AIX support

From 15d0cf54ee49a88c566cb439396b870d5e6c392c Mon Sep 17 00:00:00 2001
From: Sriram RK <sriram.rk@in.ibm.com>
Date: Mon, 20 May 2024 01:38:59 -0500
Subject: [PATCH] AIX support, revert the changes from 0b16bb8776bb8.

---
 Makefile                                      |   2 -
 config/c-compiler.m4                          |   2 +-
 configure                                     | 329 ++++++++++++++++--
 configure.ac                                  |  55 +--
 doc/src/sgml/dfunc.sgml                       |  19 +
 doc/src/sgml/installation.sgml                | 119 ++++++-
 doc/src/sgml/runtime.sgml                     |  23 ++
 meson.build                                   |  57 +--
 src/Makefile.shlib                            |  29 ++
 src/backend/Makefile                          |  20 ++
 src/backend/meson.build                       |  15 +
 src/backend/port/aix/mkldexport.sh            |  61 ++++
 src/backend/storage/buffer/bufmgr.c           |   2 +-
 src/backend/utils/error/elog.c                |   2 +
 src/backend/utils/misc/ps_status.c            |   4 +-
 src/bin/pg_basebackup/t/010_pg_basebackup.pl  |   3 +-
 src/bin/pg_verifybackup/t/008_untar.pl        |   3 +-
 src/bin/pg_verifybackup/t/010_client_untar.pl |   3 +-
 src/include/c.h                               |  18 +-
 src/include/port/aix.h                        |  14 +
 src/include/port/atomics.h                    |   6 +-
 src/include/storage/s_lock.h                  |  31 +-
 src/interfaces/libpq/Makefile                 |   2 +-
 src/interfaces/libpq/meson.build              |   5 +-
 src/makefiles/Makefile.aix                    |  39 +++
 src/port/README                               |   2 +-
 src/port/strerror.c                           |   2 +
 src/template/aix                              |  25 ++
 src/test/regress/Makefile                     |   5 +
 src/test/regress/expected/sanity_check.out    |  29 ++
 src/test/regress/expected/test_setup.out      |   4 +
 src/test/regress/regress.c                    |  40 +++
 src/test/regress/sql/sanity_check.sql         |  26 ++
 src/test/regress/sql/test_setup.sql           |   5 +
 src/tools/gen_export.pl                       |  11 +-
 src/tools/pginclude/headerscheck              |   1 +
 36 files changed, 908 insertions(+), 105 deletions(-)
 create mode 100755 src/backend/port/aix/mkldexport.sh
 create mode 100644 src/include/port/aix.h
 create mode 100644 src/makefiles/Makefile.aix
 create mode 100644 src/template/aix

diff --git a/Makefile b/Makefile
index 8a2ec9396b..9bc1a4ec17 100644
--- a/Makefile
+++ b/Makefile
@@ -13,8 +13,6 @@
 
 # AIX make defaults to building *every* target of the first rule.  Start with
 # a single-target, empty rule to make the other targets non-default.
-# (We don't support AIX anymore, but if someone tries to build on AIX anyway,
-# at least they'll get the instructions to run 'configure' first.)
 all:
 
 all check install installdirs installcheck installcheck-parallel uninstall clean distclean maintainer-clean dist distcheck world check-world install-world installcheck-world:
diff --git a/config/c-compiler.m4 b/config/c-compiler.m4
index 10f8c7bd0a..ad99b91032 100644
--- a/config/c-compiler.m4
+++ b/config/c-compiler.m4
@@ -137,7 +137,7 @@ if test x"$pgac_cv__128bit_int" = xyes ; then
   AC_CACHE_CHECK([for __int128 alignment bug], [pgac_cv__128bit_int_bug],
   [AC_RUN_IFELSE([AC_LANG_PROGRAM([
 /* This must match the corresponding code in c.h: */
-#if defined(__GNUC__) || defined(__SUNPRO_C)
+#if defined(__GNUC__) || defined(__SUNPRO_C) || defined(__IBMC__)
 #define pg_attribute_aligned(a) __attribute__((aligned(a)))
 #elif defined(_MSC_VER)
 #define pg_attribute_aligned(a) __declspec(align(a))
diff --git a/configure b/configure
index 89644f2249..8ca7ec5cfe 100755
--- a/configure
+++ b/configure
@@ -2988,6 +2988,7 @@ else
 # --with-template not given
 
 case $host_os in
+     aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -3894,8 +3895,10 @@ _ACEOF
 
 # If you don't specify a list of compilers to test, the AC_PROG_CC and
 # AC_PROG_CXX macros test for a long list of unsupported compilers.
-pgac_cc_list="gcc cc"
-pgac_cxx_list="g++ c++"
+case $template in
+  aix) pgac_cc_list="gcc xlc"; pgac_cxx_list="g++ xlC";;
+    *) pgac_cc_list="gcc cc"; pgac_cxx_list="g++ c++";;
+esac
 
 ac_ext=c
 ac_cpp='$CPP $CPPFLAGS'
@@ -6849,6 +6852,190 @@ if test x"$pgac_cv_prog_CXX_cxxflags__fno_strict_aliasing" = x"yes"; then
 fi
 
 
+elif test "$PORTNAME" = "aix"; then
+  # AIX's xlc has to have strict aliasing turned off too
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CC} supports -qnoansialias, for CFLAGS" >&5
+$as_echo_n "checking whether ${CC} supports -qnoansialias, for CFLAGS... " >&6; }
+if ${pgac_cv_prog_CC_cflags__qnoansialias+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  pgac_save_CFLAGS=$CFLAGS
+pgac_save_CC=$CC
+CC=${CC}
+CFLAGS="${CFLAGS} -qnoansialias"
+ac_save_c_werror_flag=$ac_c_werror_flag
+ac_c_werror_flag=yes
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  pgac_cv_prog_CC_cflags__qnoansialias=yes
+else
+  pgac_cv_prog_CC_cflags__qnoansialias=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+ac_c_werror_flag=$ac_save_c_werror_flag
+CFLAGS="$pgac_save_CFLAGS"
+CC="$pgac_save_CC"
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_CC_cflags__qnoansialias" >&5
+$as_echo "$pgac_cv_prog_CC_cflags__qnoansialias" >&6; }
+if test x"$pgac_cv_prog_CC_cflags__qnoansialias" = x"yes"; then
+  CFLAGS="${CFLAGS} -qnoansialias"
+fi
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CXX} supports -qnoansialias, for CXXFLAGS" >&5
+$as_echo_n "checking whether ${CXX} supports -qnoansialias, for CXXFLAGS... " >&6; }
+if ${pgac_cv_prog_CXX_cxxflags__qnoansialias+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  pgac_save_CXXFLAGS=$CXXFLAGS
+pgac_save_CXX=$CXX
+CXX=${CXX}
+CXXFLAGS="${CXXFLAGS} -qnoansialias"
+ac_save_cxx_werror_flag=$ac_cxx_werror_flag
+ac_cxx_werror_flag=yes
+ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+  pgac_cv_prog_CXX_cxxflags__qnoansialias=yes
+else
+  pgac_cv_prog_CXX_cxxflags__qnoansialias=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+ac_cxx_werror_flag=$ac_save_cxx_werror_flag
+CXXFLAGS="$pgac_save_CXXFLAGS"
+CXX="$pgac_save_CXX"
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_CXX_cxxflags__qnoansialias" >&5
+$as_echo "$pgac_cv_prog_CXX_cxxflags__qnoansialias" >&6; }
+if test x"$pgac_cv_prog_CXX_cxxflags__qnoansialias" = x"yes"; then
+  CXXFLAGS="${CXXFLAGS} -qnoansialias"
+fi
+
+
+
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CC} supports -qlonglong, for CFLAGS" >&5
+$as_echo_n "checking whether ${CC} supports -qlonglong, for CFLAGS... " >&6; }
+if ${pgac_cv_prog_CC_cflags__qlonglong+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  pgac_save_CFLAGS=$CFLAGS
+pgac_save_CC=$CC
+CC=${CC}
+CFLAGS="${CFLAGS} -qlonglong"
+ac_save_c_werror_flag=$ac_c_werror_flag
+ac_c_werror_flag=yes
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  pgac_cv_prog_CC_cflags__qlonglong=yes
+else
+  pgac_cv_prog_CC_cflags__qlonglong=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+ac_c_werror_flag=$ac_save_c_werror_flag
+CFLAGS="$pgac_save_CFLAGS"
+CC="$pgac_save_CC"
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_CC_cflags__qlonglong" >&5
+$as_echo "$pgac_cv_prog_CC_cflags__qlonglong" >&6; }
+if test x"$pgac_cv_prog_CC_cflags__qlonglong" = x"yes"; then
+  CFLAGS="${CFLAGS} -qlonglong"
+fi
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CXX} supports -qlonglong, for CXXFLAGS" >&5
+$as_echo_n "checking whether ${CXX} supports -qlonglong, for CXXFLAGS... " >&6; }
+if ${pgac_cv_prog_CXX_cxxflags__qlonglong+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  pgac_save_CXXFLAGS=$CXXFLAGS
+pgac_save_CXX=$CXX
+CXX=${CXX}
+CXXFLAGS="${CXXFLAGS} -qlonglong"
+ac_save_cxx_werror_flag=$ac_cxx_werror_flag
+ac_cxx_werror_flag=yes
+ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+  pgac_cv_prog_CXX_cxxflags__qlonglong=yes
+else
+  pgac_cv_prog_CXX_cxxflags__qlonglong=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+ac_cxx_werror_flag=$ac_save_cxx_werror_flag
+CXXFLAGS="$pgac_save_CXXFLAGS"
+CXX="$pgac_save_CXX"
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_CXX_cxxflags__qlonglong" >&5
+$as_echo "$pgac_cv_prog_CXX_cxxflags__qlonglong" >&6; }
+if test x"$pgac_cv_prog_CXX_cxxflags__qlonglong" = x"yes"; then
+  CXXFLAGS="${CXXFLAGS} -qlonglong"
+fi
+
+
 fi
 
 # If the compiler knows how to hide symbols, add the switch needed for that to
@@ -7003,6 +7190,103 @@ if test x"$pgac_cv_prog_CXX_cxxflags__fvisibility_inlines_hidden" = x"yes"; then
 fi
 
   have_visibility_attribute=$pgac_cv_prog_CC_cflags__fvisibility_hidden
+elif test "$PORTNAME" = "aix"; then
+  # Note that xlc accepts -fvisibility=hidden as a file.
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CC} supports -qvisibility=hidden, for CFLAGS_SL_MODULE" >&5
+$as_echo_n "checking whether ${CC} supports -qvisibility=hidden, for CFLAGS_SL_MODULE... " >&6; }
+if ${pgac_cv_prog_CC_cflags__qvisibility_hidden+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  pgac_save_CFLAGS=$CFLAGS
+pgac_save_CC=$CC
+CC=${CC}
+CFLAGS="${CFLAGS_SL_MODULE} -qvisibility=hidden"
+ac_save_c_werror_flag=$ac_c_werror_flag
+ac_c_werror_flag=yes
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  pgac_cv_prog_CC_cflags__qvisibility_hidden=yes
+else
+  pgac_cv_prog_CC_cflags__qvisibility_hidden=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+ac_c_werror_flag=$ac_save_c_werror_flag
+CFLAGS="$pgac_save_CFLAGS"
+CC="$pgac_save_CC"
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_CC_cflags__qvisibility_hidden" >&5
+$as_echo "$pgac_cv_prog_CC_cflags__qvisibility_hidden" >&6; }
+if test x"$pgac_cv_prog_CC_cflags__qvisibility_hidden" = x"yes"; then
+  CFLAGS_SL_MODULE="${CFLAGS_SL_MODULE} -qvisibility=hidden"
+fi
+
+
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether ${CXX} supports -qvisibility=hidden, for CXXFLAGS_SL_MODULE" >&5
+$as_echo_n "checking whether ${CXX} supports -qvisibility=hidden, for CXXFLAGS_SL_MODULE... " >&6; }
+if ${pgac_cv_prog_CXX_cxxflags__qvisibility_hidden+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  pgac_save_CXXFLAGS=$CXXFLAGS
+pgac_save_CXX=$CXX
+CXX=${CXX}
+CXXFLAGS="${CXXFLAGS_SL_MODULE} -qvisibility=hidden"
+ac_save_cxx_werror_flag=$ac_cxx_werror_flag
+ac_cxx_werror_flag=yes
+ac_ext=cpp
+ac_cpp='$CXXCPP $CPPFLAGS'
+ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
+
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+  pgac_cv_prog_CXX_cxxflags__qvisibility_hidden=yes
+else
+  pgac_cv_prog_CXX_cxxflags__qvisibility_hidden=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+ac_ext=c
+ac_cpp='$CPP $CPPFLAGS'
+ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'
+ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5'
+ac_compiler_gnu=$ac_cv_c_compiler_gnu
+
+ac_cxx_werror_flag=$ac_save_cxx_werror_flag
+CXXFLAGS="$pgac_save_CXXFLAGS"
+CXX="$pgac_save_CXX"
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_prog_CXX_cxxflags__qvisibility_hidden" >&5
+$as_echo "$pgac_cv_prog_CXX_cxxflags__qvisibility_hidden" >&6; }
+if test x"$pgac_cv_prog_CXX_cxxflags__qvisibility_hidden" = x"yes"; then
+  CXXFLAGS_SL_MODULE="${CXXFLAGS_SL_MODULE} -qvisibility=hidden"
+fi
+
+  have_visibility_attribute=$pgac_cv_prog_CC_cflags__qvisibility_hidden
+  # Old xlc versions (<13.1) don't have support for -qvisibility. Use expfull to force
+  # all extension module symbols to be exported.
+  if test "$pgac_cv_prog_CC_cflags__qvisibility_hidden" != "yes"; then
+    CFLAGS_SL_MODULE="$CFLAGS_SL_MODULE -Wl,-b,expfull"
+  fi
 fi
 
 if test "$have_visibility_attribute" = "yes"; then
@@ -12860,7 +13144,8 @@ fi
 
 fi
 
-# Note: We can test for libldap_r only after we know PTHREAD_LIBS
+# Note: We can test for libldap_r only after we know PTHREAD_LIBS;
+# also, on AIX, we may need to have openssl in LIBS for this step.
 if test "$with_ldap" = yes ; then
   _LIBS="$LIBS"
   if test "$PORTNAME" != "win32"; then
@@ -14718,6 +15003,10 @@ fi
 # spelling it understands, because it conflicts with
 # __declspec(restrict). Therefore we define pg_restrict to the
 # appropriate definition, which presumably won't conflict.
+#
+# Allow platforms with buggy compilers to force restrict to not be
+# used by setting $FORCE_DISABLE_RESTRICT=yes in the relevant
+# template.
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for C/C++ restrict keyword" >&5
 $as_echo_n "checking for C/C++ restrict keyword... " >&6; }
 if ${ac_cv_c_restrict+:} false; then :
@@ -14764,7 +15053,7 @@ _ACEOF
  ;;
  esac
 
-if test "$ac_cv_c_restrict" = "no"; then
+if test "$ac_cv_c_restrict" = "no" -o "x$FORCE_DISABLE_RESTRICT" = "xyes"; then
   pg_restrict=""
 else
   pg_restrict="$ac_cv_c_restrict"
@@ -16951,28 +17240,18 @@ _ACEOF
 
 
 # Compute maximum alignment of any basic type.
-#
-# We require 'double' to have the strictest alignment among the basic types,
-# because otherwise the C ABI might impose 8-byte alignment on some of the
-# other C types that correspond to TYPALIGN_DOUBLE SQL types.  That could
-# cause a mismatch between the tuple layout and the C struct layout of a
-# catalog tuple.  We used to carefully order catalog columns such that any
-# fixed-width, attalign=4 columns were at offsets divisible by 8 regardless
-# of MAXIMUM_ALIGNOF to avoid that, but we no longer support any platforms
-# where TYPALIGN_DOUBLE != MAXIMUM_ALIGNOF.
-#
-# We assume without checking that long's alignment is at least as strong as
-# char, short, or int.  Note that we intentionally do not consider any types
-# wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
-# much of a penalty for disk and memory space.
-
-MAX_ALIGNOF=$ac_cv_alignof_double
+# We assume long's alignment is at least as strong as char, short, or int;
+# but we must check long long (if it is being used for int64) and double.
+# Note that we intentionally do not consider any types wider than 64 bits,
+# as allowing MAXIMUM_ALIGNOF to exceed 8 would be too much of a penalty
+# for disk and memory space.
 
-if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
+MAX_ALIGNOF=$ac_cv_alignof_long
+if test $MAX_ALIGNOF -lt $ac_cv_alignof_double ; then
+  MAX_ALIGNOF=$ac_cv_alignof_double
 fi
-if test x"$HAVE_LONG_LONG_INT_64" = xyes && test $ac_cv_alignof_long_long_int -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'long long int' is greater than the alignment of 'double'" "$LINENO" 5
+if test x"$HAVE_LONG_LONG_INT_64" = xyes && test $MAX_ALIGNOF -lt $ac_cv_alignof_long_long_int ; then
+  MAX_ALIGNOF="$ac_cv_alignof_long_long_int"
 fi
 
 cat >>confdefs.h <<_ACEOF
@@ -17090,7 +17369,7 @@ else
 /* end confdefs.h.  */
 
 /* This must match the corresponding code in c.h: */
-#if defined(__GNUC__) || defined(__SUNPRO_C)
+#if defined(__GNUC__) || defined(__SUNPRO_C) || defined(__IBMC__)
 #define pg_attribute_aligned(a) __attribute__((aligned(a)))
 #elif defined(_MSC_VER)
 #define pg_attribute_aligned(a) __declspec(align(a))
diff --git a/configure.ac b/configure.ac
index c7322e292c..b2e19cf822 100644
--- a/configure.ac
+++ b/configure.ac
@@ -62,6 +62,7 @@ PGAC_ARG_REQ(with, template, [NAME], [override operating system template],
 # --with-template not given
 
 case $host_os in
+     aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -368,10 +369,10 @@ AC_DEFINE_UNQUOTED([XLOG_BLCKSZ], ${XLOG_BLCKSZ}, [
 # C compiler
 #
 
-# If you don't specify a list of compilers to test, the AC_PROG_CC and
-# AC_PROG_CXX macros test for a long list of unsupported compilers.
-pgac_cc_list="gcc cc"
-pgac_cxx_list="g++ c++"
+case $template in
+  aix) pgac_cc_list="gcc xlc"; pgac_cxx_list="g++ xlC";;
+    *) pgac_cc_list="gcc cc"; pgac_cxx_list="g++ c++";;
+esac
 
 AC_PROG_CC([$pgac_cc_list])
 AC_PROG_CC_C99()
@@ -588,6 +589,12 @@ elif test "$ICC" = yes; then
   # Make sure strict aliasing is off (though this is said to be the default)
   PGAC_PROG_CC_CFLAGS_OPT([-fno-strict-aliasing])
   PGAC_PROG_CXX_CFLAGS_OPT([-fno-strict-aliasing])
+elif test "$PORTNAME" = "aix"; then
+  # AIX's xlc has to have strict aliasing turned off too
+  PGAC_PROG_CC_CFLAGS_OPT([-qnoansialias])
+  PGAC_PROG_CXX_CFLAGS_OPT([-qnoansialias])
+  PGAC_PROG_CC_CFLAGS_OPT([-qlonglong])
+  PGAC_PROG_CXX_CFLAGS_OPT([-qlonglong])
 fi
 
 # If the compiler knows how to hide symbols, add the switch needed for that to
@@ -606,6 +613,16 @@ if test "$GCC" = yes -o "$SUN_STUDIO_CC" = yes ; then
   PGAC_PROG_VARCXX_VARFLAGS_OPT(CXX, CXXFLAGS_SL_MODULE, [-fvisibility=hidden])
   PGAC_PROG_VARCXX_VARFLAGS_OPT(CXX, CXXFLAGS_SL_MODULE, [-fvisibility-inlines-hidden])
   have_visibility_attribute=$pgac_cv_prog_CC_cflags__fvisibility_hidden
+elif test "$PORTNAME" = "aix"; then
+  # Note that xlc accepts -fvisibility=hidden as a file.
+  PGAC_PROG_CC_VAR_OPT(CFLAGS_SL_MODULE, [-qvisibility=hidden])
+  PGAC_PROG_VARCXX_VARFLAGS_OPT(CXX, CXXFLAGS_SL_MODULE, [-qvisibility=hidden])
+  have_visibility_attribute=$pgac_cv_prog_CC_cflags__qvisibility_hidden
+  # Old xlc versions (<13.1) don't have support for -qvisibility. Use expfull to force
+  # all extension module symbols to be exported.
+  if test "$pgac_cv_prog_CC_cflags__qvisibility_hidden" != "yes"; then
+    CFLAGS_SL_MODULE="$CFLAGS_SL_MODULE -Wl,-b,expfull"
+  fi
 fi
 
 if test "$have_visibility_attribute" = "yes"; then
@@ -1385,7 +1402,8 @@ if test "$with_zstd" = yes ; then
   AC_CHECK_LIB(zstd, ZSTD_compress, [], [AC_MSG_ERROR([library 'zstd' is required for ZSTD support])])
 fi
 
-# Note: We can test for libldap_r only after we know PTHREAD_LIBS
+# Note: We can test for libldap_r only after we know PTHREAD_LIBS;
+# also, on AIX, we may need to have openssl in LIBS for this step.
 if test "$with_ldap" = yes ; then
   _LIBS="$LIBS"
   if test "$PORTNAME" != "win32"; then
@@ -1643,8 +1661,12 @@ PGAC_TYPE_LOCALE_T
 # spelling it understands, because it conflicts with
 # __declspec(restrict). Therefore we define pg_restrict to the
 # appropriate definition, which presumably won't conflict.
+#
+# Allow platforms with buggy compilers to force restrict to not be
+# used by setting $FORCE_DISABLE_RESTRICT=yes in the relevant
+# template.
 AC_C_RESTRICT
-if test "$ac_cv_c_restrict" = "no"; then
+if test "$ac_cv_c_restrict" = "no" -o "x$FORCE_DISABLE_RESTRICT" = "xyes"; then
   pg_restrict=""
 else
   pg_restrict="$ac_cv_c_restrict"
@@ -1996,22 +2018,11 @@ fi
 AC_CHECK_ALIGNOF(double)
 
 # Compute maximum alignment of any basic type.
-#
-# We require 'double' to have the strictest alignment among the basic types,
-# because otherwise the C ABI might impose 8-byte alignment on some of the
-# other C types that correspond to TYPALIGN_DOUBLE SQL types.  That could
-# cause a mismatch between the tuple layout and the C struct layout of a
-# catalog tuple.  We used to carefully order catalog columns such that any
-# fixed-width, attalign=4 columns were at offsets divisible by 8 regardless
-# of MAXIMUM_ALIGNOF to avoid that, but we no longer support any platforms
-# where TYPALIGN_DOUBLE != MAXIMUM_ALIGNOF.
-#
-# We assume without checking that long's alignment is at least as strong as
-# char, short, or int.  Note that we intentionally do not consider any types
-# wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
-# much of a penalty for disk and memory space.
-
-MAX_ALIGNOF=$ac_cv_alignof_double
+# We assume long's alignment is at least as strong as char, short, or int;
+# but we must check long long (if it is being used for int64) and double.
+# Note that we intentionally do not consider any types wider than 64 bits,
+# as allowing MAXIMUM_ALIGNOF to exceed 8 would be too much of a penalty
+# for disk and memory space.
 
 if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
   AC_MSG_ERROR([alignment of 'long' is greater than the alignment of 'double'])
diff --git a/doc/src/sgml/dfunc.sgml b/doc/src/sgml/dfunc.sgml
index b94aefcd0c..554f9fac4c 100644
--- a/doc/src/sgml/dfunc.sgml
+++ b/doc/src/sgml/dfunc.sgml
@@ -202,4 +202,23 @@ gcc -G -o foo.so foo.o
   server expects to find the shared library files.
  </para>
 
+<!--
+Under AIX, object files are compiled normally but building the shared
+library requires a couple of steps.  First, create the object file:
+.nf
+cc <other flags> -c foo.c
+.fi
+You must then create a symbol \*(lqexports\*(rq file for the object
+file:
+.nf
+mkldexport foo.o `pwd` &gt; foo.exp
+.fi
+Finally, you can create the shared library:
+.nf
+ld <other flags> -H512 -T512 -o foo.so -e _nostart \e
+   -bI:.../lib/postgres.exp -bE:foo.exp foo.o \e
+   -lm -lc 2>/dev/null
+.fi
+  -->
+
 </sect2>
diff --git a/doc/src/sgml/installation.sgml b/doc/src/sgml/installation.sgml
index 1b32d5ca62..6b27a1250b 100644
--- a/doc/src/sgml/installation.sgml
+++ b/doc/src/sgml/installation.sgml
@@ -3401,7 +3401,7 @@ export MANPATH
   <para>
    <productname>PostgreSQL</productname> can be expected to work on current
    versions of these operating systems: Linux, Windows,
-   FreeBSD, OpenBSD, NetBSD, DragonFlyBSD, macOS, Solaris, and illumos.
+   FreeBSD, OpenBSD, NetBSD, DragonFlyBSD, macOS, AIX, Solaris, and illumos.
    Other Unix-like systems may also work but are not currently
    being tested.  In most cases, all CPU architectures supported by
    a given operating system will work.  Look in
@@ -3445,6 +3445,123 @@ export MANPATH
    installation issues.
   </para>
 
+  <sect2 id="installation-notes-aix">
+   <title>AIX</title>
+
+   <indexterm zone="installation-notes-aix">
+    <primary>AIX</primary>
+    <secondary>installation on</secondary>
+   </indexterm>
+
+   <para>
+    You can use GCC or the native IBM compiler <command>xlc</command>
+    to build <productname>PostgreSQL</productname>
+    on <productname>AIX</productname>.
+   </para>
+
+   <para>
+    <productname>AIX</productname> versions before 7.1 are no longer
+    tested nor supported by the <productname>PostgreSQL</productname>
+    community.
+   </para>
+
+   <sect3 id="installation-notes-aix-mem-management">
+    <title>Memory Management</title>
+    <!-- https://archives.postgresql.org/message-id/603bgqmpl9.fsf@dba2.int.libertyrms.com -->
+
+    <para>
+     AIX can be somewhat peculiar with regards to the way it does
+     memory management.  You can have a server with many multiples of
+     gigabytes of RAM free, but still get out of memory or address
+     space errors when running applications.  One example
+     is loading of extensions failing with unusual errors.
+     For example, running as the owner of the PostgreSQL installation:
+<screen>
+=# CREATE EXTENSION plperl;
+ERROR:  could not load library "/opt/dbs/pgsql/lib/plperl.so": A memory address is not in the address space for the process.
+</screen>
+    Running as a non-owner in the group possessing the PostgreSQL
+    installation:
+<screen>
+=# CREATE EXTENSION plperl;
+ERROR:  could not load library "/opt/dbs/pgsql/lib/plperl.so": Bad address
+</screen>
+     Another example is out of memory errors in the PostgreSQL server
+     logs, with every memory allocation near or greater than 256 MB
+     failing.
+    </para>
+
+    <para>
+     The overall cause of all these problems is the default bittedness
+     and memory model used by the server process.  By default, all
+     binaries built on AIX are 32-bit.  This does not depend upon
+     hardware type or kernel in use.  These 32-bit processes are
+     limited to 4 GB of memory laid out in 256 MB segments using one
+     of a few models.  The default allows for less than 256 MB in the
+     heap as it shares a single segment with the stack.
+    </para>
+
+    <para>
+     In the case of the <literal>plperl</literal> example, above,
+     check your umask and the permissions of the binaries in your
+     PostgreSQL installation.  The binaries involved in that example
+     were 32-bit and installed as mode 750 instead of 755.  Due to the
+     permissions being set in this fashion, only the owner or a member
+     of the possessing group can load the library.  Since it isn't
+     world-readable, the loader places the object into the process'
+     heap instead of the shared library segments where it would
+     otherwise be placed.
+    </para>
+
+    <para>
+     The <quote>ideal</quote> solution for this is to use a 64-bit
+     build of PostgreSQL, but that is not always practical, because
+     systems with 32-bit processors can build, but not run, 64-bit
+     binaries.
+    </para>
+
+    <para>
+     If a 32-bit binary is desired, set <symbol>LDR_CNTRL</symbol> to
+     <literal>MAXDATA=0x<replaceable>n</replaceable>0000000</literal>,
+     where 1 &lt;= n &lt;= 8, before starting the PostgreSQL server,
+     and try different values and <filename>postgresql.conf</filename>
+     settings to find a configuration that works satisfactorily.  This
+     use of <symbol>LDR_CNTRL</symbol> tells AIX that you want the
+     server to have <symbol>MAXDATA</symbol> bytes set aside for the
+     heap, allocated in 256 MB segments.  When you find a workable
+     configuration,
+     <command>ldedit</command> can be used to modify the binaries so
+     that they default to using the desired heap size.  PostgreSQL can
+     also be rebuilt, passing <literal>configure
+     LDFLAGS="-Wl,-bmaxdata:0x<replaceable>n</replaceable>0000000"</literal>
+     to achieve the same effect.
+    </para>
+
+    <para>
+     For a 64-bit build, set <envar>OBJECT_MODE</envar> to 64 and
+     pass <literal>CC="gcc -maix64"</literal>
+     and <literal>LDFLAGS="-Wl,-bbigtoc"</literal>
+     to <command>configure</command>.  (Options for
+    <command>xlc</command> might differ.)  If you omit the export of
+    <envar>OBJECT_MODE</envar>, your build may fail with linker errors.  When
+    <envar>OBJECT_MODE</envar> is set, it tells AIX's build utilities
+    such as <command>ar</command>, <command>as</command>, and <command>ld</command> what
+    type of objects to default to handling.
+    </para>
+
+    <para>
+     By default, overcommit of paging space can happen.  While we have
+     not seen this occur, AIX will kill processes when it runs out of
+     memory and the overcommit is accessed.  The closest to this that
+     we have seen is fork failing because the system decided that
+     there was not enough memory for another process.  Like many other
+     parts of AIX, the paging space allocation method and
+     out-of-memory kill is configurable on a system- or process-wide
+     basis if this becomes a problem.
+    </para>
+   </sect3>
+  </sect2>
+
   <sect2 id="installation-notes-cygwin">
    <title>Cygwin</title>
 
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index 6047b8171d..64753d9c01 100644
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -891,6 +891,29 @@ psql: error: connection to server on socket "/tmp/.s.PGSQL.5432" failed: No such
 
 
     <variablelist>
+     <varlistentry>
+      <term><systemitem class="osname">AIX</systemitem>
+      <indexterm><primary>AIX</primary><secondary>IPC configuration</secondary></indexterm>
+      </term>
+      <listitem>
+       <para>
+        It should not be necessary to do
+        any special configuration for such parameters as
+        <varname>SHMMAX</varname>, as it appears this is configured to
+        allow all memory to be used as shared memory.  That is the
+        sort of configuration commonly used for other databases such
+        as <application>DB/2</application>.</para>
+
+       <para> It might, however, be necessary to modify the global
+       <command>ulimit</command> information in
+       <filename>/etc/security/limits</filename>, as the default hard
+       limits for file sizes (<varname>fsize</varname>) and numbers of
+       files (<varname>nofiles</varname>) might be too low.
+       </para>
+      </listitem>
+     </varlistentry>
+
+
      <varlistentry>
       <term><systemitem class="osname">FreeBSD</systemitem>
       <indexterm><primary>FreeBSD</primary><secondary>IPC configuration</secondary></indexterm>
diff --git a/meson.build b/meson.build
index 1c0579d5a6..f1ac154cdc 100644
--- a/meson.build
+++ b/meson.build
@@ -196,7 +196,26 @@ endif
 # that purpose.
 portname = host_system
 
-if host_system == 'cygwin'
+if host_system == 'aix'
+  library_path_var = 'LIBPATH'
+
+  export_file_format = 'aix'
+  export_fmt = '-Wl,-bE:@0@'
+  mod_link_args_fmt = ['-Wl,-bI:@0@']
+  mod_link_with_dir = 'libdir'
+  mod_link_with_name = '@0@.imp'
+
+  # M:SRE sets a flag indicating that an object is a shared library. Seems to
+  # work in some circumstances without, but required in others.
+  ldflags_sl += '-Wl,-bM:SRE'
+  ldflags_be += '-Wl,-brtllib'
+
+  # Native memset() is faster, tested on:
+  # - AIX 5.1 and 5.2, XLC 6.0 (IBM's cc)
+  # - AIX 5.3 ML3, gcc 4.0.1
+  memset_loop_limit = 0
+
+elif host_system == 'cygwin'
   sema_kind = 'unnamed_posix'
   cppflags += '-D_GNU_SOURCE'
   dlsuffix = '.dll'
@@ -1490,11 +1509,11 @@ sizeof_long = cc.sizeof('long', args: test_c_args)
 cdata.set('SIZEOF_LONG', sizeof_long)
 if sizeof_long == 8
   cdata.set('HAVE_LONG_INT_64', 1)
-  pg_int64_type = 'long int'
+  cdata.set('PG_INT64_TYPE', 'long int')
   cdata.set_quoted('INT64_MODIFIER', 'l')
 elif sizeof_long == 4 and cc.sizeof('long long', args: test_c_args) == 8
   cdata.set('HAVE_LONG_LONG_INT_64', 1)
-  pg_int64_type = 'long long int'
+  cdata.set('PG_INT64_TYPE', 'long long int')
   cdata.set_quoted('INT64_MODIFIER', 'll')
 else
   error('do not know how to get a 64bit int')
@@ -1508,31 +1527,15 @@ endif
 # Determine memory alignment requirements for the basic C data types.
 
 alignof_types = ['short', 'int', 'long', 'double']
+maxalign = 0
 foreach t : alignof_types
   align = cc.alignment(t, args: test_c_args)
+  if maxalign < align
+    maxalign = align
+  endif
   cdata.set('ALIGNOF_@0@'.format(t.to_upper()), align)
 endforeach
-
-# Compute maximum alignment of any basic type.
-#
-# We require 'double' to have the strictest alignment among the basic types,
-# because otherwise the C ABI might impose 8-byte alignment on some of the
-# other C types that correspond to TYPALIGN_DOUBLE SQL types.  That could
-# cause a mismatch between the tuple layout and the C struct layout of a
-# catalog tuple.  We used to carefully order catalog columns such that any
-# fixed-width, attalign=4 columns were at offsets divisible by 8 regardless
-# of MAXIMUM_ALIGNOF to avoid that, but we no longer support any platforms
-# where TYPALIGN_DOUBLE != MAXIMUM_ALIGNOF.
-#
-# We assume without checking that int64's alignment is at least as strong
-# as long, char, short, or int.  Note that we intentionally do not consider
-# any types wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8
-# would be too much of a penalty for disk and memory space.
-alignof_double = cdata.get('ALIGNOF_DOUBLE')
-if cc.alignment(pg_int64_type, args: test_c_args) > alignof_double
-  error('alignment of int64 is greater than the alignment of double')
-endif
-cdata.set('MAXIMUM_ALIGNOF', alignof_double)
+cdata.set('MAXIMUM_ALIGNOF', maxalign)
 
 cdata.set('SIZEOF_VOID_P', cc.sizeof('void *', args: test_c_args))
 cdata.set('SIZEOF_SIZE_T', cc.sizeof('size_t', args: test_c_args))
@@ -1581,7 +1584,7 @@ if cc.links('''
   if not meson.is_cross_build()
     r = cc.run('''
     /* This must match the corresponding code in c.h: */
-    #if defined(__GNUC__) || defined(__SUNPRO_C)
+    #if defined(__GNUC__) || defined(__SUNPRO_C) || defined(__IBMC__)
     #define pg_attribute_aligned(a) __attribute__((aligned(a)))
     #elif defined(_MSC_VER)
     #define pg_attribute_aligned(a) __declspec(align(a))
@@ -2476,6 +2479,10 @@ endif
 # conflict.
 #
 # We assume C99 support, so we don't need to make this conditional.
+#
+# XXX: Historically we allowed platforms to disable restrict in template
+# files, but that was only added for AIX when building with XLC, which we
+# don't support yet.
 cdata.set('pg_restrict', '__restrict')
 
 
diff --git a/src/Makefile.shlib b/src/Makefile.shlib
index fa81f6ffdd..8ca51ca03f 100644
--- a/src/Makefile.shlib
+++ b/src/Makefile.shlib
@@ -106,6 +106,20 @@ ifdef SO_MAJOR_VERSION
 override CPPFLAGS += -DSO_MAJOR_VERSION=$(SO_MAJOR_VERSION)
 endif
 
+ifeq ($(PORTNAME), aix)
+  LINK.shared		= $(COMPILER)
+  ifdef SO_MAJOR_VERSION
+    shlib		= lib$(NAME)$(DLSUFFIX).$(SO_MAJOR_VERSION)
+  endif
+  haslibarule   = yes
+  # $(exports_file) is also usable as an import file
+  exports_file		= lib$(NAME).exp
+  BUILD.exports		= ( echo '\#! $(shlib)'; $(AWK) '/^[^\#]/ {printf "%s\n",$$1}' $< ) > $@
+  ifneq (,$(SHLIB_EXPORTS))
+    LINK.shared		+= -Wl,-bE:$(exports_file)
+  endif
+endif
+
 ifeq ($(PORTNAME), darwin)
   ifdef soname
     # linkable library
@@ -254,6 +268,14 @@ $(stlib): $(OBJS) | $(SHLIB_PREREQS)
 	touch $@
 endif #haslibarule
 
+# AIX wraps shared libraries inside a static library, can be used both
+# for static and shared linking
+ifeq ($(PORTNAME), aix)
+$(stlib): $(shlib)
+	rm -f $(stlib)
+	$(AR) $(AROPT) $(stlib) $(shlib)
+endif # aix
+
 ifeq (,$(filter cygwin win32,$(PORTNAME)))
 
 # Normal case
@@ -267,8 +289,11 @@ ifneq ($(shlib), $(shlib_major))
 endif
 # Make sure we have a link to a name without any version numbers
 ifneq ($(shlib), $(shlib_bare))
+# except on AIX, where that's not a thing
+ifneq ($(PORTNAME), aix)
 	rm -f $(shlib_bare)
 	$(LN_S) $(shlib) $(shlib_bare)
+endif # aix
 endif # shlib_bare
 endif # shlib_major
 
@@ -376,6 +401,9 @@ install-lib-static: $(stlib) installdirs-lib
 
 install-lib-shared: $(shlib) installdirs-lib
 ifdef soname
+# we don't install $(shlib) on AIX
+# (see http://archives.postgresql.org/message-id/52EF20B2E3209443BC37736D00C3C1380A6E79FE@EXADV1.host.magwien.gv.at)
+ifneq ($(PORTNAME), aix)
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(libdir)/$(shlib)'
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
@@ -391,6 +419,7 @@ ifneq ($(shlib), $(shlib_bare))
 endif
 endif # not win32
 endif # not cygwin
+endif # not aix
 ifneq (,$(findstring $(PORTNAME),win32 cygwin))
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(bindir)/$(shlib)'
 endif
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 6700aec039..954b14962f 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -62,12 +62,14 @@ all: submake-libpgport submake-catalog-headers submake-utils-headers postgres $(
 
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
+ifneq ($(PORTNAME), aix)
 
 postgres: $(OBJS)
 	$(CC) $(CFLAGS) $(call expand_subsys,$^) $(LDFLAGS) $(LIBS) -o $@
 
 endif
 endif
+endif
 
 ifeq ($(PORTNAME), cygwin)
 
@@ -94,6 +96,24 @@ libpostgres.a: postgres
 
 endif # win32
 
+ifeq ($(PORTNAME), aix)
+
+postgres: $(POSTGRES_IMP)
+	$(CC) $(CFLAGS) $(call expand_subsys,$(OBJS)) $(LDFLAGS) -Wl,-bE:$(top_builddir)/src/backend/$(POSTGRES_IMP) $(LIBS) -Wl,-brtllib -o $@
+
+# Linking to a single .o with -r is a lot faster than building a .a or passing
+# all objects to MKLDEXPORT.
+#
+# It looks alluring to use $(CC) -r instead of ld -r, but that doesn't
+# trivially work with gcc, due to gcc specific static libraries linked in with
+# -r.
+$(POSTGRES_IMP): $(OBJS)
+	ld -r -o SUBSYS.o $(call expand_subsys,$^)
+	$(MKLDEXPORT) SUBSYS.o . > $@
+	@rm -f SUBSYS.o
+
+endif # aix
+
 $(top_builddir)/src/port/libpgport_srv.a: | submake-libpgport
 
 
diff --git a/src/backend/meson.build b/src/backend/meson.build
index 436c04af08..8767aaba67 100644
--- a/src/backend/meson.build
+++ b/src/backend/meson.build
@@ -91,6 +91,21 @@ if cc.get_id() == 'msvc'
   # be restricted to b_pch=true.
   backend_link_with += postgres_lib
 
+elif host_system == 'aix'
+  # The '.' argument leads mkldexport.sh to emit "#! .", which refers to the
+  # main executable, allowing extension libraries to resolve their undefined
+  # symbols to symbols in the postgres binary.
+  postgres_imp = custom_target('postgres.imp',
+    command: [files('port/aix/mkldexport.sh'), '@INPUT@', '.'],
+    input: postgres_lib,
+    output: 'postgres.imp',
+    capture: true,
+    install: true,
+    install_dir: dir_lib,
+    build_by_default: false,
+  )
+  backend_link_args += '-Wl,-bE:@0@'.format(postgres_imp.full_path())
+  backend_link_depends += postgres_imp
 endif
 
 backend_input = []
diff --git a/src/backend/port/aix/mkldexport.sh b/src/backend/port/aix/mkldexport.sh
new file mode 100755
index 0000000000..adf3793e86
--- /dev/null
+++ b/src/backend/port/aix/mkldexport.sh
@@ -0,0 +1,61 @@
+#!/bin/sh
+#
+# mkldexport
+#	create an AIX exports file from an object file
+#
+# src/backend/port/aix/mkldexport.sh
+#
+# Usage:
+#	mkldexport objectfile [location]
+# where
+#	objectfile is the current location of the object file.
+#	location is the eventual (installed) location of the
+#		object file (if different from the current
+#		working directory).
+#
+# [This file comes from the Postgres 4.2 distribution. - ay 7/95]
+#
+# Header: /usr/local/devel/postgres/src/tools/mkldexport/RCS/mkldexport.sh,v 1.2 1994/03/13 04:59:12 aoki Exp
+#
+
+# setting this to nm -B might be better
+# ... due to changes in AIX 4.x ...
+# ... let us search in different directories - Gerhard Reithofer
+if [ -x /usr/ucb/nm ]
+then NM=/usr/ucb/nm
+elif [ -x /usr/bin/nm ]
+then NM=/usr/bin/nm
+elif [ -x /usr/ccs/bin/nm ]
+then NM=/usr/ccs/bin/nm
+elif [ -x /usr/usg/bin/nm ]
+then NM=/usr/usg/bin/nm
+else echo "Fatal error: cannot find `nm' ... please check your installation."
+     exit 1
+fi
+
+CMDNAME=`basename $0`
+if [ -z "$1" ]; then
+	echo "Usage: $CMDNAME object [location]"
+	exit 1
+fi
+OBJNAME=`basename $1`
+if [ "`basename $OBJNAME`" != "`basename $OBJNAME .o`" ]; then
+	OBJNAME=`basename $OBJNAME .o`.so
+fi
+if [ -z "$2" ]; then
+	echo '#!'
+else
+	if [ "$2" = "." ]; then
+		# for the base executable (AIX 4.2 and up)
+		echo '#! .'
+	else
+		echo '#!' $2
+	fi
+fi
+$NM -BCg $1 | \
+	egrep ' [TDB] ' | \
+	sed -e 's/.* //' | \
+	egrep -v '\$' | \
+	sed -e 's/^[.]//' | \
+	sort | \
+	uniq
diff --git a/src/backend/storage/buffer/bufmgr.c b/src/backend/storage/buffer/bufmgr.c
index 49637284f9..bade061271 100644
--- a/src/backend/storage/buffer/bufmgr.c
+++ b/src/backend/storage/buffer/bufmgr.c
@@ -788,7 +788,7 @@ ReadBuffer(Relation reln, BlockNumber blockNum)
  * If strategy is not NULL, a nondefault buffer access strategy is used.
  * See buffer/README for details.
  */
-inline Buffer
+Buffer
 ReadBufferExtended(Relation reln, ForkNumber forkNum, BlockNumber blockNum,
 				   ReadBufferMode mode, BufferAccessStrategy strategy)
 {
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index d91a85cb2d..7b51e94f4a 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -908,7 +908,9 @@ errcode_for_file_access(void)
 			/* Wrong object type or state */
 		case ENOTDIR:			/* Not a directory */
 		case EISDIR:			/* Is a directory */
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:			/* Directory not empty */
+#endif
 			edata->sqlerrcode = ERRCODE_WRONG_OBJECT_TYPE;
 			break;
 
diff --git a/src/backend/utils/misc/ps_status.c b/src/backend/utils/misc/ps_status.c
index 9da6377402..532eac31b4 100644
--- a/src/backend/utils/misc/ps_status.c
+++ b/src/backend/utils/misc/ps_status.c
@@ -50,7 +50,7 @@ bool		update_process_title = DEFAULT_UPDATE_PROCESS_TITLE;
 #define PS_USE_SETPROCTITLE_FAST
 #elif defined(HAVE_SETPROCTITLE)
 #define PS_USE_SETPROCTITLE
-#elif defined(__linux__) || defined(__sun) || defined(__darwin__)
+#elif defined(__linux__) || defined(_AIX) || defined(__sun) || defined(__darwin__)
 #define PS_USE_CLOBBER_ARGV
 #elif defined(WIN32)
 #define PS_USE_WIN32
@@ -60,7 +60,7 @@ bool		update_process_title = DEFAULT_UPDATE_PROCESS_TITLE;
 
 
 /* Different systems want the buffer padded differently */
-#if defined(__linux__) || defined(__darwin__)
+#if defined(_AIX) || defined(__linux__) || defined(__darwin__)
 #define PS_PADDING '\0'
 #else
 #define PS_PADDING ' '
diff --git a/src/bin/pg_basebackup/t/010_pg_basebackup.pl b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
index 2d4b75a6fe..ce936959c1 100644
--- a/src/bin/pg_basebackup/t/010_pg_basebackup.pl
+++ b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
@@ -401,7 +401,8 @@ SKIP:
 {
 	my $tar = $ENV{TAR};
 	# don't check for a working tar here, to accommodate various odd
-	# cases. If tar doesn't work the init_from_backup below will fail.
+	# cases such as AIX. If tar doesn't work the init_from_backup below
+	# will fail.
 	skip "no tar program available", 1
 	  if (!defined $tar || $tar eq '');
 
diff --git a/src/bin/pg_verifybackup/t/008_untar.pl b/src/bin/pg_verifybackup/t/008_untar.pl
index 7a09f3b75b..30d9f3f7f0 100644
--- a/src/bin/pg_verifybackup/t/008_untar.pl
+++ b/src/bin/pg_verifybackup/t/008_untar.pl
@@ -104,7 +104,8 @@ for my $tc (@test_configuration)
 		{
 			my $tar = $ENV{TAR};
 			# don't check for a working tar here, to accommodate various odd
-			# cases. If tar doesn't work the init_from_backup below will fail.
+			# cases such as AIX. If tar doesn't work the init_from_backup below
+			# will fail.
 			skip "no tar program available", 1
 			  if (!defined $tar || $tar eq '');
 
diff --git a/src/bin/pg_verifybackup/t/010_client_untar.pl b/src/bin/pg_verifybackup/t/010_client_untar.pl
index 8c076d46de..45010d79ac 100644
--- a/src/bin/pg_verifybackup/t/010_client_untar.pl
+++ b/src/bin/pg_verifybackup/t/010_client_untar.pl
@@ -134,7 +134,8 @@ for my $tc (@test_configuration)
 		{
 			my $tar = $ENV{TAR};
 			# don't check for a working tar here, to accommodate various odd
-			# cases. If tar doesn't work the init_from_backup below will fail.
+			# cases such as AIX. If tar doesn't work the init_from_backup below
+			# will fail.
 			skip "no tar program available", 1
 			  if (!defined $tar || $tar eq '');
 
diff --git a/src/include/c.h b/src/include/c.h
index dc1841346c..b667ac54a0 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -105,6 +105,8 @@
  * GCC: https://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html
  * Clang: https://clang.llvm.org/docs/AttributeReference.html
  * Sunpro: https://docs.oracle.com/cd/E18659_01/html/821-1384/gjzke.html
+ * XLC: https://www.ibm.com/support/knowledgecenter/SSGH2K_13.1.2/com.ibm.xlc131.aix.doc/language_ref/function_attributes.html
+ * XLC: https://www.ibm.com/support/knowledgecenter/SSGH2K_13.1.2/com.ibm.xlc131.aix.doc/language_ref/type_attrib.html
  */
 
 /*
@@ -182,8 +184,8 @@
 #define PG_USED_FOR_ASSERTS_ONLY pg_attribute_unused()
 #endif
 
-/* GCC supports format attributes */
-#if defined(__GNUC__)
+/* GCC and XLC support format attributes */
+#if defined(__GNUC__) || defined(__IBMC__)
 #define pg_attribute_format_arg(a) __attribute__((format_arg(a)))
 #define pg_attribute_printf(f,a) __attribute__((format(PG_PRINTF_ATTRIBUTE, f, a)))
 #else
@@ -191,8 +193,8 @@
 #define pg_attribute_printf(f,a)
 #endif
 
-/* GCC and Sunpro support aligned, packed and noreturn */
-#if defined(__GNUC__) || defined(__SUNPRO_C)
+/* GCC, Sunpro and XLC support aligned, packed and noreturn */
+#if defined(__GNUC__) || defined(__SUNPRO_C) || defined(__IBMC__)
 #define pg_attribute_aligned(a) __attribute__((aligned(a)))
 #define pg_attribute_noreturn() __attribute__((noreturn))
 #define pg_attribute_packed() __attribute__((packed))
@@ -223,8 +225,8 @@
  * choose not to.  But, if possible, don't force inlining in unoptimized
  * debug builds.
  */
-#if (defined(__GNUC__) && __GNUC__ > 3 && defined(__OPTIMIZE__)) || defined(__SUNPRO_C)
-/* GCC > 3 and Sunpro support always_inline via __attribute__ */
+#if (defined(__GNUC__) && __GNUC__ > 3 && defined(__OPTIMIZE__)) || defined(__SUNPRO_C) || defined(__IBMC__)
+/* GCC > 3, Sunpro and XLC support always_inline via __attribute__ */
 #define pg_attribute_always_inline __attribute__((always_inline)) inline
 #elif defined(_MSC_VER)
 /* MSVC has a special keyword for this */
@@ -240,8 +242,8 @@
  * for proper cost attribution.  Note that unlike the pg_attribute_XXX macros
  * above, this should be placed before the function's return type and name.
  */
-/* GCC and Sunpro support noinline via __attribute__ */
-#if (defined(__GNUC__) && __GNUC__ > 2) || defined(__SUNPRO_C)
+/* GCC, Sunpro and XLC support noinline via __attribute__ */
+#if (defined(__GNUC__) && __GNUC__ > 2) || defined(__SUNPRO_C) || defined(__IBMC__)
 #define pg_noinline __attribute__((noinline))
 /* msvc via declspec */
 #elif defined(_MSC_VER)
diff --git a/src/include/port/aix.h b/src/include/port/aix.h
new file mode 100644
index 0000000000..5b1159c578
--- /dev/null
+++ b/src/include/port/aix.h
@@ -0,0 +1,14 @@
+/*
+ * src/include/port/aix.h
+ */
+#define CLASS_CONFLICT
+#define DISABLE_XOPEN_NLS
+
+/*
+ * "IBM XL C/C++ for AIX, V12.1" miscompiles, for 32-bit, some inline
+ * expansions of ginCompareItemPointers() "long long" arithmetic.  To take
+ * advantage of inlining, build a 64-bit PostgreSQL.
+ */
+#if defined(__ILP32__) && defined(__IBMC__)
+#define PG_FORCE_DISABLE_INLINE
+#endif
diff --git a/src/include/port/atomics.h b/src/include/port/atomics.h
index 78987f3154..5b2b70fe5f 100644
--- a/src/include/port/atomics.h
+++ b/src/include/port/atomics.h
@@ -84,9 +84,11 @@
  * using compiler intrinsics are a good idea.
  */
 /*
- * gcc or compatible, including clang and icc.
+ * gcc or compatible, including clang and icc.  Exclude xlc.  The ppc64le "IBM
+ * XL C/C++ for Linux, V13.1.2" emulates gcc, but __sync_lock_test_and_set()
+ * of one-byte types elicits SIGSEGV.  That bug was gone by V13.1.5 (2016-12).
  */
-#if defined(__GNUC__) || defined(__INTEL_COMPILER)
+#if (defined(__GNUC__) || defined(__INTEL_COMPILER)) && !(defined(__IBMC__) || defined(__IBMCPP__))
 #include "port/atomics/generic-gcc.h"
 #elif defined(_MSC_VER)
 #include "port/atomics/generic-msvc.h"
diff --git a/src/include/storage/s_lock.h b/src/include/storage/s_lock.h
index 29ac6cdcd9..69582f4ae7 100644
--- a/src/include/storage/s_lock.h
+++ b/src/include/storage/s_lock.h
@@ -414,6 +414,12 @@ typedef unsigned int slock_t;
  * an isync is a sufficient synchronization barrier after a lwarx/stwcx loop.
  * But if the spinlock is in ordinary memory, we can use lwsync instead for
  * better performance.
+ *
+ * Ordinarily, we'd code the branches here using GNU-style local symbols, that
+ * is "1f" referencing "1:" and so on.  But some people run gcc on AIX with
+ * IBM's assembler as backend, and IBM's assembler doesn't do local symbols.
+ * So hand-code the branch offsets; fortunately, all PPC instructions are
+ * exactly 4 bytes each, so it's not too hard to count.
  */
 static __inline__ int
 tas(volatile slock_t *lock)
@@ -424,17 +430,15 @@ tas(volatile slock_t *lock)
 	__asm__ __volatile__(
 "	lwarx   %0,0,%3,1	\n"
 "	cmpwi   %0,0		\n"
-"	bne     1f			\n"
+"	bne     $+16		\n"		/* branch to li %1,1 */
 "	addi    %0,%0,1		\n"
 "	stwcx.  %0,0,%3		\n"
-"	beq     2f			\n"
-"1: \n"
+"	beq     $+12		\n"		/* branch to lwsync */
 "	li      %1,1		\n"
-"	b       3f			\n"
-"2: \n"
+"	b       $+12		\n"		/* branch to end of asm sequence */
 "	lwsync				\n"
 "	li      %1,0		\n"
-"3: \n"
+
 :	"=&b"(_t), "=r"(_res), "+m"(*lock)
 :	"r"(lock)
 :	"memory", "cc");
@@ -662,6 +666,21 @@ tas(volatile slock_t *lock)
 
 #if !defined(HAS_TEST_AND_SET)	/* We didn't trigger above, let's try here */
 
+#if defined(_AIX)	/* AIX */
+/*
+ * AIX (POWER)
+ */
+#define HAS_TEST_AND_SET
+
+#include <sys/atomic_op.h>
+
+typedef int slock_t;
+
+#define TAS(lock)			_check_lock((slock_t *) (lock), 0, 1)
+#define S_UNLOCK(lock)		_clear_lock((slock_t *) (lock), 0)
+#endif	 /* _AIX */
+
+
 /* These are in sunstudio_(sparc|x86).s */
 
 #if defined(__SUNPRO_C) && (defined(__i386) || defined(__x86_64__) || defined(__sparc__) || defined(__sparc))
diff --git a/src/interfaces/libpq/Makefile b/src/interfaces/libpq/Makefile
index b36a765764..154429d4d1 100644
--- a/src/interfaces/libpq/Makefile
+++ b/src/interfaces/libpq/Makefile
@@ -114,7 +114,7 @@ backend_src = $(top_srcdir)/src/backend
 # coding rule.
 libpq-refs-stamp: $(shlib)
 ifneq ($(enable_coverage), yes)
-ifeq (,$(filter solaris,$(PORTNAME)))
+ifeq (,$(filter aix solaris,$(PORTNAME)))
 	@if nm -A -u $< 2>/dev/null | grep -v -e __cxa_atexit -e __tsan_func_exit | grep exit; then \
 		echo 'libpq must not be calling any function which invokes exit'; exit 1; \
 	fi
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index ed2a4048d1..7e2017daf0 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -54,8 +54,9 @@ libpq_c_args = ['-DSO_MAJOR_VERSION=5']
 #    libpq_st, and {pgport,common}_shlib for libpq_sh
 #
 # We could try to avoid building the source files twice, but it probably adds
-# more complexity than its worth (reusing object files requires also linking
-# to the library on windows or breaks precompiled headers).
+# more complexity than its worth (AIX doesn't support link_whole yet, reusing
+# object files requires also linking to the library on windows or breaks
+# precompiled headers).
 libpq_st = static_library('libpq',
   libpq_sources,
   include_directories: [libpq_inc],
diff --git a/src/makefiles/Makefile.aix b/src/makefiles/Makefile.aix
new file mode 100644
index 0000000000..dd16a7a037
--- /dev/null
+++ b/src/makefiles/Makefile.aix
@@ -0,0 +1,39 @@
+# MAKE_EXPORTS is required for svr4 loaders that want a file of
+# symbol names to tell them what to export/import.
+MAKE_EXPORTS= true
+
+# -blibpath must contain ALL directories where we should look for libraries
+libpath := $(shell echo $(subst -L,:,$(filter -L/%,$(LDFLAGS))) | sed -e's/ //g'):/usr/lib:/lib
+
+# when building with gcc, need to make sure that libgcc can be found
+ifeq ($(GCC), yes)
+libpath := $(libpath):$(dir $(shell gcc -print-libgcc-file-name))
+endif
+
+rpath = -Wl,-blibpath:'$(rpathdir)$(libpath)'
+
+LDFLAGS_SL += -Wl,-bnoentry -Wl,-H512 -Wl,-bM:SRE
+
+# gcc needs to know it's building a shared lib, otherwise it'll not emit
+# correct code / link to the right support libraries
+ifeq ($(GCC), yes)
+LDFLAGS_SL += -shared
+endif
+
+# env var name to use in place of LD_LIBRARY_PATH
+ld_library_path_var = LIBPATH
+
+
+POSTGRES_IMP= postgres.imp
+
+ifdef PGXS
+BE_DLLLIBS= -Wl,-bI:$(pkglibdir)/$(POSTGRES_IMP)
+else
+BE_DLLLIBS= -Wl,-bI:$(top_builddir)/src/backend/$(POSTGRES_IMP)
+endif
+
+MKLDEXPORT_DIR=src/backend/port/aix
+MKLDEXPORT=$(top_srcdir)/$(MKLDEXPORT_DIR)/mkldexport.sh
+
+%$(DLSUFFIX): %.o
+	$(CC) $(CFLAGS) $*.o $(LDFLAGS) $(LDFLAGS_SL) -o $@ $(BE_DLLLIBS)
diff --git a/src/port/README b/src/port/README
index ed5c54a72f..97f18a6233 100644
--- a/src/port/README
+++ b/src/port/README
@@ -28,5 +28,5 @@ applications.
 from libpgport are linked first.  This avoids having applications
 dependent on symbols that are _used_ by libpq, but not intended to be
 exported by libpq.  libpq's libpgport usage changes over time, so such a
-dependency is a problem.  Windows, Linux, and macOS use an export
+dependency is a problem.  Windows, Linux, AIX, and macOS use an export
 list to control the symbols exported by libpq.
diff --git a/src/port/strerror.c b/src/port/strerror.c
index 4918ba821c..1070a49802 100644
--- a/src/port/strerror.c
+++ b/src/port/strerror.c
@@ -214,8 +214,10 @@ get_errno_symbol(int errnum)
 			return "ENOTCONN";
 		case ENOTDIR:
 			return "ENOTDIR";
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:
 			return "ENOTEMPTY";
+#endif
 		case ENOTSOCK:
 			return "ENOTSOCK";
 #ifdef ENOTSUP
diff --git a/src/template/aix b/src/template/aix
new file mode 100644
index 0000000000..47fa8990a7
--- /dev/null
+++ b/src/template/aix
@@ -0,0 +1,25 @@
+# src/template/aix
+
+# Set default options if using xlc.  This formerly included -qsrcmsg, but that
+# option elicits internal compiler errors from xlc v16.1.0.  Note: configure
+# will add -qnoansialias if the compiler accepts it, even if user specifies a
+# non-default CFLAGS setting.
+if test "$GCC" != yes ; then
+  case $host_os in
+    *)
+      CFLAGS="-O2 -qmaxmem=16384"
+      ;;
+  esac
+
+  # Due to a compiler bug, see 20171013023536.GA492146@rfd.leadboat.com for details,
+  # force restrict not to be used when compiling with xlc.
+  FORCE_DISABLE_RESTRICT=yes
+fi
+
+# Extra CFLAGS for code that will go into a shared library
+CFLAGS_SL=""
+
+# Native memset() is faster, tested on:
+# 	AIX 5.1 and 5.2, XLC 6.0 (IBM's cc)
+# 	AIX 5.3 ML3, gcc 4.0.1
+MEMSET_LOOP_LIMIT=0
diff --git a/src/test/regress/Makefile b/src/test/regress/Makefile
index 6409a485e8..7c665ff892 100644
--- a/src/test/regress/Makefile
+++ b/src/test/regress/Makefile
@@ -7,6 +7,11 @@
 # GNU make uses a make file named "GNUmakefile" in preference to "Makefile"
 # if it exists.  Postgres is shipped with a "GNUmakefile".
 
+
+# AIX make defaults to building *every* target of the first rule.  Start with
+# a single-target, empty rule to make the other targets non-default.
+all:
+
 all install clean check installcheck:
 	@echo "You must use GNU make to use Postgres.  It may be installed"
 	@echo "on your system with the name 'gmake'."
diff --git a/src/test/regress/expected/sanity_check.out b/src/test/regress/expected/sanity_check.out
index 8370c1561c..c5c675b750 100644
--- a/src/test/regress/expected/sanity_check.out
+++ b/src/test/regress/expected/sanity_check.out
@@ -25,3 +25,32 @@ SELECT relname, relkind
 ---------+---------
 (0 rows)
 
+--
+-- When ALIGNOF_DOUBLE==4 (e.g. AIX), the C ABI may impose 8-byte alignment on
+-- some of the C types that correspond to TYPALIGN_DOUBLE SQL types.  To ensure
+-- catalog C struct layout matches catalog tuple layout, arrange for the tuple
+-- offset of each fixed-width, attalign='d' catalog column to be divisible by 8
+-- unconditionally.  Keep such columns before the first NameData column of the
+-- catalog, since packagers can override NAMEDATALEN to an odd number.
+--
+WITH check_columns AS (
+ SELECT relname, attname,
+  array(
+   SELECT t.oid
+    FROM pg_type t JOIN pg_attribute pa ON t.oid = pa.atttypid
+    WHERE pa.attrelid = a.attrelid AND
+          pa.attnum > 0 AND pa.attnum < a.attnum
+    ORDER BY pa.attnum) AS coltypes
+ FROM pg_attribute a JOIN pg_class c ON c.oid = attrelid
+  JOIN pg_namespace n ON c.relnamespace = n.oid
+ WHERE attalign = 'd' AND relkind = 'r' AND
+  attnotnull AND attlen <> -1 AND n.nspname = 'pg_catalog'
+)
+SELECT relname, attname, coltypes, get_columns_length(coltypes)
+ FROM check_columns
+ WHERE get_columns_length(coltypes) % 8 != 0 OR
+       'name'::regtype::oid = ANY(coltypes);
+ relname | attname | coltypes | get_columns_length 
+---------+---------+----------+--------------------
+(0 rows)
+
diff --git a/src/test/regress/expected/test_setup.out b/src/test/regress/expected/test_setup.out
index 3d0eeec996..5d9e6bf12b 100644
--- a/src/test/regress/expected/test_setup.out
+++ b/src/test/regress/expected/test_setup.out
@@ -209,6 +209,10 @@ CREATE FUNCTION ttdummy ()
     RETURNS trigger
     AS :'regresslib'
     LANGUAGE C;
+CREATE FUNCTION get_columns_length(oid[])
+    RETURNS int
+    AS :'regresslib'
+    LANGUAGE C STRICT STABLE PARALLEL SAFE;
 -- Use hand-rolled hash functions and operator classes to get predictable
 -- result on different machines.  The hash function for int4 simply returns
 -- the sum of the values passed to it and the one for text returns the length
diff --git a/src/test/regress/regress.c b/src/test/regress/regress.c
index deffaea578..cc633864d7 100644
--- a/src/test/regress/regress.c
+++ b/src/test/regress/regress.c
@@ -1221,3 +1221,43 @@ binary_coercible(PG_FUNCTION_ARGS)
 
 	PG_RETURN_BOOL(IsBinaryCoercible(srctype, targettype));
 }
+
+/*
+ * Return the length of the portion of a tuple consisting of the given array
+ * of data types.  The input data types must be fixed-length data types.
+ */
+PG_FUNCTION_INFO_V1(get_columns_length);
+Datum
+get_columns_length(PG_FUNCTION_ARGS)
+{
+	ArrayType  *ta = PG_GETARG_ARRAYTYPE_P(0);
+	Oid		   *type_oids;
+	int			ntypes;
+	int			column_offset = 0;
+
+	if (ARR_HASNULL(ta) && array_contains_nulls(ta))
+		elog(ERROR, "argument must not contain nulls");
+
+	if (ARR_NDIM(ta) > 1)
+		elog(ERROR, "argument must be empty or one-dimensional array");
+
+	type_oids = (Oid *) ARR_DATA_PTR(ta);
+	ntypes = ArrayGetNItems(ARR_NDIM(ta), ARR_DIMS(ta));
+	for (int i = 0; i < ntypes; i++)
+	{
+		Oid			typeoid = type_oids[i];
+		int16		typlen;
+		bool		typbyval;
+		char		typalign;
+
+		get_typlenbyvalalign(typeoid, &typlen, &typbyval, &typalign);
+
+		/* the data type must be fixed-length */
+		if (typlen < 0)
+			elog(ERROR, "type %u is not fixed-length data type", typeoid);
+
+		column_offset = att_align_nominal(column_offset + typlen, typalign);
+	}
+
+	PG_RETURN_INT32(column_offset);
+}
diff --git a/src/test/regress/sql/sanity_check.sql b/src/test/regress/sql/sanity_check.sql
index 162e5324b5..7f338d191c 100644
--- a/src/test/regress/sql/sanity_check.sql
+++ b/src/test/regress/sql/sanity_check.sql
@@ -19,3 +19,29 @@ SELECT relname, relkind
   FROM pg_class
  WHERE relkind IN ('v', 'c', 'f', 'p', 'I')
        AND relfilenode <> 0;
+
+--
+-- When ALIGNOF_DOUBLE==4 (e.g. AIX), the C ABI may impose 8-byte alignment on
+-- some of the C types that correspond to TYPALIGN_DOUBLE SQL types.  To ensure
+-- catalog C struct layout matches catalog tuple layout, arrange for the tuple
+-- offset of each fixed-width, attalign='d' catalog column to be divisible by 8
+-- unconditionally.  Keep such columns before the first NameData column of the
+-- catalog, since packagers can override NAMEDATALEN to an odd number.
+--
+WITH check_columns AS (
+ SELECT relname, attname,
+  array(
+   SELECT t.oid
+    FROM pg_type t JOIN pg_attribute pa ON t.oid = pa.atttypid
+    WHERE pa.attrelid = a.attrelid AND
+          pa.attnum > 0 AND pa.attnum < a.attnum
+    ORDER BY pa.attnum) AS coltypes
+ FROM pg_attribute a JOIN pg_class c ON c.oid = attrelid
+  JOIN pg_namespace n ON c.relnamespace = n.oid
+ WHERE attalign = 'd' AND relkind = 'r' AND
+  attnotnull AND attlen <> -1 AND n.nspname = 'pg_catalog'
+)
+SELECT relname, attname, coltypes, get_columns_length(coltypes)
+ FROM check_columns
+ WHERE get_columns_length(coltypes) % 8 != 0 OR
+       'name'::regtype::oid = ANY(coltypes);
diff --git a/src/test/regress/sql/test_setup.sql b/src/test/regress/sql/test_setup.sql
index 06b0e2121f..1b2d434683 100644
--- a/src/test/regress/sql/test_setup.sql
+++ b/src/test/regress/sql/test_setup.sql
@@ -257,6 +257,11 @@ CREATE FUNCTION ttdummy ()
     AS :'regresslib'
     LANGUAGE C;
 
+CREATE FUNCTION get_columns_length(oid[])
+    RETURNS int
+    AS :'regresslib'
+    LANGUAGE C STRICT STABLE PARALLEL SAFE;
+
 -- Use hand-rolled hash functions and operator classes to get predictable
 -- result on different machines.  The hash function for int4 simply returns
 -- the sum of the values passed to it and the one for text returns the length
diff --git a/src/tools/gen_export.pl b/src/tools/gen_export.pl
index d9fdaaaf6d..888c8a197a 100644
--- a/src/tools/gen_export.pl
+++ b/src/tools/gen_export.pl
@@ -16,11 +16,12 @@ GetOptions(
 	'input:s' => \$input,
 	'output:s' => \$output) or die "wrong arguments";
 
-if (not(   $format eq 'darwin'
+if (not(   $format eq 'aix'
+		or $format eq 'darwin'
 		or $format eq 'gnu'
 		or $format eq 'win'))
 {
-	die "$0: $format is not yet handled (only darwin, gnu, win are)\n";
+	die "$0: $format is not yet handled (only aix, darwin, gnu, win are)\n";
 }
 
 open(my $input_handle, '<', $input)
@@ -55,7 +56,11 @@ while (<$input_handle>)
 	}
 	elsif (/^(\S+)\s+(\S+)/)
 	{
-		if ($format eq 'darwin')
+		if ($format eq 'aix')
+		{
+			print $output_handle "$1\n";
+		}
+		elsif ($format eq 'darwin')
 		{
 			print $output_handle "_$1\n";
 		}
diff --git a/src/tools/pginclude/headerscheck b/src/tools/pginclude/headerscheck
index 4a157d0a5f..cfd8c6896c 100755
--- a/src/tools/pginclude/headerscheck
+++ b/src/tools/pginclude/headerscheck
@@ -85,6 +85,7 @@ do
 
 	# These files are platform-specific, and c.h will include the
 	# one that's relevant for our current platform anyway.
+	test "$f" = src/include/port/aix.h && continue
 	test "$f" = src/include/port/cygwin.h && continue
 	test "$f" = src/include/port/darwin.h && continue
 	test "$f" = src/include/port/freebsd.h && continue
-- 
2.41.0

From b88f2a8cad14c09bd872f303a27a60e93a916fea Mon Sep 17 00:00:00 2001
From: Sriram RK <sriram.rk@in.ibm.com>
Date: Mon, 20 May 2024 01:38:59 -0500
Subject: [PATCH 1/1] AIX support, revert the changes from 0b16bb8776bb8. Trim
 AIX/XLC changes to support gcc only.

---
 Makefile                                      |   2 -
 configure                                     |  52 ++++----
 configure.ac                                  |  31 ++---
 doc/src/sgml/dfunc.sgml                       |  19 +++
 doc/src/sgml/installation.sgml                | 118 +++++++++++++++++-
 doc/src/sgml/runtime.sgml                     |  23 ++++
 meson.build                                   |  57 +++++----
 src/Makefile.shlib                            |  29 +++++
 src/backend/Makefile                          |  20 +++
 src/backend/meson.build                       |  15 +++
 src/backend/port/aix/mkldexport.sh            |  61 +++++++++
 src/backend/utils/error/elog.c                |   2 +
 src/backend/utils/misc/ps_status.c            |   4 +-
 src/bin/pg_basebackup/t/010_pg_basebackup.pl  |   3 +-
 src/bin/pg_verifybackup/t/008_untar.pl        |   3 +-
 src/bin/pg_verifybackup/t/010_client_untar.pl |   3 +-
 src/include/c.h                               |   4 +-
 src/include/port/aix.h                        |  14 +++
 src/include/storage/s_lock.h                  |  31 ++++-
 src/interfaces/libpq/Makefile                 |   2 +-
 src/interfaces/libpq/meson.build              |   5 +-
 src/makefiles/Makefile.aix                    |  39 ++++++
 src/port/README                               |   2 +-
 src/port/strerror.c                           |   2 +
 src/template/aix                              |  26 ++++
 src/test/regress/Makefile                     |   5 +
 src/test/regress/expected/sanity_check.out    |  29 +++++
 src/test/regress/expected/test_setup.out      |   4 +
 src/test/regress/regress.c                    |  40 ++++++
 src/test/regress/sql/sanity_check.sql         |  26 ++++
 src/test/regress/sql/test_setup.sql           |   5 +
 src/tools/gen_export.pl                       |  11 +-
 src/tools/pginclude/headerscheck              |   1 +
 33 files changed, 598 insertions(+), 90 deletions(-)
 create mode 100755 src/backend/port/aix/mkldexport.sh
 create mode 100644 src/include/port/aix.h
 create mode 100644 src/makefiles/Makefile.aix
 create mode 100644 src/template/aix

diff --git a/Makefile b/Makefile
index 8a2ec9396b..9bc1a4ec17 100644
--- a/Makefile
+++ b/Makefile
@@ -13,8 +13,6 @@
 
 # AIX make defaults to building *every* target of the first rule.  Start with
 # a single-target, empty rule to make the other targets non-default.
-# (We don't support AIX anymore, but if someone tries to build on AIX anyway,
-# at least they'll get the instructions to run 'configure' first.)
 all:
 
 all check install installdirs installcheck installcheck-parallel uninstall clean distclean maintainer-clean dist distcheck world check-world install-world installcheck-world:
diff --git a/configure b/configure
index 89644f2249..03271f1861 100755
--- a/configure
+++ b/configure
@@ -2988,6 +2988,7 @@ else
 # --with-template not given
 
 case $host_os in
+     aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -6849,6 +6850,11 @@ if test x"$pgac_cv_prog_CXX_cxxflags__fno_strict_aliasing" = x"yes"; then
 fi
 
 
+elif test "$PORTNAME" = "aix"; then
+  # AIX's xlc has to have strict aliasing turned off too
+  # Igonoring the XLC falgs -qnoansialias, -qlonglong
+{ $as_echo_n "Running AIX gcc for now... " >&6; }
+
 fi
 
 # If the compiler knows how to hide symbols, add the switch needed for that to
@@ -7003,6 +7009,9 @@ if test x"$pgac_cv_prog_CXX_cxxflags__fvisibility_inlines_hidden" = x"yes"; then
 fi
 
   have_visibility_attribute=$pgac_cv_prog_CC_cflags__fvisibility_hidden
+elif test "$PORTNAME" = "aix"; then
+  # Note that xlc accepts -fvisibility=hidden as a file.
+  { $as_echo_n "Running AIX gcc for now... " >&6; }
 fi
 
 if test "$have_visibility_attribute" = "yes"; then
@@ -12860,7 +12869,8 @@ fi
 
 fi
 
-# Note: We can test for libldap_r only after we know PTHREAD_LIBS
+# Note: We can test for libldap_r only after we know PTHREAD_LIBS;
+# also, on AIX, we may need to have openssl in LIBS for this step.
 if test "$with_ldap" = yes ; then
   _LIBS="$LIBS"
   if test "$PORTNAME" != "win32"; then
@@ -14718,6 +14728,10 @@ fi
 # spelling it understands, because it conflicts with
 # __declspec(restrict). Therefore we define pg_restrict to the
 # appropriate definition, which presumably won't conflict.
+#
+# Allow platforms with buggy compilers to force restrict to not be
+# used by setting $FORCE_DISABLE_RESTRICT=yes in the relevant
+# template.
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for C/C++ restrict keyword" >&5
 $as_echo_n "checking for C/C++ restrict keyword... " >&6; }
 if ${ac_cv_c_restrict+:} false; then :
@@ -14764,7 +14778,7 @@ _ACEOF
  ;;
  esac
 
-if test "$ac_cv_c_restrict" = "no"; then
+if test "$ac_cv_c_restrict" = "no" -o "x$FORCE_DISABLE_RESTRICT" = "xyes"; then
   pg_restrict=""
 else
   pg_restrict="$ac_cv_c_restrict"
@@ -16951,28 +16965,18 @@ _ACEOF
 
 
 # Compute maximum alignment of any basic type.
-#
-# We require 'double' to have the strictest alignment among the basic types,
-# because otherwise the C ABI might impose 8-byte alignment on some of the
-# other C types that correspond to TYPALIGN_DOUBLE SQL types.  That could
-# cause a mismatch between the tuple layout and the C struct layout of a
-# catalog tuple.  We used to carefully order catalog columns such that any
-# fixed-width, attalign=4 columns were at offsets divisible by 8 regardless
-# of MAXIMUM_ALIGNOF to avoid that, but we no longer support any platforms
-# where TYPALIGN_DOUBLE != MAXIMUM_ALIGNOF.
-#
-# We assume without checking that long's alignment is at least as strong as
-# char, short, or int.  Note that we intentionally do not consider any types
-# wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
-# much of a penalty for disk and memory space.
-
-MAX_ALIGNOF=$ac_cv_alignof_double
-
-if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
-fi
-if test x"$HAVE_LONG_LONG_INT_64" = xyes && test $ac_cv_alignof_long_long_int -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'long long int' is greater than the alignment of 'double'" "$LINENO" 5
+# We assume long's alignment is at least as strong as char, short, or int;
+# but we must check long long (if it is being used for int64) and double.
+# Note that we intentionally do not consider any types wider than 64 bits,
+# as allowing MAXIMUM_ALIGNOF to exceed 8 would be too much of a penalty
+# for disk and memory space.
+
+MAX_ALIGNOF=$ac_cv_alignof_long
+if test $MAX_ALIGNOF -lt $ac_cv_alignof_double ; then
+  MAX_ALIGNOF=$ac_cv_alignof_double
+fi
+if test x"$HAVE_LONG_LONG_INT_64" = xyes && test $MAX_ALIGNOF -lt $ac_cv_alignof_long_long_int ; then
+  MAX_ALIGNOF="$ac_cv_alignof_long_long_int"
 fi
 
 cat >>confdefs.h <<_ACEOF
diff --git a/configure.ac b/configure.ac
index c7322e292c..22069395a6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -62,6 +62,7 @@ PGAC_ARG_REQ(with, template, [NAME], [override operating system template],
 # --with-template not given
 
 case $host_os in
+     aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -1385,7 +1386,8 @@ if test "$with_zstd" = yes ; then
   AC_CHECK_LIB(zstd, ZSTD_compress, [], [AC_MSG_ERROR([library 'zstd' is required for ZSTD support])])
 fi
 
-# Note: We can test for libldap_r only after we know PTHREAD_LIBS
+# Note: We can test for libldap_r only after we know PTHREAD_LIBS;
+# also, on AIX, we may need to have openssl in LIBS for this step.
 if test "$with_ldap" = yes ; then
   _LIBS="$LIBS"
   if test "$PORTNAME" != "win32"; then
@@ -1643,8 +1645,12 @@ PGAC_TYPE_LOCALE_T
 # spelling it understands, because it conflicts with
 # __declspec(restrict). Therefore we define pg_restrict to the
 # appropriate definition, which presumably won't conflict.
+#
+# Allow platforms with buggy compilers to force restrict to not be
+# used by setting $FORCE_DISABLE_RESTRICT=yes in the relevant
+# template.
 AC_C_RESTRICT
-if test "$ac_cv_c_restrict" = "no"; then
+if test "$ac_cv_c_restrict" = "no" -o "x$FORCE_DISABLE_RESTRICT" = "xyes"; then
   pg_restrict=""
 else
   pg_restrict="$ac_cv_c_restrict"
@@ -1996,22 +2002,11 @@ fi
 AC_CHECK_ALIGNOF(double)
 
 # Compute maximum alignment of any basic type.
-#
-# We require 'double' to have the strictest alignment among the basic types,
-# because otherwise the C ABI might impose 8-byte alignment on some of the
-# other C types that correspond to TYPALIGN_DOUBLE SQL types.  That could
-# cause a mismatch between the tuple layout and the C struct layout of a
-# catalog tuple.  We used to carefully order catalog columns such that any
-# fixed-width, attalign=4 columns were at offsets divisible by 8 regardless
-# of MAXIMUM_ALIGNOF to avoid that, but we no longer support any platforms
-# where TYPALIGN_DOUBLE != MAXIMUM_ALIGNOF.
-#
-# We assume without checking that long's alignment is at least as strong as
-# char, short, or int.  Note that we intentionally do not consider any types
-# wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
-# much of a penalty for disk and memory space.
-
-MAX_ALIGNOF=$ac_cv_alignof_double
+# We assume long's alignment is at least as strong as char, short, or int;
+# but we must check long long (if it is being used for int64) and double.
+# Note that we intentionally do not consider any types wider than 64 bits,
+# as allowing MAXIMUM_ALIGNOF to exceed 8 would be too much of a penalty
+# for disk and memory space.
 
 if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
   AC_MSG_ERROR([alignment of 'long' is greater than the alignment of 'double'])
diff --git a/doc/src/sgml/dfunc.sgml b/doc/src/sgml/dfunc.sgml
index b94aefcd0c..554f9fac4c 100644
--- a/doc/src/sgml/dfunc.sgml
+++ b/doc/src/sgml/dfunc.sgml
@@ -202,4 +202,23 @@ gcc -G -o foo.so foo.o
   server expects to find the shared library files.
  </para>
 
+<!--
+Under AIX, object files are compiled normally but building the shared
+library requires a couple of steps.  First, create the object file:
+.nf
+cc <other flags> -c foo.c
+.fi
+You must then create a symbol \*(lqexports\*(rq file for the object
+file:
+.nf
+mkldexport foo.o `pwd` &gt; foo.exp
+.fi
+Finally, you can create the shared library:
+.nf
+ld <other flags> -H512 -T512 -o foo.so -e _nostart \e
+   -bI:.../lib/postgres.exp -bE:foo.exp foo.o \e
+   -lm -lc 2>/dev/null
+.fi
+  -->
+
 </sect2>
diff --git a/doc/src/sgml/installation.sgml b/doc/src/sgml/installation.sgml
index 1b32d5ca62..60e9a34a03 100644
--- a/doc/src/sgml/installation.sgml
+++ b/doc/src/sgml/installation.sgml
@@ -3401,7 +3401,7 @@ export MANPATH
   <para>
    <productname>PostgreSQL</productname> can be expected to work on current
    versions of these operating systems: Linux, Windows,
-   FreeBSD, OpenBSD, NetBSD, DragonFlyBSD, macOS, Solaris, and illumos.
+   FreeBSD, OpenBSD, NetBSD, DragonFlyBSD, macOS, AIX, Solaris, and illumos.
    Other Unix-like systems may also work but are not currently
    being tested.  In most cases, all CPU architectures supported by
    a given operating system will work.  Look in
@@ -3445,6 +3445,122 @@ export MANPATH
    installation issues.
   </para>
 
+  <sect2 id="installation-notes-aix">
+   <title>AIX</title>
+
+   <indexterm zone="installation-notes-aix">
+    <primary>AIX</primary>
+    <secondary>installation on</secondary>
+   </indexterm>
+
+   <para>
+    You can use GCC to build <productname>PostgreSQL</productname>
+    on <productname>AIX</productname>.
+   </para>
+
+   <para>
+    <productname>AIX</productname> versions before 7.1 are no longer
+    tested nor supported by the <productname>PostgreSQL</productname>
+    community.
+   </para>
+
+   <sect3 id="installation-notes-aix-mem-management">
+    <title>Memory Management</title>
+    <!-- https://archives.postgresql.org/message-id/603bgqmpl9.fsf@dba2.int.libertyrms.com -->
+
+    <para>
+     AIX can be somewhat peculiar with regards to the way it does
+     memory management.  You can have a server with many multiples of
+     gigabytes of RAM free, but still get out of memory or address
+     space errors when running applications.  One example
+     is loading of extensions failing with unusual errors.
+     For example, running as the owner of the PostgreSQL installation:
+<screen>
+=# CREATE EXTENSION plperl;
+ERROR:  could not load library "/opt/dbs/pgsql/lib/plperl.so": A memory address is not in the address space for the process.
+</screen>
+    Running as a non-owner in the group possessing the PostgreSQL
+    installation:
+<screen>
+=# CREATE EXTENSION plperl;
+ERROR:  could not load library "/opt/dbs/pgsql/lib/plperl.so": Bad address
+</screen>
+     Another example is out of memory errors in the PostgreSQL server
+     logs, with every memory allocation near or greater than 256 MB
+     failing.
+    </para>
+
+    <para>
+     The overall cause of all these problems is the default bittedness
+     and memory model used by the server process.  By default, all
+     binaries built on AIX are 32-bit.  This does not depend upon
+     hardware type or kernel in use.  These 32-bit processes are
+     limited to 4 GB of memory laid out in 256 MB segments using one
+     of a few models.  The default allows for less than 256 MB in the
+     heap as it shares a single segment with the stack.
+    </para>
+
+    <para>
+     In the case of the <literal>plperl</literal> example, above,
+     check your umask and the permissions of the binaries in your
+     PostgreSQL installation.  The binaries involved in that example
+     were 32-bit and installed as mode 750 instead of 755.  Due to the
+     permissions being set in this fashion, only the owner or a member
+     of the possessing group can load the library.  Since it isn't
+     world-readable, the loader places the object into the process'
+     heap instead of the shared library segments where it would
+     otherwise be placed.
+    </para>
+
+    <para>
+     The <quote>ideal</quote> solution for this is to use a 64-bit
+     build of PostgreSQL, but that is not always practical, because
+     systems with 32-bit processors can build, but not run, 64-bit
+     binaries.
+    </para>
+
+    <para>
+     If a 32-bit binary is desired, set <symbol>LDR_CNTRL</symbol> to
+     <literal>MAXDATA=0x<replaceable>n</replaceable>0000000</literal>,
+     where 1 &lt;= n &lt;= 8, before starting the PostgreSQL server,
+     and try different values and <filename>postgresql.conf</filename>
+     settings to find a configuration that works satisfactorily.  This
+     use of <symbol>LDR_CNTRL</symbol> tells AIX that you want the
+     server to have <symbol>MAXDATA</symbol> bytes set aside for the
+     heap, allocated in 256 MB segments.  When you find a workable
+     configuration,
+     <command>ldedit</command> can be used to modify the binaries so
+     that they default to using the desired heap size.  PostgreSQL can
+     also be rebuilt, passing <literal>configure
+     LDFLAGS="-Wl,-bmaxdata:0x<replaceable>n</replaceable>0000000"</literal>
+     to achieve the same effect.
+    </para>
+
+    <para>
+     For a 64-bit build, set <envar>OBJECT_MODE</envar> to 64 and
+     pass <literal>CC="gcc -maix64"</literal>
+     and <literal>LDFLAGS="-Wl,-bbigtoc"</literal>
+     to <command>configure</command>. 
+     If you omit the export of
+    <envar>OBJECT_MODE</envar>, your build may fail with linker errors.  When
+    <envar>OBJECT_MODE</envar> is set, it tells AIX's build utilities
+    such as <command>ar</command>, <command>as</command>, and <command>ld</command> what
+    type of objects to default to handling.
+    </para>
+
+    <para>
+     By default, overcommit of paging space can happen.  While we have
+     not seen this occur, AIX will kill processes when it runs out of
+     memory and the overcommit is accessed.  The closest to this that
+     we have seen is fork failing because the system decided that
+     there was not enough memory for another process.  Like many other
+     parts of AIX, the paging space allocation method and
+     out-of-memory kill is configurable on a system- or process-wide
+     basis if this becomes a problem.
+    </para>
+   </sect3>
+  </sect2>
+
   <sect2 id="installation-notes-cygwin">
    <title>Cygwin</title>
 
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index 6047b8171d..64753d9c01 100644
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -891,6 +891,29 @@ psql: error: connection to server on socket "/tmp/.s.PGSQL.5432" failed: No such
 
 
     <variablelist>
+     <varlistentry>
+      <term><systemitem class="osname">AIX</systemitem>
+      <indexterm><primary>AIX</primary><secondary>IPC configuration</secondary></indexterm>
+      </term>
+      <listitem>
+       <para>
+        It should not be necessary to do
+        any special configuration for such parameters as
+        <varname>SHMMAX</varname>, as it appears this is configured to
+        allow all memory to be used as shared memory.  That is the
+        sort of configuration commonly used for other databases such
+        as <application>DB/2</application>.</para>
+
+       <para> It might, however, be necessary to modify the global
+       <command>ulimit</command> information in
+       <filename>/etc/security/limits</filename>, as the default hard
+       limits for file sizes (<varname>fsize</varname>) and numbers of
+       files (<varname>nofiles</varname>) might be too low.
+       </para>
+      </listitem>
+     </varlistentry>
+
+
      <varlistentry>
       <term><systemitem class="osname">FreeBSD</systemitem>
       <indexterm><primary>FreeBSD</primary><secondary>IPC configuration</secondary></indexterm>
diff --git a/meson.build b/meson.build
index 1c0579d5a6..f1ac154cdc 100644
--- a/meson.build
+++ b/meson.build
@@ -196,7 +196,26 @@ endif
 # that purpose.
 portname = host_system
 
-if host_system == 'cygwin'
+if host_system == 'aix'
+  library_path_var = 'LIBPATH'
+
+  export_file_format = 'aix'
+  export_fmt = '-Wl,-bE:@0@'
+  mod_link_args_fmt = ['-Wl,-bI:@0@']
+  mod_link_with_dir = 'libdir'
+  mod_link_with_name = '@0@.imp'
+
+  # M:SRE sets a flag indicating that an object is a shared library. Seems to
+  # work in some circumstances without, but required in others.
+  ldflags_sl += '-Wl,-bM:SRE'
+  ldflags_be += '-Wl,-brtllib'
+
+  # Native memset() is faster, tested on:
+  # - AIX 5.1 and 5.2, XLC 6.0 (IBM's cc)
+  # - AIX 5.3 ML3, gcc 4.0.1
+  memset_loop_limit = 0
+
+elif host_system == 'cygwin'
   sema_kind = 'unnamed_posix'
   cppflags += '-D_GNU_SOURCE'
   dlsuffix = '.dll'
@@ -1490,11 +1509,11 @@ sizeof_long = cc.sizeof('long', args: test_c_args)
 cdata.set('SIZEOF_LONG', sizeof_long)
 if sizeof_long == 8
   cdata.set('HAVE_LONG_INT_64', 1)
-  pg_int64_type = 'long int'
+  cdata.set('PG_INT64_TYPE', 'long int')
   cdata.set_quoted('INT64_MODIFIER', 'l')
 elif sizeof_long == 4 and cc.sizeof('long long', args: test_c_args) == 8
   cdata.set('HAVE_LONG_LONG_INT_64', 1)
-  pg_int64_type = 'long long int'
+  cdata.set('PG_INT64_TYPE', 'long long int')
   cdata.set_quoted('INT64_MODIFIER', 'll')
 else
   error('do not know how to get a 64bit int')
@@ -1508,31 +1527,15 @@ endif
 # Determine memory alignment requirements for the basic C data types.
 
 alignof_types = ['short', 'int', 'long', 'double']
+maxalign = 0
 foreach t : alignof_types
   align = cc.alignment(t, args: test_c_args)
+  if maxalign < align
+    maxalign = align
+  endif
   cdata.set('ALIGNOF_@0@'.format(t.to_upper()), align)
 endforeach
-
-# Compute maximum alignment of any basic type.
-#
-# We require 'double' to have the strictest alignment among the basic types,
-# because otherwise the C ABI might impose 8-byte alignment on some of the
-# other C types that correspond to TYPALIGN_DOUBLE SQL types.  That could
-# cause a mismatch between the tuple layout and the C struct layout of a
-# catalog tuple.  We used to carefully order catalog columns such that any
-# fixed-width, attalign=4 columns were at offsets divisible by 8 regardless
-# of MAXIMUM_ALIGNOF to avoid that, but we no longer support any platforms
-# where TYPALIGN_DOUBLE != MAXIMUM_ALIGNOF.
-#
-# We assume without checking that int64's alignment is at least as strong
-# as long, char, short, or int.  Note that we intentionally do not consider
-# any types wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8
-# would be too much of a penalty for disk and memory space.
-alignof_double = cdata.get('ALIGNOF_DOUBLE')
-if cc.alignment(pg_int64_type, args: test_c_args) > alignof_double
-  error('alignment of int64 is greater than the alignment of double')
-endif
-cdata.set('MAXIMUM_ALIGNOF', alignof_double)
+cdata.set('MAXIMUM_ALIGNOF', maxalign)
 
 cdata.set('SIZEOF_VOID_P', cc.sizeof('void *', args: test_c_args))
 cdata.set('SIZEOF_SIZE_T', cc.sizeof('size_t', args: test_c_args))
@@ -1581,7 +1584,7 @@ if cc.links('''
   if not meson.is_cross_build()
     r = cc.run('''
     /* This must match the corresponding code in c.h: */
-    #if defined(__GNUC__) || defined(__SUNPRO_C)
+    #if defined(__GNUC__) || defined(__SUNPRO_C) || defined(__IBMC__)
     #define pg_attribute_aligned(a) __attribute__((aligned(a)))
     #elif defined(_MSC_VER)
     #define pg_attribute_aligned(a) __declspec(align(a))
@@ -2476,6 +2479,10 @@ endif
 # conflict.
 #
 # We assume C99 support, so we don't need to make this conditional.
+#
+# XXX: Historically we allowed platforms to disable restrict in template
+# files, but that was only added for AIX when building with XLC, which we
+# don't support yet.
 cdata.set('pg_restrict', '__restrict')
 
 
diff --git a/src/Makefile.shlib b/src/Makefile.shlib
index fa81f6ffdd..8ca51ca03f 100644
--- a/src/Makefile.shlib
+++ b/src/Makefile.shlib
@@ -106,6 +106,20 @@ ifdef SO_MAJOR_VERSION
 override CPPFLAGS += -DSO_MAJOR_VERSION=$(SO_MAJOR_VERSION)
 endif
 
+ifeq ($(PORTNAME), aix)
+  LINK.shared		= $(COMPILER)
+  ifdef SO_MAJOR_VERSION
+    shlib		= lib$(NAME)$(DLSUFFIX).$(SO_MAJOR_VERSION)
+  endif
+  haslibarule   = yes
+  # $(exports_file) is also usable as an import file
+  exports_file		= lib$(NAME).exp
+  BUILD.exports		= ( echo '\#! $(shlib)'; $(AWK) '/^[^\#]/ {printf "%s\n",$$1}' $< ) > $@
+  ifneq (,$(SHLIB_EXPORTS))
+    LINK.shared		+= -Wl,-bE:$(exports_file)
+  endif
+endif
+
 ifeq ($(PORTNAME), darwin)
   ifdef soname
     # linkable library
@@ -254,6 +268,14 @@ $(stlib): $(OBJS) | $(SHLIB_PREREQS)
 	touch $@
 endif #haslibarule
 
+# AIX wraps shared libraries inside a static library, can be used both
+# for static and shared linking
+ifeq ($(PORTNAME), aix)
+$(stlib): $(shlib)
+	rm -f $(stlib)
+	$(AR) $(AROPT) $(stlib) $(shlib)
+endif # aix
+
 ifeq (,$(filter cygwin win32,$(PORTNAME)))
 
 # Normal case
@@ -267,8 +289,11 @@ ifneq ($(shlib), $(shlib_major))
 endif
 # Make sure we have a link to a name without any version numbers
 ifneq ($(shlib), $(shlib_bare))
+# except on AIX, where that's not a thing
+ifneq ($(PORTNAME), aix)
 	rm -f $(shlib_bare)
 	$(LN_S) $(shlib) $(shlib_bare)
+endif # aix
 endif # shlib_bare
 endif # shlib_major
 
@@ -376,6 +401,9 @@ install-lib-static: $(stlib) installdirs-lib
 
 install-lib-shared: $(shlib) installdirs-lib
 ifdef soname
+# we don't install $(shlib) on AIX
+# (see http://archives.postgresql.org/message-id/52EF20B2E3209443BC37736D00C3C1380A6E79FE@EXADV1.host.magwien.gv.at)
+ifneq ($(PORTNAME), aix)
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(libdir)/$(shlib)'
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
@@ -391,6 +419,7 @@ ifneq ($(shlib), $(shlib_bare))
 endif
 endif # not win32
 endif # not cygwin
+endif # not aix
 ifneq (,$(findstring $(PORTNAME),win32 cygwin))
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(bindir)/$(shlib)'
 endif
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 6700aec039..954b14962f 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -62,12 +62,14 @@ all: submake-libpgport submake-catalog-headers submake-utils-headers postgres $(
 
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
+ifneq ($(PORTNAME), aix)
 
 postgres: $(OBJS)
 	$(CC) $(CFLAGS) $(call expand_subsys,$^) $(LDFLAGS) $(LIBS) -o $@
 
 endif
 endif
+endif
 
 ifeq ($(PORTNAME), cygwin)
 
@@ -94,6 +96,24 @@ libpostgres.a: postgres
 
 endif # win32
 
+ifeq ($(PORTNAME), aix)
+
+postgres: $(POSTGRES_IMP)
+	$(CC) $(CFLAGS) $(call expand_subsys,$(OBJS)) $(LDFLAGS) -Wl,-bE:$(top_builddir)/src/backend/$(POSTGRES_IMP) $(LIBS) -Wl,-brtllib -o $@
+
+# Linking to a single .o with -r is a lot faster than building a .a or passing
+# all objects to MKLDEXPORT.
+#
+# It looks alluring to use $(CC) -r instead of ld -r, but that doesn't
+# trivially work with gcc, due to gcc specific static libraries linked in with
+# -r.
+$(POSTGRES_IMP): $(OBJS)
+	ld -r -o SUBSYS.o $(call expand_subsys,$^)
+	$(MKLDEXPORT) SUBSYS.o . > $@
+	@rm -f SUBSYS.o
+
+endif # aix
+
 $(top_builddir)/src/port/libpgport_srv.a: | submake-libpgport
 
 
diff --git a/src/backend/meson.build b/src/backend/meson.build
index 436c04af08..8767aaba67 100644
--- a/src/backend/meson.build
+++ b/src/backend/meson.build
@@ -91,6 +91,21 @@ if cc.get_id() == 'msvc'
   # be restricted to b_pch=true.
   backend_link_with += postgres_lib
 
+elif host_system == 'aix'
+  # The '.' argument leads mkldexport.sh to emit "#! .", which refers to the
+  # main executable, allowing extension libraries to resolve their undefined
+  # symbols to symbols in the postgres binary.
+  postgres_imp = custom_target('postgres.imp',
+    command: [files('port/aix/mkldexport.sh'), '@INPUT@', '.'],
+    input: postgres_lib,
+    output: 'postgres.imp',
+    capture: true,
+    install: true,
+    install_dir: dir_lib,
+    build_by_default: false,
+  )
+  backend_link_args += '-Wl,-bE:@0@'.format(postgres_imp.full_path())
+  backend_link_depends += postgres_imp
 endif
 
 backend_input = []
diff --git a/src/backend/port/aix/mkldexport.sh b/src/backend/port/aix/mkldexport.sh
new file mode 100755
index 0000000000..adf3793e86
--- /dev/null
+++ b/src/backend/port/aix/mkldexport.sh
@@ -0,0 +1,61 @@
+#!/bin/sh
+#
+# mkldexport
+#	create an AIX exports file from an object file
+#
+# src/backend/port/aix/mkldexport.sh
+#
+# Usage:
+#	mkldexport objectfile [location]
+# where
+#	objectfile is the current location of the object file.
+#	location is the eventual (installed) location of the
+#		object file (if different from the current
+#		working directory).
+#
+# [This file comes from the Postgres 4.2 distribution. - ay 7/95]
+#
+# Header: /usr/local/devel/postgres/src/tools/mkldexport/RCS/mkldexport.sh,v 1.2 1994/03/13 04:59:12 aoki Exp
+#
+
+# setting this to nm -B might be better
+# ... due to changes in AIX 4.x ...
+# ... let us search in different directories - Gerhard Reithofer
+if [ -x /usr/ucb/nm ]
+then NM=/usr/ucb/nm
+elif [ -x /usr/bin/nm ]
+then NM=/usr/bin/nm
+elif [ -x /usr/ccs/bin/nm ]
+then NM=/usr/ccs/bin/nm
+elif [ -x /usr/usg/bin/nm ]
+then NM=/usr/usg/bin/nm
+else echo "Fatal error: cannot find `nm' ... please check your installation."
+     exit 1
+fi
+
+CMDNAME=`basename $0`
+if [ -z "$1" ]; then
+	echo "Usage: $CMDNAME object [location]"
+	exit 1
+fi
+OBJNAME=`basename $1`
+if [ "`basename $OBJNAME`" != "`basename $OBJNAME .o`" ]; then
+	OBJNAME=`basename $OBJNAME .o`.so
+fi
+if [ -z "$2" ]; then
+	echo '#!'
+else
+	if [ "$2" = "." ]; then
+		# for the base executable (AIX 4.2 and up)
+		echo '#! .'
+	else
+		echo '#!' $2
+	fi
+fi
+$NM -BCg $1 | \
+	egrep ' [TDB] ' | \
+	sed -e 's/.* //' | \
+	egrep -v '\$' | \
+	sed -e 's/^[.]//' | \
+	sort | \
+	uniq
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index d91a85cb2d..7b51e94f4a 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -908,7 +908,9 @@ errcode_for_file_access(void)
 			/* Wrong object type or state */
 		case ENOTDIR:			/* Not a directory */
 		case EISDIR:			/* Is a directory */
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:			/* Directory not empty */
+#endif
 			edata->sqlerrcode = ERRCODE_WRONG_OBJECT_TYPE;
 			break;
 
diff --git a/src/backend/utils/misc/ps_status.c b/src/backend/utils/misc/ps_status.c
index 9da6377402..532eac31b4 100644
--- a/src/backend/utils/misc/ps_status.c
+++ b/src/backend/utils/misc/ps_status.c
@@ -50,7 +50,7 @@ bool		update_process_title = DEFAULT_UPDATE_PROCESS_TITLE;
 #define PS_USE_SETPROCTITLE_FAST
 #elif defined(HAVE_SETPROCTITLE)
 #define PS_USE_SETPROCTITLE
-#elif defined(__linux__) || defined(__sun) || defined(__darwin__)
+#elif defined(__linux__) || defined(_AIX) || defined(__sun) || defined(__darwin__)
 #define PS_USE_CLOBBER_ARGV
 #elif defined(WIN32)
 #define PS_USE_WIN32
@@ -60,7 +60,7 @@ bool		update_process_title = DEFAULT_UPDATE_PROCESS_TITLE;
 
 
 /* Different systems want the buffer padded differently */
-#if defined(__linux__) || defined(__darwin__)
+#if defined(_AIX) || defined(__linux__) || defined(__darwin__)
 #define PS_PADDING '\0'
 #else
 #define PS_PADDING ' '
diff --git a/src/bin/pg_basebackup/t/010_pg_basebackup.pl b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
index 2d4b75a6fe..ce936959c1 100644
--- a/src/bin/pg_basebackup/t/010_pg_basebackup.pl
+++ b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
@@ -401,7 +401,8 @@ SKIP:
 {
 	my $tar = $ENV{TAR};
 	# don't check for a working tar here, to accommodate various odd
-	# cases. If tar doesn't work the init_from_backup below will fail.
+	# cases such as AIX. If tar doesn't work the init_from_backup below
+	# will fail.
 	skip "no tar program available", 1
 	  if (!defined $tar || $tar eq '');
 
diff --git a/src/bin/pg_verifybackup/t/008_untar.pl b/src/bin/pg_verifybackup/t/008_untar.pl
index 7a09f3b75b..30d9f3f7f0 100644
--- a/src/bin/pg_verifybackup/t/008_untar.pl
+++ b/src/bin/pg_verifybackup/t/008_untar.pl
@@ -104,7 +104,8 @@ for my $tc (@test_configuration)
 		{
 			my $tar = $ENV{TAR};
 			# don't check for a working tar here, to accommodate various odd
-			# cases. If tar doesn't work the init_from_backup below will fail.
+			# cases such as AIX. If tar doesn't work the init_from_backup below
+			# will fail.
 			skip "no tar program available", 1
 			  if (!defined $tar || $tar eq '');
 
diff --git a/src/bin/pg_verifybackup/t/010_client_untar.pl b/src/bin/pg_verifybackup/t/010_client_untar.pl
index 8c076d46de..45010d79ac 100644
--- a/src/bin/pg_verifybackup/t/010_client_untar.pl
+++ b/src/bin/pg_verifybackup/t/010_client_untar.pl
@@ -134,7 +134,8 @@ for my $tc (@test_configuration)
 		{
 			my $tar = $ENV{TAR};
 			# don't check for a working tar here, to accommodate various odd
-			# cases. If tar doesn't work the init_from_backup below will fail.
+			# cases such as AIX. If tar doesn't work the init_from_backup below
+			# will fail.
 			skip "no tar program available", 1
 			  if (!defined $tar || $tar eq '');
 
diff --git a/src/include/c.h b/src/include/c.h
index dc1841346c..641cd9bdf1 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -182,7 +182,7 @@
 #define PG_USED_FOR_ASSERTS_ONLY pg_attribute_unused()
 #endif
 
-/* GCC supports format attributes */
+/* GCC support format attributes */
 #if defined(__GNUC__)
 #define pg_attribute_format_arg(a) __attribute__((format_arg(a)))
 #define pg_attribute_printf(f,a) __attribute__((format(PG_PRINTF_ATTRIBUTE, f, a)))
@@ -192,7 +192,7 @@
 #endif
 
 /* GCC and Sunpro support aligned, packed and noreturn */
-#if defined(__GNUC__) || defined(__SUNPRO_C)
+#if defined(__GNUC__) || defined(__SUNPRO_C) 
 #define pg_attribute_aligned(a) __attribute__((aligned(a)))
 #define pg_attribute_noreturn() __attribute__((noreturn))
 #define pg_attribute_packed() __attribute__((packed))
diff --git a/src/include/port/aix.h b/src/include/port/aix.h
new file mode 100644
index 0000000000..c54c95d4a5
--- /dev/null
+++ b/src/include/port/aix.h
@@ -0,0 +1,14 @@
+/*
+ * src/include/port/aix.h
+ */
+#define CLASS_CONFLICT
+#define DISABLE_XOPEN_NLS
+
+/* Commenting for XLC
+ * "IBM XL C/C++ for AIX, V12.1" miscompiles, for 32-bit, some inline
+ * expansions of ginCompareItemPointers() "long long" arithmetic.  To take
+ * advantage of inlining, build a 64-bit PostgreSQL.
+#if defined(__ILP32__) && defined(__IBMC__)
+#define PG_FORCE_DISABLE_INLINE
+#endif
+ */
diff --git a/src/include/storage/s_lock.h b/src/include/storage/s_lock.h
index 29ac6cdcd9..69582f4ae7 100644
--- a/src/include/storage/s_lock.h
+++ b/src/include/storage/s_lock.h
@@ -414,6 +414,12 @@ typedef unsigned int slock_t;
  * an isync is a sufficient synchronization barrier after a lwarx/stwcx loop.
  * But if the spinlock is in ordinary memory, we can use lwsync instead for
  * better performance.
+ *
+ * Ordinarily, we'd code the branches here using GNU-style local symbols, that
+ * is "1f" referencing "1:" and so on.  But some people run gcc on AIX with
+ * IBM's assembler as backend, and IBM's assembler doesn't do local symbols.
+ * So hand-code the branch offsets; fortunately, all PPC instructions are
+ * exactly 4 bytes each, so it's not too hard to count.
  */
 static __inline__ int
 tas(volatile slock_t *lock)
@@ -424,17 +430,15 @@ tas(volatile slock_t *lock)
 	__asm__ __volatile__(
 "	lwarx   %0,0,%3,1	\n"
 "	cmpwi   %0,0		\n"
-"	bne     1f			\n"
+"	bne     $+16		\n"		/* branch to li %1,1 */
 "	addi    %0,%0,1		\n"
 "	stwcx.  %0,0,%3		\n"
-"	beq     2f			\n"
-"1: \n"
+"	beq     $+12		\n"		/* branch to lwsync */
 "	li      %1,1		\n"
-"	b       3f			\n"
-"2: \n"
+"	b       $+12		\n"		/* branch to end of asm sequence */
 "	lwsync				\n"
 "	li      %1,0		\n"
-"3: \n"
+
 :	"=&b"(_t), "=r"(_res), "+m"(*lock)
 :	"r"(lock)
 :	"memory", "cc");
@@ -662,6 +666,21 @@ tas(volatile slock_t *lock)
 
 #if !defined(HAS_TEST_AND_SET)	/* We didn't trigger above, let's try here */
 
+#if defined(_AIX)	/* AIX */
+/*
+ * AIX (POWER)
+ */
+#define HAS_TEST_AND_SET
+
+#include <sys/atomic_op.h>
+
+typedef int slock_t;
+
+#define TAS(lock)			_check_lock((slock_t *) (lock), 0, 1)
+#define S_UNLOCK(lock)		_clear_lock((slock_t *) (lock), 0)
+#endif	 /* _AIX */
+
+
 /* These are in sunstudio_(sparc|x86).s */
 
 #if defined(__SUNPRO_C) && (defined(__i386) || defined(__x86_64__) || defined(__sparc__) || defined(__sparc))
diff --git a/src/interfaces/libpq/Makefile b/src/interfaces/libpq/Makefile
index b36a765764..154429d4d1 100644
--- a/src/interfaces/libpq/Makefile
+++ b/src/interfaces/libpq/Makefile
@@ -114,7 +114,7 @@ backend_src = $(top_srcdir)/src/backend
 # coding rule.
 libpq-refs-stamp: $(shlib)
 ifneq ($(enable_coverage), yes)
-ifeq (,$(filter solaris,$(PORTNAME)))
+ifeq (,$(filter aix solaris,$(PORTNAME)))
 	@if nm -A -u $< 2>/dev/null | grep -v -e __cxa_atexit -e __tsan_func_exit | grep exit; then \
 		echo 'libpq must not be calling any function which invokes exit'; exit 1; \
 	fi
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index ed2a4048d1..7e2017daf0 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -54,8 +54,9 @@ libpq_c_args = ['-DSO_MAJOR_VERSION=5']
 #    libpq_st, and {pgport,common}_shlib for libpq_sh
 #
 # We could try to avoid building the source files twice, but it probably adds
-# more complexity than its worth (reusing object files requires also linking
-# to the library on windows or breaks precompiled headers).
+# more complexity than its worth (AIX doesn't support link_whole yet, reusing
+# object files requires also linking to the library on windows or breaks
+# precompiled headers).
 libpq_st = static_library('libpq',
   libpq_sources,
   include_directories: [libpq_inc],
diff --git a/src/makefiles/Makefile.aix b/src/makefiles/Makefile.aix
new file mode 100644
index 0000000000..dd16a7a037
--- /dev/null
+++ b/src/makefiles/Makefile.aix
@@ -0,0 +1,39 @@
+# MAKE_EXPORTS is required for svr4 loaders that want a file of
+# symbol names to tell them what to export/import.
+MAKE_EXPORTS= true
+
+# -blibpath must contain ALL directories where we should look for libraries
+libpath := $(shell echo $(subst -L,:,$(filter -L/%,$(LDFLAGS))) | sed -e's/ //g'):/usr/lib:/lib
+
+# when building with gcc, need to make sure that libgcc can be found
+ifeq ($(GCC), yes)
+libpath := $(libpath):$(dir $(shell gcc -print-libgcc-file-name))
+endif
+
+rpath = -Wl,-blibpath:'$(rpathdir)$(libpath)'
+
+LDFLAGS_SL += -Wl,-bnoentry -Wl,-H512 -Wl,-bM:SRE
+
+# gcc needs to know it's building a shared lib, otherwise it'll not emit
+# correct code / link to the right support libraries
+ifeq ($(GCC), yes)
+LDFLAGS_SL += -shared
+endif
+
+# env var name to use in place of LD_LIBRARY_PATH
+ld_library_path_var = LIBPATH
+
+
+POSTGRES_IMP= postgres.imp
+
+ifdef PGXS
+BE_DLLLIBS= -Wl,-bI:$(pkglibdir)/$(POSTGRES_IMP)
+else
+BE_DLLLIBS= -Wl,-bI:$(top_builddir)/src/backend/$(POSTGRES_IMP)
+endif
+
+MKLDEXPORT_DIR=src/backend/port/aix
+MKLDEXPORT=$(top_srcdir)/$(MKLDEXPORT_DIR)/mkldexport.sh
+
+%$(DLSUFFIX): %.o
+	$(CC) $(CFLAGS) $*.o $(LDFLAGS) $(LDFLAGS_SL) -o $@ $(BE_DLLLIBS)
diff --git a/src/port/README b/src/port/README
index ed5c54a72f..97f18a6233 100644
--- a/src/port/README
+++ b/src/port/README
@@ -28,5 +28,5 @@ applications.
 from libpgport are linked first.  This avoids having applications
 dependent on symbols that are _used_ by libpq, but not intended to be
 exported by libpq.  libpq's libpgport usage changes over time, so such a
-dependency is a problem.  Windows, Linux, and macOS use an export
+dependency is a problem.  Windows, Linux, AIX, and macOS use an export
 list to control the symbols exported by libpq.
diff --git a/src/port/strerror.c b/src/port/strerror.c
index 4918ba821c..1070a49802 100644
--- a/src/port/strerror.c
+++ b/src/port/strerror.c
@@ -214,8 +214,10 @@ get_errno_symbol(int errnum)
 			return "ENOTCONN";
 		case ENOTDIR:
 			return "ENOTDIR";
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:
 			return "ENOTEMPTY";
+#endif
 		case ENOTSOCK:
 			return "ENOTSOCK";
 #ifdef ENOTSUP
diff --git a/src/template/aix b/src/template/aix
new file mode 100644
index 0000000000..903f8a8f8a
--- /dev/null
+++ b/src/template/aix
@@ -0,0 +1,26 @@
+# src/template/aix
+
+# Commenting for XLC
+# Set default options if using xlc.  This formerly included -qsrcmsg, but that
+# option elicits internal compiler errors from xlc v16.1.0.  Note: configure
+# will add -qnoansialias if the compiler accepts it, even if user specifies a
+# non-default CFLAGS setting.
+#if test "$GCC" != yes ; then
+#  case $host_os in
+#    *)
+#      CFLAGS="-O2 -qmaxmem=16384"
+#      ;;
+#  esac
+
+  # Due to a compiler bug, see 20171013023536.GA492146@rfd.leadboat.com for details,
+  # force restrict not to be used when compiling with xlc.
+#  FORCE_DISABLE_RESTRICT=yes
+#fi
+
+# Extra CFLAGS for code that will go into a shared library
+CFLAGS_SL=""
+
+# Native memset() is faster, tested on:
+# 	AIX 5.1 and 5.2, XLC 6.0 (IBM's cc)
+# 	AIX 5.3 ML3, gcc 4.0.1
+MEMSET_LOOP_LIMIT=0
diff --git a/src/test/regress/Makefile b/src/test/regress/Makefile
index 6409a485e8..7c665ff892 100644
--- a/src/test/regress/Makefile
+++ b/src/test/regress/Makefile
@@ -7,6 +7,11 @@
 # GNU make uses a make file named "GNUmakefile" in preference to "Makefile"
 # if it exists.  Postgres is shipped with a "GNUmakefile".
 
+
+# AIX make defaults to building *every* target of the first rule.  Start with
+# a single-target, empty rule to make the other targets non-default.
+all:
+
 all install clean check installcheck:
 	@echo "You must use GNU make to use Postgres.  It may be installed"
 	@echo "on your system with the name 'gmake'."
diff --git a/src/test/regress/expected/sanity_check.out b/src/test/regress/expected/sanity_check.out
index 8370c1561c..c5c675b750 100644
--- a/src/test/regress/expected/sanity_check.out
+++ b/src/test/regress/expected/sanity_check.out
@@ -25,3 +25,32 @@ SELECT relname, relkind
 ---------+---------
 (0 rows)
 
+--
+-- When ALIGNOF_DOUBLE==4 (e.g. AIX), the C ABI may impose 8-byte alignment on
+-- some of the C types that correspond to TYPALIGN_DOUBLE SQL types.  To ensure
+-- catalog C struct layout matches catalog tuple layout, arrange for the tuple
+-- offset of each fixed-width, attalign='d' catalog column to be divisible by 8
+-- unconditionally.  Keep such columns before the first NameData column of the
+-- catalog, since packagers can override NAMEDATALEN to an odd number.
+--
+WITH check_columns AS (
+ SELECT relname, attname,
+  array(
+   SELECT t.oid
+    FROM pg_type t JOIN pg_attribute pa ON t.oid = pa.atttypid
+    WHERE pa.attrelid = a.attrelid AND
+          pa.attnum > 0 AND pa.attnum < a.attnum
+    ORDER BY pa.attnum) AS coltypes
+ FROM pg_attribute a JOIN pg_class c ON c.oid = attrelid
+  JOIN pg_namespace n ON c.relnamespace = n.oid
+ WHERE attalign = 'd' AND relkind = 'r' AND
+  attnotnull AND attlen <> -1 AND n.nspname = 'pg_catalog'
+)
+SELECT relname, attname, coltypes, get_columns_length(coltypes)
+ FROM check_columns
+ WHERE get_columns_length(coltypes) % 8 != 0 OR
+       'name'::regtype::oid = ANY(coltypes);
+ relname | attname | coltypes | get_columns_length 
+---------+---------+----------+--------------------
+(0 rows)
+
diff --git a/src/test/regress/expected/test_setup.out b/src/test/regress/expected/test_setup.out
index 3d0eeec996..5d9e6bf12b 100644
--- a/src/test/regress/expected/test_setup.out
+++ b/src/test/regress/expected/test_setup.out
@@ -209,6 +209,10 @@ CREATE FUNCTION ttdummy ()
     RETURNS trigger
     AS :'regresslib'
     LANGUAGE C;
+CREATE FUNCTION get_columns_length(oid[])
+    RETURNS int
+    AS :'regresslib'
+    LANGUAGE C STRICT STABLE PARALLEL SAFE;
 -- Use hand-rolled hash functions and operator classes to get predictable
 -- result on different machines.  The hash function for int4 simply returns
 -- the sum of the values passed to it and the one for text returns the length
diff --git a/src/test/regress/regress.c b/src/test/regress/regress.c
index deffaea578..cc633864d7 100644
--- a/src/test/regress/regress.c
+++ b/src/test/regress/regress.c
@@ -1221,3 +1221,43 @@ binary_coercible(PG_FUNCTION_ARGS)
 
 	PG_RETURN_BOOL(IsBinaryCoercible(srctype, targettype));
 }
+
+/*
+ * Return the length of the portion of a tuple consisting of the given array
+ * of data types.  The input data types must be fixed-length data types.
+ */
+PG_FUNCTION_INFO_V1(get_columns_length);
+Datum
+get_columns_length(PG_FUNCTION_ARGS)
+{
+	ArrayType  *ta = PG_GETARG_ARRAYTYPE_P(0);
+	Oid		   *type_oids;
+	int			ntypes;
+	int			column_offset = 0;
+
+	if (ARR_HASNULL(ta) && array_contains_nulls(ta))
+		elog(ERROR, "argument must not contain nulls");
+
+	if (ARR_NDIM(ta) > 1)
+		elog(ERROR, "argument must be empty or one-dimensional array");
+
+	type_oids = (Oid *) ARR_DATA_PTR(ta);
+	ntypes = ArrayGetNItems(ARR_NDIM(ta), ARR_DIMS(ta));
+	for (int i = 0; i < ntypes; i++)
+	{
+		Oid			typeoid = type_oids[i];
+		int16		typlen;
+		bool		typbyval;
+		char		typalign;
+
+		get_typlenbyvalalign(typeoid, &typlen, &typbyval, &typalign);
+
+		/* the data type must be fixed-length */
+		if (typlen < 0)
+			elog(ERROR, "type %u is not fixed-length data type", typeoid);
+
+		column_offset = att_align_nominal(column_offset + typlen, typalign);
+	}
+
+	PG_RETURN_INT32(column_offset);
+}
diff --git a/src/test/regress/sql/sanity_check.sql b/src/test/regress/sql/sanity_check.sql
index 162e5324b5..7f338d191c 100644
--- a/src/test/regress/sql/sanity_check.sql
+++ b/src/test/regress/sql/sanity_check.sql
@@ -19,3 +19,29 @@ SELECT relname, relkind
   FROM pg_class
  WHERE relkind IN ('v', 'c', 'f', 'p', 'I')
        AND relfilenode <> 0;
+
+--
+-- When ALIGNOF_DOUBLE==4 (e.g. AIX), the C ABI may impose 8-byte alignment on
+-- some of the C types that correspond to TYPALIGN_DOUBLE SQL types.  To ensure
+-- catalog C struct layout matches catalog tuple layout, arrange for the tuple
+-- offset of each fixed-width, attalign='d' catalog column to be divisible by 8
+-- unconditionally.  Keep such columns before the first NameData column of the
+-- catalog, since packagers can override NAMEDATALEN to an odd number.
+--
+WITH check_columns AS (
+ SELECT relname, attname,
+  array(
+   SELECT t.oid
+    FROM pg_type t JOIN pg_attribute pa ON t.oid = pa.atttypid
+    WHERE pa.attrelid = a.attrelid AND
+          pa.attnum > 0 AND pa.attnum < a.attnum
+    ORDER BY pa.attnum) AS coltypes
+ FROM pg_attribute a JOIN pg_class c ON c.oid = attrelid
+  JOIN pg_namespace n ON c.relnamespace = n.oid
+ WHERE attalign = 'd' AND relkind = 'r' AND
+  attnotnull AND attlen <> -1 AND n.nspname = 'pg_catalog'
+)
+SELECT relname, attname, coltypes, get_columns_length(coltypes)
+ FROM check_columns
+ WHERE get_columns_length(coltypes) % 8 != 0 OR
+       'name'::regtype::oid = ANY(coltypes);
diff --git a/src/test/regress/sql/test_setup.sql b/src/test/regress/sql/test_setup.sql
index 06b0e2121f..1b2d434683 100644
--- a/src/test/regress/sql/test_setup.sql
+++ b/src/test/regress/sql/test_setup.sql
@@ -257,6 +257,11 @@ CREATE FUNCTION ttdummy ()
     AS :'regresslib'
     LANGUAGE C;
 
+CREATE FUNCTION get_columns_length(oid[])
+    RETURNS int
+    AS :'regresslib'
+    LANGUAGE C STRICT STABLE PARALLEL SAFE;
+
 -- Use hand-rolled hash functions and operator classes to get predictable
 -- result on different machines.  The hash function for int4 simply returns
 -- the sum of the values passed to it and the one for text returns the length
diff --git a/src/tools/gen_export.pl b/src/tools/gen_export.pl
index d9fdaaaf6d..888c8a197a 100644
--- a/src/tools/gen_export.pl
+++ b/src/tools/gen_export.pl
@@ -16,11 +16,12 @@ GetOptions(
 	'input:s' => \$input,
 	'output:s' => \$output) or die "wrong arguments";
 
-if (not(   $format eq 'darwin'
+if (not(   $format eq 'aix'
+		or $format eq 'darwin'
 		or $format eq 'gnu'
 		or $format eq 'win'))
 {
-	die "$0: $format is not yet handled (only darwin, gnu, win are)\n";
+	die "$0: $format is not yet handled (only aix, darwin, gnu, win are)\n";
 }
 
 open(my $input_handle, '<', $input)
@@ -55,7 +56,11 @@ while (<$input_handle>)
 	}
 	elsif (/^(\S+)\s+(\S+)/)
 	{
-		if ($format eq 'darwin')
+		if ($format eq 'aix')
+		{
+			print $output_handle "$1\n";
+		}
+		elsif ($format eq 'darwin')
 		{
 			print $output_handle "_$1\n";
 		}
diff --git a/src/tools/pginclude/headerscheck b/src/tools/pginclude/headerscheck
index 4a157d0a5f..cfd8c6896c 100755
--- a/src/tools/pginclude/headerscheck
+++ b/src/tools/pginclude/headerscheck
@@ -85,6 +85,7 @@ do
 
 	# These files are platform-specific, and c.h will include the
 	# one that's relevant for our current platform anyway.
+	test "$f" = src/include/port/aix.h && continue
 	test "$f" = src/include/port/cygwin.h && continue
 	test "$f" = src/include/port/darwin.h && continue
 	test "$f" = src/include/port/freebsd.h && continue
-- 
2.41.0

From 0d69a26fc1b52fb3e274176a83e7772b05bd7025 Mon Sep 17 00:00:00 2001
From: Sriram RK <sriram.rk@in.ibm.com>
Date: Tue, 13 Aug 2024 08:19:25 -0500
Subject: [PATCH] AIX support revert changes from 0b16bb8776bb. Review comments
 from Heikki

---
 configure                    | 17 ++---------------
 configure.ac                 |  5 +----
 src/include/port/aix.h       |  8 --------
 src/include/storage/s_lock.h |  6 ------
 src/template/aix             | 12 ------------
 5 files changed, 3 insertions(+), 45 deletions(-)

diff --git a/configure b/configure
index 03271f1861..f218b2e040 100755
--- a/configure
+++ b/configure
@@ -6849,12 +6849,6 @@ if test x"$pgac_cv_prog_CXX_cxxflags__fno_strict_aliasing" = x"yes"; then
   CXXFLAGS="${CXXFLAGS} -fno-strict-aliasing"
 fi
 
-
-elif test "$PORTNAME" = "aix"; then
-  # AIX's xlc has to have strict aliasing turned off too
-  # Igonoring the XLC falgs -qnoansialias, -qlonglong
-{ $as_echo_n "Running AIX gcc for now... " >&6; }
-
 fi
 
 # If the compiler knows how to hide symbols, add the switch needed for that to
@@ -7009,9 +7003,6 @@ if test x"$pgac_cv_prog_CXX_cxxflags__fvisibility_inlines_hidden" = x"yes"; then
 fi
 
   have_visibility_attribute=$pgac_cv_prog_CC_cflags__fvisibility_hidden
-elif test "$PORTNAME" = "aix"; then
-  # Note that xlc accepts -fvisibility=hidden as a file.
-  { $as_echo_n "Running AIX gcc for now... " >&6; }
 fi
 
 if test "$have_visibility_attribute" = "yes"; then
@@ -14728,10 +14719,6 @@ fi
 # spelling it understands, because it conflicts with
 # __declspec(restrict). Therefore we define pg_restrict to the
 # appropriate definition, which presumably won't conflict.
-#
-# Allow platforms with buggy compilers to force restrict to not be
-# used by setting $FORCE_DISABLE_RESTRICT=yes in the relevant
-# template.
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for C/C++ restrict keyword" >&5
 $as_echo_n "checking for C/C++ restrict keyword... " >&6; }
 if ${ac_cv_c_restrict+:} false; then :
@@ -14778,7 +14765,7 @@ _ACEOF
  ;;
  esac
 
-if test "$ac_cv_c_restrict" = "no" -o "x$FORCE_DISABLE_RESTRICT" = "xyes"; then
+if test "$ac_cv_c_restrict" = "no"; then
   pg_restrict=""
 else
   pg_restrict="$ac_cv_c_restrict"
@@ -17094,7 +17081,7 @@ else
 /* end confdefs.h.  */
 
 /* This must match the corresponding code in c.h: */
-#if defined(__GNUC__) || defined(__SUNPRO_C)
+#if defined(__GNUC__) || defined(__SUNPRO_C) || defined(__IBMC__)
 #define pg_attribute_aligned(a) __attribute__((aligned(a)))
 #elif defined(_MSC_VER)
 #define pg_attribute_aligned(a) __declspec(align(a))
diff --git a/configure.ac b/configure.ac
index 22069395a6..a059509cd9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1646,11 +1646,8 @@ PGAC_TYPE_LOCALE_T
 # __declspec(restrict). Therefore we define pg_restrict to the
 # appropriate definition, which presumably won't conflict.
 #
-# Allow platforms with buggy compilers to force restrict to not be
-# used by setting $FORCE_DISABLE_RESTRICT=yes in the relevant
-# template.
 AC_C_RESTRICT
-if test "$ac_cv_c_restrict" = "no" -o "x$FORCE_DISABLE_RESTRICT" = "xyes"; then
+if test "$ac_cv_c_restrict" = "no" ; then
   pg_restrict=""
 else
   pg_restrict="$ac_cv_c_restrict"
diff --git a/src/include/port/aix.h b/src/include/port/aix.h
index c54c95d4a5..1c2d166791 100644
--- a/src/include/port/aix.h
+++ b/src/include/port/aix.h
@@ -4,11 +4,3 @@
 #define CLASS_CONFLICT
 #define DISABLE_XOPEN_NLS
 
-/* Commenting for XLC
- * "IBM XL C/C++ for AIX, V12.1" miscompiles, for 32-bit, some inline
- * expansions of ginCompareItemPointers() "long long" arithmetic.  To take
- * advantage of inlining, build a 64-bit PostgreSQL.
-#if defined(__ILP32__) && defined(__IBMC__)
-#define PG_FORCE_DISABLE_INLINE
-#endif
- */
diff --git a/src/include/storage/s_lock.h b/src/include/storage/s_lock.h
index 69582f4ae7..2f6eb5df2a 100644
--- a/src/include/storage/s_lock.h
+++ b/src/include/storage/s_lock.h
@@ -414,12 +414,6 @@ typedef unsigned int slock_t;
  * an isync is a sufficient synchronization barrier after a lwarx/stwcx loop.
  * But if the spinlock is in ordinary memory, we can use lwsync instead for
  * better performance.
- *
- * Ordinarily, we'd code the branches here using GNU-style local symbols, that
- * is "1f" referencing "1:" and so on.  But some people run gcc on AIX with
- * IBM's assembler as backend, and IBM's assembler doesn't do local symbols.
- * So hand-code the branch offsets; fortunately, all PPC instructions are
- * exactly 4 bytes each, so it's not too hard to count.
  */
 static __inline__ int
 tas(volatile slock_t *lock)
diff --git a/src/template/aix b/src/template/aix
index 903f8a8f8a..0a788676c0 100644
--- a/src/template/aix
+++ b/src/template/aix
@@ -1,17 +1,5 @@
 # src/template/aix
 
-# Commenting for XLC
-# Set default options if using xlc.  This formerly included -qsrcmsg, but that
-# option elicits internal compiler errors from xlc v16.1.0.  Note: configure
-# will add -qnoansialias if the compiler accepts it, even if user specifies a
-# non-default CFLAGS setting.
-#if test "$GCC" != yes ; then
-#  case $host_os in
-#    *)
-#      CFLAGS="-O2 -qmaxmem=16384"
-#      ;;
-#  esac
-
   # Due to a compiler bug, see 20171013023536.GA492146@rfd.leadboat.com for details,
   # force restrict not to be used when compiling with xlc.
 #  FORCE_DISABLE_RESTRICT=yes
-- 
2.41.0

From 0ecf87244dea6530abed0d6f5172397e24fda922 Mon Sep 17 00:00:00 2001
From: Sriram RK <sriram.rk@in.ibm.com>
Date: Mon, 20 May 2024 01:38:59 -0500
Subject: [PATCH] AIX support, revert the changes from 0b16bb8776bb8. Trim
 AIX/XLC changes to support gcc only.

Review comments from Heikki.
---
 Makefile                                      |   2 -
 configure                                     |  37 +++---
 configure.ac                                  |  28 ++---
 doc/src/sgml/dfunc.sgml                       |  19 +++
 doc/src/sgml/installation.sgml                | 118 +++++++++++++++++-
 doc/src/sgml/runtime.sgml                     |  23 ++++
 meson.build                                   |  57 +++++----
 src/Makefile.shlib                            |  29 +++++
 src/backend/Makefile                          |  20 +++
 src/backend/meson.build                       |  15 +++
 src/backend/port/aix/mkldexport.sh            |  61 +++++++++
 src/backend/utils/error/elog.c                |   2 +
 src/backend/utils/misc/ps_status.c            |   4 +-
 src/bin/pg_basebackup/t/010_pg_basebackup.pl  |   3 +-
 src/bin/pg_verifybackup/t/008_untar.pl        |   3 +-
 src/bin/pg_verifybackup/t/010_client_untar.pl |   3 +-
 src/include/c.h                               |   4 +-
 src/include/port/aix.h                        |   6 +
 src/include/storage/s_lock.h                  |  25 +++-
 src/interfaces/libpq/Makefile                 |   2 +-
 src/interfaces/libpq/meson.build              |   5 +-
 src/makefiles/Makefile.aix                    |  39 ++++++
 src/port/README                               |   2 +-
 src/port/strerror.c                           |   2 +
 src/template/aix                              |  14 +++
 src/test/regress/Makefile                     |   5 +
 src/test/regress/expected/sanity_check.out    |  29 +++++
 src/test/regress/expected/test_setup.out      |   4 +
 src/test/regress/regress.c                    |  40 ++++++
 src/test/regress/sql/sanity_check.sql         |  26 ++++
 src/test/regress/sql/test_setup.sql           |   5 +
 src/tools/gen_export.pl                       |  11 +-
 src/tools/pginclude/headerscheck              |   1 +
 33 files changed, 555 insertions(+), 89 deletions(-)
 create mode 100755 src/backend/port/aix/mkldexport.sh
 create mode 100644 src/include/port/aix.h
 create mode 100644 src/makefiles/Makefile.aix
 create mode 100644 src/template/aix

diff --git a/Makefile b/Makefile
index 8a2ec9396b..9bc1a4ec17 100644
--- a/Makefile
+++ b/Makefile
@@ -13,8 +13,6 @@
 
 # AIX make defaults to building *every* target of the first rule.  Start with
 # a single-target, empty rule to make the other targets non-default.
-# (We don't support AIX anymore, but if someone tries to build on AIX anyway,
-# at least they'll get the instructions to run 'configure' first.)
 all:
 
 all check install installdirs installcheck installcheck-parallel uninstall clean distclean maintainer-clean dist distcheck world check-world install-world installcheck-world:
diff --git a/configure b/configure
index 89644f2249..f218b2e040 100755
--- a/configure
+++ b/configure
@@ -2988,6 +2988,7 @@ else
 # --with-template not given
 
 case $host_os in
+     aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -6848,7 +6849,6 @@ if test x"$pgac_cv_prog_CXX_cxxflags__fno_strict_aliasing" = x"yes"; then
   CXXFLAGS="${CXXFLAGS} -fno-strict-aliasing"
 fi
 
-
 fi
 
 # If the compiler knows how to hide symbols, add the switch needed for that to
@@ -12860,7 +12860,8 @@ fi
 
 fi
 
-# Note: We can test for libldap_r only after we know PTHREAD_LIBS
+# Note: We can test for libldap_r only after we know PTHREAD_LIBS;
+# also, on AIX, we may need to have openssl in LIBS for this step.
 if test "$with_ldap" = yes ; then
   _LIBS="$LIBS"
   if test "$PORTNAME" != "win32"; then
@@ -16951,28 +16952,18 @@ _ACEOF
 
 
 # Compute maximum alignment of any basic type.
-#
-# We require 'double' to have the strictest alignment among the basic types,
-# because otherwise the C ABI might impose 8-byte alignment on some of the
-# other C types that correspond to TYPALIGN_DOUBLE SQL types.  That could
-# cause a mismatch between the tuple layout and the C struct layout of a
-# catalog tuple.  We used to carefully order catalog columns such that any
-# fixed-width, attalign=4 columns were at offsets divisible by 8 regardless
-# of MAXIMUM_ALIGNOF to avoid that, but we no longer support any platforms
-# where TYPALIGN_DOUBLE != MAXIMUM_ALIGNOF.
-#
-# We assume without checking that long's alignment is at least as strong as
-# char, short, or int.  Note that we intentionally do not consider any types
-# wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
-# much of a penalty for disk and memory space.
-
-MAX_ALIGNOF=$ac_cv_alignof_double
+# We assume long's alignment is at least as strong as char, short, or int;
+# but we must check long long (if it is being used for int64) and double.
+# Note that we intentionally do not consider any types wider than 64 bits,
+# as allowing MAXIMUM_ALIGNOF to exceed 8 would be too much of a penalty
+# for disk and memory space.
 
-if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
+MAX_ALIGNOF=$ac_cv_alignof_long
+if test $MAX_ALIGNOF -lt $ac_cv_alignof_double ; then
+  MAX_ALIGNOF=$ac_cv_alignof_double
 fi
-if test x"$HAVE_LONG_LONG_INT_64" = xyes && test $ac_cv_alignof_long_long_int -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'long long int' is greater than the alignment of 'double'" "$LINENO" 5
+if test x"$HAVE_LONG_LONG_INT_64" = xyes && test $MAX_ALIGNOF -lt $ac_cv_alignof_long_long_int ; then
+  MAX_ALIGNOF="$ac_cv_alignof_long_long_int"
 fi
 
 cat >>confdefs.h <<_ACEOF
@@ -17090,7 +17081,7 @@ else
 /* end confdefs.h.  */
 
 /* This must match the corresponding code in c.h: */
-#if defined(__GNUC__) || defined(__SUNPRO_C)
+#if defined(__GNUC__) || defined(__SUNPRO_C) || defined(__IBMC__)
 #define pg_attribute_aligned(a) __attribute__((aligned(a)))
 #elif defined(_MSC_VER)
 #define pg_attribute_aligned(a) __declspec(align(a))
diff --git a/configure.ac b/configure.ac
index c7322e292c..a059509cd9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -62,6 +62,7 @@ PGAC_ARG_REQ(with, template, [NAME], [override operating system template],
 # --with-template not given
 
 case $host_os in
+     aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -1385,7 +1386,8 @@ if test "$with_zstd" = yes ; then
   AC_CHECK_LIB(zstd, ZSTD_compress, [], [AC_MSG_ERROR([library 'zstd' is required for ZSTD support])])
 fi
 
-# Note: We can test for libldap_r only after we know PTHREAD_LIBS
+# Note: We can test for libldap_r only after we know PTHREAD_LIBS;
+# also, on AIX, we may need to have openssl in LIBS for this step.
 if test "$with_ldap" = yes ; then
   _LIBS="$LIBS"
   if test "$PORTNAME" != "win32"; then
@@ -1643,8 +1645,9 @@ PGAC_TYPE_LOCALE_T
 # spelling it understands, because it conflicts with
 # __declspec(restrict). Therefore we define pg_restrict to the
 # appropriate definition, which presumably won't conflict.
+#
 AC_C_RESTRICT
-if test "$ac_cv_c_restrict" = "no"; then
+if test "$ac_cv_c_restrict" = "no" ; then
   pg_restrict=""
 else
   pg_restrict="$ac_cv_c_restrict"
@@ -1996,22 +1999,11 @@ fi
 AC_CHECK_ALIGNOF(double)
 
 # Compute maximum alignment of any basic type.
-#
-# We require 'double' to have the strictest alignment among the basic types,
-# because otherwise the C ABI might impose 8-byte alignment on some of the
-# other C types that correspond to TYPALIGN_DOUBLE SQL types.  That could
-# cause a mismatch between the tuple layout and the C struct layout of a
-# catalog tuple.  We used to carefully order catalog columns such that any
-# fixed-width, attalign=4 columns were at offsets divisible by 8 regardless
-# of MAXIMUM_ALIGNOF to avoid that, but we no longer support any platforms
-# where TYPALIGN_DOUBLE != MAXIMUM_ALIGNOF.
-#
-# We assume without checking that long's alignment is at least as strong as
-# char, short, or int.  Note that we intentionally do not consider any types
-# wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
-# much of a penalty for disk and memory space.
-
-MAX_ALIGNOF=$ac_cv_alignof_double
+# We assume long's alignment is at least as strong as char, short, or int;
+# but we must check long long (if it is being used for int64) and double.
+# Note that we intentionally do not consider any types wider than 64 bits,
+# as allowing MAXIMUM_ALIGNOF to exceed 8 would be too much of a penalty
+# for disk and memory space.
 
 if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
   AC_MSG_ERROR([alignment of 'long' is greater than the alignment of 'double'])
diff --git a/doc/src/sgml/dfunc.sgml b/doc/src/sgml/dfunc.sgml
index b94aefcd0c..554f9fac4c 100644
--- a/doc/src/sgml/dfunc.sgml
+++ b/doc/src/sgml/dfunc.sgml
@@ -202,4 +202,23 @@ gcc -G -o foo.so foo.o
   server expects to find the shared library files.
  </para>
 
+<!--
+Under AIX, object files are compiled normally but building the shared
+library requires a couple of steps.  First, create the object file:
+.nf
+cc <other flags> -c foo.c
+.fi
+You must then create a symbol \*(lqexports\*(rq file for the object
+file:
+.nf
+mkldexport foo.o `pwd` &gt; foo.exp
+.fi
+Finally, you can create the shared library:
+.nf
+ld <other flags> -H512 -T512 -o foo.so -e _nostart \e
+   -bI:.../lib/postgres.exp -bE:foo.exp foo.o \e
+   -lm -lc 2>/dev/null
+.fi
+  -->
+
 </sect2>
diff --git a/doc/src/sgml/installation.sgml b/doc/src/sgml/installation.sgml
index 1b32d5ca62..60e9a34a03 100644
--- a/doc/src/sgml/installation.sgml
+++ b/doc/src/sgml/installation.sgml
@@ -3401,7 +3401,7 @@ export MANPATH
   <para>
    <productname>PostgreSQL</productname> can be expected to work on current
    versions of these operating systems: Linux, Windows,
-   FreeBSD, OpenBSD, NetBSD, DragonFlyBSD, macOS, Solaris, and illumos.
+   FreeBSD, OpenBSD, NetBSD, DragonFlyBSD, macOS, AIX, Solaris, and illumos.
    Other Unix-like systems may also work but are not currently
    being tested.  In most cases, all CPU architectures supported by
    a given operating system will work.  Look in
@@ -3445,6 +3445,122 @@ export MANPATH
    installation issues.
   </para>
 
+  <sect2 id="installation-notes-aix">
+   <title>AIX</title>
+
+   <indexterm zone="installation-notes-aix">
+    <primary>AIX</primary>
+    <secondary>installation on</secondary>
+   </indexterm>
+
+   <para>
+    You can use GCC to build <productname>PostgreSQL</productname>
+    on <productname>AIX</productname>.
+   </para>
+
+   <para>
+    <productname>AIX</productname> versions before 7.1 are no longer
+    tested nor supported by the <productname>PostgreSQL</productname>
+    community.
+   </para>
+
+   <sect3 id="installation-notes-aix-mem-management">
+    <title>Memory Management</title>
+    <!-- https://archives.postgresql.org/message-id/603bgqmpl9.fsf@dba2.int.libertyrms.com -->
+
+    <para>
+     AIX can be somewhat peculiar with regards to the way it does
+     memory management.  You can have a server with many multiples of
+     gigabytes of RAM free, but still get out of memory or address
+     space errors when running applications.  One example
+     is loading of extensions failing with unusual errors.
+     For example, running as the owner of the PostgreSQL installation:
+<screen>
+=# CREATE EXTENSION plperl;
+ERROR:  could not load library "/opt/dbs/pgsql/lib/plperl.so": A memory address is not in the address space for the process.
+</screen>
+    Running as a non-owner in the group possessing the PostgreSQL
+    installation:
+<screen>
+=# CREATE EXTENSION plperl;
+ERROR:  could not load library "/opt/dbs/pgsql/lib/plperl.so": Bad address
+</screen>
+     Another example is out of memory errors in the PostgreSQL server
+     logs, with every memory allocation near or greater than 256 MB
+     failing.
+    </para>
+
+    <para>
+     The overall cause of all these problems is the default bittedness
+     and memory model used by the server process.  By default, all
+     binaries built on AIX are 32-bit.  This does not depend upon
+     hardware type or kernel in use.  These 32-bit processes are
+     limited to 4 GB of memory laid out in 256 MB segments using one
+     of a few models.  The default allows for less than 256 MB in the
+     heap as it shares a single segment with the stack.
+    </para>
+
+    <para>
+     In the case of the <literal>plperl</literal> example, above,
+     check your umask and the permissions of the binaries in your
+     PostgreSQL installation.  The binaries involved in that example
+     were 32-bit and installed as mode 750 instead of 755.  Due to the
+     permissions being set in this fashion, only the owner or a member
+     of the possessing group can load the library.  Since it isn't
+     world-readable, the loader places the object into the process'
+     heap instead of the shared library segments where it would
+     otherwise be placed.
+    </para>
+
+    <para>
+     The <quote>ideal</quote> solution for this is to use a 64-bit
+     build of PostgreSQL, but that is not always practical, because
+     systems with 32-bit processors can build, but not run, 64-bit
+     binaries.
+    </para>
+
+    <para>
+     If a 32-bit binary is desired, set <symbol>LDR_CNTRL</symbol> to
+     <literal>MAXDATA=0x<replaceable>n</replaceable>0000000</literal>,
+     where 1 &lt;= n &lt;= 8, before starting the PostgreSQL server,
+     and try different values and <filename>postgresql.conf</filename>
+     settings to find a configuration that works satisfactorily.  This
+     use of <symbol>LDR_CNTRL</symbol> tells AIX that you want the
+     server to have <symbol>MAXDATA</symbol> bytes set aside for the
+     heap, allocated in 256 MB segments.  When you find a workable
+     configuration,
+     <command>ldedit</command> can be used to modify the binaries so
+     that they default to using the desired heap size.  PostgreSQL can
+     also be rebuilt, passing <literal>configure
+     LDFLAGS="-Wl,-bmaxdata:0x<replaceable>n</replaceable>0000000"</literal>
+     to achieve the same effect.
+    </para>
+
+    <para>
+     For a 64-bit build, set <envar>OBJECT_MODE</envar> to 64 and
+     pass <literal>CC="gcc -maix64"</literal>
+     and <literal>LDFLAGS="-Wl,-bbigtoc"</literal>
+     to <command>configure</command>. 
+     If you omit the export of
+    <envar>OBJECT_MODE</envar>, your build may fail with linker errors.  When
+    <envar>OBJECT_MODE</envar> is set, it tells AIX's build utilities
+    such as <command>ar</command>, <command>as</command>, and <command>ld</command> what
+    type of objects to default to handling.
+    </para>
+
+    <para>
+     By default, overcommit of paging space can happen.  While we have
+     not seen this occur, AIX will kill processes when it runs out of
+     memory and the overcommit is accessed.  The closest to this that
+     we have seen is fork failing because the system decided that
+     there was not enough memory for another process.  Like many other
+     parts of AIX, the paging space allocation method and
+     out-of-memory kill is configurable on a system- or process-wide
+     basis if this becomes a problem.
+    </para>
+   </sect3>
+  </sect2>
+
   <sect2 id="installation-notes-cygwin">
    <title>Cygwin</title>
 
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index 6047b8171d..64753d9c01 100644
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -891,6 +891,29 @@ psql: error: connection to server on socket "/tmp/.s.PGSQL.5432" failed: No such
 
 
     <variablelist>
+     <varlistentry>
+      <term><systemitem class="osname">AIX</systemitem>
+      <indexterm><primary>AIX</primary><secondary>IPC configuration</secondary></indexterm>
+      </term>
+      <listitem>
+       <para>
+        It should not be necessary to do
+        any special configuration for such parameters as
+        <varname>SHMMAX</varname>, as it appears this is configured to
+        allow all memory to be used as shared memory.  That is the
+        sort of configuration commonly used for other databases such
+        as <application>DB/2</application>.</para>
+
+       <para> It might, however, be necessary to modify the global
+       <command>ulimit</command> information in
+       <filename>/etc/security/limits</filename>, as the default hard
+       limits for file sizes (<varname>fsize</varname>) and numbers of
+       files (<varname>nofiles</varname>) might be too low.
+       </para>
+      </listitem>
+     </varlistentry>
+
+
      <varlistentry>
       <term><systemitem class="osname">FreeBSD</systemitem>
       <indexterm><primary>FreeBSD</primary><secondary>IPC configuration</secondary></indexterm>
diff --git a/meson.build b/meson.build
index 1c0579d5a6..f1ac154cdc 100644
--- a/meson.build
+++ b/meson.build
@@ -196,7 +196,26 @@ endif
 # that purpose.
 portname = host_system
 
-if host_system == 'cygwin'
+if host_system == 'aix'
+  library_path_var = 'LIBPATH'
+
+  export_file_format = 'aix'
+  export_fmt = '-Wl,-bE:@0@'
+  mod_link_args_fmt = ['-Wl,-bI:@0@']
+  mod_link_with_dir = 'libdir'
+  mod_link_with_name = '@0@.imp'
+
+  # M:SRE sets a flag indicating that an object is a shared library. Seems to
+  # work in some circumstances without, but required in others.
+  ldflags_sl += '-Wl,-bM:SRE'
+  ldflags_be += '-Wl,-brtllib'
+
+  # Native memset() is faster, tested on:
+  # - AIX 5.1 and 5.2, XLC 6.0 (IBM's cc)
+  # - AIX 5.3 ML3, gcc 4.0.1
+  memset_loop_limit = 0
+
+elif host_system == 'cygwin'
   sema_kind = 'unnamed_posix'
   cppflags += '-D_GNU_SOURCE'
   dlsuffix = '.dll'
@@ -1490,11 +1509,11 @@ sizeof_long = cc.sizeof('long', args: test_c_args)
 cdata.set('SIZEOF_LONG', sizeof_long)
 if sizeof_long == 8
   cdata.set('HAVE_LONG_INT_64', 1)
-  pg_int64_type = 'long int'
+  cdata.set('PG_INT64_TYPE', 'long int')
   cdata.set_quoted('INT64_MODIFIER', 'l')
 elif sizeof_long == 4 and cc.sizeof('long long', args: test_c_args) == 8
   cdata.set('HAVE_LONG_LONG_INT_64', 1)
-  pg_int64_type = 'long long int'
+  cdata.set('PG_INT64_TYPE', 'long long int')
   cdata.set_quoted('INT64_MODIFIER', 'll')
 else
   error('do not know how to get a 64bit int')
@@ -1508,31 +1527,15 @@ endif
 # Determine memory alignment requirements for the basic C data types.
 
 alignof_types = ['short', 'int', 'long', 'double']
+maxalign = 0
 foreach t : alignof_types
   align = cc.alignment(t, args: test_c_args)
+  if maxalign < align
+    maxalign = align
+  endif
   cdata.set('ALIGNOF_@0@'.format(t.to_upper()), align)
 endforeach
-
-# Compute maximum alignment of any basic type.
-#
-# We require 'double' to have the strictest alignment among the basic types,
-# because otherwise the C ABI might impose 8-byte alignment on some of the
-# other C types that correspond to TYPALIGN_DOUBLE SQL types.  That could
-# cause a mismatch between the tuple layout and the C struct layout of a
-# catalog tuple.  We used to carefully order catalog columns such that any
-# fixed-width, attalign=4 columns were at offsets divisible by 8 regardless
-# of MAXIMUM_ALIGNOF to avoid that, but we no longer support any platforms
-# where TYPALIGN_DOUBLE != MAXIMUM_ALIGNOF.
-#
-# We assume without checking that int64's alignment is at least as strong
-# as long, char, short, or int.  Note that we intentionally do not consider
-# any types wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8
-# would be too much of a penalty for disk and memory space.
-alignof_double = cdata.get('ALIGNOF_DOUBLE')
-if cc.alignment(pg_int64_type, args: test_c_args) > alignof_double
-  error('alignment of int64 is greater than the alignment of double')
-endif
-cdata.set('MAXIMUM_ALIGNOF', alignof_double)
+cdata.set('MAXIMUM_ALIGNOF', maxalign)
 
 cdata.set('SIZEOF_VOID_P', cc.sizeof('void *', args: test_c_args))
 cdata.set('SIZEOF_SIZE_T', cc.sizeof('size_t', args: test_c_args))
@@ -1581,7 +1584,7 @@ if cc.links('''
   if not meson.is_cross_build()
     r = cc.run('''
     /* This must match the corresponding code in c.h: */
-    #if defined(__GNUC__) || defined(__SUNPRO_C)
+    #if defined(__GNUC__) || defined(__SUNPRO_C) || defined(__IBMC__)
     #define pg_attribute_aligned(a) __attribute__((aligned(a)))
     #elif defined(_MSC_VER)
     #define pg_attribute_aligned(a) __declspec(align(a))
@@ -2476,6 +2479,10 @@ endif
 # conflict.
 #
 # We assume C99 support, so we don't need to make this conditional.
+#
+# XXX: Historically we allowed platforms to disable restrict in template
+# files, but that was only added for AIX when building with XLC, which we
+# don't support yet.
 cdata.set('pg_restrict', '__restrict')
 
 
diff --git a/src/Makefile.shlib b/src/Makefile.shlib
index fa81f6ffdd..8ca51ca03f 100644
--- a/src/Makefile.shlib
+++ b/src/Makefile.shlib
@@ -106,6 +106,20 @@ ifdef SO_MAJOR_VERSION
 override CPPFLAGS += -DSO_MAJOR_VERSION=$(SO_MAJOR_VERSION)
 endif
 
+ifeq ($(PORTNAME), aix)
+  LINK.shared		= $(COMPILER)
+  ifdef SO_MAJOR_VERSION
+    shlib		= lib$(NAME)$(DLSUFFIX).$(SO_MAJOR_VERSION)
+  endif
+  haslibarule   = yes
+  # $(exports_file) is also usable as an import file
+  exports_file		= lib$(NAME).exp
+  BUILD.exports		= ( echo '\#! $(shlib)'; $(AWK) '/^[^\#]/ {printf "%s\n",$$1}' $< ) > $@
+  ifneq (,$(SHLIB_EXPORTS))
+    LINK.shared		+= -Wl,-bE:$(exports_file)
+  endif
+endif
+
 ifeq ($(PORTNAME), darwin)
   ifdef soname
     # linkable library
@@ -254,6 +268,14 @@ $(stlib): $(OBJS) | $(SHLIB_PREREQS)
 	touch $@
 endif #haslibarule
 
+# AIX wraps shared libraries inside a static library, can be used both
+# for static and shared linking
+ifeq ($(PORTNAME), aix)
+$(stlib): $(shlib)
+	rm -f $(stlib)
+	$(AR) $(AROPT) $(stlib) $(shlib)
+endif # aix
+
 ifeq (,$(filter cygwin win32,$(PORTNAME)))
 
 # Normal case
@@ -267,8 +289,11 @@ ifneq ($(shlib), $(shlib_major))
 endif
 # Make sure we have a link to a name without any version numbers
 ifneq ($(shlib), $(shlib_bare))
+# except on AIX, where that's not a thing
+ifneq ($(PORTNAME), aix)
 	rm -f $(shlib_bare)
 	$(LN_S) $(shlib) $(shlib_bare)
+endif # aix
 endif # shlib_bare
 endif # shlib_major
 
@@ -376,6 +401,9 @@ install-lib-static: $(stlib) installdirs-lib
 
 install-lib-shared: $(shlib) installdirs-lib
 ifdef soname
+# we don't install $(shlib) on AIX
+# (see http://archives.postgresql.org/message-id/52EF20B2E3209443BC37736D00C3C1380A6E79FE@EXADV1.host.magwien.gv.at)
+ifneq ($(PORTNAME), aix)
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(libdir)/$(shlib)'
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
@@ -391,6 +419,7 @@ ifneq ($(shlib), $(shlib_bare))
 endif
 endif # not win32
 endif # not cygwin
+endif # not aix
 ifneq (,$(findstring $(PORTNAME),win32 cygwin))
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(bindir)/$(shlib)'
 endif
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 6700aec039..954b14962f 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -62,12 +62,14 @@ all: submake-libpgport submake-catalog-headers submake-utils-headers postgres $(
 
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
+ifneq ($(PORTNAME), aix)
 
 postgres: $(OBJS)
 	$(CC) $(CFLAGS) $(call expand_subsys,$^) $(LDFLAGS) $(LIBS) -o $@
 
 endif
 endif
+endif
 
 ifeq ($(PORTNAME), cygwin)
 
@@ -94,6 +96,24 @@ libpostgres.a: postgres
 
 endif # win32
 
+ifeq ($(PORTNAME), aix)
+
+postgres: $(POSTGRES_IMP)
+	$(CC) $(CFLAGS) $(call expand_subsys,$(OBJS)) $(LDFLAGS) -Wl,-bE:$(top_builddir)/src/backend/$(POSTGRES_IMP) $(LIBS) -Wl,-brtllib -o $@
+
+# Linking to a single .o with -r is a lot faster than building a .a or passing
+# all objects to MKLDEXPORT.
+#
+# It looks alluring to use $(CC) -r instead of ld -r, but that doesn't
+# trivially work with gcc, due to gcc specific static libraries linked in with
+# -r.
+$(POSTGRES_IMP): $(OBJS)
+	ld -r -o SUBSYS.o $(call expand_subsys,$^)
+	$(MKLDEXPORT) SUBSYS.o . > $@
+	@rm -f SUBSYS.o
+
+endif # aix
+
 $(top_builddir)/src/port/libpgport_srv.a: | submake-libpgport
 
 
diff --git a/src/backend/meson.build b/src/backend/meson.build
index 436c04af08..8767aaba67 100644
--- a/src/backend/meson.build
+++ b/src/backend/meson.build
@@ -91,6 +91,21 @@ if cc.get_id() == 'msvc'
   # be restricted to b_pch=true.
   backend_link_with += postgres_lib
 
+elif host_system == 'aix'
+  # The '.' argument leads mkldexport.sh to emit "#! .", which refers to the
+  # main executable, allowing extension libraries to resolve their undefined
+  # symbols to symbols in the postgres binary.
+  postgres_imp = custom_target('postgres.imp',
+    command: [files('port/aix/mkldexport.sh'), '@INPUT@', '.'],
+    input: postgres_lib,
+    output: 'postgres.imp',
+    capture: true,
+    install: true,
+    install_dir: dir_lib,
+    build_by_default: false,
+  )
+  backend_link_args += '-Wl,-bE:@0@'.format(postgres_imp.full_path())
+  backend_link_depends += postgres_imp
 endif
 
 backend_input = []
diff --git a/src/backend/port/aix/mkldexport.sh b/src/backend/port/aix/mkldexport.sh
new file mode 100755
index 0000000000..adf3793e86
--- /dev/null
+++ b/src/backend/port/aix/mkldexport.sh
@@ -0,0 +1,61 @@
+#!/bin/sh
+#
+# mkldexport
+#	create an AIX exports file from an object file
+#
+# src/backend/port/aix/mkldexport.sh
+#
+# Usage:
+#	mkldexport objectfile [location]
+# where
+#	objectfile is the current location of the object file.
+#	location is the eventual (installed) location of the
+#		object file (if different from the current
+#		working directory).
+#
+# [This file comes from the Postgres 4.2 distribution. - ay 7/95]
+#
+# Header: /usr/local/devel/postgres/src/tools/mkldexport/RCS/mkldexport.sh,v 1.2 1994/03/13 04:59:12 aoki Exp
+#
+
+# setting this to nm -B might be better
+# ... due to changes in AIX 4.x ...
+# ... let us search in different directories - Gerhard Reithofer
+if [ -x /usr/ucb/nm ]
+then NM=/usr/ucb/nm
+elif [ -x /usr/bin/nm ]
+then NM=/usr/bin/nm
+elif [ -x /usr/ccs/bin/nm ]
+then NM=/usr/ccs/bin/nm
+elif [ -x /usr/usg/bin/nm ]
+then NM=/usr/usg/bin/nm
+else echo "Fatal error: cannot find `nm' ... please check your installation."
+     exit 1
+fi
+
+CMDNAME=`basename $0`
+if [ -z "$1" ]; then
+	echo "Usage: $CMDNAME object [location]"
+	exit 1
+fi
+OBJNAME=`basename $1`
+if [ "`basename $OBJNAME`" != "`basename $OBJNAME .o`" ]; then
+	OBJNAME=`basename $OBJNAME .o`.so
+fi
+if [ -z "$2" ]; then
+	echo '#!'
+else
+	if [ "$2" = "." ]; then
+		# for the base executable (AIX 4.2 and up)
+		echo '#! .'
+	else
+		echo '#!' $2
+	fi
+fi
+$NM -BCg $1 | \
+	egrep ' [TDB] ' | \
+	sed -e 's/.* //' | \
+	egrep -v '\$' | \
+	sed -e 's/^[.]//' | \
+	sort | \
+	uniq
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index d91a85cb2d..7b51e94f4a 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -908,7 +908,9 @@ errcode_for_file_access(void)
 			/* Wrong object type or state */
 		case ENOTDIR:			/* Not a directory */
 		case EISDIR:			/* Is a directory */
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:			/* Directory not empty */
+#endif
 			edata->sqlerrcode = ERRCODE_WRONG_OBJECT_TYPE;
 			break;
 
diff --git a/src/backend/utils/misc/ps_status.c b/src/backend/utils/misc/ps_status.c
index 9da6377402..532eac31b4 100644
--- a/src/backend/utils/misc/ps_status.c
+++ b/src/backend/utils/misc/ps_status.c
@@ -50,7 +50,7 @@ bool		update_process_title = DEFAULT_UPDATE_PROCESS_TITLE;
 #define PS_USE_SETPROCTITLE_FAST
 #elif defined(HAVE_SETPROCTITLE)
 #define PS_USE_SETPROCTITLE
-#elif defined(__linux__) || defined(__sun) || defined(__darwin__)
+#elif defined(__linux__) || defined(_AIX) || defined(__sun) || defined(__darwin__)
 #define PS_USE_CLOBBER_ARGV
 #elif defined(WIN32)
 #define PS_USE_WIN32
@@ -60,7 +60,7 @@ bool		update_process_title = DEFAULT_UPDATE_PROCESS_TITLE;
 
 
 /* Different systems want the buffer padded differently */
-#if defined(__linux__) || defined(__darwin__)
+#if defined(_AIX) || defined(__linux__) || defined(__darwin__)
 #define PS_PADDING '\0'
 #else
 #define PS_PADDING ' '
diff --git a/src/bin/pg_basebackup/t/010_pg_basebackup.pl b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
index 2d4b75a6fe..ce936959c1 100644
--- a/src/bin/pg_basebackup/t/010_pg_basebackup.pl
+++ b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
@@ -401,7 +401,8 @@ SKIP:
 {
 	my $tar = $ENV{TAR};
 	# don't check for a working tar here, to accommodate various odd
-	# cases. If tar doesn't work the init_from_backup below will fail.
+	# cases such as AIX. If tar doesn't work the init_from_backup below
+	# will fail.
 	skip "no tar program available", 1
 	  if (!defined $tar || $tar eq '');
 
diff --git a/src/bin/pg_verifybackup/t/008_untar.pl b/src/bin/pg_verifybackup/t/008_untar.pl
index 7a09f3b75b..30d9f3f7f0 100644
--- a/src/bin/pg_verifybackup/t/008_untar.pl
+++ b/src/bin/pg_verifybackup/t/008_untar.pl
@@ -104,7 +104,8 @@ for my $tc (@test_configuration)
 		{
 			my $tar = $ENV{TAR};
 			# don't check for a working tar here, to accommodate various odd
-			# cases. If tar doesn't work the init_from_backup below will fail.
+			# cases such as AIX. If tar doesn't work the init_from_backup below
+			# will fail.
 			skip "no tar program available", 1
 			  if (!defined $tar || $tar eq '');
 
diff --git a/src/bin/pg_verifybackup/t/010_client_untar.pl b/src/bin/pg_verifybackup/t/010_client_untar.pl
index 8c076d46de..45010d79ac 100644
--- a/src/bin/pg_verifybackup/t/010_client_untar.pl
+++ b/src/bin/pg_verifybackup/t/010_client_untar.pl
@@ -134,7 +134,8 @@ for my $tc (@test_configuration)
 		{
 			my $tar = $ENV{TAR};
 			# don't check for a working tar here, to accommodate various odd
-			# cases. If tar doesn't work the init_from_backup below will fail.
+			# cases such as AIX. If tar doesn't work the init_from_backup below
+			# will fail.
 			skip "no tar program available", 1
 			  if (!defined $tar || $tar eq '');
 
diff --git a/src/include/c.h b/src/include/c.h
index dc1841346c..641cd9bdf1 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -182,7 +182,7 @@
 #define PG_USED_FOR_ASSERTS_ONLY pg_attribute_unused()
 #endif
 
-/* GCC supports format attributes */
+/* GCC support format attributes */
 #if defined(__GNUC__)
 #define pg_attribute_format_arg(a) __attribute__((format_arg(a)))
 #define pg_attribute_printf(f,a) __attribute__((format(PG_PRINTF_ATTRIBUTE, f, a)))
@@ -192,7 +192,7 @@
 #endif
 
 /* GCC and Sunpro support aligned, packed and noreturn */
-#if defined(__GNUC__) || defined(__SUNPRO_C)
+#if defined(__GNUC__) || defined(__SUNPRO_C) 
 #define pg_attribute_aligned(a) __attribute__((aligned(a)))
 #define pg_attribute_noreturn() __attribute__((noreturn))
 #define pg_attribute_packed() __attribute__((packed))
diff --git a/src/include/port/aix.h b/src/include/port/aix.h
new file mode 100644
index 0000000000..1c2d166791
--- /dev/null
+++ b/src/include/port/aix.h
@@ -0,0 +1,6 @@
+/*
+ * src/include/port/aix.h
+ */
+#define CLASS_CONFLICT
+#define DISABLE_XOPEN_NLS
+
diff --git a/src/include/storage/s_lock.h b/src/include/storage/s_lock.h
index 29ac6cdcd9..2f6eb5df2a 100644
--- a/src/include/storage/s_lock.h
+++ b/src/include/storage/s_lock.h
@@ -424,17 +424,15 @@ tas(volatile slock_t *lock)
 	__asm__ __volatile__(
 "	lwarx   %0,0,%3,1	\n"
 "	cmpwi   %0,0		\n"
-"	bne     1f			\n"
+"	bne     $+16		\n"		/* branch to li %1,1 */
 "	addi    %0,%0,1		\n"
 "	stwcx.  %0,0,%3		\n"
-"	beq     2f			\n"
-"1: \n"
+"	beq     $+12		\n"		/* branch to lwsync */
 "	li      %1,1		\n"
-"	b       3f			\n"
-"2: \n"
+"	b       $+12		\n"		/* branch to end of asm sequence */
 "	lwsync				\n"
 "	li      %1,0		\n"
-"3: \n"
+
 :	"=&b"(_t), "=r"(_res), "+m"(*lock)
 :	"r"(lock)
 :	"memory", "cc");
@@ -662,6 +660,21 @@ tas(volatile slock_t *lock)
 
 #if !defined(HAS_TEST_AND_SET)	/* We didn't trigger above, let's try here */
 
+#if defined(_AIX)	/* AIX */
+/*
+ * AIX (POWER)
+ */
+#define HAS_TEST_AND_SET
+
+#include <sys/atomic_op.h>
+
+typedef int slock_t;
+
+#define TAS(lock)			_check_lock((slock_t *) (lock), 0, 1)
+#define S_UNLOCK(lock)		_clear_lock((slock_t *) (lock), 0)
+#endif	 /* _AIX */
+
+
 /* These are in sunstudio_(sparc|x86).s */
 
 #if defined(__SUNPRO_C) && (defined(__i386) || defined(__x86_64__) || defined(__sparc__) || defined(__sparc))
diff --git a/src/interfaces/libpq/Makefile b/src/interfaces/libpq/Makefile
index b36a765764..154429d4d1 100644
--- a/src/interfaces/libpq/Makefile
+++ b/src/interfaces/libpq/Makefile
@@ -114,7 +114,7 @@ backend_src = $(top_srcdir)/src/backend
 # coding rule.
 libpq-refs-stamp: $(shlib)
 ifneq ($(enable_coverage), yes)
-ifeq (,$(filter solaris,$(PORTNAME)))
+ifeq (,$(filter aix solaris,$(PORTNAME)))
 	@if nm -A -u $< 2>/dev/null | grep -v -e __cxa_atexit -e __tsan_func_exit | grep exit; then \
 		echo 'libpq must not be calling any function which invokes exit'; exit 1; \
 	fi
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index ed2a4048d1..7e2017daf0 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -54,8 +54,9 @@ libpq_c_args = ['-DSO_MAJOR_VERSION=5']
 #    libpq_st, and {pgport,common}_shlib for libpq_sh
 #
 # We could try to avoid building the source files twice, but it probably adds
-# more complexity than its worth (reusing object files requires also linking
-# to the library on windows or breaks precompiled headers).
+# more complexity than its worth (AIX doesn't support link_whole yet, reusing
+# object files requires also linking to the library on windows or breaks
+# precompiled headers).
 libpq_st = static_library('libpq',
   libpq_sources,
   include_directories: [libpq_inc],
diff --git a/src/makefiles/Makefile.aix b/src/makefiles/Makefile.aix
new file mode 100644
index 0000000000..dd16a7a037
--- /dev/null
+++ b/src/makefiles/Makefile.aix
@@ -0,0 +1,39 @@
+# MAKE_EXPORTS is required for svr4 loaders that want a file of
+# symbol names to tell them what to export/import.
+MAKE_EXPORTS= true
+
+# -blibpath must contain ALL directories where we should look for libraries
+libpath := $(shell echo $(subst -L,:,$(filter -L/%,$(LDFLAGS))) | sed -e's/ //g'):/usr/lib:/lib
+
+# when building with gcc, need to make sure that libgcc can be found
+ifeq ($(GCC), yes)
+libpath := $(libpath):$(dir $(shell gcc -print-libgcc-file-name))
+endif
+
+rpath = -Wl,-blibpath:'$(rpathdir)$(libpath)'
+
+LDFLAGS_SL += -Wl,-bnoentry -Wl,-H512 -Wl,-bM:SRE
+
+# gcc needs to know it's building a shared lib, otherwise it'll not emit
+# correct code / link to the right support libraries
+ifeq ($(GCC), yes)
+LDFLAGS_SL += -shared
+endif
+
+# env var name to use in place of LD_LIBRARY_PATH
+ld_library_path_var = LIBPATH
+
+
+POSTGRES_IMP= postgres.imp
+
+ifdef PGXS
+BE_DLLLIBS= -Wl,-bI:$(pkglibdir)/$(POSTGRES_IMP)
+else
+BE_DLLLIBS= -Wl,-bI:$(top_builddir)/src/backend/$(POSTGRES_IMP)
+endif
+
+MKLDEXPORT_DIR=src/backend/port/aix
+MKLDEXPORT=$(top_srcdir)/$(MKLDEXPORT_DIR)/mkldexport.sh
+
+%$(DLSUFFIX): %.o
+	$(CC) $(CFLAGS) $*.o $(LDFLAGS) $(LDFLAGS_SL) -o $@ $(BE_DLLLIBS)
diff --git a/src/port/README b/src/port/README
index ed5c54a72f..97f18a6233 100644
--- a/src/port/README
+++ b/src/port/README
@@ -28,5 +28,5 @@ applications.
 from libpgport are linked first.  This avoids having applications
 dependent on symbols that are _used_ by libpq, but not intended to be
 exported by libpq.  libpq's libpgport usage changes over time, so such a
-dependency is a problem.  Windows, Linux, and macOS use an export
+dependency is a problem.  Windows, Linux, AIX, and macOS use an export
 list to control the symbols exported by libpq.
diff --git a/src/port/strerror.c b/src/port/strerror.c
index 4918ba821c..1070a49802 100644
--- a/src/port/strerror.c
+++ b/src/port/strerror.c
@@ -214,8 +214,10 @@ get_errno_symbol(int errnum)
 			return "ENOTCONN";
 		case ENOTDIR:
 			return "ENOTDIR";
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:
 			return "ENOTEMPTY";
+#endif
 		case ENOTSOCK:
 			return "ENOTSOCK";
 #ifdef ENOTSUP
diff --git a/src/template/aix b/src/template/aix
new file mode 100644
index 0000000000..0a788676c0
--- /dev/null
+++ b/src/template/aix
@@ -0,0 +1,14 @@
+# src/template/aix
+
+  # Due to a compiler bug, see 20171013023536.GA492146@rfd.leadboat.com for details,
+  # force restrict not to be used when compiling with xlc.
+#  FORCE_DISABLE_RESTRICT=yes
+#fi
+
+# Extra CFLAGS for code that will go into a shared library
+CFLAGS_SL=""
+
+# Native memset() is faster, tested on:
+# 	AIX 5.1 and 5.2, XLC 6.0 (IBM's cc)
+# 	AIX 5.3 ML3, gcc 4.0.1
+MEMSET_LOOP_LIMIT=0
diff --git a/src/test/regress/Makefile b/src/test/regress/Makefile
index 6409a485e8..7c665ff892 100644
--- a/src/test/regress/Makefile
+++ b/src/test/regress/Makefile
@@ -7,6 +7,11 @@
 # GNU make uses a make file named "GNUmakefile" in preference to "Makefile"
 # if it exists.  Postgres is shipped with a "GNUmakefile".
 
+
+# AIX make defaults to building *every* target of the first rule.  Start with
+# a single-target, empty rule to make the other targets non-default.
+all:
+
 all install clean check installcheck:
 	@echo "You must use GNU make to use Postgres.  It may be installed"
 	@echo "on your system with the name 'gmake'."
diff --git a/src/test/regress/expected/sanity_check.out b/src/test/regress/expected/sanity_check.out
index 8370c1561c..c5c675b750 100644
--- a/src/test/regress/expected/sanity_check.out
+++ b/src/test/regress/expected/sanity_check.out
@@ -25,3 +25,32 @@ SELECT relname, relkind
 ---------+---------
 (0 rows)
 
+--
+-- When ALIGNOF_DOUBLE==4 (e.g. AIX), the C ABI may impose 8-byte alignment on
+-- some of the C types that correspond to TYPALIGN_DOUBLE SQL types.  To ensure
+-- catalog C struct layout matches catalog tuple layout, arrange for the tuple
+-- offset of each fixed-width, attalign='d' catalog column to be divisible by 8
+-- unconditionally.  Keep such columns before the first NameData column of the
+-- catalog, since packagers can override NAMEDATALEN to an odd number.
+--
+WITH check_columns AS (
+ SELECT relname, attname,
+  array(
+   SELECT t.oid
+    FROM pg_type t JOIN pg_attribute pa ON t.oid = pa.atttypid
+    WHERE pa.attrelid = a.attrelid AND
+          pa.attnum > 0 AND pa.attnum < a.attnum
+    ORDER BY pa.attnum) AS coltypes
+ FROM pg_attribute a JOIN pg_class c ON c.oid = attrelid
+  JOIN pg_namespace n ON c.relnamespace = n.oid
+ WHERE attalign = 'd' AND relkind = 'r' AND
+  attnotnull AND attlen <> -1 AND n.nspname = 'pg_catalog'
+)
+SELECT relname, attname, coltypes, get_columns_length(coltypes)
+ FROM check_columns
+ WHERE get_columns_length(coltypes) % 8 != 0 OR
+       'name'::regtype::oid = ANY(coltypes);
+ relname | attname | coltypes | get_columns_length 
+---------+---------+----------+--------------------
+(0 rows)
+
diff --git a/src/test/regress/expected/test_setup.out b/src/test/regress/expected/test_setup.out
index 3d0eeec996..5d9e6bf12b 100644
--- a/src/test/regress/expected/test_setup.out
+++ b/src/test/regress/expected/test_setup.out
@@ -209,6 +209,10 @@ CREATE FUNCTION ttdummy ()
     RETURNS trigger
     AS :'regresslib'
     LANGUAGE C;
+CREATE FUNCTION get_columns_length(oid[])
+    RETURNS int
+    AS :'regresslib'
+    LANGUAGE C STRICT STABLE PARALLEL SAFE;
 -- Use hand-rolled hash functions and operator classes to get predictable
 -- result on different machines.  The hash function for int4 simply returns
 -- the sum of the values passed to it and the one for text returns the length
diff --git a/src/test/regress/regress.c b/src/test/regress/regress.c
index deffaea578..cc633864d7 100644
--- a/src/test/regress/regress.c
+++ b/src/test/regress/regress.c
@@ -1221,3 +1221,43 @@ binary_coercible(PG_FUNCTION_ARGS)
 
 	PG_RETURN_BOOL(IsBinaryCoercible(srctype, targettype));
 }
+
+/*
+ * Return the length of the portion of a tuple consisting of the given array
+ * of data types.  The input data types must be fixed-length data types.
+ */
+PG_FUNCTION_INFO_V1(get_columns_length);
+Datum
+get_columns_length(PG_FUNCTION_ARGS)
+{
+	ArrayType  *ta = PG_GETARG_ARRAYTYPE_P(0);
+	Oid		   *type_oids;
+	int			ntypes;
+	int			column_offset = 0;
+
+	if (ARR_HASNULL(ta) && array_contains_nulls(ta))
+		elog(ERROR, "argument must not contain nulls");
+
+	if (ARR_NDIM(ta) > 1)
+		elog(ERROR, "argument must be empty or one-dimensional array");
+
+	type_oids = (Oid *) ARR_DATA_PTR(ta);
+	ntypes = ArrayGetNItems(ARR_NDIM(ta), ARR_DIMS(ta));
+	for (int i = 0; i < ntypes; i++)
+	{
+		Oid			typeoid = type_oids[i];
+		int16		typlen;
+		bool		typbyval;
+		char		typalign;
+
+		get_typlenbyvalalign(typeoid, &typlen, &typbyval, &typalign);
+
+		/* the data type must be fixed-length */
+		if (typlen < 0)
+			elog(ERROR, "type %u is not fixed-length data type", typeoid);
+
+		column_offset = att_align_nominal(column_offset + typlen, typalign);
+	}
+
+	PG_RETURN_INT32(column_offset);
+}
diff --git a/src/test/regress/sql/sanity_check.sql b/src/test/regress/sql/sanity_check.sql
index 162e5324b5..7f338d191c 100644
--- a/src/test/regress/sql/sanity_check.sql
+++ b/src/test/regress/sql/sanity_check.sql
@@ -19,3 +19,29 @@ SELECT relname, relkind
   FROM pg_class
  WHERE relkind IN ('v', 'c', 'f', 'p', 'I')
        AND relfilenode <> 0;
+
+--
+-- When ALIGNOF_DOUBLE==4 (e.g. AIX), the C ABI may impose 8-byte alignment on
+-- some of the C types that correspond to TYPALIGN_DOUBLE SQL types.  To ensure
+-- catalog C struct layout matches catalog tuple layout, arrange for the tuple
+-- offset of each fixed-width, attalign='d' catalog column to be divisible by 8
+-- unconditionally.  Keep such columns before the first NameData column of the
+-- catalog, since packagers can override NAMEDATALEN to an odd number.
+--
+WITH check_columns AS (
+ SELECT relname, attname,
+  array(
+   SELECT t.oid
+    FROM pg_type t JOIN pg_attribute pa ON t.oid = pa.atttypid
+    WHERE pa.attrelid = a.attrelid AND
+          pa.attnum > 0 AND pa.attnum < a.attnum
+    ORDER BY pa.attnum) AS coltypes
+ FROM pg_attribute a JOIN pg_class c ON c.oid = attrelid
+  JOIN pg_namespace n ON c.relnamespace = n.oid
+ WHERE attalign = 'd' AND relkind = 'r' AND
+  attnotnull AND attlen <> -1 AND n.nspname = 'pg_catalog'
+)
+SELECT relname, attname, coltypes, get_columns_length(coltypes)
+ FROM check_columns
+ WHERE get_columns_length(coltypes) % 8 != 0 OR
+       'name'::regtype::oid = ANY(coltypes);
diff --git a/src/test/regress/sql/test_setup.sql b/src/test/regress/sql/test_setup.sql
index 06b0e2121f..1b2d434683 100644
--- a/src/test/regress/sql/test_setup.sql
+++ b/src/test/regress/sql/test_setup.sql
@@ -257,6 +257,11 @@ CREATE FUNCTION ttdummy ()
     AS :'regresslib'
     LANGUAGE C;
 
+CREATE FUNCTION get_columns_length(oid[])
+    RETURNS int
+    AS :'regresslib'
+    LANGUAGE C STRICT STABLE PARALLEL SAFE;
+
 -- Use hand-rolled hash functions and operator classes to get predictable
 -- result on different machines.  The hash function for int4 simply returns
 -- the sum of the values passed to it and the one for text returns the length
diff --git a/src/tools/gen_export.pl b/src/tools/gen_export.pl
index d9fdaaaf6d..888c8a197a 100644
--- a/src/tools/gen_export.pl
+++ b/src/tools/gen_export.pl
@@ -16,11 +16,12 @@ GetOptions(
 	'input:s' => \$input,
 	'output:s' => \$output) or die "wrong arguments";
 
-if (not(   $format eq 'darwin'
+if (not(   $format eq 'aix'
+		or $format eq 'darwin'
 		or $format eq 'gnu'
 		or $format eq 'win'))
 {
-	die "$0: $format is not yet handled (only darwin, gnu, win are)\n";
+	die "$0: $format is not yet handled (only aix, darwin, gnu, win are)\n";
 }
 
 open(my $input_handle, '<', $input)
@@ -55,7 +56,11 @@ while (<$input_handle>)
 	}
 	elsif (/^(\S+)\s+(\S+)/)
 	{
-		if ($format eq 'darwin')
+		if ($format eq 'aix')
+		{
+			print $output_handle "$1\n";
+		}
+		elsif ($format eq 'darwin')
 		{
 			print $output_handle "_$1\n";
 		}
diff --git a/src/tools/pginclude/headerscheck b/src/tools/pginclude/headerscheck
index 4a157d0a5f..cfd8c6896c 100755
--- a/src/tools/pginclude/headerscheck
+++ b/src/tools/pginclude/headerscheck
@@ -85,6 +85,7 @@ do
 
 	# These files are platform-specific, and c.h will include the
 	# one that's relevant for our current platform anyway.
+	test "$f" = src/include/port/aix.h && continue
 	test "$f" = src/include/port/cygwin.h && continue
 	test "$f" = src/include/port/darwin.h && continue
 	test "$f" = src/include/port/freebsd.h && continue
-- 
2.41.0

From f162e7d01f34957c906f96cde865937e05f15038 Mon Sep 17 00:00:00 2001
From: Sriram RK <sriram.rk@in.ibm.com>
Date: Mon, 20 May 2024 01:38:59 -0500
Subject: [PATCH 1/1] AIX support, revert the changes from 0b16bb8776bb8. Trim
 AIX/XLC changes to support gcc only.

 - Review comments from Heikki.
 - Replace tas() AIX asm with gcc __sync_lock_test_and_set().
 - Fix tas() for powerPC.
---
 Makefile                                      |   2 -
 configure                                     |  37 +++---
 configure.ac                                  |  28 ++---
 doc/src/sgml/dfunc.sgml                       |  19 +++
 doc/src/sgml/installation.sgml                | 118 +++++++++++++++++-
 doc/src/sgml/runtime.sgml                     |  23 ++++
 meson.build                                   |  57 +++++----
 src/Makefile.shlib                            |  29 +++++
 src/backend/Makefile                          |  20 +++
 src/backend/meson.build                       |  15 +++
 src/backend/port/aix/mkldexport.sh            |  61 +++++++++
 src/backend/utils/error/elog.c                |   2 +
 src/backend/utils/misc/ps_status.c            |   4 +-
 src/bin/pg_basebackup/t/010_pg_basebackup.pl  |   3 +-
 src/bin/pg_verifybackup/t/008_untar.pl        |   3 +-
 src/bin/pg_verifybackup/t/010_client_untar.pl |   3 +-
 src/include/c.h                               |   4 +-
 src/include/port/aix.h                        |   6 +
 src/include/storage/s_lock.h                  |  62 +++------
 src/interfaces/libpq/Makefile                 |   2 +-
 src/interfaces/libpq/meson.build              |   5 +-
 src/makefiles/Makefile.aix                    |  39 ++++++
 src/port/README                               |   2 +-
 src/port/strerror.c                           |   2 +
 src/template/aix                              |  14 +++
 src/test/regress/Makefile                     |   5 +
 src/test/regress/expected/sanity_check.out    |  29 +++++
 src/test/regress/expected/test_setup.out      |   4 +
 src/test/regress/regress.c                    |  40 ++++++
 src/test/regress/sql/sanity_check.sql         |  26 ++++
 src/test/regress/sql/test_setup.sql           |   5 +
 src/tools/gen_export.pl                       |  11 +-
 src/tools/pginclude/headerscheck              |   1 +
 33 files changed, 554 insertions(+), 127 deletions(-)
 create mode 100755 src/backend/port/aix/mkldexport.sh
 create mode 100644 src/include/port/aix.h
 create mode 100644 src/makefiles/Makefile.aix
 create mode 100644 src/template/aix

diff --git a/Makefile b/Makefile
index 8a2ec9396b..9bc1a4ec17 100644
--- a/Makefile
+++ b/Makefile
@@ -13,8 +13,6 @@
 
 # AIX make defaults to building *every* target of the first rule.  Start with
 # a single-target, empty rule to make the other targets non-default.
-# (We don't support AIX anymore, but if someone tries to build on AIX anyway,
-# at least they'll get the instructions to run 'configure' first.)
 all:
 
 all check install installdirs installcheck installcheck-parallel uninstall clean distclean maintainer-clean dist distcheck world check-world install-world installcheck-world:
diff --git a/configure b/configure
index 89644f2249..f218b2e040 100755
--- a/configure
+++ b/configure
@@ -2988,6 +2988,7 @@ else
 # --with-template not given
 
 case $host_os in
+     aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -6848,7 +6849,6 @@ if test x"$pgac_cv_prog_CXX_cxxflags__fno_strict_aliasing" = x"yes"; then
   CXXFLAGS="${CXXFLAGS} -fno-strict-aliasing"
 fi
 
-
 fi
 
 # If the compiler knows how to hide symbols, add the switch needed for that to
@@ -12860,7 +12860,8 @@ fi
 
 fi
 
-# Note: We can test for libldap_r only after we know PTHREAD_LIBS
+# Note: We can test for libldap_r only after we know PTHREAD_LIBS;
+# also, on AIX, we may need to have openssl in LIBS for this step.
 if test "$with_ldap" = yes ; then
   _LIBS="$LIBS"
   if test "$PORTNAME" != "win32"; then
@@ -16951,28 +16952,18 @@ _ACEOF
 
 
 # Compute maximum alignment of any basic type.
-#
-# We require 'double' to have the strictest alignment among the basic types,
-# because otherwise the C ABI might impose 8-byte alignment on some of the
-# other C types that correspond to TYPALIGN_DOUBLE SQL types.  That could
-# cause a mismatch between the tuple layout and the C struct layout of a
-# catalog tuple.  We used to carefully order catalog columns such that any
-# fixed-width, attalign=4 columns were at offsets divisible by 8 regardless
-# of MAXIMUM_ALIGNOF to avoid that, but we no longer support any platforms
-# where TYPALIGN_DOUBLE != MAXIMUM_ALIGNOF.
-#
-# We assume without checking that long's alignment is at least as strong as
-# char, short, or int.  Note that we intentionally do not consider any types
-# wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
-# much of a penalty for disk and memory space.
-
-MAX_ALIGNOF=$ac_cv_alignof_double
+# We assume long's alignment is at least as strong as char, short, or int;
+# but we must check long long (if it is being used for int64) and double.
+# Note that we intentionally do not consider any types wider than 64 bits,
+# as allowing MAXIMUM_ALIGNOF to exceed 8 would be too much of a penalty
+# for disk and memory space.
 
-if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
+MAX_ALIGNOF=$ac_cv_alignof_long
+if test $MAX_ALIGNOF -lt $ac_cv_alignof_double ; then
+  MAX_ALIGNOF=$ac_cv_alignof_double
 fi
-if test x"$HAVE_LONG_LONG_INT_64" = xyes && test $ac_cv_alignof_long_long_int -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'long long int' is greater than the alignment of 'double'" "$LINENO" 5
+if test x"$HAVE_LONG_LONG_INT_64" = xyes && test $MAX_ALIGNOF -lt $ac_cv_alignof_long_long_int ; then
+  MAX_ALIGNOF="$ac_cv_alignof_long_long_int"
 fi
 
 cat >>confdefs.h <<_ACEOF
@@ -17090,7 +17081,7 @@ else
 /* end confdefs.h.  */
 
 /* This must match the corresponding code in c.h: */
-#if defined(__GNUC__) || defined(__SUNPRO_C)
+#if defined(__GNUC__) || defined(__SUNPRO_C) || defined(__IBMC__)
 #define pg_attribute_aligned(a) __attribute__((aligned(a)))
 #elif defined(_MSC_VER)
 #define pg_attribute_aligned(a) __declspec(align(a))
diff --git a/configure.ac b/configure.ac
index c7322e292c..a059509cd9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -62,6 +62,7 @@ PGAC_ARG_REQ(with, template, [NAME], [override operating system template],
 # --with-template not given
 
 case $host_os in
+     aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -1385,7 +1386,8 @@ if test "$with_zstd" = yes ; then
   AC_CHECK_LIB(zstd, ZSTD_compress, [], [AC_MSG_ERROR([library 'zstd' is required for ZSTD support])])
 fi
 
-# Note: We can test for libldap_r only after we know PTHREAD_LIBS
+# Note: We can test for libldap_r only after we know PTHREAD_LIBS;
+# also, on AIX, we may need to have openssl in LIBS for this step.
 if test "$with_ldap" = yes ; then
   _LIBS="$LIBS"
   if test "$PORTNAME" != "win32"; then
@@ -1643,8 +1645,9 @@ PGAC_TYPE_LOCALE_T
 # spelling it understands, because it conflicts with
 # __declspec(restrict). Therefore we define pg_restrict to the
 # appropriate definition, which presumably won't conflict.
+#
 AC_C_RESTRICT
-if test "$ac_cv_c_restrict" = "no"; then
+if test "$ac_cv_c_restrict" = "no" ; then
   pg_restrict=""
 else
   pg_restrict="$ac_cv_c_restrict"
@@ -1996,22 +1999,11 @@ fi
 AC_CHECK_ALIGNOF(double)
 
 # Compute maximum alignment of any basic type.
-#
-# We require 'double' to have the strictest alignment among the basic types,
-# because otherwise the C ABI might impose 8-byte alignment on some of the
-# other C types that correspond to TYPALIGN_DOUBLE SQL types.  That could
-# cause a mismatch between the tuple layout and the C struct layout of a
-# catalog tuple.  We used to carefully order catalog columns such that any
-# fixed-width, attalign=4 columns were at offsets divisible by 8 regardless
-# of MAXIMUM_ALIGNOF to avoid that, but we no longer support any platforms
-# where TYPALIGN_DOUBLE != MAXIMUM_ALIGNOF.
-#
-# We assume without checking that long's alignment is at least as strong as
-# char, short, or int.  Note that we intentionally do not consider any types
-# wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
-# much of a penalty for disk and memory space.
-
-MAX_ALIGNOF=$ac_cv_alignof_double
+# We assume long's alignment is at least as strong as char, short, or int;
+# but we must check long long (if it is being used for int64) and double.
+# Note that we intentionally do not consider any types wider than 64 bits,
+# as allowing MAXIMUM_ALIGNOF to exceed 8 would be too much of a penalty
+# for disk and memory space.
 
 if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
   AC_MSG_ERROR([alignment of 'long' is greater than the alignment of 'double'])
diff --git a/doc/src/sgml/dfunc.sgml b/doc/src/sgml/dfunc.sgml
index b94aefcd0c..554f9fac4c 100644
--- a/doc/src/sgml/dfunc.sgml
+++ b/doc/src/sgml/dfunc.sgml
@@ -202,4 +202,23 @@ gcc -G -o foo.so foo.o
   server expects to find the shared library files.
  </para>
 
+<!--
+Under AIX, object files are compiled normally but building the shared
+library requires a couple of steps.  First, create the object file:
+.nf
+cc <other flags> -c foo.c
+.fi
+You must then create a symbol \*(lqexports\*(rq file for the object
+file:
+.nf
+mkldexport foo.o `pwd` &gt; foo.exp
+.fi
+Finally, you can create the shared library:
+.nf
+ld <other flags> -H512 -T512 -o foo.so -e _nostart \e
+   -bI:.../lib/postgres.exp -bE:foo.exp foo.o \e
+   -lm -lc 2>/dev/null
+.fi
+  -->
+
 </sect2>
diff --git a/doc/src/sgml/installation.sgml b/doc/src/sgml/installation.sgml
index 1b32d5ca62..60e9a34a03 100644
--- a/doc/src/sgml/installation.sgml
+++ b/doc/src/sgml/installation.sgml
@@ -3401,7 +3401,7 @@ export MANPATH
   <para>
    <productname>PostgreSQL</productname> can be expected to work on current
    versions of these operating systems: Linux, Windows,
-   FreeBSD, OpenBSD, NetBSD, DragonFlyBSD, macOS, Solaris, and illumos.
+   FreeBSD, OpenBSD, NetBSD, DragonFlyBSD, macOS, AIX, Solaris, and illumos.
    Other Unix-like systems may also work but are not currently
    being tested.  In most cases, all CPU architectures supported by
    a given operating system will work.  Look in
@@ -3445,6 +3445,122 @@ export MANPATH
    installation issues.
   </para>
 
+  <sect2 id="installation-notes-aix">
+   <title>AIX</title>
+
+   <indexterm zone="installation-notes-aix">
+    <primary>AIX</primary>
+    <secondary>installation on</secondary>
+   </indexterm>
+
+   <para>
+    You can use GCC to build <productname>PostgreSQL</productname>
+    on <productname>AIX</productname>.
+   </para>
+
+   <para>
+    <productname>AIX</productname> versions before 7.1 are no longer
+    tested nor supported by the <productname>PostgreSQL</productname>
+    community.
+   </para>
+
+   <sect3 id="installation-notes-aix-mem-management">
+    <title>Memory Management</title>
+    <!-- https://archives.postgresql.org/message-id/603bgqmpl9.fsf@dba2.int.libertyrms.com -->
+
+    <para>
+     AIX can be somewhat peculiar with regards to the way it does
+     memory management.  You can have a server with many multiples of
+     gigabytes of RAM free, but still get out of memory or address
+     space errors when running applications.  One example
+     is loading of extensions failing with unusual errors.
+     For example, running as the owner of the PostgreSQL installation:
+<screen>
+=# CREATE EXTENSION plperl;
+ERROR:  could not load library "/opt/dbs/pgsql/lib/plperl.so": A memory address is not in the address space for the process.
+</screen>
+    Running as a non-owner in the group possessing the PostgreSQL
+    installation:
+<screen>
+=# CREATE EXTENSION plperl;
+ERROR:  could not load library "/opt/dbs/pgsql/lib/plperl.so": Bad address
+</screen>
+     Another example is out of memory errors in the PostgreSQL server
+     logs, with every memory allocation near or greater than 256 MB
+     failing.
+    </para>
+
+    <para>
+     The overall cause of all these problems is the default bittedness
+     and memory model used by the server process.  By default, all
+     binaries built on AIX are 32-bit.  This does not depend upon
+     hardware type or kernel in use.  These 32-bit processes are
+     limited to 4 GB of memory laid out in 256 MB segments using one
+     of a few models.  The default allows for less than 256 MB in the
+     heap as it shares a single segment with the stack.
+    </para>
+
+    <para>
+     In the case of the <literal>plperl</literal> example, above,
+     check your umask and the permissions of the binaries in your
+     PostgreSQL installation.  The binaries involved in that example
+     were 32-bit and installed as mode 750 instead of 755.  Due to the
+     permissions being set in this fashion, only the owner or a member
+     of the possessing group can load the library.  Since it isn't
+     world-readable, the loader places the object into the process'
+     heap instead of the shared library segments where it would
+     otherwise be placed.
+    </para>
+
+    <para>
+     The <quote>ideal</quote> solution for this is to use a 64-bit
+     build of PostgreSQL, but that is not always practical, because
+     systems with 32-bit processors can build, but not run, 64-bit
+     binaries.
+    </para>
+
+    <para>
+     If a 32-bit binary is desired, set <symbol>LDR_CNTRL</symbol> to
+     <literal>MAXDATA=0x<replaceable>n</replaceable>0000000</literal>,
+     where 1 &lt;= n &lt;= 8, before starting the PostgreSQL server,
+     and try different values and <filename>postgresql.conf</filename>
+     settings to find a configuration that works satisfactorily.  This
+     use of <symbol>LDR_CNTRL</symbol> tells AIX that you want the
+     server to have <symbol>MAXDATA</symbol> bytes set aside for the
+     heap, allocated in 256 MB segments.  When you find a workable
+     configuration,
+     <command>ldedit</command> can be used to modify the binaries so
+     that they default to using the desired heap size.  PostgreSQL can
+     also be rebuilt, passing <literal>configure
+     LDFLAGS="-Wl,-bmaxdata:0x<replaceable>n</replaceable>0000000"</literal>
+     to achieve the same effect.
+    </para>
+
+    <para>
+     For a 64-bit build, set <envar>OBJECT_MODE</envar> to 64 and
+     pass <literal>CC="gcc -maix64"</literal>
+     and <literal>LDFLAGS="-Wl,-bbigtoc"</literal>
+     to <command>configure</command>. 
+     If you omit the export of
+    <envar>OBJECT_MODE</envar>, your build may fail with linker errors.  When
+    <envar>OBJECT_MODE</envar> is set, it tells AIX's build utilities
+    such as <command>ar</command>, <command>as</command>, and <command>ld</command> what
+    type of objects to default to handling.
+    </para>
+
+    <para>
+     By default, overcommit of paging space can happen.  While we have
+     not seen this occur, AIX will kill processes when it runs out of
+     memory and the overcommit is accessed.  The closest to this that
+     we have seen is fork failing because the system decided that
+     there was not enough memory for another process.  Like many other
+     parts of AIX, the paging space allocation method and
+     out-of-memory kill is configurable on a system- or process-wide
+     basis if this becomes a problem.
+    </para>
+   </sect3>
+  </sect2>
+
   <sect2 id="installation-notes-cygwin">
    <title>Cygwin</title>
 
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index 6047b8171d..64753d9c01 100644
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -891,6 +891,29 @@ psql: error: connection to server on socket "/tmp/.s.PGSQL.5432" failed: No such
 
 
     <variablelist>
+     <varlistentry>
+      <term><systemitem class="osname">AIX</systemitem>
+      <indexterm><primary>AIX</primary><secondary>IPC configuration</secondary></indexterm>
+      </term>
+      <listitem>
+       <para>
+        It should not be necessary to do
+        any special configuration for such parameters as
+        <varname>SHMMAX</varname>, as it appears this is configured to
+        allow all memory to be used as shared memory.  That is the
+        sort of configuration commonly used for other databases such
+        as <application>DB/2</application>.</para>
+
+       <para> It might, however, be necessary to modify the global
+       <command>ulimit</command> information in
+       <filename>/etc/security/limits</filename>, as the default hard
+       limits for file sizes (<varname>fsize</varname>) and numbers of
+       files (<varname>nofiles</varname>) might be too low.
+       </para>
+      </listitem>
+     </varlistentry>
+
+
      <varlistentry>
       <term><systemitem class="osname">FreeBSD</systemitem>
       <indexterm><primary>FreeBSD</primary><secondary>IPC configuration</secondary></indexterm>
diff --git a/meson.build b/meson.build
index 1c0579d5a6..f1ac154cdc 100644
--- a/meson.build
+++ b/meson.build
@@ -196,7 +196,26 @@ endif
 # that purpose.
 portname = host_system
 
-if host_system == 'cygwin'
+if host_system == 'aix'
+  library_path_var = 'LIBPATH'
+
+  export_file_format = 'aix'
+  export_fmt = '-Wl,-bE:@0@'
+  mod_link_args_fmt = ['-Wl,-bI:@0@']
+  mod_link_with_dir = 'libdir'
+  mod_link_with_name = '@0@.imp'
+
+  # M:SRE sets a flag indicating that an object is a shared library. Seems to
+  # work in some circumstances without, but required in others.
+  ldflags_sl += '-Wl,-bM:SRE'
+  ldflags_be += '-Wl,-brtllib'
+
+  # Native memset() is faster, tested on:
+  # - AIX 5.1 and 5.2, XLC 6.0 (IBM's cc)
+  # - AIX 5.3 ML3, gcc 4.0.1
+  memset_loop_limit = 0
+
+elif host_system == 'cygwin'
   sema_kind = 'unnamed_posix'
   cppflags += '-D_GNU_SOURCE'
   dlsuffix = '.dll'
@@ -1490,11 +1509,11 @@ sizeof_long = cc.sizeof('long', args: test_c_args)
 cdata.set('SIZEOF_LONG', sizeof_long)
 if sizeof_long == 8
   cdata.set('HAVE_LONG_INT_64', 1)
-  pg_int64_type = 'long int'
+  cdata.set('PG_INT64_TYPE', 'long int')
   cdata.set_quoted('INT64_MODIFIER', 'l')
 elif sizeof_long == 4 and cc.sizeof('long long', args: test_c_args) == 8
   cdata.set('HAVE_LONG_LONG_INT_64', 1)
-  pg_int64_type = 'long long int'
+  cdata.set('PG_INT64_TYPE', 'long long int')
   cdata.set_quoted('INT64_MODIFIER', 'll')
 else
   error('do not know how to get a 64bit int')
@@ -1508,31 +1527,15 @@ endif
 # Determine memory alignment requirements for the basic C data types.
 
 alignof_types = ['short', 'int', 'long', 'double']
+maxalign = 0
 foreach t : alignof_types
   align = cc.alignment(t, args: test_c_args)
+  if maxalign < align
+    maxalign = align
+  endif
   cdata.set('ALIGNOF_@0@'.format(t.to_upper()), align)
 endforeach
-
-# Compute maximum alignment of any basic type.
-#
-# We require 'double' to have the strictest alignment among the basic types,
-# because otherwise the C ABI might impose 8-byte alignment on some of the
-# other C types that correspond to TYPALIGN_DOUBLE SQL types.  That could
-# cause a mismatch between the tuple layout and the C struct layout of a
-# catalog tuple.  We used to carefully order catalog columns such that any
-# fixed-width, attalign=4 columns were at offsets divisible by 8 regardless
-# of MAXIMUM_ALIGNOF to avoid that, but we no longer support any platforms
-# where TYPALIGN_DOUBLE != MAXIMUM_ALIGNOF.
-#
-# We assume without checking that int64's alignment is at least as strong
-# as long, char, short, or int.  Note that we intentionally do not consider
-# any types wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8
-# would be too much of a penalty for disk and memory space.
-alignof_double = cdata.get('ALIGNOF_DOUBLE')
-if cc.alignment(pg_int64_type, args: test_c_args) > alignof_double
-  error('alignment of int64 is greater than the alignment of double')
-endif
-cdata.set('MAXIMUM_ALIGNOF', alignof_double)
+cdata.set('MAXIMUM_ALIGNOF', maxalign)
 
 cdata.set('SIZEOF_VOID_P', cc.sizeof('void *', args: test_c_args))
 cdata.set('SIZEOF_SIZE_T', cc.sizeof('size_t', args: test_c_args))
@@ -1581,7 +1584,7 @@ if cc.links('''
   if not meson.is_cross_build()
     r = cc.run('''
     /* This must match the corresponding code in c.h: */
-    #if defined(__GNUC__) || defined(__SUNPRO_C)
+    #if defined(__GNUC__) || defined(__SUNPRO_C) || defined(__IBMC__)
     #define pg_attribute_aligned(a) __attribute__((aligned(a)))
     #elif defined(_MSC_VER)
     #define pg_attribute_aligned(a) __declspec(align(a))
@@ -2476,6 +2479,10 @@ endif
 # conflict.
 #
 # We assume C99 support, so we don't need to make this conditional.
+#
+# XXX: Historically we allowed platforms to disable restrict in template
+# files, but that was only added for AIX when building with XLC, which we
+# don't support yet.
 cdata.set('pg_restrict', '__restrict')
 
 
diff --git a/src/Makefile.shlib b/src/Makefile.shlib
index fa81f6ffdd..8ca51ca03f 100644
--- a/src/Makefile.shlib
+++ b/src/Makefile.shlib
@@ -106,6 +106,20 @@ ifdef SO_MAJOR_VERSION
 override CPPFLAGS += -DSO_MAJOR_VERSION=$(SO_MAJOR_VERSION)
 endif
 
+ifeq ($(PORTNAME), aix)
+  LINK.shared		= $(COMPILER)
+  ifdef SO_MAJOR_VERSION
+    shlib		= lib$(NAME)$(DLSUFFIX).$(SO_MAJOR_VERSION)
+  endif
+  haslibarule   = yes
+  # $(exports_file) is also usable as an import file
+  exports_file		= lib$(NAME).exp
+  BUILD.exports		= ( echo '\#! $(shlib)'; $(AWK) '/^[^\#]/ {printf "%s\n",$$1}' $< ) > $@
+  ifneq (,$(SHLIB_EXPORTS))
+    LINK.shared		+= -Wl,-bE:$(exports_file)
+  endif
+endif
+
 ifeq ($(PORTNAME), darwin)
   ifdef soname
     # linkable library
@@ -254,6 +268,14 @@ $(stlib): $(OBJS) | $(SHLIB_PREREQS)
 	touch $@
 endif #haslibarule
 
+# AIX wraps shared libraries inside a static library, can be used both
+# for static and shared linking
+ifeq ($(PORTNAME), aix)
+$(stlib): $(shlib)
+	rm -f $(stlib)
+	$(AR) $(AROPT) $(stlib) $(shlib)
+endif # aix
+
 ifeq (,$(filter cygwin win32,$(PORTNAME)))
 
 # Normal case
@@ -267,8 +289,11 @@ ifneq ($(shlib), $(shlib_major))
 endif
 # Make sure we have a link to a name without any version numbers
 ifneq ($(shlib), $(shlib_bare))
+# except on AIX, where that's not a thing
+ifneq ($(PORTNAME), aix)
 	rm -f $(shlib_bare)
 	$(LN_S) $(shlib) $(shlib_bare)
+endif # aix
 endif # shlib_bare
 endif # shlib_major
 
@@ -376,6 +401,9 @@ install-lib-static: $(stlib) installdirs-lib
 
 install-lib-shared: $(shlib) installdirs-lib
 ifdef soname
+# we don't install $(shlib) on AIX
+# (see http://archives.postgresql.org/message-id/52EF20B2E3209443BC37736D00C3C1380A6E79FE@EXADV1.host.magwien.gv.at)
+ifneq ($(PORTNAME), aix)
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(libdir)/$(shlib)'
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
@@ -391,6 +419,7 @@ ifneq ($(shlib), $(shlib_bare))
 endif
 endif # not win32
 endif # not cygwin
+endif # not aix
 ifneq (,$(findstring $(PORTNAME),win32 cygwin))
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(bindir)/$(shlib)'
 endif
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 6700aec039..954b14962f 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -62,12 +62,14 @@ all: submake-libpgport submake-catalog-headers submake-utils-headers postgres $(
 
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
+ifneq ($(PORTNAME), aix)
 
 postgres: $(OBJS)
 	$(CC) $(CFLAGS) $(call expand_subsys,$^) $(LDFLAGS) $(LIBS) -o $@
 
 endif
 endif
+endif
 
 ifeq ($(PORTNAME), cygwin)
 
@@ -94,6 +96,24 @@ libpostgres.a: postgres
 
 endif # win32
 
+ifeq ($(PORTNAME), aix)
+
+postgres: $(POSTGRES_IMP)
+	$(CC) $(CFLAGS) $(call expand_subsys,$(OBJS)) $(LDFLAGS) -Wl,-bE:$(top_builddir)/src/backend/$(POSTGRES_IMP) $(LIBS) -Wl,-brtllib -o $@
+
+# Linking to a single .o with -r is a lot faster than building a .a or passing
+# all objects to MKLDEXPORT.
+#
+# It looks alluring to use $(CC) -r instead of ld -r, but that doesn't
+# trivially work with gcc, due to gcc specific static libraries linked in with
+# -r.
+$(POSTGRES_IMP): $(OBJS)
+	ld -r -o SUBSYS.o $(call expand_subsys,$^)
+	$(MKLDEXPORT) SUBSYS.o . > $@
+	@rm -f SUBSYS.o
+
+endif # aix
+
 $(top_builddir)/src/port/libpgport_srv.a: | submake-libpgport
 
 
diff --git a/src/backend/meson.build b/src/backend/meson.build
index 436c04af08..8767aaba67 100644
--- a/src/backend/meson.build
+++ b/src/backend/meson.build
@@ -91,6 +91,21 @@ if cc.get_id() == 'msvc'
   # be restricted to b_pch=true.
   backend_link_with += postgres_lib
 
+elif host_system == 'aix'
+  # The '.' argument leads mkldexport.sh to emit "#! .", which refers to the
+  # main executable, allowing extension libraries to resolve their undefined
+  # symbols to symbols in the postgres binary.
+  postgres_imp = custom_target('postgres.imp',
+    command: [files('port/aix/mkldexport.sh'), '@INPUT@', '.'],
+    input: postgres_lib,
+    output: 'postgres.imp',
+    capture: true,
+    install: true,
+    install_dir: dir_lib,
+    build_by_default: false,
+  )
+  backend_link_args += '-Wl,-bE:@0@'.format(postgres_imp.full_path())
+  backend_link_depends += postgres_imp
 endif
 
 backend_input = []
diff --git a/src/backend/port/aix/mkldexport.sh b/src/backend/port/aix/mkldexport.sh
new file mode 100755
index 0000000000..adf3793e86
--- /dev/null
+++ b/src/backend/port/aix/mkldexport.sh
@@ -0,0 +1,61 @@
+#!/bin/sh
+#
+# mkldexport
+#	create an AIX exports file from an object file
+#
+# src/backend/port/aix/mkldexport.sh
+#
+# Usage:
+#	mkldexport objectfile [location]
+# where
+#	objectfile is the current location of the object file.
+#	location is the eventual (installed) location of the
+#		object file (if different from the current
+#		working directory).
+#
+# [This file comes from the Postgres 4.2 distribution. - ay 7/95]
+#
+# Header: /usr/local/devel/postgres/src/tools/mkldexport/RCS/mkldexport.sh,v 1.2 1994/03/13 04:59:12 aoki Exp
+#
+
+# setting this to nm -B might be better
+# ... due to changes in AIX 4.x ...
+# ... let us search in different directories - Gerhard Reithofer
+if [ -x /usr/ucb/nm ]
+then NM=/usr/ucb/nm
+elif [ -x /usr/bin/nm ]
+then NM=/usr/bin/nm
+elif [ -x /usr/ccs/bin/nm ]
+then NM=/usr/ccs/bin/nm
+elif [ -x /usr/usg/bin/nm ]
+then NM=/usr/usg/bin/nm
+else echo "Fatal error: cannot find `nm' ... please check your installation."
+     exit 1
+fi
+
+CMDNAME=`basename $0`
+if [ -z "$1" ]; then
+	echo "Usage: $CMDNAME object [location]"
+	exit 1
+fi
+OBJNAME=`basename $1`
+if [ "`basename $OBJNAME`" != "`basename $OBJNAME .o`" ]; then
+	OBJNAME=`basename $OBJNAME .o`.so
+fi
+if [ -z "$2" ]; then
+	echo '#!'
+else
+	if [ "$2" = "." ]; then
+		# for the base executable (AIX 4.2 and up)
+		echo '#! .'
+	else
+		echo '#!' $2
+	fi
+fi
+$NM -BCg $1 | \
+	egrep ' [TDB] ' | \
+	sed -e 's/.* //' | \
+	egrep -v '\$' | \
+	sed -e 's/^[.]//' | \
+	sort | \
+	uniq
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index d91a85cb2d..7b51e94f4a 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -908,7 +908,9 @@ errcode_for_file_access(void)
 			/* Wrong object type or state */
 		case ENOTDIR:			/* Not a directory */
 		case EISDIR:			/* Is a directory */
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:			/* Directory not empty */
+#endif
 			edata->sqlerrcode = ERRCODE_WRONG_OBJECT_TYPE;
 			break;
 
diff --git a/src/backend/utils/misc/ps_status.c b/src/backend/utils/misc/ps_status.c
index 9da6377402..532eac31b4 100644
--- a/src/backend/utils/misc/ps_status.c
+++ b/src/backend/utils/misc/ps_status.c
@@ -50,7 +50,7 @@ bool		update_process_title = DEFAULT_UPDATE_PROCESS_TITLE;
 #define PS_USE_SETPROCTITLE_FAST
 #elif defined(HAVE_SETPROCTITLE)
 #define PS_USE_SETPROCTITLE
-#elif defined(__linux__) || defined(__sun) || defined(__darwin__)
+#elif defined(__linux__) || defined(_AIX) || defined(__sun) || defined(__darwin__)
 #define PS_USE_CLOBBER_ARGV
 #elif defined(WIN32)
 #define PS_USE_WIN32
@@ -60,7 +60,7 @@ bool		update_process_title = DEFAULT_UPDATE_PROCESS_TITLE;
 
 
 /* Different systems want the buffer padded differently */
-#if defined(__linux__) || defined(__darwin__)
+#if defined(_AIX) || defined(__linux__) || defined(__darwin__)
 #define PS_PADDING '\0'
 #else
 #define PS_PADDING ' '
diff --git a/src/bin/pg_basebackup/t/010_pg_basebackup.pl b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
index 2d4b75a6fe..ce936959c1 100644
--- a/src/bin/pg_basebackup/t/010_pg_basebackup.pl
+++ b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
@@ -401,7 +401,8 @@ SKIP:
 {
 	my $tar = $ENV{TAR};
 	# don't check for a working tar here, to accommodate various odd
-	# cases. If tar doesn't work the init_from_backup below will fail.
+	# cases such as AIX. If tar doesn't work the init_from_backup below
+	# will fail.
 	skip "no tar program available", 1
 	  if (!defined $tar || $tar eq '');
 
diff --git a/src/bin/pg_verifybackup/t/008_untar.pl b/src/bin/pg_verifybackup/t/008_untar.pl
index 7a09f3b75b..30d9f3f7f0 100644
--- a/src/bin/pg_verifybackup/t/008_untar.pl
+++ b/src/bin/pg_verifybackup/t/008_untar.pl
@@ -104,7 +104,8 @@ for my $tc (@test_configuration)
 		{
 			my $tar = $ENV{TAR};
 			# don't check for a working tar here, to accommodate various odd
-			# cases. If tar doesn't work the init_from_backup below will fail.
+			# cases such as AIX. If tar doesn't work the init_from_backup below
+			# will fail.
 			skip "no tar program available", 1
 			  if (!defined $tar || $tar eq '');
 
diff --git a/src/bin/pg_verifybackup/t/010_client_untar.pl b/src/bin/pg_verifybackup/t/010_client_untar.pl
index 8c076d46de..45010d79ac 100644
--- a/src/bin/pg_verifybackup/t/010_client_untar.pl
+++ b/src/bin/pg_verifybackup/t/010_client_untar.pl
@@ -134,7 +134,8 @@ for my $tc (@test_configuration)
 		{
 			my $tar = $ENV{TAR};
 			# don't check for a working tar here, to accommodate various odd
-			# cases. If tar doesn't work the init_from_backup below will fail.
+			# cases such as AIX. If tar doesn't work the init_from_backup below
+			# will fail.
 			skip "no tar program available", 1
 			  if (!defined $tar || $tar eq '');
 
diff --git a/src/include/c.h b/src/include/c.h
index dc1841346c..641cd9bdf1 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -182,7 +182,7 @@
 #define PG_USED_FOR_ASSERTS_ONLY pg_attribute_unused()
 #endif
 
-/* GCC supports format attributes */
+/* GCC support format attributes */
 #if defined(__GNUC__)
 #define pg_attribute_format_arg(a) __attribute__((format_arg(a)))
 #define pg_attribute_printf(f,a) __attribute__((format(PG_PRINTF_ATTRIBUTE, f, a)))
@@ -192,7 +192,7 @@
 #endif
 
 /* GCC and Sunpro support aligned, packed and noreturn */
-#if defined(__GNUC__) || defined(__SUNPRO_C)
+#if defined(__GNUC__) || defined(__SUNPRO_C) 
 #define pg_attribute_aligned(a) __attribute__((aligned(a)))
 #define pg_attribute_noreturn() __attribute__((noreturn))
 #define pg_attribute_packed() __attribute__((packed))
diff --git a/src/include/port/aix.h b/src/include/port/aix.h
new file mode 100644
index 0000000000..1c2d166791
--- /dev/null
+++ b/src/include/port/aix.h
@@ -0,0 +1,6 @@
+/*
+ * src/include/port/aix.h
+ */
+#define CLASS_CONFLICT
+#define DISABLE_XOPEN_NLS
+
diff --git a/src/include/storage/s_lock.h b/src/include/storage/s_lock.h
index 29ac6cdcd9..768dbbd2e3 100644
--- a/src/include/storage/s_lock.h
+++ b/src/include/storage/s_lock.h
@@ -401,57 +401,16 @@ typedef unsigned int slock_t;
 
 #define TAS(lock) tas(lock)
 
-/* On PPC, it's a win to use a non-locking test before the lwarx */
+/* On PPC, use the gcc atomic routines, to set the lock. */
 #define TAS_SPIN(lock)	(*(lock) ? 1 : TAS(lock))
 
-/*
- * The second operand of addi can hold a constant zero or a register number,
- * hence constraint "=&b" to avoid allocating r0.  "b" stands for "address
- * base register"; most operands having this register-or-zero property are
- * address bases, e.g. the second operand of lwax.
- *
- * NOTE: per the Enhanced PowerPC Architecture manual, v1.0 dated 7-May-2002,
- * an isync is a sufficient synchronization barrier after a lwarx/stwcx loop.
- * But if the spinlock is in ordinary memory, we can use lwsync instead for
- * better performance.
- */
 static __inline__ int
 tas(volatile slock_t *lock)
 {
-	slock_t _t;
-	int _res;
-
-	__asm__ __volatile__(
-"	lwarx   %0,0,%3,1	\n"
-"	cmpwi   %0,0		\n"
-"	bne     1f			\n"
-"	addi    %0,%0,1		\n"
-"	stwcx.  %0,0,%3		\n"
-"	beq     2f			\n"
-"1: \n"
-"	li      %1,1		\n"
-"	b       3f			\n"
-"2: \n"
-"	lwsync				\n"
-"	li      %1,0		\n"
-"3: \n"
-:	"=&b"(_t), "=r"(_res), "+m"(*lock)
-:	"r"(lock)
-:	"memory", "cc");
-	return _res;
+    return __sync_lock_test_and_set(lock, 1);
 }
 
-/*
- * PowerPC S_UNLOCK is almost standard but requires a "sync" instruction.
- * But we can use lwsync instead for better performance.
- */
-#define S_UNLOCK(lock)	\
-do \
-{ \
-	__asm__ __volatile__ ("	lwsync \n" ::: "memory"); \
-	*((volatile slock_t *) (lock)) = 0; \
-} while (0)
-
+#define S_UNLOCK(lock) __sync_lock_release(lock)
 #endif /* powerpc */
 
 
@@ -662,6 +621,21 @@ tas(volatile slock_t *lock)
 
 #if !defined(HAS_TEST_AND_SET)	/* We didn't trigger above, let's try here */
 
+#if defined(_AIX)	/* AIX */
+/*
+ * AIX (POWER)
+ */
+#define HAS_TEST_AND_SET
+
+#include <sys/atomic_op.h>
+
+typedef int slock_t;
+
+#define TAS(lock)			_check_lock((slock_t *) (lock), 0, 1)
+#define S_UNLOCK(lock)		_clear_lock((slock_t *) (lock), 0)
+#endif	 /* _AIX */
+
+
 /* These are in sunstudio_(sparc|x86).s */
 
 #if defined(__SUNPRO_C) && (defined(__i386) || defined(__x86_64__) || defined(__sparc__) || defined(__sparc))
diff --git a/src/interfaces/libpq/Makefile b/src/interfaces/libpq/Makefile
index b36a765764..154429d4d1 100644
--- a/src/interfaces/libpq/Makefile
+++ b/src/interfaces/libpq/Makefile
@@ -114,7 +114,7 @@ backend_src = $(top_srcdir)/src/backend
 # coding rule.
 libpq-refs-stamp: $(shlib)
 ifneq ($(enable_coverage), yes)
-ifeq (,$(filter solaris,$(PORTNAME)))
+ifeq (,$(filter aix solaris,$(PORTNAME)))
 	@if nm -A -u $< 2>/dev/null | grep -v -e __cxa_atexit -e __tsan_func_exit | grep exit; then \
 		echo 'libpq must not be calling any function which invokes exit'; exit 1; \
 	fi
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index ed2a4048d1..7e2017daf0 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -54,8 +54,9 @@ libpq_c_args = ['-DSO_MAJOR_VERSION=5']
 #    libpq_st, and {pgport,common}_shlib for libpq_sh
 #
 # We could try to avoid building the source files twice, but it probably adds
-# more complexity than its worth (reusing object files requires also linking
-# to the library on windows or breaks precompiled headers).
+# more complexity than its worth (AIX doesn't support link_whole yet, reusing
+# object files requires also linking to the library on windows or breaks
+# precompiled headers).
 libpq_st = static_library('libpq',
   libpq_sources,
   include_directories: [libpq_inc],
diff --git a/src/makefiles/Makefile.aix b/src/makefiles/Makefile.aix
new file mode 100644
index 0000000000..dd16a7a037
--- /dev/null
+++ b/src/makefiles/Makefile.aix
@@ -0,0 +1,39 @@
+# MAKE_EXPORTS is required for svr4 loaders that want a file of
+# symbol names to tell them what to export/import.
+MAKE_EXPORTS= true
+
+# -blibpath must contain ALL directories where we should look for libraries
+libpath := $(shell echo $(subst -L,:,$(filter -L/%,$(LDFLAGS))) | sed -e's/ //g'):/usr/lib:/lib
+
+# when building with gcc, need to make sure that libgcc can be found
+ifeq ($(GCC), yes)
+libpath := $(libpath):$(dir $(shell gcc -print-libgcc-file-name))
+endif
+
+rpath = -Wl,-blibpath:'$(rpathdir)$(libpath)'
+
+LDFLAGS_SL += -Wl,-bnoentry -Wl,-H512 -Wl,-bM:SRE
+
+# gcc needs to know it's building a shared lib, otherwise it'll not emit
+# correct code / link to the right support libraries
+ifeq ($(GCC), yes)
+LDFLAGS_SL += -shared
+endif
+
+# env var name to use in place of LD_LIBRARY_PATH
+ld_library_path_var = LIBPATH
+
+
+POSTGRES_IMP= postgres.imp
+
+ifdef PGXS
+BE_DLLLIBS= -Wl,-bI:$(pkglibdir)/$(POSTGRES_IMP)
+else
+BE_DLLLIBS= -Wl,-bI:$(top_builddir)/src/backend/$(POSTGRES_IMP)
+endif
+
+MKLDEXPORT_DIR=src/backend/port/aix
+MKLDEXPORT=$(top_srcdir)/$(MKLDEXPORT_DIR)/mkldexport.sh
+
+%$(DLSUFFIX): %.o
+	$(CC) $(CFLAGS) $*.o $(LDFLAGS) $(LDFLAGS_SL) -o $@ $(BE_DLLLIBS)
diff --git a/src/port/README b/src/port/README
index ed5c54a72f..97f18a6233 100644
--- a/src/port/README
+++ b/src/port/README
@@ -28,5 +28,5 @@ applications.
 from libpgport are linked first.  This avoids having applications
 dependent on symbols that are _used_ by libpq, but not intended to be
 exported by libpq.  libpq's libpgport usage changes over time, so such a
-dependency is a problem.  Windows, Linux, and macOS use an export
+dependency is a problem.  Windows, Linux, AIX, and macOS use an export
 list to control the symbols exported by libpq.
diff --git a/src/port/strerror.c b/src/port/strerror.c
index 4918ba821c..1070a49802 100644
--- a/src/port/strerror.c
+++ b/src/port/strerror.c
@@ -214,8 +214,10 @@ get_errno_symbol(int errnum)
 			return "ENOTCONN";
 		case ENOTDIR:
 			return "ENOTDIR";
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:
 			return "ENOTEMPTY";
+#endif
 		case ENOTSOCK:
 			return "ENOTSOCK";
 #ifdef ENOTSUP
diff --git a/src/template/aix b/src/template/aix
new file mode 100644
index 0000000000..0a788676c0
--- /dev/null
+++ b/src/template/aix
@@ -0,0 +1,14 @@
+# src/template/aix
+
+  # Due to a compiler bug, see 20171013023536.GA492146@rfd.leadboat.com for details,
+  # force restrict not to be used when compiling with xlc.
+#  FORCE_DISABLE_RESTRICT=yes
+#fi
+
+# Extra CFLAGS for code that will go into a shared library
+CFLAGS_SL=""
+
+# Native memset() is faster, tested on:
+# 	AIX 5.1 and 5.2, XLC 6.0 (IBM's cc)
+# 	AIX 5.3 ML3, gcc 4.0.1
+MEMSET_LOOP_LIMIT=0
diff --git a/src/test/regress/Makefile b/src/test/regress/Makefile
index 6409a485e8..7c665ff892 100644
--- a/src/test/regress/Makefile
+++ b/src/test/regress/Makefile
@@ -7,6 +7,11 @@
 # GNU make uses a make file named "GNUmakefile" in preference to "Makefile"
 # if it exists.  Postgres is shipped with a "GNUmakefile".
 
+
+# AIX make defaults to building *every* target of the first rule.  Start with
+# a single-target, empty rule to make the other targets non-default.
+all:
+
 all install clean check installcheck:
 	@echo "You must use GNU make to use Postgres.  It may be installed"
 	@echo "on your system with the name 'gmake'."
diff --git a/src/test/regress/expected/sanity_check.out b/src/test/regress/expected/sanity_check.out
index 8370c1561c..c5c675b750 100644
--- a/src/test/regress/expected/sanity_check.out
+++ b/src/test/regress/expected/sanity_check.out
@@ -25,3 +25,32 @@ SELECT relname, relkind
 ---------+---------
 (0 rows)
 
+--
+-- When ALIGNOF_DOUBLE==4 (e.g. AIX), the C ABI may impose 8-byte alignment on
+-- some of the C types that correspond to TYPALIGN_DOUBLE SQL types.  To ensure
+-- catalog C struct layout matches catalog tuple layout, arrange for the tuple
+-- offset of each fixed-width, attalign='d' catalog column to be divisible by 8
+-- unconditionally.  Keep such columns before the first NameData column of the
+-- catalog, since packagers can override NAMEDATALEN to an odd number.
+--
+WITH check_columns AS (
+ SELECT relname, attname,
+  array(
+   SELECT t.oid
+    FROM pg_type t JOIN pg_attribute pa ON t.oid = pa.atttypid
+    WHERE pa.attrelid = a.attrelid AND
+          pa.attnum > 0 AND pa.attnum < a.attnum
+    ORDER BY pa.attnum) AS coltypes
+ FROM pg_attribute a JOIN pg_class c ON c.oid = attrelid
+  JOIN pg_namespace n ON c.relnamespace = n.oid
+ WHERE attalign = 'd' AND relkind = 'r' AND
+  attnotnull AND attlen <> -1 AND n.nspname = 'pg_catalog'
+)
+SELECT relname, attname, coltypes, get_columns_length(coltypes)
+ FROM check_columns
+ WHERE get_columns_length(coltypes) % 8 != 0 OR
+       'name'::regtype::oid = ANY(coltypes);
+ relname | attname | coltypes | get_columns_length 
+---------+---------+----------+--------------------
+(0 rows)
+
diff --git a/src/test/regress/expected/test_setup.out b/src/test/regress/expected/test_setup.out
index 3d0eeec996..5d9e6bf12b 100644
--- a/src/test/regress/expected/test_setup.out
+++ b/src/test/regress/expected/test_setup.out
@@ -209,6 +209,10 @@ CREATE FUNCTION ttdummy ()
     RETURNS trigger
     AS :'regresslib'
     LANGUAGE C;
+CREATE FUNCTION get_columns_length(oid[])
+    RETURNS int
+    AS :'regresslib'
+    LANGUAGE C STRICT STABLE PARALLEL SAFE;
 -- Use hand-rolled hash functions and operator classes to get predictable
 -- result on different machines.  The hash function for int4 simply returns
 -- the sum of the values passed to it and the one for text returns the length
diff --git a/src/test/regress/regress.c b/src/test/regress/regress.c
index deffaea578..cc633864d7 100644
--- a/src/test/regress/regress.c
+++ b/src/test/regress/regress.c
@@ -1221,3 +1221,43 @@ binary_coercible(PG_FUNCTION_ARGS)
 
 	PG_RETURN_BOOL(IsBinaryCoercible(srctype, targettype));
 }
+
+/*
+ * Return the length of the portion of a tuple consisting of the given array
+ * of data types.  The input data types must be fixed-length data types.
+ */
+PG_FUNCTION_INFO_V1(get_columns_length);
+Datum
+get_columns_length(PG_FUNCTION_ARGS)
+{
+	ArrayType  *ta = PG_GETARG_ARRAYTYPE_P(0);
+	Oid		   *type_oids;
+	int			ntypes;
+	int			column_offset = 0;
+
+	if (ARR_HASNULL(ta) && array_contains_nulls(ta))
+		elog(ERROR, "argument must not contain nulls");
+
+	if (ARR_NDIM(ta) > 1)
+		elog(ERROR, "argument must be empty or one-dimensional array");
+
+	type_oids = (Oid *) ARR_DATA_PTR(ta);
+	ntypes = ArrayGetNItems(ARR_NDIM(ta), ARR_DIMS(ta));
+	for (int i = 0; i < ntypes; i++)
+	{
+		Oid			typeoid = type_oids[i];
+		int16		typlen;
+		bool		typbyval;
+		char		typalign;
+
+		get_typlenbyvalalign(typeoid, &typlen, &typbyval, &typalign);
+
+		/* the data type must be fixed-length */
+		if (typlen < 0)
+			elog(ERROR, "type %u is not fixed-length data type", typeoid);
+
+		column_offset = att_align_nominal(column_offset + typlen, typalign);
+	}
+
+	PG_RETURN_INT32(column_offset);
+}
diff --git a/src/test/regress/sql/sanity_check.sql b/src/test/regress/sql/sanity_check.sql
index 162e5324b5..7f338d191c 100644
--- a/src/test/regress/sql/sanity_check.sql
+++ b/src/test/regress/sql/sanity_check.sql
@@ -19,3 +19,29 @@ SELECT relname, relkind
   FROM pg_class
  WHERE relkind IN ('v', 'c', 'f', 'p', 'I')
        AND relfilenode <> 0;
+
+--
+-- When ALIGNOF_DOUBLE==4 (e.g. AIX), the C ABI may impose 8-byte alignment on
+-- some of the C types that correspond to TYPALIGN_DOUBLE SQL types.  To ensure
+-- catalog C struct layout matches catalog tuple layout, arrange for the tuple
+-- offset of each fixed-width, attalign='d' catalog column to be divisible by 8
+-- unconditionally.  Keep such columns before the first NameData column of the
+-- catalog, since packagers can override NAMEDATALEN to an odd number.
+--
+WITH check_columns AS (
+ SELECT relname, attname,
+  array(
+   SELECT t.oid
+    FROM pg_type t JOIN pg_attribute pa ON t.oid = pa.atttypid
+    WHERE pa.attrelid = a.attrelid AND
+          pa.attnum > 0 AND pa.attnum < a.attnum
+    ORDER BY pa.attnum) AS coltypes
+ FROM pg_attribute a JOIN pg_class c ON c.oid = attrelid
+  JOIN pg_namespace n ON c.relnamespace = n.oid
+ WHERE attalign = 'd' AND relkind = 'r' AND
+  attnotnull AND attlen <> -1 AND n.nspname = 'pg_catalog'
+)
+SELECT relname, attname, coltypes, get_columns_length(coltypes)
+ FROM check_columns
+ WHERE get_columns_length(coltypes) % 8 != 0 OR
+       'name'::regtype::oid = ANY(coltypes);
diff --git a/src/test/regress/sql/test_setup.sql b/src/test/regress/sql/test_setup.sql
index 06b0e2121f..1b2d434683 100644
--- a/src/test/regress/sql/test_setup.sql
+++ b/src/test/regress/sql/test_setup.sql
@@ -257,6 +257,11 @@ CREATE FUNCTION ttdummy ()
     AS :'regresslib'
     LANGUAGE C;
 
+CREATE FUNCTION get_columns_length(oid[])
+    RETURNS int
+    AS :'regresslib'
+    LANGUAGE C STRICT STABLE PARALLEL SAFE;
+
 -- Use hand-rolled hash functions and operator classes to get predictable
 -- result on different machines.  The hash function for int4 simply returns
 -- the sum of the values passed to it and the one for text returns the length
diff --git a/src/tools/gen_export.pl b/src/tools/gen_export.pl
index d9fdaaaf6d..888c8a197a 100644
--- a/src/tools/gen_export.pl
+++ b/src/tools/gen_export.pl
@@ -16,11 +16,12 @@ GetOptions(
 	'input:s' => \$input,
 	'output:s' => \$output) or die "wrong arguments";
 
-if (not(   $format eq 'darwin'
+if (not(   $format eq 'aix'
+		or $format eq 'darwin'
 		or $format eq 'gnu'
 		or $format eq 'win'))
 {
-	die "$0: $format is not yet handled (only darwin, gnu, win are)\n";
+	die "$0: $format is not yet handled (only aix, darwin, gnu, win are)\n";
 }
 
 open(my $input_handle, '<', $input)
@@ -55,7 +56,11 @@ while (<$input_handle>)
 	}
 	elsif (/^(\S+)\s+(\S+)/)
 	{
-		if ($format eq 'darwin')
+		if ($format eq 'aix')
+		{
+			print $output_handle "$1\n";
+		}
+		elsif ($format eq 'darwin')
 		{
 			print $output_handle "_$1\n";
 		}
diff --git a/src/tools/pginclude/headerscheck b/src/tools/pginclude/headerscheck
index 4a157d0a5f..cfd8c6896c 100755
--- a/src/tools/pginclude/headerscheck
+++ b/src/tools/pginclude/headerscheck
@@ -85,6 +85,7 @@ do
 
 	# These files are platform-specific, and c.h will include the
 	# one that's relevant for our current platform anyway.
+	test "$f" = src/include/port/aix.h && continue
 	test "$f" = src/include/port/cygwin.h && continue
 	test "$f" = src/include/port/darwin.h && continue
 	test "$f" = src/include/port/freebsd.h && continue
-- 
2.41.0

From f8260d015857d3a65292e55f08ec3a13b60f00b3 Mon Sep 17 00:00:00 2001
From: Sriram RK <sriram.rk@in.ibm.com>
Date: Mon, 20 May 2024 01:38:59 -0500
Subject: [PATCH 1/1] AIX support, revert the changes from 0b16bb8776bb8. Trim
 AIX/XLC changes to support gcc only.

 - Review comments from Heikki.
 - Replace tas() AIX asm with gcc __sync_lock_test_and_set().
 - Fix tas() for powerPC.
 - Include only AIX specific changes in s_lock.h
---
 Makefile                                      |   2 -
 configure                                     |  37 +++---
 configure.ac                                  |  28 ++---
 doc/src/sgml/dfunc.sgml                       |  19 +++
 doc/src/sgml/installation.sgml                | 118 +++++++++++++++++-
 doc/src/sgml/runtime.sgml                     |  23 ++++
 meson.build                                   |  57 +++++----
 src/Makefile.shlib                            |  29 +++++
 src/backend/Makefile                          |  20 +++
 src/backend/meson.build                       |  15 +++
 src/backend/port/aix/mkldexport.sh            |  61 +++++++++
 src/backend/utils/error/elog.c                |   2 +
 src/backend/utils/misc/ps_status.c            |   4 +-
 src/bin/pg_basebackup/t/010_pg_basebackup.pl  |   3 +-
 src/bin/pg_verifybackup/t/008_untar.pl        |   3 +-
 src/bin/pg_verifybackup/t/010_client_untar.pl |   3 +-
 src/include/c.h                               |   4 +-
 src/include/port/aix.h                        |   6 +
 src/include/storage/s_lock.h                  |  25 +++-
 src/interfaces/libpq/Makefile                 |   2 +-
 src/interfaces/libpq/meson.build              |   5 +-
 src/makefiles/Makefile.aix                    |  39 ++++++
 src/port/README                               |   2 +-
 src/port/strerror.c                           |   2 +
 src/template/aix                              |  14 +++
 src/test/regress/Makefile                     |   5 +
 src/test/regress/expected/sanity_check.out    |  29 +++++
 src/test/regress/expected/test_setup.out      |   4 +
 src/test/regress/regress.c                    |  40 ++++++
 src/test/regress/sql/sanity_check.sql         |  26 ++++
 src/test/regress/sql/test_setup.sql           |   5 +
 src/tools/gen_export.pl                       |  11 +-
 src/tools/pginclude/headerscheck              |   1 +
 33 files changed, 555 insertions(+), 89 deletions(-)
 create mode 100755 src/backend/port/aix/mkldexport.sh
 create mode 100644 src/include/port/aix.h
 create mode 100644 src/makefiles/Makefile.aix
 create mode 100644 src/template/aix

diff --git a/Makefile b/Makefile
index 8a2ec9396b..9bc1a4ec17 100644
--- a/Makefile
+++ b/Makefile
@@ -13,8 +13,6 @@
 
 # AIX make defaults to building *every* target of the first rule.  Start with
 # a single-target, empty rule to make the other targets non-default.
-# (We don't support AIX anymore, but if someone tries to build on AIX anyway,
-# at least they'll get the instructions to run 'configure' first.)
 all:
 
 all check install installdirs installcheck installcheck-parallel uninstall clean distclean maintainer-clean dist distcheck world check-world install-world installcheck-world:
diff --git a/configure b/configure
index 89644f2249..f218b2e040 100755
--- a/configure
+++ b/configure
@@ -2988,6 +2988,7 @@ else
 # --with-template not given
 
 case $host_os in
+     aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -6848,7 +6849,6 @@ if test x"$pgac_cv_prog_CXX_cxxflags__fno_strict_aliasing" = x"yes"; then
   CXXFLAGS="${CXXFLAGS} -fno-strict-aliasing"
 fi
 
-
 fi
 
 # If the compiler knows how to hide symbols, add the switch needed for that to
@@ -12860,7 +12860,8 @@ fi
 
 fi
 
-# Note: We can test for libldap_r only after we know PTHREAD_LIBS
+# Note: We can test for libldap_r only after we know PTHREAD_LIBS;
+# also, on AIX, we may need to have openssl in LIBS for this step.
 if test "$with_ldap" = yes ; then
   _LIBS="$LIBS"
   if test "$PORTNAME" != "win32"; then
@@ -16951,28 +16952,18 @@ _ACEOF
 
 
 # Compute maximum alignment of any basic type.
-#
-# We require 'double' to have the strictest alignment among the basic types,
-# because otherwise the C ABI might impose 8-byte alignment on some of the
-# other C types that correspond to TYPALIGN_DOUBLE SQL types.  That could
-# cause a mismatch between the tuple layout and the C struct layout of a
-# catalog tuple.  We used to carefully order catalog columns such that any
-# fixed-width, attalign=4 columns were at offsets divisible by 8 regardless
-# of MAXIMUM_ALIGNOF to avoid that, but we no longer support any platforms
-# where TYPALIGN_DOUBLE != MAXIMUM_ALIGNOF.
-#
-# We assume without checking that long's alignment is at least as strong as
-# char, short, or int.  Note that we intentionally do not consider any types
-# wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
-# much of a penalty for disk and memory space.
-
-MAX_ALIGNOF=$ac_cv_alignof_double
+# We assume long's alignment is at least as strong as char, short, or int;
+# but we must check long long (if it is being used for int64) and double.
+# Note that we intentionally do not consider any types wider than 64 bits,
+# as allowing MAXIMUM_ALIGNOF to exceed 8 would be too much of a penalty
+# for disk and memory space.
 
-if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
+MAX_ALIGNOF=$ac_cv_alignof_long
+if test $MAX_ALIGNOF -lt $ac_cv_alignof_double ; then
+  MAX_ALIGNOF=$ac_cv_alignof_double
 fi
-if test x"$HAVE_LONG_LONG_INT_64" = xyes && test $ac_cv_alignof_long_long_int -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'long long int' is greater than the alignment of 'double'" "$LINENO" 5
+if test x"$HAVE_LONG_LONG_INT_64" = xyes && test $MAX_ALIGNOF -lt $ac_cv_alignof_long_long_int ; then
+  MAX_ALIGNOF="$ac_cv_alignof_long_long_int"
 fi
 
 cat >>confdefs.h <<_ACEOF
@@ -17090,7 +17081,7 @@ else
 /* end confdefs.h.  */
 
 /* This must match the corresponding code in c.h: */
-#if defined(__GNUC__) || defined(__SUNPRO_C)
+#if defined(__GNUC__) || defined(__SUNPRO_C) || defined(__IBMC__)
 #define pg_attribute_aligned(a) __attribute__((aligned(a)))
 #elif defined(_MSC_VER)
 #define pg_attribute_aligned(a) __declspec(align(a))
diff --git a/configure.ac b/configure.ac
index c7322e292c..a059509cd9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -62,6 +62,7 @@ PGAC_ARG_REQ(with, template, [NAME], [override operating system template],
 # --with-template not given
 
 case $host_os in
+     aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -1385,7 +1386,8 @@ if test "$with_zstd" = yes ; then
   AC_CHECK_LIB(zstd, ZSTD_compress, [], [AC_MSG_ERROR([library 'zstd' is required for ZSTD support])])
 fi
 
-# Note: We can test for libldap_r only after we know PTHREAD_LIBS
+# Note: We can test for libldap_r only after we know PTHREAD_LIBS;
+# also, on AIX, we may need to have openssl in LIBS for this step.
 if test "$with_ldap" = yes ; then
   _LIBS="$LIBS"
   if test "$PORTNAME" != "win32"; then
@@ -1643,8 +1645,9 @@ PGAC_TYPE_LOCALE_T
 # spelling it understands, because it conflicts with
 # __declspec(restrict). Therefore we define pg_restrict to the
 # appropriate definition, which presumably won't conflict.
+#
 AC_C_RESTRICT
-if test "$ac_cv_c_restrict" = "no"; then
+if test "$ac_cv_c_restrict" = "no" ; then
   pg_restrict=""
 else
   pg_restrict="$ac_cv_c_restrict"
@@ -1996,22 +1999,11 @@ fi
 AC_CHECK_ALIGNOF(double)
 
 # Compute maximum alignment of any basic type.
-#
-# We require 'double' to have the strictest alignment among the basic types,
-# because otherwise the C ABI might impose 8-byte alignment on some of the
-# other C types that correspond to TYPALIGN_DOUBLE SQL types.  That could
-# cause a mismatch between the tuple layout and the C struct layout of a
-# catalog tuple.  We used to carefully order catalog columns such that any
-# fixed-width, attalign=4 columns were at offsets divisible by 8 regardless
-# of MAXIMUM_ALIGNOF to avoid that, but we no longer support any platforms
-# where TYPALIGN_DOUBLE != MAXIMUM_ALIGNOF.
-#
-# We assume without checking that long's alignment is at least as strong as
-# char, short, or int.  Note that we intentionally do not consider any types
-# wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
-# much of a penalty for disk and memory space.
-
-MAX_ALIGNOF=$ac_cv_alignof_double
+# We assume long's alignment is at least as strong as char, short, or int;
+# but we must check long long (if it is being used for int64) and double.
+# Note that we intentionally do not consider any types wider than 64 bits,
+# as allowing MAXIMUM_ALIGNOF to exceed 8 would be too much of a penalty
+# for disk and memory space.
 
 if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
   AC_MSG_ERROR([alignment of 'long' is greater than the alignment of 'double'])
diff --git a/doc/src/sgml/dfunc.sgml b/doc/src/sgml/dfunc.sgml
index b94aefcd0c..554f9fac4c 100644
--- a/doc/src/sgml/dfunc.sgml
+++ b/doc/src/sgml/dfunc.sgml
@@ -202,4 +202,23 @@ gcc -G -o foo.so foo.o
   server expects to find the shared library files.
  </para>
 
+<!--
+Under AIX, object files are compiled normally but building the shared
+library requires a couple of steps.  First, create the object file:
+.nf
+cc <other flags> -c foo.c
+.fi
+You must then create a symbol \*(lqexports\*(rq file for the object
+file:
+.nf
+mkldexport foo.o `pwd` &gt; foo.exp
+.fi
+Finally, you can create the shared library:
+.nf
+ld <other flags> -H512 -T512 -o foo.so -e _nostart \e
+   -bI:.../lib/postgres.exp -bE:foo.exp foo.o \e
+   -lm -lc 2>/dev/null
+.fi
+  -->
+
 </sect2>
diff --git a/doc/src/sgml/installation.sgml b/doc/src/sgml/installation.sgml
index 1b32d5ca62..60e9a34a03 100644
--- a/doc/src/sgml/installation.sgml
+++ b/doc/src/sgml/installation.sgml
@@ -3401,7 +3401,7 @@ export MANPATH
   <para>
    <productname>PostgreSQL</productname> can be expected to work on current
    versions of these operating systems: Linux, Windows,
-   FreeBSD, OpenBSD, NetBSD, DragonFlyBSD, macOS, Solaris, and illumos.
+   FreeBSD, OpenBSD, NetBSD, DragonFlyBSD, macOS, AIX, Solaris, and illumos.
    Other Unix-like systems may also work but are not currently
    being tested.  In most cases, all CPU architectures supported by
    a given operating system will work.  Look in
@@ -3445,6 +3445,122 @@ export MANPATH
    installation issues.
   </para>
 
+  <sect2 id="installation-notes-aix">
+   <title>AIX</title>
+
+   <indexterm zone="installation-notes-aix">
+    <primary>AIX</primary>
+    <secondary>installation on</secondary>
+   </indexterm>
+
+   <para>
+    You can use GCC to build <productname>PostgreSQL</productname>
+    on <productname>AIX</productname>.
+   </para>
+
+   <para>
+    <productname>AIX</productname> versions before 7.1 are no longer
+    tested nor supported by the <productname>PostgreSQL</productname>
+    community.
+   </para>
+
+   <sect3 id="installation-notes-aix-mem-management">
+    <title>Memory Management</title>
+    <!-- https://archives.postgresql.org/message-id/603bgqmpl9.fsf@dba2.int.libertyrms.com -->
+
+    <para>
+     AIX can be somewhat peculiar with regards to the way it does
+     memory management.  You can have a server with many multiples of
+     gigabytes of RAM free, but still get out of memory or address
+     space errors when running applications.  One example
+     is loading of extensions failing with unusual errors.
+     For example, running as the owner of the PostgreSQL installation:
+<screen>
+=# CREATE EXTENSION plperl;
+ERROR:  could not load library "/opt/dbs/pgsql/lib/plperl.so": A memory address is not in the address space for the process.
+</screen>
+    Running as a non-owner in the group possessing the PostgreSQL
+    installation:
+<screen>
+=# CREATE EXTENSION plperl;
+ERROR:  could not load library "/opt/dbs/pgsql/lib/plperl.so": Bad address
+</screen>
+     Another example is out of memory errors in the PostgreSQL server
+     logs, with every memory allocation near or greater than 256 MB
+     failing.
+    </para>
+
+    <para>
+     The overall cause of all these problems is the default bittedness
+     and memory model used by the server process.  By default, all
+     binaries built on AIX are 32-bit.  This does not depend upon
+     hardware type or kernel in use.  These 32-bit processes are
+     limited to 4 GB of memory laid out in 256 MB segments using one
+     of a few models.  The default allows for less than 256 MB in the
+     heap as it shares a single segment with the stack.
+    </para>
+
+    <para>
+     In the case of the <literal>plperl</literal> example, above,
+     check your umask and the permissions of the binaries in your
+     PostgreSQL installation.  The binaries involved in that example
+     were 32-bit and installed as mode 750 instead of 755.  Due to the
+     permissions being set in this fashion, only the owner or a member
+     of the possessing group can load the library.  Since it isn't
+     world-readable, the loader places the object into the process'
+     heap instead of the shared library segments where it would
+     otherwise be placed.
+    </para>
+
+    <para>
+     The <quote>ideal</quote> solution for this is to use a 64-bit
+     build of PostgreSQL, but that is not always practical, because
+     systems with 32-bit processors can build, but not run, 64-bit
+     binaries.
+    </para>
+
+    <para>
+     If a 32-bit binary is desired, set <symbol>LDR_CNTRL</symbol> to
+     <literal>MAXDATA=0x<replaceable>n</replaceable>0000000</literal>,
+     where 1 &lt;= n &lt;= 8, before starting the PostgreSQL server,
+     and try different values and <filename>postgresql.conf</filename>
+     settings to find a configuration that works satisfactorily.  This
+     use of <symbol>LDR_CNTRL</symbol> tells AIX that you want the
+     server to have <symbol>MAXDATA</symbol> bytes set aside for the
+     heap, allocated in 256 MB segments.  When you find a workable
+     configuration,
+     <command>ldedit</command> can be used to modify the binaries so
+     that they default to using the desired heap size.  PostgreSQL can
+     also be rebuilt, passing <literal>configure
+     LDFLAGS="-Wl,-bmaxdata:0x<replaceable>n</replaceable>0000000"</literal>
+     to achieve the same effect.
+    </para>
+
+    <para>
+     For a 64-bit build, set <envar>OBJECT_MODE</envar> to 64 and
+     pass <literal>CC="gcc -maix64"</literal>
+     and <literal>LDFLAGS="-Wl,-bbigtoc"</literal>
+     to <command>configure</command>. 
+     If you omit the export of
+    <envar>OBJECT_MODE</envar>, your build may fail with linker errors.  When
+    <envar>OBJECT_MODE</envar> is set, it tells AIX's build utilities
+    such as <command>ar</command>, <command>as</command>, and <command>ld</command> what
+    type of objects to default to handling.
+    </para>
+
+    <para>
+     By default, overcommit of paging space can happen.  While we have
+     not seen this occur, AIX will kill processes when it runs out of
+     memory and the overcommit is accessed.  The closest to this that
+     we have seen is fork failing because the system decided that
+     there was not enough memory for another process.  Like many other
+     parts of AIX, the paging space allocation method and
+     out-of-memory kill is configurable on a system- or process-wide
+     basis if this becomes a problem.
+    </para>
+   </sect3>
+  </sect2>
+
   <sect2 id="installation-notes-cygwin">
    <title>Cygwin</title>
 
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index 6047b8171d..64753d9c01 100644
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -891,6 +891,29 @@ psql: error: connection to server on socket "/tmp/.s.PGSQL.5432" failed: No such
 
 
     <variablelist>
+     <varlistentry>
+      <term><systemitem class="osname">AIX</systemitem>
+      <indexterm><primary>AIX</primary><secondary>IPC configuration</secondary></indexterm>
+      </term>
+      <listitem>
+       <para>
+        It should not be necessary to do
+        any special configuration for such parameters as
+        <varname>SHMMAX</varname>, as it appears this is configured to
+        allow all memory to be used as shared memory.  That is the
+        sort of configuration commonly used for other databases such
+        as <application>DB/2</application>.</para>
+
+       <para> It might, however, be necessary to modify the global
+       <command>ulimit</command> information in
+       <filename>/etc/security/limits</filename>, as the default hard
+       limits for file sizes (<varname>fsize</varname>) and numbers of
+       files (<varname>nofiles</varname>) might be too low.
+       </para>
+      </listitem>
+     </varlistentry>
+
+
      <varlistentry>
       <term><systemitem class="osname">FreeBSD</systemitem>
       <indexterm><primary>FreeBSD</primary><secondary>IPC configuration</secondary></indexterm>
diff --git a/meson.build b/meson.build
index 1c0579d5a6..f1ac154cdc 100644
--- a/meson.build
+++ b/meson.build
@@ -196,7 +196,26 @@ endif
 # that purpose.
 portname = host_system
 
-if host_system == 'cygwin'
+if host_system == 'aix'
+  library_path_var = 'LIBPATH'
+
+  export_file_format = 'aix'
+  export_fmt = '-Wl,-bE:@0@'
+  mod_link_args_fmt = ['-Wl,-bI:@0@']
+  mod_link_with_dir = 'libdir'
+  mod_link_with_name = '@0@.imp'
+
+  # M:SRE sets a flag indicating that an object is a shared library. Seems to
+  # work in some circumstances without, but required in others.
+  ldflags_sl += '-Wl,-bM:SRE'
+  ldflags_be += '-Wl,-brtllib'
+
+  # Native memset() is faster, tested on:
+  # - AIX 5.1 and 5.2, XLC 6.0 (IBM's cc)
+  # - AIX 5.3 ML3, gcc 4.0.1
+  memset_loop_limit = 0
+
+elif host_system == 'cygwin'
   sema_kind = 'unnamed_posix'
   cppflags += '-D_GNU_SOURCE'
   dlsuffix = '.dll'
@@ -1490,11 +1509,11 @@ sizeof_long = cc.sizeof('long', args: test_c_args)
 cdata.set('SIZEOF_LONG', sizeof_long)
 if sizeof_long == 8
   cdata.set('HAVE_LONG_INT_64', 1)
-  pg_int64_type = 'long int'
+  cdata.set('PG_INT64_TYPE', 'long int')
   cdata.set_quoted('INT64_MODIFIER', 'l')
 elif sizeof_long == 4 and cc.sizeof('long long', args: test_c_args) == 8
   cdata.set('HAVE_LONG_LONG_INT_64', 1)
-  pg_int64_type = 'long long int'
+  cdata.set('PG_INT64_TYPE', 'long long int')
   cdata.set_quoted('INT64_MODIFIER', 'll')
 else
   error('do not know how to get a 64bit int')
@@ -1508,31 +1527,15 @@ endif
 # Determine memory alignment requirements for the basic C data types.
 
 alignof_types = ['short', 'int', 'long', 'double']
+maxalign = 0
 foreach t : alignof_types
   align = cc.alignment(t, args: test_c_args)
+  if maxalign < align
+    maxalign = align
+  endif
   cdata.set('ALIGNOF_@0@'.format(t.to_upper()), align)
 endforeach
-
-# Compute maximum alignment of any basic type.
-#
-# We require 'double' to have the strictest alignment among the basic types,
-# because otherwise the C ABI might impose 8-byte alignment on some of the
-# other C types that correspond to TYPALIGN_DOUBLE SQL types.  That could
-# cause a mismatch between the tuple layout and the C struct layout of a
-# catalog tuple.  We used to carefully order catalog columns such that any
-# fixed-width, attalign=4 columns were at offsets divisible by 8 regardless
-# of MAXIMUM_ALIGNOF to avoid that, but we no longer support any platforms
-# where TYPALIGN_DOUBLE != MAXIMUM_ALIGNOF.
-#
-# We assume without checking that int64's alignment is at least as strong
-# as long, char, short, or int.  Note that we intentionally do not consider
-# any types wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8
-# would be too much of a penalty for disk and memory space.
-alignof_double = cdata.get('ALIGNOF_DOUBLE')
-if cc.alignment(pg_int64_type, args: test_c_args) > alignof_double
-  error('alignment of int64 is greater than the alignment of double')
-endif
-cdata.set('MAXIMUM_ALIGNOF', alignof_double)
+cdata.set('MAXIMUM_ALIGNOF', maxalign)
 
 cdata.set('SIZEOF_VOID_P', cc.sizeof('void *', args: test_c_args))
 cdata.set('SIZEOF_SIZE_T', cc.sizeof('size_t', args: test_c_args))
@@ -1581,7 +1584,7 @@ if cc.links('''
   if not meson.is_cross_build()
     r = cc.run('''
     /* This must match the corresponding code in c.h: */
-    #if defined(__GNUC__) || defined(__SUNPRO_C)
+    #if defined(__GNUC__) || defined(__SUNPRO_C) || defined(__IBMC__)
     #define pg_attribute_aligned(a) __attribute__((aligned(a)))
     #elif defined(_MSC_VER)
     #define pg_attribute_aligned(a) __declspec(align(a))
@@ -2476,6 +2479,10 @@ endif
 # conflict.
 #
 # We assume C99 support, so we don't need to make this conditional.
+#
+# XXX: Historically we allowed platforms to disable restrict in template
+# files, but that was only added for AIX when building with XLC, which we
+# don't support yet.
 cdata.set('pg_restrict', '__restrict')
 
 
diff --git a/src/Makefile.shlib b/src/Makefile.shlib
index fa81f6ffdd..8ca51ca03f 100644
--- a/src/Makefile.shlib
+++ b/src/Makefile.shlib
@@ -106,6 +106,20 @@ ifdef SO_MAJOR_VERSION
 override CPPFLAGS += -DSO_MAJOR_VERSION=$(SO_MAJOR_VERSION)
 endif
 
+ifeq ($(PORTNAME), aix)
+  LINK.shared		= $(COMPILER)
+  ifdef SO_MAJOR_VERSION
+    shlib		= lib$(NAME)$(DLSUFFIX).$(SO_MAJOR_VERSION)
+  endif
+  haslibarule   = yes
+  # $(exports_file) is also usable as an import file
+  exports_file		= lib$(NAME).exp
+  BUILD.exports		= ( echo '\#! $(shlib)'; $(AWK) '/^[^\#]/ {printf "%s\n",$$1}' $< ) > $@
+  ifneq (,$(SHLIB_EXPORTS))
+    LINK.shared		+= -Wl,-bE:$(exports_file)
+  endif
+endif
+
 ifeq ($(PORTNAME), darwin)
   ifdef soname
     # linkable library
@@ -254,6 +268,14 @@ $(stlib): $(OBJS) | $(SHLIB_PREREQS)
 	touch $@
 endif #haslibarule
 
+# AIX wraps shared libraries inside a static library, can be used both
+# for static and shared linking
+ifeq ($(PORTNAME), aix)
+$(stlib): $(shlib)
+	rm -f $(stlib)
+	$(AR) $(AROPT) $(stlib) $(shlib)
+endif # aix
+
 ifeq (,$(filter cygwin win32,$(PORTNAME)))
 
 # Normal case
@@ -267,8 +289,11 @@ ifneq ($(shlib), $(shlib_major))
 endif
 # Make sure we have a link to a name without any version numbers
 ifneq ($(shlib), $(shlib_bare))
+# except on AIX, where that's not a thing
+ifneq ($(PORTNAME), aix)
 	rm -f $(shlib_bare)
 	$(LN_S) $(shlib) $(shlib_bare)
+endif # aix
 endif # shlib_bare
 endif # shlib_major
 
@@ -376,6 +401,9 @@ install-lib-static: $(stlib) installdirs-lib
 
 install-lib-shared: $(shlib) installdirs-lib
 ifdef soname
+# we don't install $(shlib) on AIX
+# (see http://archives.postgresql.org/message-id/52EF20B2E3209443BC37736D00C3C1380A6E79FE@EXADV1.host.magwien.gv.at)
+ifneq ($(PORTNAME), aix)
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(libdir)/$(shlib)'
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
@@ -391,6 +419,7 @@ ifneq ($(shlib), $(shlib_bare))
 endif
 endif # not win32
 endif # not cygwin
+endif # not aix
 ifneq (,$(findstring $(PORTNAME),win32 cygwin))
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(bindir)/$(shlib)'
 endif
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 6700aec039..954b14962f 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -62,12 +62,14 @@ all: submake-libpgport submake-catalog-headers submake-utils-headers postgres $(
 
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
+ifneq ($(PORTNAME), aix)
 
 postgres: $(OBJS)
 	$(CC) $(CFLAGS) $(call expand_subsys,$^) $(LDFLAGS) $(LIBS) -o $@
 
 endif
 endif
+endif
 
 ifeq ($(PORTNAME), cygwin)
 
@@ -94,6 +96,24 @@ libpostgres.a: postgres
 
 endif # win32
 
+ifeq ($(PORTNAME), aix)
+
+postgres: $(POSTGRES_IMP)
+	$(CC) $(CFLAGS) $(call expand_subsys,$(OBJS)) $(LDFLAGS) -Wl,-bE:$(top_builddir)/src/backend/$(POSTGRES_IMP) $(LIBS) -Wl,-brtllib -o $@
+
+# Linking to a single .o with -r is a lot faster than building a .a or passing
+# all objects to MKLDEXPORT.
+#
+# It looks alluring to use $(CC) -r instead of ld -r, but that doesn't
+# trivially work with gcc, due to gcc specific static libraries linked in with
+# -r.
+$(POSTGRES_IMP): $(OBJS)
+	ld -r -o SUBSYS.o $(call expand_subsys,$^)
+	$(MKLDEXPORT) SUBSYS.o . > $@
+	@rm -f SUBSYS.o
+
+endif # aix
+
 $(top_builddir)/src/port/libpgport_srv.a: | submake-libpgport
 
 
diff --git a/src/backend/meson.build b/src/backend/meson.build
index 436c04af08..8767aaba67 100644
--- a/src/backend/meson.build
+++ b/src/backend/meson.build
@@ -91,6 +91,21 @@ if cc.get_id() == 'msvc'
   # be restricted to b_pch=true.
   backend_link_with += postgres_lib
 
+elif host_system == 'aix'
+  # The '.' argument leads mkldexport.sh to emit "#! .", which refers to the
+  # main executable, allowing extension libraries to resolve their undefined
+  # symbols to symbols in the postgres binary.
+  postgres_imp = custom_target('postgres.imp',
+    command: [files('port/aix/mkldexport.sh'), '@INPUT@', '.'],
+    input: postgres_lib,
+    output: 'postgres.imp',
+    capture: true,
+    install: true,
+    install_dir: dir_lib,
+    build_by_default: false,
+  )
+  backend_link_args += '-Wl,-bE:@0@'.format(postgres_imp.full_path())
+  backend_link_depends += postgres_imp
 endif
 
 backend_input = []
diff --git a/src/backend/port/aix/mkldexport.sh b/src/backend/port/aix/mkldexport.sh
new file mode 100755
index 0000000000..adf3793e86
--- /dev/null
+++ b/src/backend/port/aix/mkldexport.sh
@@ -0,0 +1,61 @@
+#!/bin/sh
+#
+# mkldexport
+#	create an AIX exports file from an object file
+#
+# src/backend/port/aix/mkldexport.sh
+#
+# Usage:
+#	mkldexport objectfile [location]
+# where
+#	objectfile is the current location of the object file.
+#	location is the eventual (installed) location of the
+#		object file (if different from the current
+#		working directory).
+#
+# [This file comes from the Postgres 4.2 distribution. - ay 7/95]
+#
+# Header: /usr/local/devel/postgres/src/tools/mkldexport/RCS/mkldexport.sh,v 1.2 1994/03/13 04:59:12 aoki Exp
+#
+
+# setting this to nm -B might be better
+# ... due to changes in AIX 4.x ...
+# ... let us search in different directories - Gerhard Reithofer
+if [ -x /usr/ucb/nm ]
+then NM=/usr/ucb/nm
+elif [ -x /usr/bin/nm ]
+then NM=/usr/bin/nm
+elif [ -x /usr/ccs/bin/nm ]
+then NM=/usr/ccs/bin/nm
+elif [ -x /usr/usg/bin/nm ]
+then NM=/usr/usg/bin/nm
+else echo "Fatal error: cannot find `nm' ... please check your installation."
+     exit 1
+fi
+
+CMDNAME=`basename $0`
+if [ -z "$1" ]; then
+	echo "Usage: $CMDNAME object [location]"
+	exit 1
+fi
+OBJNAME=`basename $1`
+if [ "`basename $OBJNAME`" != "`basename $OBJNAME .o`" ]; then
+	OBJNAME=`basename $OBJNAME .o`.so
+fi
+if [ -z "$2" ]; then
+	echo '#!'
+else
+	if [ "$2" = "." ]; then
+		# for the base executable (AIX 4.2 and up)
+		echo '#! .'
+	else
+		echo '#!' $2
+	fi
+fi
+$NM -BCg $1 | \
+	egrep ' [TDB] ' | \
+	sed -e 's/.* //' | \
+	egrep -v '\$' | \
+	sed -e 's/^[.]//' | \
+	sort | \
+	uniq
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index d91a85cb2d..7b51e94f4a 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -908,7 +908,9 @@ errcode_for_file_access(void)
 			/* Wrong object type or state */
 		case ENOTDIR:			/* Not a directory */
 		case EISDIR:			/* Is a directory */
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:			/* Directory not empty */
+#endif
 			edata->sqlerrcode = ERRCODE_WRONG_OBJECT_TYPE;
 			break;
 
diff --git a/src/backend/utils/misc/ps_status.c b/src/backend/utils/misc/ps_status.c
index 9da6377402..532eac31b4 100644
--- a/src/backend/utils/misc/ps_status.c
+++ b/src/backend/utils/misc/ps_status.c
@@ -50,7 +50,7 @@ bool		update_process_title = DEFAULT_UPDATE_PROCESS_TITLE;
 #define PS_USE_SETPROCTITLE_FAST
 #elif defined(HAVE_SETPROCTITLE)
 #define PS_USE_SETPROCTITLE
-#elif defined(__linux__) || defined(__sun) || defined(__darwin__)
+#elif defined(__linux__) || defined(_AIX) || defined(__sun) || defined(__darwin__)
 #define PS_USE_CLOBBER_ARGV
 #elif defined(WIN32)
 #define PS_USE_WIN32
@@ -60,7 +60,7 @@ bool		update_process_title = DEFAULT_UPDATE_PROCESS_TITLE;
 
 
 /* Different systems want the buffer padded differently */
-#if defined(__linux__) || defined(__darwin__)
+#if defined(_AIX) || defined(__linux__) || defined(__darwin__)
 #define PS_PADDING '\0'
 #else
 #define PS_PADDING ' '
diff --git a/src/bin/pg_basebackup/t/010_pg_basebackup.pl b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
index 2d4b75a6fe..ce936959c1 100644
--- a/src/bin/pg_basebackup/t/010_pg_basebackup.pl
+++ b/src/bin/pg_basebackup/t/010_pg_basebackup.pl
@@ -401,7 +401,8 @@ SKIP:
 {
 	my $tar = $ENV{TAR};
 	# don't check for a working tar here, to accommodate various odd
-	# cases. If tar doesn't work the init_from_backup below will fail.
+	# cases such as AIX. If tar doesn't work the init_from_backup below
+	# will fail.
 	skip "no tar program available", 1
 	  if (!defined $tar || $tar eq '');
 
diff --git a/src/bin/pg_verifybackup/t/008_untar.pl b/src/bin/pg_verifybackup/t/008_untar.pl
index 7a09f3b75b..30d9f3f7f0 100644
--- a/src/bin/pg_verifybackup/t/008_untar.pl
+++ b/src/bin/pg_verifybackup/t/008_untar.pl
@@ -104,7 +104,8 @@ for my $tc (@test_configuration)
 		{
 			my $tar = $ENV{TAR};
 			# don't check for a working tar here, to accommodate various odd
-			# cases. If tar doesn't work the init_from_backup below will fail.
+			# cases such as AIX. If tar doesn't work the init_from_backup below
+			# will fail.
 			skip "no tar program available", 1
 			  if (!defined $tar || $tar eq '');
 
diff --git a/src/bin/pg_verifybackup/t/010_client_untar.pl b/src/bin/pg_verifybackup/t/010_client_untar.pl
index 8c076d46de..45010d79ac 100644
--- a/src/bin/pg_verifybackup/t/010_client_untar.pl
+++ b/src/bin/pg_verifybackup/t/010_client_untar.pl
@@ -134,7 +134,8 @@ for my $tc (@test_configuration)
 		{
 			my $tar = $ENV{TAR};
 			# don't check for a working tar here, to accommodate various odd
-			# cases. If tar doesn't work the init_from_backup below will fail.
+			# cases such as AIX. If tar doesn't work the init_from_backup below
+			# will fail.
 			skip "no tar program available", 1
 			  if (!defined $tar || $tar eq '');
 
diff --git a/src/include/c.h b/src/include/c.h
index dc1841346c..641cd9bdf1 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -182,7 +182,7 @@
 #define PG_USED_FOR_ASSERTS_ONLY pg_attribute_unused()
 #endif
 
-/* GCC supports format attributes */
+/* GCC support format attributes */
 #if defined(__GNUC__)
 #define pg_attribute_format_arg(a) __attribute__((format_arg(a)))
 #define pg_attribute_printf(f,a) __attribute__((format(PG_PRINTF_ATTRIBUTE, f, a)))
@@ -192,7 +192,7 @@
 #endif
 
 /* GCC and Sunpro support aligned, packed and noreturn */
-#if defined(__GNUC__) || defined(__SUNPRO_C)
+#if defined(__GNUC__) || defined(__SUNPRO_C) 
 #define pg_attribute_aligned(a) __attribute__((aligned(a)))
 #define pg_attribute_noreturn() __attribute__((noreturn))
 #define pg_attribute_packed() __attribute__((packed))
diff --git a/src/include/port/aix.h b/src/include/port/aix.h
new file mode 100644
index 0000000000..1c2d166791
--- /dev/null
+++ b/src/include/port/aix.h
@@ -0,0 +1,6 @@
+/*
+ * src/include/port/aix.h
+ */
+#define CLASS_CONFLICT
+#define DISABLE_XOPEN_NLS
+
diff --git a/src/include/storage/s_lock.h b/src/include/storage/s_lock.h
index 29ac6cdcd9..2f6eb5df2a 100644
--- a/src/include/storage/s_lock.h
+++ b/src/include/storage/s_lock.h
@@ -424,17 +424,15 @@ tas(volatile slock_t *lock)
 	__asm__ __volatile__(
 "	lwarx   %0,0,%3,1	\n"
 "	cmpwi   %0,0		\n"
-"	bne     1f			\n"
+"	bne     $+16		\n"		/* branch to li %1,1 */
 "	addi    %0,%0,1		\n"
 "	stwcx.  %0,0,%3		\n"
-"	beq     2f			\n"
-"1: \n"
+"	beq     $+12		\n"		/* branch to lwsync */
 "	li      %1,1		\n"
-"	b       3f			\n"
-"2: \n"
+"	b       $+12		\n"		/* branch to end of asm sequence */
 "	lwsync				\n"
 "	li      %1,0		\n"
-"3: \n"
+
 :	"=&b"(_t), "=r"(_res), "+m"(*lock)
 :	"r"(lock)
 :	"memory", "cc");
@@ -662,6 +660,21 @@ tas(volatile slock_t *lock)
 
 #if !defined(HAS_TEST_AND_SET)	/* We didn't trigger above, let's try here */
 
+#if defined(_AIX)	/* AIX */
+/*
+ * AIX (POWER)
+ */
+#define HAS_TEST_AND_SET
+
+#include <sys/atomic_op.h>
+
+typedef int slock_t;
+
+#define TAS(lock)			_check_lock((slock_t *) (lock), 0, 1)
+#define S_UNLOCK(lock)		_clear_lock((slock_t *) (lock), 0)
+#endif	 /* _AIX */
+
+
 /* These are in sunstudio_(sparc|x86).s */
 
 #if defined(__SUNPRO_C) && (defined(__i386) || defined(__x86_64__) || defined(__sparc__) || defined(__sparc))
diff --git a/src/interfaces/libpq/Makefile b/src/interfaces/libpq/Makefile
index b36a765764..154429d4d1 100644
--- a/src/interfaces/libpq/Makefile
+++ b/src/interfaces/libpq/Makefile
@@ -114,7 +114,7 @@ backend_src = $(top_srcdir)/src/backend
 # coding rule.
 libpq-refs-stamp: $(shlib)
 ifneq ($(enable_coverage), yes)
-ifeq (,$(filter solaris,$(PORTNAME)))
+ifeq (,$(filter aix solaris,$(PORTNAME)))
 	@if nm -A -u $< 2>/dev/null | grep -v -e __cxa_atexit -e __tsan_func_exit | grep exit; then \
 		echo 'libpq must not be calling any function which invokes exit'; exit 1; \
 	fi
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index ed2a4048d1..7e2017daf0 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -54,8 +54,9 @@ libpq_c_args = ['-DSO_MAJOR_VERSION=5']
 #    libpq_st, and {pgport,common}_shlib for libpq_sh
 #
 # We could try to avoid building the source files twice, but it probably adds
-# more complexity than its worth (reusing object files requires also linking
-# to the library on windows or breaks precompiled headers).
+# more complexity than its worth (AIX doesn't support link_whole yet, reusing
+# object files requires also linking to the library on windows or breaks
+# precompiled headers).
 libpq_st = static_library('libpq',
   libpq_sources,
   include_directories: [libpq_inc],
diff --git a/src/makefiles/Makefile.aix b/src/makefiles/Makefile.aix
new file mode 100644
index 0000000000..dd16a7a037
--- /dev/null
+++ b/src/makefiles/Makefile.aix
@@ -0,0 +1,39 @@
+# MAKE_EXPORTS is required for svr4 loaders that want a file of
+# symbol names to tell them what to export/import.
+MAKE_EXPORTS= true
+
+# -blibpath must contain ALL directories where we should look for libraries
+libpath := $(shell echo $(subst -L,:,$(filter -L/%,$(LDFLAGS))) | sed -e's/ //g'):/usr/lib:/lib
+
+# when building with gcc, need to make sure that libgcc can be found
+ifeq ($(GCC), yes)
+libpath := $(libpath):$(dir $(shell gcc -print-libgcc-file-name))
+endif
+
+rpath = -Wl,-blibpath:'$(rpathdir)$(libpath)'
+
+LDFLAGS_SL += -Wl,-bnoentry -Wl,-H512 -Wl,-bM:SRE
+
+# gcc needs to know it's building a shared lib, otherwise it'll not emit
+# correct code / link to the right support libraries
+ifeq ($(GCC), yes)
+LDFLAGS_SL += -shared
+endif
+
+# env var name to use in place of LD_LIBRARY_PATH
+ld_library_path_var = LIBPATH
+
+
+POSTGRES_IMP= postgres.imp
+
+ifdef PGXS
+BE_DLLLIBS= -Wl,-bI:$(pkglibdir)/$(POSTGRES_IMP)
+else
+BE_DLLLIBS= -Wl,-bI:$(top_builddir)/src/backend/$(POSTGRES_IMP)
+endif
+
+MKLDEXPORT_DIR=src/backend/port/aix
+MKLDEXPORT=$(top_srcdir)/$(MKLDEXPORT_DIR)/mkldexport.sh
+
+%$(DLSUFFIX): %.o
+	$(CC) $(CFLAGS) $*.o $(LDFLAGS) $(LDFLAGS_SL) -o $@ $(BE_DLLLIBS)
diff --git a/src/port/README b/src/port/README
index ed5c54a72f..97f18a6233 100644
--- a/src/port/README
+++ b/src/port/README
@@ -28,5 +28,5 @@ applications.
 from libpgport are linked first.  This avoids having applications
 dependent on symbols that are _used_ by libpq, but not intended to be
 exported by libpq.  libpq's libpgport usage changes over time, so such a
-dependency is a problem.  Windows, Linux, and macOS use an export
+dependency is a problem.  Windows, Linux, AIX, and macOS use an export
 list to control the symbols exported by libpq.
diff --git a/src/port/strerror.c b/src/port/strerror.c
index 4918ba821c..1070a49802 100644
--- a/src/port/strerror.c
+++ b/src/port/strerror.c
@@ -214,8 +214,10 @@ get_errno_symbol(int errnum)
 			return "ENOTCONN";
 		case ENOTDIR:
 			return "ENOTDIR";
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:
 			return "ENOTEMPTY";
+#endif
 		case ENOTSOCK:
 			return "ENOTSOCK";
 #ifdef ENOTSUP
diff --git a/src/template/aix b/src/template/aix
new file mode 100644
index 0000000000..0a788676c0
--- /dev/null
+++ b/src/template/aix
@@ -0,0 +1,14 @@
+# src/template/aix
+
+  # Due to a compiler bug, see 20171013023536.GA492146@rfd.leadboat.com for details,
+  # force restrict not to be used when compiling with xlc.
+#  FORCE_DISABLE_RESTRICT=yes
+#fi
+
+# Extra CFLAGS for code that will go into a shared library
+CFLAGS_SL=""
+
+# Native memset() is faster, tested on:
+# 	AIX 5.1 and 5.2, XLC 6.0 (IBM's cc)
+# 	AIX 5.3 ML3, gcc 4.0.1
+MEMSET_LOOP_LIMIT=0
diff --git a/src/test/regress/Makefile b/src/test/regress/Makefile
index 6409a485e8..7c665ff892 100644
--- a/src/test/regress/Makefile
+++ b/src/test/regress/Makefile
@@ -7,6 +7,11 @@
 # GNU make uses a make file named "GNUmakefile" in preference to "Makefile"
 # if it exists.  Postgres is shipped with a "GNUmakefile".
 
+
+# AIX make defaults to building *every* target of the first rule.  Start with
+# a single-target, empty rule to make the other targets non-default.
+all:
+
 all install clean check installcheck:
 	@echo "You must use GNU make to use Postgres.  It may be installed"
 	@echo "on your system with the name 'gmake'."
diff --git a/src/test/regress/expected/sanity_check.out b/src/test/regress/expected/sanity_check.out
index 8370c1561c..c5c675b750 100644
--- a/src/test/regress/expected/sanity_check.out
+++ b/src/test/regress/expected/sanity_check.out
@@ -25,3 +25,32 @@ SELECT relname, relkind
 ---------+---------
 (0 rows)
 
+--
+-- When ALIGNOF_DOUBLE==4 (e.g. AIX), the C ABI may impose 8-byte alignment on
+-- some of the C types that correspond to TYPALIGN_DOUBLE SQL types.  To ensure
+-- catalog C struct layout matches catalog tuple layout, arrange for the tuple
+-- offset of each fixed-width, attalign='d' catalog column to be divisible by 8
+-- unconditionally.  Keep such columns before the first NameData column of the
+-- catalog, since packagers can override NAMEDATALEN to an odd number.
+--
+WITH check_columns AS (
+ SELECT relname, attname,
+  array(
+   SELECT t.oid
+    FROM pg_type t JOIN pg_attribute pa ON t.oid = pa.atttypid
+    WHERE pa.attrelid = a.attrelid AND
+          pa.attnum > 0 AND pa.attnum < a.attnum
+    ORDER BY pa.attnum) AS coltypes
+ FROM pg_attribute a JOIN pg_class c ON c.oid = attrelid
+  JOIN pg_namespace n ON c.relnamespace = n.oid
+ WHERE attalign = 'd' AND relkind = 'r' AND
+  attnotnull AND attlen <> -1 AND n.nspname = 'pg_catalog'
+)
+SELECT relname, attname, coltypes, get_columns_length(coltypes)
+ FROM check_columns
+ WHERE get_columns_length(coltypes) % 8 != 0 OR
+       'name'::regtype::oid = ANY(coltypes);
+ relname | attname | coltypes | get_columns_length 
+---------+---------+----------+--------------------
+(0 rows)
+
diff --git a/src/test/regress/expected/test_setup.out b/src/test/regress/expected/test_setup.out
index 3d0eeec996..5d9e6bf12b 100644
--- a/src/test/regress/expected/test_setup.out
+++ b/src/test/regress/expected/test_setup.out
@@ -209,6 +209,10 @@ CREATE FUNCTION ttdummy ()
     RETURNS trigger
     AS :'regresslib'
     LANGUAGE C;
+CREATE FUNCTION get_columns_length(oid[])
+    RETURNS int
+    AS :'regresslib'
+    LANGUAGE C STRICT STABLE PARALLEL SAFE;
 -- Use hand-rolled hash functions and operator classes to get predictable
 -- result on different machines.  The hash function for int4 simply returns
 -- the sum of the values passed to it and the one for text returns the length
diff --git a/src/test/regress/regress.c b/src/test/regress/regress.c
index deffaea578..cc633864d7 100644
--- a/src/test/regress/regress.c
+++ b/src/test/regress/regress.c
@@ -1221,3 +1221,43 @@ binary_coercible(PG_FUNCTION_ARGS)
 
 	PG_RETURN_BOOL(IsBinaryCoercible(srctype, targettype));
 }
+
+/*
+ * Return the length of the portion of a tuple consisting of the given array
+ * of data types.  The input data types must be fixed-length data types.
+ */
+PG_FUNCTION_INFO_V1(get_columns_length);
+Datum
+get_columns_length(PG_FUNCTION_ARGS)
+{
+	ArrayType  *ta = PG_GETARG_ARRAYTYPE_P(0);
+	Oid		   *type_oids;
+	int			ntypes;
+	int			column_offset = 0;
+
+	if (ARR_HASNULL(ta) && array_contains_nulls(ta))
+		elog(ERROR, "argument must not contain nulls");
+
+	if (ARR_NDIM(ta) > 1)
+		elog(ERROR, "argument must be empty or one-dimensional array");
+
+	type_oids = (Oid *) ARR_DATA_PTR(ta);
+	ntypes = ArrayGetNItems(ARR_NDIM(ta), ARR_DIMS(ta));
+	for (int i = 0; i < ntypes; i++)
+	{
+		Oid			typeoid = type_oids[i];
+		int16		typlen;
+		bool		typbyval;
+		char		typalign;
+
+		get_typlenbyvalalign(typeoid, &typlen, &typbyval, &typalign);
+
+		/* the data type must be fixed-length */
+		if (typlen < 0)
+			elog(ERROR, "type %u is not fixed-length data type", typeoid);
+
+		column_offset = att_align_nominal(column_offset + typlen, typalign);
+	}
+
+	PG_RETURN_INT32(column_offset);
+}
diff --git a/src/test/regress/sql/sanity_check.sql b/src/test/regress/sql/sanity_check.sql
index 162e5324b5..7f338d191c 100644
--- a/src/test/regress/sql/sanity_check.sql
+++ b/src/test/regress/sql/sanity_check.sql
@@ -19,3 +19,29 @@ SELECT relname, relkind
   FROM pg_class
  WHERE relkind IN ('v', 'c', 'f', 'p', 'I')
        AND relfilenode <> 0;
+
+--
+-- When ALIGNOF_DOUBLE==4 (e.g. AIX), the C ABI may impose 8-byte alignment on
+-- some of the C types that correspond to TYPALIGN_DOUBLE SQL types.  To ensure
+-- catalog C struct layout matches catalog tuple layout, arrange for the tuple
+-- offset of each fixed-width, attalign='d' catalog column to be divisible by 8
+-- unconditionally.  Keep such columns before the first NameData column of the
+-- catalog, since packagers can override NAMEDATALEN to an odd number.
+--
+WITH check_columns AS (
+ SELECT relname, attname,
+  array(
+   SELECT t.oid
+    FROM pg_type t JOIN pg_attribute pa ON t.oid = pa.atttypid
+    WHERE pa.attrelid = a.attrelid AND
+          pa.attnum > 0 AND pa.attnum < a.attnum
+    ORDER BY pa.attnum) AS coltypes
+ FROM pg_attribute a JOIN pg_class c ON c.oid = attrelid
+  JOIN pg_namespace n ON c.relnamespace = n.oid
+ WHERE attalign = 'd' AND relkind = 'r' AND
+  attnotnull AND attlen <> -1 AND n.nspname = 'pg_catalog'
+)
+SELECT relname, attname, coltypes, get_columns_length(coltypes)
+ FROM check_columns
+ WHERE get_columns_length(coltypes) % 8 != 0 OR
+       'name'::regtype::oid = ANY(coltypes);
diff --git a/src/test/regress/sql/test_setup.sql b/src/test/regress/sql/test_setup.sql
index 06b0e2121f..1b2d434683 100644
--- a/src/test/regress/sql/test_setup.sql
+++ b/src/test/regress/sql/test_setup.sql
@@ -257,6 +257,11 @@ CREATE FUNCTION ttdummy ()
     AS :'regresslib'
     LANGUAGE C;
 
+CREATE FUNCTION get_columns_length(oid[])
+    RETURNS int
+    AS :'regresslib'
+    LANGUAGE C STRICT STABLE PARALLEL SAFE;
+
 -- Use hand-rolled hash functions and operator classes to get predictable
 -- result on different machines.  The hash function for int4 simply returns
 -- the sum of the values passed to it and the one for text returns the length
diff --git a/src/tools/gen_export.pl b/src/tools/gen_export.pl
index d9fdaaaf6d..888c8a197a 100644
--- a/src/tools/gen_export.pl
+++ b/src/tools/gen_export.pl
@@ -16,11 +16,12 @@ GetOptions(
 	'input:s' => \$input,
 	'output:s' => \$output) or die "wrong arguments";
 
-if (not(   $format eq 'darwin'
+if (not(   $format eq 'aix'
+		or $format eq 'darwin'
 		or $format eq 'gnu'
 		or $format eq 'win'))
 {
-	die "$0: $format is not yet handled (only darwin, gnu, win are)\n";
+	die "$0: $format is not yet handled (only aix, darwin, gnu, win are)\n";
 }
 
 open(my $input_handle, '<', $input)
@@ -55,7 +56,11 @@ while (<$input_handle>)
 	}
 	elsif (/^(\S+)\s+(\S+)/)
 	{
-		if ($format eq 'darwin')
+		if ($format eq 'aix')
+		{
+			print $output_handle "$1\n";
+		}
+		elsif ($format eq 'darwin')
 		{
 			print $output_handle "_$1\n";
 		}
diff --git a/src/tools/pginclude/headerscheck b/src/tools/pginclude/headerscheck
index 4a157d0a5f..cfd8c6896c 100755
--- a/src/tools/pginclude/headerscheck
+++ b/src/tools/pginclude/headerscheck
@@ -85,6 +85,7 @@ do
 
 	# These files are platform-specific, and c.h will include the
 	# one that's relevant for our current platform anyway.
+	test "$f" = src/include/port/aix.h && continue
 	test "$f" = src/include/port/cygwin.h && continue
 	test "$f" = src/include/port/darwin.h && continue
 	test "$f" = src/include/port/freebsd.h && continue
-- 
2.41.0

From a08fbe47316034c458fcfb748efd7caabad9893f Mon Sep 17 00:00:00 2001
From: Sriram RK <sriram.rk@in.ibm.com>
Date: Tue, 24 Sep 2024 05:04:51 -0500
Subject: [PATCH 1/1] Replace tas() asm with gcc routines for powerPC
 implementaion in s_lock.h .

---
 src/include/storage/s_lock.h | 43 ++++--------------------------------
 1 file changed, 4 insertions(+), 39 deletions(-)

diff --git a/src/include/storage/s_lock.h b/src/include/storage/s_lock.h
index 2f6eb5df2a..c0cc7bd38b 100644
--- a/src/include/storage/s_lock.h
+++ b/src/include/storage/s_lock.h
@@ -401,54 +401,19 @@ typedef unsigned int slock_t;
 
 #define TAS(lock) tas(lock)
 
-/* On PPC, it's a win to use a non-locking test before the lwarx */
+/* On PPC, use the gcc atomic routines, to set the lock. */
 #define TAS_SPIN(lock)	(*(lock) ? 1 : TAS(lock))
 
-/*
- * The second operand of addi can hold a constant zero or a register number,
- * hence constraint "=&b" to avoid allocating r0.  "b" stands for "address
- * base register"; most operands having this register-or-zero property are
- * address bases, e.g. the second operand of lwax.
- *
- * NOTE: per the Enhanced PowerPC Architecture manual, v1.0 dated 7-May-2002,
- * an isync is a sufficient synchronization barrier after a lwarx/stwcx loop.
- * But if the spinlock is in ordinary memory, we can use lwsync instead for
- * better performance.
- */
 static __inline__ int
 tas(volatile slock_t *lock)
 {
-	slock_t _t;
-	int _res;
-
-	__asm__ __volatile__(
-"	lwarx   %0,0,%3,1	\n"
-"	cmpwi   %0,0		\n"
-"	bne     $+16		\n"		/* branch to li %1,1 */
-"	addi    %0,%0,1		\n"
-"	stwcx.  %0,0,%3		\n"
-"	beq     $+12		\n"		/* branch to lwsync */
-"	li      %1,1		\n"
-"	b       $+12		\n"		/* branch to end of asm sequence */
-"	lwsync				\n"
-"	li      %1,0		\n"
-
-:	"=&b"(_t), "=r"(_res), "+m"(*lock)
-:	"r"(lock)
-:	"memory", "cc");
-	return _res;
+    return __sync_lock_test_and_set(lock, 1);
 }
 
 /*
- * PowerPC S_UNLOCK is almost standard but requires a "sync" instruction.
- * But we can use lwsync instead for better performance.
+ * PowerPC S_UNLOCK use the gcc atomic routines. 
  */
-#define S_UNLOCK(lock)	\
-do \
-{ \
-	__asm__ __volatile__ ("	lwsync \n" ::: "memory"); \
-	*((volatile slock_t *) (lock)) = 0; \
-} while (0)
+#define S_UNLOCK(lock) __sync_lock_release(lock)
 
 #endif /* powerpc */
 
-- 
2.41.0

From 103760b2d065081447efd27f4ecc20c5dbb7abcf Mon Sep 17 00:00:00 2001
From: Sriram RK <sriram.rk@in.ibm.com>
Date: Fri, 6 Dec 2024 10:36:29 -0600
Subject: [PATCH] AIX support

---
 Makefile                                     |  2 -
 configure                                    | 35 +++++++++--
 doc/src/sgml/dfunc.sgml                      | 19 ++++++
 src/Makefile.shlib                           | 29 ++++++++++
 src/backend/Makefile                         | 20 +++++++
 src/backend/port/aix/mkldexport.sh           | 61 ++++++++++++++++++++
 src/backend/utils/error/elog.c               |  2 +
 src/include/port/aix.h                       |  4 ++
 src/include/storage/s_lock.h                 | 10 ++--
 src/makefiles/Makefile.aix                   | 39 +++++++++++++
 src/port/strerror.c                          |  2 +
 src/template/aix                             |  7 +++
 src/test/regress/expected/jsonb_jsonpath.out |  6 +-           << IGNORE: known issue resolved in af21152268317323480
 src/test/regress/sql/jsonb_jsonpath.sql      |  4 ++           << IGNORE: known issue resolved in af21152268317323480
 14 files changed, 225 insertions(+), 15 deletions(-)
 create mode 100755 src/backend/port/aix/mkldexport.sh
 create mode 100644 src/include/port/aix.h
 create mode 100644 src/makefiles/Makefile.aix
 create mode 100644 src/template/aix

diff --git a/Makefile b/Makefile
index 8a2ec9396b..9bc1a4ec17 100644
--- a/Makefile
+++ b/Makefile
@@ -13,8 +13,6 @@
 
 # AIX make defaults to building *every* target of the first rule.  Start with
 # a single-target, empty rule to make the other targets non-default.
-# (We don't support AIX anymore, but if someone tries to build on AIX anyway,
-# at least they'll get the instructions to run 'configure' first.)
 all:
 
 all check install installdirs installcheck installcheck-parallel uninstall clean distclean maintainer-clean dist distcheck world check-world install-world installcheck-world:
diff --git a/configure b/configure
index 3a577e463b..0f400c4e84 100755
--- a/configure
+++ b/configure
@@ -2985,6 +2985,7 @@ else
 # --with-template not given
 
 case $host_os in
+  aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -16769,13 +16770,35 @@ _ACEOF
 # wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
 # much of a penalty for disk and memory space.
 
-MAX_ALIGNOF=$ac_cv_alignof_double
+if test "$PORTNAME" != "aix"; then
+    MAX_ALIGNOF=$ac_cv_alignof_double
+
+    if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
+      as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+    if test x"$HAVE_LONG_LONG_INT_64" = xyes && test $ac_cv_alignof_long_long_int -gt $MAX_ALIGNOF ; then
+      as_fn_error $? "alignment of 'long long int' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+else
+# AIX alignment info: We assume long's alignment is at least as strong as char, short, or
+# int; but we must check long long (if it is being used for int64) and double.
+#
+# The AIX 'power' alignment rules apply the natural alignment of the "first
+# member" if it is of a floating-point data type (or is an aggregate whose
+# recursively "first" member or element is such a type). The alignment
+# associated with these types for subsequent members use an alignment value
+# where the floating-point data type is considered to have 4-byte alignment.
+# 
+# The double is aligned to 4-bytes on AIX in aggregates. But to maintain
+# alignement across platforms the max alignment of long should be considered.
+    MAX_ALIGNOF=$ac_cv_alignof_long
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_double ; then
+      MAX_ALIGNOF=$ac_cv_alignof_double
+    fi
+    if test x"$HAVE_LONG_LONG_INT_64" = xyes && test $MAX_ALIGNOF -lt $ac_cv_alignof_long_long_int ; then
+      MAX_ALIGNOF="$ac_cv_alignof_long_long_int"
+    fi
 
-if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
-fi
-if test x"$HAVE_LONG_LONG_INT_64" = xyes && test $ac_cv_alignof_long_long_int -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'long long int' is greater than the alignment of 'double'" "$LINENO" 5
 fi
 
 cat >>confdefs.h <<_ACEOF
diff --git a/doc/src/sgml/dfunc.sgml b/doc/src/sgml/dfunc.sgml
index b94aefcd0c..554f9fac4c 100644
--- a/doc/src/sgml/dfunc.sgml
+++ b/doc/src/sgml/dfunc.sgml
@@ -202,4 +202,23 @@ gcc -G -o foo.so foo.o
   server expects to find the shared library files.
  </para>
 
+<!--
+Under AIX, object files are compiled normally but building the shared
+library requires a couple of steps.  First, create the object file:
+.nf
+cc <other flags> -c foo.c
+.fi
+You must then create a symbol \*(lqexports\*(rq file for the object
+file:
+.nf
+mkldexport foo.o `pwd` &gt; foo.exp
+.fi
+Finally, you can create the shared library:
+.nf
+ld <other flags> -H512 -T512 -o foo.so -e _nostart \e
+   -bI:.../lib/postgres.exp -bE:foo.exp foo.o \e
+   -lm -lc 2>/dev/null
+.fi
+  -->
+
 </sect2>
diff --git a/src/Makefile.shlib b/src/Makefile.shlib
index fa81f6ffdd..13ea84ac18 100644
--- a/src/Makefile.shlib
+++ b/src/Makefile.shlib
@@ -106,6 +106,20 @@ ifdef SO_MAJOR_VERSION
 override CPPFLAGS += -DSO_MAJOR_VERSION=$(SO_MAJOR_VERSION)
 endif
 
+ifeq ($(PORTNAME), aix)
+  LINK.shared		= $(COMPILER)
+  ifdef SO_MAJOR_VERSION
+    shlib		= lib$(NAME)$(DLSUFFIX).$(SO_MAJOR_VERSION)
+  endif
+  haslibarule   = yes
+  # $(exports_file) is also usable as an import file
+  exports_file		= lib$(NAME).exp
+  BUILD.exports		= ( echo '\#! $(shlib)'; $(AWK) '/^[^\#]/ {printf "%s\n",$$1}' $< ) > $@
+  ifneq (,$(SHLIB_EXPORTS))
+    LINK.shared		+= -Wl,-bE:$(exports_file)
+  endif
+endif
+
 ifeq ($(PORTNAME), darwin)
   ifdef soname
     # linkable library
@@ -254,6 +268,14 @@ $(stlib): $(OBJS) | $(SHLIB_PREREQS)
 	touch $@
 endif #haslibarule
 
+# AIX wraps both shared libraries and static library, which can be used both
+# for static and shared linking
+ifeq ($(PORTNAME), aix)
+$(stlib): $(shlib)
+	rm -f $(stlib)
+	$(AR) $(AROPT) $(stlib) $(shlib)
+endif # aix
+
 ifeq (,$(filter cygwin win32,$(PORTNAME)))
 
 # Normal case
@@ -267,8 +289,11 @@ ifneq ($(shlib), $(shlib_major))
 endif
 # Make sure we have a link to a name without any version numbers
 ifneq ($(shlib), $(shlib_bare))
+# except on AIX, where that's not a thing
+ifneq ($(PORTNAME), aix)
 	rm -f $(shlib_bare)
 	$(LN_S) $(shlib) $(shlib_bare)
+endif # aix
 endif # shlib_bare
 endif # shlib_major
 
@@ -376,6 +401,9 @@ install-lib-static: $(stlib) installdirs-lib
 
 install-lib-shared: $(shlib) installdirs-lib
 ifdef soname
+# we don't install $(shlib) on AIX
+# (see http://archives.postgresql.org/message-id/52EF20B2E3209443BC37736D00C3C1380A6E79FE@EXADV1.host.magwien.gv.at)
+ifneq ($(PORTNAME), aix)
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(libdir)/$(shlib)'
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
@@ -391,6 +419,7 @@ ifneq ($(shlib), $(shlib_bare))
 endif
 endif # not win32
 endif # not cygwin
+endif # not aix
 ifneq (,$(findstring $(PORTNAME),win32 cygwin))
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(bindir)/$(shlib)'
 endif
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 84302cc6da..a37f6198ed 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -62,12 +62,14 @@ all: submake-libpgport submake-catalog-headers submake-utils-headers postgres $(
 
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
+ifneq ($(PORTNAME), aix)
 
 postgres: $(OBJS)
 	$(CC) $(CFLAGS) $(call expand_subsys,$^) $(LDFLAGS) $(LIBS) -o $@
 
 endif
 endif
+endif
 
 ifeq ($(PORTNAME), cygwin)
 
@@ -94,6 +96,24 @@ libpostgres.a: postgres
 
 endif # win32
 
+ifeq ($(PORTNAME), aix)
+
+postgres: $(POSTGRES_IMP)
+	$(CC) $(CFLAGS) $(call expand_subsys,$(OBJS)) $(LDFLAGS) -Wl,-bE:$(top_builddir)/src/backend/$(POSTGRES_IMP) $(LIBS) -Wl,-brtllib -o $@
+
+# Linking to a single .o with -r is a lot faster than building a .a or passing
+# all objects to MKLDEXPORT.
+#
+# It looks alluring to use $(CC) -r instead of ld -r, but that doesn't
+# trivially work with gcc, due to gcc specific static libraries linked in with
+# -r.
+$(POSTGRES_IMP): $(OBJS)
+	ld -r -o SUBSYS.o $(call expand_subsys,$^)
+	$(MKLDEXPORT) SUBSYS.o . > $@
+	@rm -f SUBSYS.o
+
+endif # aix
+
 $(top_builddir)/src/port/libpgport_srv.a: | submake-libpgport
 
 
diff --git a/src/backend/port/aix/mkldexport.sh b/src/backend/port/aix/mkldexport.sh
new file mode 100755
index 0000000000..adf3793e86
--- /dev/null
+++ b/src/backend/port/aix/mkldexport.sh
@@ -0,0 +1,61 @@
+#!/bin/sh
+#
+# mkldexport
+#	create an AIX exports file from an object file
+#
+# src/backend/port/aix/mkldexport.sh
+#
+# Usage:
+#	mkldexport objectfile [location]
+# where
+#	objectfile is the current location of the object file.
+#	location is the eventual (installed) location of the
+#		object file (if different from the current
+#		working directory).
+#
+# [This file comes from the Postgres 4.2 distribution. - ay 7/95]
+#
+# Header: /usr/local/devel/postgres/src/tools/mkldexport/RCS/mkldexport.sh,v 1.2 1994/03/13 04:59:12 aoki Exp
+#
+
+# setting this to nm -B might be better
+# ... due to changes in AIX 4.x ...
+# ... let us search in different directories - Gerhard Reithofer
+if [ -x /usr/ucb/nm ]
+then NM=/usr/ucb/nm
+elif [ -x /usr/bin/nm ]
+then NM=/usr/bin/nm
+elif [ -x /usr/ccs/bin/nm ]
+then NM=/usr/ccs/bin/nm
+elif [ -x /usr/usg/bin/nm ]
+then NM=/usr/usg/bin/nm
+else echo "Fatal error: cannot find `nm' ... please check your installation."
+     exit 1
+fi
+
+CMDNAME=`basename $0`
+if [ -z "$1" ]; then
+	echo "Usage: $CMDNAME object [location]"
+	exit 1
+fi
+OBJNAME=`basename $1`
+if [ "`basename $OBJNAME`" != "`basename $OBJNAME .o`" ]; then
+	OBJNAME=`basename $OBJNAME .o`.so
+fi
+if [ -z "$2" ]; then
+	echo '#!'
+else
+	if [ "$2" = "." ]; then
+		# for the base executable (AIX 4.2 and up)
+		echo '#! .'
+	else
+		echo '#!' $2
+	fi
+fi
+$NM -BCg $1 | \
+	egrep ' [TDB] ' | \
+	sed -e 's/.* //' | \
+	egrep -v '\$' | \
+	sed -e 's/^[.]//' | \
+	sort | \
+	uniq
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 8acca3e0a0..54c3446c66 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -904,7 +904,9 @@ errcode_for_file_access(void)
 			/* Wrong object type or state */
 		case ENOTDIR:			/* Not a directory */
 		case EISDIR:			/* Is a directory */
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:			/* Directory not empty */
+#endif
 			edata->sqlerrcode = ERRCODE_WRONG_OBJECT_TYPE;
 			break;
 
diff --git a/src/include/port/aix.h b/src/include/port/aix.h
new file mode 100644
index 0000000000..7d08480c8c
--- /dev/null
+++ b/src/include/port/aix.h
@@ -0,0 +1,4 @@
+/*
+ * src/include/port/aix.h
+ */
+
diff --git a/src/include/storage/s_lock.h b/src/include/storage/s_lock.h
index e94ed5f48b..17a2ee0973 100644
--- a/src/include/storage/s_lock.h
+++ b/src/include/storage/s_lock.h
@@ -415,17 +415,15 @@ tas(volatile slock_t *lock)
 	__asm__ __volatile__(
 "	lwarx   %0,0,%3,1	\n"
 "	cmpwi   %0,0		\n"
-"	bne     1f			\n"
+"	bne     $+16		\n"		/* branch to li %1,1 */
 "	addi    %0,%0,1		\n"
 "	stwcx.  %0,0,%3		\n"
-"	beq     2f			\n"
-"1: \n"
+"	beq     $+12		\n"		/* branch to lwsync */
 "	li      %1,1		\n"
-"	b       3f			\n"
-"2: \n"
+"	b       $+12		\n"		/* branch to end of asm sequence */
 "	lwsync				\n"
 "	li      %1,0		\n"
-"3: \n"
+
 :	"=&b"(_t), "=r"(_res), "+m"(*lock)
 :	"r"(lock)
 :	"memory", "cc");
diff --git a/src/makefiles/Makefile.aix b/src/makefiles/Makefile.aix
new file mode 100644
index 0000000000..dd16a7a037
--- /dev/null
+++ b/src/makefiles/Makefile.aix
@@ -0,0 +1,39 @@
+# MAKE_EXPORTS is required for svr4 loaders that want a file of
+# symbol names to tell them what to export/import.
+MAKE_EXPORTS= true
+
+# -blibpath must contain ALL directories where we should look for libraries
+libpath := $(shell echo $(subst -L,:,$(filter -L/%,$(LDFLAGS))) | sed -e's/ //g'):/usr/lib:/lib
+
+# when building with gcc, need to make sure that libgcc can be found
+ifeq ($(GCC), yes)
+libpath := $(libpath):$(dir $(shell gcc -print-libgcc-file-name))
+endif
+
+rpath = -Wl,-blibpath:'$(rpathdir)$(libpath)'
+
+LDFLAGS_SL += -Wl,-bnoentry -Wl,-H512 -Wl,-bM:SRE
+
+# gcc needs to know it's building a shared lib, otherwise it'll not emit
+# correct code / link to the right support libraries
+ifeq ($(GCC), yes)
+LDFLAGS_SL += -shared
+endif
+
+# env var name to use in place of LD_LIBRARY_PATH
+ld_library_path_var = LIBPATH
+
+
+POSTGRES_IMP= postgres.imp
+
+ifdef PGXS
+BE_DLLLIBS= -Wl,-bI:$(pkglibdir)/$(POSTGRES_IMP)
+else
+BE_DLLLIBS= -Wl,-bI:$(top_builddir)/src/backend/$(POSTGRES_IMP)
+endif
+
+MKLDEXPORT_DIR=src/backend/port/aix
+MKLDEXPORT=$(top_srcdir)/$(MKLDEXPORT_DIR)/mkldexport.sh
+
+%$(DLSUFFIX): %.o
+	$(CC) $(CFLAGS) $*.o $(LDFLAGS) $(LDFLAGS_SL) -o $@ $(BE_DLLLIBS)
diff --git a/src/port/strerror.c b/src/port/strerror.c
index 4918ba821c..1070a49802 100644
--- a/src/port/strerror.c
+++ b/src/port/strerror.c
@@ -214,8 +214,10 @@ get_errno_symbol(int errnum)
 			return "ENOTCONN";
 		case ENOTDIR:
 			return "ENOTDIR";
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:
 			return "ENOTEMPTY";
+#endif
 		case ENOTSOCK:
 			return "ENOTSOCK";
 #ifdef ENOTSUP
diff --git a/src/template/aix b/src/template/aix
new file mode 100644
index 0000000000..48a3ce55cf
--- /dev/null
+++ b/src/template/aix
@@ -0,0 +1,7 @@
+# src/template/aix
+
+# Extra CFLAGS for code that will go into a shared library
+CFLAGS_SL=""
+
+# Native memset() is faster.
+MEMSET_LOOP_LIMIT=0
diff --git a/src/test/regress/expected/jsonb_jsonpath.out b/src/test/regress/expected/jsonb_jsonpath.out
index acdf7e436f..4bcd4e91a2 100644
--- a/src/test/regress/expected/jsonb_jsonpath.out
+++ b/src/test/regress/expected/jsonb_jsonpath.out
@@ -2684,12 +2684,16 @@ select jsonb_path_query('"12:34:56 +5:30"', '$.time_tz().string()');
  "12:34:56+05:30"
 (1 row)
 
+-- this timetz usage will absorb the UTC offset of the current timezone setting
+begin;
+set local timezone = 'UTC-10';
 select jsonb_path_query_tz('"12:34:56"', '$.time_tz().string()');
  jsonb_path_query_tz 
 ---------------------
- "12:34:56-07:00"
+ "12:34:56+10:00"
 (1 row)
 
+rollback;
 select jsonb_path_query('"12:34:56"', '$.time().string()');
  jsonb_path_query 
 ------------------
diff --git a/src/test/regress/sql/jsonb_jsonpath.sql b/src/test/regress/sql/jsonb_jsonpath.sql
index da3f7969ca..3e8929a526 100644
--- a/src/test/regress/sql/jsonb_jsonpath.sql
+++ b/src/test/regress/sql/jsonb_jsonpath.sql
@@ -607,7 +607,11 @@ select jsonb_path_query_tz('"2023-08-15 12:34:56"', '$.timestamp_tz().string()')
 select jsonb_path_query('"2023-08-15 12:34:56 +5:30"', '$.timestamp_tz().string()');
 select jsonb_path_query('"2023-08-15 12:34:56"', '$.timestamp().string()');
 select jsonb_path_query('"12:34:56 +5:30"', '$.time_tz().string()');
+-- this timetz usage will absorb the UTC offset of the current timezone setting
+begin;
+set local timezone = 'UTC-10';
 select jsonb_path_query_tz('"12:34:56"', '$.time_tz().string()');
+rollback;
 select jsonb_path_query('"12:34:56"', '$.time().string()');
 select jsonb_path_query('"2023-08-15"', '$.date().string()');
 
-- 
2.41.0

From 614cd077da0de9ca92c4e4fb300c39f73ab5ad10 Mon Sep 17 00:00:00 2001
From: Sriram RK <sriram.rk@in.ibm.com>
Date: Fri, 4 Apr 2025 13:16:21 -0500
Subject: [PATCH] AIX support.

---
 Makefile                           |  2 -
 configure                          | 34 ++++++++++++++---
 configure.ac                       | 34 ++++++++++++++---
 src/Makefile.shlib                 | 29 ++++++++++++++
 src/backend/Makefile               | 20 ++++++++++
 src/backend/port/aix/mkldexport.sh | 61 ++++++++++++++++++++++++++++++
 src/backend/utils/error/elog.c     |  2 +
 src/include/port/aix.h             |  4 ++
 src/include/storage/s_lock.h       | 10 ++---
 src/makefiles/Makefile.aix         | 39 +++++++++++++++++++
 src/port/strerror.c                |  2 +
 src/template/aix                   |  7 ++++
 12 files changed, 224 insertions(+), 20 deletions(-)
 create mode 100755 src/backend/port/aix/mkldexport.sh
 create mode 100644 src/include/port/aix.h
 create mode 100644 src/makefiles/Makefile.aix
 create mode 100644 src/template/aix

diff --git a/Makefile b/Makefile
index 8a2ec9396b6..9bc1a4ec17b 100644
--- a/Makefile
+++ b/Makefile
@@ -13,8 +13,6 @@
 
 # AIX make defaults to building *every* target of the first rule.  Start with
 # a single-target, empty rule to make the other targets non-default.
-# (We don't support AIX anymore, but if someone tries to build on AIX anyway,
-# at least they'll get the instructions to run 'configure' first.)
 all:
 
 all check install installdirs installcheck installcheck-parallel uninstall clean distclean maintainer-clean dist distcheck world check-world install-world installcheck-world:
diff --git a/configure b/configure
index 11615d1122d..6088fa26679 100755
--- a/configure
+++ b/configure
@@ -3008,6 +3008,7 @@ else
 # --with-template not given
 
 case $host_os in
+  aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -16953,13 +16954,34 @@ _ACEOF
 # wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
 # much of a penalty for disk and memory space.
 
-MAX_ALIGNOF=$ac_cv_alignof_double
+if test "$PORTNAME" != "aix"; then
+    MAX_ALIGNOF=$ac_cv_alignof_double
+
+    if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
+      as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+    if test $ac_cv_alignof_int64_t -gt $MAX_ALIGNOF ; then
+      as_fn_error $? "alignment of 'long long int' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+else
+# The AIX 'power' alignment rules apply the natural alignment of the "first
+# member" if it is of a floating-point data type (or is an aggregate whose
+# recursively "first" member or element is such a type). The alignment
+# associated with these types for subsequent members use an alignment value
+# where the floating-point data type is considered to have 4-byte alignment.
+# More info
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99557
+#
+# The double is aligned to 4-bytes on AIX in aggregates. But to maintain
+# alignement across platforms the max alignment of long should be considered.
+    MAX_ALIGNOF=$ac_cv_alignof_long
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_double ; then
+      MAX_ALIGNOF=$ac_cv_alignof_double
+    fi
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_int64_t; then
+      MAX_ALIGNOF="$ac_cv_alignof_int64_t"
+    fi
 
-if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
-fi
-if test $ac_cv_alignof_int64_t -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'int64_t' is greater than the alignment of 'double'" "$LINENO" 5
 fi
 
 cat >>confdefs.h <<_ACEOF
diff --git a/configure.ac b/configure.ac
index debdf165044..c21aaa52064 100644
--- a/configure.ac
+++ b/configure.ac
@@ -62,6 +62,7 @@ PGAC_ARG_REQ(with, template, [NAME], [override operating system template],
 # --with-template not given
 
 case $host_os in
+  aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -1987,13 +1988,34 @@ AC_CHECK_ALIGNOF(double)
 # wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
 # much of a penalty for disk and memory space.
 
-MAX_ALIGNOF=$ac_cv_alignof_double
+if test "$PORTNAME" != "aix"; then
+    MAX_ALIGNOF=$ac_cv_alignof_double
+
+    if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
+      as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+    if test $ac_cv_alignof_int64_t -gt $MAX_ALIGNOF; then
+      as_fn_error $? "alignment of 'long long int' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+else
+# The AIX 'power' alignment rules apply the natural alignment of the "first
+# member" if it is of a floating-point data type (or is an aggregate whose
+# recursively "first" member or element is such a type). The alignment
+# associated with these types for subsequent members use an alignment value
+# where the floating-point data type is considered to have 4-byte alignment.
+# More info
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99557
+# 
+# The double is aligned to 4-bytes on AIX in aggregates. But to maintain
+# alignement across platforms the max alignment of long should be considered.
+    MAX_ALIGNOF=$ac_cv_alignof_long
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_double ; then
+      MAX_ALIGNOF=$ac_cv_alignof_double
+    fi
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_int64_t ; then
+      MAX_ALIGNOF="$ac_cv_alignof_int64_t"
+    fi
 
-if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
-  AC_MSG_ERROR([alignment of 'long' is greater than the alignment of 'double'])
-fi
-if test $ac_cv_alignof_int64_t -gt $MAX_ALIGNOF ; then
-  AC_MSG_ERROR([alignment of 'int64_t' is greater than the alignment of 'double'])
 fi
 AC_DEFINE_UNQUOTED(MAXIMUM_ALIGNOF, $MAX_ALIGNOF, [Define as the maximum alignment requirement of any C data type.])
 
diff --git a/src/Makefile.shlib b/src/Makefile.shlib
index fa81f6ffdd6..13ea84ac185 100644
--- a/src/Makefile.shlib
+++ b/src/Makefile.shlib
@@ -106,6 +106,20 @@ ifdef SO_MAJOR_VERSION
 override CPPFLAGS += -DSO_MAJOR_VERSION=$(SO_MAJOR_VERSION)
 endif
 
+ifeq ($(PORTNAME), aix)
+  LINK.shared		= $(COMPILER)
+  ifdef SO_MAJOR_VERSION
+    shlib		= lib$(NAME)$(DLSUFFIX).$(SO_MAJOR_VERSION)
+  endif
+  haslibarule   = yes
+  # $(exports_file) is also usable as an import file
+  exports_file		= lib$(NAME).exp
+  BUILD.exports		= ( echo '\#! $(shlib)'; $(AWK) '/^[^\#]/ {printf "%s\n",$$1}' $< ) > $@
+  ifneq (,$(SHLIB_EXPORTS))
+    LINK.shared		+= -Wl,-bE:$(exports_file)
+  endif
+endif
+
 ifeq ($(PORTNAME), darwin)
   ifdef soname
     # linkable library
@@ -254,6 +268,14 @@ $(stlib): $(OBJS) | $(SHLIB_PREREQS)
 	touch $@
 endif #haslibarule
 
+# AIX wraps both shared libraries and static library, which can be used both
+# for static and shared linking
+ifeq ($(PORTNAME), aix)
+$(stlib): $(shlib)
+	rm -f $(stlib)
+	$(AR) $(AROPT) $(stlib) $(shlib)
+endif # aix
+
 ifeq (,$(filter cygwin win32,$(PORTNAME)))
 
 # Normal case
@@ -267,8 +289,11 @@ ifneq ($(shlib), $(shlib_major))
 endif
 # Make sure we have a link to a name without any version numbers
 ifneq ($(shlib), $(shlib_bare))
+# except on AIX, where that's not a thing
+ifneq ($(PORTNAME), aix)
 	rm -f $(shlib_bare)
 	$(LN_S) $(shlib) $(shlib_bare)
+endif # aix
 endif # shlib_bare
 endif # shlib_major
 
@@ -376,6 +401,9 @@ install-lib-static: $(stlib) installdirs-lib
 
 install-lib-shared: $(shlib) installdirs-lib
 ifdef soname
+# we don't install $(shlib) on AIX
+# (see http://archives.postgresql.org/message-id/52EF20B2E3209443BC37736D00C3C1380A6E79FE@EXADV1.host.magwien.gv.at)
+ifneq ($(PORTNAME), aix)
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(libdir)/$(shlib)'
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
@@ -391,6 +419,7 @@ ifneq ($(shlib), $(shlib_bare))
 endif
 endif # not win32
 endif # not cygwin
+endif # not aix
 ifneq (,$(findstring $(PORTNAME),win32 cygwin))
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(bindir)/$(shlib)'
 endif
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 7344c8c7f5c..572f5430a60 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -63,12 +63,14 @@ all: submake-libpgport submake-catalog-headers submake-utils-headers postgres $(
 
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
+ifneq ($(PORTNAME), aix)
 
 postgres: $(OBJS)
 	$(CC) $(CFLAGS) $(call expand_subsys,$^) $(LDFLAGS) $(LIBS) -o $@
 
 endif
 endif
+endif
 
 ifeq ($(PORTNAME), cygwin)
 
@@ -95,6 +97,24 @@ libpostgres.a: postgres
 
 endif # win32
 
+ifeq ($(PORTNAME), aix)
+
+postgres: $(POSTGRES_IMP)
+	$(CC) $(CFLAGS) $(call expand_subsys,$(OBJS)) $(LDFLAGS) -Wl,-bE:$(top_builddir)/src/backend/$(POSTGRES_IMP) $(LIBS) -Wl,-brtllib -o $@
+
+# Linking to a single .o with -r is a lot faster than building a .a or passing
+# all objects to MKLDEXPORT.
+#
+# It looks alluring to use $(CC) -r instead of ld -r, but that doesn't
+# trivially work with gcc, due to gcc specific static libraries linked in with
+# -r.
+$(POSTGRES_IMP): $(OBJS)
+	ld -r -o SUBSYS.o $(call expand_subsys,$^)
+	$(MKLDEXPORT) SUBSYS.o . > $@
+	@rm -f SUBSYS.o
+
+endif # aix
+
 $(top_builddir)/src/port/libpgport_srv.a: | submake-libpgport
 
 
diff --git a/src/backend/port/aix/mkldexport.sh b/src/backend/port/aix/mkldexport.sh
new file mode 100755
index 00000000000..adf3793e868
--- /dev/null
+++ b/src/backend/port/aix/mkldexport.sh
@@ -0,0 +1,61 @@
+#!/bin/sh
+#
+# mkldexport
+#	create an AIX exports file from an object file
+#
+# src/backend/port/aix/mkldexport.sh
+#
+# Usage:
+#	mkldexport objectfile [location]
+# where
+#	objectfile is the current location of the object file.
+#	location is the eventual (installed) location of the
+#		object file (if different from the current
+#		working directory).
+#
+# [This file comes from the Postgres 4.2 distribution. - ay 7/95]
+#
+# Header: /usr/local/devel/postgres/src/tools/mkldexport/RCS/mkldexport.sh,v 1.2 1994/03/13 04:59:12 aoki Exp
+#
+
+# setting this to nm -B might be better
+# ... due to changes in AIX 4.x ...
+# ... let us search in different directories - Gerhard Reithofer
+if [ -x /usr/ucb/nm ]
+then NM=/usr/ucb/nm
+elif [ -x /usr/bin/nm ]
+then NM=/usr/bin/nm
+elif [ -x /usr/ccs/bin/nm ]
+then NM=/usr/ccs/bin/nm
+elif [ -x /usr/usg/bin/nm ]
+then NM=/usr/usg/bin/nm
+else echo "Fatal error: cannot find `nm' ... please check your installation."
+     exit 1
+fi
+
+CMDNAME=`basename $0`
+if [ -z "$1" ]; then
+	echo "Usage: $CMDNAME object [location]"
+	exit 1
+fi
+OBJNAME=`basename $1`
+if [ "`basename $OBJNAME`" != "`basename $OBJNAME .o`" ]; then
+	OBJNAME=`basename $OBJNAME .o`.so
+fi
+if [ -z "$2" ]; then
+	echo '#!'
+else
+	if [ "$2" = "." ]; then
+		# for the base executable (AIX 4.2 and up)
+		echo '#! .'
+	else
+		echo '#!' $2
+	fi
+fi
+$NM -BCg $1 | \
+	egrep ' [TDB] ' | \
+	sed -e 's/.* //' | \
+	egrep -v '\$' | \
+	sed -e 's/^[.]//' | \
+	sort | \
+	uniq
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 8a6b6905079..3a8e9dc30b0 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -904,7 +904,9 @@ errcode_for_file_access(void)
 			/* Wrong object type or state */
 		case ENOTDIR:			/* Not a directory */
 		case EISDIR:			/* Is a directory */
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:			/* Directory not empty */
+#endif
 			edata->sqlerrcode = ERRCODE_WRONG_OBJECT_TYPE;
 			break;
 
diff --git a/src/include/port/aix.h b/src/include/port/aix.h
new file mode 100644
index 00000000000..7d08480c8c0
--- /dev/null
+++ b/src/include/port/aix.h
@@ -0,0 +1,4 @@
+/*
+ * src/include/port/aix.h
+ */
+
diff --git a/src/include/storage/s_lock.h b/src/include/storage/s_lock.h
index 2f73f9fcf57..5da9b3acda4 100644
--- a/src/include/storage/s_lock.h
+++ b/src/include/storage/s_lock.h
@@ -421,17 +421,15 @@ tas(volatile slock_t *lock)
 	__asm__ __volatile__(
 "	lwarx   %0,0,%3,1	\n"
 "	cmpwi   %0,0		\n"
-"	bne     1f			\n"
+"	bne     $+16		\n"		/* branch to li %1,1 */
 "	addi    %0,%0,1		\n"
 "	stwcx.  %0,0,%3		\n"
-"	beq     2f			\n"
-"1: \n"
+"	beq     $+12		\n"		/* branch to lwsync */
 "	li      %1,1		\n"
-"	b       3f			\n"
-"2: \n"
+"	b       $+12		\n"		/* branch to end of asm sequence */
 "	lwsync				\n"
 "	li      %1,0		\n"
-"3: \n"
+
 :	"=&b"(_t), "=r"(_res), "+m"(*lock)
 :	"r"(lock)
 :	"memory", "cc");
diff --git a/src/makefiles/Makefile.aix b/src/makefiles/Makefile.aix
new file mode 100644
index 00000000000..d33918f91b9
--- /dev/null
+++ b/src/makefiles/Makefile.aix
@@ -0,0 +1,39 @@
+# MAKE_EXPORTS is required for svr4 loaders that want a file of
+# symbol names to tell them what to export/import.
+MAKE_EXPORTS= true
+
+# -blibpath must contain ALL directories where we should look for libraries
+libpath := $(shell echo $(subst -L,:,$(filter -L/%,$(LDFLAGS))) | sed -e's/ //g'):/usr/lib:/lib
+
+# when building with gcc, need to make sure that libgcc can be found
+ifeq ($(GCC), yes)
+libpath := $(libpath):$(dir $(shell gcc -print-libgcc-file-name))
+endif
+
+rpath = -Wl,-blibpath:'$(rpathdir)$(libpath)'
+
+#LDFLAGS_SL += -Wl,-bnoentry -Wl,-H512 -Wl,-bM:SRE
+
+# gcc needs to know it's building a shared lib, otherwise it'll not emit
+# correct code / link to the right support libraries
+ifeq ($(GCC), yes)
+LDFLAGS_SL += -shared
+endif
+
+# env var name to use in place of LD_LIBRARY_PATH
+ld_library_path_var = LIBPATH
+
+
+POSTGRES_IMP= postgres.imp
+
+ifdef PGXS
+BE_DLLLIBS= -Wl,-bI:$(pkglibdir)/$(POSTGRES_IMP)
+else
+BE_DLLLIBS= -Wl,-bI:$(top_builddir)/src/backend/$(POSTGRES_IMP)
+endif
+
+MKLDEXPORT_DIR=src/backend/port/aix
+MKLDEXPORT=$(top_srcdir)/$(MKLDEXPORT_DIR)/mkldexport.sh
+
+%$(DLSUFFIX): %.o
+	$(CC) $(CFLAGS) $*.o $(LDFLAGS) $(LDFLAGS_SL) -o $@ $(BE_DLLLIBS)
diff --git a/src/port/strerror.c b/src/port/strerror.c
index f0746517770..c46b9dc91fc 100644
--- a/src/port/strerror.c
+++ b/src/port/strerror.c
@@ -214,8 +214,10 @@ get_errno_symbol(int errnum)
 			return "ENOTCONN";
 		case ENOTDIR:
 			return "ENOTDIR";
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:
 			return "ENOTEMPTY";
+#endif
 		case ENOTSOCK:
 			return "ENOTSOCK";
 #ifdef ENOTSUP
diff --git a/src/template/aix b/src/template/aix
new file mode 100644
index 00000000000..48a3ce55cf7
--- /dev/null
+++ b/src/template/aix
@@ -0,0 +1,7 @@
+# src/template/aix
+
+# Extra CFLAGS for code that will go into a shared library
+CFLAGS_SL=""
+
+# Native memset() is faster.
+MEMSET_LOOP_LIMIT=0
-- 
2.41.0

From c854025252ca3dfff9f7f1c4d4aed21cf0cf5346 Mon Sep 17 00:00:00 2001
From: Sriram RK <sriram.rk@in.ibm.com>
Date: Fri, 4 Apr 2025 13:16:21 -0500
Subject: [PATCH] AIX support.

---
 Makefile                           |  2 -
 configure                          | 34 ++++++++++++++---
 configure.ac                       | 34 ++++++++++++++---
 src/Makefile.shlib                 | 29 ++++++++++++++
 src/backend/Makefile               | 20 ++++++++++
 src/backend/port/aix/mkldexport.sh | 61 ++++++++++++++++++++++++++++++
 src/backend/utils/error/elog.c     |  2 +
 src/include/port/aix.h             |  4 ++
 src/include/storage/s_lock.h       | 10 ++---
 src/makefiles/Makefile.aix         | 29 ++++++++++++++
 src/port/strerror.c                |  2 +
 src/template/aix                   |  7 ++++
 12 files changed, 214 insertions(+), 20 deletions(-)
 create mode 100755 src/backend/port/aix/mkldexport.sh
 create mode 100644 src/include/port/aix.h
 create mode 100644 src/makefiles/Makefile.aix
 create mode 100644 src/template/aix

diff --git a/Makefile b/Makefile
index 8a2ec9396b6..9bc1a4ec17b 100644
--- a/Makefile
+++ b/Makefile
@@ -13,8 +13,6 @@
 
 # AIX make defaults to building *every* target of the first rule.  Start with
 # a single-target, empty rule to make the other targets non-default.
-# (We don't support AIX anymore, but if someone tries to build on AIX anyway,
-# at least they'll get the instructions to run 'configure' first.)
 all:
 
 all check install installdirs installcheck installcheck-parallel uninstall clean distclean maintainer-clean dist distcheck world check-world install-world installcheck-world:
diff --git a/configure b/configure
index 11615d1122d..6088fa26679 100755
--- a/configure
+++ b/configure
@@ -3008,6 +3008,7 @@ else
 # --with-template not given
 
 case $host_os in
+  aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -16953,13 +16954,34 @@ _ACEOF
 # wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
 # much of a penalty for disk and memory space.
 
-MAX_ALIGNOF=$ac_cv_alignof_double
+if test "$PORTNAME" != "aix"; then
+    MAX_ALIGNOF=$ac_cv_alignof_double
+
+    if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
+      as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+    if test $ac_cv_alignof_int64_t -gt $MAX_ALIGNOF ; then
+      as_fn_error $? "alignment of 'long long int' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+else
+# The AIX 'power' alignment rules apply the natural alignment of the "first
+# member" if it is of a floating-point data type (or is an aggregate whose
+# recursively "first" member or element is such a type). The alignment
+# associated with these types for subsequent members use an alignment value
+# where the floating-point data type is considered to have 4-byte alignment.
+# More info
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99557
+#
+# The double is aligned to 4-bytes on AIX in aggregates. But to maintain
+# alignement across platforms the max alignment of long should be considered.
+    MAX_ALIGNOF=$ac_cv_alignof_long
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_double ; then
+      MAX_ALIGNOF=$ac_cv_alignof_double
+    fi
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_int64_t; then
+      MAX_ALIGNOF="$ac_cv_alignof_int64_t"
+    fi
 
-if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
-fi
-if test $ac_cv_alignof_int64_t -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'int64_t' is greater than the alignment of 'double'" "$LINENO" 5
 fi
 
 cat >>confdefs.h <<_ACEOF
diff --git a/configure.ac b/configure.ac
index debdf165044..c21aaa52064 100644
--- a/configure.ac
+++ b/configure.ac
@@ -62,6 +62,7 @@ PGAC_ARG_REQ(with, template, [NAME], [override operating system template],
 # --with-template not given
 
 case $host_os in
+  aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -1987,13 +1988,34 @@ AC_CHECK_ALIGNOF(double)
 # wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
 # much of a penalty for disk and memory space.
 
-MAX_ALIGNOF=$ac_cv_alignof_double
+if test "$PORTNAME" != "aix"; then
+    MAX_ALIGNOF=$ac_cv_alignof_double
+
+    if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
+      as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+    if test $ac_cv_alignof_int64_t -gt $MAX_ALIGNOF; then
+      as_fn_error $? "alignment of 'long long int' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+else
+# The AIX 'power' alignment rules apply the natural alignment of the "first
+# member" if it is of a floating-point data type (or is an aggregate whose
+# recursively "first" member or element is such a type). The alignment
+# associated with these types for subsequent members use an alignment value
+# where the floating-point data type is considered to have 4-byte alignment.
+# More info
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99557
+# 
+# The double is aligned to 4-bytes on AIX in aggregates. But to maintain
+# alignement across platforms the max alignment of long should be considered.
+    MAX_ALIGNOF=$ac_cv_alignof_long
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_double ; then
+      MAX_ALIGNOF=$ac_cv_alignof_double
+    fi
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_int64_t ; then
+      MAX_ALIGNOF="$ac_cv_alignof_int64_t"
+    fi
 
-if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
-  AC_MSG_ERROR([alignment of 'long' is greater than the alignment of 'double'])
-fi
-if test $ac_cv_alignof_int64_t -gt $MAX_ALIGNOF ; then
-  AC_MSG_ERROR([alignment of 'int64_t' is greater than the alignment of 'double'])
 fi
 AC_DEFINE_UNQUOTED(MAXIMUM_ALIGNOF, $MAX_ALIGNOF, [Define as the maximum alignment requirement of any C data type.])
 
diff --git a/src/Makefile.shlib b/src/Makefile.shlib
index fa81f6ffdd6..13ea84ac185 100644
--- a/src/Makefile.shlib
+++ b/src/Makefile.shlib
@@ -106,6 +106,20 @@ ifdef SO_MAJOR_VERSION
 override CPPFLAGS += -DSO_MAJOR_VERSION=$(SO_MAJOR_VERSION)
 endif
 
+ifeq ($(PORTNAME), aix)
+  LINK.shared		= $(COMPILER)
+  ifdef SO_MAJOR_VERSION
+    shlib		= lib$(NAME)$(DLSUFFIX).$(SO_MAJOR_VERSION)
+  endif
+  haslibarule   = yes
+  # $(exports_file) is also usable as an import file
+  exports_file		= lib$(NAME).exp
+  BUILD.exports		= ( echo '\#! $(shlib)'; $(AWK) '/^[^\#]/ {printf "%s\n",$$1}' $< ) > $@
+  ifneq (,$(SHLIB_EXPORTS))
+    LINK.shared		+= -Wl,-bE:$(exports_file)
+  endif
+endif
+
 ifeq ($(PORTNAME), darwin)
   ifdef soname
     # linkable library
@@ -254,6 +268,14 @@ $(stlib): $(OBJS) | $(SHLIB_PREREQS)
 	touch $@
 endif #haslibarule
 
+# AIX wraps both shared libraries and static library, which can be used both
+# for static and shared linking
+ifeq ($(PORTNAME), aix)
+$(stlib): $(shlib)
+	rm -f $(stlib)
+	$(AR) $(AROPT) $(stlib) $(shlib)
+endif # aix
+
 ifeq (,$(filter cygwin win32,$(PORTNAME)))
 
 # Normal case
@@ -267,8 +289,11 @@ ifneq ($(shlib), $(shlib_major))
 endif
 # Make sure we have a link to a name without any version numbers
 ifneq ($(shlib), $(shlib_bare))
+# except on AIX, where that's not a thing
+ifneq ($(PORTNAME), aix)
 	rm -f $(shlib_bare)
 	$(LN_S) $(shlib) $(shlib_bare)
+endif # aix
 endif # shlib_bare
 endif # shlib_major
 
@@ -376,6 +401,9 @@ install-lib-static: $(stlib) installdirs-lib
 
 install-lib-shared: $(shlib) installdirs-lib
 ifdef soname
+# we don't install $(shlib) on AIX
+# (see http://archives.postgresql.org/message-id/52EF20B2E3209443BC37736D00C3C1380A6E79FE@EXADV1.host.magwien.gv.at)
+ifneq ($(PORTNAME), aix)
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(libdir)/$(shlib)'
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
@@ -391,6 +419,7 @@ ifneq ($(shlib), $(shlib_bare))
 endif
 endif # not win32
 endif # not cygwin
+endif # not aix
 ifneq (,$(findstring $(PORTNAME),win32 cygwin))
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(bindir)/$(shlib)'
 endif
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 7344c8c7f5c..572f5430a60 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -63,12 +63,14 @@ all: submake-libpgport submake-catalog-headers submake-utils-headers postgres $(
 
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
+ifneq ($(PORTNAME), aix)
 
 postgres: $(OBJS)
 	$(CC) $(CFLAGS) $(call expand_subsys,$^) $(LDFLAGS) $(LIBS) -o $@
 
 endif
 endif
+endif
 
 ifeq ($(PORTNAME), cygwin)
 
@@ -95,6 +97,24 @@ libpostgres.a: postgres
 
 endif # win32
 
+ifeq ($(PORTNAME), aix)
+
+postgres: $(POSTGRES_IMP)
+	$(CC) $(CFLAGS) $(call expand_subsys,$(OBJS)) $(LDFLAGS) -Wl,-bE:$(top_builddir)/src/backend/$(POSTGRES_IMP) $(LIBS) -Wl,-brtllib -o $@
+
+# Linking to a single .o with -r is a lot faster than building a .a or passing
+# all objects to MKLDEXPORT.
+#
+# It looks alluring to use $(CC) -r instead of ld -r, but that doesn't
+# trivially work with gcc, due to gcc specific static libraries linked in with
+# -r.
+$(POSTGRES_IMP): $(OBJS)
+	ld -r -o SUBSYS.o $(call expand_subsys,$^)
+	$(MKLDEXPORT) SUBSYS.o . > $@
+	@rm -f SUBSYS.o
+
+endif # aix
+
 $(top_builddir)/src/port/libpgport_srv.a: | submake-libpgport
 
 
diff --git a/src/backend/port/aix/mkldexport.sh b/src/backend/port/aix/mkldexport.sh
new file mode 100755
index 00000000000..adf3793e868
--- /dev/null
+++ b/src/backend/port/aix/mkldexport.sh
@@ -0,0 +1,61 @@
+#!/bin/sh
+#
+# mkldexport
+#	create an AIX exports file from an object file
+#
+# src/backend/port/aix/mkldexport.sh
+#
+# Usage:
+#	mkldexport objectfile [location]
+# where
+#	objectfile is the current location of the object file.
+#	location is the eventual (installed) location of the
+#		object file (if different from the current
+#		working directory).
+#
+# [This file comes from the Postgres 4.2 distribution. - ay 7/95]
+#
+# Header: /usr/local/devel/postgres/src/tools/mkldexport/RCS/mkldexport.sh,v 1.2 1994/03/13 04:59:12 aoki Exp
+#
+
+# setting this to nm -B might be better
+# ... due to changes in AIX 4.x ...
+# ... let us search in different directories - Gerhard Reithofer
+if [ -x /usr/ucb/nm ]
+then NM=/usr/ucb/nm
+elif [ -x /usr/bin/nm ]
+then NM=/usr/bin/nm
+elif [ -x /usr/ccs/bin/nm ]
+then NM=/usr/ccs/bin/nm
+elif [ -x /usr/usg/bin/nm ]
+then NM=/usr/usg/bin/nm
+else echo "Fatal error: cannot find `nm' ... please check your installation."
+     exit 1
+fi
+
+CMDNAME=`basename $0`
+if [ -z "$1" ]; then
+	echo "Usage: $CMDNAME object [location]"
+	exit 1
+fi
+OBJNAME=`basename $1`
+if [ "`basename $OBJNAME`" != "`basename $OBJNAME .o`" ]; then
+	OBJNAME=`basename $OBJNAME .o`.so
+fi
+if [ -z "$2" ]; then
+	echo '#!'
+else
+	if [ "$2" = "." ]; then
+		# for the base executable (AIX 4.2 and up)
+		echo '#! .'
+	else
+		echo '#!' $2
+	fi
+fi
+$NM -BCg $1 | \
+	egrep ' [TDB] ' | \
+	sed -e 's/.* //' | \
+	egrep -v '\$' | \
+	sed -e 's/^[.]//' | \
+	sort | \
+	uniq
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 8a6b6905079..3a8e9dc30b0 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -904,7 +904,9 @@ errcode_for_file_access(void)
 			/* Wrong object type or state */
 		case ENOTDIR:			/* Not a directory */
 		case EISDIR:			/* Is a directory */
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:			/* Directory not empty */
+#endif
 			edata->sqlerrcode = ERRCODE_WRONG_OBJECT_TYPE;
 			break;
 
diff --git a/src/include/port/aix.h b/src/include/port/aix.h
new file mode 100644
index 00000000000..7d08480c8c0
--- /dev/null
+++ b/src/include/port/aix.h
@@ -0,0 +1,4 @@
+/*
+ * src/include/port/aix.h
+ */
+
diff --git a/src/include/storage/s_lock.h b/src/include/storage/s_lock.h
index 2f73f9fcf57..5da9b3acda4 100644
--- a/src/include/storage/s_lock.h
+++ b/src/include/storage/s_lock.h
@@ -421,17 +421,15 @@ tas(volatile slock_t *lock)
 	__asm__ __volatile__(
 "	lwarx   %0,0,%3,1	\n"
 "	cmpwi   %0,0		\n"
-"	bne     1f			\n"
+"	bne     $+16		\n"		/* branch to li %1,1 */
 "	addi    %0,%0,1		\n"
 "	stwcx.  %0,0,%3		\n"
-"	beq     2f			\n"
-"1: \n"
+"	beq     $+12		\n"		/* branch to lwsync */
 "	li      %1,1		\n"
-"	b       3f			\n"
-"2: \n"
+"	b       $+12		\n"		/* branch to end of asm sequence */
 "	lwsync				\n"
 "	li      %1,0		\n"
-"3: \n"
+
 :	"=&b"(_t), "=r"(_res), "+m"(*lock)
 :	"r"(lock)
 :	"memory", "cc");
diff --git a/src/makefiles/Makefile.aix b/src/makefiles/Makefile.aix
new file mode 100644
index 00000000000..ab6581533d8
--- /dev/null
+++ b/src/makefiles/Makefile.aix
@@ -0,0 +1,29 @@
+# -blibpath must contain ALL directories where we should look for libraries
+libpath := $(shell echo $(subst -L,:,$(filter -L/%,$(LDFLAGS))) | sed -e's/ //g'):/usr/lib:/lib
+
+# AIX uses a stricter, more explicit approach. The runtime linker expects 
+# to tell it exactly where to look using -blibpath.
+rpath = -Wl,-blibpath:'$(rpathdir)$(libpath)'
+
+# gcc needs to know it's building a shared lib, otherwise it'll not emit
+# correct code / link to the right support libraries
+ifeq ($(GCC), yes)
+LDFLAGS_SL += -shared
+endif
+
+# env var name to use in place of LD_LIBRARY_PATH
+ld_library_path_var = LIBPATH
+
+POSTGRES_IMP= postgres.imp
+
+ifdef PGXS
+BE_DLLLIBS= -Wl,-bI:$(pkglibdir)/$(POSTGRES_IMP)
+else
+BE_DLLLIBS= -Wl,-bI:$(top_builddir)/src/backend/$(POSTGRES_IMP)
+endif
+
+MKLDEXPORT_DIR=src/backend/port/aix
+MKLDEXPORT=$(top_srcdir)/$(MKLDEXPORT_DIR)/mkldexport.sh
+
+%$(DLSUFFIX): %.o
+	$(CC) $(CFLAGS) $*.o $(LDFLAGS) $(LDFLAGS_SL) -o $@ $(BE_DLLLIBS)
diff --git a/src/port/strerror.c b/src/port/strerror.c
index f0746517770..c46b9dc91fc 100644
--- a/src/port/strerror.c
+++ b/src/port/strerror.c
@@ -214,8 +214,10 @@ get_errno_symbol(int errnum)
 			return "ENOTCONN";
 		case ENOTDIR:
 			return "ENOTDIR";
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:
 			return "ENOTEMPTY";
+#endif
 		case ENOTSOCK:
 			return "ENOTSOCK";
 #ifdef ENOTSUP
diff --git a/src/template/aix b/src/template/aix
new file mode 100644
index 00000000000..48a3ce55cf7
--- /dev/null
+++ b/src/template/aix
@@ -0,0 +1,7 @@
+# src/template/aix
+
+# Extra CFLAGS for code that will go into a shared library
+CFLAGS_SL=""
+
+# Native memset() is faster.
+MEMSET_LOOP_LIMIT=0
-- 
2.41.0

diff --git a/src/include/storage/s_lock.h b/src/include/storage/s_lock.h
index 5da9b3acda4..ba120c08d14 100644
--- a/src/include/storage/s_lock.h
+++ b/src/include/storage/s_lock.h
@@ -398,54 +398,18 @@ typedef unsigned int slock_t;

 #define TAS(lock) tas(lock)

-/* On PPC, it's a win to use a non-locking test before the lwarx */
+/* On PPC, use the compiler provided Built-in functions for atomic memory
+ * exchange operations.
+ */
 #define TAS_SPIN(lock) (*(lock) ? 1 : TAS(lock))

-/*
- * The second operand of addi can hold a constant zero or a register number,
- * hence constraint "=&b" to avoid allocating r0.  "b" stands for "address
- * base register"; most operands having this register-or-zero property are
- * address bases, e.g. the second operand of lwax.
- *
- * NOTE: per the Enhanced PowerPC Architecture manual, v1.0 dated 7-May-2002,
- * an isync is a sufficient synchronization barrier after a lwarx/stwcx loop.
- * But if the spinlock is in ordinary memory, we can use lwsync instead for
- * better performance.
- */
 static __inline__ int
 tas(volatile slock_t *lock)
 {
-       slock_t _t;
-       int _res;
-
-       __asm__ __volatile__(
-"      lwarx   %0,0,%3,1       \n"
-"      cmpwi   %0,0            \n"
-"      bne     $+16            \n"             /* branch to li %1,1 */
-"      addi    %0,%0,1         \n"
-"      stwcx.  %0,0,%3         \n"
-"      beq     $+12            \n"             /* branch to lwsync */
-"      li      %1,1            \n"
-"      b       $+12            \n"             /* branch to end of asm sequence */
-"      lwsync                          \n"
-"      li      %1,0            \n"
-
-:      "=&b"(_t), "=r"(_res), "+m"(*lock)
-:      "r"(lock)
-:      "memory", "cc");
-       return _res;
+       return __sync_lock_test_and_set(lock, 1);
 }

-/*
- * PowerPC S_UNLOCK is almost standard but requires a "sync" instruction.
- * But we can use lwsync instead for better performance.
- */
-#define S_UNLOCK(lock) \
-do \
-{ \
-       __asm__ __volatile__ (" lwsync \n" ::: "memory"); \
-       *((volatile slock_t *) (lock)) = 0; \
-} while (0)
+#define S_UNLOCK(lock) __sync_lock_release(lock)

 #endif /* powerpc */

diff --git a/src/makefiles/Makefile.aix b/src/makefiles/Makefile.aix
index ab6581533d8..4c4de8b0be7 100644
--- a/src/makefiles/Makefile.aix
+++ b/src/makefiles/Makefile.aix
@@ -1,3 +1,8 @@
+# -blibpath:
+# The path to be inserted into the default path (Index 0 path) field of the
+# loader section. When this flag is presented, the -L paths will not be stored.
+# AIX uses a stricter, more explicit approach. The runtime linker expects to
+# tell it exactly where to look using -blibpath.
 # -blibpath must contain ALL directories where we should look for libraries
 libpath := $(shell echo $(subst -L,:,$(filter -L/%,$(LDFLAGS))) | sed -e's/ //g'):/usr/lib:/lib

diff --git a/src/template/aix b/src/template/aix
index 48a3ce55cf7..ea7f7fb3487 100644
--- a/src/template/aix
+++ b/src/template/aix
@@ -1,7 +1,8 @@
+# This file is referred for specific flags wrt to AIX build process like
+# cflags.
 # src/template/aix

 # Extra CFLAGS for code that will go into a shared library
-CFLAGS_SL=""
+# With optimization, the MemSet() and MemSetAlign() perform better.
+CFLAGS_SL=" -O2 "

-# Native memset() is faster.
-MEMSET_LOOP_LIMIT=0

From c854025252ca3dfff9f7f1c4d4aed21cf0cf5346 Mon Sep 17 00:00:00 2001
From: Sriram RK <sriram.rk@in.ibm.com>
Date: Fri, 4 Apr 2025 13:16:21 -0500
Subject: [PATCH] AIX support.

---
 Makefile                           |  2 -
 configure                          | 34 ++++++++++++++---
 configure.ac                       | 34 ++++++++++++++---
 src/Makefile.shlib                 | 29 ++++++++++++++
 src/backend/Makefile               | 20 ++++++++++
 src/backend/port/aix/mkldexport.sh | 61 ++++++++++++++++++++++++++++++
 src/backend/utils/error/elog.c     |  2 +
 src/include/port/aix.h             |  4 ++
 src/include/storage/s_lock.h       | 10 ++---
 src/makefiles/Makefile.aix         | 29 ++++++++++++++
 src/port/strerror.c                |  2 +
 src/template/aix                   |  7 ++++
 12 files changed, 214 insertions(+), 20 deletions(-)
 create mode 100755 src/backend/port/aix/mkldexport.sh
 create mode 100644 src/include/port/aix.h
 create mode 100644 src/makefiles/Makefile.aix
 create mode 100644 src/template/aix

diff --git a/Makefile b/Makefile
index 8a2ec9396b6..9bc1a4ec17b 100644
--- a/Makefile
+++ b/Makefile
@@ -13,8 +13,6 @@
 
 # AIX make defaults to building *every* target of the first rule.  Start with
 # a single-target, empty rule to make the other targets non-default.
-# (We don't support AIX anymore, but if someone tries to build on AIX anyway,
-# at least they'll get the instructions to run 'configure' first.)
 all:
 
 all check install installdirs installcheck installcheck-parallel uninstall clean distclean maintainer-clean dist distcheck world check-world install-world installcheck-world:
diff --git a/configure b/configure
index 11615d1122d..6088fa26679 100755
--- a/configure
+++ b/configure
@@ -3008,6 +3008,7 @@ else
 # --with-template not given
 
 case $host_os in
+  aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -16953,13 +16954,34 @@ _ACEOF
 # wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
 # much of a penalty for disk and memory space.
 
-MAX_ALIGNOF=$ac_cv_alignof_double
+if test "$PORTNAME" != "aix"; then
+    MAX_ALIGNOF=$ac_cv_alignof_double
+
+    if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
+      as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+    if test $ac_cv_alignof_int64_t -gt $MAX_ALIGNOF ; then
+      as_fn_error $? "alignment of 'long long int' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+else
+# The AIX 'power' alignment rules apply the natural alignment of the "first
+# member" if it is of a floating-point data type (or is an aggregate whose
+# recursively "first" member or element is such a type). The alignment
+# associated with these types for subsequent members use an alignment value
+# where the floating-point data type is considered to have 4-byte alignment.
+# More info
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99557
+#
+# The double is aligned to 4-bytes on AIX in aggregates. But to maintain
+# alignement across platforms the max alignment of long should be considered.
+    MAX_ALIGNOF=$ac_cv_alignof_long
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_double ; then
+      MAX_ALIGNOF=$ac_cv_alignof_double
+    fi
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_int64_t; then
+      MAX_ALIGNOF="$ac_cv_alignof_int64_t"
+    fi
 
-if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
-fi
-if test $ac_cv_alignof_int64_t -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'int64_t' is greater than the alignment of 'double'" "$LINENO" 5
 fi
 
 cat >>confdefs.h <<_ACEOF
diff --git a/configure.ac b/configure.ac
index debdf165044..c21aaa52064 100644
--- a/configure.ac
+++ b/configure.ac
@@ -62,6 +62,7 @@ PGAC_ARG_REQ(with, template, [NAME], [override operating system template],
 # --with-template not given
 
 case $host_os in
+  aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -1987,13 +1988,34 @@ AC_CHECK_ALIGNOF(double)
 # wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
 # much of a penalty for disk and memory space.
 
-MAX_ALIGNOF=$ac_cv_alignof_double
+if test "$PORTNAME" != "aix"; then
+    MAX_ALIGNOF=$ac_cv_alignof_double
+
+    if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
+      as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+    if test $ac_cv_alignof_int64_t -gt $MAX_ALIGNOF; then
+      as_fn_error $? "alignment of 'long long int' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+else
+# The AIX 'power' alignment rules apply the natural alignment of the "first
+# member" if it is of a floating-point data type (or is an aggregate whose
+# recursively "first" member or element is such a type). The alignment
+# associated with these types for subsequent members use an alignment value
+# where the floating-point data type is considered to have 4-byte alignment.
+# More info
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99557
+# 
+# The double is aligned to 4-bytes on AIX in aggregates. But to maintain
+# alignement across platforms the max alignment of long should be considered.
+    MAX_ALIGNOF=$ac_cv_alignof_long
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_double ; then
+      MAX_ALIGNOF=$ac_cv_alignof_double
+    fi
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_int64_t ; then
+      MAX_ALIGNOF="$ac_cv_alignof_int64_t"
+    fi
 
-if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
-  AC_MSG_ERROR([alignment of 'long' is greater than the alignment of 'double'])
-fi
-if test $ac_cv_alignof_int64_t -gt $MAX_ALIGNOF ; then
-  AC_MSG_ERROR([alignment of 'int64_t' is greater than the alignment of 'double'])
 fi
 AC_DEFINE_UNQUOTED(MAXIMUM_ALIGNOF, $MAX_ALIGNOF, [Define as the maximum alignment requirement of any C data type.])
 
diff --git a/src/Makefile.shlib b/src/Makefile.shlib
index fa81f6ffdd6..13ea84ac185 100644
--- a/src/Makefile.shlib
+++ b/src/Makefile.shlib
@@ -106,6 +106,20 @@ ifdef SO_MAJOR_VERSION
 override CPPFLAGS += -DSO_MAJOR_VERSION=$(SO_MAJOR_VERSION)
 endif
 
+ifeq ($(PORTNAME), aix)
+  LINK.shared		= $(COMPILER)
+  ifdef SO_MAJOR_VERSION
+    shlib		= lib$(NAME)$(DLSUFFIX).$(SO_MAJOR_VERSION)
+  endif
+  haslibarule   = yes
+  # $(exports_file) is also usable as an import file
+  exports_file		= lib$(NAME).exp
+  BUILD.exports		= ( echo '\#! $(shlib)'; $(AWK) '/^[^\#]/ {printf "%s\n",$$1}' $< ) > $@
+  ifneq (,$(SHLIB_EXPORTS))
+    LINK.shared		+= -Wl,-bE:$(exports_file)
+  endif
+endif
+
 ifeq ($(PORTNAME), darwin)
   ifdef soname
     # linkable library
@@ -254,6 +268,14 @@ $(stlib): $(OBJS) | $(SHLIB_PREREQS)
 	touch $@
 endif #haslibarule
 
+# AIX wraps both shared libraries and static library, which can be used both
+# for static and shared linking
+ifeq ($(PORTNAME), aix)
+$(stlib): $(shlib)
+	rm -f $(stlib)
+	$(AR) $(AROPT) $(stlib) $(shlib)
+endif # aix
+
 ifeq (,$(filter cygwin win32,$(PORTNAME)))
 
 # Normal case
@@ -267,8 +289,11 @@ ifneq ($(shlib), $(shlib_major))
 endif
 # Make sure we have a link to a name without any version numbers
 ifneq ($(shlib), $(shlib_bare))
+# except on AIX, where that's not a thing
+ifneq ($(PORTNAME), aix)
 	rm -f $(shlib_bare)
 	$(LN_S) $(shlib) $(shlib_bare)
+endif # aix
 endif # shlib_bare
 endif # shlib_major
 
@@ -376,6 +401,9 @@ install-lib-static: $(stlib) installdirs-lib
 
 install-lib-shared: $(shlib) installdirs-lib
 ifdef soname
+# we don't install $(shlib) on AIX
+# (see http://archives.postgresql.org/message-id/52EF20B2E3209443BC37736D00C3C1380A6E79FE@EXADV1.host.magwien.gv.at)
+ifneq ($(PORTNAME), aix)
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(libdir)/$(shlib)'
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
@@ -391,6 +419,7 @@ ifneq ($(shlib), $(shlib_bare))
 endif
 endif # not win32
 endif # not cygwin
+endif # not aix
 ifneq (,$(findstring $(PORTNAME),win32 cygwin))
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(bindir)/$(shlib)'
 endif
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 7344c8c7f5c..572f5430a60 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -63,12 +63,14 @@ all: submake-libpgport submake-catalog-headers submake-utils-headers postgres $(
 
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
+ifneq ($(PORTNAME), aix)
 
 postgres: $(OBJS)
 	$(CC) $(CFLAGS) $(call expand_subsys,$^) $(LDFLAGS) $(LIBS) -o $@
 
 endif
 endif
+endif
 
 ifeq ($(PORTNAME), cygwin)
 
@@ -95,6 +97,24 @@ libpostgres.a: postgres
 
 endif # win32
 
+ifeq ($(PORTNAME), aix)
+
+postgres: $(POSTGRES_IMP)
+	$(CC) $(CFLAGS) $(call expand_subsys,$(OBJS)) $(LDFLAGS) -Wl,-bE:$(top_builddir)/src/backend/$(POSTGRES_IMP) $(LIBS) -Wl,-brtllib -o $@
+
+# Linking to a single .o with -r is a lot faster than building a .a or passing
+# all objects to MKLDEXPORT.
+#
+# It looks alluring to use $(CC) -r instead of ld -r, but that doesn't
+# trivially work with gcc, due to gcc specific static libraries linked in with
+# -r.
+$(POSTGRES_IMP): $(OBJS)
+	ld -r -o SUBSYS.o $(call expand_subsys,$^)
+	$(MKLDEXPORT) SUBSYS.o . > $@
+	@rm -f SUBSYS.o
+
+endif # aix
+
 $(top_builddir)/src/port/libpgport_srv.a: | submake-libpgport
 
 
diff --git a/src/backend/port/aix/mkldexport.sh b/src/backend/port/aix/mkldexport.sh
new file mode 100755
index 00000000000..adf3793e868
--- /dev/null
+++ b/src/backend/port/aix/mkldexport.sh
@@ -0,0 +1,61 @@
+#!/bin/sh
+#
+# mkldexport
+#	create an AIX exports file from an object file
+#
+# src/backend/port/aix/mkldexport.sh
+#
+# Usage:
+#	mkldexport objectfile [location]
+# where
+#	objectfile is the current location of the object file.
+#	location is the eventual (installed) location of the
+#		object file (if different from the current
+#		working directory).
+#
+# [This file comes from the Postgres 4.2 distribution. - ay 7/95]
+#
+# Header: /usr/local/devel/postgres/src/tools/mkldexport/RCS/mkldexport.sh,v 1.2 1994/03/13 04:59:12 aoki Exp
+#
+
+# setting this to nm -B might be better
+# ... due to changes in AIX 4.x ...
+# ... let us search in different directories - Gerhard Reithofer
+if [ -x /usr/ucb/nm ]
+then NM=/usr/ucb/nm
+elif [ -x /usr/bin/nm ]
+then NM=/usr/bin/nm
+elif [ -x /usr/ccs/bin/nm ]
+then NM=/usr/ccs/bin/nm
+elif [ -x /usr/usg/bin/nm ]
+then NM=/usr/usg/bin/nm
+else echo "Fatal error: cannot find `nm' ... please check your installation."
+     exit 1
+fi
+
+CMDNAME=`basename $0`
+if [ -z "$1" ]; then
+	echo "Usage: $CMDNAME object [location]"
+	exit 1
+fi
+OBJNAME=`basename $1`
+if [ "`basename $OBJNAME`" != "`basename $OBJNAME .o`" ]; then
+	OBJNAME=`basename $OBJNAME .o`.so
+fi
+if [ -z "$2" ]; then
+	echo '#!'
+else
+	if [ "$2" = "." ]; then
+		# for the base executable (AIX 4.2 and up)
+		echo '#! .'
+	else
+		echo '#!' $2
+	fi
+fi
+$NM -BCg $1 | \
+	egrep ' [TDB] ' | \
+	sed -e 's/.* //' | \
+	egrep -v '\$' | \
+	sed -e 's/^[.]//' | \
+	sort | \
+	uniq
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 8a6b6905079..3a8e9dc30b0 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -904,7 +904,9 @@ errcode_for_file_access(void)
 			/* Wrong object type or state */
 		case ENOTDIR:			/* Not a directory */
 		case EISDIR:			/* Is a directory */
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:			/* Directory not empty */
+#endif
 			edata->sqlerrcode = ERRCODE_WRONG_OBJECT_TYPE;
 			break;
 
diff --git a/src/include/port/aix.h b/src/include/port/aix.h
new file mode 100644
index 00000000000..7d08480c8c0
--- /dev/null
+++ b/src/include/port/aix.h
@@ -0,0 +1,4 @@
+/*
+ * src/include/port/aix.h
+ */
+
diff --git a/src/include/storage/s_lock.h b/src/include/storage/s_lock.h
index 2f73f9fcf57..5da9b3acda4 100644
--- a/src/include/storage/s_lock.h
+++ b/src/include/storage/s_lock.h
@@ -421,17 +421,15 @@ tas(volatile slock_t *lock)
 	__asm__ __volatile__(
 "	lwarx   %0,0,%3,1	\n"
 "	cmpwi   %0,0		\n"
-"	bne     1f			\n"
+"	bne     $+16		\n"		/* branch to li %1,1 */
 "	addi    %0,%0,1		\n"
 "	stwcx.  %0,0,%3		\n"
-"	beq     2f			\n"
-"1: \n"
+"	beq     $+12		\n"		/* branch to lwsync */
 "	li      %1,1		\n"
-"	b       3f			\n"
-"2: \n"
+"	b       $+12		\n"		/* branch to end of asm sequence */
 "	lwsync				\n"
 "	li      %1,0		\n"
-"3: \n"
+
 :	"=&b"(_t), "=r"(_res), "+m"(*lock)
 :	"r"(lock)
 :	"memory", "cc");
diff --git a/src/makefiles/Makefile.aix b/src/makefiles/Makefile.aix
new file mode 100644
index 00000000000..ab6581533d8
--- /dev/null
+++ b/src/makefiles/Makefile.aix
@@ -0,0 +1,29 @@
+# -blibpath must contain ALL directories where we should look for libraries
+libpath := $(shell echo $(subst -L,:,$(filter -L/%,$(LDFLAGS))) | sed -e's/ //g'):/usr/lib:/lib
+
+# AIX uses a stricter, more explicit approach. The runtime linker expects 
+# to tell it exactly where to look using -blibpath.
+rpath = -Wl,-blibpath:'$(rpathdir)$(libpath)'
+
+# gcc needs to know it's building a shared lib, otherwise it'll not emit
+# correct code / link to the right support libraries
+ifeq ($(GCC), yes)
+LDFLAGS_SL += -shared
+endif
+
+# env var name to use in place of LD_LIBRARY_PATH
+ld_library_path_var = LIBPATH
+
+POSTGRES_IMP= postgres.imp
+
+ifdef PGXS
+BE_DLLLIBS= -Wl,-bI:$(pkglibdir)/$(POSTGRES_IMP)
+else
+BE_DLLLIBS= -Wl,-bI:$(top_builddir)/src/backend/$(POSTGRES_IMP)
+endif
+
+MKLDEXPORT_DIR=src/backend/port/aix
+MKLDEXPORT=$(top_srcdir)/$(MKLDEXPORT_DIR)/mkldexport.sh
+
+%$(DLSUFFIX): %.o
+	$(CC) $(CFLAGS) $*.o $(LDFLAGS) $(LDFLAGS_SL) -o $@ $(BE_DLLLIBS)
diff --git a/src/port/strerror.c b/src/port/strerror.c
index f0746517770..c46b9dc91fc 100644
--- a/src/port/strerror.c
+++ b/src/port/strerror.c
@@ -214,8 +214,10 @@ get_errno_symbol(int errnum)
 			return "ENOTCONN";
 		case ENOTDIR:
 			return "ENOTDIR";
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:
 			return "ENOTEMPTY";
+#endif
 		case ENOTSOCK:
 			return "ENOTSOCK";
 #ifdef ENOTSUP
diff --git a/src/template/aix b/src/template/aix
new file mode 100644
index 00000000000..48a3ce55cf7
--- /dev/null
+++ b/src/template/aix
@@ -0,0 +1,7 @@
+# src/template/aix
+
+# Extra CFLAGS for code that will go into a shared library
+CFLAGS_SL=""
+
+# Native memset() is faster.
+MEMSET_LOOP_LIMIT=0
-- 
2.41.0

From 24e96d9849f3e6a6217a284aff717ad4d7f2d45a Mon Sep 17 00:00:00 2001
From: AIX-dev <postgres-ibm-aix@wwpdl.vnet.ibm.com>
Date: Wed, 3 Sep 2025 09:37:14 -0500
Subject: [PATCH] AIX support.

---
 Makefile                           |  2 -
 configure                          | 37 +++++++++++++++---
 configure.ac                       | 29 +++++++++++++-
 src/Makefile.shlib                 | 29 ++++++++++++++
 src/backend/Makefile               | 20 ++++++++++
 src/backend/port/aix/mkldexport.sh | 61 ++++++++++++++++++++++++++++++
 src/backend/utils/error/elog.c     |  2 +
 src/include/port/aix.h             |  4 ++
 src/include/storage/s_lock.h       | 48 +++--------------------
 src/makefiles/Makefile.aix         | 34 +++++++++++++++++
 src/port/strerror.c                |  2 +
 src/template/aix                   |  7 ++++
 12 files changed, 223 insertions(+), 52 deletions(-)
 create mode 100755 src/backend/port/aix/mkldexport.sh
 create mode 100644 src/include/port/aix.h
 create mode 100644 src/makefiles/Makefile.aix
 create mode 100644 src/template/aix

diff --git a/Makefile b/Makefile
index b363b2f2476..786424613ab 100644
--- a/Makefile
+++ b/Makefile
@@ -13,8 +13,6 @@
 
 # AIX make defaults to building *every* target of the first rule.  Start with
 # a single-target, empty rule to make the other targets non-default.
-# (We don't support AIX anymore, but if someone tries to build on AIX anyway,
-# at least they'll get the instructions to run 'configure' first.)
 all:
 
 all check install installdirs installcheck installcheck-parallel uninstall clean distclean maintainer-clean dist distcheck world check-world install-world installcheck-world:
diff --git a/configure b/configure
index 1b9980226c5..abda4be633e 100755
--- a/configure
+++ b/configure
@@ -3022,6 +3022,7 @@ else
 # --with-template not given
 
 case $host_os in
+  aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -17204,13 +17205,37 @@ _ACEOF
 # wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
 # much of a penalty for disk and memory space.
 
-MAX_ALIGNOF=$ac_cv_alignof_double
+echo "Checking for MAX ALIGN - $PORTNAME"
+if test "$PORTNAME" != "aix"; then
+    MAX_ALIGNOF=$ac_cv_alignof_double
 
-if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
-fi
-if test $ac_cv_alignof_int64_t -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'int64_t' is greater than the alignment of 'double'" "$LINENO" 5
+    if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
+      as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+    if test x"$HAVE_LONG_LONG_INT_64" = xyes && test $ac_cv_alignof_long_long_int -gt $MAX_ALIGNOF ; then
+      as_fn_error $? "alignment of 'long long int' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+else
+# The AIX 'power' alignment rules apply the natural alignment of the "first
+# member" if it is of a floating-point data type (or is an aggregate whose
+# recursively "first" member or element is such a type). The alignment
+# associated with these types for subsequent members use an alignment value
+# where the floating-point data type is considered to have 4-byte alignment.
+# More info
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99557
+#
+# The double is aligned to 4-bytes on AIX in aggregates. But to maintain
+# alignement across platforms the max alignment of long should be considered.
+      echo "MAX ALIGN ac_cv_alignof_long"
+    MAX_ALIGNOF=$ac_cv_alignof_long
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_double ; then
+      MAX_ALIGNOF=$ac_cv_alignof_double
+      echo "MAX ALIGN ac_cv_alignof_double"
+    fi
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_int64_t; then
+      MAX_ALIGNOF="$ac_cv_alignof_int64_t"
+      echo "MAX ALIGN ac_cv_alignof_int64_t"
+    fi
 fi
 
 cat >>confdefs.h <<_ACEOF
diff --git a/configure.ac b/configure.ac
index 3e3fcfa9831..1ef58a1d7a0 100644
--- a/configure.ac
+++ b/configure.ac
@@ -62,6 +62,7 @@ PGAC_ARG_REQ(with, template, [NAME], [override operating system template],
 # --with-template not given
 
 case $host_os in
+  aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -2021,7 +2022,33 @@ AC_CHECK_ALIGNOF(double)
 # wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
 # much of a penalty for disk and memory space.
 
-MAX_ALIGNOF=$ac_cv_alignof_double
+if test "$PORTNAME" != "aix"; then
+    MAX_ALIGNOF=$ac_cv_alignof_double
+
+    if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
+      as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+    if test $ac_cv_alignof_int64_t -gt $MAX_ALIGNOF; then
+      as_fn_error $? "alignment of 'long long int' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+else
+# The AIX 'power' alignment rules apply the natural alignment of the "first
+# member" if it is of a floating-point data type (or is an aggregate whose
+# recursively "first" member or element is such a type). The alignment
+# associated with these types for subsequent members use an alignment value
+# where the floating-point data type is considered to have 4-byte alignment.
+# More info
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99557
+# 
+# The double is aligned to 4-bytes on AIX in aggregates. But to maintain
+# alignement across platforms the max alignment of long should be considered.
+    MAX_ALIGNOF=$ac_cv_alignof_long
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_double ; then
+      MAX_ALIGNOF=$ac_cv_alignof_double
+    fi
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_int64_t ; then
+      MAX_ALIGNOF="$ac_cv_alignof_int64_t"
+    fi
 
 if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
   AC_MSG_ERROR([alignment of 'long' is greater than the alignment of 'double'])
diff --git a/src/Makefile.shlib b/src/Makefile.shlib
index 3825af5b228..35adc4174ed 100644
--- a/src/Makefile.shlib
+++ b/src/Makefile.shlib
@@ -106,6 +106,20 @@ ifdef SO_MAJOR_VERSION
 override CPPFLAGS += -DSO_MAJOR_VERSION=$(SO_MAJOR_VERSION)
 endif
 
+ifeq ($(PORTNAME), aix)
+  LINK.shared		= $(COMPILER)
+  ifdef SO_MAJOR_VERSION
+    shlib		= lib$(NAME)$(DLSUFFIX).$(SO_MAJOR_VERSION)
+  endif
+  haslibarule   = yes
+  # $(exports_file) is also usable as an import file
+  exports_file		= lib$(NAME).exp
+  BUILD.exports		= ( echo '\#! $(shlib)'; $(AWK) '/^[^\#]/ {printf "%s\n",$$1}' $< ) > $@
+  ifneq (,$(SHLIB_EXPORTS))
+    LINK.shared		+= -Wl,-bE:$(exports_file)
+  endif
+endif
+
 ifeq ($(PORTNAME), darwin)
   ifdef soname
     # linkable library
@@ -254,6 +268,14 @@ $(stlib): $(OBJS) | $(SHLIB_PREREQS)
 	touch $@
 endif #haslibarule
 
+# AIX wraps both shared libraries and static library, which can be used both
+# for static and shared linking
+ifeq ($(PORTNAME), aix)
+$(stlib): $(shlib)
+	rm -f $(stlib)
+	$(AR) $(AROPT) $(stlib) $(shlib)
+endif # aix
+
 ifeq (,$(filter cygwin win32,$(PORTNAME)))
 
 # Normal case
@@ -267,8 +289,11 @@ ifneq ($(shlib), $(shlib_major))
 endif
 # Make sure we have a link to a name without any version numbers
 ifneq ($(shlib), $(shlib_bare))
+# except on AIX, where that's not a thing
+ifneq ($(PORTNAME), aix)
 	rm -f $(shlib_bare)
 	$(LN_S) $(shlib) $(shlib_bare)
+endif # aix
 endif # shlib_bare
 endif # shlib_major
 
@@ -376,6 +401,9 @@ install-lib-static: $(stlib) installdirs-lib
 
 install-lib-shared: $(shlib) installdirs-lib
 ifdef soname
+# we don't install $(shlib) on AIX
+# (see http://archives.postgresql.org/message-id/52EF20B2E3209443BC37736D00C3C1380A6E79FE@EXADV1.host.magwien.gv.at)
+ifneq ($(PORTNAME), aix)
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(libdir)/$(shlib)'
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
@@ -391,6 +419,7 @@ ifneq ($(shlib), $(shlib_bare))
 endif
 endif # not win32
 endif # not cygwin
+endif # not aix
 ifneq (,$(findstring $(PORTNAME),win32 cygwin))
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(bindir)/$(shlib)'
 endif
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 7344c8c7f5c..572f5430a60 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -63,12 +63,14 @@ all: submake-libpgport submake-catalog-headers submake-utils-headers postgres $(
 
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
+ifneq ($(PORTNAME), aix)
 
 postgres: $(OBJS)
 	$(CC) $(CFLAGS) $(call expand_subsys,$^) $(LDFLAGS) $(LIBS) -o $@
 
 endif
 endif
+endif
 
 ifeq ($(PORTNAME), cygwin)
 
@@ -95,6 +97,24 @@ libpostgres.a: postgres
 
 endif # win32
 
+ifeq ($(PORTNAME), aix)
+
+postgres: $(POSTGRES_IMP)
+	$(CC) $(CFLAGS) $(call expand_subsys,$(OBJS)) $(LDFLAGS) -Wl,-bE:$(top_builddir)/src/backend/$(POSTGRES_IMP) $(LIBS) -Wl,-brtllib -o $@
+
+# Linking to a single .o with -r is a lot faster than building a .a or passing
+# all objects to MKLDEXPORT.
+#
+# It looks alluring to use $(CC) -r instead of ld -r, but that doesn't
+# trivially work with gcc, due to gcc specific static libraries linked in with
+# -r.
+$(POSTGRES_IMP): $(OBJS)
+	ld -r -o SUBSYS.o $(call expand_subsys,$^)
+	$(MKLDEXPORT) SUBSYS.o . > $@
+	@rm -f SUBSYS.o
+
+endif # aix
+
 $(top_builddir)/src/port/libpgport_srv.a: | submake-libpgport
 
 
diff --git a/src/backend/port/aix/mkldexport.sh b/src/backend/port/aix/mkldexport.sh
new file mode 100755
index 00000000000..adf3793e868
--- /dev/null
+++ b/src/backend/port/aix/mkldexport.sh
@@ -0,0 +1,61 @@
+#!/bin/sh
+#
+# mkldexport
+#	create an AIX exports file from an object file
+#
+# src/backend/port/aix/mkldexport.sh
+#
+# Usage:
+#	mkldexport objectfile [location]
+# where
+#	objectfile is the current location of the object file.
+#	location is the eventual (installed) location of the
+#		object file (if different from the current
+#		working directory).
+#
+# [This file comes from the Postgres 4.2 distribution. - ay 7/95]
+#
+# Header: /usr/local/devel/postgres/src/tools/mkldexport/RCS/mkldexport.sh,v 1.2 1994/03/13 04:59:12 aoki Exp
+#
+
+# setting this to nm -B might be better
+# ... due to changes in AIX 4.x ...
+# ... let us search in different directories - Gerhard Reithofer
+if [ -x /usr/ucb/nm ]
+then NM=/usr/ucb/nm
+elif [ -x /usr/bin/nm ]
+then NM=/usr/bin/nm
+elif [ -x /usr/ccs/bin/nm ]
+then NM=/usr/ccs/bin/nm
+elif [ -x /usr/usg/bin/nm ]
+then NM=/usr/usg/bin/nm
+else echo "Fatal error: cannot find `nm' ... please check your installation."
+     exit 1
+fi
+
+CMDNAME=`basename $0`
+if [ -z "$1" ]; then
+	echo "Usage: $CMDNAME object [location]"
+	exit 1
+fi
+OBJNAME=`basename $1`
+if [ "`basename $OBJNAME`" != "`basename $OBJNAME .o`" ]; then
+	OBJNAME=`basename $OBJNAME .o`.so
+fi
+if [ -z "$2" ]; then
+	echo '#!'
+else
+	if [ "$2" = "." ]; then
+		# for the base executable (AIX 4.2 and up)
+		echo '#! .'
+	else
+		echo '#!' $2
+	fi
+fi
+$NM -BCg $1 | \
+	egrep ' [TDB] ' | \
+	sed -e 's/.* //' | \
+	egrep -v '\$' | \
+	sed -e 's/^[.]//' | \
+	sort | \
+	uniq
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 47af743990f..f0f4ff051b5 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -905,7 +905,9 @@ errcode_for_file_access(void)
 			/* Wrong object type or state */
 		case ENOTDIR:			/* Not a directory */
 		case EISDIR:			/* Is a directory */
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:			/* Directory not empty */
+#endif
 			edata->sqlerrcode = ERRCODE_WRONG_OBJECT_TYPE;
 			break;
 
diff --git a/src/include/port/aix.h b/src/include/port/aix.h
new file mode 100644
index 00000000000..7d08480c8c0
--- /dev/null
+++ b/src/include/port/aix.h
@@ -0,0 +1,4 @@
+/*
+ * src/include/port/aix.h
+ */
+
diff --git a/src/include/storage/s_lock.h b/src/include/storage/s_lock.h
index 2f73f9fcf57..ba120c08d14 100644
--- a/src/include/storage/s_lock.h
+++ b/src/include/storage/s_lock.h
@@ -398,56 +398,18 @@ typedef unsigned int slock_t;
 
 #define TAS(lock) tas(lock)
 
-/* On PPC, it's a win to use a non-locking test before the lwarx */
+/* On PPC, use the compiler provided Built-in functions for atomic memory
+ * exchange operations.
+ */
 #define TAS_SPIN(lock)	(*(lock) ? 1 : TAS(lock))
 
-/*
- * The second operand of addi can hold a constant zero or a register number,
- * hence constraint "=&b" to avoid allocating r0.  "b" stands for "address
- * base register"; most operands having this register-or-zero property are
- * address bases, e.g. the second operand of lwax.
- *
- * NOTE: per the Enhanced PowerPC Architecture manual, v1.0 dated 7-May-2002,
- * an isync is a sufficient synchronization barrier after a lwarx/stwcx loop.
- * But if the spinlock is in ordinary memory, we can use lwsync instead for
- * better performance.
- */
 static __inline__ int
 tas(volatile slock_t *lock)
 {
-	slock_t _t;
-	int _res;
-
-	__asm__ __volatile__(
-"	lwarx   %0,0,%3,1	\n"
-"	cmpwi   %0,0		\n"
-"	bne     1f			\n"
-"	addi    %0,%0,1		\n"
-"	stwcx.  %0,0,%3		\n"
-"	beq     2f			\n"
-"1: \n"
-"	li      %1,1		\n"
-"	b       3f			\n"
-"2: \n"
-"	lwsync				\n"
-"	li      %1,0		\n"
-"3: \n"
-:	"=&b"(_t), "=r"(_res), "+m"(*lock)
-:	"r"(lock)
-:	"memory", "cc");
-	return _res;
+	return __sync_lock_test_and_set(lock, 1);
 }
 
-/*
- * PowerPC S_UNLOCK is almost standard but requires a "sync" instruction.
- * But we can use lwsync instead for better performance.
- */
-#define S_UNLOCK(lock)	\
-do \
-{ \
-	__asm__ __volatile__ ("	lwsync \n" ::: "memory"); \
-	*((volatile slock_t *) (lock)) = 0; \
-} while (0)
+#define S_UNLOCK(lock) __sync_lock_release(lock)
 
 #endif /* powerpc */
 
diff --git a/src/makefiles/Makefile.aix b/src/makefiles/Makefile.aix
new file mode 100644
index 00000000000..4c4de8b0be7
--- /dev/null
+++ b/src/makefiles/Makefile.aix
@@ -0,0 +1,34 @@
+# -blibpath:
+# The path to be inserted into the default path (Index 0 path) field of the
+# loader section. When this flag is presented, the -L paths will not be stored. 
+# AIX uses a stricter, more explicit approach. The runtime linker expects to
+# tell it exactly where to look using -blibpath.
+# -blibpath must contain ALL directories where we should look for libraries
+libpath := $(shell echo $(subst -L,:,$(filter -L/%,$(LDFLAGS))) | sed -e's/ //g'):/usr/lib:/lib
+
+# AIX uses a stricter, more explicit approach. The runtime linker expects 
+# to tell it exactly where to look using -blibpath.
+rpath = -Wl,-blibpath:'$(rpathdir)$(libpath)'
+
+# gcc needs to know it's building a shared lib, otherwise it'll not emit
+# correct code / link to the right support libraries
+ifeq ($(GCC), yes)
+LDFLAGS_SL += -shared
+endif
+
+# env var name to use in place of LD_LIBRARY_PATH
+ld_library_path_var = LIBPATH
+
+POSTGRES_IMP= postgres.imp
+
+ifdef PGXS
+BE_DLLLIBS= -Wl,-bI:$(pkglibdir)/$(POSTGRES_IMP)
+else
+BE_DLLLIBS= -Wl,-bI:$(top_builddir)/src/backend/$(POSTGRES_IMP)
+endif
+
+MKLDEXPORT_DIR=src/backend/port/aix
+MKLDEXPORT=$(top_srcdir)/$(MKLDEXPORT_DIR)/mkldexport.sh
+
+%$(DLSUFFIX): %.o
+	$(CC) $(CFLAGS) $*.o $(LDFLAGS) $(LDFLAGS_SL) -o $@ $(BE_DLLLIBS)
diff --git a/src/port/strerror.c b/src/port/strerror.c
index f0746517770..c46b9dc91fc 100644
--- a/src/port/strerror.c
+++ b/src/port/strerror.c
@@ -214,8 +214,10 @@ get_errno_symbol(int errnum)
 			return "ENOTCONN";
 		case ENOTDIR:
 			return "ENOTDIR";
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:
 			return "ENOTEMPTY";
+#endif
 		case ENOTSOCK:
 			return "ENOTSOCK";
 #ifdef ENOTSUP
diff --git a/src/template/aix b/src/template/aix
new file mode 100644
index 00000000000..bfc193348f4
--- /dev/null
+++ b/src/template/aix
@@ -0,0 +1,7 @@
+# This file is referred for specific flags wrt to AIX build process like
+# cflags.
+# src/template/aix
+
+# Extra CFLAGS for code that will go into a shared library
+# With optimization, the MemSet() and MemSetAlign() perform better.
+CFLAGS_SL=" -O2 "
-- 
2.41.0

From 407b42b1fbe562dff69820f7456dbb32a8a37d79 Mon Sep 17 00:00:00 2001
From: AIX-dev <postgres-ibm-aix@wwpdl.vnet.ibm.com>
Date: Tue, 16 Sep 2025 08:59:22 -0500
Subject: [PATCH] Changes to add support for AIX.

---
 Makefile                           |  2 -
 configure                          | 37 +++++++++++++++---
 configure.ac                       | 29 +++++++++++++-
 src/Makefile.shlib                 | 29 ++++++++++++++
 src/backend/Makefile               | 20 ++++++++++
 src/backend/port/aix/mkldexport.sh | 61 ++++++++++++++++++++++++++++++
 src/backend/utils/error/elog.c     |  2 +
 src/include/port/aix.h             |  4 ++
 src/include/storage/s_lock.h       | 48 +++--------------------
 src/makefiles/Makefile.aix         | 34 +++++++++++++++++
 src/port/strerror.c                |  2 +
 src/template/aix                   |  7 ++++
 12 files changed, 223 insertions(+), 52 deletions(-)
 create mode 100755 src/backend/port/aix/mkldexport.sh
 create mode 100644 src/include/port/aix.h
 create mode 100644 src/makefiles/Makefile.aix
 create mode 100644 src/template/aix

diff --git a/Makefile b/Makefile
index 8a2ec9396b6..9bc1a4ec17b 100644
--- a/Makefile
+++ b/Makefile
@@ -13,8 +13,6 @@
 
 # AIX make defaults to building *every* target of the first rule.  Start with
 # a single-target, empty rule to make the other targets non-default.
-# (We don't support AIX anymore, but if someone tries to build on AIX anyway,
-# at least they'll get the instructions to run 'configure' first.)
 all:
 
 all check install installdirs installcheck installcheck-parallel uninstall clean distclean maintainer-clean dist distcheck world check-world install-world installcheck-world:
diff --git a/configure b/configure
index 507a2437c33..67cad0f5581 100755
--- a/configure
+++ b/configure
@@ -3022,6 +3022,7 @@ else
 # --with-template not given
 
 case $host_os in
+  aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -17204,13 +17205,37 @@ _ACEOF
 # wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
 # much of a penalty for disk and memory space.
 
-MAX_ALIGNOF=$ac_cv_alignof_double
+echo "Checking for MAX ALIGN - $PORTNAME"
+if test "$PORTNAME" != "aix"; then
+    MAX_ALIGNOF=$ac_cv_alignof_double
 
-if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
-fi
-if test $ac_cv_alignof_int64_t -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'int64_t' is greater than the alignment of 'double'" "$LINENO" 5
+    if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
+      as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+    if test x"$HAVE_LONG_LONG_INT_64" = xyes && test $ac_cv_alignof_long_long_int -gt $MAX_ALIGNOF ; then
+      as_fn_error $? "alignment of 'long long int' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+else
+# The AIX 'power' alignment rules apply the natural alignment of the "first
+# member" if it is of a floating-point data type (or is an aggregate whose
+# recursively "first" member or element is such a type). The alignment
+# associated with these types for subsequent members use an alignment value
+# where the floating-point data type is considered to have 4-byte alignment.
+# More info
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99557
+#
+# The double is aligned to 4-bytes on AIX in aggregates. But to maintain
+# alignement across platforms the max alignment of long should be considered.
+      echo "MAX ALIGN ac_cv_alignof_long"
+    MAX_ALIGNOF=$ac_cv_alignof_long
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_double ; then
+      MAX_ALIGNOF=$ac_cv_alignof_double
+      echo "MAX ALIGN ac_cv_alignof_double"
+    fi
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_int64_t; then
+      MAX_ALIGNOF="$ac_cv_alignof_int64_t"
+      echo "MAX ALIGN ac_cv_alignof_int64_t"
+    fi
 fi
 
 cat >>confdefs.h <<_ACEOF
diff --git a/configure.ac b/configure.ac
index 5f4548adc5c..a25aedacef2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -62,6 +62,7 @@ PGAC_ARG_REQ(with, template, [NAME], [override operating system template],
 # --with-template not given
 
 case $host_os in
+  aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -2021,7 +2022,33 @@ AC_CHECK_ALIGNOF(double)
 # wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
 # much of a penalty for disk and memory space.
 
-MAX_ALIGNOF=$ac_cv_alignof_double
+if test "$PORTNAME" != "aix"; then
+    MAX_ALIGNOF=$ac_cv_alignof_double
+
+    if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
+      as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+    if test $ac_cv_alignof_int64_t -gt $MAX_ALIGNOF; then
+      as_fn_error $? "alignment of 'long long int' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+else
+# The AIX 'power' alignment rules apply the natural alignment of the "first
+# member" if it is of a floating-point data type (or is an aggregate whose
+# recursively "first" member or element is such a type). The alignment
+# associated with these types for subsequent members use an alignment value
+# where the floating-point data type is considered to have 4-byte alignment.
+# More info
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99557
+# 
+# The double is aligned to 4-bytes on AIX in aggregates. But to maintain
+# alignement across platforms the max alignment of long should be considered.
+    MAX_ALIGNOF=$ac_cv_alignof_long
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_double ; then
+      MAX_ALIGNOF=$ac_cv_alignof_double
+    fi
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_int64_t ; then
+      MAX_ALIGNOF="$ac_cv_alignof_int64_t"
+    fi
 
 if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
   AC_MSG_ERROR([alignment of 'long' is greater than the alignment of 'double'])
diff --git a/src/Makefile.shlib b/src/Makefile.shlib
index 3825af5b228..35adc4174ed 100644
--- a/src/Makefile.shlib
+++ b/src/Makefile.shlib
@@ -106,6 +106,20 @@ ifdef SO_MAJOR_VERSION
 override CPPFLAGS += -DSO_MAJOR_VERSION=$(SO_MAJOR_VERSION)
 endif
 
+ifeq ($(PORTNAME), aix)
+  LINK.shared		= $(COMPILER)
+  ifdef SO_MAJOR_VERSION
+    shlib		= lib$(NAME)$(DLSUFFIX).$(SO_MAJOR_VERSION)
+  endif
+  haslibarule   = yes
+  # $(exports_file) is also usable as an import file
+  exports_file		= lib$(NAME).exp
+  BUILD.exports		= ( echo '\#! $(shlib)'; $(AWK) '/^[^\#]/ {printf "%s\n",$$1}' $< ) > $@
+  ifneq (,$(SHLIB_EXPORTS))
+    LINK.shared		+= -Wl,-bE:$(exports_file)
+  endif
+endif
+
 ifeq ($(PORTNAME), darwin)
   ifdef soname
     # linkable library
@@ -254,6 +268,14 @@ $(stlib): $(OBJS) | $(SHLIB_PREREQS)
 	touch $@
 endif #haslibarule
 
+# AIX wraps both shared libraries and static library, which can be used both
+# for static and shared linking
+ifeq ($(PORTNAME), aix)
+$(stlib): $(shlib)
+	rm -f $(stlib)
+	$(AR) $(AROPT) $(stlib) $(shlib)
+endif # aix
+
 ifeq (,$(filter cygwin win32,$(PORTNAME)))
 
 # Normal case
@@ -267,8 +289,11 @@ ifneq ($(shlib), $(shlib_major))
 endif
 # Make sure we have a link to a name without any version numbers
 ifneq ($(shlib), $(shlib_bare))
+# except on AIX, where that's not a thing
+ifneq ($(PORTNAME), aix)
 	rm -f $(shlib_bare)
 	$(LN_S) $(shlib) $(shlib_bare)
+endif # aix
 endif # shlib_bare
 endif # shlib_major
 
@@ -376,6 +401,9 @@ install-lib-static: $(stlib) installdirs-lib
 
 install-lib-shared: $(shlib) installdirs-lib
 ifdef soname
+# we don't install $(shlib) on AIX
+# (see http://archives.postgresql.org/message-id/52EF20B2E3209443BC37736D00C3C1380A6E79FE@EXADV1.host.magwien.gv.at)
+ifneq ($(PORTNAME), aix)
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(libdir)/$(shlib)'
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
@@ -391,6 +419,7 @@ ifneq ($(shlib), $(shlib_bare))
 endif
 endif # not win32
 endif # not cygwin
+endif # not aix
 ifneq (,$(findstring $(PORTNAME),win32 cygwin))
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(bindir)/$(shlib)'
 endif
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 7344c8c7f5c..572f5430a60 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -63,12 +63,14 @@ all: submake-libpgport submake-catalog-headers submake-utils-headers postgres $(
 
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
+ifneq ($(PORTNAME), aix)
 
 postgres: $(OBJS)
 	$(CC) $(CFLAGS) $(call expand_subsys,$^) $(LDFLAGS) $(LIBS) -o $@
 
 endif
 endif
+endif
 
 ifeq ($(PORTNAME), cygwin)
 
@@ -95,6 +97,24 @@ libpostgres.a: postgres
 
 endif # win32
 
+ifeq ($(PORTNAME), aix)
+
+postgres: $(POSTGRES_IMP)
+	$(CC) $(CFLAGS) $(call expand_subsys,$(OBJS)) $(LDFLAGS) -Wl,-bE:$(top_builddir)/src/backend/$(POSTGRES_IMP) $(LIBS) -Wl,-brtllib -o $@
+
+# Linking to a single .o with -r is a lot faster than building a .a or passing
+# all objects to MKLDEXPORT.
+#
+# It looks alluring to use $(CC) -r instead of ld -r, but that doesn't
+# trivially work with gcc, due to gcc specific static libraries linked in with
+# -r.
+$(POSTGRES_IMP): $(OBJS)
+	ld -r -o SUBSYS.o $(call expand_subsys,$^)
+	$(MKLDEXPORT) SUBSYS.o . > $@
+	@rm -f SUBSYS.o
+
+endif # aix
+
 $(top_builddir)/src/port/libpgport_srv.a: | submake-libpgport
 
 
diff --git a/src/backend/port/aix/mkldexport.sh b/src/backend/port/aix/mkldexport.sh
new file mode 100755
index 00000000000..adf3793e868
--- /dev/null
+++ b/src/backend/port/aix/mkldexport.sh
@@ -0,0 +1,61 @@
+#!/bin/sh
+#
+# mkldexport
+#	create an AIX exports file from an object file
+#
+# src/backend/port/aix/mkldexport.sh
+#
+# Usage:
+#	mkldexport objectfile [location]
+# where
+#	objectfile is the current location of the object file.
+#	location is the eventual (installed) location of the
+#		object file (if different from the current
+#		working directory).
+#
+# [This file comes from the Postgres 4.2 distribution. - ay 7/95]
+#
+# Header: /usr/local/devel/postgres/src/tools/mkldexport/RCS/mkldexport.sh,v 1.2 1994/03/13 04:59:12 aoki Exp
+#
+
+# setting this to nm -B might be better
+# ... due to changes in AIX 4.x ...
+# ... let us search in different directories - Gerhard Reithofer
+if [ -x /usr/ucb/nm ]
+then NM=/usr/ucb/nm
+elif [ -x /usr/bin/nm ]
+then NM=/usr/bin/nm
+elif [ -x /usr/ccs/bin/nm ]
+then NM=/usr/ccs/bin/nm
+elif [ -x /usr/usg/bin/nm ]
+then NM=/usr/usg/bin/nm
+else echo "Fatal error: cannot find `nm' ... please check your installation."
+     exit 1
+fi
+
+CMDNAME=`basename $0`
+if [ -z "$1" ]; then
+	echo "Usage: $CMDNAME object [location]"
+	exit 1
+fi
+OBJNAME=`basename $1`
+if [ "`basename $OBJNAME`" != "`basename $OBJNAME .o`" ]; then
+	OBJNAME=`basename $OBJNAME .o`.so
+fi
+if [ -z "$2" ]; then
+	echo '#!'
+else
+	if [ "$2" = "." ]; then
+		# for the base executable (AIX 4.2 and up)
+		echo '#! .'
+	else
+		echo '#!' $2
+	fi
+fi
+$NM -BCg $1 | \
+	egrep ' [TDB] ' | \
+	sed -e 's/.* //' | \
+	egrep -v '\$' | \
+	sed -e 's/^[.]//' | \
+	sort | \
+	uniq
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index b7b9692f8c8..d0c4b7ba3ac 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -905,7 +905,9 @@ errcode_for_file_access(void)
 			/* Wrong object type or state */
 		case ENOTDIR:			/* Not a directory */
 		case EISDIR:			/* Is a directory */
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:			/* Directory not empty */
+#endif
 			edata->sqlerrcode = ERRCODE_WRONG_OBJECT_TYPE;
 			break;
 
diff --git a/src/include/port/aix.h b/src/include/port/aix.h
new file mode 100644
index 00000000000..7d08480c8c0
--- /dev/null
+++ b/src/include/port/aix.h
@@ -0,0 +1,4 @@
+/*
+ * src/include/port/aix.h
+ */
+
diff --git a/src/include/storage/s_lock.h b/src/include/storage/s_lock.h
index 2f73f9fcf57..ba120c08d14 100644
--- a/src/include/storage/s_lock.h
+++ b/src/include/storage/s_lock.h
@@ -398,56 +398,18 @@ typedef unsigned int slock_t;
 
 #define TAS(lock) tas(lock)
 
-/* On PPC, it's a win to use a non-locking test before the lwarx */
+/* On PPC, use the compiler provided Built-in functions for atomic memory
+ * exchange operations.
+ */
 #define TAS_SPIN(lock)	(*(lock) ? 1 : TAS(lock))
 
-/*
- * The second operand of addi can hold a constant zero or a register number,
- * hence constraint "=&b" to avoid allocating r0.  "b" stands for "address
- * base register"; most operands having this register-or-zero property are
- * address bases, e.g. the second operand of lwax.
- *
- * NOTE: per the Enhanced PowerPC Architecture manual, v1.0 dated 7-May-2002,
- * an isync is a sufficient synchronization barrier after a lwarx/stwcx loop.
- * But if the spinlock is in ordinary memory, we can use lwsync instead for
- * better performance.
- */
 static __inline__ int
 tas(volatile slock_t *lock)
 {
-	slock_t _t;
-	int _res;
-
-	__asm__ __volatile__(
-"	lwarx   %0,0,%3,1	\n"
-"	cmpwi   %0,0		\n"
-"	bne     1f			\n"
-"	addi    %0,%0,1		\n"
-"	stwcx.  %0,0,%3		\n"
-"	beq     2f			\n"
-"1: \n"
-"	li      %1,1		\n"
-"	b       3f			\n"
-"2: \n"
-"	lwsync				\n"
-"	li      %1,0		\n"
-"3: \n"
-:	"=&b"(_t), "=r"(_res), "+m"(*lock)
-:	"r"(lock)
-:	"memory", "cc");
-	return _res;
+	return __sync_lock_test_and_set(lock, 1);
 }
 
-/*
- * PowerPC S_UNLOCK is almost standard but requires a "sync" instruction.
- * But we can use lwsync instead for better performance.
- */
-#define S_UNLOCK(lock)	\
-do \
-{ \
-	__asm__ __volatile__ ("	lwsync \n" ::: "memory"); \
-	*((volatile slock_t *) (lock)) = 0; \
-} while (0)
+#define S_UNLOCK(lock) __sync_lock_release(lock)
 
 #endif /* powerpc */
 
diff --git a/src/makefiles/Makefile.aix b/src/makefiles/Makefile.aix
new file mode 100644
index 00000000000..4c4de8b0be7
--- /dev/null
+++ b/src/makefiles/Makefile.aix
@@ -0,0 +1,34 @@
+# -blibpath:
+# The path to be inserted into the default path (Index 0 path) field of the
+# loader section. When this flag is presented, the -L paths will not be stored. 
+# AIX uses a stricter, more explicit approach. The runtime linker expects to
+# tell it exactly where to look using -blibpath.
+# -blibpath must contain ALL directories where we should look for libraries
+libpath := $(shell echo $(subst -L,:,$(filter -L/%,$(LDFLAGS))) | sed -e's/ //g'):/usr/lib:/lib
+
+# AIX uses a stricter, more explicit approach. The runtime linker expects 
+# to tell it exactly where to look using -blibpath.
+rpath = -Wl,-blibpath:'$(rpathdir)$(libpath)'
+
+# gcc needs to know it's building a shared lib, otherwise it'll not emit
+# correct code / link to the right support libraries
+ifeq ($(GCC), yes)
+LDFLAGS_SL += -shared
+endif
+
+# env var name to use in place of LD_LIBRARY_PATH
+ld_library_path_var = LIBPATH
+
+POSTGRES_IMP= postgres.imp
+
+ifdef PGXS
+BE_DLLLIBS= -Wl,-bI:$(pkglibdir)/$(POSTGRES_IMP)
+else
+BE_DLLLIBS= -Wl,-bI:$(top_builddir)/src/backend/$(POSTGRES_IMP)
+endif
+
+MKLDEXPORT_DIR=src/backend/port/aix
+MKLDEXPORT=$(top_srcdir)/$(MKLDEXPORT_DIR)/mkldexport.sh
+
+%$(DLSUFFIX): %.o
+	$(CC) $(CFLAGS) $*.o $(LDFLAGS) $(LDFLAGS_SL) -o $@ $(BE_DLLLIBS)
diff --git a/src/port/strerror.c b/src/port/strerror.c
index f0746517770..c46b9dc91fc 100644
--- a/src/port/strerror.c
+++ b/src/port/strerror.c
@@ -214,8 +214,10 @@ get_errno_symbol(int errnum)
 			return "ENOTCONN";
 		case ENOTDIR:
 			return "ENOTDIR";
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:
 			return "ENOTEMPTY";
+#endif
 		case ENOTSOCK:
 			return "ENOTSOCK";
 #ifdef ENOTSUP
diff --git a/src/template/aix b/src/template/aix
new file mode 100644
index 00000000000..bfc193348f4
--- /dev/null
+++ b/src/template/aix
@@ -0,0 +1,7 @@
+# This file is referred for specific flags wrt to AIX build process like
+# cflags.
+# src/template/aix
+
+# Extra CFLAGS for code that will go into a shared library
+# With optimization, the MemSet() and MemSetAlign() perform better.
+CFLAGS_SL=" -O2 "
-- 
2.41.0

From 18dd09463342bbc836c7a8dda3a3864ceb083176 Mon Sep 17 00:00:00 2001
From: AIX-dev <postgres-ibm-aix@wwpdl.vnet.ibm.com>
Date: Wed, 15 Oct 2025 09:33:07 -0500
Subject: [PATCH] AIX changes for meson build.

---
 meson.build                                   | 25 +++++++++++--
 src/backend/jit/llvm/meson.build              |  6 ++++
 src/backend/meson.build                       | 36 ++++++++++++++++++-
 .../replication/libpqwalreceiver/meson.build  |  8 ++++-
 src/backend/replication/pgoutput/meson.build  |  6 ++++
 src/backend/snowball/meson.build              |  8 ++++-
 .../utils/mb/conversion_procs/meson.build     |  6 ++++
 src/include/port/aix.h                        | 22 ++++++++++++
 src/interfaces/ecpg/compatlib/meson.build     |  8 ++++-
 src/interfaces/ecpg/ecpglib/meson.build       |  7 +++-
 src/interfaces/ecpg/pgtypeslib/meson.build    |  7 +++-
 src/interfaces/libpq/meson.build              | 14 ++++++--
 src/tools/gen_export.pl                       | 13 +++++--
 13 files changed, 154 insertions(+), 12 deletions(-)

diff --git a/meson.build b/meson.build
index a87eb913fff..27c0f38ebc8 100644
--- a/meson.build
+++ b/meson.build
@@ -198,7 +198,26 @@ endif
 # that purpose.
 portname = host_system
 
-if host_system == 'cygwin'
+if host_system == 'aix'
+  library_path_var = 'LIBPATH'
+
+  export_file_format = 'aix'
+  export_fmt = '-Wl,-bE:@0@'
+  mod_link_args_fmt = ['-Wl,-bI:@0@']
+  mod_link_with_dir = 'libdir'
+  mod_link_with_name = '@0@.imp'
+
+  # M:SRE sets a flag indicating that an object is a shared library. Seems to
+  # work in some circumstances without, but required in others.
+  ldflags_sl += '-Wl,-bM:SRE'
+  ldflags_be += '-Wl,-brtllib'
+
+  # Native memset() is faster, tested on:
+  # - AIX 5.1 and 5.2, XLC 6.0 (IBM's cc)
+  # - AIX 5.3 ML3, gcc 4.0.1
+  #memset_loop_limit = 0
+
+elif host_system == 'cygwin'
   sema_kind = 'unnamed_posix'
   cppflags += '-D_GNU_SOURCE'
   dlsuffix = '.dll'
@@ -1775,7 +1794,9 @@ endforeach
 # would be too much of a penalty for disk and memory space.
 alignof_double = cdata.get('ALIGNOF_DOUBLE')
 if cc.alignment('int64_t', args: test_c_args, prefix: '#include <stdint.h>') > alignof_double
-  error('alignment of int64_t is greater than the alignment of double')
+  if host_system != 'aix'
+    error('alignment of int64_t is greater than the alignment of double')
+  endif
 endif
 cdata.set('MAXIMUM_ALIGNOF', alignof_double)
 
diff --git a/src/backend/jit/llvm/meson.build b/src/backend/jit/llvm/meson.build
index 805fbd69006..f83db9d0d6e 100644
--- a/src/backend/jit/llvm/meson.build
+++ b/src/backend/jit/llvm/meson.build
@@ -29,11 +29,17 @@ if host_system == 'windows'
     '--FILEDESC', 'llvmjit - JIT using LLVM',])
 endif
 
+aix_link_args= []
+if host_machine.system() == 'aix'
+  aix_link_args = ['-Wl,-bI:' + meson.project_build_root() + '/src/backend/postgres.imp']
+endif
+
 llvmjit = shared_module('llvmjit',
   llvmjit_sources,
   kwargs: pg_mod_args + {
     'dependencies': pg_mod_args['dependencies'] + [llvm],
     'cpp_args': pg_mod_args['cpp_args'] + llvm.get_variable(configtool: 'cxxflags').split(),
+    link_args: aix_link_args
   }
 )
 
diff --git a/src/backend/meson.build b/src/backend/meson.build
index b831a541652..47c0eae1309 100644
--- a/src/backend/meson.build
+++ b/src/backend/meson.build
@@ -125,6 +125,40 @@ if host_system == 'windows'
     '--FILEDESC', 'PostgreSQL Server',])
 endif
 
+if host_system == 'aix'
+find_obj_files = find_program('sh', required: true)
+
+cb_o = custom_target(
+   'SUBSYS.o',
+    input: [postgres_lib.extract_all_objects(recursive: true)],
+    output: 'SUBSYS.o',
+   command: ['ld', '-r', '-o', '@OUTPUT@', '@INPUT@'],
+   install: false,
+  )
+postgres_imp = 'postgres.imp'
+
+generate_import_file = custom_target('generate_import_file', output: postgres_imp, command: ['sh', '-c', '../src/backend/port/aix/mkldexport.sh src/backend/SUBSYS.o . > src/backend/postgres.imp'], build_by_default: true, depends: [cb_o])
+
+my_dep = declare_dependency(sources:[generate_import_file])
+#libpq_aix_deps += my_dep
+backend_link_depends += generate_import_file
+
+endif
+
+if host_system == 'aix'
+ postgres = executable('postgres',
+   backend_input,
+   sources: post_export_backend_sources,
+   objects: backend_objs,
+   link_args: backend_link_args + ['-Wl,-bE:src/backend/postgres.imp'],
+   link_with: backend_link_with,
+   link_depends: backend_link_depends,
+   export_dynamic: true,
+   implib: 'postgres',
+   dependencies: backend_build_deps + [my_dep],
+   kwargs: default_bin_args,
+)
+else
 postgres = executable('postgres',
   backend_input,
   sources: post_export_backend_sources,
@@ -137,7 +171,7 @@ postgres = executable('postgres',
   dependencies: backend_build_deps,
   kwargs: default_bin_args,
 )
-
+endif
 backend_targets += postgres
 
 pg_mod_c_args = cflags_mod
diff --git a/src/backend/replication/libpqwalreceiver/meson.build b/src/backend/replication/libpqwalreceiver/meson.build
index 2150f31cfa3..135062244d4 100644
--- a/src/backend/replication/libpqwalreceiver/meson.build
+++ b/src/backend/replication/libpqwalreceiver/meson.build
@@ -10,12 +10,18 @@ if host_system == 'windows'
     '--FILEDESC', 'libpqwalreceiver - receive WAL during streaming replication',])
 endif
 
+aix_link_args= []
+if host_machine.system() == 'aix'
+  aix_link_args = ['-Wl,-bI:' + meson.project_build_root() + '/src/backend/postgres.imp']
+endif
+
 libpqwalreceiver = shared_module('pqwalreceiver',
   libpqwalreceiver_sources,
   kwargs: pg_mod_args + {
     'name_prefix': 'lib',
     'dependencies': pg_mod_args['dependencies'] + [libpq],
-  }
+  },
+  link_args: aix_link_args
 )
 
 backend_targets += libpqwalreceiver
diff --git a/src/backend/replication/pgoutput/meson.build b/src/backend/replication/pgoutput/meson.build
index 14e2f03ada0..9fbd035988b 100644
--- a/src/backend/replication/pgoutput/meson.build
+++ b/src/backend/replication/pgoutput/meson.build
@@ -10,9 +10,15 @@ if host_system == 'windows'
     '--FILEDESC', 'pgoutput - standard logical replication output plugin',])
 endif
 
+aix_link_args= []
+if host_machine.system() == 'aix'
+  aix_link_args = ['-Wl,-bI:' + meson.project_build_root() + '/src/backend/postgres.imp']
+endif
+
 pgoutput = shared_module('pgoutput',
   pgoutput_sources,
   kwargs: pg_mod_args,
+  link_args: aix_link_args
 )
 
 backend_targets += pgoutput
diff --git a/src/backend/snowball/meson.build b/src/backend/snowball/meson.build
index 8e73d9d7368..92b3934bcc6 100644
--- a/src/backend/snowball/meson.build
+++ b/src/backend/snowball/meson.build
@@ -66,12 +66,18 @@ if host_system == 'windows'
     '--FILEDESC', 'snowball - natural language stemmers',])
 endif
 
+aix_link_args= []
+if host_machine.system() == 'aix'
+  aix_link_args = ['-Wl,-bI:' + meson.project_build_root() + '/src/backend/postgres.imp']
+endif
+
 dict_snowball = shared_module('dict_snowball',
   dict_snowball_sources,
   c_pch: pch_postgres_h,
   kwargs: pg_mod_args + {
     'include_directories': [stemmer_inc],
-  }
+  },
+  link_args: aix_link_args
 )
 
 snowball_create = custom_target('snowball_create',
diff --git a/src/backend/utils/mb/conversion_procs/meson.build b/src/backend/utils/mb/conversion_procs/meson.build
index 0e8273e0b61..a76c4993055 100644
--- a/src/backend/utils/mb/conversion_procs/meson.build
+++ b/src/backend/utils/mb/conversion_procs/meson.build
@@ -38,8 +38,14 @@ foreach encoding, sources : encodings
       '--NAME', encoding])
   endif
 
+  aix_link_args= []
+  if host_machine.system() == 'aix'
+    aix_link_args = ['-Wl,-bI:' + meson.project_build_root() + '/src/backend/postgres.imp']
+  endif
+
   backend_targets += shared_module(encoding,
     source_files,
     kwargs: pg_mod_args,
+    link_args: aix_link_args
   )
 endforeach
diff --git a/src/include/port/aix.h b/src/include/port/aix.h
index 7d08480c8c0..450e68da657 100644
--- a/src/include/port/aix.h
+++ b/src/include/port/aix.h
@@ -2,3 +2,25 @@
  * src/include/port/aix.h
  */
 
+/* These changes are required for the meson changes as the autoconf is not run
+ * and corresponding  key feature macros are defined here.
+ */
+ 
+#ifdef _AIX
+#ifndef PGDLLIMPORT
+#define PGDLLIMPORT
+#endif  /* PGDLLIMPORT */
+typedef float float4;
+typedef double float8;
+
+#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
+#define pg_noreturn _Noreturn
+#elif defined(__GNUC__)
+#define pg_noreturn __attribute__((noreturn))
+#else
+#define pg_noreturn
+#endif
+
+#include <stdbool.h>
+
+#endif  /*_AIX */
diff --git a/src/interfaces/ecpg/compatlib/meson.build b/src/interfaces/ecpg/compatlib/meson.build
index 56e0a21651b..d199002f7ed 100644
--- a/src/interfaces/ecpg/compatlib/meson.build
+++ b/src/interfaces/ecpg/compatlib/meson.build
@@ -15,8 +15,14 @@ if host_system == 'windows'
     '--FILEDESC', 'ECPG compat - compatibility library for ECPG',])
 endif
 
+libname = 'libecpg_compat'
+if host_machine.system() == 'aix'
+  libname += '_static'
+endif
+
+
 # see src/interfaces/libpq/meson.build
-ecpg_compat_st = static_library('libecpg_compat',
+ecpg_compat_st = static_library(libname,
   ecpg_compat_sources,
   include_directories: ecpg_compat_inc,
   c_args: ecpg_compat_c_args,
diff --git a/src/interfaces/ecpg/ecpglib/meson.build b/src/interfaces/ecpg/ecpglib/meson.build
index 8f478c6a73e..448a0038a71 100644
--- a/src/interfaces/ecpg/ecpglib/meson.build
+++ b/src/interfaces/ecpg/ecpglib/meson.build
@@ -24,8 +24,13 @@ if host_system == 'windows'
     '--FILEDESC', 'ECPG - embedded SQL in C',])
 endif
 
+libname = 'libecpg'
+if host_machine.system() == 'aix'
+  libname += '_static'
+endif
+
 # see src/interfaces/libpq/meson.build
-ecpglib_st = static_library('libecpg',
+ecpglib_st = static_library(libname,
   ecpglib_sources,
   include_directories: ecpglib_inc,
   c_args: ecpglib_c_args,
diff --git a/src/interfaces/ecpg/pgtypeslib/meson.build b/src/interfaces/ecpg/pgtypeslib/meson.build
index 02301ec9acb..6421930dc05 100644
--- a/src/interfaces/ecpg/pgtypeslib/meson.build
+++ b/src/interfaces/ecpg/pgtypeslib/meson.build
@@ -20,8 +20,13 @@ if host_system == 'windows'
     '--FILEDESC', 'pgtypes - library for data type mapping',])
 endif
 
+libname = 'libpgtypes'
+if host_machine.system() == 'aix'
+  libname += '_static'
+endif
+
 # see src/interfaces/libpq/meson.build
-ecpg_pgtypes_st = static_library('libpgtypes',
+ecpg_pgtypes_st = static_library(libname,
   ecpg_pgtypes_sources,
   include_directories: ecpg_pgtypes_inc,
   c_args: ecpg_pgtypes_c_args,
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index a74e885b169..3e96d3f073e 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -49,6 +49,11 @@ libpq_c_args = ['-DSO_MAJOR_VERSION=5']
 # The OAuth implementation differs depending on the type of library being built.
 libpq_so_c_args = ['-DUSE_DYNAMIC_OAUTH']
 
+libname = 'libpq'
+if host_machine.system() == 'aix'
+  libname += '_static'
+endif
+
 # Not using both_libraries() here as
 # 1) resource files should only be in the shared library
 # 2) we want the .pc file to include a dependency to {pgport,common}_static for
@@ -57,7 +62,7 @@ libpq_so_c_args = ['-DUSE_DYNAMIC_OAUTH']
 # We could try to avoid building the source files twice, but it probably adds
 # more complexity than its worth (reusing object files requires also linking
 # to the library on windows or breaks precompiled headers).
-libpq_st = static_library('libpq',
+libpq_st = static_library(libname,
   libpq_sources,
   include_directories: [libpq_inc],
   c_args: libpq_c_args,
@@ -66,6 +71,11 @@ libpq_st = static_library('libpq',
   kwargs: default_lib_args,
 )
 
+aix_link_args = []
+if host_machine.system() == 'aix'
+  aix_link_args = ['-Wl,-bI:' + export_file.full_path()]
+endif
+
 libpq_so = shared_library('libpq',
   libpq_sources + libpq_so_sources,
   include_directories: [libpq_inc, postgres_inc],
@@ -76,7 +86,7 @@ libpq_so = shared_library('libpq',
   darwin_versions: ['5', '5.' + pg_version_major.to_string()],
   dependencies: [frontend_shlib_code, libpq_deps],
   link_depends: export_file,
-  link_args: export_fmt.format(export_file.full_path()),
+  link_args: [export_fmt.format(export_file.full_path()), aix_link_args],
   kwargs: default_lib_args,
 )
 
diff --git a/src/tools/gen_export.pl b/src/tools/gen_export.pl
index 86a7742b369..19c8b60560f 100644
--- a/src/tools/gen_export.pl
+++ b/src/tools/gen_export.pl
@@ -18,9 +18,10 @@ GetOptions(
 
 if (not(   $format eq 'darwin'
 		or $format eq 'gnu'
-		or $format eq 'win'))
+		or $format eq 'win'
+        or $format eq 'aix'))
 {
-	die "$0: $format is not yet handled (only darwin, gnu, win are)\n";
+	die "$0: $format is not yet handled (only darwin, gnu, win, aix are)\n";
 }
 
 open(my $input_handle, '<', $input)
@@ -46,6 +47,10 @@ elsif ($format eq 'win')
 	}
 	print $output_handle "EXPORTS\n";
 }
+elsif ($format eq 'aix')
+{
+	print $output_handle "#!\n";
+}
 
 while (<$input_handle>)
 {
@@ -63,6 +68,10 @@ while (<$input_handle>)
 		{
 			print $output_handle "    $1;\n";
 		}
+        elsif ($format eq 'aix')
+        {
+            print $output_handle "$1\n";
+        }
 		elsif ($format eq 'win')
 		{
 			print $output_handle "$1 @ $2\n";
-- 
2.41.0

From 407b42b1fbe562dff69820f7456dbb32a8a37d79 Mon Sep 17 00:00:00 2001
From: AIX-dev <postgres-ibm-aix@wwpdl.vnet.ibm.com>
Date: Tue, 16 Sep 2025 08:59:22 -0500
Subject: [PATCH] Changes to add support for AIX.

---
 Makefile                           |  2 -
 configure                          | 37 +++++++++++++++---
 configure.ac                       | 29 +++++++++++++-
 src/Makefile.shlib                 | 29 ++++++++++++++
 src/backend/Makefile               | 20 ++++++++++
 src/backend/port/aix/mkldexport.sh | 61 ++++++++++++++++++++++++++++++
 src/backend/utils/error/elog.c     |  2 +
 src/include/port/aix.h             |  4 ++
 src/include/storage/s_lock.h       | 48 +++--------------------
 src/makefiles/Makefile.aix         | 34 +++++++++++++++++
 src/port/strerror.c                |  2 +
 src/template/aix                   |  7 ++++
 12 files changed, 223 insertions(+), 52 deletions(-)
 create mode 100755 src/backend/port/aix/mkldexport.sh
 create mode 100644 src/include/port/aix.h
 create mode 100644 src/makefiles/Makefile.aix
 create mode 100644 src/template/aix

diff --git a/Makefile b/Makefile
index 8a2ec9396b6..9bc1a4ec17b 100644
--- a/Makefile
+++ b/Makefile
@@ -13,8 +13,6 @@
 
 # AIX make defaults to building *every* target of the first rule.  Start with
 # a single-target, empty rule to make the other targets non-default.
-# (We don't support AIX anymore, but if someone tries to build on AIX anyway,
-# at least they'll get the instructions to run 'configure' first.)
 all:
 
 all check install installdirs installcheck installcheck-parallel uninstall clean distclean maintainer-clean dist distcheck world check-world install-world installcheck-world:
diff --git a/configure b/configure
index 507a2437c33..67cad0f5581 100755
--- a/configure
+++ b/configure
@@ -3022,6 +3022,7 @@ else
 # --with-template not given
 
 case $host_os in
+  aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -17204,13 +17205,37 @@ _ACEOF
 # wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
 # much of a penalty for disk and memory space.
 
-MAX_ALIGNOF=$ac_cv_alignof_double
+echo "Checking for MAX ALIGN - $PORTNAME"
+if test "$PORTNAME" != "aix"; then
+    MAX_ALIGNOF=$ac_cv_alignof_double
 
-if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
-fi
-if test $ac_cv_alignof_int64_t -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'int64_t' is greater than the alignment of 'double'" "$LINENO" 5
+    if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
+      as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+    if test x"$HAVE_LONG_LONG_INT_64" = xyes && test $ac_cv_alignof_long_long_int -gt $MAX_ALIGNOF ; then
+      as_fn_error $? "alignment of 'long long int' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+else
+# The AIX 'power' alignment rules apply the natural alignment of the "first
+# member" if it is of a floating-point data type (or is an aggregate whose
+# recursively "first" member or element is such a type). The alignment
+# associated with these types for subsequent members use an alignment value
+# where the floating-point data type is considered to have 4-byte alignment.
+# More info
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99557
+#
+# The double is aligned to 4-bytes on AIX in aggregates. But to maintain
+# alignement across platforms the max alignment of long should be considered.
+      echo "MAX ALIGN ac_cv_alignof_long"
+    MAX_ALIGNOF=$ac_cv_alignof_long
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_double ; then
+      MAX_ALIGNOF=$ac_cv_alignof_double
+      echo "MAX ALIGN ac_cv_alignof_double"
+    fi
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_int64_t; then
+      MAX_ALIGNOF="$ac_cv_alignof_int64_t"
+      echo "MAX ALIGN ac_cv_alignof_int64_t"
+    fi
 fi
 
 cat >>confdefs.h <<_ACEOF
diff --git a/configure.ac b/configure.ac
index 5f4548adc5c..a25aedacef2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -62,6 +62,7 @@ PGAC_ARG_REQ(with, template, [NAME], [override operating system template],
 # --with-template not given
 
 case $host_os in
+  aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -2021,7 +2022,33 @@ AC_CHECK_ALIGNOF(double)
 # wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
 # much of a penalty for disk and memory space.
 
-MAX_ALIGNOF=$ac_cv_alignof_double
+if test "$PORTNAME" != "aix"; then
+    MAX_ALIGNOF=$ac_cv_alignof_double
+
+    if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
+      as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+    if test $ac_cv_alignof_int64_t -gt $MAX_ALIGNOF; then
+      as_fn_error $? "alignment of 'long long int' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+else
+# The AIX 'power' alignment rules apply the natural alignment of the "first
+# member" if it is of a floating-point data type (or is an aggregate whose
+# recursively "first" member or element is such a type). The alignment
+# associated with these types for subsequent members use an alignment value
+# where the floating-point data type is considered to have 4-byte alignment.
+# More info
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99557
+# 
+# The double is aligned to 4-bytes on AIX in aggregates. But to maintain
+# alignement across platforms the max alignment of long should be considered.
+    MAX_ALIGNOF=$ac_cv_alignof_long
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_double ; then
+      MAX_ALIGNOF=$ac_cv_alignof_double
+    fi
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_int64_t ; then
+      MAX_ALIGNOF="$ac_cv_alignof_int64_t"
+    fi
 
 if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
   AC_MSG_ERROR([alignment of 'long' is greater than the alignment of 'double'])
diff --git a/src/Makefile.shlib b/src/Makefile.shlib
index 3825af5b228..35adc4174ed 100644
--- a/src/Makefile.shlib
+++ b/src/Makefile.shlib
@@ -106,6 +106,20 @@ ifdef SO_MAJOR_VERSION
 override CPPFLAGS += -DSO_MAJOR_VERSION=$(SO_MAJOR_VERSION)
 endif
 
+ifeq ($(PORTNAME), aix)
+  LINK.shared		= $(COMPILER)
+  ifdef SO_MAJOR_VERSION
+    shlib		= lib$(NAME)$(DLSUFFIX).$(SO_MAJOR_VERSION)
+  endif
+  haslibarule   = yes
+  # $(exports_file) is also usable as an import file
+  exports_file		= lib$(NAME).exp
+  BUILD.exports		= ( echo '\#! $(shlib)'; $(AWK) '/^[^\#]/ {printf "%s\n",$$1}' $< ) > $@
+  ifneq (,$(SHLIB_EXPORTS))
+    LINK.shared		+= -Wl,-bE:$(exports_file)
+  endif
+endif
+
 ifeq ($(PORTNAME), darwin)
   ifdef soname
     # linkable library
@@ -254,6 +268,14 @@ $(stlib): $(OBJS) | $(SHLIB_PREREQS)
 	touch $@
 endif #haslibarule
 
+# AIX wraps both shared libraries and static library, which can be used both
+# for static and shared linking
+ifeq ($(PORTNAME), aix)
+$(stlib): $(shlib)
+	rm -f $(stlib)
+	$(AR) $(AROPT) $(stlib) $(shlib)
+endif # aix
+
 ifeq (,$(filter cygwin win32,$(PORTNAME)))
 
 # Normal case
@@ -267,8 +289,11 @@ ifneq ($(shlib), $(shlib_major))
 endif
 # Make sure we have a link to a name without any version numbers
 ifneq ($(shlib), $(shlib_bare))
+# except on AIX, where that's not a thing
+ifneq ($(PORTNAME), aix)
 	rm -f $(shlib_bare)
 	$(LN_S) $(shlib) $(shlib_bare)
+endif # aix
 endif # shlib_bare
 endif # shlib_major
 
@@ -376,6 +401,9 @@ install-lib-static: $(stlib) installdirs-lib
 
 install-lib-shared: $(shlib) installdirs-lib
 ifdef soname
+# we don't install $(shlib) on AIX
+# (see http://archives.postgresql.org/message-id/52EF20B2E3209443BC37736D00C3C1380A6E79FE@EXADV1.host.magwien.gv.at)
+ifneq ($(PORTNAME), aix)
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(libdir)/$(shlib)'
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
@@ -391,6 +419,7 @@ ifneq ($(shlib), $(shlib_bare))
 endif
 endif # not win32
 endif # not cygwin
+endif # not aix
 ifneq (,$(findstring $(PORTNAME),win32 cygwin))
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(bindir)/$(shlib)'
 endif
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 7344c8c7f5c..572f5430a60 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -63,12 +63,14 @@ all: submake-libpgport submake-catalog-headers submake-utils-headers postgres $(
 
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
+ifneq ($(PORTNAME), aix)
 
 postgres: $(OBJS)
 	$(CC) $(CFLAGS) $(call expand_subsys,$^) $(LDFLAGS) $(LIBS) -o $@
 
 endif
 endif
+endif
 
 ifeq ($(PORTNAME), cygwin)
 
@@ -95,6 +97,24 @@ libpostgres.a: postgres
 
 endif # win32
 
+ifeq ($(PORTNAME), aix)
+
+postgres: $(POSTGRES_IMP)
+	$(CC) $(CFLAGS) $(call expand_subsys,$(OBJS)) $(LDFLAGS) -Wl,-bE:$(top_builddir)/src/backend/$(POSTGRES_IMP) $(LIBS) -Wl,-brtllib -o $@
+
+# Linking to a single .o with -r is a lot faster than building a .a or passing
+# all objects to MKLDEXPORT.
+#
+# It looks alluring to use $(CC) -r instead of ld -r, but that doesn't
+# trivially work with gcc, due to gcc specific static libraries linked in with
+# -r.
+$(POSTGRES_IMP): $(OBJS)
+	ld -r -o SUBSYS.o $(call expand_subsys,$^)
+	$(MKLDEXPORT) SUBSYS.o . > $@
+	@rm -f SUBSYS.o
+
+endif # aix
+
 $(top_builddir)/src/port/libpgport_srv.a: | submake-libpgport
 
 
diff --git a/src/backend/port/aix/mkldexport.sh b/src/backend/port/aix/mkldexport.sh
new file mode 100755
index 00000000000..adf3793e868
--- /dev/null
+++ b/src/backend/port/aix/mkldexport.sh
@@ -0,0 +1,61 @@
+#!/bin/sh
+#
+# mkldexport
+#	create an AIX exports file from an object file
+#
+# src/backend/port/aix/mkldexport.sh
+#
+# Usage:
+#	mkldexport objectfile [location]
+# where
+#	objectfile is the current location of the object file.
+#	location is the eventual (installed) location of the
+#		object file (if different from the current
+#		working directory).
+#
+# [This file comes from the Postgres 4.2 distribution. - ay 7/95]
+#
+# Header: /usr/local/devel/postgres/src/tools/mkldexport/RCS/mkldexport.sh,v 1.2 1994/03/13 04:59:12 aoki Exp
+#
+
+# setting this to nm -B might be better
+# ... due to changes in AIX 4.x ...
+# ... let us search in different directories - Gerhard Reithofer
+if [ -x /usr/ucb/nm ]
+then NM=/usr/ucb/nm
+elif [ -x /usr/bin/nm ]
+then NM=/usr/bin/nm
+elif [ -x /usr/ccs/bin/nm ]
+then NM=/usr/ccs/bin/nm
+elif [ -x /usr/usg/bin/nm ]
+then NM=/usr/usg/bin/nm
+else echo "Fatal error: cannot find `nm' ... please check your installation."
+     exit 1
+fi
+
+CMDNAME=`basename $0`
+if [ -z "$1" ]; then
+	echo "Usage: $CMDNAME object [location]"
+	exit 1
+fi
+OBJNAME=`basename $1`
+if [ "`basename $OBJNAME`" != "`basename $OBJNAME .o`" ]; then
+	OBJNAME=`basename $OBJNAME .o`.so
+fi
+if [ -z "$2" ]; then
+	echo '#!'
+else
+	if [ "$2" = "." ]; then
+		# for the base executable (AIX 4.2 and up)
+		echo '#! .'
+	else
+		echo '#!' $2
+	fi
+fi
+$NM -BCg $1 | \
+	egrep ' [TDB] ' | \
+	sed -e 's/.* //' | \
+	egrep -v '\$' | \
+	sed -e 's/^[.]//' | \
+	sort | \
+	uniq
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index b7b9692f8c8..d0c4b7ba3ac 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -905,7 +905,9 @@ errcode_for_file_access(void)
 			/* Wrong object type or state */
 		case ENOTDIR:			/* Not a directory */
 		case EISDIR:			/* Is a directory */
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:			/* Directory not empty */
+#endif
 			edata->sqlerrcode = ERRCODE_WRONG_OBJECT_TYPE;
 			break;
 
diff --git a/src/include/port/aix.h b/src/include/port/aix.h
new file mode 100644
index 00000000000..7d08480c8c0
--- /dev/null
+++ b/src/include/port/aix.h
@@ -0,0 +1,4 @@
+/*
+ * src/include/port/aix.h
+ */
+
diff --git a/src/include/storage/s_lock.h b/src/include/storage/s_lock.h
index 2f73f9fcf57..ba120c08d14 100644
--- a/src/include/storage/s_lock.h
+++ b/src/include/storage/s_lock.h
@@ -398,56 +398,18 @@ typedef unsigned int slock_t;
 
 #define TAS(lock) tas(lock)
 
-/* On PPC, it's a win to use a non-locking test before the lwarx */
+/* On PPC, use the compiler provided Built-in functions for atomic memory
+ * exchange operations.
+ */
 #define TAS_SPIN(lock)	(*(lock) ? 1 : TAS(lock))
 
-/*
- * The second operand of addi can hold a constant zero or a register number,
- * hence constraint "=&b" to avoid allocating r0.  "b" stands for "address
- * base register"; most operands having this register-or-zero property are
- * address bases, e.g. the second operand of lwax.
- *
- * NOTE: per the Enhanced PowerPC Architecture manual, v1.0 dated 7-May-2002,
- * an isync is a sufficient synchronization barrier after a lwarx/stwcx loop.
- * But if the spinlock is in ordinary memory, we can use lwsync instead for
- * better performance.
- */
 static __inline__ int
 tas(volatile slock_t *lock)
 {
-	slock_t _t;
-	int _res;
-
-	__asm__ __volatile__(
-"	lwarx   %0,0,%3,1	\n"
-"	cmpwi   %0,0		\n"
-"	bne     1f			\n"
-"	addi    %0,%0,1		\n"
-"	stwcx.  %0,0,%3		\n"
-"	beq     2f			\n"
-"1: \n"
-"	li      %1,1		\n"
-"	b       3f			\n"
-"2: \n"
-"	lwsync				\n"
-"	li      %1,0		\n"
-"3: \n"
-:	"=&b"(_t), "=r"(_res), "+m"(*lock)
-:	"r"(lock)
-:	"memory", "cc");
-	return _res;
+	return __sync_lock_test_and_set(lock, 1);
 }
 
-/*
- * PowerPC S_UNLOCK is almost standard but requires a "sync" instruction.
- * But we can use lwsync instead for better performance.
- */
-#define S_UNLOCK(lock)	\
-do \
-{ \
-	__asm__ __volatile__ ("	lwsync \n" ::: "memory"); \
-	*((volatile slock_t *) (lock)) = 0; \
-} while (0)
+#define S_UNLOCK(lock) __sync_lock_release(lock)
 
 #endif /* powerpc */
 
diff --git a/src/makefiles/Makefile.aix b/src/makefiles/Makefile.aix
new file mode 100644
index 00000000000..4c4de8b0be7
--- /dev/null
+++ b/src/makefiles/Makefile.aix
@@ -0,0 +1,34 @@
+# -blibpath:
+# The path to be inserted into the default path (Index 0 path) field of the
+# loader section. When this flag is presented, the -L paths will not be stored. 
+# AIX uses a stricter, more explicit approach. The runtime linker expects to
+# tell it exactly where to look using -blibpath.
+# -blibpath must contain ALL directories where we should look for libraries
+libpath := $(shell echo $(subst -L,:,$(filter -L/%,$(LDFLAGS))) | sed -e's/ //g'):/usr/lib:/lib
+
+# AIX uses a stricter, more explicit approach. The runtime linker expects 
+# to tell it exactly where to look using -blibpath.
+rpath = -Wl,-blibpath:'$(rpathdir)$(libpath)'
+
+# gcc needs to know it's building a shared lib, otherwise it'll not emit
+# correct code / link to the right support libraries
+ifeq ($(GCC), yes)
+LDFLAGS_SL += -shared
+endif
+
+# env var name to use in place of LD_LIBRARY_PATH
+ld_library_path_var = LIBPATH
+
+POSTGRES_IMP= postgres.imp
+
+ifdef PGXS
+BE_DLLLIBS= -Wl,-bI:$(pkglibdir)/$(POSTGRES_IMP)
+else
+BE_DLLLIBS= -Wl,-bI:$(top_builddir)/src/backend/$(POSTGRES_IMP)
+endif
+
+MKLDEXPORT_DIR=src/backend/port/aix
+MKLDEXPORT=$(top_srcdir)/$(MKLDEXPORT_DIR)/mkldexport.sh
+
+%$(DLSUFFIX): %.o
+	$(CC) $(CFLAGS) $*.o $(LDFLAGS) $(LDFLAGS_SL) -o $@ $(BE_DLLLIBS)
diff --git a/src/port/strerror.c b/src/port/strerror.c
index f0746517770..c46b9dc91fc 100644
--- a/src/port/strerror.c
+++ b/src/port/strerror.c
@@ -214,8 +214,10 @@ get_errno_symbol(int errnum)
 			return "ENOTCONN";
 		case ENOTDIR:
 			return "ENOTDIR";
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:
 			return "ENOTEMPTY";
+#endif
 		case ENOTSOCK:
 			return "ENOTSOCK";
 #ifdef ENOTSUP
diff --git a/src/template/aix b/src/template/aix
new file mode 100644
index 00000000000..bfc193348f4
--- /dev/null
+++ b/src/template/aix
@@ -0,0 +1,7 @@
+# This file is referred for specific flags wrt to AIX build process like
+# cflags.
+# src/template/aix
+
+# Extra CFLAGS for code that will go into a shared library
+# With optimization, the MemSet() and MemSetAlign() perform better.
+CFLAGS_SL=" -O2 "
-- 
2.41.0

From 98af27c6331c4fe161f7cab5c16768587f7fcb9a Mon Sep 17 00:00:00 2001
From: AIX-dev <postgres-ibm-aix@wwpdl.vnet.ibm.com>
Date: Tue, 9 Dec 2025 09:49:31 -0600
Subject: [PATCH] Support for AIX.

---
 Makefile                                   |  2 -
 configure                                  | 37 ++++++++++---
 configure.ac                               | 29 +++++++++-
 meson.build                                | 27 ++++++++--
 src/Makefile.shlib                         | 29 ++++++++++
 src/backend/Makefile                       | 20 +++++++
 src/backend/meson.build                    | 18 +++++++
 src/backend/port/aix/mkldexport.sh         | 61 ++++++++++++++++++++++
 src/backend/utils/error/elog.c             |  2 +
 src/include/port/aix.h                     | 26 +++++++++
 src/include/storage/s_lock.h               | 52 +++---------------
 src/interfaces/ecpg/compatlib/meson.build  |  2 +-
 src/interfaces/ecpg/ecpglib/meson.build    |  2 +-
 src/interfaces/ecpg/pgtypeslib/meson.build |  2 +-
 src/interfaces/libpq/meson.build           |  2 +-
 src/makefiles/Makefile.aix                 | 34 ++++++++++++
 src/port/strerror.c                        |  2 +
 src/template/aix                           |  6 +++
 src/tools/gen_export.pl                    | 11 +++-
 19 files changed, 300 insertions(+), 64 deletions(-)
 create mode 100755 src/backend/port/aix/mkldexport.sh
 create mode 100644 src/include/port/aix.h
 create mode 100644 src/makefiles/Makefile.aix
 create mode 100644 src/template/aix

diff --git a/Makefile b/Makefile
index 8a2ec9396b6..9bc1a4ec17b 100644
--- a/Makefile
+++ b/Makefile
@@ -13,8 +13,6 @@
 
 # AIX make defaults to building *every* target of the first rule.  Start with
 # a single-target, empty rule to make the other targets non-default.
-# (We don't support AIX anymore, but if someone tries to build on AIX anyway,
-# at least they'll get the instructions to run 'configure' first.)
 all:
 
 all check install installdirs installcheck installcheck-parallel uninstall clean distclean maintainer-clean dist distcheck world check-world install-world installcheck-world:
diff --git a/configure b/configure
index 3a0ed11fa8e..c4749a8e5b6 100755
--- a/configure
+++ b/configure
@@ -3020,6 +3020,7 @@ else
 # --with-template not given
 
 case $host_os in
+  aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -17006,13 +17007,37 @@ _ACEOF
 # wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
 # much of a penalty for disk and memory space.
 
-MAX_ALIGNOF=$ac_cv_alignof_double
+echo "Checking for MAX ALIGN - $PORTNAME"
+if test "$PORTNAME" != "aix"; then
+    MAX_ALIGNOF=$ac_cv_alignof_double
 
-if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
-fi
-if test $ac_cv_alignof_int64_t -gt $MAX_ALIGNOF ; then
-  as_fn_error $? "alignment of 'int64_t' is greater than the alignment of 'double'" "$LINENO" 5
+    if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
+      as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+    if test x"$HAVE_LONG_LONG_INT_64" = xyes && test $ac_cv_alignof_long_long_int -gt $MAX_ALIGNOF ; then
+      as_fn_error $? "alignment of 'long long int' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+else
+# The AIX 'power' alignment rules apply the natural alignment of the "first
+# member" if it is of a floating-point data type (or is an aggregate whose
+# recursively "first" member or element is such a type). The alignment
+# associated with these types for subsequent members use an alignment value
+# where the floating-point data type is considered to have 4-byte alignment.
+# More info
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99557
+#
+# The double is aligned to 4-bytes on AIX in aggregates. But to maintain
+# alignement across platforms the max alignment of long should be considered.
+      echo "MAX ALIGN ac_cv_alignof_long"
+    MAX_ALIGNOF=$ac_cv_alignof_long
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_double ; then
+      MAX_ALIGNOF=$ac_cv_alignof_double
+      echo "MAX ALIGN ac_cv_alignof_double"
+    fi
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_int64_t; then
+      MAX_ALIGNOF="$ac_cv_alignof_int64_t"
+      echo "MAX ALIGN ac_cv_alignof_int64_t"
+    fi
 fi
 
 cat >>confdefs.h <<_ACEOF
diff --git a/configure.ac b/configure.ac
index c2413720a18..7f1530df2b1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -62,6 +62,7 @@ PGAC_ARG_REQ(with, template, [NAME], [override operating system template],
 # --with-template not given
 
 case $host_os in
+  aix*) template=aix ;;
   cygwin*|msys*) template=cygwin ;;
   darwin*) template=darwin ;;
 dragonfly*) template=netbsd ;;
@@ -2006,7 +2007,33 @@ AC_CHECK_ALIGNOF(double)
 # wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8 would be too
 # much of a penalty for disk and memory space.
 
-MAX_ALIGNOF=$ac_cv_alignof_double
+if test "$PORTNAME" != "aix"; then
+    MAX_ALIGNOF=$ac_cv_alignof_double
+
+    if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
+      as_fn_error $? "alignment of 'long' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+    if test $ac_cv_alignof_int64_t -gt $MAX_ALIGNOF; then
+      as_fn_error $? "alignment of 'long long int' is greater than the alignment of 'double'" "$LINENO" 5
+    fi
+else
+# The AIX 'power' alignment rules apply the natural alignment of the "first
+# member" if it is of a floating-point data type (or is an aggregate whose
+# recursively "first" member or element is such a type). The alignment
+# associated with these types for subsequent members use an alignment value
+# where the floating-point data type is considered to have 4-byte alignment.
+# More info
+# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99557
+# 
+# The double is aligned to 4-bytes on AIX in aggregates. But to maintain
+# alignement across platforms the max alignment of long should be considered.
+    MAX_ALIGNOF=$ac_cv_alignof_long
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_double ; then
+      MAX_ALIGNOF=$ac_cv_alignof_double
+    fi
+    if test $MAX_ALIGNOF -lt $ac_cv_alignof_int64_t ; then
+      MAX_ALIGNOF="$ac_cv_alignof_int64_t"
+    fi
 
 if test $ac_cv_alignof_long -gt $MAX_ALIGNOF ; then
   AC_MSG_ERROR([alignment of 'long' is greater than the alignment of 'double'])
diff --git a/meson.build b/meson.build
index 6e7ddd74683..304a9184075 100644
--- a/meson.build
+++ b/meson.build
@@ -206,6 +206,25 @@ if host_system == 'cygwin'
   mod_link_with_name = 'lib@0@.a'
   mod_link_with_dir = 'libdir'
 
+elif host_system == 'aix'
+  sema_kind = 'unnamed_posix'
+  library_path_var = 'LIBPATH'
+  export_file_format = 'aix'
+  export_fmt = '-Wl,-bE:@0@'
+  mod_link_args_fmt = ['-Wl,-bI:@0@']
+  mod_link_with_dir = 'libdir'
+  mod_link_with_name = '@0@.imp'
+  dl_suffix = '.a'
+  cppflags += '-D_GNU_SOURCE'
+
+  # M:SRE sets a flag indicating that an object is a shared library. Seems to
+  # work in some circumstances without, but required in others.
+  ldflags_sl += '-Wl,-bM:SRE'
+  ldflags_be += '-Wl,-brtllib'
+
+  # Native memset() is faster, tested on:
+  memset_loop_limit = 0
+
 elif host_system == 'darwin'
   dlsuffix = '.dylib'
   library_path_var = 'DYLD_LIBRARY_PATH'
@@ -1766,9 +1785,9 @@ endforeach
 # any types wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8
 # would be too much of a penalty for disk and memory space.
 alignof_double = cdata.get('ALIGNOF_DOUBLE')
-if cc.alignment('int64_t', args: test_c_args, prefix: '#include <stdint.h>') > alignof_double
-  error('alignment of int64_t is greater than the alignment of double')
-endif
+#if cc.alignment('int64_t', args: test_c_args, prefix: '#include <stdint.h>') > alignof_double
+#  error('alignment of int64_t is greater than the alignment of double')
+#endif
 cdata.set('MAXIMUM_ALIGNOF', alignof_double)
 
 cdata.set('SIZEOF_LONG', cc.sizeof('long', args: test_c_args))
@@ -1820,7 +1839,7 @@ if cc.links('''
   if not meson.is_cross_build()
     r = cc.run('''
     /* This must match the corresponding code in c.h: */
-    #if defined(__GNUC__)
+    #if defined(__GNUC__) || defined(__IBMC__)
     #define pg_attribute_aligned(a) __attribute__((aligned(a)))
     #elif defined(_MSC_VER)
     #define pg_attribute_aligned(a) __declspec(align(a))
diff --git a/src/Makefile.shlib b/src/Makefile.shlib
index 3825af5b228..35adc4174ed 100644
--- a/src/Makefile.shlib
+++ b/src/Makefile.shlib
@@ -106,6 +106,20 @@ ifdef SO_MAJOR_VERSION
 override CPPFLAGS += -DSO_MAJOR_VERSION=$(SO_MAJOR_VERSION)
 endif
 
+ifeq ($(PORTNAME), aix)
+  LINK.shared		= $(COMPILER)
+  ifdef SO_MAJOR_VERSION
+    shlib		= lib$(NAME)$(DLSUFFIX).$(SO_MAJOR_VERSION)
+  endif
+  haslibarule   = yes
+  # $(exports_file) is also usable as an import file
+  exports_file		= lib$(NAME).exp
+  BUILD.exports		= ( echo '\#! $(shlib)'; $(AWK) '/^[^\#]/ {printf "%s\n",$$1}' $< ) > $@
+  ifneq (,$(SHLIB_EXPORTS))
+    LINK.shared		+= -Wl,-bE:$(exports_file)
+  endif
+endif
+
 ifeq ($(PORTNAME), darwin)
   ifdef soname
     # linkable library
@@ -254,6 +268,14 @@ $(stlib): $(OBJS) | $(SHLIB_PREREQS)
 	touch $@
 endif #haslibarule
 
+# AIX wraps both shared libraries and static library, which can be used both
+# for static and shared linking
+ifeq ($(PORTNAME), aix)
+$(stlib): $(shlib)
+	rm -f $(stlib)
+	$(AR) $(AROPT) $(stlib) $(shlib)
+endif # aix
+
 ifeq (,$(filter cygwin win32,$(PORTNAME)))
 
 # Normal case
@@ -267,8 +289,11 @@ ifneq ($(shlib), $(shlib_major))
 endif
 # Make sure we have a link to a name without any version numbers
 ifneq ($(shlib), $(shlib_bare))
+# except on AIX, where that's not a thing
+ifneq ($(PORTNAME), aix)
 	rm -f $(shlib_bare)
 	$(LN_S) $(shlib) $(shlib_bare)
+endif # aix
 endif # shlib_bare
 endif # shlib_major
 
@@ -376,6 +401,9 @@ install-lib-static: $(stlib) installdirs-lib
 
 install-lib-shared: $(shlib) installdirs-lib
 ifdef soname
+# we don't install $(shlib) on AIX
+# (see http://archives.postgresql.org/message-id/52EF20B2E3209443BC37736D00C3C1380A6E79FE@EXADV1.host.magwien.gv.at)
+ifneq ($(PORTNAME), aix)
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(libdir)/$(shlib)'
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
@@ -391,6 +419,7 @@ ifneq ($(shlib), $(shlib_bare))
 endif
 endif # not win32
 endif # not cygwin
+endif # not aix
 ifneq (,$(findstring $(PORTNAME),win32 cygwin))
 	$(INSTALL_SHLIB) $< '$(DESTDIR)$(bindir)/$(shlib)'
 endif
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 7344c8c7f5c..572f5430a60 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -63,12 +63,14 @@ all: submake-libpgport submake-catalog-headers submake-utils-headers postgres $(
 
 ifneq ($(PORTNAME), cygwin)
 ifneq ($(PORTNAME), win32)
+ifneq ($(PORTNAME), aix)
 
 postgres: $(OBJS)
 	$(CC) $(CFLAGS) $(call expand_subsys,$^) $(LDFLAGS) $(LIBS) -o $@
 
 endif
 endif
+endif
 
 ifeq ($(PORTNAME), cygwin)
 
@@ -95,6 +97,24 @@ libpostgres.a: postgres
 
 endif # win32
 
+ifeq ($(PORTNAME), aix)
+
+postgres: $(POSTGRES_IMP)
+	$(CC) $(CFLAGS) $(call expand_subsys,$(OBJS)) $(LDFLAGS) -Wl,-bE:$(top_builddir)/src/backend/$(POSTGRES_IMP) $(LIBS) -Wl,-brtllib -o $@
+
+# Linking to a single .o with -r is a lot faster than building a .a or passing
+# all objects to MKLDEXPORT.
+#
+# It looks alluring to use $(CC) -r instead of ld -r, but that doesn't
+# trivially work with gcc, due to gcc specific static libraries linked in with
+# -r.
+$(POSTGRES_IMP): $(OBJS)
+	ld -r -o SUBSYS.o $(call expand_subsys,$^)
+	$(MKLDEXPORT) SUBSYS.o . > $@
+	@rm -f SUBSYS.o
+
+endif # aix
+
 $(top_builddir)/src/port/libpgport_srv.a: | submake-libpgport
 
 
diff --git a/src/backend/meson.build b/src/backend/meson.build
index b831a541652..4838f245ab3 100644
--- a/src/backend/meson.build
+++ b/src/backend/meson.build
@@ -125,6 +125,24 @@ if host_system == 'windows'
     '--FILEDESC', 'PostgreSQL Server',])
 endif
 
+if host_system == 'aix'
+  # The '.' argument leads mkldexport.sh to emit "#! .", which refers to the
+  # main executable, allowing extension libraries to resolve their undefined
+  # symbols to symbols in the postgres binary.
+  postgres_imp = custom_target('postgres.imp',
+    command: [files('port/aix/mkldexport.sh'), '@INPUT@', '.'],
+    input: postgres_lib,
+    output: 'postgres.imp',
+    capture: true,
+    install: true,
+    install_dir: dir_lib,
+    build_by_default: false,
+  )
+  backend_link_args += '-Wl,-bE:@0@'.format(postgres_imp.full_path())
+  backend_link_depends += postgres_imp
+endif
+
+
 postgres = executable('postgres',
   backend_input,
   sources: post_export_backend_sources,
diff --git a/src/backend/port/aix/mkldexport.sh b/src/backend/port/aix/mkldexport.sh
new file mode 100755
index 00000000000..adf3793e868
--- /dev/null
+++ b/src/backend/port/aix/mkldexport.sh
@@ -0,0 +1,61 @@
+#!/bin/sh
+#
+# mkldexport
+#	create an AIX exports file from an object file
+#
+# src/backend/port/aix/mkldexport.sh
+#
+# Usage:
+#	mkldexport objectfile [location]
+# where
+#	objectfile is the current location of the object file.
+#	location is the eventual (installed) location of the
+#		object file (if different from the current
+#		working directory).
+#
+# [This file comes from the Postgres 4.2 distribution. - ay 7/95]
+#
+# Header: /usr/local/devel/postgres/src/tools/mkldexport/RCS/mkldexport.sh,v 1.2 1994/03/13 04:59:12 aoki Exp
+#
+
+# setting this to nm -B might be better
+# ... due to changes in AIX 4.x ...
+# ... let us search in different directories - Gerhard Reithofer
+if [ -x /usr/ucb/nm ]
+then NM=/usr/ucb/nm
+elif [ -x /usr/bin/nm ]
+then NM=/usr/bin/nm
+elif [ -x /usr/ccs/bin/nm ]
+then NM=/usr/ccs/bin/nm
+elif [ -x /usr/usg/bin/nm ]
+then NM=/usr/usg/bin/nm
+else echo "Fatal error: cannot find `nm' ... please check your installation."
+     exit 1
+fi
+
+CMDNAME=`basename $0`
+if [ -z "$1" ]; then
+	echo "Usage: $CMDNAME object [location]"
+	exit 1
+fi
+OBJNAME=`basename $1`
+if [ "`basename $OBJNAME`" != "`basename $OBJNAME .o`" ]; then
+	OBJNAME=`basename $OBJNAME .o`.so
+fi
+if [ -z "$2" ]; then
+	echo '#!'
+else
+	if [ "$2" = "." ]; then
+		# for the base executable (AIX 4.2 and up)
+		echo '#! .'
+	else
+		echo '#!' $2
+	fi
+fi
+$NM -BCg $1 | \
+	egrep ' [TDB] ' | \
+	sed -e 's/.* //' | \
+	egrep -v '\$' | \
+	sed -e 's/^[.]//' | \
+	sort | \
+	uniq
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 29643c51439..1c933b5afad 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -914,7 +914,9 @@ errcode_for_file_access(void)
 			/* Wrong object type or state */
 		case ENOTDIR:			/* Not a directory */
 		case EISDIR:			/* Is a directory */
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:			/* Directory not empty */
+#endif
 			edata->sqlerrcode = ERRCODE_WRONG_OBJECT_TYPE;
 			break;
 
diff --git a/src/include/port/aix.h b/src/include/port/aix.h
new file mode 100644
index 00000000000..dd7cfb197cd
--- /dev/null
+++ b/src/include/port/aix.h
@@ -0,0 +1,26 @@
+/*
+ * src/include/port/aix.h
+ */
+
+/* This change is required for the meson changes as the autoconf is not run and
+ * to resolve the conflicts in picking the float.h details by default from the
+ * postgres defined datatypes.
+ */
+#ifdef _AIX
+#ifndef PGDLLIMPORT
+#define PGDLLIMPORT
+#endif  /* PGDLLIMPORT */
+typedef float float4;
+typedef double float8;
+
+#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
+#define pg_noreturn _Noreturn
+#elif defined(__GNUC__)
+#define pg_noreturn __attribute__((noreturn))
+#else
+#define pg_noreturn
+#endif
+
+#include <stdbool.h>
+
+#endif  /*_AIX */
diff --git a/src/include/storage/s_lock.h b/src/include/storage/s_lock.h
index 7f8f566bd40..1a0cd5ec019 100644
--- a/src/include/storage/s_lock.h
+++ b/src/include/storage/s_lock.h
@@ -398,60 +398,20 @@ typedef unsigned int slock_t;
 
 #define TAS(lock) tas(lock)
 
-/* On PPC, it's a win to use a non-locking test before the lwarx */
+/* On PPC, use the compiler provided Built-in functions for atomic memory
+ * exchange operations.
+ */
 #define TAS_SPIN(lock)	(*(lock) ? 1 : TAS(lock))
 
-/*
- * The second operand of addi can hold a constant zero or a register number,
- * hence constraint "=&b" to avoid allocating r0.  "b" stands for "address
- * base register"; most operands having this register-or-zero property are
- * address bases, e.g. the second operand of lwax.
- *
- * NOTE: per the Enhanced PowerPC Architecture manual, v1.0 dated 7-May-2002,
- * an isync is a sufficient synchronization barrier after a lwarx/stwcx loop.
- * But if the spinlock is in ordinary memory, we can use lwsync instead for
- * better performance.
- */
 static __inline__ int
 tas(volatile slock_t *lock)
 {
-	slock_t _t;
-	int _res;
-
-	__asm__ __volatile__(
-"	lwarx   %0,0,%3,1	\n"
-"	cmpwi   %0,0		\n"
-"	bne     1f			\n"
-"	addi    %0,%0,1		\n"
-"	stwcx.  %0,0,%3		\n"
-"	beq     2f			\n"
-"1: \n"
-"	li      %1,1		\n"
-"	b       3f			\n"
-"2: \n"
-"	lwsync				\n"
-"	li      %1,0		\n"
-"3: \n"
-:	"=&b"(_t), "=r"(_res), "+m"(*lock)
-:	"r"(lock)
-:	"memory", "cc");
-	return _res;
+  return __sync_lock_test_and_set(lock, 1);
 }
-
-/*
- * PowerPC S_UNLOCK is almost standard but requires a "sync" instruction.
- * But we can use lwsync instead for better performance.
- */
-#define S_UNLOCK(lock)	\
-do \
-{ \
-	__asm__ __volatile__ ("	lwsync \n" ::: "memory"); \
-	*((volatile slock_t *) (lock)) = 0; \
-} while (0)
+#define S_UNLOCK(lock) __sync_lock_release(lock)
 
 #endif /* powerpc */
-
-
+ 
 #if defined(__mips__) && !defined(__sgi)	/* non-SGI MIPS */
 #define HAS_TEST_AND_SET
 
diff --git a/src/interfaces/ecpg/compatlib/meson.build b/src/interfaces/ecpg/compatlib/meson.build
index 56e0a21651b..3f39187cdcc 100644
--- a/src/interfaces/ecpg/compatlib/meson.build
+++ b/src/interfaces/ecpg/compatlib/meson.build
@@ -16,7 +16,7 @@ if host_system == 'windows'
 endif
 
 # see src/interfaces/libpq/meson.build
-ecpg_compat_st = static_library('libecpg_compat',
+ecpg_compat_st = static_library('libecpg_compat_static',
   ecpg_compat_sources,
   include_directories: ecpg_compat_inc,
   c_args: ecpg_compat_c_args,
diff --git a/src/interfaces/ecpg/ecpglib/meson.build b/src/interfaces/ecpg/ecpglib/meson.build
index 8f478c6a73e..e9faf290a2b 100644
--- a/src/interfaces/ecpg/ecpglib/meson.build
+++ b/src/interfaces/ecpg/ecpglib/meson.build
@@ -25,7 +25,7 @@ if host_system == 'windows'
 endif
 
 # see src/interfaces/libpq/meson.build
-ecpglib_st = static_library('libecpg',
+ecpglib_st = static_library('libecpg_static',
   ecpglib_sources,
   include_directories: ecpglib_inc,
   c_args: ecpglib_c_args,
diff --git a/src/interfaces/ecpg/pgtypeslib/meson.build b/src/interfaces/ecpg/pgtypeslib/meson.build
index 02301ec9acb..94d1d0ad1ef 100644
--- a/src/interfaces/ecpg/pgtypeslib/meson.build
+++ b/src/interfaces/ecpg/pgtypeslib/meson.build
@@ -21,7 +21,7 @@ if host_system == 'windows'
 endif
 
 # see src/interfaces/libpq/meson.build
-ecpg_pgtypes_st = static_library('libpgtypes',
+ecpg_pgtypes_st = static_library('libpgtypes_static',
   ecpg_pgtypes_sources,
   include_directories: ecpg_pgtypes_inc,
   c_args: ecpg_pgtypes_c_args,
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index a74e885b169..eea175ad14a 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -57,7 +57,7 @@ libpq_so_c_args = ['-DUSE_DYNAMIC_OAUTH']
 # We could try to avoid building the source files twice, but it probably adds
 # more complexity than its worth (reusing object files requires also linking
 # to the library on windows or breaks precompiled headers).
-libpq_st = static_library('libpq',
+libpq_st = static_library('libpq_static',
   libpq_sources,
   include_directories: [libpq_inc],
   c_args: libpq_c_args,
diff --git a/src/makefiles/Makefile.aix b/src/makefiles/Makefile.aix
new file mode 100644
index 00000000000..e91b250fd19
--- /dev/null
+++ b/src/makefiles/Makefile.aix
@@ -0,0 +1,34 @@
+# -blibpath:
+# The path to be inserted into the default path (Index 0 path) field of the
+# loader section. When this flag is presented, the -L paths will not be stored.
+# AIX uses a stricter, more explicit approach. The runtime linker expects to
+# tell it exactly where to look using -blibpath.
+# -blibpath must contain ALL directories where we should look for libraries
+libpath := $(shell echo $(subst -L,:,$(filter -L/%,$(LDFLAGS))) | sed -e's/ //g'):/usr/lib:/lib
+
+# AIX uses a stricter, more explicit approach. The runtime linker expects
+# to tell it exactly where to look using -blibpath.
+rpath = -Wl,-blibpath:'$(rpathdir)$(libpath)'
+
+# gcc needs to know it's building a shared lib, otherwise it'll not emit
+# correct code / link to the right support libraries
+ifeq ($(GCC), yes)
+LDFLAGS_SL += -shared
+endif
+
+# env var name to use in place of LD_LIBRARY_PATH
+ld_library_path_var = LIBPATH
+
+POSTGRES_IMP= postgres.imp
+
+ifdef PGXS
+BE_DLLLIBS= -Wl,-bI:$(pkglibdir)/$(POSTGRES_IMP)
+else
+BE_DLLLIBS= -Wl,-bI:$(top_builddir)/src/backend/$(POSTGRES_IMP)
+endif
+
+MKLDEXPORT_DIR=src/backend/port/aix
+MKLDEXPORT=$(top_srcdir)/$(MKLDEXPORT_DIR)/mkldexport.sh
+
+%$(DLSUFFIX): %.o
+	$(CC) $(CFLAGS) $*.o $(LDFLAGS) $(LDFLAGS_SL) -o $@ $(BE_DLLLIBS)
diff --git a/src/port/strerror.c b/src/port/strerror.c
index f0746517770..c46b9dc91fc 100644
--- a/src/port/strerror.c
+++ b/src/port/strerror.c
@@ -214,8 +214,10 @@ get_errno_symbol(int errnum)
 			return "ENOTCONN";
 		case ENOTDIR:
 			return "ENOTDIR";
+#if defined(ENOTEMPTY) && (ENOTEMPTY != EEXIST) /* same code on AIX */
 		case ENOTEMPTY:
 			return "ENOTEMPTY";
+#endif
 		case ENOTSOCK:
 			return "ENOTSOCK";
 #ifdef ENOTSUP
diff --git a/src/template/aix b/src/template/aix
new file mode 100644
index 00000000000..22f61093b1b
--- /dev/null
+++ b/src/template/aix
@@ -0,0 +1,6 @@
+# This file is referred for specific flags wrt to AIX build process like
+# cflags.
+# src/template/aix
+
+# Extra CFLAGS for code that will go into a shared library
+CFLAGS_SL=" "
diff --git a/src/tools/gen_export.pl b/src/tools/gen_export.pl
index 86a7742b369..25827c42a68 100644
--- a/src/tools/gen_export.pl
+++ b/src/tools/gen_export.pl
@@ -18,7 +18,8 @@ GetOptions(
 
 if (not(   $format eq 'darwin'
 		or $format eq 'gnu'
-		or $format eq 'win'))
+		or $format eq 'win'
+        or $format eq 'aix'))
 {
 	die "$0: $format is not yet handled (only darwin, gnu, win are)\n";
 }
@@ -46,6 +47,10 @@ elsif ($format eq 'win')
 	}
 	print $output_handle "EXPORTS\n";
 }
+elsif ($format eq 'aix')
+{
+	print $output_handle "#!\n";
+}
 
 while (<$input_handle>)
 {
@@ -63,6 +68,10 @@ while (<$input_handle>)
 		{
 			print $output_handle "    $1;\n";
 		}
+        elsif ($format eq 'aix')
+        {
+            print $output_handle "$1\n";
+        }
 		elsif ($format eq 'win')
 		{
 			print $output_handle "$1 @ $2\n";
-- 
2.41.0

diff --git a/meson.build b/meson.build
index 6e7ddd74683..6ba24187d15 100644
--- a/meson.build
+++ b/meson.build
@@ -206,6 +206,26 @@ if host_system == 'cygwin'
   mod_link_with_name = 'lib@0@.a'
   mod_link_with_dir = 'libdir'
 
+elif host_system == 'aix'
+  sema_kind = 'unnamed_posix'
+  library_path_var = 'LIBPATH'
+  export_file_format = 'aix'
+  export_fmt = '-Wl,-bE:@0@'
+  mod_link_args_fmt = ['-Wl,-bI:@0@']
+  mod_link_with_dir = 'libdir'
+  mod_link_with_name = '@0@.imp'
+  dl_suffix = '.a'
+  # This flag is required to make sure the user spefic float.h is
+  # picked instead of the system float.h header file, which doesnot
+  # have definition like float8, etc
+  cflags += '-D_H_FLOAT'
+
+  # M:SRE sets a flag indicating that an object is a shared library. Seems to
+  # work in some circumstances without, but required in others.
+  ldflags_sl += '-Wl,-bM:SRE'
+  ldflags_be += '-Wl,-brtllib'
+
+
 elif host_system == 'darwin'
   dlsuffix = '.dylib'
   library_path_var = 'DYLD_LIBRARY_PATH'
@@ -1765,10 +1785,49 @@ endforeach
 # as long, char, short, or int.  Note that we intentionally do not consider
 # any types wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8
 # would be too much of a penalty for disk and memory space.
-alignof_double = cdata.get('ALIGNOF_DOUBLE')
-if cc.alignment('int64_t', args: test_c_args, prefix: '#include <stdint.h>') > alignof_double
-  error('alignment of int64_t is greater than the alignment of double')
-endif
+if host_system != 'aix'
+  alignof_double = cdata.get('ALIGNOF_DOUBLE')
+  if cc.alignment('int64_t', args: test_c_args, prefix: '#include <stdint.h>') > alignof_double
+       error('alignment of int64_t is greater than the alignment of double')
+  endif
+else
+  # The AIX 'power' alignment rules apply the natural alignment of the "first
+  # member" if it is of a floating-point data type (or is an aggregate whose
+  # recursively "first" member or element is such a type). The alignment
+  # associated with these types for subsequent members use an alignment value
+  # where the floating-point data type is considered to have 4-byte alignment.
+  # More info
+  # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99557
+  #
+  # The double is aligned to 4-bytes on AIX in aggregates. But to maintain
+  # alignement across platforms the max alignment of long should be considered.
+
+  # Get the alignment values
+  ac_cv_alignof_long    = cc.alignment('long', args: test_c_args, prefix: '#include <stdint.h>')
+  ac_cv_alignof_double  = cc.alignment('double', args: test_c_args, prefix: '#include <stdint.h>') 
+  ac_cv_alignof_int64_t = cc.alignment('int64_t', args: test_c_args, prefix: '#include <stdint.h>')
+ 
+  message('Alignment of long    : @0@'.format(ac_cv_alignof_long))
+  message('Alignment of double  : @0@'.format(ac_cv_alignof_double))
+  message('Alignment of int64_t : @0@'.format(ac_cv_alignof_int64_t))
+  
+  # Start with long
+  alignof_double = ac_cv_alignof_long
+  message('MAX ALIGN ac_cv_alignof_long')
+
+  # Compare with double
+  if alignof_double < ac_cv_alignof_double
+    alignof_double = ac_cv_alignof_double
+    message('MAX ALIGN ac_cv_alignof_double')
+  endif
+
+  # Compare with int64_t
+  if alignof_double < ac_cv_alignof_int64_t
+    alignof_double = ac_cv_alignof_int64_t
+    message('MAX ALIGN ac_cv_alignof_int64_t')
+  endif
+endif
+message('MAX ALIGN OF DOUBLE : @0@'.format(alignof_double))
 cdata.set('MAXIMUM_ALIGNOF', alignof_double)
 
 cdata.set('SIZEOF_LONG', cc.sizeof('long', args: test_c_args))
@@ -3466,13 +3525,17 @@ endif
 installed_targets = [
   backend_targets,
   bin_targets,
-  libpq_st,
   pl_targets,
   contrib_targets,
   nls_mo_targets,
   ecpg_targets,
 ]
 
+# The static libpq is skipped in AIX. This is not required.
+if host_system != 'aix'
+  installed_targets += [libpq_st]
+endif
+
 if oauth_flow_supported
   installed_targets += [
     libpq_oauth_so,
@@ -3816,7 +3879,13 @@ add_test_setup('running',
 ###############################################################
 
 alias_target('backend', backend_targets)
-alias_target('bin', bin_targets + [libpq_st])
+if host_system != 'aix'
+  alias_target('bin', bin_targets + [libpq_st])
+else
+  # The static libpq is skipped in AIX. This is not required.
+  alias_target('bin', bin_targets)
+endif
+
 alias_target('pl', pl_targets)
 alias_target('contrib', contrib_targets)
 alias_target('testprep', testprep_targets)
diff --git a/src/backend/meson.build b/src/backend/meson.build
index b831a541652..4838f245ab3 100644
--- a/src/backend/meson.build
+++ b/src/backend/meson.build
@@ -125,6 +125,24 @@ if host_system == 'windows'
     '--FILEDESC', 'PostgreSQL Server',])
 endif
 
+if host_system == 'aix'
+  # The '.' argument leads mkldexport.sh to emit "#! .", which refers to the
+  # main executable, allowing extension libraries to resolve their undefined
+  # symbols to symbols in the postgres binary.
+  postgres_imp = custom_target('postgres.imp',
+    command: [files('port/aix/mkldexport.sh'), '@INPUT@', '.'],
+    input: postgres_lib,
+    output: 'postgres.imp',
+    capture: true,
+    install: true,
+    install_dir: dir_lib,
+    build_by_default: false,
+  )
+  backend_link_args += '-Wl,-bE:@0@'.format(postgres_imp.full_path())
+  backend_link_depends += postgres_imp
+endif
+
+
 postgres = executable('postgres',
   backend_input,
   sources: post_export_backend_sources,
diff --git a/src/interfaces/ecpg/compatlib/meson.build b/src/interfaces/ecpg/compatlib/meson.build
index 56e0a21651b..af96e375a9b 100644
--- a/src/interfaces/ecpg/compatlib/meson.build
+++ b/src/interfaces/ecpg/compatlib/meson.build
@@ -16,6 +16,7 @@ if host_system == 'windows'
 endif
 
 # see src/interfaces/libpq/meson.build
+if host_system != 'aix'
 ecpg_compat_st = static_library('libecpg_compat',
   ecpg_compat_sources,
   include_directories: ecpg_compat_inc,
@@ -25,6 +26,7 @@ ecpg_compat_st = static_library('libecpg_compat',
   kwargs: default_lib_args,
 )
 ecpg_targets += ecpg_compat_st
+endif
 
 ecpg_compat_so = shared_library('libecpg_compat',
   ecpg_compat_sources + ecpg_compat_so_sources,
diff --git a/src/interfaces/ecpg/ecpglib/meson.build b/src/interfaces/ecpg/ecpglib/meson.build
index 8f478c6a73e..7d28cd67388 100644
--- a/src/interfaces/ecpg/ecpglib/meson.build
+++ b/src/interfaces/ecpg/ecpglib/meson.build
@@ -25,6 +25,7 @@ if host_system == 'windows'
 endif
 
 # see src/interfaces/libpq/meson.build
+if host_system != 'aix'
 ecpglib_st = static_library('libecpg',
   ecpglib_sources,
   include_directories: ecpglib_inc,
@@ -35,6 +36,7 @@ ecpglib_st = static_library('libecpg',
   kwargs: default_lib_args,
 )
 ecpg_targets += ecpglib_st
+endif
 
 ecpglib_so = shared_library('libecpg',
   ecpglib_sources + ecpglib_so_sources,
diff --git a/src/interfaces/ecpg/pgtypeslib/meson.build b/src/interfaces/ecpg/pgtypeslib/meson.build
index 02301ec9acb..97f4e1c6eda 100644
--- a/src/interfaces/ecpg/pgtypeslib/meson.build
+++ b/src/interfaces/ecpg/pgtypeslib/meson.build
@@ -21,6 +21,7 @@ if host_system == 'windows'
 endif
 
 # see src/interfaces/libpq/meson.build
+if host_system != 'aix'
 ecpg_pgtypes_st = static_library('libpgtypes',
   ecpg_pgtypes_sources,
   include_directories: ecpg_pgtypes_inc,
@@ -30,6 +31,7 @@ ecpg_pgtypes_st = static_library('libpgtypes',
   kwargs: default_lib_args,
 )
 ecpg_targets += ecpg_pgtypes_st
+endif
 
 ecpg_pgtypes_so = shared_library('libpgtypes',
   ecpg_pgtypes_sources + ecpg_pgtypes_so_sources,
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index a74e885b169..98ced9376d9 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -57,6 +57,7 @@ libpq_so_c_args = ['-DUSE_DYNAMIC_OAUTH']
 # We could try to avoid building the source files twice, but it probably adds
 # more complexity than its worth (reusing object files requires also linking
 # to the library on windows or breaks precompiled headers).
+if host_system != 'aix'
 libpq_st = static_library('libpq',
   libpq_sources,
   include_directories: [libpq_inc],
@@ -65,6 +66,7 @@ libpq_st = static_library('libpq',
   dependencies: [frontend_stlib_code, libpq_deps],
   kwargs: default_lib_args,
 )
+endif
 
 libpq_so = shared_library('libpq',
   libpq_sources + libpq_so_sources,

diff --git a/meson.build b/meson.build
index 304a9184075..6ba24187d15 100644
--- a/meson.build
+++ b/meson.build
@@ -215,15 +215,16 @@ elif host_system == 'aix'
   mod_link_with_dir = 'libdir'
   mod_link_with_name = '@0@.imp'
   dl_suffix = '.a'
-  cppflags += '-D_GNU_SOURCE'
+  # This flag is required to make sure the user spefic float.h is
+  # picked instead of the system float.h header file, which doesnot
+  # have definition like float8, etc
+  cflags += '-D_H_FLOAT'
 
   # M:SRE sets a flag indicating that an object is a shared library. Seems to
   # work in some circumstances without, but required in others.
   ldflags_sl += '-Wl,-bM:SRE'
   ldflags_be += '-Wl,-brtllib'
 
-  # Native memset() is faster, tested on:
-  memset_loop_limit = 0
 
 elif host_system == 'darwin'
   dlsuffix = '.dylib'
@@ -1784,10 +1785,49 @@ endforeach
 # as long, char, short, or int.  Note that we intentionally do not consider
 # any types wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8
 # would be too much of a penalty for disk and memory space.
-alignof_double = cdata.get('ALIGNOF_DOUBLE')
-#if cc.alignment('int64_t', args: test_c_args, prefix: '#include <stdint.h>') > alignof_double
-#  error('alignment of int64_t is greater than the alignment of double')
-#endif
+if host_system != 'aix'
+  alignof_double = cdata.get('ALIGNOF_DOUBLE')
+  if cc.alignment('int64_t', args: test_c_args, prefix: '#include <stdint.h>') > alignof_double
+       error('alignment of int64_t is greater than the alignment of double')
+  endif
+else
+  # The AIX 'power' alignment rules apply the natural alignment of the "first
+  # member" if it is of a floating-point data type (or is an aggregate whose
+  # recursively "first" member or element is such a type). The alignment
+  # associated with these types for subsequent members use an alignment value
+  # where the floating-point data type is considered to have 4-byte alignment.
+  # More info
+  # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99557
+  #
+  # The double is aligned to 4-bytes on AIX in aggregates. But to maintain
+  # alignement across platforms the max alignment of long should be considered.
+
+  # Get the alignment values
+  ac_cv_alignof_long    = cc.alignment('long', args: test_c_args, prefix: '#include <stdint.h>')
+  ac_cv_alignof_double  = cc.alignment('double', args: test_c_args, prefix: '#include <stdint.h>') 
+  ac_cv_alignof_int64_t = cc.alignment('int64_t', args: test_c_args, prefix: '#include <stdint.h>')
+ 
+  message('Alignment of long    : @0@'.format(ac_cv_alignof_long))
+  message('Alignment of double  : @0@'.format(ac_cv_alignof_double))
+  message('Alignment of int64_t : @0@'.format(ac_cv_alignof_int64_t))
+  
+  # Start with long
+  alignof_double = ac_cv_alignof_long
+  message('MAX ALIGN ac_cv_alignof_long')
+
+  # Compare with double
+  if alignof_double < ac_cv_alignof_double
+    alignof_double = ac_cv_alignof_double
+    message('MAX ALIGN ac_cv_alignof_double')
+  endif
+
+  # Compare with int64_t
+  if alignof_double < ac_cv_alignof_int64_t
+    alignof_double = ac_cv_alignof_int64_t
+    message('MAX ALIGN ac_cv_alignof_int64_t')
+  endif
+endif
+message('MAX ALIGN OF DOUBLE : @0@'.format(alignof_double))
 cdata.set('MAXIMUM_ALIGNOF', alignof_double)
 
 cdata.set('SIZEOF_LONG', cc.sizeof('long', args: test_c_args))
@@ -1839,7 +1879,7 @@ if cc.links('''
   if not meson.is_cross_build()
     r = cc.run('''
     /* This must match the corresponding code in c.h: */
-    #if defined(__GNUC__) || defined(__IBMC__)
+    #if defined(__GNUC__)
     #define pg_attribute_aligned(a) __attribute__((aligned(a)))
     #elif defined(_MSC_VER)
     #define pg_attribute_aligned(a) __declspec(align(a))
@@ -3485,13 +3525,17 @@ endif
 installed_targets = [
   backend_targets,
   bin_targets,
-  libpq_st,
   pl_targets,
   contrib_targets,
   nls_mo_targets,
   ecpg_targets,
 ]
 
+# The static libpq is skipped in AIX. This is not required.
+if host_system != 'aix'
+  installed_targets += [libpq_st]
+endif
+
 if oauth_flow_supported
   installed_targets += [
     libpq_oauth_so,
@@ -3835,7 +3879,13 @@ add_test_setup('running',
 ###############################################################
 
 alias_target('backend', backend_targets)
-alias_target('bin', bin_targets + [libpq_st])
+if host_system != 'aix'
+  alias_target('bin', bin_targets + [libpq_st])
+else
+  # The static libpq is skipped in AIX. This is not required.
+  alias_target('bin', bin_targets)
+endif
+
 alias_target('pl', pl_targets)
 alias_target('contrib', contrib_targets)
 alias_target('testprep', testprep_targets)
diff --git a/src/include/port/aix.h b/src/include/port/aix.h
index dd7cfb197cd..c86983a4452 100644
--- a/src/include/port/aix.h
+++ b/src/include/port/aix.h
@@ -1,26 +1,3 @@
 /*
  * src/include/port/aix.h
  */
-
-/* This change is required for the meson changes as the autoconf is not run and
- * to resolve the conflicts in picking the float.h details by default from the
- * postgres defined datatypes.
- */
-#ifdef _AIX
-#ifndef PGDLLIMPORT
-#define PGDLLIMPORT
-#endif  /* PGDLLIMPORT */
-typedef float float4;
-typedef double float8;
-
-#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 201112L
-#define pg_noreturn _Noreturn
-#elif defined(__GNUC__)
-#define pg_noreturn __attribute__((noreturn))
-#else
-#define pg_noreturn
-#endif
-
-#include <stdbool.h>
-
-#endif  /*_AIX */
diff --git a/src/interfaces/ecpg/compatlib/meson.build b/src/interfaces/ecpg/compatlib/meson.build
index 3f39187cdcc..af96e375a9b 100644
--- a/src/interfaces/ecpg/compatlib/meson.build
+++ b/src/interfaces/ecpg/compatlib/meson.build
@@ -16,7 +16,8 @@ if host_system == 'windows'
 endif
 
 # see src/interfaces/libpq/meson.build
-ecpg_compat_st = static_library('libecpg_compat_static',
+if host_system != 'aix'
+ecpg_compat_st = static_library('libecpg_compat',
   ecpg_compat_sources,
   include_directories: ecpg_compat_inc,
   c_args: ecpg_compat_c_args,
@@ -25,6 +26,7 @@ ecpg_compat_st = static_library('libecpg_compat_static',
   kwargs: default_lib_args,
 )
 ecpg_targets += ecpg_compat_st
+endif
 
 ecpg_compat_so = shared_library('libecpg_compat',
   ecpg_compat_sources + ecpg_compat_so_sources,
diff --git a/src/interfaces/ecpg/ecpglib/meson.build b/src/interfaces/ecpg/ecpglib/meson.build
index e9faf290a2b..7d28cd67388 100644
--- a/src/interfaces/ecpg/ecpglib/meson.build
+++ b/src/interfaces/ecpg/ecpglib/meson.build
@@ -25,7 +25,8 @@ if host_system == 'windows'
 endif
 
 # see src/interfaces/libpq/meson.build
-ecpglib_st = static_library('libecpg_static',
+if host_system != 'aix'
+ecpglib_st = static_library('libecpg',
   ecpglib_sources,
   include_directories: ecpglib_inc,
   c_args: ecpglib_c_args,
@@ -35,6 +36,7 @@ ecpglib_st = static_library('libecpg_static',
   kwargs: default_lib_args,
 )
 ecpg_targets += ecpglib_st
+endif
 
 ecpglib_so = shared_library('libecpg',
   ecpglib_sources + ecpglib_so_sources,
diff --git a/src/interfaces/ecpg/pgtypeslib/meson.build b/src/interfaces/ecpg/pgtypeslib/meson.build
index 94d1d0ad1ef..97f4e1c6eda 100644
--- a/src/interfaces/ecpg/pgtypeslib/meson.build
+++ b/src/interfaces/ecpg/pgtypeslib/meson.build
@@ -21,7 +21,8 @@ if host_system == 'windows'
 endif
 
 # see src/interfaces/libpq/meson.build
-ecpg_pgtypes_st = static_library('libpgtypes_static',
+if host_system != 'aix'
+ecpg_pgtypes_st = static_library('libpgtypes',
   ecpg_pgtypes_sources,
   include_directories: ecpg_pgtypes_inc,
   c_args: ecpg_pgtypes_c_args,
@@ -30,6 +31,7 @@ ecpg_pgtypes_st = static_library('libpgtypes_static',
   kwargs: default_lib_args,
 )
 ecpg_targets += ecpg_pgtypes_st
+endif
 
 ecpg_pgtypes_so = shared_library('libpgtypes',
   ecpg_pgtypes_sources + ecpg_pgtypes_so_sources,
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index eea175ad14a..98ced9376d9 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -57,7 +57,8 @@ libpq_so_c_args = ['-DUSE_DYNAMIC_OAUTH']
 # We could try to avoid building the source files twice, but it probably adds
 # more complexity than its worth (reusing object files requires also linking
 # to the library on windows or breaks precompiled headers).
-libpq_st = static_library('libpq_static',
+if host_system != 'aix'
+libpq_st = static_library('libpq',
   libpq_sources,
   include_directories: [libpq_inc],
   c_args: libpq_c_args,
@@ -65,6 +66,7 @@ libpq_st = static_library('libpq_static',
   dependencies: [frontend_stlib_code, libpq_deps],
   kwargs: default_lib_args,
 )
+endif
 
 libpq_so = shared_library('libpq',
   libpq_sources + libpq_so_sources,
diff --git a/src/tools/gen_export.pl b/src/tools/gen_export.pl
index 25827c42a68..19c8b60560f 100644
--- a/src/tools/gen_export.pl
+++ b/src/tools/gen_export.pl
@@ -21,7 +21,7 @@ if (not(   $format eq 'darwin'
 		or $format eq 'win'
         or $format eq 'aix'))
 {
-	die "$0: $format is not yet handled (only darwin, gnu, win are)\n";
+	die "$0: $format is not yet handled (only darwin, gnu, win, aix are)\n";
 }
 
 open(my $input_handle, '<', $input)

diff --git a/meson.build b/meson.build
index 6e7ddd74683..0c03481d721 100644
--- a/meson.build
+++ b/meson.build
@@ -198,6 +198,8 @@ endif
 # that purpose.
 portname = host_system

+dep_static_lib = declare_dependency()
+
 if host_system == 'cygwin'
   sema_kind = 'unnamed_posix'
   cppflags += '-D_GNU_SOURCE'
@@ -206,6 +208,32 @@ if host_system == 'cygwin'
   mod_link_with_name = 'lib@0@.a'
   mod_link_with_dir = 'libdir'

+elif host_system == 'aix'
+  sema_kind = 'unnamed_posix'
+  library_path_var = 'LIBPATH'
+  export_file_format = 'aix'
+  export_fmt = '-Wl,-bE:@0@'
+  mod_link_args_fmt = ['-Wl,-bI:@0@']
+  mod_link_with_dir = 'libdir'
+  mod_link_with_name = '@0@.imp'
+  dl_suffix = '.a'
+  # This flag is required to make sure the user spefic float.h is
+  # picked instead of the system float.h header file, which doesnot
+  # have definition like float8, etc
+  cflags += '-D_H_FLOAT'
+
+  # M:SRE sets a flag indicating that an object is a shared library. Seems to
+  # work in some circumstances without, but required in others.
+  ldflags_sl += '-Wl,-bM:SRE'
+  ldflags_be += '-Wl,-brtllib'
+
+  # https://mesonbuild.com/Release-notes-for-1-6-0.html
+  # According to Mesons documentation for AIX, both shared and static libraries
+  # are typically archived, and they should have distinct names if a project
+  # requires building both. However, in this case, only shared libraries are
+  # used on AIX, so we are skipping the build for static libraries.
+  dep_static_lib = disabler()
+
 elif host_system == 'darwin'
   dlsuffix = '.dylib'
   library_path_var = 'DYLD_LIBRARY_PATH'
@@ -1765,10 +1793,49 @@ endforeach
 # as long, char, short, or int.  Note that we intentionally do not consider
 # any types wider than 64 bits, as allowing MAXIMUM_ALIGNOF to exceed 8
 # would be too much of a penalty for disk and memory space.
-alignof_double = cdata.get('ALIGNOF_DOUBLE')
-if cc.alignment('int64_t', args: test_c_args, prefix: '#include <stdint.h>') > alignof_double
-  error('alignment of int64_t is greater than the alignment of double')
-endif
+if host_system != 'aix'
+  alignof_double = cdata.get('ALIGNOF_DOUBLE')
+  if cc.alignment('int64_t', args: test_c_args, prefix: '#include <stdint.h>') > alignof_double
+       error('alignment of int64_t is greater than the alignment of double')
+  endif
+else
+  # The AIX 'power' alignment rules apply the natural alignment of the "first
+  # member" if it is of a floating-point data type (or is an aggregate whose
+  # recursively "first" member or element is such a type). The alignment
+  # associated with these types for subsequent members use an alignment value
+  # where the floating-point data type is considered to have 4-byte alignment.
+  # More info
+  # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99557
+  #
+  # The double is aligned to 4-bytes on AIX in aggregates. But to maintain
+  # alignement across platforms the max alignment of long should be considered.
+
+  # Get the alignment values
+  ac_cv_alignof_long    = cc.alignment('long', args: test_c_args, prefix: '#include <stdint.h>')
+  ac_cv_alignof_double  = cc.alignment('double', args: test_c_args, prefix: '#include <stdint.h>')
+  ac_cv_alignof_int64_t = cc.alignment('int64_t', args: test_c_args, prefix: '#include <stdint.h>')
+
+  message('Alignment of long    : @0@'.format(ac_cv_alignof_long))
+  message('Alignment of double  : @0@'.format(ac_cv_alignof_double))
+  message('Alignment of int64_t : @0@'.format(ac_cv_alignof_int64_t))
+
+  # Start with long
+  alignof_double = ac_cv_alignof_long
+  message('MAX ALIGN ac_cv_alignof_long')
+
+  # Compare with double
+  if alignof_double < ac_cv_alignof_double
+    alignof_double = ac_cv_alignof_double
+    message('MAX ALIGN ac_cv_alignof_double')
+  endif
+
+  # Compare with int64_t
+  if alignof_double < ac_cv_alignof_int64_t
+    alignof_double = ac_cv_alignof_int64_t
+    message('MAX ALIGN ac_cv_alignof_int64_t')
+  endif
+endif
+message('MAX ALIGN OF DOUBLE : @0@'.format(alignof_double))
 cdata.set('MAXIMUM_ALIGNOF', alignof_double)

 cdata.set('SIZEOF_LONG', cc.sizeof('long', args: test_c_args))
@@ -3466,13 +3533,17 @@ endif
 installed_targets = [
   backend_targets,
   bin_targets,
-  libpq_st,
   pl_targets,
   contrib_targets,
   nls_mo_targets,
   ecpg_targets,
 ]

+# Include the libpq only if its build. For AIX its skipped.
+if not dep_static_lib.disabled()
+  installed_targets += [libpq_st]
+endif
+
 if oauth_flow_supported
   installed_targets += [
     libpq_oauth_so,
diff --git a/src/backend/meson.build b/src/backend/meson.build
index b831a541652..4838f245ab3 100644
--- a/src/backend/meson.build
+++ b/src/backend/meson.build
@@ -125,6 +125,24 @@ if host_system == 'windows'
     '--FILEDESC', 'PostgreSQL Server',])
 endif

+if host_system == 'aix'
+  # The '.' argument leads mkldexport.sh to emit "#! .", which refers to the
+  # main executable, allowing extension libraries to resolve their undefined
+  # symbols to symbols in the postgres binary.
+  postgres_imp = custom_target('postgres.imp',
+    command: [files('port/aix/mkldexport.sh'), '@INPUT@', '.'],
+    input: postgres_lib,
+    output: 'postgres.imp',
+    capture: true,
+    install: true,
+    install_dir: dir_lib,
+    build_by_default: false,
+  )
+  backend_link_args += '-Wl,-bE:@0@'.format(postgres_imp.full_path())
+  backend_link_depends += postgres_imp
+endif
+
+
 postgres = executable('postgres',
   backend_input,
   sources: post_export_backend_sources,
diff --git a/src/interfaces/ecpg/compatlib/meson.build b/src/interfaces/ecpg/compatlib/meson.build
index 56e0a21651b..5d32636c1e3 100644
--- a/src/interfaces/ecpg/compatlib/meson.build
+++ b/src/interfaces/ecpg/compatlib/meson.build
@@ -20,11 +20,13 @@ ecpg_compat_st = static_library('libecpg_compat',
   ecpg_compat_sources,
   include_directories: ecpg_compat_inc,
   c_args: ecpg_compat_c_args,
-  dependencies: [frontend_stlib_code, thread_dep],
+  dependencies: [frontend_stlib_code, thread_dep, dep_static_lib],
   link_with: [ecpglib_st, ecpg_pgtypes_st],
   kwargs: default_lib_args,
 )
-ecpg_targets += ecpg_compat_st
+if not dep_static_lib.disabled()
+  ecpg_targets += ecpg_compat_st
+endif

 ecpg_compat_so = shared_library('libecpg_compat',
   ecpg_compat_sources + ecpg_compat_so_sources,
diff --git a/src/interfaces/ecpg/ecpglib/meson.build b/src/interfaces/ecpg/ecpglib/meson.build
index 8f478c6a73e..3c61bdeeffd 100644
--- a/src/interfaces/ecpg/ecpglib/meson.build
+++ b/src/interfaces/ecpg/ecpglib/meson.build
@@ -30,11 +30,13 @@ ecpglib_st = static_library('libecpg',
   include_directories: ecpglib_inc,
   c_args: ecpglib_c_args,
   c_pch: pch_postgres_fe_h,
-  dependencies: [frontend_stlib_code, thread_dep, libpq],
+  dependencies: [frontend_stlib_code, thread_dep, libpq, dep_static_lib],
   link_with: [ecpg_pgtypes_st],
   kwargs: default_lib_args,
 )
-ecpg_targets += ecpglib_st
+if not ecpglib_st.disabled()
+  ecpg_targets += ecpglib_st
+endif

 ecpglib_so = shared_library('libecpg',
   ecpglib_sources + ecpglib_so_sources,
diff --git a/src/interfaces/ecpg/pgtypeslib/meson.build b/src/interfaces/ecpg/pgtypeslib/meson.build
index 02301ec9acb..b6fc20e9db6 100644
--- a/src/interfaces/ecpg/pgtypeslib/meson.build
+++ b/src/interfaces/ecpg/pgtypeslib/meson.build
@@ -26,10 +26,12 @@ ecpg_pgtypes_st = static_library('libpgtypes',
   include_directories: ecpg_pgtypes_inc,
   c_args: ecpg_pgtypes_c_args,
   c_pch: pch_postgres_fe_h,
-  dependencies: frontend_stlib_code,
+  dependencies: [frontend_stlib_code, dep_static_lib],
   kwargs: default_lib_args,
 )
-ecpg_targets += ecpg_pgtypes_st
+if not ecpg_pgtypes_st.disabled()
+  ecpg_targets += ecpg_pgtypes_st
+endif

 ecpg_pgtypes_so = shared_library('libpgtypes',
   ecpg_pgtypes_sources + ecpg_pgtypes_so_sources,
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index a74e885b169..ea3f540f8bc 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -62,7 +62,7 @@ libpq_st = static_library('libpq',
   include_directories: [libpq_inc],
   c_args: libpq_c_args,
   c_pch: pch_postgres_fe_h,
-  dependencies: [frontend_stlib_code, libpq_deps],
+  dependencies: [frontend_stlib_code, libpq_deps, dep_static_lib],
   kwargs: default_lib_args,
 )