From 295161e09c41658841a902c57f99da54395b20dd Mon Sep 17 00:00:00 2001
From: Greg Burd <greg@burd.me>
Date: Sun, 23 Nov 2025 07:58:47 -0500
Subject: [PATCH v20251123] WIP ARM64/MSVC stdatomic

---
 doc/src/sgml/installation.sgml |  2 +-
 meson.build                    | 15 ++++++++++++++-
 src/include/port/spin_delay.h  |  7 +++++--
 src/port/pg_crc32c_armv8.c     |  2 ++
 src/tools/msvc_gendef.pl       |  8 ++++----
 5 files changed, 26 insertions(+), 8 deletions(-)

diff --git a/doc/src/sgml/installation.sgml b/doc/src/sgml/installation.sgml
index fe8d73e1f8c..3f8d512a906 100644
--- a/doc/src/sgml/installation.sgml
+++ b/doc/src/sgml/installation.sgml
@@ -3967,7 +3967,7 @@ configure ... LDFLAGS="-R /usr/sfw/lib:/opt/sfw/lib:/usr/local/lib"
    <sect3 id="install-windows-full-64-bit">
     <title>Special Considerations for 64-Bit Windows</title>
     <para>
-     PostgreSQL will only build for the x64 architecture on 64-bit Windows.
+     PostgreSQL will only build for the x64 and ARM64 architectures on 64-bit Windows.
     </para>
     <para>
      Mixing 32- and 64-bit versions in the same build tree is not supported.
diff --git a/meson.build b/meson.build
index 1a2005e75c4..18637180ab1 100644
--- a/meson.build
+++ b/meson.build
@@ -2158,6 +2158,11 @@ endforeach
 
 
 if cc.get_id() == 'msvc'
+  # Add ARM64 architecture flag for Windows 11 ARM64 for correct intrensics
+  if host_machine.system() == 'windows' and host_machine.cpu_family() == 'aarch64'
+    add_project_arguments('/arch:armv9.4', language: ['c', 'cpp'])
+  endif
+
   cflags_warn += [
     # Warnings to disable:
     # from /W1:
@@ -2367,6 +2372,11 @@ if host_cpu == 'x86' or host_cpu == 'x86_64'
   else
 
     prog = '''
+#ifdef _MSC_VER
+#include <intrin.h>
+#else
+#include <arm_acle.h>
+#endif
 #include <nmmintrin.h>
 unsigned int crc;
 
@@ -2450,7 +2460,10 @@ int main(void)
 }
 '''
 
-  if cc.links(prog, name: '__crc32cb, __crc32ch, __crc32cw, and __crc32cd without -march=armv8-a+crc',
+  if cc.get_id() == 'msvc'
+    cdata.set('USE_ARMV8_CRC32C', 1)
+    have_optimized_crc = true
+  elif cc.links(prog, name: '__crc32cb, __crc32ch, __crc32cw, and __crc32cd without -march=armv8-a+crc',
       args: test_c_args)
     # Use ARM CRC Extension unconditionally
     cdata.set('USE_ARMV8_CRC32C', 1)
diff --git a/src/include/port/spin_delay.h b/src/include/port/spin_delay.h
index c583698af8e..f944c8362da 100644
--- a/src/include/port/spin_delay.h
+++ b/src/include/port/spin_delay.h
@@ -69,9 +69,12 @@ pg_spin_delay(void)
 
 	/*
 	 * If using Visual C++ on Win64, inline assembly is unavailable.  Use a
-	 * _mm_pause intrinsic instead of rep nop.
+	 * _mm_pause intrinsic instead of rep nop. For ARM64, use the __yield()
+	 * intrinsic which emits the YIELD instruction as a hint to the processor.
 	 */
-#if defined(_WIN64)
+#if defined(_M_ARM64)
+	__yield();
+#elif defined(_WIN64)
 	_mm_pause();
 #else
 	/* See comment for gcc code. Same code, MASM syntax */
diff --git a/src/port/pg_crc32c_armv8.c b/src/port/pg_crc32c_armv8.c
index 5ba070bb99d..6a155ddde1e 100644
--- a/src/port/pg_crc32c_armv8.c
+++ b/src/port/pg_crc32c_armv8.c
@@ -14,7 +14,9 @@
  */
 #include "c.h"
 
+#ifndef _MSC_VER
 #include <arm_acle.h>
+#endif
 
 #include "port/pg_crc32c.h"
 
diff --git a/src/tools/msvc_gendef.pl b/src/tools/msvc_gendef.pl
index 868aad51b09..c92c94c4775 100644
--- a/src/tools/msvc_gendef.pl
+++ b/src/tools/msvc_gendef.pl
@@ -118,9 +118,9 @@ sub writedef
 	{
 		my $isdata = $def->{$f} eq 'data';
 
-		# Strip the leading underscore for win32, but not x64
+		# Strip the leading underscore for win32, but not x64 and aarch64
 		$f =~ s/^_//
-		  unless ($arch eq "x86_64");
+		  unless ($arch eq "x86_64" || $arch eq "aarch64");
 
 		# Emit just the name if it's a function symbol, or emit the name
 		# decorated with the DATA option for variables.
@@ -141,7 +141,7 @@ sub writedef
 sub usage
 {
 	die("Usage: msvc_gendef.pl --arch <arch> --deffile <deffile> --tempdir <tempdir> files-or-directories\n"
-		  . "    arch: x86 | x86_64\n"
+		  . "    arch: x86 | x86_64 | aarch64\n"
 		  . "    deffile: path of the generated file\n"
 		  . "    tempdir: directory for temporary files\n"
 		  . "    files or directories: object files or directory containing object files\n"
@@ -158,7 +158,7 @@ GetOptions(
 	'tempdir:s' => \$tempdir,) or usage();
 
 usage("arch: $arch")
-  unless ($arch eq 'x86' || $arch eq 'x86_64');
+  unless ($arch eq 'x86' || $arch eq 'x86_64' || $arch eq 'aarch64');
 
 my @files;
 
-- 
2.52.0.windows.1