Subject: [PATCH v2 4/4] Refactor some SIMD and popcount macros.

From: Nathan Bossart <[email-masked]>
Date: Thu, 15 Jan 2026 12:26:31 -0600

---
 meson.build                    |  4 +++-
 src/include/c.h                | 19 +++++++++++++++++
 src/include/port/pg_bitutils.h | 37 +++-------------------------------
 src/include/port/simd.h        | 17 ++--------------
 src/port/pg_bitutils.c         |  4 ++--
 src/port/pg_popcount_aarch64.c |  8 ++++----
 src/port/pg_popcount_x86.c     |  8 ++++----
 7 files changed, 37 insertions(+), 60 deletions(-)

diff --git a/meson.build b/meson.build
index eedd40b8137..299817cb83e 100644
--- a/meson.build
+++ b/meson.build
@@ -2609,7 +2609,9 @@ endif
 
 if host_cpu == 'x86_64'
 
-  if cc.compiles('''
+  if cc.get_id() == 'msvc'
+    cdata.set('HAVE_X86_64_POPCNTQ', 1)
+  elif cc.compiles('''
       void main(void)
       {
           long long x = 1; long long r;
diff --git a/src/include/c.h b/src/include/c.h
index 7136102e5ff..b6d53073fad 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -1230,6 +1230,25 @@ typedef struct PGAlignedXLogBlock
 	((underlying_type) (expr))
 #endif
 
+/*
+ * SSE2 instructions are part of the spec for the 64-bit x86 ISA. We assume
+ * that compilers targeting this architecture understand SSE2 intrinsics.
+ */
+#if (defined(__x86_64__) || defined(_M_AMD64))
+#define USE_SSE2
+
+/*
+ * We use the Neon instructions if the compiler provides access to them (as
+ * indicated by __ARM_NEON) and we are on aarch64.  While Neon support is
+ * technically optional for aarch64, it appears that all available 64-bit
+ * hardware does have it.  Neon exists in some 32-bit hardware too, but we
+ * could not realistically use it there without a run-time check, which seems
+ * not worth the trouble for now.
+ */
+#elif defined(__aarch64__) && defined(__ARM_NEON)
+#define USE_NEON
+#endif
+
 /* ----------------------------------------------------------------
  *				Section 9: system-specific hacks
  *
diff --git a/src/include/port/pg_bitutils.h b/src/include/port/pg_bitutils.h
index 89b117d9817..35761f509ec 100644
--- a/src/include/port/pg_bitutils.h
+++ b/src/include/port/pg_bitutils.h
@@ -276,43 +276,12 @@ pg_ceil_log2_64(uint64 num)
 		return pg_leftmost_one_pos64(num - 1) + 1;
 }
 
-/*
- * With MSVC on x86_64 builds, try using native popcnt instructions via the
- * __popcnt and __popcnt64 intrinsics.  These don't work the same as GCC's
- * __builtin_popcount* intrinsic functions as they always emit popcnt
- * instructions.
- */
-#if defined(_MSC_VER) && defined(_M_AMD64)
-#define HAVE_X86_64_POPCNTQ
-#endif
-
-/*
- * On x86_64, we can use the hardware popcount instruction, but only if
- * we can verify that the CPU supports it via the cpuid instruction.
- *
- * Otherwise, we fall back to a hand-rolled implementation.
- */
-#ifdef HAVE_X86_64_POPCNTQ
-#if defined(HAVE__GET_CPUID) || defined(HAVE__CPUID)
-#define TRY_POPCNT_X86_64 1
-#endif
-#endif
-
-/*
- * On AArch64, we can use Neon instructions if the compiler provides access to
- * them (as indicated by __ARM_NEON).  As in simd.h, we assume that all
- * available 64-bit hardware has Neon support.
- */
-#if defined(__aarch64__) && defined(__ARM_NEON)
-#define POPCNT_AARCH64 1
-#endif
-
 extern int	pg_popcount32_portable(uint32 word);
 extern int	pg_popcount64_portable(uint64 word);
 extern uint64 pg_popcount_portable(const char *buf, int bytes);
 extern uint64 pg_popcount_masked_portable(const char *buf, int bytes, bits8 mask);
 
-#ifdef TRY_POPCNT_X86_64
+#ifdef HAVE_X86_64_POPCNTQ
 /*
  * Attempt to use SSE4.2 or AVX-512 instructions, but perform a runtime check
  * first.
@@ -322,7 +291,7 @@ extern PGDLLIMPORT int (*pg_popcount64) (uint64 word);
 extern PGDLLIMPORT uint64 (*pg_popcount_optimized) (const char *buf, int bytes);
 extern PGDLLIMPORT uint64 (*pg_popcount_masked_optimized) (const char *buf, int bytes, bits8 mask);
 
-#elif POPCNT_AARCH64
+#elif defined(USE_NEON)
 /* Use the Neon version of pg_popcount{32,64} without function pointer. */
 extern int	pg_popcount32(uint32 word);
 extern int	pg_popcount64(uint64 word);
@@ -346,7 +315,7 @@ extern int	pg_popcount64(uint64 word);
 extern uint64 pg_popcount_optimized(const char *buf, int bytes);
 extern uint64 pg_popcount_masked_optimized(const char *buf, int bytes, bits8 mask);
 
-#endif							/* TRY_POPCNT_X86_64 */
+#endif
 
 /*
  * Returns the number of 1-bits in buf.
diff --git a/src/include/port/simd.h b/src/include/port/simd.h
index 33202a4b0e2..50615aec7f4 100644
--- a/src/include/port/simd.h
+++ b/src/include/port/simd.h
@@ -18,32 +18,19 @@
 #ifndef SIMD_H
 #define SIMD_H
 
-#if (defined(__x86_64__) || defined(_M_AMD64))
+#if defined(USE_SSE2)
 /*
- * SSE2 instructions are part of the spec for the 64-bit x86 ISA. We assume
- * that compilers targeting this architecture understand SSE2 intrinsics.
- *
  * We use emmintrin.h rather than the comprehensive header immintrin.h in
  * order to exclude extensions beyond SSE2. This is because MSVC, at least,
  * will allow the use of intrinsics that haven't been enabled at compile
  * time.
  */
 #include <emmintrin.h>
-#define USE_SSE2
 typedef __m128i Vector8;
 typedef __m128i Vector32;
 
-#elif defined(__aarch64__) && defined(__ARM_NEON)
-/*
- * We use the Neon instructions if the compiler provides access to them (as
- * indicated by __ARM_NEON) and we are on aarch64.  While Neon support is
- * technically optional for aarch64, it appears that all available 64-bit
- * hardware does have it.  Neon exists in some 32-bit hardware too, but we
- * could not realistically use it there without a run-time check, which seems
- * not worth the trouble for now.
- */
+#elif defined(USE_NEON)
 #include <arm_neon.h>
-#define USE_NEON
 typedef uint8x16_t Vector8;
 typedef uint32x4_t Vector32;
 
diff --git a/src/port/pg_bitutils.c b/src/port/pg_bitutils.c
index 170aeef7548..ffda75825e5 100644
--- a/src/port/pg_bitutils.c
+++ b/src/port/pg_bitutils.c
@@ -242,7 +242,7 @@ pg_popcount_masked_portable(const char *buf, int bytes, bits8 mask)
 	return popcnt;
 }
 
-#if !defined(TRY_POPCNT_X86_64) && !defined(POPCNT_AARCH64)
+#if !defined(HAVE_X86_64_POPCNTQ) && !defined(USE_NEON)
 
 /*
  * When special CPU instructions are not available, there's no point in using
@@ -282,4 +282,4 @@ pg_popcount_masked_optimized(const char *buf, int bytes, bits8 mask)
 	return pg_popcount_masked_portable(buf, bytes, mask);
 }
 
-#endif							/* ! TRY_POPCNT_X86_64 && ! POPCNT_AARCH64 */
+#endif							/* ! HAVE_X86_64_POPCNTQ && ! USE_NEON */
diff --git a/src/port/pg_popcount_aarch64.c b/src/port/pg_popcount_aarch64.c
index cda73cf6088..2184854dbf7 100644
--- a/src/port/pg_popcount_aarch64.c
+++ b/src/port/pg_popcount_aarch64.c
@@ -12,9 +12,7 @@
  */
 #include "c.h"
 
-#include "port/pg_bitutils.h"
-
-#ifdef POPCNT_AARCH64
+#ifdef USE_NEON
 
 #include <arm_neon.h>
 
@@ -30,6 +28,8 @@
 #endif
 #endif
 
+#include "port/pg_bitutils.h"
+
 /*
  * The Neon versions are built regardless of whether we are building the SVE
  * versions.
@@ -478,4 +478,4 @@ pg_popcount_masked_neon(const char *buf, int bytes, bits8 mask)
 	return popcnt;
 }
 
-#endif							/* POPCNT_AARCH64 */
+#endif							/* USE_NEON */
diff --git a/src/port/pg_popcount_x86.c b/src/port/pg_popcount_x86.c
index f88511dcc7c..b17d90da340 100644
--- a/src/port/pg_popcount_x86.c
+++ b/src/port/pg_popcount_x86.c
@@ -12,9 +12,7 @@
  */
 #include "c.h"
 
-#include "port/pg_bitutils.h"
-
-#ifdef TRY_POPCNT_X86_64
+#ifdef HAVE_X86_64_POPCNTQ
 
 #if defined(HAVE__GET_CPUID) || defined(HAVE__GET_CPUID_COUNT)
 #include <cpuid.h>
@@ -28,6 +26,8 @@
 #include <intrin.h>
 #endif
 
+#include "port/pg_bitutils.h"
+
 /*
  * The SSE4.2 versions are built regardless of whether we are building the
  * AVX-512 versions.
@@ -468,4 +468,4 @@ pg_popcount_masked_sse42(const char *buf, int bytes, bits8 mask)
 	return popcnt;
 }
 
-#endif							/* TRY_POPCNT_X86_64 */
+#endif							/* HAVE_X86_64_POPCNTQ */
-- 
2.50.1 (Apple Git-155)

--KuW0xlRTZoVkcm/J--