v5-0001-SVE-support-for-popcount-and-popcount-masked.patch

From 57668e64b861b9a722e30d452967376231841e59 Mon Sep 17 00:00:00 2001
From: Chiranmoy Bhattacharya <chiranmoy.bhattacharya@fujitsu.com>
Date: Wed, 19 Feb 2025 12:30:47 +0530
Subject: [PATCH v4] SVE support for popcount and popcount masked

---
 config/c-compiler.m4           |  36 ++++++++++
 configure                      |  56 +++++++++++++++
 configure.ac                   |   9 +++
 meson.build                    |  33 +++++++++
 src/include/pg_config.h.in     |   3 +
 src/include/port/pg_bitutils.h |  13 ++++
 src/port/Makefile              |   1 +
 src/port/meson.build           |   1 +
 src/port/pg_bitutils.c         |  44 +++++++++++-
 src/port/pg_popcount_sve.c     | 123 +++++++++++++++++++++++++++++++++
 10 files changed, 318 insertions(+), 1 deletion(-)
 create mode 100644 src/port/pg_popcount_sve.c

diff --git a/config/c-compiler.m4 b/config/c-compiler.m4
index 8534cc54c13..c3c2d6fe29d 100644
--- a/config/c-compiler.m4
+++ b/config/c-compiler.m4
@@ -704,3 +704,39 @@ if test x"$Ac_cachevar" = x"yes"; then
 fi
 undefine([Ac_cachevar])dnl
 ])# PGAC_AVX512_POPCNT_INTRINSICS
+
+# PGAC_ARM_SVE_POPCNT_INTRINSICS
+# ------------------------------
+# Check if the compiler supports the ARM SVE popcount instructions using the
+# svdup_u64, svwhilelt_b8, svcntb, svaddv, svadd_x, svcnt_x, svld1,
+# svptrue_b64 and svand_x intrinsic functions.
+#
+# If the intrinsics are supported, sets pgac_arm_sve_popcnt_intrinsics.
+AC_DEFUN([PGAC_ARM_SVE_POPCNT_INTRINSICS],
+[define([Ac_cachevar], [AS_TR_SH([pgac_cv_arm_sve_popcnt_intrinsics])])dnl
+AC_CACHE_CHECK([for svcnt_x and other intrinsics], [Ac_cachevar],
+[AC_LINK_IFELSE([AC_LANG_PROGRAM([#include <arm_sve.h>
+    #if defined(__has_attribute) && __has_attribute(target)
+        __attribute__((target("arch=armv8-a+sve")))
+    #endif
+    static int sve_popcount_test(void)
+    {
+      int popcnt = 0;
+      const char buf@<:@sizeof(uint64_t)@:>@;
+      svbool_t pred8 = svwhilelt_b8(0, 8), pred64 = svptrue_b64();
+      svuint64_t accum = svdup_u64(0), vec;
+      if (svcntb() > 0)
+        popcnt = svaddv(pred8, svcnt_x(pred8, svld1(pred8, (const uint8_t *) buf)));
+      vec = svand_x(pred64, svld1(pred64, (const uint64_t *) buf), 0xf0f0);
+      accum = svadd_x(pred64, accum, svcnt_x(pred64, vec));
+      popcnt += svaddv(pred64, accum);
+      return popcnt;
+    }],
+  [return sve_popcount_test();])],
+  [Ac_cachevar=yes],
+  [Ac_cachevar=no])])
+if test x"$Ac_cachevar" = x"yes"; then
+  pgac_arm_sve_popcnt_intrinsics=yes
+fi
+undefine([Ac_cachevar])dnl
+])# PGAC_ARM_SVE_POPCNT_INTRINSICS
diff --git a/configure b/configure
index 0ffcaeb4367..b227b826092 100755
--- a/configure
+++ b/configure
@@ -17049,6 +17049,62 @@ $as_echo "#define USE_AVX512_POPCNT_WITH_RUNTIME_CHECK 1" >>confdefs.h
   fi
 fi
 
+# Check for ARM SVE popcount intrinsics
+#
+if test x"$host_cpu" = x"aarch64"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for svcnt_x and other intrinsics" >&5
+$as_echo_n "checking for svcnt_x and other intrinsics... " >&6; }
+if ${pgac_cv_arm_sve_popcnt_intrinsics+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+#include <arm_sve.h>
+    #if defined(__has_attribute) && __has_attribute(target)
+        __attribute__((target("arch=armv8-a+sve")))
+    #endif
+    static int sve_popcount_test(void)
+    {
+      int popcnt = 0;
+      const char buf[sizeof(uint64_t)];
+      svbool_t pred8 = svwhilelt_b8(0, 8), pred64 = svptrue_b64();
+      svuint64_t accum = svdup_u64(0), vec;
+      if (svcntb() > 0)
+        popcnt = svaddv(pred8, svcnt_x(pred8, svld1(pred8, (const uint8_t *) buf)));
+      vec = svand_x(pred64, svld1(pred64, (const uint64_t *) buf), 0xf0f0);
+      accum = svadd_x(pred64, accum, svcnt_x(pred64, vec));
+      popcnt += svaddv(pred64, accum);
+      return popcnt;
+    }
+int
+main ()
+{
+return sve_popcount_test();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  pgac_cv_arm_sve_popcnt_intrinsics=yes
+else
+  pgac_cv_arm_sve_popcnt_intrinsics=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_arm_sve_popcnt_intrinsics" >&5
+$as_echo "$pgac_cv_arm_sve_popcnt_intrinsics" >&6; }
+if test x"$pgac_cv_arm_sve_popcnt_intrinsics" = x"yes"; then
+  pgac_arm_sve_popcnt_intrinsics=yes
+fi
+
+  if test x"$pgac_arm_sve_popcnt_intrinsics" = x"yes"; then
+
+$as_echo "#define USE_SVE_POPCNT_WITH_RUNTIME_CHECK 1" >>confdefs.h
+
+  fi
+fi
+
 # Check for Intel SSE 4.2 intrinsics to do CRC calculations.
 #
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for _mm_crc32_u8 and _mm_crc32_u32" >&5
diff --git a/configure.ac b/configure.ac
index f56681e0d91..5c649870550 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2016,6 +2016,15 @@ if test x"$host_cpu" = x"x86_64"; then
   fi
 fi
 
+# Check for ARM SVE popcount intrinsics
+#
+if test x"$host_cpu" = x"aarch64"; then
+  PGAC_ARM_SVE_POPCNT_INTRINSICS()
+  if test x"$pgac_arm_sve_popcnt_intrinsics" = x"yes"; then
+    AC_DEFINE(USE_SVE_POPCNT_WITH_RUNTIME_CHECK, 1, [Define to 1 to use ARM popcount instructions.])
+  fi
+fi
+
 # Check for Intel SSE 4.2 intrinsics to do CRC calculations.
 #
 PGAC_SSE42_CRC32_INTRINSICS()
diff --git a/meson.build b/meson.build
index 7dd7110318d..db3120442b5 100644
--- a/meson.build
+++ b/meson.build
@@ -2195,6 +2195,39 @@ int main(void)
 endif
 
 
+###############################################################
+# Check for the availability of ARM SVE popcount intrinsics.
+###############################################################
+
+if host_cpu == 'aarch64'
+
+  prog = '''
+#include <arm_sve.h>
+#if defined(__has_attribute) && __has_attribute(target)
+    __attribute__((target("arch=armv8-a+sve")))
+#endif
+int main ()
+{
+  int popcnt = 0;
+  const char buf[sizeof(uint64_t)];
+  svbool_t pred8 = svwhilelt_b8(0, 8), pred64 = svptrue_b64();
+  svuint64_t accum = svdup_u64(0), vec;
+  if (svcntb() > 0)
+    popcnt = svaddv(pred8, svcnt_x(pred8, svld1(pred8, (const uint8_t *) buf)));
+  vec = svand_x(pred64, svld1(pred64, (const uint64_t *) buf), 0xf0f0);
+  accum = svadd_x(pred64, accum, svcnt_x(pred64, vec));
+  popcnt += svaddv(pred64, accum);
+  return popcnt;
+}
+'''
+
+  if cc.links(prog, name: 'ARM SVE popcount', args: test_c_args)
+    cdata.set('USE_SVE_POPCNT_WITH_RUNTIME_CHECK', 1)
+  endif
+
+endif
+
+
 ###############################################################
 # Select CRC-32C implementation.
 #
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 07b2f798abd..29c32bbbbe3 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -648,6 +648,9 @@
 /* Define to 1 to use AVX-512 popcount instructions with a runtime check. */
 #undef USE_AVX512_POPCNT_WITH_RUNTIME_CHECK
 
+/* Define to 1 to use SVE popcount instructions with a runtime check. */
+#undef USE_SVE_POPCNT_WITH_RUNTIME_CHECK
+
 /* Define to 1 to build with Bonjour support. (--with-bonjour) */
 #undef USE_BONJOUR
 
diff --git a/src/include/port/pg_bitutils.h b/src/include/port/pg_bitutils.h
index 62554ce685a..b73feb30da5 100644
--- a/src/include/port/pg_bitutils.h
+++ b/src/include/port/pg_bitutils.h
@@ -315,6 +315,19 @@ extern uint64 pg_popcount_avx512(const char *buf, int bytes);
 extern uint64 pg_popcount_masked_avx512(const char *buf, int bytes, bits8 mask);
 #endif
 
+/*
+ * On AArch64, try using SVE popcount instructions, but only if
+ * we can verify that the CPU supports it via a runtime check.
+ */
+#elif USE_SVE_POPCNT_WITH_RUNTIME_CHECK
+extern int	pg_popcount32(uint32 word);
+extern 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);
+extern bool pg_popcount_sve_available(void);
+extern uint64 pg_popcount_sve(const char *buf, int bytes);
+extern uint64 pg_popcount_masked_sve(const char *buf, int bytes, bits8 mask);
+
 #else
 /* Use a portable implementation -- no need for a function pointer. */
 extern int	pg_popcount32(uint32 word);
diff --git a/src/port/Makefile b/src/port/Makefile
index 4c224319512..61a8bcec15c 100644
--- a/src/port/Makefile
+++ b/src/port/Makefile
@@ -45,6 +45,7 @@ OBJS = \
 	path.o \
 	pg_bitutils.o \
 	pg_popcount_avx512.o \
+	pg_popcount_sve.o \
 	pg_strong_random.o \
 	pgcheckdir.o \
 	pgmkdirp.o \
diff --git a/src/port/meson.build b/src/port/meson.build
index 7fcfa728d43..4a3429c21a9 100644
--- a/src/port/meson.build
+++ b/src/port/meson.build
@@ -8,6 +8,7 @@ pgport_sources = [
   'path.c',
   'pg_bitutils.c',
   'pg_popcount_avx512.c',
+  'pg_popcount_sve.c',
   'pg_strong_random.c',
   'pgcheckdir.c',
   'pgmkdirp.c',
diff --git a/src/port/pg_bitutils.c b/src/port/pg_bitutils.c
index 5677525693d..f0d92bf317b 100644
--- a/src/port/pg_bitutils.c
+++ b/src/port/pg_bitutils.c
@@ -339,6 +339,47 @@ pg_popcount_masked_fast(const char *buf, int bytes, bits8 mask)
 
 #endif							/* TRY_POPCNT_FAST */
 
+#ifdef USE_SVE_POPCNT_WITH_RUNTIME_CHECK
+static uint64 pg_popcount_choose_aarch64(const char *buf, int bytes);
+static uint64 pg_popcount_masked_choose_aarch64(const char *buf, int bytes, bits8 mask);
+uint64		(*pg_popcount_optimized) (const char *buf, int bytes) = pg_popcount_choose_aarch64;
+uint64		(*pg_popcount_masked_optimized) (const char *buf, int bytes, bits8 mask) = pg_popcount_masked_choose_aarch64;
+
+/*
+ * On AArch64 these functions are invoked on the first call to pg_popcount and
+ * pg_popcount_masked. They detect whether we can use the SVE implementations,
+ * and replace the function pointers so that subsequent calls are routed
+ * directly to the chosen implementation.
+ */
+static inline void
+choose_popcount_functions_aarch64(void)
+{
+	if (pg_popcount_sve_available())
+	{
+		pg_popcount_optimized = pg_popcount_sve;
+		pg_popcount_masked_optimized = pg_popcount_masked_sve;
+	}
+	else
+	{
+		pg_popcount_optimized = pg_popcount_slow;
+		pg_popcount_masked_optimized = pg_popcount_masked_slow;
+	}
+}
+
+static uint64
+pg_popcount_choose_aarch64(const char *buf, int bytes)
+{
+	choose_popcount_functions_aarch64();
+	return pg_popcount_optimized(buf, bytes);
+}
+
+static uint64
+pg_popcount_masked_choose_aarch64(const char *buf, int bytes, bits8 mask)
+{
+	choose_popcount_functions_aarch64();
+	return pg_popcount_masked(buf, bytes, mask);
+}
+#endif							/* USE_SVE_POPCNT_WITH_RUNTIME_CHECK */
 
 /*
  * pg_popcount32_slow
@@ -507,6 +548,7 @@ pg_popcount64(uint64 word)
 	return pg_popcount64_slow(word);
 }
 
+#ifndef USE_SVE_POPCNT_WITH_RUNTIME_CHECK
 /*
  * pg_popcount_optimized
  *		Returns the number of 1-bits in buf
@@ -526,5 +568,5 @@ pg_popcount_masked_optimized(const char *buf, int bytes, bits8 mask)
 {
 	return pg_popcount_masked_slow(buf, bytes, mask);
 }
-
+#endif							/* !USE_SVE_POPCNT_WITH_RUNTIME_CHECK */
 #endif							/* !TRY_POPCNT_FAST */
diff --git a/src/port/pg_popcount_sve.c b/src/port/pg_popcount_sve.c
new file mode 100644
index 00000000000..060193eec11
--- /dev/null
+++ b/src/port/pg_popcount_sve.c
@@ -0,0 +1,123 @@
+/*-------------------------------------------------------------------------
+ *
+ * pg_popcount_sve.c
+ *	  Holds the SVE pg_popcount() implementation.
+ *
+ * Copyright (c) 2024, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/port/pg_popcount_sve.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "c.h"
+
+#ifdef USE_SVE_POPCNT_WITH_RUNTIME_CHECK
+
+#include "port/pg_bitutils.h"
+#include <arm_sve.h>
+
+#if defined(HAVE_ELF_AUX_INFO) || defined(HAVE_GETAUXVAL)
+#include <sys/auxv.h>
+#endif
+
+/*
+ * Returns true if the CPU supports the instructions required for the SVE
+ * pg_popcount() implementation.
+ */
+bool
+pg_popcount_sve_available(void)
+{
+#if defined(HAVE_ELF_AUX_INFO) && defined(__aarch64__)	/* FreeBSD */
+	unsigned long hwcap;
+	return elf_aux_info(AT_HWCAP, &hwcap, sizeof(hwcap)) == 0 &&
+		(hwcap & HWCAP_SVE) != 0;
+#elif defined(HAVE_GETAUXVAL) && defined(__aarch64__)	/* Linux */
+	return (getauxval(AT_HWCAP) & HWCAP_SVE) != 0;
+#else
+	return false;
+#endif
+}
+
+/*
+ * pg_popcount_sve
+ *		Returns the number of 1-bits in buf
+ */
+pg_attribute_target("arch=armv8-a+sve")
+uint64
+pg_popcount_sve(const char *buf, int bytes)
+{
+	svbool_t    pred = svptrue_b64();
+	svuint64_t  vec64,
+				accum1 = svdup_u64(0),
+				accum2 = svdup_u64(0);
+	uint32		i = 0,
+				vec_len = svcntb(),
+				loop_bytes = bytes & ~(vec_len * 2 - 1);
+	uint64      popcnt = 0;
+
+	/* Process 2 complete vectors */
+	for (; i < loop_bytes; i += vec_len * 2)
+	{
+		vec64 = svld1(pred, (const uint64 *) (buf + i));
+		accum1 = svadd_x(pred, accum1, svcnt_x(pred, vec64));
+		vec64 = svld1(pred, (const uint64 *) (buf + i + vec_len));
+		accum2 = svadd_x(pred, accum2, svcnt_x(pred, vec64));
+	}
+
+	/* Reduce the accumulators */
+	popcnt += svaddv(pred, svadd_x(pred, accum1, accum2));
+
+	/* Process the last incomplete vector  */
+	for(; i < bytes; i += vec_len)
+	{
+		pred = svwhilelt_b8(i, (uint32) bytes);
+		popcnt += svaddv(pred, svcnt_x(pred, svld1(pred, (const uint8 *) (buf + i))));
+	}
+
+	return popcnt;
+}
+
+/*
+ * pg_popcount_masked_sve
+ *		Returns the number of 1-bits in buf after applying the mask
+ */
+pg_attribute_target("arch=armv8-a+sve")
+uint64
+pg_popcount_masked_sve(const char *buf, int bytes, bits8 mask)
+{
+	svbool_t	pred = svptrue_b64();
+	svuint8_t   vec8;
+	svuint64_t  vec64,
+				accum1 = svdup_u64(0),
+				accum2 = svdup_u64(0);
+	uint32		i = 0,
+				vec_len = svcntb(),
+				loop_bytes = bytes & ~(vec_len * 2 - 1);
+	uint64		popcnt = 0,
+				mask64 = ~UINT64CONST(0) / 0xFF * mask;
+
+	/* Process 2 complete vectors */
+	for (; i < loop_bytes; i += vec_len * 2)
+	{
+		vec64 = svand_x(pred, svld1(pred, (const uint64 *) (buf + i)), mask64);
+		accum1 = svadd_x(pred, accum1, svcnt_x(pred, vec64));
+		vec64 = svand_x(pred, svld1(pred, (const uint64 *) (buf + i + vec_len)), mask64);
+		accum2 = svadd_x(pred, accum2, svcnt_x(pred, vec64));
+	}
+
+	/* Reduce the accumulators */
+	popcnt += svaddv(pred, svadd_x(pred, accum1, accum2));
+
+	/* Process the last incomplete vectors */
+	for(; i < bytes; i += vec_len)
+	{
+		pred = svwhilelt_b8(i, (uint32) bytes);
+		vec8 = svand_x(pred, svld1(pred, (const uint8 *) (buf + i)), mask);
+		popcnt += svaddv(pred, svcnt_x(pred, vec8));
+	}
+
+	return popcnt;
+}
+
+#endif							/* USE_SVE_POPCNT_WITH_RUNTIME_CHECK */
-- 
2.34.1