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help / color / mirror / Atom feedFrom: Nathan Bossart <nathan@postgresql.org>
Subject: [PATCH v11 4/4] Remove uses of popcount builtins.
Date: Fri, 6 Feb 2026 10:00:21 -0600
---
configure | 38 ----------------------------------
configure.ac | 1 -
meson.build | 1 -
src/include/pg_config.h.in | 3 ---
src/include/port/pg_bitutils.h | 17 +--------------
src/port/pg_popcount_aarch64.c | 5 -----
6 files changed, 1 insertion(+), 64 deletions(-)
diff --git a/configure b/configure
index ba293931878..623aa397fae 100755
--- a/configure
+++ b/configure
@@ -15920,44 +15920,6 @@ cat >>confdefs.h <<_ACEOF
#define HAVE__BUILTIN_CTZ 1
_ACEOF
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for __builtin_popcount" >&5
-$as_echo_n "checking for __builtin_popcount... " >&6; }
-if ${pgac_cv__builtin_popcount+:} false; then :
- $as_echo_n "(cached) " >&6
-else
- cat confdefs.h - <<_ACEOF >conftest.$ac_ext
-/* end confdefs.h. */
-
-int
-call__builtin_popcount(unsigned int x)
-{
- return __builtin_popcount(x);
-}
-int
-main ()
-{
-
- ;
- return 0;
-}
-_ACEOF
-if ac_fn_c_try_link "$LINENO"; then :
- pgac_cv__builtin_popcount=yes
-else
- pgac_cv__builtin_popcount=no
-fi
-rm -f core conftest.err conftest.$ac_objext \
- conftest$ac_exeext conftest.$ac_ext
-fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv__builtin_popcount" >&5
-$as_echo "$pgac_cv__builtin_popcount" >&6; }
-if test x"${pgac_cv__builtin_popcount}" = xyes ; then
-
-cat >>confdefs.h <<_ACEOF
-#define HAVE__BUILTIN_POPCOUNT 1
-_ACEOF
-
fi
# __builtin_frame_address may draw a diagnostic for non-constant argument,
# so it needs a different test function.
diff --git a/configure.ac b/configure.ac
index 412fe358a2f..04c6a75bff7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1853,7 +1853,6 @@ PGAC_CHECK_BUILTIN_FUNC([__builtin_bswap64], [long int x])
# We assume that we needn't test all widths of these explicitly:
PGAC_CHECK_BUILTIN_FUNC([__builtin_clz], [unsigned int x])
PGAC_CHECK_BUILTIN_FUNC([__builtin_ctz], [unsigned int x])
-PGAC_CHECK_BUILTIN_FUNC([__builtin_popcount], [unsigned int x])
# __builtin_frame_address may draw a diagnostic for non-constant argument,
# so it needs a different test function.
PGAC_CHECK_BUILTIN_FUNC_PTR([__builtin_frame_address], [0])
diff --git a/meson.build b/meson.build
index 0722b16927e..c607d8ac69a 100644
--- a/meson.build
+++ b/meson.build
@@ -2004,7 +2004,6 @@ builtins = [
'ctz',
'constant_p',
'frame_address',
- 'popcount',
'unreachable',
]
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index c089f2252c3..301328b8cd3 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -530,9 +530,6 @@
/* Define to 1 if your compiler understands __builtin_$op_overflow. */
#undef HAVE__BUILTIN_OP_OVERFLOW
-/* Define to 1 if your compiler understands __builtin_popcount. */
-#undef HAVE__BUILTIN_POPCOUNT
-
/* Define to 1 if your compiler understands __builtin_types_compatible_p. */
#undef HAVE__BUILTIN_TYPES_COMPATIBLE_P
diff --git a/src/include/port/pg_bitutils.h b/src/include/port/pg_bitutils.h
index 3c58f6c6864..c9b1f5f17dc 100644
--- a/src/include/port/pg_bitutils.h
+++ b/src/include/port/pg_bitutils.h
@@ -313,32 +313,17 @@ pg_popcount32(uint32 word)
* pg_popcount64
* Return the number of 1 bits set in word
*
- * Plain C version adapted from
+ * Adapted from
* https://graphics.stanford.edu/~seander/bithacks.html#CountBitsSetParallel.
*/
static inline int
pg_popcount64(uint64 word)
{
- /*
- * On x86, gcc generates a function call for this built-in unless the
- * popcnt instruction is available, so we use the plain C version in that
- * case to ensure inlining.
- */
-#if defined(HAVE__BUILTIN_POPCOUNT) && (defined(__POPCNT__) || !defined(__x86_64__))
-#if SIZEOF_LONG == 8
- return __builtin_popcountl(word);
-#elif SIZEOF_LONG_LONG == 8
- return __builtin_popcountll(word);
-#else
-#error "cannot find integer of the same size as uint64_t"
-#endif
-#else
word -= (word >> 1) & UINT64CONST(0x5555555555555555);
word = (word & UINT64CONST(0x3333333333333333)) +
((word >> 2) & UINT64CONST(0x3333333333333333));
word = (word + (word >> 4)) & UINT64CONST(0xf0f0f0f0f0f0f0f);
return (word * UINT64CONST(0x101010101010101)) >> 56;
-#endif
}
/*
diff --git a/src/port/pg_popcount_aarch64.c b/src/port/pg_popcount_aarch64.c
index f474ef45510..b0f10ae07a4 100644
--- a/src/port/pg_popcount_aarch64.c
+++ b/src/port/pg_popcount_aarch64.c
@@ -298,11 +298,6 @@ pg_popcount_masked_optimized(const char *buf, int bytes, bits8 mask)
static inline int
pg_popcount64_neon(uint64 word)
{
- /*
- * For some compilers, __builtin_popcountl() already emits Neon
- * instructions. The line below should compile to the same code on those
- * systems.
- */
return vaddv_u8(vcnt_u8(vld1_u8((const uint8 *) &word)));
}
--
2.50.1 (Apple Git-155)
--mih0IfQp6StcW7xc--
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Subject: Re: [PATCH v11 4/4] Remove uses of popcount builtins.
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