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Update configure probes for CFLAGS needed for ARM CRC instructions.

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On ARM platforms where the baseline CPU target lacks CRC instructions,
we need to supply a -march flag to persuade the compiler to compile
such instructions.  It turns out that our existing choice of
"-march=armv8-a+crc" has not worked for some time, because recent gcc
will interpret that as selecting software floating point, and then
will spit up if the platform requires hard-float ABI, as most do
nowadays.  The end result was to silently fall back to software CRC,
which isn't very desirable since in practice almost all currently
produced ARM chips do have hardware CRC.

We can fix this by using "-march=armv8-a+crc+simd" to enable the
correct ABI choice.  (This has no impact on the code actually
generated, since neither of the files we compile with this flag
does any floating-point stuff, let alone SIMD.)  Keep the test for
"-march=armv8-a+crc" since that's required for soft-float ABI,
but try that second since most platforms we're likely to build on
use hard-float.

Since this isn't working as-intended on the last several years'
worth of gcc releases, back-patch to all supported branches.

Discussion: https://postgr.es/m/4496616.iHFcN1HehY@portable-bastien
This commit is contained in:
Tom Lane 2024-11-25 12:50:17 -05:00
parent 4570b22666
commit 5980f1884f
3 changed files with 58 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

47
configure vendored
View File

@ -17482,7 +17482,8 @@ rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
# Check for ARMv8 CRC Extension intrinsics to do CRC calculations.
#
# First check if __crc32c* intrinsics can be used with the default compiler
# flags. If not, check if adding -march=armv8-a+crc flag helps.
# flags. If not, check if adding "-march=armv8-a+crc+simd" flag helps.
# On systems using soft-float ABI, "-march=armv8-a+crc" is required instead.
# CFLAGS_CRC is set if the extra flag is required.
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for __crc32cb, __crc32ch, __crc32cw, and __crc32cd with CFLAGS=" >&5
$as_echo_n "checking for __crc32cb, __crc32ch, __crc32cw, and __crc32cd with CFLAGS=... " >&6; }
@ -17525,7 +17526,48 @@ if test x"$pgac_cv_armv8_crc32c_intrinsics_" = x"yes"; then
fi
if test x"$pgac_armv8_crc32c_intrinsics" != x"yes"; then
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for __crc32cb, __crc32ch, __crc32cw, and __crc32cd with CFLAGS=-march=armv8-a+crc" >&5
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for __crc32cb, __crc32ch, __crc32cw, and __crc32cd with CFLAGS=-march=armv8-a+crc+simd" >&5
$as_echo_n "checking for __crc32cb, __crc32ch, __crc32cw, and __crc32cd with CFLAGS=-march=armv8-a+crc+simd... " >&6; }
if ${pgac_cv_armv8_crc32c_intrinsics__march_armv8_apcrcpsimd+:} false; then :
$as_echo_n "(cached) " >&6
else
pgac_save_CFLAGS=$CFLAGS
CFLAGS="$pgac_save_CFLAGS -march=armv8-a+crc+simd"
cat confdefs.h - <<_ACEOF >conftest.$ac_ext
/* end confdefs.h. */
#include <arm_acle.h>
int
main ()
{
unsigned int crc = 0;
crc = __crc32cb(crc, 0);
crc = __crc32ch(crc, 0);
crc = __crc32cw(crc, 0);
crc = __crc32cd(crc, 0);
/* return computed value, to prevent the above being optimized away */
return crc == 0;
;
return 0;
}
_ACEOF
if ac_fn_c_try_link "$LINENO"; then :
pgac_cv_armv8_crc32c_intrinsics__march_armv8_apcrcpsimd=yes
else
pgac_cv_armv8_crc32c_intrinsics__march_armv8_apcrcpsimd=no
fi
rm -f core conftest.err conftest.$ac_objext \
conftest$ac_exeext conftest.$ac_ext
CFLAGS="$pgac_save_CFLAGS"
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_armv8_crc32c_intrinsics__march_armv8_apcrcpsimd" >&5
$as_echo "$pgac_cv_armv8_crc32c_intrinsics__march_armv8_apcrcpsimd" >&6; }
if test x"$pgac_cv_armv8_crc32c_intrinsics__march_armv8_apcrcpsimd" = x"yes"; then
CFLAGS_CRC="-march=armv8-a+crc+simd"
pgac_armv8_crc32c_intrinsics=yes
fi
if test x"$pgac_armv8_crc32c_intrinsics" != x"yes"; then
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for __crc32cb, __crc32ch, __crc32cw, and __crc32cd with CFLAGS=-march=armv8-a+crc" >&5
$as_echo_n "checking for __crc32cb, __crc32ch, __crc32cw, and __crc32cd with CFLAGS=-march=armv8-a+crc... " >&6; }
if ${pgac_cv_armv8_crc32c_intrinsics__march_armv8_apcrc+:} false; then :
$as_echo_n "(cached) " >&6
@ -17565,6 +17607,7 @@ if test x"$pgac_cv_armv8_crc32c_intrinsics__march_armv8_apcrc" = x"yes"; then
pgac_armv8_crc32c_intrinsics=yes
fi
fi
fi
# Check for LoongArch CRC intrinsics to do CRC calculations.

8
configure.ac
View File

@ -2088,11 +2088,15 @@ AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [
# Check for ARMv8 CRC Extension intrinsics to do CRC calculations.
#
# First check if __crc32c* intrinsics can be used with the default compiler
# flags. If not, check if adding -march=armv8-a+crc flag helps.
# flags. If not, check if adding "-march=armv8-a+crc+simd" flag helps.
# On systems using soft-float ABI, "-march=armv8-a+crc" is required instead.
# CFLAGS_CRC is set if the extra flag is required.
PGAC_ARMV8_CRC32C_INTRINSICS([])
if test x"$pgac_armv8_crc32c_intrinsics" != x"yes"; then
PGAC_ARMV8_CRC32C_INTRINSICS([-march=armv8-a+crc])
PGAC_ARMV8_CRC32C_INTRINSICS([-march=armv8-a+crc+simd])
if test x"$pgac_armv8_crc32c_intrinsics" != x"yes"; then
PGAC_ARMV8_CRC32C_INTRINSICS([-march=armv8-a+crc])
fi
fi
# Check for LoongArch CRC intrinsics to do CRC calculations.

7
meson.build
View File

@ -2284,6 +2284,13 @@ int main(void)
# Use ARM CRC Extension unconditionally
cdata.set('USE_ARMV8_CRC32C', 1)
have_optimized_crc = true
elif cc.links(prog, name: '__crc32cb, __crc32ch, __crc32cw, and __crc32cd with -march=armv8-a+crc+simd',
args: test_c_args + ['-march=armv8-a+crc+simd'])
# Use ARM CRC Extension, with runtime check
cflags_crc += '-march=armv8-a+crc+simd'
cdata.set('USE_ARMV8_CRC32C', false)
cdata.set('USE_ARMV8_CRC32C_WITH_RUNTIME_CHECK', 1)
have_optimized_crc = true
elif cc.links(prog, name: '__crc32cb, __crc32ch, __crc32cw, and __crc32cd with -march=armv8-a+crc',
args: test_c_args + ['-march=armv8-a+crc'])
# Use ARM CRC Extension, with runtime check