dbs/postgres
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Update configure probes for CFLAGS needed for ARM CRC instructions.

Browse source 
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 f979197eba
commit e266a0ed67
3 changed files with 58 additions and 4 deletions
Download patch file Download diff file Expand all files Collapse all files

7
meson.build
View file

@ -2303,6 +2303,13 @@ 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