diff options
Diffstat (limited to 'configure.ac')
| -rw-r--r-- | configure.ac | 19 |
1 files changed, 9 insertions, 10 deletions
diff --git a/configure.ac b/configure.ac index 8c3367bd545..99a5b1aac64 100644 --- a/configure.ac +++ b/configure.ac @@ -2068,13 +2068,7 @@ fi # Check for Intel SSE 4.2 intrinsics to do CRC calculations. # -# First check if the _mm_crc32_u8 and _mm_crc32_u64 intrinsics can be used -# with the default compiler flags. If not, check if adding the -msse4.2 -# flag helps. CFLAGS_CRC is set to -msse4.2 if that's required. -PGAC_SSE42_CRC32_INTRINSICS([]) -if test x"$pgac_sse42_crc32_intrinsics" != x"yes"; then - PGAC_SSE42_CRC32_INTRINSICS([-msse4.2]) -fi +PGAC_SSE42_CRC32_INTRINSICS() # Are we targeting a processor that supports SSE 4.2? gcc, clang and icc all # define __SSE4_2__ in that case. @@ -2111,15 +2105,20 @@ AC_SUBST(CFLAGS_CRC) # If we are targeting a processor that has Intel SSE 4.2 instructions, we can # use the special CRC instructions for calculating CRC-32C. If we're not # targeting such a processor, but we can nevertheless produce code that uses -# the SSE intrinsics, perhaps with some extra CFLAGS, compile both -# implementations and select which one to use at runtime, depending on whether -# SSE 4.2 is supported by the processor we're running on. +# the SSE intrinsics, compile both implementations and select which one to use +# at runtime, depending on whether SSE 4.2 is supported by the processor we're +# running on. # # Similarly, if we are targeting an ARM processor that has the CRC # instructions that are part of the ARMv8 CRC Extension, use them. And if # we're not targeting such a processor, but can nevertheless produce code that # uses the CRC instructions, compile both, and select at runtime. # +# Note that we do not use __attribute__((target("..."))) for the ARM CRC +# instructions because until clang 16, using the ARM intrinsics still requires +# special -march flags. Perhaps we can re-evaluate this decision after some +# time has passed. +# # You can skip the runtime check by setting the appropriate USE_*_CRC32 flag to 1 # in the template or configure command line. # |