This commit refactors `strrchr-evex` and `strrchr-evex512` to use a
common implementation: `strrchr-evex-base.S`.
The motivation is `strrchr-evex` needed to be refactored to not use
64-bit masked registers in preperation for AVX10.
Once vec-width masked register combining was removed, the EVEX and
EVEX512 implementations can easily be implemented in the same file
without any major overhead.
The net result is performance improvements (measured on TGL) for both
`strrchr-evex` and `strrchr-evex512`. Although, note there are some
regressions in the test suite and it may be many of the cases that
make the total-geomean of improvement/regression across bench-strrchr
are cold. The point of the performance measurement is to show there
are no major regressions, but the primary motivation is preperation
for AVX10.
Benchmarks where taken on TGL:
https://www.intel.com/content/www/us/en/products/sku/213799/intel-core-i711850h-processor-24m-cache-up-to-4-80-ghz/specifications.html
EVEX geometric_mean(N=5) of all benchmarks New / Original : 0.74
EVEX512 geometric_mean(N=5) of all benchmarks New / Original: 0.87
Full check passes on x86.
1. Add default ISA level selection in non-multiarch/rtld
implementations.
2. Add ISA level build guards to different implementations.
- I.e strcmp-avx2.S which is ISA level 3 will only build if
compiled ISA level <= 3. Otherwise there is no reason to
include it as we will always use one of the ISA level 4
implementations (strcmp-evex.S).
3. Refactor the ifunc selector and ifunc implementation list to use
the ISA level aware wrapper macros that allow functions below the
compiled ISA level (with a guranteed replacement) to be skipped.
Tested with and without multiarch on x86_64 for ISA levels:
{generic, x86-64-v2, x86-64-v3, x86-64-v4}
And m32 with and without multiarch.
Update ifunc-avx2.h, strchr.c, strcmp.c, strncmp.c and wcsnlen.c to
select the function optimized with 256-bit EVEX instructions using
YMM16-YMM31 registers to avoid RTM abort with usable AVX512VL, AVX512BW
and BMI2 since VZEROUPPER isn't needed at function exit.
For strcmp/strncmp, prefer AVX2 strcmp/strncmp if Prefer_AVX2_STRCMP
is set.
