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Optimize x86-64 strcmp/wcscmp and strncmp/wcsncmp with AVX2. It uses vector comparison as much as possible. Peak performance observed on a SkyLake machine: 9x, 3x, 2.5x and 5.5x for strcmp, strncmp, wcscmp and wcsncmp, respectively. The larger the comparison length, the more benefit using avx2 functions, except on the strcmp, where peak is observed at length == 32 bytes. Select AVX2 strcmp/wcscmp on AVX2 machines where vzeroupper is preferred and AVX unaligned load is fast. NB: It uses TZCNT instead of BSF since TZCNT produces the same result as BSF for non-zero input. TZCNT is faster than BSF and is executed as BSF if machine doesn't support TZCNT. * sysdeps/x86_64/multiarch/Makefile (sysdep_routines): Add strcmp-avx2, strncmp-avx2, wcscmp-avx2, wcscmp-sse2, wcsncmp-avx2 and wcsncmp-sse2. * sysdeps/x86_64/multiarch/ifunc-impl-list.c (__libc_ifunc_impl_list): Add tests for __strcmp_avx2, __strncmp_avx2, __wcscmp_avx2, __wcsncmp_avx2, __wcscmp_sse2 and __wcsncmp_sse2. * sysdeps/x86_64/multiarch/strcmp.c (OPTIMIZE (avx2)): (IFUNC_SELECTOR): Return OPTIMIZE (avx2) on AVX 2 machines if AVX unaligned load is fast and vzeroupper is preferred. * sysdeps/x86_64/multiarch/strncmp.c: Likewise. * sysdeps/x86_64/multiarch/strcmp-avx2.S: New file. * sysdeps/x86_64/multiarch/strncmp-avx2.S: Likewise. * sysdeps/x86_64/multiarch/wcscmp-avx2.S: Likewise. * sysdeps/x86_64/multiarch/wcscmp-sse2.S: Likewise. * sysdeps/x86_64/multiarch/wcscmp.c: Likewise. * sysdeps/x86_64/multiarch/wcsncmp-avx2.S: Likewise. * sysdeps/x86_64/multiarch/wcsncmp-sse2.c: Likewise. * sysdeps/x86_64/multiarch/wcsncmp.c: Likewise. * sysdeps/x86_64/wcscmp.S (__wcscmp): Add alias only if __wcscmp is undefined.
5 lines
79 B
ArmAsm
5 lines
79 B
ArmAsm
#define STRCMP __wcscmp_avx2
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#define USE_AS_WCSCMP 1
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#include "strcmp-avx2.S"
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