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authorLeonardo Sandoval <leonardo.sandoval.gonzalez@linux.intel.com>2018-05-03 11:09:30 -0500
committerLeonardo Sandoval <leonardo.sandoval.gonzalez@linux.intel.com>2018-06-01 16:32:43 -0500
commit1457016337072d1b6739f571846b619596990cb7 (patch)
tree985983beef1070b9e01f6f31ad974f5038278799 /benchtests/scripts/compare_strings.py
parente02c026f38505cd474ff1bdaa88fc671804f5805 (diff)
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x86-64: Optimize strcmp/wcscmp and strncmp/wcsncmp with AVX2
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.
Diffstat (limited to 'benchtests/scripts/compare_strings.py')
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