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.
regcomp brings in references to wcscoll, which isn't in all the
standards that contain regcomp. In turn, wcscoll brings in references
to wcscmp, also not in all those standards. This patch fixes this by
making those functions into weak aliases of __wcscoll and __wcscmp and
calling those names instead as needed.
Tested for x86_64 and x86 (testsuite, and that disassembly of
installed shared libraries is unchanged by the patch).
[BZ #18497]
* wcsmbs/wcscmp.c [!WCSCMP] (WCSCMP): Define as __wcscmp instead
of wcscmp.
(wcscmp): Define as weak alias of WCSCMP.
* wcsmbs/wcscoll.c (STRCOLL): Define as __wcscoll instead of
wcscoll.
(USE_HIDDEN_DEF): Define.
[!USE_IN_EXTENDED_LOCALE_MODEL] (wcscoll): Define as weak alias of
__wcscoll. Don't use libc_hidden_weak.
* wcsmbs/wcscoll_l.c (STRCMP): Define as __wcscmp instead of
wcscmp.
* sysdeps/i386/i686/multiarch/wcscmp-c.c
[SHARED] (libc_hidden_def): Define __GI___wcscmp instead of
__GI_wcscmp.
(weak_alias): Undefine and redefine.
* sysdeps/i386/i686/multiarch/wcscmp.S (wcscmp): Rename to
__wcscmp and define as weak alias of __wcscmp.
* sysdeps/x86_64/wcscmp.S (wcscmp): Likewise.
* include/wchar.h (__wcscmp): Declare. Use libc_hidden_proto.
(__wcscoll): Likewise.
(wcscmp): Don't use libc_hidden_proto.
(wcscoll): Likewise.
* posix/regcomp.c (build_range_exp): Call __wcscoll instead of
wcscoll.
* posix/regexec.c (check_node_accept_bytes): Likewise.
* conform/Makefile (test-xfail-XPG3/regex.h/linknamespace): Remove
variable.
(test-xfail-XPG4/regex.h/linknamespace): Likewise.
(test-xfail-POSIX/regex.h/linknamespace): Likewise.
Joseph Myers
Paul Eggert
Leonardo Sandoval
Allan McRae
Ulrich Drepper
Liubov Dmitrieva