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| author | Raghuveer Devulapalli <raghuveer.devulapalli@intel.com> | 2022-06-06 12:17:43 -0700 |
|---|---|---|
| committer | H.J. Lu <hjl.tools@gmail.com> | 2022-06-06 19:46:55 -0700 |
| commit | 5082a287d5e9a1f9cb98b7c982a708a3684f1d5c (patch) | |
| tree | 7fd99341b565ce257383a603daedcc9e019e2230 /sysdeps/x86_64/multiarch/ifunc-impl-list.c | |
| parent | 8521001731d6539382fa875f1cac9864c466ef27 (diff) | |
| download | glibc-5082a287d5e9a1f9cb98b7c982a708a3684f1d5c.tar.gz glibc-5082a287d5e9a1f9cb98b7c982a708a3684f1d5c.tar.xz glibc-5082a287d5e9a1f9cb98b7c982a708a3684f1d5c.zip | |
x86_64: Add strstr function with 512-bit EVEX
Adding a 512-bit EVEX version of strstr. The algorithm works as follows: (1) We spend a few cycles at the begining to peek into the needle. We locate an edge in the needle (first occurance of 2 consequent distinct characters) and also store the first 64-bytes into a zmm register. (2) We search for the edge in the haystack by looking into one cache line of the haystack at a time. This avoids having to read past a page boundary which can cause a seg fault. (3) If an edge is found in the haystack we first compare the first 64-bytes of the needle (already stored in a zmm register) before we proceed with a full string compare performed byte by byte. Benchmarking results: (old = strstr_sse2_unaligned, new = strstr_avx512) Geometric mean of all benchmarks: new / old = 0.66 Difficult skiptable(0) : new / old = 0.02 Difficult skiptable(1) : new / old = 0.01 Difficult 2-way : new / old = 0.25 Difficult testing first 2 : new / old = 1.26 Difficult skiptable(0) : new / old = 0.05 Difficult skiptable(1) : new / old = 0.06 Difficult 2-way : new / old = 0.26 Difficult testing first 2 : new / old = 1.05 Difficult skiptable(0) : new / old = 0.42 Difficult skiptable(1) : new / old = 0.24 Difficult 2-way : new / old = 0.21 Difficult testing first 2 : new / old = 1.04 Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
Diffstat (limited to 'sysdeps/x86_64/multiarch/ifunc-impl-list.c')
| -rw-r--r-- | sysdeps/x86_64/multiarch/ifunc-impl-list.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/sysdeps/x86_64/multiarch/ifunc-impl-list.c b/sysdeps/x86_64/multiarch/ifunc-impl-list.c index c5cd9466fe..58f3ec8306 100644 --- a/sysdeps/x86_64/multiarch/ifunc-impl-list.c +++ b/sysdeps/x86_64/multiarch/ifunc-impl-list.c @@ -618,6 +618,12 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array, /* Support sysdeps/x86_64/multiarch/strstr.c. */ IFUNC_IMPL (i, name, strstr, + IFUNC_IMPL_ADD (array, i, strstr, + (CPU_FEATURE_USABLE (AVX512VL) + && CPU_FEATURE_USABLE (AVX512BW) + && CPU_FEATURE_USABLE (AVX512DQ) + && CPU_FEATURE_USABLE (BMI2)), + __strstr_avx512) IFUNC_IMPL_ADD (array, i, strstr, 1, __strstr_sse2_unaligned) IFUNC_IMPL_ADD (array, i, strstr, 1, __strstr_sse2)) |