[PATCH v1 18/23] x86: Optimize str{n}casecmp TOLOWER logic in strcmp-sse42.S
Sunil Pandey
skpgkp2@gmail.com
Thu May 12 19:45:08 GMT 2022
On Thu, Mar 24, 2022 at 12:05 PM H.J. Lu via Libc-alpha
<libc-alpha@sourceware.org> wrote:
>
> On Wed, Mar 23, 2022 at 3:02 PM Noah Goldstein <goldstein.w.n@gmail.com> wrote:
> >
> > Slightly faster method of doing TOLOWER that saves an
> > instruction.
> >
> > Also replace the hard coded 5-byte no with .p2align 4. On builds with
> > CET enabled this misaligned entry to strcasecmp.
> >
> > geometric_mean(N=40) of all benchmarks New / Original: .920
> >
> > All string/memory tests pass.
> > ---
> > Geomtric Mean N=40 runs; All functions page aligned
> > length, align1, align2, max_char, New Time / Old Time
> > 1, 1, 1, 127, 0.914
> > 2, 2, 2, 127, 0.952
> > 3, 3, 3, 127, 0.924
> > 4, 4, 4, 127, 0.995
> > 5, 5, 5, 127, 0.985
> > 6, 6, 6, 127, 1.017
> > 7, 7, 7, 127, 1.031
> > 8, 0, 0, 127, 0.967
> > 9, 1, 1, 127, 0.969
> > 10, 2, 2, 127, 0.951
> > 11, 3, 3, 127, 0.938
> > 12, 4, 4, 127, 0.937
> > 13, 5, 5, 127, 0.967
> > 14, 6, 6, 127, 0.941
> > 15, 7, 7, 127, 0.951
> > 4, 0, 0, 127, 0.959
> > 4, 0, 0, 254, 0.98
> > 8, 0, 0, 254, 0.959
> > 16, 0, 0, 127, 0.895
> > 16, 0, 0, 254, 0.901
> > 32, 0, 0, 127, 0.85
> > 32, 0, 0, 254, 0.851
> > 64, 0, 0, 127, 0.897
> > 64, 0, 0, 254, 0.895
> > 128, 0, 0, 127, 0.944
> > 128, 0, 0, 254, 0.935
> > 256, 0, 0, 127, 0.922
> > 256, 0, 0, 254, 0.913
> > 512, 0, 0, 127, 0.921
> > 512, 0, 0, 254, 0.914
> > 1024, 0, 0, 127, 0.845
> > 1024, 0, 0, 254, 0.84
> > 16, 1, 2, 127, 0.923
> > 16, 2, 1, 254, 0.955
> > 32, 2, 4, 127, 0.979
> > 32, 4, 2, 254, 0.957
> > 64, 3, 6, 127, 0.866
> > 64, 6, 3, 254, 0.849
> > 128, 4, 0, 127, 0.882
> > 128, 0, 4, 254, 0.876
> > 256, 5, 2, 127, 0.877
> > 256, 2, 5, 254, 0.882
> > 512, 6, 4, 127, 0.822
> > 512, 4, 6, 254, 0.862
> > 1024, 7, 6, 127, 0.903
> > 1024, 6, 7, 254, 0.908
> >
> > sysdeps/x86_64/multiarch/strcmp-sse42.S | 83 +++++++++++--------------
> > 1 file changed, 35 insertions(+), 48 deletions(-)
> >
> > diff --git a/sysdeps/x86_64/multiarch/strcmp-sse42.S b/sysdeps/x86_64/multiarch/strcmp-sse42.S
> > index 580feb90e9..7805ae9d41 100644
> > --- a/sysdeps/x86_64/multiarch/strcmp-sse42.S
> > +++ b/sysdeps/x86_64/multiarch/strcmp-sse42.S
> > @@ -88,9 +88,8 @@ ENTRY (GLABEL(__strcasecmp))
> > movq __libc_tsd_LOCALE@gottpoff(%rip),%rax
> > mov %fs:(%rax),%RDX_LP
> >
> > - // XXX 5 byte should be before the function
> > - /* 5-byte NOP. */
> > - .byte 0x0f,0x1f,0x44,0x00,0x00
> > + /* Either 1 or 5 bytes (dependeing if CET is enabled). */
> > + .p2align 4
> > END (GLABEL(__strcasecmp))
> > /* FALLTHROUGH to strcasecmp_l. */
> > #endif
> > @@ -99,9 +98,8 @@ ENTRY (GLABEL(__strncasecmp))
> > movq __libc_tsd_LOCALE@gottpoff(%rip),%rax
> > mov %fs:(%rax),%RCX_LP
> >
> > - // XXX 5 byte should be before the function
> > - /* 5-byte NOP. */
> > - .byte 0x0f,0x1f,0x44,0x00,0x00
> > + /* Either 1 or 5 bytes (dependeing if CET is enabled). */
> > + .p2align 4
> > END (GLABEL(__strncasecmp))
> > /* FALLTHROUGH to strncasecmp_l. */
> > #endif
> > @@ -169,27 +167,22 @@ STRCMP_SSE42:
> > #if defined USE_AS_STRCASECMP_L || defined USE_AS_STRNCASECMP_L
> > .section .rodata.cst16,"aM",@progbits,16
> > .align 16
> > -LABEL(belowupper):
> > - .quad 0x4040404040404040
> > - .quad 0x4040404040404040
> > -LABEL(topupper):
> > -# ifdef USE_AVX
> > - .quad 0x5a5a5a5a5a5a5a5a
> > - .quad 0x5a5a5a5a5a5a5a5a
> > -# else
> > - .quad 0x5b5b5b5b5b5b5b5b
> > - .quad 0x5b5b5b5b5b5b5b5b
> > -# endif
> > -LABEL(touppermask):
> > +LABEL(lcase_min):
> > + .quad 0x3f3f3f3f3f3f3f3f
> > + .quad 0x3f3f3f3f3f3f3f3f
> > +LABEL(lcase_max):
> > + .quad 0x9999999999999999
> > + .quad 0x9999999999999999
> > +LABEL(case_add):
> > .quad 0x2020202020202020
> > .quad 0x2020202020202020
> > .previous
> > - movdqa LABEL(belowupper)(%rip), %xmm4
> > -# define UCLOW_reg %xmm4
> > - movdqa LABEL(topupper)(%rip), %xmm5
> > -# define UCHIGH_reg %xmm5
> > - movdqa LABEL(touppermask)(%rip), %xmm6
> > -# define LCQWORD_reg %xmm6
> > + movdqa LABEL(lcase_min)(%rip), %xmm4
> > +# define LCASE_MIN_reg %xmm4
> > + movdqa LABEL(lcase_max)(%rip), %xmm5
> > +# define LCASE_MAX_reg %xmm5
> > + movdqa LABEL(case_add)(%rip), %xmm6
> > +# define CASE_ADD_reg %xmm6
> > #endif
> > cmp $0x30, %ecx
> > ja LABEL(crosscache)/* rsi: 16-byte load will cross cache line */
> > @@ -200,32 +193,26 @@ LABEL(touppermask):
> > #if defined USE_AS_STRCASECMP_L || defined USE_AS_STRNCASECMP_L
> > # ifdef USE_AVX
> > # define TOLOWER(reg1, reg2) \
> > - vpcmpgtb UCLOW_reg, reg1, %xmm7; \
> > - vpcmpgtb UCHIGH_reg, reg1, %xmm8; \
> > - vpcmpgtb UCLOW_reg, reg2, %xmm9; \
> > - vpcmpgtb UCHIGH_reg, reg2, %xmm10; \
> > - vpandn %xmm7, %xmm8, %xmm8; \
> > - vpandn %xmm9, %xmm10, %xmm10; \
> > - vpand LCQWORD_reg, %xmm8, %xmm8; \
> > - vpand LCQWORD_reg, %xmm10, %xmm10; \
> > - vpor reg1, %xmm8, reg1; \
> > - vpor reg2, %xmm10, reg2
> > + vpaddb LCASE_MIN_reg, reg1, %xmm7; \
> > + vpaddb LCASE_MIN_reg, reg2, %xmm8; \
> > + vpcmpgtb LCASE_MAX_reg, %xmm7, %xmm7; \
> > + vpcmpgtb LCASE_MAX_reg, %xmm8, %xmm8; \
> > + vpandn CASE_ADD_reg, %xmm7, %xmm7; \
> > + vpandn CASE_ADD_reg, %xmm8, %xmm8; \
> > + vpaddb %xmm7, reg1, reg1; \
> > + vpaddb %xmm8, reg2, reg2
> > # else
> > # define TOLOWER(reg1, reg2) \
> > - movdqa reg1, %xmm7; \
> > - movdqa UCHIGH_reg, %xmm8; \
> > - movdqa reg2, %xmm9; \
> > - movdqa UCHIGH_reg, %xmm10; \
> > - pcmpgtb UCLOW_reg, %xmm7; \
> > - pcmpgtb reg1, %xmm8; \
> > - pcmpgtb UCLOW_reg, %xmm9; \
> > - pcmpgtb reg2, %xmm10; \
> > - pand %xmm8, %xmm7; \
> > - pand %xmm10, %xmm9; \
> > - pand LCQWORD_reg, %xmm7; \
> > - pand LCQWORD_reg, %xmm9; \
> > - por %xmm7, reg1; \
> > - por %xmm9, reg2
> > + movdqa LCASE_MIN_reg, %xmm7; \
> > + movdqa LCASE_MIN_reg, %xmm8; \
> > + paddb reg1, %xmm7; \
> > + paddb reg2, %xmm8; \
> > + pcmpgtb LCASE_MAX_reg, %xmm7; \
> > + pcmpgtb LCASE_MAX_reg, %xmm8; \
> > + pandn CASE_ADD_reg, %xmm7; \
> > + pandn CASE_ADD_reg, %xmm8; \
> > + paddb %xmm7, reg1; \
> > + paddb %xmm8, reg2
> > # endif
> > TOLOWER (%xmm1, %xmm2)
> > #else
> > --
> > 2.25.1
> >
>
> LGTM.
>
> Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
>
> Thanks.
>
> --
> H.J.
I would like to backport this patch to release branches.
Any comments or objections?
--Sunil
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