[PATCH v1 17/23] x86: Optimize str{n}casecmp TOLOWER logic in strcmp.S
Sunil Pandey
skpgkp2@gmail.com
Thu May 12 19:44:13 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 3:01 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: .894
> >
> > 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, 0.903
> > 2, 2, 2, 127, 0.905
> > 3, 3, 3, 127, 0.877
> > 4, 4, 4, 127, 0.888
> > 5, 5, 5, 127, 0.901
> > 6, 6, 6, 127, 0.954
> > 7, 7, 7, 127, 0.932
> > 8, 0, 0, 127, 0.918
> > 9, 1, 1, 127, 0.914
> > 10, 2, 2, 127, 0.877
> > 11, 3, 3, 127, 0.909
> > 12, 4, 4, 127, 0.876
> > 13, 5, 5, 127, 0.886
> > 14, 6, 6, 127, 0.914
> > 15, 7, 7, 127, 0.939
> > 4, 0, 0, 127, 0.963
> > 4, 0, 0, 254, 0.943
> > 8, 0, 0, 254, 0.927
> > 16, 0, 0, 127, 0.876
> > 16, 0, 0, 254, 0.865
> > 32, 0, 0, 127, 0.865
> > 32, 0, 0, 254, 0.862
> > 64, 0, 0, 127, 0.863
> > 64, 0, 0, 254, 0.896
> > 128, 0, 0, 127, 0.885
> > 128, 0, 0, 254, 0.882
> > 256, 0, 0, 127, 0.87
> > 256, 0, 0, 254, 0.869
> > 512, 0, 0, 127, 0.832
> > 512, 0, 0, 254, 0.848
> > 1024, 0, 0, 127, 0.835
> > 1024, 0, 0, 254, 0.843
> > 16, 1, 2, 127, 0.914
> > 16, 2, 1, 254, 0.949
> > 32, 2, 4, 127, 0.955
> > 32, 4, 2, 254, 1.004
> > 64, 3, 6, 127, 0.844
> > 64, 6, 3, 254, 0.905
> > 128, 4, 0, 127, 0.889
> > 128, 0, 4, 254, 0.845
> > 256, 5, 2, 127, 0.929
> > 256, 2, 5, 254, 0.907
> > 512, 6, 4, 127, 0.837
> > 512, 4, 6, 254, 0.862
> > 1024, 7, 6, 127, 0.895
> > 1024, 6, 7, 254, 0.89
> >
> > sysdeps/x86_64/strcmp.S | 64 +++++++++++++++++++----------------------
> > 1 file changed, 29 insertions(+), 35 deletions(-)
> >
> > diff --git a/sysdeps/x86_64/strcmp.S b/sysdeps/x86_64/strcmp.S
> > index e2ab59c555..99d8b36f1d 100644
> > --- a/sysdeps/x86_64/strcmp.S
> > +++ b/sysdeps/x86_64/strcmp.S
> > @@ -75,9 +75,8 @@ ENTRY2 (__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
> > END2 (__strcasecmp)
> > # ifndef NO_NOLOCALE_ALIAS
> > weak_alias (__strcasecmp, strcasecmp)
> > @@ -94,9 +93,8 @@ ENTRY2 (__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
> > END2 (__strncasecmp)
> > # ifndef NO_NOLOCALE_ALIAS
> > weak_alias (__strncasecmp, strncasecmp)
> > @@ -146,22 +144,22 @@ ENTRY (STRCMP)
> > #if defined USE_AS_STRCASECMP_L || defined USE_AS_STRNCASECMP_L
> > .section .rodata.cst16,"aM",@progbits,16
> > .align 16
> > -.Lbelowupper:
> > - .quad 0x4040404040404040
> > - .quad 0x4040404040404040
> > -.Ltopupper:
> > - .quad 0x5b5b5b5b5b5b5b5b
> > - .quad 0x5b5b5b5b5b5b5b5b
> > -.Ltouppermask:
> > +.Llcase_min:
> > + .quad 0x3f3f3f3f3f3f3f3f
> > + .quad 0x3f3f3f3f3f3f3f3f
> > +.Llcase_max:
> > + .quad 0x9999999999999999
> > + .quad 0x9999999999999999
> > +.Lcase_add:
> > .quad 0x2020202020202020
> > .quad 0x2020202020202020
> > .previous
> > - movdqa .Lbelowupper(%rip), %xmm5
> > -# define UCLOW_reg %xmm5
> > - movdqa .Ltopupper(%rip), %xmm6
> > -# define UCHIGH_reg %xmm6
> > - movdqa .Ltouppermask(%rip), %xmm7
> > -# define LCQWORD_reg %xmm7
> > + movdqa .Llcase_min(%rip), %xmm5
> > +# define LCASE_MIN_reg %xmm5
> > + movdqa .Llcase_max(%rip), %xmm6
> > +# define LCASE_MAX_reg %xmm6
> > + movdqa .Lcase_add(%rip), %xmm7
> > +# define CASE_ADD_reg %xmm7
> > #endif
> > cmp $0x30, %ecx
> > ja LABEL(crosscache) /* rsi: 16-byte load will cross cache line */
> > @@ -172,22 +170,18 @@ ENTRY (STRCMP)
> > movhpd 8(%rdi), %xmm1
> > movhpd 8(%rsi), %xmm2
> > #if defined USE_AS_STRCASECMP_L || defined USE_AS_STRNCASECMP_L
> > -# define TOLOWER(reg1, reg2) \
> > - movdqa reg1, %xmm8; \
> > - movdqa UCHIGH_reg, %xmm9; \
> > - movdqa reg2, %xmm10; \
> > - movdqa UCHIGH_reg, %xmm11; \
> > - pcmpgtb UCLOW_reg, %xmm8; \
> > - pcmpgtb reg1, %xmm9; \
> > - pcmpgtb UCLOW_reg, %xmm10; \
> > - pcmpgtb reg2, %xmm11; \
> > - pand %xmm9, %xmm8; \
> > - pand %xmm11, %xmm10; \
> > - pand LCQWORD_reg, %xmm8; \
> > - pand LCQWORD_reg, %xmm10; \
> > - por %xmm8, reg1; \
> > - por %xmm10, reg2
> > - TOLOWER (%xmm1, %xmm2)
> > +# define TOLOWER(reg1, reg2) \
> > + movdqa LCASE_MIN_reg, %xmm8; \
> > + movdqa LCASE_MIN_reg, %xmm9; \
> > + paddb reg1, %xmm8; \
> > + paddb reg2, %xmm9; \
> > + pcmpgtb LCASE_MAX_reg, %xmm8; \
> > + pcmpgtb LCASE_MAX_reg, %xmm9; \
> > + pandn CASE_ADD_reg, %xmm8; \
> > + pandn CASE_ADD_reg, %xmm9; \
> > + paddb %xmm8, reg1; \
> > + paddb %xmm9, reg2
> > + TOLOWER (%xmm1, %xmm2)
> > #else
> > # define TOLOWER(reg1, reg2)
> > #endif
> > --
> > 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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