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x86: Optimize str{n}casecmp TOLOWER logic in strcmp.S

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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.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

(cherry picked from commit 670b54bc58)
This commit is contained in:
Noah Goldstein 2022-03-23 16:57:36 -05:00 committed by Sunil K Pandey
parent a4b1cae068
commit 5997011826
1 changed files with 29 additions and 35 deletions
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64
sysdeps/x86_64/strcmp.S
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@ -78,9 +78,8 @@ 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)
@ -97,9 +96,8 @@ 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)
@ -149,22 +147,22 @@ 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 */
@ -175,22 +173,18 @@ 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