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* [glibc] x86: Optimize str{n}casecmp TOLOWER logic in strcmp.S
@ 2022-03-25 18:19 Noah Goldstein
0 siblings, 0 replies; only message in thread
From: Noah Goldstein @ 2022-03-25 18:19 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=670b54bc585ea4a94f3b2e9272ba44aa6b730b73
commit 670b54bc585ea4a94f3b2e9272ba44aa6b730b73
Author: Noah Goldstein <goldstein.w.n@gmail.com>
Date: Wed Mar 23 16:57:36 2022 -0500
x86: Optimize str{n}casecmp TOLOWER logic in strcmp.S
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>
Diff:
---
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
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