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From 017773f93b0e41f3b164e5db86d0c7b7f75675e9 Mon Sep 17 00:00:00 2001
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From: Noah Goldstein <goldstein.w.n@gmail.com>
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Date: Wed, 23 Mar 2022 16:57:36 -0500
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Subject: [PATCH] x86: Optimize str{n}casecmp TOLOWER logic in strcmp.S
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Slightly faster method of doing TOLOWER that saves an
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instruction.
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Also replace the hard coded 5-byte no with .p2align 4. On builds with
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CET enabled this misaligned entry to strcasecmp.
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geometric_mean(N=40) of all benchmarks New / Original: .894
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All string/memory tests pass.
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Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
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(cherry picked from commit 670b54bc585ea4a94f3b2e9272ba44aa6b730b73)
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---
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sysdeps/x86_64/strcmp.S | 64 +++++++++++++++++++----------------------
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1 file changed, 29 insertions(+), 35 deletions(-)
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diff --git a/sysdeps/x86_64/strcmp.S b/sysdeps/x86_64/strcmp.S
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index aa6df898..f454ce5b 100644
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--- a/sysdeps/x86_64/strcmp.S
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+++ b/sysdeps/x86_64/strcmp.S
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@@ -78,9 +78,8 @@ ENTRY2 (__strcasecmp)
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movq __libc_tsd_LOCALE@gottpoff(%rip),%rax
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mov %fs:(%rax),%RDX_LP
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- // XXX 5 byte should be before the function
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- /* 5-byte NOP. */
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- .byte 0x0f,0x1f,0x44,0x00,0x00
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+ /* Either 1 or 5 bytes (dependeing if CET is enabled). */
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+ .p2align 4
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END2 (__strcasecmp)
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# ifndef NO_NOLOCALE_ALIAS
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weak_alias (__strcasecmp, strcasecmp)
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@@ -97,9 +96,8 @@ ENTRY2 (__strncasecmp)
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movq __libc_tsd_LOCALE@gottpoff(%rip),%rax
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mov %fs:(%rax),%RCX_LP
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- // XXX 5 byte should be before the function
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- /* 5-byte NOP. */
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- .byte 0x0f,0x1f,0x44,0x00,0x00
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+ /* Either 1 or 5 bytes (dependeing if CET is enabled). */
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+ .p2align 4
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END2 (__strncasecmp)
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# ifndef NO_NOLOCALE_ALIAS
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weak_alias (__strncasecmp, strncasecmp)
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@@ -149,22 +147,22 @@ ENTRY (STRCMP)
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#if defined USE_AS_STRCASECMP_L || defined USE_AS_STRNCASECMP_L
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.section .rodata.cst16,"aM",@progbits,16
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.align 16
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-.Lbelowupper:
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- .quad 0x4040404040404040
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- .quad 0x4040404040404040
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-.Ltopupper:
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- .quad 0x5b5b5b5b5b5b5b5b
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- .quad 0x5b5b5b5b5b5b5b5b
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-.Ltouppermask:
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+.Llcase_min:
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+ .quad 0x3f3f3f3f3f3f3f3f
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+ .quad 0x3f3f3f3f3f3f3f3f
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+.Llcase_max:
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+ .quad 0x9999999999999999
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+ .quad 0x9999999999999999
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+.Lcase_add:
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.quad 0x2020202020202020
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.quad 0x2020202020202020
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.previous
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- movdqa .Lbelowupper(%rip), %xmm5
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-# define UCLOW_reg %xmm5
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- movdqa .Ltopupper(%rip), %xmm6
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-# define UCHIGH_reg %xmm6
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- movdqa .Ltouppermask(%rip), %xmm7
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-# define LCQWORD_reg %xmm7
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+ movdqa .Llcase_min(%rip), %xmm5
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+# define LCASE_MIN_reg %xmm5
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+ movdqa .Llcase_max(%rip), %xmm6
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+# define LCASE_MAX_reg %xmm6
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+ movdqa .Lcase_add(%rip), %xmm7
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+# define CASE_ADD_reg %xmm7
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#endif
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cmp $0x30, %ecx
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ja LABEL(crosscache) /* rsi: 16-byte load will cross cache line */
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@@ -175,22 +173,18 @@ ENTRY (STRCMP)
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movhpd 8(%rdi), %xmm1
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movhpd 8(%rsi), %xmm2
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#if defined USE_AS_STRCASECMP_L || defined USE_AS_STRNCASECMP_L
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-# define TOLOWER(reg1, reg2) \
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- movdqa reg1, %xmm8; \
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- movdqa UCHIGH_reg, %xmm9; \
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- movdqa reg2, %xmm10; \
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- movdqa UCHIGH_reg, %xmm11; \
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- pcmpgtb UCLOW_reg, %xmm8; \
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- pcmpgtb reg1, %xmm9; \
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- pcmpgtb UCLOW_reg, %xmm10; \
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- pcmpgtb reg2, %xmm11; \
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- pand %xmm9, %xmm8; \
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- pand %xmm11, %xmm10; \
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- pand LCQWORD_reg, %xmm8; \
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- pand LCQWORD_reg, %xmm10; \
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- por %xmm8, reg1; \
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- por %xmm10, reg2
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- TOLOWER (%xmm1, %xmm2)
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+# define TOLOWER(reg1, reg2) \
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+ movdqa LCASE_MIN_reg, %xmm8; \
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+ movdqa LCASE_MIN_reg, %xmm9; \
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+ paddb reg1, %xmm8; \
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+ paddb reg2, %xmm9; \
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+ pcmpgtb LCASE_MAX_reg, %xmm8; \
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+ pcmpgtb LCASE_MAX_reg, %xmm9; \
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+ pandn CASE_ADD_reg, %xmm8; \
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+ pandn CASE_ADD_reg, %xmm9; \
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+ paddb %xmm8, reg1; \
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+ paddb %xmm9, reg2
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+ TOLOWER (%xmm1, %xmm2)
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#else
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# define TOLOWER(reg1, reg2)
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#endif
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--
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GitLab
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