Optimize strchr for x86.
* libc/machine/i386/strchr.S (strchr): Pre-align data so unaligned searches aren't penalized. Special-case searching for 0.
This commit is contained in:
Eric Blake
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804c0cc6d0
commit
4962a9453a
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@ -1,3 +1,9 @@
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2008-05-21 Eric Blake <ebb9@byu.net>
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Optimize strchr for x86.
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* libc/machine/i386/strchr.S (strchr): Pre-align data so unaligned
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searches aren't penalized. Special-case searching for 0.
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2008-05-20 Nick Clifton <nickc@redhat.com>
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* libc/sys/sysnecv850/crt0.S (___dso_handle): Define (weak).
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@ -5,7 +11,7 @@
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2008-05-20 DJ Delorie <dj@redhat.com>
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* libc/sys/sysnecv850/isatty.c (_isatty): Renamed from isatty.
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2008-05-14 Jeff Johnston <jjohnstn@redhat.com>
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* libc/include/sys/reent.h: Change _REENT_INIT... macros to
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@ -1,6 +1,6 @@
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/*
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* ====================================================
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* Copyright (C) 1998, 2002 by Red Hat Inc. All rights reserved.
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* Copyright (C) 1998, 2002, 2008 by Red Hat Inc. All rights reserved.
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*
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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@ -9,7 +9,7 @@
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*/
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#include "i386mach.h"
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.global SYM (strchr)
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SOTYPE_FUNCTION(strchr)
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@ -21,14 +21,45 @@ SYM (strchr):
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pushl ebx
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xorl ebx,ebx
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movl 8(ebp),edi
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movb 12(ebp),bl
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addb 12(ebp),bl
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#ifndef __OPTIMIZE_SIZE__
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/* check if string is aligned, if not do check one byte at a time */
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#ifndef __OPTIMIZE_SIZE__
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/* Special case strchr(p,0). */
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je L25
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/* Do byte-wise checks until string is aligned. */
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test $3,edi
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jne L9
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je L5
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movl edi,eax
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movb (eax),cl
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testb cl,cl
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je L14
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cmpb bl,cl
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je L19
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incl edi
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test $3,edi
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je L5
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movl edi,eax
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movb (eax),cl
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testb cl,cl
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je L14
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cmpb bl,cl
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je L19
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incl edi
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test $3,edi
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je L5
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movl edi,eax
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movb (eax),cl
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testb cl,cl
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je L14
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cmpb bl,cl
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je L19
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incl edi
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/* create 4 byte mask which is just the desired byte repeated 4 times */
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L5:
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movl ebx,ecx
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sall $8,ebx
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subl $4,edi
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@ -49,15 +80,14 @@ L10:
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testl $-2139062144,edx
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jne L9
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movl ebx,eax
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xorl ecx,eax
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leal -16843009(eax),edx
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notl eax
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andl eax,edx
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xorl ebx,ecx
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leal -16843009(ecx),edx
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notl ecx
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andl ecx,edx
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testl $-2139062144,edx
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je L10
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#endif /* not __OPTIMIZE_SIZE__ */
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/* loop while (*s && *s++ != c) */
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L9:
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leal -1(edi),eax
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@ -69,7 +99,7 @@ L15:
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je L14
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cmpb bl,dl
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jne L15
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L14:
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/* if (*s == c) return address otherwise return NULL */
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cmpb bl,(eax)
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@ -83,3 +113,60 @@ L19:
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leave
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ret
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#ifndef __OPTIMIZE_SIZE__
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/* Special case strchr(p,0). */
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#if 0
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/* Hideous performance on modern machines. */
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L25:
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cld
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movl $-1,ecx
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xor eax,eax
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repnz
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scasb
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leal -1(edi),eax
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jmp L19
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#endif
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L25:
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/* Do byte-wise checks until string is aligned. */
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test $3,edi
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je L26
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movl edi,eax
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movb (eax),cl
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testb cl,cl
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je L19
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incl edi
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test $3,edi
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je L26
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movl edi,eax
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movb (eax),cl
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testb cl,cl
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je L19
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incl edi
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test $3,edi
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je L26
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movl edi,eax
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movb (eax),cl
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testb cl,cl
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je L19
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incl edi
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L26:
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subl $4,edi
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/* loop performing 4 byte mask checking for desired 0 byte */
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.p2align 4,,7
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L27:
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addl $4,edi
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movl (edi),ecx
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leal -16843009(ecx),edx
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movl ecx,eax
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notl eax
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andl eax,edx
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testl $-2139062144,edx
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je L27
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jmp L9
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#endif /* !__OPTIMIZE_SIZE__ */
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