From 482eec0d1188823ad93247f79bf965886e8bd4f7 Mon Sep 17 00:00:00 2001 From: Ulrich Drepper Date: Sat, 16 Jan 1999 17:09:04 +0000 Subject: Update. 1999-01-16 Ulrich Drepper * elf/Makefile (tests): Add loadtest. Add rules to generate test modules. * Makeconfig (+link): Add $(LDFLAGS-$(@F)) to command line. * elf/loadtest.c: New file. * elf/testobj1.c: New file. * elf/testobj2.c: New file. * elf/testobj3.c: New file. * elf/dl-close.c: Correct removing module from global list. * elf/dl-open.c: Add debugging code. * include/string.h: Add __rawmemchr prototype. * string/Makefile (routines): Add rawmemchr. * string/Versions [GLIBC_2.1]: Add __rawmemchr and rawmemchr. * string/string.h: Add prototype for rawmemchr. * string/bits/string2.h: Optimize strchr with rawmemchr. * sysdeps/generic/rawmemchr.c: New file. * sysdeps/i386/rawmemchr.c: New file. * sysdeps/i386/i486/bits/string.h: Add rawmemchr inline code. Optimize strchr with rawmemchr. * sysdeps/unix/sysv/linux/bits/posix_opt.h: Define _LFS_LARGEFILE, _LFS64_LARGEFILE, and _LFS64_STDIO for Unix98. 1999-01-14 Andreas Jaeger * nis/nis_error.c (nis_errlist): Fix capitilasation. --- sysdeps/i386/i486/bits/string.h | 30 +++++- sysdeps/i386/rawmemchr.S | 218 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 246 insertions(+), 2 deletions(-) create mode 100644 sysdeps/i386/rawmemchr.S (limited to 'sysdeps/i386') diff --git a/sysdeps/i386/i486/bits/string.h b/sysdeps/i386/i486/bits/string.h index f810de06ea..e20f037ab7 100644 --- a/sysdeps/i386/i486/bits/string.h +++ b/sysdeps/i386/i486/bits/string.h @@ -1,5 +1,5 @@ /* Optimized, inlined string functions. i486 version. - Copyright (C) 1997, 1998 Free Software Foundation, Inc. + Copyright (C) 1997, 1998, 1999 Free Software Foundation, Inc. This file is part of the GNU C Library. The GNU C Library is free software; you can redistribute it and/or @@ -377,6 +377,30 @@ memchr (__const void *__s, int __c, size_t __n) } +/* Return pointer to C in S. */ +#define _HAVE_STRING_ARCH_rawmemchr 1 +__STRING_INLINE void * +__rawmemchr (const void *__s, int __c) +{ + register unsigned long int __d0; + register unsigned char *__res; + __asm__ __volatile__ + ("cld\n\t" + "repne; scasb\n\t" + : "=D" (__res), "=&c" (__d0) + : "a" (__c), "0" (__s), "1" (0xffffffff) + : "cc"); + return __res - 1; +} +#ifdef __USE_GNU +__STRING_INLINE void * +rawmemchr (const void *__s, int __c) +{ + return __rawmemchr (__s, __c); +} +#endif /* use GNU */ + + /* Return the length of S. */ #define _HAVE_STRING_ARCH_strlen 1 #define strlen(str) \ @@ -1049,7 +1073,9 @@ __strncmp_g (__const char *__s1, __const char *__s2, size_t __n) #define _HAVE_STRING_ARCH_strchr 1 #define strchr(s, c) \ (__extension__ (__builtin_constant_p (c) \ - ? __strchr_c (s, ((c) & 0xff) << 8) \ + ? ((c) == '\0' \ + ? (char *) __rawmemchr (s, c) \ + : __strchr_c (s, ((c) & 0xff) << 8)) \ : __strchr_g (s, c))) __STRING_INLINE char *__strchr_c (__const char *__s, int __c); diff --git a/sysdeps/i386/rawmemchr.S b/sysdeps/i386/rawmemchr.S new file mode 100644 index 0000000000..83626e0473 --- /dev/null +++ b/sysdeps/i386/rawmemchr.S @@ -0,0 +1,218 @@ +/* rawmemchr (str, ch) -- Return pointer to first occurrence of CH in STR. + For Intel 80x86, x>=3. + Copyright (C) 1994, 95, 96, 97, 98, 99 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Ulrich Drepper + Optimised a little by Alan Modra + + This version is developed using the same algorithm as the fast C + version which carries the following introduction: + + Based on strlen implementation by Torbjorn Granlund (tege@sics.se), + with help from Dan Sahlin (dan@sics.se) and + commentary by Jim Blandy (jimb@ai.mit.edu); + adaptation to memchr suggested by Dick Karpinski (dick@cca.ucsf.edu), + and implemented by Roland McGrath (roland@ai.mit.edu). + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Library General Public License as + published by the Free Software Foundation; either version 2 of the + License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Library General Public License for more details. + + You should have received a copy of the GNU Library General Public + License along with the GNU C Library; see the file COPYING.LIB. If not, + write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, + Boston, MA 02111-1307, USA. */ + +#include +#include "asm-syntax.h" + +/* + INPUT PARAMETERS: + str (sp + 4) + c (sp + 8) +*/ + + .text +ENTRY (__rawmemchr) + /* Save callee-safe register used in this function. */ + pushl %edi + + /* Load parameters into registers. */ + movl 8(%esp), %eax /* str: pointer to memory block. */ + movl 12(%esp), %edx /* c: byte we are looking for. */ + + /* At the moment %edx contains C. What we need for the + algorithm is C in all bytes of the dword. Avoid + operations on 16 bit words because these require an + prefix byte (and one more cycle). */ + movb %dl, %dh /* Now it is 0|0|c|c */ + movl %edx, %ecx + shll $16, %edx /* Now c|c|0|0 */ + movw %cx, %dx /* And finally c|c|c|c */ + + /* Better performance can be achieved if the word (32 + bit) memory access is aligned on a four-byte-boundary. + So process first bytes one by one until boundary is + reached. Don't use a loop for better performance. */ + + testb $3, %al /* correctly aligned ? */ + je L(1) /* yes => begin loop */ + cmpb %dl, (%eax) /* compare byte */ + je L(9) /* target found => return */ + incl %eax /* increment source pointer */ + + testb $3, %al /* correctly aligned ? */ + je L(1) /* yes => begin loop */ + cmpb %dl, (%eax) /* compare byte */ + je L(9) /* target found => return */ + incl %eax /* increment source pointer */ + + testb $3, %al /* correctly aligned ? */ + je L(1) /* yes => begin loop */ + cmpb %dl, (%eax) /* compare byte */ + je L(9) /* target found => return */ + incl %eax /* increment source pointer */ + + /* We exit the loop if adding MAGIC_BITS to LONGWORD fails to + change any of the hole bits of LONGWORD. + + 1) Is this safe? Will it catch all the zero bytes? + Suppose there is a byte with all zeros. Any carry bits + propagating from its left will fall into the hole at its + least significant bit and stop. Since there will be no + carry from its most significant bit, the LSB of the + byte to the left will be unchanged, and the zero will be + detected. + + 2) Is this worthwhile? Will it ignore everything except + zero bytes? Suppose every byte of LONGWORD has a bit set + somewhere. There will be a carry into bit 8. If bit 8 + is set, this will carry into bit 16. If bit 8 is clear, + one of bits 9-15 must be set, so there will be a carry + into bit 16. Similarly, there will be a carry into bit + 24. If one of bits 24-31 is set, there will be a carry + into bit 32 (=carry flag), so all of the hole bits will + be changed. + + 3) But wait! Aren't we looking for C, not zero? + Good point. So what we do is XOR LONGWORD with a longword, + each of whose bytes is C. This turns each byte that is C + into a zero. */ + + + /* Each round the main loop processes 16 bytes. */ + ALIGN (4) + +L(1): movl (%eax), %ecx /* get word (= 4 bytes) in question */ + movl $0xfefefeff, %edi /* magic value */ + xorl %edx, %ecx /* XOR with word c|c|c|c => bytes of str == c + are now 0 */ + addl %ecx, %edi /* add the magic value to the word. We get + carry bits reported for each byte which + is *not* 0 */ + + /* According to the algorithm we had to reverse the effect of the + XOR first and then test the overflow bits. But because the + following XOR would destroy the carry flag and it would (in a + representation with more than 32 bits) not alter then last + overflow, we can now test this condition. If no carry is signaled + no overflow must have occurred in the last byte => it was 0. */ + jnc L(8) + + /* We are only interested in carry bits that change due to the + previous add, so remove original bits */ + xorl %ecx, %edi /* ((word^charmask)+magic)^(word^charmask) */ + + /* Now test for the other three overflow bits. */ + orl $0xfefefeff, %edi /* set all non-carry bits */ + incl %edi /* add 1: if one carry bit was *not* set + the addition will not result in 0. */ + + /* If at least one byte of the word is C we don't get 0 in %edi. */ + jnz L(8) /* found it => return pointer */ + + /* This process is unfolded four times for better performance. + we don't increment the source pointer each time. Instead we + use offsets and increment by 16 in each run of the loop. But + before probing for the matching byte we need some extra code + (following LL(13) below). Even the len can be compared with + constants instead of decrementing each time. */ + + movl 4(%eax), %ecx /* get word (= 4 bytes) in question */ + movl $0xfefefeff, %edi /* magic value */ + xorl %edx, %ecx /* XOR with word c|c|c|c => bytes of str == c + are now 0 */ + addl %ecx, %edi /* add the magic value to the word. We get + carry bits reported for each byte which + is *not* 0 */ + jnc L(7) /* highest byte is C => return pointer */ + xorl %ecx, %edi /* ((word^charmask)+magic)^(word^charmask) */ + orl $0xfefefeff, %edi /* set all non-carry bits */ + incl %edi /* add 1: if one carry bit was *not* set + the addition will not result in 0. */ + jnz L(7) /* found it => return pointer */ + + movl 8(%eax), %ecx /* get word (= 4 bytes) in question */ + movl $0xfefefeff, %edi /* magic value */ + xorl %edx, %ecx /* XOR with word c|c|c|c => bytes of str == c + are now 0 */ + addl %ecx, %edi /* add the magic value to the word. We get + carry bits reported for each byte which + is *not* 0 */ + jnc L(6) /* highest byte is C => return pointer */ + xorl %ecx, %edi /* ((word^charmask)+magic)^(word^charmask) */ + orl $0xfefefeff, %edi /* set all non-carry bits */ + incl %edi /* add 1: if one carry bit was *not* set + the addition will not result in 0. */ + jnz L(6) /* found it => return pointer */ + + movl 12(%eax), %ecx /* get word (= 4 bytes) in question */ + movl $0xfefefeff, %edi /* magic value */ + xorl %edx, %ecx /* XOR with word c|c|c|c => bytes of str == c + are now 0 */ + addl %ecx, %edi /* add the magic value to the word. We get + carry bits reported for each byte which + is *not* 0 */ + jnc L(5) /* highest byte is C => return pointer */ + xorl %ecx, %edi /* ((word^charmask)+magic)^(word^charmask) */ + orl $0xfefefeff, %edi /* set all non-carry bits */ + incl %edi /* add 1: if one carry bit was *not* set + the addition will not result in 0. */ + jnz L(5) /* found it => return pointer */ + + /* Adjust both counters for a full round, i.e. 16 bytes. */ + addl $16, %eax + jmp L(1) + /* add missing source pointer increments */ +L(5): addl $4, %eax +L(6): addl $4, %eax +L(7): addl $4, %eax + + /* Test for the matching byte in the word. %ecx contains a NUL + char in the byte which originally was the byte we are looking + at. */ +L(8): testb %cl, %cl /* test first byte in dword */ + jz L(9) /* if zero => return pointer */ + incl %eax /* increment source pointer */ + + testb %ch, %ch /* test second byte in dword */ + jz L(9) /* if zero => return pointer */ + incl %eax /* increment source pointer */ + + testl $0xff0000, %ecx /* test third byte in dword */ + jz L(9) /* if zero => return pointer */ + incl %eax /* increment source pointer */ + + /* No further test needed we we know it is one of the four bytes. */ + +L(9): popl %edi /* pop saved register */ + + ret +END (__rawmemchr) +weak_alias (__rawmemchr, rawmemchr) -- cgit v1.2.3