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Diffstat (limited to 'sysdeps/i386/i586/strchr.S')
| -rw-r--r-- | sysdeps/i386/i586/strchr.S | 348 |
1 files changed, 0 insertions, 348 deletions
diff --git a/sysdeps/i386/i586/strchr.S b/sysdeps/i386/i586/strchr.S deleted file mode 100644 index 02f66b8f72..0000000000 --- a/sysdeps/i386/i586/strchr.S +++ /dev/null @@ -1,348 +0,0 @@ -/* Find character CH in a NUL terminated string. - Highly optimized version for ix85, x>=5. - Copyright (C) 1995-2017 Free Software Foundation, Inc. - This file is part of the GNU C Library. - Contributed by Ulrich Drepper, <drepper@gnu.ai.mit.edu>. - - The GNU C Library is free software; you can redistribute it and/or - modify it under the terms of the GNU Lesser General Public - License as published by the Free Software Foundation; either - version 2.1 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 - Lesser General Public License for more details. - - You should have received a copy of the GNU Lesser General Public - License along with the GNU C Library; if not, see - <http://www.gnu.org/licenses/>. */ - -#include <sysdep.h> -#include "asm-syntax.h" - -/* This version is especially optimized for the i586 (and following?) - processors. This is mainly done by using the two pipelines. The - version optimized for i486 is weak in this aspect because to get - as much parallelism we have to execute some *more* instructions. - - The code below is structured to reflect the pairing of the instructions - as *I think* it is. I have no processor data book to verify this. - If you find something you think is incorrect let me know. */ - - -/* The magic value which is used throughout in the whole code. */ -#define magic 0xfefefeff - -#define PARMS 4+16 /* space for 4 saved regs */ -#define RTN PARMS -#define STR RTN -#define CHR STR+4 - - .text -ENTRY (strchr) - - pushl %edi /* Save callee-safe registers. */ - cfi_adjust_cfa_offset (-4) - pushl %esi - cfi_adjust_cfa_offset (-4) - - pushl %ebx - cfi_adjust_cfa_offset (-4) - pushl %ebp - cfi_adjust_cfa_offset (-4) - - movl STR(%esp), %eax - movl CHR(%esp), %edx - - movl %eax, %edi /* duplicate string pointer for later */ - cfi_rel_offset (edi, 12) - xorl %ecx, %ecx /* clear %ecx */ - - /* 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 */ - movb %dl, %cl /* we construct the lower half in %ecx */ - - shll $16, %edx /* now %edx is c|c|0|0 */ - movb %cl, %ch /* now %ecx is 0|0|c|c */ - - orl %ecx, %edx /* and finally c|c|c|c */ - andl $3, %edi /* mask alignment bits */ - - jz L(11) /* alignment is 0 => start loop */ - - movb %dl, %cl /* 0 is needed below */ - jp L(0) /* exactly two bits set */ - - xorb (%eax), %cl /* is byte the one we are looking for? */ - jz L(out) /* yes => return pointer */ - - xorb %dl, %cl /* load single byte and test for NUL */ - je L(3) /* yes => return NULL */ - - movb 1(%eax), %cl /* load single byte */ - incl %eax - - cmpb %cl, %dl /* is byte == C? */ - je L(out) /* aligned => return pointer */ - - cmpb $0, %cl /* is byte NUL? */ - je L(3) /* yes => return NULL */ - - incl %eax - decl %edi - - jne L(11) - -L(0): movb (%eax), %cl /* load single byte */ - - cmpb %cl, %dl /* is byte == C? */ - je L(out) /* aligned => return pointer */ - - cmpb $0, %cl /* is byte NUL? */ - je L(3) /* yes => return NULL */ - - incl %eax /* increment pointer */ - - cfi_rel_offset (esi, 8) - cfi_rel_offset (ebx, 4) - cfi_rel_offset (ebp, 0) - - /* The following code is the preparation for the loop. The - four instruction up to `L1' will not be executed in the loop - because the same code is found at the end of the loop, but - there it is executed in parallel with other instructions. */ -L(11): movl (%eax), %ecx - movl $magic, %ebp - - movl $magic, %edi - addl %ecx, %ebp - - /* The main loop: it looks complex and indeed it is. I would - love to say `it was hard to write, so it should he hard to - read' but I will give some more hints. To fully understand - this code you should first take a look at the i486 version. - The basic algorithm is the same, but here the code organized - in a way which permits to use both pipelines all the time. - - I tried to make it a bit more understandable by indenting - the code according to stage in the algorithm. It goes as - follows: - check for 0 in 1st word - check for C in 1st word - check for 0 in 2nd word - check for C in 2nd word - check for 0 in 3rd word - check for C in 3rd word - check for 0 in 4th word - check for C in 4th word - - Please note that doing the test for NUL before the test for - C allows us to overlap the test for 0 in the next word with - the test for C. */ - -L(1): xorl %ecx, %ebp /* (word^magic) */ - addl %ecx, %edi /* add magic word */ - - leal 4(%eax), %eax /* increment pointer */ - jnc L(4) /* previous addl caused overflow? */ - - movl %ecx, %ebx /* duplicate original word */ - orl $magic, %ebp /* (word^magic)|magic */ - - addl $1, %ebp /* (word^magic)|magic == 0xffffffff? */ - jne L(4) /* yes => we found word with NUL */ - - movl $magic, %esi /* load magic value */ - xorl %edx, %ebx /* clear words which are C */ - - movl (%eax), %ecx - addl %ebx, %esi /* (word+magic) */ - - movl $magic, %edi - jnc L(5) /* previous addl caused overflow? */ - - movl %edi, %ebp - xorl %ebx, %esi /* (word+magic)^word */ - - addl %ecx, %ebp - orl $magic, %esi /* ((word+magic)^word)|magic */ - - addl $1, %esi /* ((word+magic)^word)|magic==0xf..f?*/ - jne L(5) /* yes => we found word with C */ - - xorl %ecx, %ebp - addl %ecx, %edi - - leal 4(%eax), %eax - jnc L(4) - - movl %ecx, %ebx - orl $magic, %ebp - - addl $1, %ebp - jne L(4) - - movl $magic, %esi - xorl %edx, %ebx - - movl (%eax), %ecx - addl %ebx, %esi - - movl $magic, %edi - jnc L(5) - - movl %edi, %ebp - xorl %ebx, %esi - - addl %ecx, %ebp - orl $magic, %esi - - addl $1, %esi - jne L(5) - - xorl %ecx, %ebp - addl %ecx, %edi - - leal 4(%eax), %eax - jnc L(4) - - movl %ecx, %ebx - orl $magic, %ebp - - addl $1, %ebp - jne L(4) - - movl $magic, %esi - xorl %edx, %ebx - - movl (%eax), %ecx - addl %ebx, %esi - - movl $magic, %edi - jnc L(5) - - movl %edi, %ebp - xorl %ebx, %esi - - addl %ecx, %ebp - orl $magic, %esi - - addl $1, %esi - jne L(5) - - xorl %ecx, %ebp - addl %ecx, %edi - - leal 4(%eax), %eax - jnc L(4) - - movl %ecx, %ebx - orl $magic, %ebp - - addl $1, %ebp - jne L(4) - - movl $magic, %esi - xorl %edx, %ebx - - movl (%eax), %ecx - addl %ebx, %esi - - movl $magic, %edi - jnc L(5) - - movl %edi, %ebp - xorl %ebx, %esi - - addl %ecx, %ebp - orl $magic, %esi - - addl $1, %esi - - je L(1) - - /* We know there is no NUL byte but a C byte in the word. - %ebx contains NUL in this particular byte. */ -L(5): subl $4, %eax /* adjust pointer */ - testb %bl, %bl /* first byte == C? */ - - jz L(out) /* yes => return pointer */ - - incl %eax /* increment pointer */ - testb %bh, %bh /* second byte == C? */ - - jz L(out) /* yes => return pointer */ - - shrl $16, %ebx /* make upper bytes accessible */ - incl %eax /* increment pointer */ - - cmp $0, %bl /* third byte == C */ - je L(out) /* yes => return pointer */ - - incl %eax /* increment pointer */ - -L(out): popl %ebp /* restore saved registers */ - cfi_adjust_cfa_offset (-4) - cfi_restore (ebp) - popl %ebx - cfi_adjust_cfa_offset (-4) - cfi_restore (ebx) - - popl %esi - cfi_adjust_cfa_offset (-4) - cfi_restore (esi) - popl %edi - cfi_adjust_cfa_offset (-4) - cfi_restore (edi) - - ret - - cfi_adjust_cfa_offset (16) - cfi_rel_offset (edi, 12) - cfi_rel_offset (esi, 8) - cfi_rel_offset (ebx, 4) - cfi_rel_offset (ebp, 0) - /* We know there is a NUL byte in the word. But we have to test - whether there is an C byte before it in the word. */ -L(4): subl $4, %eax /* adjust pointer */ - cmpb %dl, %cl /* first byte == C? */ - - je L(out) /* yes => return pointer */ - - cmpb $0, %cl /* first byte == NUL? */ - je L(3) /* yes => return NULL */ - - incl %eax /* increment pointer */ - - cmpb %dl, %ch /* second byte == C? */ - je L(out) /* yes => return pointer */ - - cmpb $0, %ch /* second byte == NUL? */ - je L(3) /* yes => return NULL */ - - shrl $16, %ecx /* make upper bytes accessible */ - incl %eax /* increment pointer */ - - cmpb %dl, %cl /* third byte == C? */ - je L(out) /* yes => return pointer */ - - cmpb $0, %cl /* third byte == NUL? */ - je L(3) /* yes => return NULL */ - - incl %eax /* increment pointer */ - - /* The test four the fourth byte is necessary! */ - cmpb %dl, %ch /* fourth byte == C? */ - je L(out) /* yes => return pointer */ - -L(3): xorl %eax, %eax - jmp L(out) -END (strchr) - -#undef index -weak_alias (strchr, index) -libc_hidden_builtin_def (strchr) |