diff options
Diffstat (limited to 'sysdeps/i386/i486/strcat.S')
| -rw-r--r-- | sysdeps/i386/i486/strcat.S | 260 |
1 files changed, 260 insertions, 0 deletions
diff --git a/sysdeps/i386/i486/strcat.S b/sysdeps/i386/i486/strcat.S new file mode 100644 index 0000000000..e3d2181bdb --- /dev/null +++ b/sysdeps/i386/i486/strcat.S @@ -0,0 +1,260 @@ +/* strcat(dest, src) -- Append SRC on the end of DEST. +For Intel 80x86, x>=4. +Copyright (C) 1994, 1995 Free Software Foundation, Inc. +Contributed by Ulrich Drepper <drepper@ipd.info.uni-karlsruhe.de>. +Optimised a little by Alan Modra <Alan@SPRI.Levels.UniSA.Edu.Au> +This file is part of the GNU C Library. + +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 <sysdep.h> +#include "asm-syntax.h" + +/* + INPUT PARAMETERS: + dest (sp + 4) + src (sp + 8) +*/ + + .text +ENTRY (strcat) + pushl %edi /* Save callee-safe register. */ + + movl 12(%esp), %ecx /* load source pointer */ + movl 8(%esp), %edx /* load destination pointer */ + + testb $0xff, (%ecx) /* Is source string empty? */ + jz L8 /* yes => return */ + + /* Test the first bytes separately until destination is aligned. */ + testb $3, %edx /* destination pointer aligned? */ + jz L1 /* yes => begin scan loop */ + testb $0xff, (%edx) /* is end of string? */ + jz L2 /* yes => start appending */ + incl %edx /* increment source pointer */ + + testb $3, %edx /* destination pointer aligned? */ + jz L1 /* yes => begin scan loop */ + testb $0xff, (%edx) /* is end of string? */ + jz L2 /* yes => start appending */ + incl %edx /* increment source pointer */ + + testb $3, %edx /* destination pointer aligned? */ + jz L1 /* yes => begin scan loop */ + testb $0xff, (%edx) /* is end of string? */ + jz L2 /* yes => start appending */ + incl %edx /* increment source pointer */ + + /* Now we are aligned. Begin scan loop. */ + jmp L1 + + ALIGN(4) + +L4: addl $16,%edx /* increment destination pointer for round */ + +L1: movl (%edx), %eax /* get word (= 4 bytes) in question */ + movl $0xfefefeff, %edi /* magic value */ + + /* If you compare this with the algorithm in memchr.S you will + notice that here is an `xorl' statement missing. But you must + not forget that we are looking for C == 0 and `xorl $0, %eax' + is a no-op. */ + + addl %eax, %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 occured in the last byte => it was 0. */ + jnc L3 + + /* We are only interested in carry bits that change due to the + previous add, so remove original bits */ + xorl %eax, %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 %ecx. */ + jnz L3 + + movl 4(%edx), %eax /* get word from source */ + movl $0xfefefeff, %edi /* magic value */ + addl %eax, %edi /* add the magic value to the word. We get + carry bits reported for each byte which + is *not* 0 */ + jnc L5 /* highest byte is C => stop copying */ + xorl %eax, %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 L5 /* one byte is NUL => stop copying */ + + movl 8(%edx), %eax /* get word from source */ + movl $0xfefefeff, %edi /* magic value */ + addl %eax, %edi /* add the magic value to the word. We get + carry bits reported for each byte which + is *not* 0 */ + jnc L6 /* highest byte is C => stop copying */ + xorl %eax, %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 L6 /* one byte is NUL => stop copying */ + + movl 12(%edx), %eax /* get word from source */ + movl $0xfefefeff, %edi /* magic value */ + addl %eax, %edi /* add the magic value to the word. We get + carry bits reported for each byte which + is *not* 0 */ + jnc L7 /* highest byte is C => stop copying */ + xorl %eax, %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. */ + jz L4 /* no byte is NUL => carry on copying */ + +L7: addl $4, %edx /* adjust source pointer */ +L6: addl $4, %edx +L5: addl $4, %edx + +L3: testb %al, %al /* is first byte NUL? */ + jz L2 /* yes => start copying */ + incl %edx /* increment source pointer */ + + testb %ah, %ah /* is second byte NUL? */ + jz L2 /* yes => start copying */ + incl %edx /* increment source pointer */ + + testl $0xff0000, %eax /* is third byte NUL? */ + jz L2 /* yes => start copying */ + incl %edx /* increment source pointer */ + +L2: subl %ecx, %edx /* reduce number of loop variants */ + + /* Now we have to align the source pointer. */ + testb $3, %ecx /* pointer correctly aligned? */ + jz L29 /* yes => start copy loop */ + movb (%ecx), %al /* get first byte */ + movb %al, (%ecx,%edx) /* and store it */ + andl %al, %al /* is byte NUL? */ + jz L8 /* yes => return */ + incl %ecx /* increment pointer */ + + testb $3, %ecx /* pointer correctly aligned? */ + jz L29 /* yes => start copy loop */ + movb (%ecx), %al /* get first byte */ + movb %al, (%ecx,%edx) /* and store it */ + andl %al, %al /* is byte NUL? */ + jz L8 /* yes => return */ + incl %ecx /* increment pointer */ + + testb $3, %ecx /* pointer correctly aligned? */ + jz L29 /* yes => start copy loop */ + movb (%ecx), %al /* get first byte */ + movb %al, (%ecx,%edx) /* and store it */ + andl %al, %al /* is byte NUL? */ + jz L8 /* yes => return */ + incl %ecx /* increment pointer */ + + /* Now we are aligned. */ + jmp L29 /* start copy loop */ + + ALIGN(4) + +L28: movl %eax, 12(%ecx,%edx)/* store word at destination */ + addl $16, %ecx /* adjust pointer for full round */ + +L29: movl (%ecx), %eax /* get word from source */ + movl $0xfefefeff, %edi /* magic value */ + addl %eax, %edi /* add the magic value to the word. We get + carry bits reported for each byte which + is *not* 0 */ + jnc L9 /* highest byte is C => stop copying */ + xorl %eax, %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 L9 /* one byte is NUL => stop copying */ + movl %eax, (%ecx,%edx) /* store word to destination */ + + movl 4(%ecx), %eax /* get word from source */ + movl $0xfefefeff, %edi /* magic value */ + addl %eax, %edi /* add the magic value to the word. We get + carry bits reported for each byte which + is *not* 0 */ + jnc L91 /* highest byte is C => stop copying */ + xorl %eax, %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 L91 /* one byte is NUL => stop copying */ + movl %eax, 4(%ecx,%edx) /* store word to destination */ + + movl 8(%ecx), %eax /* get word from source */ + movl $0xfefefeff, %edi /* magic value */ + addl %eax, %edi /* add the magic value to the word. We get + carry bits reported for each byte which + is *not* 0 */ + jnc L92 /* highest byte is C => stop copying */ + xorl %eax, %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 L92 /* one byte is NUL => stop copying */ + movl %eax, 8(%ecx,%edx) /* store word to destination */ + + movl 12(%ecx), %eax /* get word from source */ + movl $0xfefefeff, %edi /* magic value */ + addl %eax, %edi /* add the magic value to the word. We get + carry bits reported for each byte which + is *not* 0 */ + jnc L93 /* highest byte is C => stop copying */ + xorl %eax, %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. */ + jz L28 /* no is NUL => carry on copying */ + +L93: addl $4, %ecx /* adjust pointer */ +L92: addl $4, %ecx +L91: addl $4, %ecx + +L9: movb %al, (%ecx,%edx) /* store first byte of last word */ + orb %al, %al /* is it NUL? */ + jz L8 /* yes => return */ + + movb %ah, 1(%ecx,%edx) /* store second byte of last word */ + orb %ah, %ah /* is it NUL? */ + jz L8 /* yes => return */ + + shrl $16, %eax /* make upper bytes accessible */ + movb %al, 2(%ecx,%edx) /* store third byte of last word */ + orb %al, %al /* is it NUL? */ + jz L8 /* yes => return */ + + movb %ah, 3(%ecx,%edx) /* store fourth byte of last word */ + +L8: movl 8(%esp), %eax /* start address of destination is result */ + popl %edi /* restore saved register */ + + ret |