diff options
Diffstat (limited to 'libc/string/x86_64/strcpy.S')
| -rw-r--r-- | libc/string/x86_64/strcpy.S | 153 |
1 files changed, 153 insertions, 0 deletions
diff --git a/libc/string/x86_64/strcpy.S b/libc/string/x86_64/strcpy.S new file mode 100644 index 000000000..0847e2b7c --- /dev/null +++ b/libc/string/x86_64/strcpy.S @@ -0,0 +1,153 @@ +/* strcpy/stpcpy implementation for x86-64. + Copyright (C) 2002 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Andreas Jaeger <aj@suse.de>, 2002. + + 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, write to the Free + Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA + 02111-1307 USA. */ + +#include "_glibc_inc.h" + +#ifndef USE_AS_STPCPY +# define STRCPY strcpy +#endif + + .text +ENTRY (BP_SYM (STRCPY)) + movq %rsi, %rcx /* Source register. */ + andl $7, %ecx /* mask alignment bits */ + movq %rdi, %rdx /* Duplicate destination pointer. */ + + jz 5f /* aligned => start loop */ + + neg %ecx /* We need to align to 8 bytes. */ + addl $8,%ecx + /* Search the first bytes directly. */ +0: + movb (%rsi), %al /* Fetch a byte */ + testb %al, %al /* Is it NUL? */ + movb %al, (%rdx) /* Store it */ + jz 4f /* If it was NUL, done! */ + incq %rsi + incq %rdx + decl %ecx + jnz 0b + +5: + movq $0xfefefefefefefeff,%r8 + + /* Now the sources is aligned. Unfortunatly we cannot force + to have both source and destination aligned, so ignore the + alignment of the destination. */ + .p2align 4 +1: + /* 1st unroll. */ + movq (%rsi), %rax /* Read double word (8 bytes). */ + addq $8, %rsi /* Adjust pointer for next word. */ + movq %rax, %r9 /* Save a copy for NUL finding. */ + addq %r8, %r9 /* add the magic value to the word. We get + carry bits reported for each byte which + is *not* 0 */ + jnc 3f /* highest byte is NUL => return pointer */ + xorq %rax, %r9 /* (word+magic)^word */ + orq %r8, %r9 /* set all non-carry bits */ + incq %r9 /* add 1: if one carry bit was *not* set + the addition will not result in 0. */ + + jnz 3f /* found NUL => return pointer */ + + movq %rax, (%rdx) /* Write value to destination. */ + addq $8, %rdx /* Adjust pointer. */ + + /* 2nd unroll. */ + movq (%rsi), %rax /* Read double word (8 bytes). */ + addq $8, %rsi /* Adjust pointer for next word. */ + movq %rax, %r9 /* Save a copy for NUL finding. */ + addq %r8, %r9 /* add the magic value to the word. We get + carry bits reported for each byte which + is *not* 0 */ + jnc 3f /* highest byte is NUL => return pointer */ + xorq %rax, %r9 /* (word+magic)^word */ + orq %r8, %r9 /* set all non-carry bits */ + incq %r9 /* add 1: if one carry bit was *not* set + the addition will not result in 0. */ + + jnz 3f /* found NUL => return pointer */ + + movq %rax, (%rdx) /* Write value to destination. */ + addq $8, %rdx /* Adjust pointer. */ + + /* 3rd unroll. */ + movq (%rsi), %rax /* Read double word (8 bytes). */ + addq $8, %rsi /* Adjust pointer for next word. */ + movq %rax, %r9 /* Save a copy for NUL finding. */ + addq %r8, %r9 /* add the magic value to the word. We get + carry bits reported for each byte which + is *not* 0 */ + jnc 3f /* highest byte is NUL => return pointer */ + xorq %rax, %r9 /* (word+magic)^word */ + orq %r8, %r9 /* set all non-carry bits */ + incq %r9 /* add 1: if one carry bit was *not* set + the addition will not result in 0. */ + + jnz 3f /* found NUL => return pointer */ + + movq %rax, (%rdx) /* Write value to destination. */ + addq $8, %rdx /* Adjust pointer. */ + + /* 4th unroll. */ + movq (%rsi), %rax /* Read double word (8 bytes). */ + addq $8, %rsi /* Adjust pointer for next word. */ + movq %rax, %r9 /* Save a copy for NUL finding. */ + addq %r8, %r9 /* add the magic value to the word. We get + carry bits reported for each byte which + is *not* 0 */ + jnc 3f /* highest byte is NUL => return pointer */ + xorq %rax, %r9 /* (word+magic)^word */ + orq %r8, %r9 /* set all non-carry bits */ + incq %r9 /* add 1: if one carry bit was *not* set + the addition will not result in 0. */ + + jnz 3f /* found NUL => return pointer */ + + movq %rax, (%rdx) /* Write value to destination. */ + addq $8, %rdx /* Adjust pointer. */ + jmp 1b /* Next iteration. */ + + /* Do the last few bytes. %rax contains the value to write. + The loop is unrolled twice. */ + .p2align 4 +3: + /* Note that stpcpy needs to return with the value of the NUL + byte. */ + movb %al, (%rdx) /* 1st byte. */ + testb %al, %al /* Is it NUL. */ + jz 4f /* yes, finish. */ + incq %rdx /* Increment destination. */ + movb %ah, (%rdx) /* 2nd byte. */ + testb %ah, %ah /* Is it NUL?. */ + jz 4f /* yes, finish. */ + incq %rdx /* Increment destination. */ + shrq $16, %rax /* Shift... */ + jmp 3b /* and look at next two bytes in %rax. */ + +4: +#ifdef USE_AS_STPCPY + movq %rdx, %rax /* Destination is return value. */ +#else + movq %rdi, %rax /* Source is return value. */ +#endif + retq +END (BP_SYM (STRCPY)) |