NetBSD/lib/libc/arch/x86_64/string/strcpy.S

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/*
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* Written by J.T. Conklin <jtc@NetBSD.org>.
* Public domain.
* Adapted for NetBSD/x86_64 by Frank van der Linden <fvdl@wasabisystems.com>
*/
#include <machine/asm.h>
#if defined(LIBC_SCCS)
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RCSID("$NetBSD: strcpy.S,v 1.2 2003/07/26 19:24:40 salo Exp $")
#endif
/*
* NOTE: I've unrolled the loop eight times: large enough to make a
* significant difference, and small enough not to totally trash the
* cache.
*/
ENTRY(strcpy)
movq %rdi,%r11
L1: movb (%rsi),%al /* unroll loop, but not too much */
movb %al,(%rdi)
testb %al,%al
jz L2
movb 1(%rsi),%al
movb %al,1(%rdi)
testb %al,%al
jz L2
movb 2(%rsi),%al
movb %al,2(%rdi)
testb %al,%al
jz L2
movb 3(%rsi),%al
movb %al,3(%rdi)
testb %al,%al
jz L2
movb 4(%rsi),%al
movb %al,4(%rdi)
testb %al,%al
jz L2
movb 5(%rsi),%al
movb %al,5(%rdi)
testb %al,%al
jz L2
movb 6(%rsi),%al
movb %al,6(%rdi)
testb %al,%al
jz L2
movb 7(%rsi),%al
movb %al,7(%rdi)
addq $8,%rsi
addq $8,%rdi
testb %al,%al
jnz L1
L2: movq %r11,%rax
ret