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Eliminate superfluous memory access in memcpy(3)/memmove(3).

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Obtained from:	NetBSD
MFC after:	1 week
This commit is contained in:
sobomax 2002-10-15 09:50:07 +00:00
parent fbb20002c7
commit 30e3020a42
1 changed files with 8 additions and 13 deletions
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21
lib/libc/i386/string/bcopy.S
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@ -59,27 +59,25 @@ ENTRY(bcopy)
#if defined(MEMCOPY) || defined(MEMMOVE)
movl 12(%esp),%edi
movl 16(%esp),%esi
movl %edi,%eax
#else
movl 12(%esp),%esi
movl 16(%esp),%edi
#endif
movl 20(%esp),%ecx
movl %edi,%eax
subl %esi,%eax
cmpl %ecx,%eax /* overlapping? */
movl %edi,%edx
subl %esi,%edx
cmpl %ecx,%edx /* overlapping? */
jb 1f
cld /* nope, copy forwards. */
movl %ecx,%eax
movl %ecx,%edx
shrl $2,%ecx /* copy by words */
rep
movsl
movl %eax,%ecx
movl %edx,%ecx
andl $3,%ecx /* any bytes left? */
rep
movsb
#if defined(MEMCOPY) || defined(MEMMOVE)
movl 12(%esp),%eax
#endif
popl %edi
popl %esi
ret
@ -87,21 +85,18 @@ ENTRY(bcopy)
addl %ecx,%edi /* copy backwards. */
addl %ecx,%esi
std
movl %ecx,%eax
movl %ecx,%edx
andl $3,%ecx /* any fractional bytes? */
decl %edi
decl %esi
rep
movsb
movl %eax,%ecx /* copy remainder by words */
movl %edx,%ecx /* copy remainder by words */
shrl $2,%ecx
subl $3,%esi
subl $3,%edi
rep
movsl
#if defined(MEMCOPY) || defined(MEMMOVE)
movl 12(%esp),%eax
#endif
popl %edi
popl %esi
cld