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x86, mem: Don't implement forward memmove() as memcpy()

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memmove() allow source and destination address to be overlap, but
there is no such limitation for memcpy().  Therefore, explicitly
implement memmove() in both the forwards and backward directions, to
give us the ability to optimize memcpy().

Signed-off-by: Ma Ling <ling.ma@intel.com>
LKML-Reference: <C10D3FB0CD45994C8A51FEC1227CE22F0E483AD86A@shsmsx502.ccr.corp.intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
Ma, Ling 2010-08-23 14:11:12 -07:00 committed by H. Peter Anvin
parent 76be97c1fc
commit fdf4289679
2 changed files with 68 additions and 16 deletions
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38
arch/x86/lib/memcpy_32.c
View file

@ -25,19 +25,35 @@ void *memmove(void *dest, const void *src, size_t n)
int d0, d1, d2;
if (dest < src) {
memcpy(dest, src, n);
if ((dest + n) < src)
return memcpy(dest, src, n);
else
__asm__ __volatile__(
"rep\n\t"
"movsb\n\t"
: "=&c" (d0), "=&S" (d1), "=&D" (d2)
:"0" (n),
"1" (src),
"2" (dest)
:"memory");
} else {
__asm__ __volatile__(
"std\n\t"
"rep\n\t"
"movsb\n\t"
"cld"
: "=&c" (d0), "=&S" (d1), "=&D" (d2)
:"0" (n),
"1" (n-1+src),
"2" (n-1+dest)
:"memory");
if((src + count) < dest)
return memcpy(dest, src, count);
else
__asm__ __volatile__(
"std\n\t"
"rep\n\t"
"movsb\n\t"
"cld"
: "=&c" (d0), "=&S" (d1), "=&D" (d2)
:"0" (n),
"1" (n-1+src),
"2" (n-1+dest)
:"memory");
}
return dest;
}
EXPORT_SYMBOL(memmove);

46
arch/x86/lib/memmove_64.c
View file

@ -8,13 +8,49 @@
#undef memmove
void *memmove(void *dest, const void *src, size_t count)
{
unsigned long d0, d1, d2, d3;
if (dest < src) {
return memcpy(dest, src, count);
if ((dest + count) < src)
return memcpy(dest, src, count);
else
__asm__ __volatile__(
"movq %0, %3\n\t"
"shr $3, %0\n\t"
"andq $7, %3\n\t"
"rep\n\t"
"movsq\n\t"
"movq %3, %0\n\t"
"rep\n\t"
"movsb"
: "=&c" (d0), "=&S" (d1), "=&D" (d2), "=r" (d3)
:"0" (count),
"1" (src),
"2" (dest)
:"memory");
} else {
char *p = dest + count;
const char *s = src + count;
while (count--)
*--p = *--s;
if((src + count) < dest)
return memcpy(dest, src, count);
else
__asm__ __volatile__(
"movq %0, %3\n\t"
"lea -8(%1, %0), %1\n\t"
"lea -8(%2, %0), %2\n\t"
"shr $3, %0\n\t"
"andq $7, %3\n\t"
"std\n\t"
"rep\n\t"
"movsq\n\t"
"lea 7(%1), %1\n\t"
"lea 7(%2), %2\n\t"
"movq %3, %0\n\t"
"rep\n\t"
"movsb\n\t"
"cld"
: "=&c" (d0), "=&S" (d1), "=&D" (d2), "=r" (d3)
:"0" (count),
"1" (src),
"2" (dest)
:"memory");
}
return dest;
}