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authorMa, Ling <ling.ma@intel.com>2010-08-23 17:11:12 -0400
committerH. Peter Anvin <hpa@linux.intel.com>2010-08-23 17:14:27 -0400
commitfdf4289679fd41d76553ce224750e9737cd80eea (patch)
tree6191ed574019b3f22e6d283dde0108517fe62f8f /arch/x86/lib/memcpy_32.c
parent76be97c1fc945db08aae1f1b746012662d643e97 (diff)
x86, mem: Don't implement forward memmove() as memcpy()
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>
Diffstat (limited to 'arch/x86/lib/memcpy_32.c')
-rw-r--r--arch/x86/lib/memcpy_32.c38
1 files changed, 27 insertions, 11 deletions
diff --git a/arch/x86/lib/memcpy_32.c b/arch/x86/lib/memcpy_32.c
index 5415a9d06f53..be424dfcf365 100644
--- a/arch/x86/lib/memcpy_32.c
+++ b/arch/x86/lib/memcpy_32.c
@@ -25,19 +25,35 @@ void *memmove(void *dest, const void *src, size_t n)
25 int d0, d1, d2; 25 int d0, d1, d2;
26 26
27 if (dest < src) { 27 if (dest < src) {
28 memcpy(dest, src, n); 28 if ((dest + n) < src)
29 return memcpy(dest, src, n);
30 else
31 __asm__ __volatile__(
32 "rep\n\t"
33 "movsb\n\t"
34 : "=&c" (d0), "=&S" (d1), "=&D" (d2)
35 :"0" (n),
36 "1" (src),
37 "2" (dest)
38 :"memory");
39
29 } else { 40 } else {
30 __asm__ __volatile__( 41
31 "std\n\t" 42 if((src + count) < dest)
32 "rep\n\t" 43 return memcpy(dest, src, count);
33 "movsb\n\t" 44 else
34 "cld" 45 __asm__ __volatile__(
35 : "=&c" (d0), "=&S" (d1), "=&D" (d2) 46 "std\n\t"
36 :"0" (n), 47 "rep\n\t"
37 "1" (n-1+src), 48 "movsb\n\t"
38 "2" (n-1+dest) 49 "cld"
39 :"memory"); 50 : "=&c" (d0), "=&S" (d1), "=&D" (d2)
51 :"0" (n),
52 "1" (n-1+src),
53 "2" (n-1+dest)
54 :"memory");
40 } 55 }
56
41 return dest; 57 return dest;
42} 58}
43EXPORT_SYMBOL(memmove); 59EXPORT_SYMBOL(memmove);