[tip:core/locking] x86, mem: Don't implement forward memmove() as memcpy()

[tip-bot for Ma, Ling]

Commit-ID:  fdf4289679fd41d76553ce224750e9737cd80eea
Gitweb:     http://git.kernel.org/tip/fdf4289679fd41d76553ce224750e9737cd80eea
Author:     Ma, Ling <ling.ma@xxxxxxxxx>
AuthorDate: Mon, 23 Aug 2010 14:11:12 -0700
Committer:  H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
CommitDate: Mon, 23 Aug 2010 14:14:27 -0700

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@xxxxxxxxx>
LKML-Reference: <C10D3FB0CD45994C8A51FEC1227CE22F0E483AD86A@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
---
 arch/x86/lib/memcpy_32.c  |   38 ++++++++++++++++++++++++++----------
 arch/x86/lib/memmove_64.c |   46 ++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 68 insertions(+), 16 deletions(-)

diff --git a/arch/x86/lib/memcpy_32.c b/arch/x86/lib/memcpy_32.c
index 5415a9d..be424df 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)
 	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);
diff --git a/arch/x86/lib/memmove_64.c b/arch/x86/lib/memmove_64.c
index 0a33909..ecacc4b 100644
--- a/arch/x86/lib/memmove_64.c
+++ b/arch/x86/lib/memmove_64.c
@@ -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;
 }
--
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