From fdf4289679fd41d76553ce224750e9737cd80eea Mon Sep 17 00:00:00 2001
From: "Ma, Ling" <ling.ma@intel.com>
Date: Mon, 23 Aug 2010 14:11:12 -0700
Subject: [PATCH] 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>
---
 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 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)
 	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 0a33909bf122..ecacc4b3d9e5 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;
 }