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Commit fdf42896 authored by Ma, Ling's avatar Ma, Ling Committed by H. Peter Anvin
Browse files

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: default avatarMa Ling <ling.ma@intel.com>
LKML-Reference: <C10D3FB0CD45994C8A51FEC1227CE22F0E483AD86A@shsmsx502.ccr.corp.intel.com>
Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
parent 76be97c1

arch/x86/lib/memcpy_32.c

+27 −11
Original line number Diff line number Diff line
@@ -25,8 +25,23 @@ 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 {



		if((src + count) < dest)

			return memcpy(dest, src, count);

		else

			__asm__ __volatile__(

				"std\n\t"

				"rep\n\t"
@@ -38,6 +53,7 @@ void *memmove(void *dest, const void *src, size_t n) 
				 "2" (n-1+dest)

				:"memory");

	}



	return dest;

}

EXPORT_SYMBOL(memmove);

arch/x86/lib/memmove_64.c

+41 −5
Original line number Diff line number Diff line
@@ -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) {

		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;

}