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x86: Add an accelerated memmove() function

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Bring in a faster memmove() from Linux 4.7. This speeds up scrolling on the
display.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
This commit is contained in:
Simon Glass 2016-10-05 20:42:10 -06:00 committed by Bin Meng
parent 26f50fbed2
commit a5b8722532
2 changed files with 162 additions and 1 deletions
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2
arch/x86/include/asm/string.h
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@ -17,7 +17,7 @@ extern char * strchr(const char * s, int c);
#define __HAVE_ARCH_MEMCPY
extern void * memcpy(void *, const void *, __kernel_size_t);
#undef __HAVE_ARCH_MEMMOVE
#define __HAVE_ARCH_MEMMOVE
extern void * memmove(void *, const void *, __kernel_size_t);
#undef __HAVE_ARCH_MEMCHR

161
arch/x86/lib/string.c
View file

@ -130,3 +130,164 @@ void *memcpy(void *dstpp, const void *srcpp, size_t len)
return dstpp;
}
void *memmove(void *dest, const void *src, size_t n)
{
int d0, d1, d2, d3, d4, d5;
char *ret = dest;
__asm__ __volatile__(
/* Handle more 16 bytes in loop */
"cmp $0x10, %0\n\t"
"jb 1f\n\t"
/* Decide forward/backward copy mode */
"cmp %2, %1\n\t"
"jb 2f\n\t"
/*
* movs instruction have many startup latency
* so we handle small size by general register.
*/
"cmp $680, %0\n\t"
"jb 3f\n\t"
/* movs instruction is only good for aligned case */
"mov %1, %3\n\t"
"xor %2, %3\n\t"
"and $0xff, %3\n\t"
"jz 4f\n\t"
"3:\n\t"
"sub $0x10, %0\n\t"
/* We gobble 16 bytes forward in each loop */
"3:\n\t"
"sub $0x10, %0\n\t"
"mov 0*4(%1), %3\n\t"
"mov 1*4(%1), %4\n\t"
"mov %3, 0*4(%2)\n\t"
"mov %4, 1*4(%2)\n\t"
"mov 2*4(%1), %3\n\t"
"mov 3*4(%1), %4\n\t"
"mov %3, 2*4(%2)\n\t"
"mov %4, 3*4(%2)\n\t"
"lea 0x10(%1), %1\n\t"
"lea 0x10(%2), %2\n\t"
"jae 3b\n\t"
"add $0x10, %0\n\t"
"jmp 1f\n\t"
/* Handle data forward by movs */
".p2align 4\n\t"
"4:\n\t"
"mov -4(%1, %0), %3\n\t"
"lea -4(%2, %0), %4\n\t"
"shr $2, %0\n\t"
"rep movsl\n\t"
"mov %3, (%4)\n\t"
"jmp 11f\n\t"
/* Handle data backward by movs */
".p2align 4\n\t"
"6:\n\t"
"mov (%1), %3\n\t"
"mov %2, %4\n\t"
"lea -4(%1, %0), %1\n\t"
"lea -4(%2, %0), %2\n\t"
"shr $2, %0\n\t"
"std\n\t"
"rep movsl\n\t"
"mov %3,(%4)\n\t"
"cld\n\t"
"jmp 11f\n\t"
/* Start to prepare for backward copy */
".p2align 4\n\t"
"2:\n\t"
"cmp $680, %0\n\t"
"jb 5f\n\t"
"mov %1, %3\n\t"
"xor %2, %3\n\t"
"and $0xff, %3\n\t"
"jz 6b\n\t"
/* Calculate copy position to tail */
"5:\n\t"
"add %0, %1\n\t"
"add %0, %2\n\t"
"sub $0x10, %0\n\t"
/* We gobble 16 bytes backward in each loop */
"7:\n\t"
"sub $0x10, %0\n\t"
"mov -1*4(%1), %3\n\t"
"mov -2*4(%1), %4\n\t"
"mov %3, -1*4(%2)\n\t"
"mov %4, -2*4(%2)\n\t"
"mov -3*4(%1), %3\n\t"
"mov -4*4(%1), %4\n\t"
"mov %3, -3*4(%2)\n\t"
"mov %4, -4*4(%2)\n\t"
"lea -0x10(%1), %1\n\t"
"lea -0x10(%2), %2\n\t"
"jae 7b\n\t"
/* Calculate copy position to head */
"add $0x10, %0\n\t"
"sub %0, %1\n\t"
"sub %0, %2\n\t"
/* Move data from 8 bytes to 15 bytes */
".p2align 4\n\t"
"1:\n\t"
"cmp $8, %0\n\t"
"jb 8f\n\t"
"mov 0*4(%1), %3\n\t"
"mov 1*4(%1), %4\n\t"
"mov -2*4(%1, %0), %5\n\t"
"mov -1*4(%1, %0), %1\n\t"
"mov %3, 0*4(%2)\n\t"
"mov %4, 1*4(%2)\n\t"
"mov %5, -2*4(%2, %0)\n\t"
"mov %1, -1*4(%2, %0)\n\t"
"jmp 11f\n\t"
/* Move data from 4 bytes to 7 bytes */
".p2align 4\n\t"
"8:\n\t"
"cmp $4, %0\n\t"
"jb 9f\n\t"
"mov 0*4(%1), %3\n\t"
"mov -1*4(%1, %0), %4\n\t"
"mov %3, 0*4(%2)\n\t"
"mov %4, -1*4(%2, %0)\n\t"
"jmp 11f\n\t"
/* Move data from 2 bytes to 3 bytes */
".p2align 4\n\t"
"9:\n\t"
"cmp $2, %0\n\t"
"jb 10f\n\t"
"movw 0*2(%1), %%dx\n\t"
"movw -1*2(%1, %0), %%bx\n\t"
"movw %%dx, 0*2(%2)\n\t"
"movw %%bx, -1*2(%2, %0)\n\t"
"jmp 11f\n\t"
/* Move data for 1 byte */
".p2align 4\n\t"
"10:\n\t"
"cmp $1, %0\n\t"
"jb 11f\n\t"
"movb (%1), %%cl\n\t"
"movb %%cl, (%2)\n\t"
".p2align 4\n\t"
"11:"
: "=&c" (d0), "=&S" (d1), "=&D" (d2),
"=r" (d3), "=r" (d4), "=r"(d5)
: "0" (n),
"1" (src),
"2" (dest)
: "memory");
return ret;
}