x86: Add an accelerated memmove() function

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>

diff --git a/arch/x86/include/asm/string.h b/arch/x86/include/asm/string.h
index 0ad612f6273af9be2e0137681076ab6f1bb4bef9..38afd236843a6cc95a442ed4c690211b1d59fab7 100644 (file)
--- a/arch/x86/include/asm/string.h
+++ b/arch/x86/include/asm/string.h
@@ -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

diff --git a/arch/x86/lib/string.c b/arch/x86/lib/string.c
index 6c66431ed93b3d4943954f0e07a04a0acf665c77..5343c2b6fd5b06ed4e2818bc014e2972cb698a11 100644 (file)
--- a/arch/x86/lib/string.c
+++ b/arch/x86/lib/string.c
@@ -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;
+}