fdf4289679
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>
57 lines
1.2 KiB
C
57 lines
1.2 KiB
C
/* Normally compiler builtins are used, but sometimes the compiler calls out
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of line code. Based on asm-i386/string.h.
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*/
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#define _STRING_C
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#include <linux/string.h>
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#include <linux/module.h>
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#undef memmove
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void *memmove(void *dest, const void *src, size_t count)
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{
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unsigned long d0, d1, d2, d3;
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if (dest < src) {
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if ((dest + count) < src)
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return memcpy(dest, src, count);
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else
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__asm__ __volatile__(
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"movq %0, %3\n\t"
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"shr $3, %0\n\t"
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"andq $7, %3\n\t"
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"rep\n\t"
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"movsq\n\t"
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"movq %3, %0\n\t"
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"rep\n\t"
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"movsb"
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: "=&c" (d0), "=&S" (d1), "=&D" (d2), "=r" (d3)
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:"0" (count),
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"1" (src),
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"2" (dest)
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:"memory");
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} else {
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if((src + count) < dest)
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return memcpy(dest, src, count);
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else
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__asm__ __volatile__(
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"movq %0, %3\n\t"
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"lea -8(%1, %0), %1\n\t"
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"lea -8(%2, %0), %2\n\t"
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"shr $3, %0\n\t"
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"andq $7, %3\n\t"
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"std\n\t"
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"rep\n\t"
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"movsq\n\t"
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"lea 7(%1), %1\n\t"
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"lea 7(%2), %2\n\t"
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"movq %3, %0\n\t"
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"rep\n\t"
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"movsb\n\t"
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"cld"
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: "=&c" (d0), "=&S" (d1), "=&D" (d2), "=r" (d3)
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:"0" (count),
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"1" (src),
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"2" (dest)
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:"memory");
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}
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return dest;
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}
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EXPORT_SYMBOL(memmove);
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