60 lines
1.4 KiB
ArmAsm
60 lines
1.4 KiB
ArmAsm
/* _memmove() Author: Kees J. Bot */
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/* 2 Jan 1994 */
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/* void *_memmove(void *s1, const void *s2, size_t n) */
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/* Copy a chunk of memory. Handle overlap. */
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/* */
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#include <machine/asm.h>
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ENTRY(_memmove)
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push %ebp
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movl %esp, %ebp
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push %esi
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push %edi
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movl 8(%ebp), %edi /* String s1 */
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movl 12(%ebp), %esi /* String s2 */
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movl 16(%ebp), %ecx /* Length */
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movl %edi, %eax
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subl %esi, %eax
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cmpl %ecx, %eax
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jb downwards /* if (s2 - s1) < n then copy downwards */
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LABEL(_memcpy)
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cld /* Clear direction bit: upwards */
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cmpl $16, %ecx
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jb upbyte /* Don't bother being smart with short arrays */
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movl %esi, %eax
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orl %edi, %eax
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testb $1, %al
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jne upbyte /* Bit 0 set, use byte copy */
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testb $2, %al
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jne upword /* Bit 1 set, use word copy */
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uplword:
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shrdl $2, %ecx, %eax /* Save low 2 bits of ecx in eax */
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shrl $2, %ecx
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rep movsl /* Copy longwords. */
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shldl $2, %eax, %ecx /* Restore excess count */
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upword:
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shrl $1, %ecx
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rep movsw /* Copy words */
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adcl %ecx, %ecx /* One more byte? */
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upbyte:
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rep movsb /* Copy bytes */
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done:
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movl 8(%ebp), %eax /* Absolutely noone cares about this value */
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pop %edi
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pop %esi
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pop %ebp
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ret
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/* Handle bad overlap by copying downwards, don't bother to do word copies. */
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downwards:
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std /* Set direction bit: downwards */
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leal -1(%esi,%ecx,1), %esi
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leal -1(%edi,%ecx,1), %edi
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rep movsb /* Copy bytes */
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cld
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jmp done
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