59 lines
1.3 KiB
ArmAsm
59 lines
1.3 KiB
ArmAsm
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! _memmove() Author: Kees J. Bot
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! 2 Jan 1994
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.sect .text; .sect .rom; .sect .data; .sect .bss
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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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.sect .text
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.define __memmove, __memcpy
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.align 16
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__memmove:
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push ebp
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mov ebp, esp
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push esi
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push edi
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mov edi, 8(ebp) ! String s1
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mov esi, 12(ebp) ! String s2
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mov ecx, 16(ebp) ! Length
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mov eax, edi
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sub eax, esi
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cmp eax, ecx
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jb downwards ! if (s2 - s1) < n then copy downwards
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__memcpy:
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cld ! Clear direction bit: upwards
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cmp ecx, 16
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jb upbyte ! Don't bother being smart with short arrays
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mov eax, esi
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or eax, edi
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testb al, 1
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jnz upbyte ! Bit 0 set, use byte copy
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testb al, 2
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jnz upword ! Bit 1 set, use word copy
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uplword:shrd eax, ecx, 2 ! Save low 2 bits of ecx in eax
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shr ecx, 2
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rep
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movs ! Copy longwords.
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shld ecx, eax, 2 ! Restore excess count
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upword: shr ecx, 1
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rep
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o16 movs ! Copy words
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adc ecx, ecx ! One more byte?
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upbyte: rep
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movsb ! Copy bytes
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done: mov eax, 8(ebp) ! 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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lea esi, -1(esi)(ecx*1)
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lea edi, -1(edi)(ecx*1)
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rep
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movsb ! Copy bytes
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cld
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jmp done
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