| 1,67 → 1,60 |
|---|
| # _memmove() Author: Kees J. Bot 2 Jan 1994 |
| /* _memmove() Author: Kees J. Bot */ |
| /* 2 Jan 1994 */ |
| |
| # void *_memmove(void *s1, const void *s2, size_t n) |
| # Copy a chunk of memory. Handle overlap. |
| /* void *_memmove(void *s1, const void *s2, size_t n) */ |
| /* Copy a chunk of memory. Handle overlap. */ |
| /* */ |
| |
| .intel_syntax |
| #include "asm.h" |
| |
| .globl __memmove, __memcpy |
| ENTRY(_memmove) |
| push %ebp |
| movl %esp, %ebp |
| push %esi |
| push %edi |
| movl 8(%ebp), %edi /* String s1 */ |
| movl 12(%ebp), %esi /* String s2 */ |
| movl 16(%ebp), %ecx /* Length */ |
| movl %edi, %eax |
| subl %esi, %eax |
| cmpl %ecx, %eax |
| jb downwards /* if (s2 - s1) < n then copy downwards */ |
| LABEL(_memcpy) |
| cld /* Clear direction bit: upwards */ |
| cmpl $16, %ecx |
| jb upbyte /* Don't bother being smart with short arrays */ |
| movl %esi, %eax |
| orl %edi, %eax |
| testb $1, %al |
| jne upbyte /* Bit 0 set, use byte copy */ |
| testb $2, %al |
| jne upword /* Bit 1 set, use word copy */ |
| uplword: |
| shrdl $2, %ecx, %eax /* Save low 2 bits of ecx in eax */ |
| shrl $2, %ecx |
| |
| .text |
| rep movsl /* Copy longwords. */ |
| shldl $2, %eax, %ecx /* Restore excess count */ |
| upword: |
| shrl $1, %ecx |
| |
| .align 16 |
| __memmove: |
| push ebp |
| mov ebp, esp |
| |
| push esi |
| push edi |
| |
| mov edi, [ebp+8] # String s1 |
| mov esi, [ebp+12] # String s2 |
| mov ecx, [ebp+16] # Length |
| |
| mov eax, edi |
| sub eax, esi |
| cmp eax, ecx |
| jb downwards # if (s2 - s1) < n then copy downwards |
| __memcpy: |
| cld # Clear direction bit: upwards |
| cmp ecx, 16 |
| jb upbyte # Don't bother being smart with short arrays |
| |
| mov eax, esi |
| or eax, edi |
| testb al, 1 |
| jnz upbyte # Bit 0 set, use byte copy |
| |
| testb al, 2 |
| |
| jnz upword # Bit 1 set, use word copy |
| uplword: |
| shrd eax, ecx, 2 # Save low 2 bits of ecx in eax |
| shr ecx, 2 |
| rep movsd # Copy longwords. |
| shld ecx, eax, 2 # Restore excess count |
| upword: |
| shr ecx, 1 |
| rep movsw # Copy words |
| adc ecx, ecx # One more byte? |
| rep movsw /* Copy words */ |
| adcl %ecx, %ecx /* One more byte? */ |
| upbyte: |
| rep movsb # Copy bytes |
| rep movsb /* Copy bytes */ |
| done: |
| mov eax, [ebp+8] # Absolutely noone cares about this value |
| pop edi |
| pop esi |
| pop ebp |
| movl 8(%ebp), %eax /* Absolutely noone cares about this value */ |
| pop %edi |
| pop %esi |
| pop %ebp |
| ret |
| |
| # Handle bad overlap by copying downwards, don't bother to do word copies. |
| /* Handle bad overlap by copying downwards, don't bother to do word copies. */ |
| downwards: |
| std /* Set direction bit: downwards */ |
| leal -1(%esi,%ecx,1), %esi |
| leal -1(%edi,%ecx,1), %edi |
| |
| downwards: |
| std # Set direction bit: downwards |
| lea esi, [esi+ecx-1] |
| lea edi, [edi+ecx-1] |
| rep movsb # Copy bytes |
| rep movsb /* Copy bytes */ |
| cld |
| jmp done |