| 0,0 → 1,52 |
|---|
| /* Copyright (C) 1995 DJ Delorie, see COPYING.DJ for details */ |
| ##include<libc/asm.h> |
| # .file "memset.s" |
| .text |
| .global _memset |
| .align 4 |
| _memset: |
| pushl %ebp |
| movl %esp,%ebp |
| pushl %edi |
| movl 8(%ebp),%edi |
| movl 12(%ebp),%eax |
| movl 16(%ebp),%ecx |
| cld |
| |
| # We will handle memsets of <= 15 bytes one byte at a time. |
| # This avoids some extra overhead for small memsets, and |
| # knowing we are setting > 15 bytes eliminates some annoying |
| # checks in the "long move" case. |
| cmpl $15,%ecx |
| jle L3 |
| |
| # Otherwise, tile the byte value out into %eax. |
| # 0x41 -> 0x41414141, etc. |
| movb %al,%ah |
| movl %eax,%edx |
| sall $16,%eax |
| movw %dx,%ax |
| jmp L2 |
| |
| # Handle any cruft necessary to get %edi long-aligned. |
| L1: stosb |
| decl %ecx |
| L2: testl $3,%edi |
| jnz L1 |
| |
| # Now slam out all of the longs. |
| movl %ecx,%edx |
| shrl $2,%ecx |
| rep |
| stosl |
| |
| # Finally, handle any trailing cruft. We know the high three bytes |
| # of %ecx must be zero, so just put the "slop count" in the low byte. |
| movb %dl,%cl |
| andb $3,%cl |
| L3: rep |
| stosb |
| popl %edi |
| movl 8(%ebp),%eax |
| leave |
| ret |