kolibrios/drivers/old/radeonhd/memset.asm

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/* 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