.file "memset.s"
#include <sys/asm_linkage.h>
ANSI_PRAGMA_WEAK(memset,function)
ENTRY(memset)
pushl %edi / save register variable
movl 8(%esp),%edi / %edi = string address
movl 12(%esp),%eax / %al = byte to duplicate
movl 16(%esp),%ecx / %ecx = number of copies
/ For all basic blocks in this routine, maintain the following
/ entry conditions: %eax each byte is set to desired byte.
/ NOTE: .byteset doesn't require this
/ %ecx contains # bytes to set
/ %edi contain address to set
cld / make sure we go the right way...
cmpl $20,%ecx / strings with fewer than 20 chars should be byte set
jbe .byteset
andl $0xff, %eax / trim anything above low byte
imul $0x01010101, %eax / extend low byte to each byte
cmpl $256, %ecx / smaller areas don't benefit from alignment
jbe .wordset
cmpl $511, %ecx / areas smaller than this should be wordset
jbe .check_wordset
/
/ prep work for sse temporal and non-temporal
/
pushl %ebx / more registers are needed
pushl %esi / for alignment work
/
/ align address to 64 byte boundaries.
/
movl %ecx, %ebx / save byte count
movl %edi, %esi / esi is scratch register
andl $63, %esi / bytes to align to 64 byte align addr
neg %esi / compute count of bytes
addl $64, %esi / needed to align
andl $63, %esi / to 64 byte align addr
jz .sse_aligned / skip alignment if not needed
subl %esi, %ebx / ebx contains remainder of bytes to set
movl %esi, %ecx / alignment bytes
shrl $2,%ecx / %ecx = number of words to set
rep; sstol
movl %esi,%ecx
andl $3,%ecx / %ecx = number of bytes left
rep; sstob
movl %ebx, %ecx / remainder to be set
.sse_aligned:
shr $6, %ecx / number of 64 byte blocks to set
/
/ load xmm0 with bytes to be set
/
subl $16,%esp / give ourselves some working room on the stack
movl %eax,(%esp) / copy eax into each of 4 bytes
movl %eax,4(%esp) / avoid pushl since it causes more interlocking
movl %eax,8(%esp) /
movl %eax,12(%esp) /
movups (%esp), %xmm0 / unaligned load from stack into xmm0
addl $16,%esp / restore stack position
cmpl $262143, %ebx / blocks smaller than this allocate in the cache
jbe .sse_loop
jmp .sse_nt_loop / branch across alignment nops
.align 16
.sse_nt_loop:
movntps %xmm0, (%edi) / block non-temporal store
movntps %xmm0, 16(%edi) / use sse rather than sse2
movntps %xmm0, 32(%edi) / so we work more places
movntps %xmm0, 48(%edi) /
addl $64, %edi / increment dest address
dec %ecx / dec count of blocks
jnz .sse_nt_loop / jump if not done
andl $63, %ebx / remainder of bytes to copy
movl %ebx, %ecx / ecx contains remainer of bytes to set
popl %esi / restore stack config
popl %ebx /
#if defined(_SSE2_INSN)
mfence
#elif defined(_SSE_INSN)
sfence
#else
#error "Must have either SSE or SSE2"
#endif
cmpl $20, %ecx / compare and jump accordingly
jbe .byteset
jmp .wordset
.align 16
.sse_loop:
movaps %xmm0, (%edi) / block copy w/ SSE
movaps %xmm0, 16(%edi)
movaps %xmm0, 32(%edi)
movaps %xmm0, 48(%edi)
addl $64, %edi / increment addr
dec %ecx / dec count of blocks
jnz .sse_loop / jump if not done
andl $63, %ebx / remainder of bytes to copy
movl %ebx, %ecx / in %ecx as normal
popl %esi / restore stack config
popl %ebx /
cmpl $20, %ecx
jbe .byteset
jmp .wordset
.check_wordset:
movl %edi, %edx / save current store ptr
andl $7, %edi / check alignment
movl %edx,%edi / %edi = string address
jz .wordset / all ok
.align_wordset:
pushl %ebx / more registers are needed
pushl %esi
movl %ecx, %ebx
movl %edi, %esi
andl $7, %esi
neg %esi
addl $8, %esi
andl $7, %esi
subl %esi, %ebx / ebx contains remainder of bytes to copy
movl %esi, %ecx
rep; sstob
movl %ebx, %ecx
popl %esi / restore stack config
popl %ebx /
.wordset:
movl %ecx, %edx / save cont
shrl $2,%ecx / %ecx = number of words to set
rep; sstol
movl %edx,%ecx
andl $3,%ecx / %ecx = number of bytes left
.byteset:
rep; sstob
movl 8(%esp),%eax / return string address
popl %edi / restore register variable
ret
SET_SIZE(memset)
