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/* Optimized memset implementation for POWER10 LE.
Copyright (C) 2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <sysdep.h>
/* void * [r3] memset (void *s [r3], int c [r4], size_t n [r5]));
Returns 's'. */
#ifndef MEMSET
# define MEMSET memset
#endif
.machine power9
ENTRY_TOCLESS (MEMSET, 5)
CALL_MCOUNT 3
L(_memset):
/* Assume memset of zero length is uncommon, and just let it go
through the small path below. */
cmpldi r5,64
/* Replicate byte to quad word. */
mtvsrd v0+32,r4
vspltb v0,v0,7
li r7,16
sldi r8,r7,56
bgt L(large)
/* For short lengths we want to avoid as many branches as possible.
We use store VSX vector with length instructions to do this.
It takes advantage of the fact that if the length passed to stxvl
is zero nothing is done, effectively a no-op. */
sldi r5,r5,56
addi r10,r3,16
sub. r11,r5,r8
isellt r11,0,r11 /* Saturate the subtraction to zero. */
stxvl v0+32,r3,r5
stxvl v0+32,r10,r11
addi r9,r3,32
addi r10,r3,48
sub. r11,r11,r8
isellt r11,0,r11
sub. r5,r11,r8
isellt r5,0,r5
stxvl v0+32,r9,r11
stxvl v0+32,r10,r5
blr
.balign 16
L(large):
mr r6,r3 /* Don't modify r3 since we need to return it. */
/* Get dest 16B aligned. */
neg r0,r3
clrldi. r7,r0,(64-4)
beq L(aligned)
rldic r9,r0,56,4 /* (~X & 0xf)<<56 "clrlsldi r9,r0,64-4,56". */
stxvl v0+32,r6,r9 /* Store up to 15B until aligned address. */
add r6,r6,r7
sub r5,r5,r7
/* Go to tail if there is less than 64B left after alignment. */
cmpldi r5,64
blt L(tail_64)
.balign 16
L(aligned):
/* Go to tail if there is less than 128B left after alignment. */
srdi. r0,r5,7
beq L(tail_128)
/* If c == 0 && n >= 256 use dcbz to zero out full cache blocks. */
cmpldi cr5,r5,255
cmpldi cr6,r4,0
crand 27,26,21
bt 27,L(dcbz)
mtctr r0
.balign 32
L(loop):
stxv v0+32,0(r6)
stxv v0+32,16(r6)
stxv v0+32,32(r6)
stxv v0+32,48(r6)
stxv v0+32,64(r6)
stxv v0+32,80(r6)
stxv v0+32,96(r6)
stxv v0+32,112(r6)
addi r6,r6,128
bdnz L(loop)
.balign 16
L(tail):
/* 127B or less left, finish the tail or return. */
andi. r5,r5,127
beqlr
cmpldi r5,64
blt L(tail_64)
.balign 16
L(tail_128):
/* Stores a minimum of 64B and up to 128B and return. */
stxv v0+32,0(r6)
stxv v0+32,16(r6)
stxv v0+32,32(r6)
stxv v0+32,48(r6)
addi r6,r6,64
andi. r5,r5,63
beqlr
.balign 16
L(tail_64):
/* Stores up to 64B and return. */
sldi r5,r5,56
addi r10,r6,16
sub. r11,r5,r8
isellt r11,0,r11
stxvl v0+32,r6,r5
stxvl v0+32,r10,r11
sub. r11,r11,r8
blelr
addi r9,r6,32
addi r10,r6,48
isellt r11,0,r11
sub. r5,r11,r8
isellt r5,0,r5
stxvl v0+32,r9,r11
stxvl v0+32,r10,r5
blr
.balign 16
L(dcbz):
/* Special case when value is 0 and we have a long length to deal
with. Use dcbz to zero out a full cacheline of 128 bytes at a time.
Before using dcbz though, we need to get the destination 128-byte
aligned. */
neg r0,r6
clrldi. r0,r0,(64-7)
beq L(dcbz_aligned)
sub r5,r5,r0
mtocrf 0x2,r0 /* copying bits 57..59 to cr6. The ones for sizes 64,
32 and 16 which need to be checked. */
/* Write 16-128 bytes until DST is aligned to 128 bytes. */
64: bf 25,32f
stxv v0+32,0(r6)
stxv v0+32,16(r6)
stxv v0+32,32(r6)
stxv v0+32,48(r6)
addi r6,r6,64
32: bf 26,16f
stxv v0+32,0(r6)
stxv v0+32,16(r6)
addi r6,r6,32
16: bf 27,L(dcbz_aligned)
stxv v0+32,0(r6)
addi r6,r6,16
.balign 16
L(dcbz_aligned):
/* Setup dcbz unroll offsets and count numbers. */
srdi. r0,r5,9
li r9,128
beq L(bcdz_tail)
li r10,256
li r11,384
mtctr r0
.balign 16
L(dcbz_loop):
/* Sets 512 bytes to zero in each iteration, the loop unrolling shows
a throughput boost for large sizes (2048 bytes or higher). */
dcbz 0,r6
dcbz r9,r6
dcbz r10,r6
dcbz r11,r6
addi r6,r6,512
bdnz L(dcbz_loop)
andi. r5,r5,511
beqlr
.balign 16
L(bcdz_tail):
/* We have 1-511 bytes remaining. */
srdi. r0,r5,7
beq L(tail)
mtocrf 0x1,r0
256: bf 30,128f
dcbz 0,r6
dcbz r9,r6
addi r6,r6,256
128: bf 31,L(tail)
dcbz 0,r6
addi r6,r6,128
b L(tail)
END_GEN_TB (MEMSET,TB_TOCLESS)
libc_hidden_builtin_def (memset)
/* Copied from bzero.S to prevent the linker from inserting a stub
between bzero and memset. */
ENTRY_TOCLESS (__bzero)
CALL_MCOUNT 2
mr r5,r4
li r4,0
b L(_memset)
END (__bzero)
#ifndef __bzero
weak_alias (__bzero, bzero)
#endif
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