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/* Copyright (C) 1996-2024 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/>. */
/* Fill a block of memory with a character. Optimized for the Alpha
architecture:
- memory accessed as aligned quadwords only
- destination memory not read unless needed for good cache behaviour
- basic blocks arranged to optimize branch prediction for full-quadword
aligned memory blocks.
- partial head and tail quadwords constructed with byte-mask instructions
This is generally scheduled for the EV5 (got to look out for my own
interests :-), but with EV4 needs in mind. There *should* be no more
stalls for the EV4 than there are for the EV5.
*/
#include <sysdep.h>
.set noat
.set noreorder
.text
.type memset, @function
.globl memset
.usepv memset, USEPV_PROF
cfi_startproc
/* On entry to this basic block:
t3 == loop counter
t4 == bytes in partial final word
a0 == possibly misaligned destination pointer
a1 == replicated source character */
.align 3
memset_loop:
beq t3, $tail
blbc t3, 0f # skip single store if count even
stq_u a1, 0(a0) # e0 : store one word
subq t3, 1, t3 # .. e1 :
addq a0, 8, a0 # e0 :
beq t3, $tail # .. e1 :
0: stq_u a1, 0(a0) # e0 : store two words
subq t3, 2, t3 # .. e1 :
stq_u a1, 8(a0) # e0 :
addq a0, 16, a0 # .. e1 :
bne t3, 0b # e1 :
$tail: bne t4, 1f # is there a tail to do?
ret # no
.align 3
1: ldq_u t0, 0(a0) # e1 : yes, load original data
mskql a1, t4, t1 # .. e0 :
mskqh t0, t4, t0 # e0 :
or t0, t1, t0 # e1 (stall)
stq_u t0, 0(a0) # e0 :
ret # .. e1 :
memset:
#ifdef PROF
ldgp gp, 0(pv)
lda AT, _mcount
jsr AT, (AT), _mcount
#endif
and a1, 0xff, a1 # e0 : zero extend input character
mov a0, v0 # .. e1 : move return value in place
sll a1, 8, t0 # e0 : begin replicating the char
beq a2, $done # .. e1 : early exit for zero-length store
or t0, a1, a1 # e0 :
and a0, 7, t1 # .. e1 : dest misalignment
sll a1, 16, t0 # e0 :
addq a2, t1, a2 # .. e1 : add dest misalignment to count
or t0, a1, a1 # e0 :
srl a2, 3, t3 # .. e1 : loop = count >> 3
sll a1, 32, t0 # e0 :
and a2, 7, t4 # .. e1 : find number of bytes in tail
or t0, a1, a1 # e0 : character replication done
beq t1, memset_loop # .. e1 : aligned head, jump right in
ldq_u t0, 0(a0) # e1 : load original data to mask into
mskqh a1, a0, t1 # .. e0 :
cmpult a2, 8, t2 # e0 : is this a sub-word set?
bne t2, $oneq # .. e1 (zdb)
mskql t0, a0, t0 # e0 : we span words. finish this partial
subq t3, 1, t3 # .. e1 :
addq a0, 8, a0 # e0 :
or t0, t1, t0 # .. e1 :
stq_u t0, -8(a0) # e0 :
br memset_loop # .. e1 :
.align 3
$oneq:
mskql t1, a2, t1 # e0 : entire operation within one word
mskql t0, a0, t2 # e0 :
mskqh t0, a2, t3 # e0 :
or t1, t2, t0 # .. e1 :
or t0, t3, t0 # e1 :
stq_u t0, 0(a0) # e0 (stall)
$done: ret
cfi_endproc
libc_hidden_builtin_def (memset)
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