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/* Copyright (C) 2000-2023 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>
.arch ev6
.set noat
.set noreorder
ENTRY(memset)
#ifdef PROF
ldgp gp, 0(pv)
lda AT, _mcount
jsr AT, (AT), _mcount
.prologue 1
#else
.prologue 0
#endif
/*
* Serious stalling happens. The only way to mitigate this is to
* undertake a major re-write to interleave the constant materialization
* with other parts of the fall-through code. This is important, even
* though it makes maintenance tougher.
* Do this later.
*/
and $17, 255, $1 # E : 00000000000000ch
insbl $17, 1, $2 # U : 000000000000ch00
mov $16, $0 # E : return value
ble $18, $end # U : zero length requested?
addq $18, $16, $6 # E : max address to write to
or $1, $2, $17 # E : 000000000000chch
insbl $1, 2, $3 # U : 0000000000ch0000
insbl $1, 3, $4 # U : 00000000ch000000
or $3, $4, $3 # E : 00000000chch0000
inswl $17, 4, $5 # U : 0000chch00000000
xor $16, $6, $1 # E : will complete write be within one quadword?
inswl $17, 6, $2 # U : chch000000000000
or $17, $3, $17 # E : 00000000chchchch
or $2, $5, $2 # E : chchchch00000000
bic $1, 7, $1 # E : fit within a single quadword?
and $16, 7, $3 # E : Target addr misalignment
or $17, $2, $17 # E : chchchchchchchch
beq $1, $within_quad # U :
nop # E :
beq $3, $aligned # U : target is 0mod8
/*
* Target address is misaligned, and won't fit within a quadword.
*/
ldq_u $4, 0($16) # L : Fetch first partial
mov $16, $5 # E : Save the address
insql $17, $16, $2 # U : Insert new bytes
subq $3, 8, $3 # E : Invert (for addressing uses)
addq $18, $3, $18 # E : $18 is new count ($3 is negative)
mskql $4, $16, $4 # U : clear relevant parts of the quad
subq $16, $3, $16 # E : $16 is new aligned destination
or $2, $4, $1 # E : Final bytes
nop
stq_u $1,0($5) # L : Store result
nop
nop
.align 4
$aligned:
/*
* We are now guaranteed to be quad aligned, with at least
* one partial quad to write.
*/
sra $18, 3, $3 # U : Number of remaining quads to write
and $18, 7, $18 # E : Number of trailing bytes to write
mov $16, $5 # E : Save dest address
beq $3, $no_quad # U : tail stuff only
/*
* It's worth the effort to unroll this and use wh64 if possible.
* At this point, entry values are:
* $16 Current destination address
* $5 A copy of $16
* $6 The max quadword address to write to
* $18 Number trailer bytes
* $3 Number quads to write
*/
and $16, 0x3f, $2 # E : Forward work (only useful for unrolled loop)
subq $3, 16, $4 # E : Only try to unroll if > 128 bytes
subq $2, 0x40, $1 # E : bias counter (aligning stuff 0mod64)
blt $4, $loop # U :
/*
* We know we've got at least 16 quads, minimum of one trip
* through unrolled loop. Do a quad at a time to get us 0mod64
* aligned.
*/
nop # E :
nop # E :
nop # E :
beq $1, $bigalign # U :
$alignmod64:
stq $17, 0($5) # L :
subq $3, 1, $3 # E : For consistency later
addq $1, 8, $1 # E : Increment towards zero for alignment
addq $5, 8, $4 # E : Initial wh64 address (filler instruction)
nop
nop
addq $5, 8, $5 # E : Inc address
blt $1, $alignmod64 # U :
$bigalign:
/*
* $3 - number quads left to go
* $5 - target address (aligned 0mod64)
* $17 - mask of stuff to store
* Scratch registers available: $7, $2, $4, $1
* We know that we'll be taking a minimum of one trip through.
* CWG Section 3.7.6: do not expect a sustained store rate of > 1/cycle
* Assumes the wh64 needs to be for 2 trips through the loop in the future.
* The wh64 is issued on for the starting destination address for trip +2
* through the loop, and if there are less than two trips left, the target
* address will be for the current trip.
*/
$do_wh64:
wh64 ($4) # L1 : memory subsystem write hint
subq $3, 24, $2 # E : For determining future wh64 addresses
stq $17, 0($5) # L :
nop # E :
addq $5, 128, $4 # E : speculative target of next wh64
stq $17, 8($5) # L :
stq $17, 16($5) # L :
addq $5, 64, $7 # E : Fallback address for wh64 (== next trip addr)
stq $17, 24($5) # L :
stq $17, 32($5) # L :
cmovlt $2, $7, $4 # E : Latency 2, extra mapping cycle
nop
stq $17, 40($5) # L :
stq $17, 48($5) # L :
subq $3, 16, $2 # E : Repeat the loop at least once more?
nop
stq $17, 56($5) # L :
addq $5, 64, $5 # E :
subq $3, 8, $3 # E :
bge $2, $do_wh64 # U :
nop
nop
nop
beq $3, $no_quad # U : Might have finished already
.align 4
/*
* Simple loop for trailing quadwords, or for small amounts
* of data (where we can't use an unrolled loop and wh64)
*/
$loop:
stq $17, 0($5) # L :
subq $3, 1, $3 # E : Decrement number quads left
addq $5, 8, $5 # E : Inc address
bne $3, $loop # U : more?
$no_quad:
/*
* Write 0..7 trailing bytes.
*/
nop # E :
beq $18, $end # U : All done?
ldq $7, 0($5) # L :
mskqh $7, $6, $2 # U : Mask final quad
insqh $17, $6, $4 # U : New bits
or $2, $4, $1 # E : Put it all together
stq $1, 0($5) # L : And back to memory
ret $31,($26),1 # L0 :
$within_quad:
ldq_u $1, 0($16) # L :
insql $17, $16, $2 # U : New bits
mskql $1, $16, $4 # U : Clear old
or $2, $4, $2 # E : New result
mskql $2, $6, $4 # U :
mskqh $1, $6, $2 # U :
or $2, $4, $1 # E :
stq_u $1, 0($16) # L :
$end:
nop
nop
nop
ret $31,($26),1 # L0 :
END(memset)
libc_hidden_builtin_def (memset)
|
