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/* Optimized memset implementation for PowerPC.
Copyright (C) 1997-2024 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/>. */
#include <sysdep.h>
#include <rtld-global-offsets.h>
/* void * [r3] memset (void *s [r3], int c [r4], size_t n [r5]));
Returns 's'.
The memset is done in four sizes: byte (8 bits), word (32 bits),
32-byte blocks (256 bits) and cache line size (128, 256, 1024 bits).
There is a special case for setting whole cache lines to 0, which
takes advantage of the dcbz instruction. */
.section ".text"
EALIGN (memset, 5, 1)
#define rTMP r0
#define rRTN r3 /* initial value of 1st argument */
#define rMEMP0 r3 /* original value of 1st arg */
#define rCHR r4 /* char to set in each byte */
#define rLEN r5 /* length of region to set */
#define rMEMP r6 /* address at which we are storing */
#define rALIGN r7 /* number of bytes we are setting now (when aligning) */
#define rMEMP2 r8
#define rPOS32 r7 /* constant +32 for clearing with dcbz */
#define rNEG64 r8 /* constant -64 for clearing with dcbz */
#define rNEG32 r9 /* constant -32 for clearing with dcbz */
#define rGOT r9 /* Address of the Global Offset Table. */
#define rCLS r8 /* Cache line size obtained from static. */
#define rCLM r9 /* Cache line size mask to check for cache alignment. */
/* take care of case for size <= 4 */
cmplwi cr1, rLEN, 4
andi. rALIGN, rMEMP0, 3
mr rMEMP, rMEMP0
ble- cr1, L(small)
/* align to word boundary */
cmplwi cr5, rLEN, 31
rlwimi rCHR, rCHR, 8, 16, 23
beq+ L(aligned) /* 8th instruction from .align */
mtcrf 0x01, rMEMP0
subfic rALIGN, rALIGN, 4
add rMEMP, rMEMP, rALIGN
sub rLEN, rLEN, rALIGN
bf+ 31, L(g0)
stb rCHR, 0(rMEMP0)
bt 30, L(aligned)
L(g0): sth rCHR, -2(rMEMP) /* 16th instruction from .align */
/* take care of case for size < 31 */
L(aligned):
mtcrf 0x01, rLEN
rlwimi rCHR, rCHR, 16, 0, 15
ble cr5, L(medium)
/* align to cache line boundary... */
andi. rALIGN, rMEMP, 0x1C
subfic rALIGN, rALIGN, 0x20
beq L(caligned)
mtcrf 0x01, rALIGN
add rMEMP, rMEMP, rALIGN
sub rLEN, rLEN, rALIGN
cmplwi cr1, rALIGN, 0x10
mr rMEMP2, rMEMP
bf 28, L(a1)
stw rCHR, -4(rMEMP2)
stwu rCHR, -8(rMEMP2)
L(a1): blt cr1, L(a2)
stw rCHR, -4(rMEMP2) /* 32nd instruction from .align */
stw rCHR, -8(rMEMP2)
stw rCHR, -12(rMEMP2)
stwu rCHR, -16(rMEMP2)
L(a2): bf 29, L(caligned)
stw rCHR, -4(rMEMP2)
/* now aligned to a cache line. */
L(caligned):
cmplwi cr1, rCHR, 0
clrrwi. rALIGN, rLEN, 5
mtcrf 0x01, rLEN /* 40th instruction from .align */
/* Check if we can use the special case for clearing memory using dcbz.
This requires that we know the correct cache line size for this
processor. Getting the cache line size may require establishing GOT
addressability, so branch out of line to set this up. */
beq cr1, L(checklinesize)
/* Store blocks of 32-bytes (256-bits) starting on a 32-byte boundary.
Can't assume that rCHR is zero or that the cache line size is either
32-bytes or even known. */
L(nondcbz):
srwi rTMP, rALIGN, 5
mtctr rTMP
beq L(medium) /* we may not actually get to do a full line */
clrlwi. rLEN, rLEN, 27
add rMEMP, rMEMP, rALIGN
li rNEG64, -0x40
bdz L(cloopdone) /* 48th instruction from .align */
/* We can't use dcbz here as we don't know the cache line size. We can
use "data cache block touch for store", which is safe. */
L(c3): dcbtst rNEG64, rMEMP
stw rCHR, -4(rMEMP)
stw rCHR, -8(rMEMP)
stw rCHR, -12(rMEMP)
stw rCHR, -16(rMEMP)
nop /* let 601 fetch last 4 instructions of loop */
stw rCHR, -20(rMEMP)
stw rCHR, -24(rMEMP) /* 56th instruction from .align */
nop /* let 601 fetch first 8 instructions of loop */
stw rCHR, -28(rMEMP)
stwu rCHR, -32(rMEMP)
bdnz L(c3)
L(cloopdone):
stw rCHR, -4(rMEMP)
stw rCHR, -8(rMEMP)
stw rCHR, -12(rMEMP)
stw rCHR, -16(rMEMP) /* 64th instruction from .align */
stw rCHR, -20(rMEMP)
cmplwi cr1, rLEN, 16
stw rCHR, -24(rMEMP)
stw rCHR, -28(rMEMP)
stwu rCHR, -32(rMEMP)
beqlr
add rMEMP, rMEMP, rALIGN
b L(medium_tail2) /* 72nd instruction from .align */
.align 5
nop
/* Clear cache lines of memory in 128-byte chunks.
This code is optimized for processors with 32-byte cache lines.
It is further optimized for the 601 processor, which requires
some care in how the code is aligned in the i-cache. */
L(zloopstart):
clrlwi rLEN, rLEN, 27
mtcrf 0x02, rALIGN
srwi. rTMP, rALIGN, 7
mtctr rTMP
li rPOS32, 0x20
li rNEG64, -0x40
cmplwi cr1, rLEN, 16 /* 8 */
bf 26, L(z0)
dcbz 0, rMEMP
addi rMEMP, rMEMP, 0x20
L(z0): li rNEG32, -0x20
bf 25, L(z1)
dcbz 0, rMEMP
dcbz rPOS32, rMEMP
addi rMEMP, rMEMP, 0x40 /* 16 */
L(z1): cmplwi cr5, rLEN, 0
beq L(medium)
L(zloop):
dcbz 0, rMEMP
dcbz rPOS32, rMEMP
addi rMEMP, rMEMP, 0x80
dcbz rNEG64, rMEMP
dcbz rNEG32, rMEMP
bdnz L(zloop)
beqlr cr5
b L(medium_tail2)
.align 5
L(small):
/* Memset of 4 bytes or less. */
cmplwi cr5, rLEN, 1
cmplwi cr1, rLEN, 3
bltlr cr5
stb rCHR, 0(rMEMP)
beqlr cr5
nop
stb rCHR, 1(rMEMP)
bltlr cr1
stb rCHR, 2(rMEMP)
beqlr cr1
nop
stb rCHR, 3(rMEMP)
blr
/* Memset of 0-31 bytes. */
.align 5
L(medium):
cmplwi cr1, rLEN, 16
L(medium_tail2):
add rMEMP, rMEMP, rLEN
L(medium_tail):
bt- 31, L(medium_31t)
bt- 30, L(medium_30t)
L(medium_30f):
bt- 29, L(medium_29t)
L(medium_29f):
bge- cr1, L(medium_27t)
bflr- 28
stw rCHR, -4(rMEMP) /* 8th instruction from .align */
stw rCHR, -8(rMEMP)
blr
L(medium_31t):
stbu rCHR, -1(rMEMP)
bf- 30, L(medium_30f)
L(medium_30t):
sthu rCHR, -2(rMEMP)
bf- 29, L(medium_29f)
L(medium_29t):
stwu rCHR, -4(rMEMP)
blt- cr1, L(medium_27f) /* 16th instruction from .align */
L(medium_27t):
stw rCHR, -4(rMEMP)
stw rCHR, -8(rMEMP)
stw rCHR, -12(rMEMP)
stwu rCHR, -16(rMEMP)
L(medium_27f):
bflr- 28
L(medium_28t):
stw rCHR, -4(rMEMP)
stw rCHR, -8(rMEMP)
blr
L(checklinesize):
/* If the remaining length is less the 32 bytes then don't bother getting
the cache line size. */
beq L(medium)
#ifdef PIC
mflr rTMP
/* Establishes GOT addressability so we can load the cache line size
from rtld_global_ro. This value was set from the aux vector during
startup. */
SETUP_GOT_ACCESS(rGOT,got_label)
addis rGOT,rGOT,_GLOBAL_OFFSET_TABLE_-got_label@ha
addi rGOT,rGOT,_GLOBAL_OFFSET_TABLE_-got_label@l
mtlr rTMP
#endif
/* Load rtld_global_ro._dl_cache_line_size. */
__GLRO(rCLS, rGOT, _dl_cache_line_size,
RTLD_GLOBAL_RO_DL_CACHE_LINE_SIZE_OFFSET)
/* If the cache line size was not set then goto to L(nondcbz), which is
safe for any cache line size. */
cmplwi cr1,rCLS,0
beq cr1,L(nondcbz)
/* If the cache line size is 32 bytes then goto to L(zloopstart),
which is coded specifically for 32-byte lines (and 601). */
cmplwi cr1,rCLS,32
beq cr1,L(zloopstart)
/* Now we know the cache line size and it is not 32-bytes. However
we may not yet be aligned to the cache line and may have a partial
line to fill. Touch it 1st to fetch the cache line. */
dcbtst 0,rMEMP
addi rCLM,rCLS,-1
L(getCacheAligned):
cmplwi cr1,rLEN,32
and. rTMP,rCLM,rMEMP
blt cr1,L(handletail32)
beq L(cacheAligned)
/* We are not aligned to start of a cache line yet. Store 32-byte
of data and test again. */
addi rMEMP,rMEMP,32
addi rLEN,rLEN,-32
stw rCHR,-32(rMEMP)
stw rCHR,-28(rMEMP)
stw rCHR,-24(rMEMP)
stw rCHR,-20(rMEMP)
stw rCHR,-16(rMEMP)
stw rCHR,-12(rMEMP)
stw rCHR,-8(rMEMP)
stw rCHR,-4(rMEMP)
b L(getCacheAligned)
/* Now we are aligned to the cache line and can use dcbz. */
L(cacheAligned):
cmplw cr1,rLEN,rCLS
blt cr1,L(handletail32)
dcbz 0,rMEMP
subf rLEN,rCLS,rLEN
add rMEMP,rMEMP,rCLS
b L(cacheAligned)
/* We are here because; the cache line size was set, it was not
32-bytes, and the remainder (rLEN) is now less than the actual cache
line size. Set up the preconditions for L(nondcbz) and go there to
store the remaining bytes. */
L(handletail32):
clrrwi. rALIGN, rLEN, 5
b L(nondcbz)
END (memset)
libc_hidden_builtin_def (memset)
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