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/* Optimized memrchr implementation for PowerPC32/POWER7 using cmpb insn.
Copyright (C) 2010-2021 Free Software Foundation, Inc.
Contributed by Luis Machado <luisgpm@br.ibm.com>.
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>
/* int [r3] memrchr (char *s [r3], int byte [r4], int size [r5]) */
.machine power7
ENTRY (__memrchr)
CALL_MCOUNT
add r7,r3,r5 /* Calculate the last acceptable address. */
neg r0,r7
addi r7,r7,-1
mr r10,r3
clrrwi r6,r7,7
li r9,3<<5
dcbt r9,r6,16 /* Stream hint, decreasing addresses. */
/* Replicate BYTE to word. */
insrwi r4,r4,8,16
insrwi r4,r4,16,0
li r6,-4
li r9,-1
rlwinm r0,r0,3,27,28 /* Calculate padding. */
clrrwi r8,r7,2
srw r9,r9,r0
cmplwi r5,16
clrrwi r0,r10,2
ble L(small_range)
#ifdef __LITTLE_ENDIAN__
lwzx r12,0,r8
#else
lwbrx r12,0,r8 /* Load reversed word from memory. */
#endif
cmpb r3,r12,r4 /* Check for BYTE in WORD1. */
and r3,r3,r9
cmplwi cr7,r3,0 /* If r3 == 0, no BYTEs have been found. */
bne cr7,L(done)
mtcrf 0x01,r8
/* Are we now aligned to a doubleword boundary? If so, skip to
the main loop. Otherwise, go through the alignment code. */
bf 29,L(loop_setup)
/* Handle WORD2 of pair. */
#ifdef __LITTLE_ENDIAN__
lwzx r12,r8,r6
#else
lwbrx r12,r8,r6
#endif
addi r8,r8,-4
cmpb r3,r12,r4
cmplwi cr7,r3,0
bne cr7,L(done)
L(loop_setup):
/* The last word we want to read in the loop below is the one
containing the first byte of the string, ie. the word at
s & ~3, or r0. The first word read is at r8 - 4, we
read 2 * cnt words, so the last word read will be at
r8 - 4 - 8 * cnt + 4. Solving for cnt gives
cnt = (r8 - r0) / 8 */
sub r5,r8,r0
addi r8,r8,-4
srwi r9,r5,3 /* Number of loop iterations. */
mtctr r9 /* Setup the counter. */
/* Main loop to look for BYTE backwards in the string.
FIXME: Investigate whether 32 byte align helps with this
9 instruction loop. */
.align 5
L(loop):
/* Load two words, compare and merge in a
single register for speed. This is an attempt
to speed up the byte-checking process for bigger strings. */
#ifdef __LITTLE_ENDIAN__
lwzx r12,0,r8
lwzx r11,r8,r6
#else
lwbrx r12,0,r8
lwbrx r11,r8,r6
#endif
cmpb r3,r12,r4
cmpb r9,r11,r4
or r5,r9,r3 /* Merge everything in one word. */
cmplwi cr7,r5,0
bne cr7,L(found)
addi r8,r8,-8
bdnz L(loop)
/* We may have one more word to read. */
cmplw r8,r0
bnelr
#ifdef __LITTLE_ENDIAN__
lwzx r12,0,r8
#else
lwbrx r12,0,r8
#endif
cmpb r3,r12,r4
cmplwi cr7,r3,0
bne cr7,L(done)
blr
.align 4
L(found):
/* OK, one (or both) of the words contains BYTE. Check
the first word. */
cmplwi cr6,r3,0
bne cr6,L(done)
/* BYTE must be in the second word. Adjust the address
again and move the result of cmpb to r3 so we can calculate the
pointer. */
mr r3,r9
addi r8,r8,-4
/* r3 has the output of the cmpb instruction, that is, it contains
0xff in the same position as BYTE in the original
word from the string. Use that to calculate the pointer.
We need to make sure BYTE is *before* the end of the
range. */
L(done):
cntlzw r9,r3 /* Count leading zeros before the match. */
cmplw r8,r0 /* Are we on the last word? */
srwi r6,r9,3 /* Convert leading zeros to bytes. */
addi r0,r6,-3
sub r3,r8,r0
cmplw cr7,r3,r10
bnelr
bgelr cr7
li r3,0
blr
.align 4
L(null):
li r3,0
blr
/* Deals with size <= 16. */
.align 4
L(small_range):
cmplwi r5,0
beq L(null)
#ifdef __LITTLE_ENDIAN__
lwzx r12,0,r8
#else
lwbrx r12,0,r8 /* Load reversed word from memory. */
#endif
cmpb r3,r12,r4 /* Check for BYTE in WORD1. */
and r3,r3,r9
cmplwi cr7,r3,0
bne cr7,L(done)
/* Are we done already? */
cmplw r8,r0
addi r8,r8,-4
beqlr
.align 5
L(loop_small):
#ifdef __LITTLE_ENDIAN__
lwzx r12,0,r8
#else
lwbrx r12,0,r8
#endif
cmpb r3,r12,r4
cmplw r8,r0
cmplwi cr7,r3,0
bne cr7,L(done)
addi r8,r8,-4
bne L(loop_small)
blr
END (__memrchr)
weak_alias (__memrchr, memrchr)
libc_hidden_builtin_def (memrchr)
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