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/* Optimized memrchr implementation for PowerPC64/POWER7 using cmpb insn.
Copyright (C) 2010-2021 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>
/* int [r3] memrchr (char *s [r3], int byte [r4], int size [r5]) */
#ifndef MEMRCHR
# define MEMRCHR __memrchr
#endif
.machine power7
ENTRY_TOCLESS (MEMRCHR)
CALL_MCOUNT 3
add r7,r3,r5 /* Calculate the last acceptable address. */
neg r0,r7
addi r7,r7,-1
mr r10,r3
clrrdi r6,r7,7
li r9,3<<5
dcbt r9,r6,8 /* Stream hint, decreasing addresses. */
/* Replicate BYTE to doubleword. */
insrdi r4,r4,8,48
insrdi r4,r4,16,32
insrdi r4,r4,32,0
li r6,-8
li r9,-1
rlwinm r0,r0,3,26,28 /* Calculate padding. */
clrrdi r8,r7,3
srd r9,r9,r0
cmpldi r5,32
clrrdi r0,r10,3
ble L(small_range)
#ifdef __LITTLE_ENDIAN__
ldx r12,0,r8
#else
ldbrx r12,0,r8 /* Load reversed doubleword from memory. */
#endif
cmpb r3,r12,r4 /* Check for BYTE in DWORD1. */
and r3,r3,r9
cmpldi cr7,r3,0 /* If r3 == 0, no BYTEs have been found. */
bne cr7,L(done)
mtcrf 0x01,r8
/* Are we now aligned to a quadword boundary? If so, skip to
the main loop. Otherwise, go through the alignment code. */
bf 28,L(loop_setup)
/* Handle DWORD2 of pair. */
#ifdef __LITTLE_ENDIAN__
ldx r12,r8,r6
#else
ldbrx r12,r8,r6
#endif
addi r8,r8,-8
cmpb r3,r12,r4
cmpldi cr7,r3,0
bne cr7,L(done)
L(loop_setup):
/* The last dword we want to read in the loop below is the one
containing the first byte of the string, ie. the dword at
s & ~7, or r0. The first dword read is at r8 - 8, we
read 2 * cnt dwords, so the last dword read will be at
r8 - 8 - 16 * cnt + 8. Solving for cnt gives
cnt = (r8 - r0) / 16 */
sub r5,r8,r0
addi r8,r8,-8
srdi r9,r5,4 /* 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 doublewords, 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__
ldx r12,0,r8
ldx r11,r8,r6
#else
ldbrx r12,0,r8
ldbrx r11,r8,r6
#endif
cmpb r3,r12,r4
cmpb r9,r11,r4
or r5,r9,r3 /* Merge everything in one doubleword. */
cmpldi cr7,r5,0
bne cr7,L(found)
addi r8,r8,-16
bdnz L(loop)
/* We may have one more word to read. */
cmpld r8,r0
bnelr
#ifdef __LITTLE_ENDIAN__
ldx r12,0,r8
#else
ldbrx r12,0,r8
#endif
cmpb r3,r12,r4
cmpldi cr7,r3,0
bne cr7,L(done)
blr
.align 4
L(found):
/* OK, one (or both) of the dwords contains BYTE. Check
the first dword. */
cmpldi 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,-8
/* 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):
cntlzd r9,r3 /* Count leading zeros before the match. */
cmpld r8,r0 /* Are we on the last word? */
srdi r6,r9,3 /* Convert leading zeros to bytes. */
addi r0,r6,-7
sub r3,r8,r0
cmpld cr7,r3,r10
bnelr
bgelr cr7
li r3,0
blr
.align 4
L(null):
li r3,0
blr
/* Deals with size <= 32. */
.align 4
L(small_range):
cmpldi r5,0
beq L(null)
#ifdef __LITTLE_ENDIAN__
ldx r12,0,r8
#else
ldbrx r12,0,r8 /* Load reversed doubleword from memory. */
#endif
cmpb r3,r12,r4 /* Check for BYTE in DWORD1. */
and r3,r3,r9
cmpldi cr7,r3,0
bne cr7,L(done)
/* Are we done already? */
cmpld r8,r0
addi r8,r8,-8
beqlr
.align 5
L(loop_small):
#ifdef __LITTLE_ENDIAN__
ldx r12,0,r8
#else
ldbrx r12,0,r8
#endif
cmpb r3,r12,r4
cmpld r8,r0
cmpldi cr7,r3,0
bne cr7,L(done)
addi r8,r8,-8
bne L(loop_small)
blr
END (MEMRCHR)
weak_alias (__memrchr, memrchr)
libc_hidden_builtin_def (memrchr)
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