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/* Optimized memrchr implementation for PowerPC32/POWER7 using cmpb insn.
Copyright (C) 2010 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
<http://www.gnu.org/licenses/>. */
#include <sysdep.h>
#include <bp-sym.h>
#include <bp-asm.h>
/* int [r3] memrchr (char *s [r3], int byte [r4], int size [r5]) */
.machine power7
ENTRY (BP_SYM (__memrchr))
CALL_MCOUNT
dcbt 0,r3
mr r7,r3
add r3,r7,r5 /* Calculate the last acceptable address. */
cmplw cr7,r3,r7 /* Is the address equal or less than r3? */
/* Replicate BYTE to word. */
rlwimi r4,r4,8,16,23
rlwimi r4,r4,16,0,15
bge cr7,L(proceed)
li r3,-1 /* Make r11 the biggest if r4 <= 0. */
L(proceed):
li r6,-4
addi r9,r3,-1
clrrwi r8,r9,2
addi r8,r8,4
neg r0,r3
rlwinm r0,r0,3,27,28 /* Calculate padding. */
cmplwi r5,16
ble L(small_range)
lwbrx r12,r8,r6 /* Load reversed word from memory. */
cmpb r10,r12,r4 /* Check for BYTE in WORD1. */
slw r10,r10,r0
srw r10,r10,r0
cmplwi cr7,r10,0 /* If r10 == 0, no BYTE's have been found. */
bne cr7,L(done)
/* Are we done already? */
addi r9,r8,-4
cmplw cr6,r9,r7
ble cr6,L(null)
mtcrf 0x01,r8
/* Are we now aligned to a doubleword boundary? If so, skip to
the main loop. Otherwise, go through the alignment code. */
mr r8,r9
bt 29,L(loop_setup)
/* Handle WORD2 of pair. */
lwbrx r12,r8,r6
cmpb r10,r12,r4
cmplwi cr7,r10,0
bne cr7,L(done)
/* Are we done already? */
addi r8,r8,-4
cmplw cr6,r8,r7
ble cr6,L(null)
L(loop_setup):
li r0,-8
sub r5,r8,r7
srwi r9,r5,3 /* Number of loop iterations. */
mtctr r9 /* Setup the counter. */
b L(loop)
/* Main loop to look for BYTE backwards in the string. Since it's a
small loop (< 8 instructions), align it to 32-bytes. */
.p2align 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. */
lwbrx r12,r8,r6
lwbrx r11,r8,r0
addi r8,r8,-4
cmpb r10,r12,r4
cmpb r9,r11,r4
or r5,r9,r10 /* Merge everything in one word. */
cmplwi cr7,r5,0
bne cr7,L(found)
addi r8,r8,-4
bdnz L(loop)
/* We're here because the counter reached 0, and that means we
didn't have any matches for BYTE in the whole range. Just return
the original range. */
addi r9,r8,4
cmplw cr6,r9,r7
bgt cr6,L(loop_small)
b L(null)
/* OK, one (or both) of the words contains BYTE. Check
the first word and decrement the address in case the first
word really contains BYTE. */
.align 4
L(found):
cmplwi cr6,r10,0
addi r8,r8,4
bne cr6,L(done)
/* BYTE must be in the second word. Adjust the address
again and move the result of cmpb to r10 so we can calculate the
pointer. */
mr r10,r9
addi r8,r8,-4
/* r10 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 r0,r10 /* Count leading zeroes before the match. */
srwi r6,r0,3 /* Convert leading zeroes to bytes. */
addi r0,r6,1
sub r3,r8,r0
cmplw r3,r7
blt L(null)
blr
.align 4
L(null):
li r3,0
blr
/* Deals with size <= 16. */
.align 4
L(small_range):
cmplwi r5,0
beq L(null)
lwbrx r12,r8,r6 /* Load reversed word from memory. */
cmpb r10,r12,r4 /* Check for null bytes in WORD1. */
slw r10,r10,r0
srw r10,r10,r0
cmplwi cr7,r10,0
bne cr7,L(done)
addi r8,r8,-4
cmplw r8,r7
ble L(null)
b L(loop_small)
.p2align 5
L(loop_small):
lwbrx r12,r8,r6
cmpb r10,r12,r4
cmplwi cr6,r10,0
bne cr6,L(done)
addi r8,r8,-4
cmplw r8,r7
ble L(null)
b L(loop_small)
END (BP_SYM (__memrchr))
weak_alias (BP_SYM (__memrchr), BP_SYM(memrchr))
libc_hidden_builtin_def (memrchr)
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