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/* Optimized memchr 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] memchr (char *s [r3], int byte [r4], int size [r5]) */
.machine power7
ENTRY (__memchr)
CALL_MCOUNT
dcbt 0,r3
clrrwi r8,r3,2
insrwi r4,r4,8,16 /* Replicate byte to word. */
/* Calculate the last acceptable address and check for possible
addition overflow by using satured math:
r7 = r3 + r5
r7 |= -(r7 < x) */
add r7,r3,r5
subfc r6,r3,r7
subfe r9,r9,r9
or r7,r7,r9
insrwi r4,r4,16,0
cmplwi r5,16
li r9, -1
rlwinm r6,r3,3,27,28 /* Calculate padding. */
addi r7,r7,-1
#ifdef __LITTLE_ENDIAN__
slw r9,r9,r6
#else
srw r9,r9,r6
#endif
ble L(small_range)
lwz r12,0(r8) /* Load word from memory. */
cmpb r3,r12,r4 /* Check for BYTEs in WORD1. */
and r3,r3,r9
clrlwi r5,r7,30 /* Byte count - 1 in last word. */
clrrwi r7,r7,2 /* Address of last word. */
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. */
bt 29,L(loop_setup)
/* Handle WORD2 of pair. */
lwzu r12,4(r8)
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 last byte of the string, ie. the word at
(s + size - 1) & ~3, or r7. 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 = (r7 - r8) / 8 */
sub r6,r7,r8
srwi r6,r6,3 /* Number of loop iterations. */
mtctr r6 /* Setup the counter. */
/* Main loop to look for BYTE in the string. Since
it's a small loop (8 instructions), align it to 32-bytes. */
.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. */
lwz r12,4(r8)
lwzu r11,8(r8)
cmpb r3,r12,r4
cmpb r9,r11,r4
or r6,r9,r3 /* Merge everything in one word. */
cmplwi cr7,r6,0
bne cr7,L(found)
bdnz L(loop)
/* We may have one more dword to read. */
cmplw r8,r7
beqlr
lwzu r12,4(r8)
cmpb r3,r12,r4
cmplwi cr6,r3,0
bne cr6,L(done)
blr
.align 4
L(found):
/* 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. */
cmplwi cr6,r3,0
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 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):
#ifdef __LITTLE_ENDIAN__
addi r0,r3,-1
andc r0,r0,r3
popcntw r0,r0 /* Count trailing zeros. */
#else
cntlzw r0,r3 /* Count leading zeros before the match. */
#endif
cmplw r8,r7 /* Are we on the last word? */
srwi r0,r0,3 /* Convert leading/trailing zeros to bytes. */
add r3,r8,r0
cmplw cr7,r0,r5 /* If on the last dword, check byte offset. */
bnelr
blelr 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)
lwz r12,0(r8) /* Load word from memory. */
cmpb r3,r12,r4 /* Check for BYTE in DWORD1. */
and r3,r3,r9
cmplwi cr7,r3,0
clrlwi r5,r7,30 /* Byte count - 1 in last word. */
clrrwi r7,r7,2 /* Address of last word. */
cmplw r8,r7 /* Are we done already? */
bne cr7,L(done)
beqlr
lwzu r12,4(r8)
cmpb r3,r12,r4
cmplwi cr6,r3,0
cmplw r8,r7
bne cr6,L(done)
beqlr
lwzu r12,4(r8)
cmpb r3,r12,r4
cmplwi cr6,r3,0
cmplw r8,r7
bne cr6,L(done)
beqlr
lwzu r12,4(r8)
cmpb r3,r12,r4
cmplwi cr6,r3,0
cmplw r8,r7
bne cr6,L(done)
beqlr
lwzu r12,4(r8)
cmpb r3,r12,r4
cmplwi cr6,r3,0
bne cr6,L(done)
blr
END (__memchr)
weak_alias (__memchr, memchr)
libc_hidden_builtin_def (memchr)
|
