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/* Optimized memchr implementation for PowerPC64/POWER7 using cmpb insn.
Copyright (C) 2010-2024 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>
/* int [r3] memchr (char *s [r3], int byte [r4], int size [r5]) */
#ifndef MEMCHR
# define MEMCHR __memchr
#endif
.machine power7
ENTRY_TOCLESS (MEMCHR)
CALL_MCOUNT 3
dcbt 0,r3
clrrdi r8,r3,3
insrdi r4,r4,8,48
/* 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
extsw r6,r9
or r7,r7,r6
insrdi r4,r4,16,32
cmpldi r5,32
li r9, -1
rlwinm r6,r3,3,26,28 /* Calculate padding. */
insrdi r4,r4,32,0
addi r7,r7,-1
#ifdef __LITTLE_ENDIAN__
sld r9,r9,r6
#else
srd r9,r9,r6
#endif
ble L(small_range)
ld r12,0(r8) /* Load doubleword from memory. */
cmpb r3,r12,r4 /* Check for BYTEs in DWORD1. */
and r3,r3,r9
clrldi r5,r7,61 /* Byte count - 1 in last dword. */
clrrdi r7,r7,3 /* Address of last doubleword. */
cmpldi cr7,r3,0 /* Does r3 indicate we got a hit? */
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. */
bt 28,L(loop_setup)
/* Handle DWORD2 of pair. */
ldu r12,8(r8)
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 last byte of the string, ie. the dword at
(s + size - 1) & ~7, or r7. 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 = (r7 - r8) / 16 */
sub r6,r7,r8
srdi r6,r6,4 /* 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 doublewords, compare and merge in a
single register for speed. This is an attempt
to speed up the byte-checking process for bigger strings. */
ld r12,8(r8)
ldu r11,16(r8)
cmpb r3,r12,r4
cmpb r9,r11,r4
or r6,r9,r3 /* Merge everything in one doubleword. */
cmpldi cr7,r6,0
bne cr7,L(found)
bdnz L(loop)
/* We may have one more dword to read. */
cmpld r8,r7
beqlr
ldu r12,8(r8)
cmpb r3,r12,r4
cmpldi cr6,r3,0
bne cr6,L(done)
blr
.align 4
L(found):
/* OK, one (or both) of the doublewords contains BYTE. Check
the first doubleword and decrement the address in case the first
doubleword really contains BYTE. */
cmpldi cr6,r3,0
addi r8,r8,-8
bne cr6,L(done)
/* BYTE must be in the second doubleword. 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
doubleword 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
popcntd r0,r0 /* Count trailing zeros. */
#else
cntlzd r0,r3 /* Count leading zeros before the match. */
#endif
cmpld r8,r7 /* Are we on the last dword? */
srdi r0,r0,3 /* Convert leading/trailing zeros to bytes. */
add r3,r8,r0
cmpld 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 <= 32. */
.align 4
L(small_range):
cmpldi r5,0
beq L(null)
ld r12,0(r8) /* Load word from memory. */
cmpb r3,r12,r4 /* Check for BYTE in DWORD1. */
and r3,r3,r9
cmpldi cr7,r3,0
clrldi r5,r7,61 /* Byte count - 1 in last dword. */
clrrdi r7,r7,3 /* Address of last doubleword. */
cmpld r8,r7 /* Are we done already? */
bne cr7,L(done)
beqlr
ldu r12,8(r8)
cmpb r3,r12,r4
cmpldi cr6,r3,0
cmpld r8,r7
bne cr6,L(done) /* Found something. */
beqlr /* Hit end of string (length). */
ldu r12,8(r8)
cmpb r3,r12,r4
cmpldi cr6,r3,0
cmpld r8,r7
bne cr6,L(done)
beqlr
ldu r12,8(r8)
cmpb r3,r12,r4
cmpldi cr6,r3,0
cmpld r8,r7
bne cr6,L(done)
beqlr
ldu r12,8(r8)
cmpb r3,r12,r4
cmpldi cr6,r3,0
bne cr6,L(done)
blr
END (MEMCHR)
weak_alias (__memchr, memchr)
libc_hidden_builtin_def (memchr)
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