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/* Optimized strchrnul implementation for PowerPC64/POWER7 using cmpb insn.
Copyright (C) 2010-2020 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>
#ifndef STRCHRNUL
# define STRCHRNUL __strchrnul
#endif
/* int [r3] strchrnul (char *s [r3], int c [r4]) */
.machine power7
ENTRY_TOCLESS (STRCHRNUL)
CALL_MCOUNT 2
dcbt 0,r3
clrrdi r8,r3,3 /* Align the address to doubleword boundary. */
/* Replicate byte to doubleword. */
insrdi r4,r4,8,48
insrdi r4,r4,16,32
insrdi r4,r4,32,0
rlwinm r6,r3,3,26,28 /* Calculate padding. */
ld r12,0(r8) /* Load doubleword from memory. */
li r0,0 /* Doubleword with null chars to use
with cmpb. */
/* Now r4 has a doubleword of c bytes and r0 has
a doubleword of null bytes. */
cmpb r10,r12,r0 /* Compare each byte against c byte. */
cmpb r9,r12,r4 /* Compare each byte against null byte. */
/* Move the doublewords left and right to discard the bits that are
not part of the string and to bring them back as zeros. */
#ifdef __LITTLE_ENDIAN__
srd r10,r10,r6
srd r9,r9,r6
sld r10,r10,r6
sld r9,r9,r6
#else
sld r10,r10,r6
sld r9,r9,r6
srd r10,r10,r6
srd r9,r9,r6
#endif
or r5,r9,r10 /* OR the results to speed things up. */
cmpdi cr7,r5,0 /* If r5 == 0, no c or null 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. */
bt 28,L(loop)
/* Handle DWORD2 of pair. */
ldu r12,8(r8)
cmpb r10,r12,r0
cmpb r9,r12,r4
or r5,r9,r10
cmpdi cr7,r5,0
bne cr7,L(done)
b L(loop) /* We branch here (rather than falling through)
to skip the nops due to heavy alignment
of the loop below. */
.p2align 5
L(loop):
/* Load two doublewords, compare and merge in a
single register for speed. This is an attempt
to speed up the null-checking process for bigger strings. */
ld r12,8(r8)
ldu r11,16(r8)
cmpb r10,r12,r0
cmpb r9,r12,r4
cmpb r6,r11,r0
cmpb r7,r11,r4
or r5,r9,r10
or r10,r6,r7
or r11,r5,r10
cmpdi cr7,r11,0
beq cr7,L(loop)
/* OK, one (or both) of the doublewords contains a c/null byte. Check
the first doubleword and decrement the address in case the first
doubleword really contains a c/null byte. */
cmpdi cr6,r5,0
addi r8,r8,-8
bne cr6,L(done)
/* The c/null byte must be in the second doubleword. Adjust the
address again and move the result of cmpb to r5 so we can calculate
the pointer. */
mr r5,r10
addi r8,r8,8
/* r5 has the output of the cmpb instruction, that is, it contains
0xff in the same position as the c/null byte in the original
doubleword from the string. Use that to calculate the pointer. */
L(done):
#ifdef __LITTLE_ENDIAN__
addi r0,r5,-1
andc r0,r0,r5
popcntd r0,r0
#else
cntlzd r0,r5 /* Count leading zeros before the match. */
#endif
srdi r0,r0,3 /* Convert leading zeros to bytes. */
add r3,r8,r0 /* Return address of matching c/null byte. */
blr
END (STRCHRNUL)
weak_alias (STRCHRNUL, strchrnul)
libc_hidden_builtin_def (STRCHRNUL)
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