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/* Optimized strchr 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] strchr (char *s [r3], int c [r4]) */
.machine power7
ENTRY (strchr)
CALL_MCOUNT
dcbt 0,r3
clrrwi r8,r3,2 /* Align the address to word boundary. */
cmpwi cr7,r4,0
lwz r12,0(r8) /* Load word from memory. */
li r0,0 /* Word with null chars to use
with cmpb. */
rlwinm r6,r3,3,27,28 /* Calculate padding. */
beq cr7,L(null_match)
/* Replicate byte to word. */
insrwi r4,r4,8,16
insrwi r4,r4,16,0
/* Now r4 has a word of c bytes and r0 has
a word of null bytes. */
cmpb r10,r12,r4 /* Compare each byte against c byte. */
cmpb r11,r12,r0 /* Compare each byte against null byte. */
/* Move the words left and right to discard the bits that are
not part of the string and to bring them back as zeros. */
#ifdef __LITTLE_ENDIAN__
srw r10,r10,r6
srw r11,r11,r6
slw r10,r10,r6
slw r11,r11,r6
#else
slw r10,r10,r6
slw r11,r11,r6
srw r10,r10,r6
srw r11,r11,r6
#endif
or r5,r10,r11 /* OR the results to speed things up. */
cmpwi 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 doubleword boundary? If so, skip to
the main loop. Otherwise, go through the alignment code. */
bt 29,L(loop)
/* Handle WORD2 of pair. */
lwzu r12,4(r8)
cmpb r10,r12,r4
cmpb r11,r12,r0
or r5,r10,r11
cmpwi 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 words, compare and merge in a
single register for speed. This is an attempt
to speed up the null-checking process for bigger strings. */
lwz r12,4(r8)
lwzu r9,8(r8)
cmpb r10,r12,r4
cmpb r11,r12,r0
cmpb r6,r9,r4
cmpb r7,r9,r0
or r12,r10,r11
or r9,r6,r7
or r5,r12,r9
cmpwi cr7,r5,0
beq cr7,L(loop)
/* OK, one (or both) of the words contains a c/null byte. Check
the first word and decrement the address in case the first
word really contains a c/null byte. */
cmpwi cr6,r12,0
addi r8,r8,-4
bne cr6,L(done)
/* The c/null byte must be in the second word. Adjust the address
again and move the result of cmpb to r10/r11 so we can calculate
the pointer. */
mr r10,r6
mr r11,r7
addi r8,r8,4
/* r10/r11 have the output of the cmpb instructions, that is,
0xff in the same position as the c/null byte in the original
word from the string. Use that to calculate the pointer. */
L(done):
#ifdef __LITTLE_ENDIAN__
addi r3,r10,-1
andc r3,r3,r10
popcntw r0,r3
addi r4,r11,-1
andc r4,r4,r11
cmplw cr7,r3,r4
bgt cr7,L(no_match)
#else
cntlzw r0,r10 /* Count leading zeros before c matches. */
cmplw cr7,r11,r10
bgt cr7,L(no_match)
#endif
srwi r0,r0,3 /* Convert leading zeros to bytes. */
add r3,r8,r0 /* Return address of the matching c byte
or null in case c was not found. */
blr
.align 4
L(no_match):
li r3,0
blr
/* We are here because strchr was called with a null byte. */
.align 4
L(null_match):
/* r0 has a word of null bytes. */
cmpb r5,r12,r0 /* Compare each byte against null bytes. */
/* Move the words left and right to discard the bits that are
not part of the string and bring them back as zeros. */
#ifdef __LITTLE_ENDIAN__
srw r5,r5,r6
slw r5,r5,r6
#else
slw r5,r5,r6
srw r5,r5,r6
#endif
cmpwi cr7,r5,0 /* If r10 == 0, no c or null bytes
have been found. */
bne cr7,L(done_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. */
bt 29,L(loop_null)
/* Handle WORD2 of pair. */
lwzu r12,4(r8)
cmpb r5,r12,r0
cmpwi cr7,r5,0
bne cr7,L(done_null)
b L(loop_null) /* We branch here (rather than falling through)
to skip the nops due to heavy alignment
of the loop below. */
/* Main loop to look for the end of the string. Since it's a
small loop (< 8 instructions), align it to 32-bytes. */
.p2align 5
L(loop_null):
/* Load two words, compare and merge in a
single register for speed. This is an attempt
to speed up the null-checking process for bigger strings. */
lwz r12,4(r8)
lwzu r11,8(r8)
cmpb r5,r12,r0
cmpb r10,r11,r0
or r6,r5,r10
cmpwi cr7,r6,0
beq cr7,L(loop_null)
/* OK, one (or both) of the words contains a null byte. Check
the first word and decrement the address in case the first
word really contains a null byte. */
cmpwi cr6,r5,0
addi r8,r8,-4
bne cr6,L(done_null)
/* The null 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 r5,r10
addi r8,r8,4
/* r5 has the output of the cmpb instruction, that is, it contains
0xff in the same position as the null byte in the original
word from the string. Use that to calculate the pointer. */
L(done_null):
#ifdef __LITTLE_ENDIAN__
addi r0,r5,-1
andc r0,r0,r5
popcntw r0,r0
#else
cntlzw r0,r5 /* Count leading zeros before the match. */
#endif
srwi r0,r0,3 /* Convert leading zeros to bytes. */
add r3,r8,r0 /* Return address of the matching null byte. */
blr
END (strchr)
weak_alias (strchr, index)
libc_hidden_builtin_def (strchr)
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