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/* Optimized strchr implementation for PowerPC64/POWER7 using cmpb insn.
Copyright (C) 2010-2013 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>
/* int [r3] strchr (char *s [r3], int c [r4]) */
.machine power7
ENTRY (strchr)
CALL_MCOUNT 2
dcbt 0,r3
clrrdi r8,r3,3 /* Align the address to doubleword boundary. */
cmpdi cr7,r4,0
ld r12,0(r8) /* Load doubleword from memory. */
li r0,0 /* Doubleword with null chars to use
with cmpb. */
rlwinm r6,r3,3,26,28 /* Calculate padding. */
beq cr7,L(null_match)
/* Replicate byte to doubleword. */
rlwimi r4,r4,8,16,23
rlwimi r4,r4,16,0,15
insrdi r4,r4,32,0
/* Now r4 has a doubleword of c bytes and r0 has
a doubleword 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 doublewords left and right to discard the bits that are
not part of the string and bring them back as zeros. */
sld r10,r10,r6
sld r11,r11,r6
srd r10,r10,r6
srd r11,r11,r6
or r5,r10,r11 /* 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 doubleword boundary? If so, skip to
the main loop. Otherwise, go through the alignment code. */
bt 28,L(loop)
/* Handle WORD2 of pair. */
ldu r12,8(r8)
cmpb r10,r12,r4
cmpb r11,r12,r0
or r5,r10,r11
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 r9,16(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
cmpdi cr7,r5,0
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,r12,0
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 r10 so we can calculate
the pointer. */
mr r10,r6
mr r11,r7
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):
cntlzd r4,r10 /* Count leading zeroes before c matches. */
cntlzd r0,r11 /* Count leading zeroes before null matches. */
cmpld cr7,r4,r0
bgt cr7,L(no_match)
srdi r0,r4,3 /* Convert leading zeroes 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 doubleword of null bytes. */
cmpb r5,r12,r0 /* Compare each byte against null bytes. */
/* Move the doublewords left and right to discard the bits that are
not part of the string and bring them back as zeros. */
sld r5,r5,r6
srd r5,r5,r6
cmpdi 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 quadword boundary? If so, skip to
the main loop. Otherwise, go through the alignment code. */
bt 28,L(loop_null)
/* Handle WORD2 of pair. */
ldu r12,8(r8)
cmpb r5,r12,r0
cmpdi 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 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 r5,r12,r0
cmpb r10,r11,r0
or r6,r5,r10
cmpdi cr7,r6,0
beq cr7,L(loop_null)
/* OK, one (or both) of the doublewords contains a null byte. Check
the first doubleword and decrement the address in case the first
doubleword really contains a null byte. */
cmpdi cr6,r5,0
addi r8,r8,-8
bne cr6,L(done_null)
/* The null byte must be in the second doubleword. Adjust the address
again and move the result of cmpb to r10 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 null byte in the original
doubleword from the string. Use that to calculate the pointer. */
L(done_null):
cntlzd r0,r5 /* Count leading zeros before the match. */
srdi 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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