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/* Optimized strcmp implementation for Power7 using 'cmpb' instruction
Copyright (C) 2014-2015 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
<http://www.gnu.org/licenses/>. */
/* The optimization is achieved here through cmpb instruction.
8byte aligned strings are processed with double word comparision
and unaligned strings are handled effectively with loop unrolling
technique */
#include <sysdep.h>
/* int [r3] strcmp (const char *s1 [r3], const char *s2 [r4]) */
.machine power7
EALIGN (strcmp, 4, 0)
CALL_MCOUNT 2
or r9, r3, r4
rldicl. r10, r9, 0, 61 /* are s1 and s2 8 byte aligned..? */
bne cr0, L(process_unaligned_bytes)
li r5, 0
.align 4
/* process input parameters on double word aligned boundary */
L(unrollDword):
ld r8,0(r3)
ld r10,0(r4)
cmpb r7,r8,r5
cmpdi cr7,r7,0
mr r9,r7
bne cr7,L(null_found)
cmpld cr7,r8,r10
bne cr7,L(different)
ld r8,8(r3)
ld r10,8(r4)
cmpb r7,r8,r5
cmpdi cr7,r7,0
mr r9,r7
bne cr7,L(null_found)
cmpld cr7,r8,r10
bne cr7,L(different)
ld r8,16(r3)
ld r10,16(r4)
cmpb r7,r8,r5
cmpdi cr7,r7,0
mr r9,r7
bne cr7,L(null_found)
cmpld cr7,r8,r10
bne cr7,L(different)
ld r8,24(r3)
ld r10,24(r4)
cmpb r7,r8,r5
cmpdi cr7,r7,0
mr r9,r7
bne cr7,L(null_found)
cmpld cr7,r8,r10
bne cr7,L(different)
addi r3, r3, 32
addi r4, r4, 32
beq cr7, L(unrollDword)
.align 4
L(null_found):
#ifdef __LITTLE_ENDIAN__
neg r7,r9
and r9,r9,r7
li r7,-1
cntlzd r9,r9
subfic r9,r9,71
sld r9,r7,r9
#else
cntlzd r9,r9
li r7,-1
addi r9,r9,8
srd r9,r7,r9
#endif
or r8,r8,r9
or r10,r10,r9
L(different):
cmpb r9,r8,r10
#ifdef __LITTLE_ENDIAN__
addi r7,r9,1
andc r9,r7,r9
cntlzd r9,r9
subfic r9,r9,63
#else
not r9,r9
cntlzd r9,r9
subfic r9,r9,56
#endif
srd r3,r8,r9
srd r10,r10,r9
rldicl r10,r10,0,56
rldicl r3,r3,0,56
subf r3,r10,r3
blr
.align 4
L(process_unaligned_bytes):
lbz r9, 0(r3) /* load byte from s1 */
lbz r10, 0(r4) /* load byte from s2 */
cmpdi cr7, r9, 0 /* compare *s1 with NULL */
beq cr7, L(diffOfNULL) /* if *s1 is NULL , return *s1 - *s2 */
cmplw cr7, r9, r10 /* compare *s1 and *s2 */
bne cr7, L(ComputeDiff) /* branch to compute difference and return */
lbz r9, 1(r3) /* load next byte from s1 */
lbz r10, 1(r4) /* load next byte from s2 */
cmpdi cr7, r9, 0 /* compare *s1 with NULL */
beq cr7, L(diffOfNULL) /* if *s1 is NULL , return *s1 - *s2 */
cmplw cr7, r9, r10 /* compare *s1 and *s2 */
bne cr7, L(ComputeDiff) /* branch to compute difference and return */
lbz r9, 2(r3) /* unroll 3rd byte here */
lbz r10, 2(r4)
cmpdi cr7, r9, 0
beq cr7, L(diffOfNULL)
cmplw cr7, r9, r10
bne 7, L(ComputeDiff)
lbz r9, 3(r3) /* unroll 4th byte now */
lbz r10, 3(r4)
addi r3, r3, 4 /* increment s1 by unroll factor */
cmpdi cr7, r9, 0
cmplw cr6, 9, r10
beq cr7, L(diffOfNULL)
addi r4, r4, 4 /* increment s2 by unroll factor */
beq cr6, L(process_unaligned_bytes) /* unroll byte processing */
.align 4
L(ComputeDiff):
extsw r9, r9
subf r10, r10, r9 /* compute s1 - s2 */
extsw r3, r10
blr /* return */
.align 4
L(diffOfNULL):
li r9, 0
subf r10, r10, r9 /* compute s1 - s2 */
extsw r3, r10 /* sign extend result */
blr /* return */
END (strcmp)
libc_hidden_builtin_def (strcmp)
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