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/* Optimized strcmp implementation for PowerPC.
Copyright (C) 1997-2021 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>
/* See strlen.s for comments on how the end-of-string testing works. */
/* int [r3] strcmp (const char *s1 [r3], const char *s2 [r4]) */
EALIGN (strcmp, 4, 0)
#define rTMP2 r0
#define rRTN r3
#define rSTR1 r3 /* first string arg */
#define rSTR2 r4 /* second string arg */
#define rWORD1 r5 /* current word in s1 */
#define rWORD2 r6 /* current word in s2 */
#define rFEFE r7 /* constant 0xfefefeff (-0x01010101) */
#define r7F7F r8 /* constant 0x7f7f7f7f */
#define rNEG r9 /* ~(word in s1 | 0x7f7f7f7f) */
#define rBITDIF r10 /* bits that differ in s1 & s2 words */
#define rTMP r11
or rTMP, rSTR2, rSTR1
clrlwi. rTMP, rTMP, 30
lis rFEFE, -0x101
bne L(unaligned)
lwz rWORD1, 0(rSTR1)
lwz rWORD2, 0(rSTR2)
lis r7F7F, 0x7f7f
addi rFEFE, rFEFE, -0x101
addi r7F7F, r7F7F, 0x7f7f
b L(g1)
L(g0): lwzu rWORD1, 4(rSTR1)
bne cr1, L(different)
lwzu rWORD2, 4(rSTR2)
L(g1): add rTMP, rFEFE, rWORD1
nor rNEG, r7F7F, rWORD1
and. rTMP, rTMP, rNEG
cmpw cr1, rWORD1, rWORD2
beq+ L(g0)
/* OK. We've hit the end of the string. We need to be careful that
we don't compare two strings as different because of gunk beyond
the end of the strings... */
#ifdef __LITTLE_ENDIAN__
L(endstring):
addi rTMP2, rTMP, -1
andc rTMP2, rTMP2, rTMP
rlwimi rTMP2, rTMP2, 1, 0, 30
and rWORD2, rWORD2, rTMP2 /* Mask off gunk. */
and rWORD1, rWORD1, rTMP2
rlwinm rTMP2, rWORD2, 8, 0xffffffff /* Byte reverse word. */
rlwinm rTMP, rWORD1, 8, 0xffffffff
rlwimi rTMP2, rWORD2, 24, 0, 7
rlwimi rTMP, rWORD1, 24, 0, 7
rlwimi rTMP2, rWORD2, 24, 16, 23
rlwimi rTMP, rWORD1, 24, 16, 23
xor. rBITDIF, rTMP, rTMP2
sub rRTN, rTMP, rTMP2
bgelr+
ori rRTN, rTMP2, 1
blr
L(different):
lwz rWORD1, -4(rSTR1)
rlwinm rTMP2, rWORD2, 8, 0xffffffff /* Byte reverse word. */
rlwinm rTMP, rWORD1, 8, 0xffffffff
rlwimi rTMP2, rWORD2, 24, 0, 7
rlwimi rTMP, rWORD1, 24, 0, 7
rlwimi rTMP2, rWORD2, 24, 16, 23
rlwimi rTMP, rWORD1, 24, 16, 23
xor. rBITDIF, rTMP, rTMP2
sub rRTN, rTMP, rTMP2
bgelr+
ori rRTN, rTMP2, 1
blr
#else
L(endstring):
and rTMP, r7F7F, rWORD1
beq cr1, L(equal)
add rTMP, rTMP, r7F7F
xor. rBITDIF, rWORD1, rWORD2
andc rNEG, rNEG, rTMP
blt- L(highbit)
cntlzw rBITDIF, rBITDIF
cntlzw rNEG, rNEG
addi rNEG, rNEG, 7
cmpw cr1, rNEG, rBITDIF
sub rRTN, rWORD1, rWORD2
bgelr+ cr1
L(equal):
li rRTN, 0
blr
L(different):
lwz rWORD1, -4(rSTR1)
xor. rBITDIF, rWORD1, rWORD2
sub rRTN, rWORD1, rWORD2
bgelr+
L(highbit):
ori rRTN, rWORD2, 1
blr
#endif
/* Oh well. In this case, we just do a byte-by-byte comparison. */
.align 4
L(unaligned):
lbz rWORD1, 0(rSTR1)
lbz rWORD2, 0(rSTR2)
b L(u1)
L(u0): lbzu rWORD1, 1(rSTR1)
bne- L(u4)
lbzu rWORD2, 1(rSTR2)
L(u1): cmpwi cr1, rWORD1, 0
beq- cr1, L(u3)
cmpw rWORD1, rWORD2
bne- L(u3)
lbzu rWORD1, 1(rSTR1)
lbzu rWORD2, 1(rSTR2)
cmpwi cr1, rWORD1, 0
cmpw rWORD1, rWORD2
bne+ cr1, L(u0)
L(u3): sub rRTN, rWORD1, rWORD2
blr
L(u4): lbz rWORD1, -1(rSTR1)
sub rRTN, rWORD1, rWORD2
blr
END (strcmp)
libc_hidden_builtin_def (strcmp)
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