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/* Optimized strcmp implementation for PowerPC64.
Copyright (C) 2003-2023 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] strncmp (const char *s1 [r3], const char *s2 [r4], size_t size [r5]) */
#ifndef STRNCMP
# define STRNCMP strncmp
#endif
ENTRY_TOCLESS (STRNCMP, 4)
CALL_MCOUNT 3
#define rTMP2 r0
#define rRTN r3
#define rSTR1 r3 /* first string arg */
#define rSTR2 r4 /* second string arg */
#define rN r5 /* max string length */
#define rWORD1 r6 /* current word in s1 */
#define rWORD2 r7 /* current word in s2 */
#define rFEFE r8 /* constant 0xfefefefefefefeff (-0x0101010101010101) */
#define r7F7F r9 /* constant 0x7f7f7f7f7f7f7f7f */
#define rNEG r10 /* ~(word in s1 | 0x7f7f7f7f7f7f7f7f) */
#define rBITDIF r11 /* bits that differ in s1 & s2 words */
#define rTMP r12
dcbt 0,rSTR1
or rTMP, rSTR2, rSTR1
lis r7F7F, 0x7f7f
dcbt 0,rSTR2
clrldi. rTMP, rTMP, 61
cmpldi cr1, rN, 0
lis rFEFE, -0x101
bne L(unaligned)
/* We are doubleword aligned so set up for two loops. first a double word
loop, then fall into the byte loop if any residual. */
srdi. rTMP, rN, 3
clrldi rN, rN, 61
addi rFEFE, rFEFE, -0x101
addi r7F7F, r7F7F, 0x7f7f
cmpldi cr1, rN, 0
beq L(unaligned)
mtctr rTMP /* Power4 wants mtctr 1st in dispatch group. */
ld rWORD1, 0(rSTR1)
ld rWORD2, 0(rSTR2)
sldi rTMP, rFEFE, 32
insrdi r7F7F, r7F7F, 32, 0
add rFEFE, rFEFE, rTMP
b L(g1)
L(g0):
ldu rWORD1, 8(rSTR1)
bne- cr1, L(different)
ldu rWORD2, 8(rSTR2)
L(g1): add rTMP, rFEFE, rWORD1
nor rNEG, r7F7F, rWORD1
bdz L(tail)
and. rTMP, rTMP, rNEG
cmpd 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
beq cr1, L(equal)
andc rTMP2, rTMP2, rTMP
rldimi rTMP2, rTMP2, 1, 0
and rWORD2, rWORD2, rTMP2 /* Mask off gunk. */
and rWORD1, rWORD1, rTMP2
cmpd cr1, rWORD1, rWORD2
beq cr1, L(equal)
xor rBITDIF, rWORD1, rWORD2 /* rBITDIF has bits that differ. */
neg rNEG, rBITDIF
and rNEG, rNEG, rBITDIF /* rNEG has LS bit that differs. */
cntlzd rNEG, rNEG /* bitcount of the bit. */
andi. rNEG, rNEG, 56 /* bitcount to LS byte that differs. */
sld rWORD1, rWORD1, rNEG /* shift left to clear MS bytes. */
sld rWORD2, rWORD2, rNEG
xor. rBITDIF, rWORD1, rWORD2
sub rRTN, rWORD1, rWORD2
blt- L(highbit)
sradi rRTN, rRTN, 63 /* must return an int. */
ori rRTN, rRTN, 1
blr
L(equal):
li rRTN, 0
blr
L(different):
ld rWORD1, -8(rSTR1)
xor rBITDIF, rWORD1, rWORD2 /* rBITDIF has bits that differ. */
neg rNEG, rBITDIF
and rNEG, rNEG, rBITDIF /* rNEG has LS bit that differs. */
cntlzd rNEG, rNEG /* bitcount of the bit. */
andi. rNEG, rNEG, 56 /* bitcount to LS byte that differs. */
sld rWORD1, rWORD1, rNEG /* shift left to clear MS bytes. */
sld rWORD2, rWORD2, rNEG
xor. rBITDIF, rWORD1, rWORD2
sub rRTN, rWORD1, rWORD2
blt- L(highbit)
sradi rRTN, rRTN, 63
ori rRTN, rRTN, 1
blr
L(highbit):
sradi rRTN, rWORD2, 63
ori rRTN, rRTN, 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)
cntlzd rBITDIF, rBITDIF
cntlzd rNEG, rNEG
addi rNEG, rNEG, 7
cmpd cr1, rNEG, rBITDIF
sub rRTN, rWORD1, rWORD2
blt- cr1, L(equal)
sradi rRTN, rRTN, 63 /* must return an int. */
ori rRTN, rRTN, 1
blr
L(equal):
li rRTN, 0
blr
L(different):
ld rWORD1, -8(rSTR1)
xor. rBITDIF, rWORD1, rWORD2
sub rRTN, rWORD1, rWORD2
blt- L(highbit)
sradi rRTN, rRTN, 63
ori rRTN, rRTN, 1
blr
L(highbit):
sradi rRTN, rWORD2, 63
ori rRTN, rRTN, 1
blr
#endif
/* Oh well. In this case, we just do a byte-by-byte comparison. */
.align 4
L(tail):
and. rTMP, rTMP, rNEG
cmpd cr1, rWORD1, rWORD2
bne- L(endstring)
addi rSTR1, rSTR1, 8
bne- cr1, L(different)
addi rSTR2, rSTR2, 8
cmpldi cr1, rN, 0
L(unaligned):
mtctr rN /* Power4 wants mtctr 1st in dispatch group */
bgt cr1, L(uz)
L(ux):
li rRTN, 0
blr
.align 4
L(uz):
lbz rWORD1, 0(rSTR1)
lbz rWORD2, 0(rSTR2)
nop
b L(u1)
L(u0):
lbzu rWORD2, 1(rSTR2)
L(u1):
bdz L(u3)
cmpdi cr1, rWORD1, 0
cmpd rWORD1, rWORD2
beq- cr1, L(u3)
lbzu rWORD1, 1(rSTR1)
bne- L(u2)
lbzu rWORD2, 1(rSTR2)
bdz L(u3)
cmpdi cr1, rWORD1, 0
cmpd rWORD1, rWORD2
bne- L(u3)
lbzu rWORD1, 1(rSTR1)
bne+ cr1, L(u0)
L(u2): lbzu rWORD1, -1(rSTR1)
L(u3): sub rRTN, rWORD1, rWORD2
blr
END (STRNCMP)
libc_hidden_builtin_def (strncmp)
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