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/* Optimized strcmp implementation for POWER7/PowerPC64.
Copyright (C) 2010, 2011 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, write to the Free
Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA
02110-1301 USA. */
#include <sysdep.h>
#include <bp-sym.h>
#include <bp-asm.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]) */
EALIGN (BP_SYM(strncmp),4,0)
CALL_MCOUNT 3
#define rTMP r0
#define rRTN r3
#define rSTR1 r3 /* first string arg */
#define rSTR2 r4 /* second string arg */
#define rN r5 /* max string length */
/* Note: The Bounded pointer support in this code is broken. This code
was inherited from PPC32 and that support was never completed.
Current PPC gcc does not support -fbounds-check or -fbounded-pointers. */
#define rWORD1 r6 /* current word in s1 */
#define rWORD2 r7 /* current word in s2 */
#define rWORD3 r10
#define rWORD4 r11
#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 */
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 alligned 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
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... */
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
ori rRTN,rRTN,1
blr
L(equal):
li rRTN,0
blr
L(different):
ldu 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):
srdi rWORD2,rWORD2,56
srdi rWORD1,rWORD1,56
sub rRTN,rWORD1,rWORD2
blr
/* 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
ble cr1,L(ux)
L(uz):
lbz rWORD1,0(rSTR1)
lbz rWORD2,0(rSTR2)
.align 4
L(u1):
cmpdi cr1,rWORD1,0
bdz L(u4)
cmpd rWORD1,rWORD2
beq cr1,L(u4)
bne L(u4)
lbzu rWORD3,1(rSTR1)
lbzu rWORD4,1(rSTR2)
cmpdi cr1,rWORD3,0
bdz L(u3)
cmpd rWORD3,rWORD4
beq cr1,L(u3)
bne L(u3)
lbzu rWORD1,1(rSTR1)
lbzu rWORD2,1(rSTR2)
cmpdi cr1,rWORD1,0
bdz L(u4)
cmpd rWORD1,rWORD2
beq cr1,L(u4)
bne L(u4)
lbzu rWORD3,1(rSTR1)
lbzu rWORD4,1(rSTR2)
cmpdi cr1,rWORD3,0
bdz L(u3)
cmpd rWORD3,rWORD4
beq cr1,L(u3)
bne L(u3)
lbzu rWORD1,1(rSTR1)
lbzu rWORD2,1(rSTR2)
b L(u1)
L(u3): sub rRTN,rWORD3,rWORD4
blr
L(u4): sub rRTN,rWORD1,rWORD2
blr
L(ux):
li rRTN,0
blr
END (BP_SYM (strncmp))
libc_hidden_builtin_def (strncmp)
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