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/* Optimized strcmp implementation for PowerPC32.
Copyright (C) 2003, 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, see
<http://www.gnu.org/licenses/>. */
#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)
#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 rFEFE r8 /* constant 0xfefefeff (-0x01010101) */
#define r7F7F r9 /* constant 0x7f7f7f7f */
#define rNEG r10 /* ~(word in s1 | 0x7f7f7f7f) */
#define rBITDIF r11 /* bits that differ in s1 & s2 words */
dcbt 0,rSTR1
or rTMP, rSTR2, rSTR1
lis r7F7F, 0x7f7f
dcbt 0,rSTR2
clrlwi. rTMP, rTMP, 30
cmplwi cr1, rN, 0
lis rFEFE, -0x101
bne L(unaligned)
/* We are word alligned so set up for two loops. first a word
loop, then fall into the byte loop if any residual. */
srwi. rTMP, rN, 2
clrlwi rN, rN, 30
addi rFEFE, rFEFE, -0x101
addi r7F7F, r7F7F, 0x7f7f
cmplwi cr1, rN, 0
beq L(unaligned)
mtctr rTMP /* Power4 wants mtctr 1st in dispatch group. */
lwz rWORD1, 0(rSTR1)
lwz rWORD2, 0(rSTR2)
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
bdz L(tail)
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... */
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
blt- cr1, L(equal)
srawi rRTN, rRTN, 31
ori rRTN, rRTN, 1
blr
L(equal):
li rRTN, 0
blr
L(different):
lwzu rWORD1, -4(rSTR1)
xor. rBITDIF, rWORD1, rWORD2
sub rRTN, rWORD1, rWORD2
blt- L(highbit)
srawi rRTN, rRTN, 31
ori rRTN, rRTN, 1
blr
L(highbit):
srwi rWORD2, rWORD2, 24
srwi rWORD1, rWORD1, 24
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
cmpw cr1, rWORD1, rWORD2
bne- L(endstring)
addi rSTR1, rSTR1, 4
bne- cr1, L(different)
addi rSTR2, rSTR2, 4
cmplwi 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)
cmpwi cr1, rWORD1, 0
cmpw rWORD1, rWORD2
beq- cr1, L(u3)
lbzu rWORD1, 1(rSTR1)
bne- L(u2)
lbzu rWORD2, 1(rSTR2)
bdz L(u3)
cmpwi cr1, rWORD1, 0
cmpw 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 (BP_SYM (strncmp))
libc_hidden_builtin_def (strncmp)
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