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strcmp.S
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/* Copyright (C) 2014-2018 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/>. */
#ifdef ANDROID_CHANGES
# include "machine/asm.h"
# include "machine/regdef.h"
#elif _LIBC
# include <sysdep.h>
# include <regdef.h>
# include <sys/asm.h>
#elif defined _COMPILING_NEWLIB
# include "machine/asm.h"
# include "machine/regdef.h"
#else
# include <regdef.h>
# include <sys/asm.h>
#endif
/* Technically strcmp should not read past the end of the strings being
compared. We will read a full word that may contain excess bits beyond
the NULL string terminator but unless ENABLE_READAHEAD is set, we will not
read the next word after the end of string. Setting ENABLE_READAHEAD will
improve performance but is technically illegal based on the definition of
strcmp. */
#ifdef ENABLE_READAHEAD
# define DELAY_READ
#else
# define DELAY_READ nop
#endif
/* Testing on a little endian machine showed using CLZ was a
performance loss, so we are not turning it on by default. */
#if defined(ENABLE_CLZ) && (__mips_isa_rev > 1)
# define USE_CLZ
#endif
/* Some asm.h files do not have the L macro definition. */
#ifndef L
# if _MIPS_SIM == _ABIO32
# define L(label) $L ## label
# else
# define L(label) .L ## label
# endif
#endif
/* Some asm.h files do not have the PTR_ADDIU macro definition. */
#ifndef PTR_ADDIU
# ifdef USE_DOUBLE
# define PTR_ADDIU daddiu
# else
# define PTR_ADDIU addiu
# endif
#endif
/* Allow the routine to be named something else if desired. */
#ifndef STRCMP_NAME
# define STRCMP_NAME strcmp
#endif
#ifdef ANDROID_CHANGES
LEAF(STRCMP_NAME, 0)
#else
LEAF(STRCMP_NAME)
#endif
.set nomips16
.set noreorder
or t0, a0, a1
andi t0,0x3
bne t0, zero, L(byteloop)
/* Both strings are 4 byte aligned at this point. */
lui t8, 0x0101
ori t8, t8, 0x0101
lui t9, 0x7f7f
ori t9, 0x7f7f
#define STRCMP32(OFFSET) \
lw v0, OFFSET(a0); \
lw v1, OFFSET(a1); \
subu t0, v0, t8; \
bne v0, v1, L(worddiff); \
nor t1, v0, t9; \
and t0, t0, t1; \
bne t0, zero, L(returnzero)
L(wordloop):
STRCMP32(0)
DELAY_READ
STRCMP32(4)
DELAY_READ
STRCMP32(8)
DELAY_READ
STRCMP32(12)
DELAY_READ
STRCMP32(16)
DELAY_READ
STRCMP32(20)
DELAY_READ
STRCMP32(24)
DELAY_READ
STRCMP32(28)
PTR_ADDIU a0, a0, 32
b L(wordloop)
PTR_ADDIU a1, a1, 32
L(returnzero):
j ra
move v0, zero
L(worddiff):
#ifdef USE_CLZ
subu t0, v0, t8
nor t1, v0, t9
and t1, t0, t1
xor t0, v0, v1
or t0, t0, t1
# if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
wsbh t0, t0
rotr t0, t0, 16
# endif
clz t1, t0
and t1, 0xf8
# if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
neg t1
addu t1, 24
# endif
rotrv v0, v0, t1
rotrv v1, v1, t1
and v0, v0, 0xff
and v1, v1, 0xff
j ra
subu v0, v0, v1
#else /* USE_CLZ */
# if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
andi t0, v0, 0xff
beq t0, zero, L(wexit01)
andi t1, v1, 0xff
bne t0, t1, L(wexit01)
srl t8, v0, 8
srl t9, v1, 8
andi t8, t8, 0xff
beq t8, zero, L(wexit89)
andi t9, t9, 0xff
bne t8, t9, L(wexit89)
srl t0, v0, 16
srl t1, v1, 16
andi t0, t0, 0xff
beq t0, zero, L(wexit01)
andi t1, t1, 0xff
bne t0, t1, L(wexit01)
srl t8, v0, 24
srl t9, v1, 24
# else /* __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ */
srl t0, v0, 24
beq t0, zero, L(wexit01)
srl t1, v1, 24
bne t0, t1, L(wexit01)
srl t8, v0, 16
srl t9, v1, 16
andi t8, t8, 0xff
beq t8, zero, L(wexit89)
andi t9, t9, 0xff
bne t8, t9, L(wexit89)
srl t0, v0, 8
srl t1, v1, 8
andi t0, t0, 0xff
beq t0, zero, L(wexit01)
andi t1, t1, 0xff
bne t0, t1, L(wexit01)
andi t8, v0, 0xff
andi t9, v1, 0xff
# endif /* __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ */
L(wexit89):
j ra
subu v0, t8, t9
L(wexit01):
j ra
subu v0, t0, t1
#endif /* USE_CLZ */
/* It might seem better to do the 'beq' instruction between the two 'lbu'
instructions so that the nop is not needed but testing showed that this
code is actually faster (based on glibc strcmp test). */
#define BYTECMP01(OFFSET) \
lbu v0, OFFSET(a0); \
lbu v1, OFFSET(a1); \
beq v0, zero, L(bexit01); \
nop; \
bne v0, v1, L(bexit01)
#define BYTECMP89(OFFSET) \
lbu t8, OFFSET(a0); \
lbu t9, OFFSET(a1); \
beq t8, zero, L(bexit89); \
nop; \
bne t8, t9, L(bexit89)
L(byteloop):
BYTECMP01(0)
BYTECMP89(1)
BYTECMP01(2)
BYTECMP89(3)
BYTECMP01(4)
BYTECMP89(5)
BYTECMP01(6)
BYTECMP89(7)
PTR_ADDIU a0, a0, 8
b L(byteloop)
PTR_ADDIU a1, a1, 8
L(bexit01):
j ra
subu v0, v0, v1
L(bexit89):
j ra
subu v0, t8, t9
.set at
.set reorder
END(STRCMP_NAME)
#ifndef ANDROID_CHANGES
# ifdef _LIBC
libc_hidden_builtin_def (STRCMP_NAME)
# endif
#endif