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/*
* Copyright (c) 2011 The Android Open Source Project
* Copyright (c) 2008 ARM Ltd
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the company may not be used to endorse or promote
* products derived from this software without specific prior written
* permission.
*
* THIS SOFTWARE IS PROVIDED BY ARM LTD ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL ARM LTD BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
* TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include <private/bionic_asm.h>
.text
#ifdef __ARMEB__
#define SHFT2LSB lsl
#define SHFT2LSBEQ lsleq
#define SHFT2MSB lsr
#define SHFT2MSBEQ lsreq
#define MSB 0x000000ff
#define LSB 0xff000000
#else
#define SHFT2LSB lsr
#define SHFT2LSBEQ lsreq
#define SHFT2MSB lsl
#define SHFT2MSBEQ lsleq
#define MSB 0xff000000
#define LSB 0x000000ff
#endif
#define magic1(REG) REG
#define magic2(REG) REG, lsl #7
ENTRY(strcmp)
pld [r0, #0]
pld [r1, #0]
eor r2, r0, r1
tst r2, #3
/* Strings not at same byte offset from a word boundary. */
bne .Lstrcmp_unaligned
ands r2, r0, #3
bic r0, r0, #3
bic r1, r1, #3
ldr ip, [r0], #4
it eq
ldreq r3, [r1], #4
beq 1f
/* Although s1 and s2 have identical initial alignment, they are
* not currently word aligned. Rather than comparing bytes,
* make sure that any bytes fetched from before the addressed
* bytes are forced to 0xff. Then they will always compare
* equal.
*/
eor r2, r2, #3
lsl r2, r2, #3
mvn r3, #MSB
SHFT2LSB r2, r3, r2
ldr r3, [r1], #4
orr ip, ip, r2
orr r3, r3, r2
1:
/* Load the 'magic' constant 0x01010101. */
str r4, [sp, #-4]!
mov r4, #1
orr r4, r4, r4, lsl #8
orr r4, r4, r4, lsl #16
.p2align 2
4:
pld [r0, #8]
pld [r1, #8]
sub r2, ip, magic1(r4)
cmp ip, r3
itttt eq
/* check for any zero bytes in first word */
biceq r2, r2, ip
tsteq r2, magic2(r4)
ldreq ip, [r0], #4
ldreq r3, [r1], #4
beq 4b
2:
/* There's a zero or a different byte in the word */
SHFT2MSB r0, ip, #24
SHFT2LSB ip, ip, #8
cmp r0, #1
it cs
cmpcs r0, r3, SHFT2MSB #24
it eq
SHFT2LSBEQ r3, r3, #8
beq 2b
/* On a big-endian machine, r0 contains the desired byte in bits
* 0-7; on a little-endian machine they are in bits 24-31. In
* both cases the other bits in r0 are all zero. For r3 the
* interesting byte is at the other end of the word, but the
* other bits are not necessarily zero. We need a signed result
* representing the differnece in the unsigned bytes, so for the
* little-endian case we can't just shift the interesting bits up.
*/
#ifdef __ARMEB__
sub r0, r0, r3, lsr #24
#else
and r3, r3, #255
/* No RSB instruction in Thumb2 */
#ifdef __thumb2__
lsr r0, r0, #24
sub r0, r0, r3
#else
rsb r0, r3, r0, lsr #24
#endif
#endif
ldr r4, [sp], #4
bx lr
.Lstrcmp_unaligned:
wp1 .req r0
wp2 .req r1
b1 .req r2
w1 .req r4
w2 .req r5
t1 .req ip
@ r3 is scratch
/* First of all, compare bytes until wp1(sp1) is word-aligned. */
1:
tst wp1, #3
beq 2f
ldrb r2, [wp1], #1
ldrb r3, [wp2], #1
cmp r2, #1
it cs
cmpcs r2, r3
beq 1b
sub r0, r2, r3
bx lr
2:
str r5, [sp, #-4]!
str r4, [sp, #-4]!
mov b1, #1
orr b1, b1, b1, lsl #8
orr b1, b1, b1, lsl #16
and t1, wp2, #3
bic wp2, wp2, #3
ldr w1, [wp1], #4
ldr w2, [wp2], #4
cmp t1, #2
beq 2f
bhi 3f
/* Critical inner Loop: Block with 3 bytes initial overlap */
.p2align 2
1:
bic t1, w1, #MSB
cmp t1, w2, SHFT2LSB #8
sub r3, w1, b1
bic r3, r3, w1
bne 4f
ands r3, r3, b1, lsl #7
it eq
ldreq w2, [wp2], #4
bne 5f
eor t1, t1, w1
cmp t1, w2, SHFT2MSB #24
bne 6f
ldr w1, [wp1], #4
b 1b
4:
SHFT2LSB w2, w2, #8
b 8f
5:
#ifdef __ARMEB__
/* The syndrome value may contain false ones if the string ends
* with the bytes 0x01 0x00
*/
tst w1, #0xff000000
itt ne
tstne w1, #0x00ff0000
tstne w1, #0x0000ff00
beq 7f
#else
bics r3, r3, #0xff000000
bne 7f
#endif
ldrb w2, [wp2]
SHFT2LSB t1, w1, #24
#ifdef __ARMEB__
lsl w2, w2, #24
#endif
b 8f
6:
SHFT2LSB t1, w1, #24
and w2, w2, #LSB
b 8f
/* Critical inner Loop: Block with 2 bytes initial overlap */
.p2align 2
2:
SHFT2MSB t1, w1, #16
sub r3, w1, b1
SHFT2LSB t1, t1, #16
bic r3, r3, w1
cmp t1, w2, SHFT2LSB #16
bne 4f
ands r3, r3, b1, lsl #7
it eq
ldreq w2, [wp2], #4
bne 5f
eor t1, t1, w1
cmp t1, w2, SHFT2MSB #16
bne 6f
ldr w1, [wp1], #4
b 2b
5:
#ifdef __ARMEB__
/* The syndrome value may contain false ones if the string ends
* with the bytes 0x01 0x00
*/
tst w1, #0xff000000
it ne
tstne w1, #0x00ff0000
beq 7f
#else
lsls r3, r3, #16
bne 7f
#endif
ldrh w2, [wp2]
SHFT2LSB t1, w1, #16
#ifdef __ARMEB__
lsl w2, w2, #16
#endif
b 8f
6:
SHFT2MSB w2, w2, #16
SHFT2LSB t1, w1, #16
4:
SHFT2LSB w2, w2, #16
b 8f
/* Critical inner Loop: Block with 1 byte initial overlap */
.p2align 2
3:
and t1, w1, #LSB
cmp t1, w2, SHFT2LSB #24
sub r3, w1, b1
bic r3, r3, w1
bne 4f
ands r3, r3, b1, lsl #7
it eq
ldreq w2, [wp2], #4
bne 5f
eor t1, t1, w1
cmp t1, w2, SHFT2MSB #8
bne 6f
ldr w1, [wp1], #4
b 3b
4:
SHFT2LSB w2, w2, #24
b 8f
5:
/* The syndrome value may contain false ones if the string ends
* with the bytes 0x01 0x00
*/
tst w1, #LSB
beq 7f
ldr w2, [wp2], #4
6:
SHFT2LSB t1, w1, #8
bic w2, w2, #MSB
b 8f
7:
mov r0, #0
ldr r4, [sp], #4
ldr r5, [sp], #4
bx lr
8:
and r2, t1, #LSB
and r0, w2, #LSB
cmp r0, #1
it cs
cmpcs r0, r2
itt eq
SHFT2LSBEQ t1, t1, #8
SHFT2LSBEQ w2, w2, #8
beq 8b
sub r0, r2, r0
ldr r4, [sp], #4
ldr r5, [sp], #4
bx lr
END(strcmp)