libc/arch-arm/bionic/strcmp.S - android_bionic - Gitiles

 /*
  * 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 <machine/cpu-features.h>

 	.text

 	.global strcmp
 	.type strcmp, %function
 	.align 4

 #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

 strcmp:
 	.fnstart
 	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
 	.fnend

 .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
	/*
	* 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 <machine/cpu-features.h>

	.text

	.global strcmp
	.type strcmp, %function
	.align 4

	#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

	strcmp:
	.fnstart
	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
	.fnend

	.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