xref: /bionic/libc/arch-arm/bionic/memset.S

/*
 * Copyright (C) 2008 The Android Open Source Project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *  * Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *  * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "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 THE
 * COPYRIGHT OWNER OR CONTRIBUTORS 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/asm.h>

		/*
		 * Optimized memset() for ARM.
         *
         * memset() returns its first argument.
		 */

ENTRY(bzero)
        mov     r2, r1
        mov     r1, #0
END(bzero)

ENTRY(memset)
		/* compute the offset to align the destination
		 * offset = (4-(src&3))&3 = -src & 3
		 */
        .save       {r0, r4-r7, lr}
		stmfd		sp!, {r0, r4-r7, lr}
		rsb			r3, r0, #0
		ands		r3, r3, #3
        cmp         r3, r2
        movhi       r3, r2

        /* splat r1 */
        mov         r1, r1, lsl #24
        orr         r1, r1, r1, lsr #8
        orr         r1, r1, r1, lsr #16

		movs		r12, r3, lsl #31
		strcsb		r1, [r0], #1    /* can't use strh (alignment unknown) */
		strcsb		r1, [r0], #1
		strmib		r1, [r0], #1
		subs		r2, r2, r3
        ldmlsfd     sp!, {r0, r4-r7, lr}   /* return */
        bxls        lr

		/* align the destination to a cache-line */
        mov         r12, r1
        mov         lr, r1
        mov         r4, r1
        mov         r5, r1
        mov         r6, r1
        mov         r7, r1

		rsb         r3, r0, #0
		ands		r3, r3, #0x1C
		beq         3f
		cmp         r3, r2
		andhi		r3, r2, #0x1C
		sub         r2, r2, r3

		/* conditionnaly writes 0 to 7 words (length in r3) */
		movs		r3, r3, lsl #28
		stmcsia		r0!, {r1, lr}
		stmcsia		r0!, {r1, lr}
		stmmiia		r0!, {r1, lr}
		movs		r3, r3, lsl #2
        strcs       r1, [r0], #4

3:
        subs        r2, r2, #32
        mov         r3, r1
        bmi         2f
1:      subs        r2, r2, #32
        stmia		r0!, {r1,r3,r4,r5,r6,r7,r12,lr}
        bhs         1b
2:      add         r2, r2, #32

		/* conditionnaly stores 0 to 31 bytes */
		movs		r2, r2, lsl #28
		stmcsia		r0!, {r1,r3,r12,lr}
		stmmiia		r0!, {r1, lr}
		movs		r2, r2, lsl #2
        strcs       r1, [r0], #4
		strmih		r1, [r0], #2
		movs		r2, r2, lsl #2
		strcsb		r1, [r0]
        ldmfd		sp!, {r0, r4-r7, lr}
        bx          lr
END(memset)