libc/arch-arm/generic/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 <private/bionic_asm.h>

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

         .syntax unified

ENTRY(__memset_chk_generic)
        cmp         r2, r3
        bls         memset

        bl          __memset_chk_fail
END(__memset_chk_generic)

ENTRY(memset_generic)
        /* 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
        strbcs      r1, [r0], #1    /* can't use strh (alignment unknown) */
        strbcs      r1, [r0], #1
        strbmi      r1, [r0], #1
        subs        r2, r2, r3
        popls       {r0, r4-r7, pc}    /* return */

        /* 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

        /* conditionally writes 0 to 7 words (length in r3) */
        movs        r3, r3, lsl #28
        stmcs       r0!, {r1, lr}
        stmcs       r0!, {r1, lr}
        stmmi       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

        /* conditionally stores 0 to 31 bytes */
        movs        r2, r2, lsl #28
        stmcs       r0!, {r1,r3,r12,lr}
        stmmi       r0!, {r1, lr}
        movs        r2, r2, lsl #2
        strcs       r1, [r0], #4
        strhmi      r1, [r0], #2
        movs        r2, r2, lsl #2
        strbcs      r1, [r0]
        ldmfd       sp!, {r0, r4-r7, pc}
END(memset_generic)