libc/arch-riscv64/string/strncmp_v.S

/*
 * Copyright (C) 2023 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.
 */
/*
 * Copyright (c) 2023 SiFive, Inc.
 * 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 SIFIVE INC ``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 SIFIVE INC 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>

#define iResult a0

#define pStr1 a0
#define pStr2 a1
#define iLength a2

#define iVL a3
#define iTemp1 a4
#define iTemp2 a5

#define ELEM_LMUL_SETTING m1
#define vStr1 v0
#define vStr2 v4
#define vMask1 v8
#define vMask2 v9

ENTRY(strncmp_v)

    beqz iLength, L(zero_length)

L(loop):
    vsetvli iVL, iLength, e8, ELEM_LMUL_SETTING, ta, ma

    vle8ff.v vStr1, (pStr1)
     # vStr1[i] == 0
    vmseq.vx vMask1, vStr1, zero

    vle8ff.v vStr2, (pStr2)
    # vStr1[i] != vStr2[i]
    vmsne.vv vMask2, vStr1, vStr2

    csrr iVL, vl

    # r = mask1 | mask2
    # We could use vfirst.m to get the first zero char or the
    # first different char between str1 and str2.
    vmor.mm vMask1, vMask1, vMask2

    sub iLength, iLength, iVL

    vfirst.m iTemp1, vMask1

    bgez iTemp1, L(end_loop)

    add pStr1, pStr1, iVL
    add pStr2, pStr2, iVL
    bnez iLength, L(loop)
L(end_loop):

    add pStr1, pStr1, iTemp1
    add pStr2, pStr2, iTemp1
    lbu iTemp1, 0(pStr1)
    lbu iTemp2, 0(pStr2)

    sub iResult, iTemp1, iTemp2
    ret

L(zero_length):
    li iResult, 0
    ret

END(strncmp_v)