/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * OpenRISC memset.S
 *
 * Hand-optimized assembler version of memset for OpenRISC.
 * Algorithm inspired by several other arch-specific memset routines
 * in the kernel tree
 *
 * Copyright (C) 2015 Olof Kindgren <olof.kindgren@gmail.com>
 */

        .global memset
        .type   memset, @function
memset:
        /* arguments:
         * r3 = *s
         * r4 = c
         * r5 = n
         * r13, r15, r17, r19 used as temp regs
        */

        /* Exit if n == 0 */
        l.sfeqi         r5, 0
        l.bf            4f

        /* Truncate c to char */
        l.andi          r13, r4, 0xff

        /* Skip word extension if c is 0 */
        l.sfeqi         r13, 0
        l.bf            1f
        /* Check for at least two whole words (8 bytes) */
         l.sfleui       r5, 7

        /* Extend char c to 32-bit word cccc in r13 */
        l.slli          r15, r13, 16  // r13 = 000c, r15 = 0c00
        l.or            r13, r13, r15 // r13 = 0c0c, r15 = 0c00
        l.slli          r15, r13, 8   // r13 = 0c0c, r15 = c0c0
        l.or            r13, r13, r15 // r13 = cccc, r15 = c0c0

1:      l.addi          r19, r3, 0 // Set r19 = src
        /* Jump to byte copy loop if less than two words */
        l.bf            3f
         l.or           r17, r5, r0 // Set r17 = n

        /* Mask out two LSBs to check alignment */
        l.andi          r15, r3, 0x3

        /* lsb == 00, jump to word copy loop */
        l.sfeqi         r15, 0
        l.bf            2f
         l.addi         r19, r3, 0 // Set r19 = src

        /* lsb == 01,10 or 11 */
        l.sb            0(r3), r13   // *src = c
        l.addi          r17, r17, -1 // Decrease n

        l.sfeqi         r15, 3
        l.bf            2f
         l.addi         r19, r3, 1  // src += 1

        /* lsb == 01 or 10 */
        l.sb            1(r3), r13   // *(src+1) = c
        l.addi          r17, r17, -1 // Decrease n

        l.sfeqi         r15, 2
        l.bf            2f
         l.addi         r19, r3, 2  // src += 2

        /* lsb == 01 */
        l.sb            2(r3), r13   // *(src+2) = c
        l.addi          r17, r17, -1 // Decrease n
        l.addi          r19, r3, 3   // src += 3

        /* Word copy loop */
2:      l.sw            0(r19), r13  // *src = cccc
        l.addi          r17, r17, -4 // Decrease n
        l.sfgeui        r17, 4
        l.bf            2b
         l.addi         r19, r19, 4  // Increase src

        /* When n > 0, copy the remaining bytes, otherwise jump to exit */
        l.sfeqi         r17, 0
        l.bf            4f

        /* Byte copy loop */
3:      l.addi          r17, r17, -1 // Decrease n
        l.sb            0(r19), r13  // *src = cccc
        l.sfnei         r17, 0
        l.bf            3b
         l.addi         r19, r19, 1  // Increase src

4:      l.jr            r9
         l.ori          r11, r3, 0