1 /* SPDX-License-Identifier: GPL-2.0-or-later */ 2 /* 3 * OpenRISC memset.S 4 * 5 * Hand-optimized assembler version of memset for OpenRISC. 6 * Algorithm inspired by several other arch-specific memset routines 7 * in the kernel tree 8 * 9 * Copyright (C) 2015 Olof Kindgren <olof.kindgren@gmail.com> 10 */ 11 12 .global memset 13 .type memset, @function 14 memset: 15 /* arguments: 16 * r3 = *s 17 * r4 = c 18 * r5 = n 19 * r13, r15, r17, r19 used as temp regs 20 */ 21 22 /* Exit if n == 0 */ 23 l.sfeqi r5, 0 24 l.bf 4f 25 26 /* Truncate c to char */ 27 l.andi r13, r4, 0xff 28 29 /* Skip word extension if c is 0 */ 30 l.sfeqi r13, 0 31 l.bf 1f 32 /* Check for at least two whole words (8 bytes) */ 33 l.sfleui r5, 7 34 35 /* Extend char c to 32-bit word cccc in r13 */ 36 l.slli r15, r13, 16 // r13 = 000c, r15 = 0c00 37 l.or r13, r13, r15 // r13 = 0c0c, r15 = 0c00 38 l.slli r15, r13, 8 // r13 = 0c0c, r15 = c0c0 39 l.or r13, r13, r15 // r13 = cccc, r15 = c0c0 40 41 1: l.addi r19, r3, 0 // Set r19 = src 42 /* Jump to byte copy loop if less than two words */ 43 l.bf 3f 44 l.or r17, r5, r0 // Set r17 = n 45 46 /* Mask out two LSBs to check alignment */ 47 l.andi r15, r3, 0x3 48 49 /* lsb == 00, jump to word copy loop */ 50 l.sfeqi r15, 0 51 l.bf 2f 52 l.addi r19, r3, 0 // Set r19 = src 53 54 /* lsb == 01,10 or 11 */ 55 l.sb 0(r3), r13 // *src = c 56 l.addi r17, r17, -1 // Decrease n 57 58 l.sfeqi r15, 3 59 l.bf 2f 60 l.addi r19, r3, 1 // src += 1 61 62 /* lsb == 01 or 10 */ 63 l.sb 1(r3), r13 // *(src+1) = c 64 l.addi r17, r17, -1 // Decrease n 65 66 l.sfeqi r15, 2 67 l.bf 2f 68 l.addi r19, r3, 2 // src += 2 69 70 /* lsb == 01 */ 71 l.sb 2(r3), r13 // *(src+2) = c 72 l.addi r17, r17, -1 // Decrease n 73 l.addi r19, r3, 3 // src += 3 74 75 /* Word copy loop */ 76 2: l.sw 0(r19), r13 // *src = cccc 77 l.addi r17, r17, -4 // Decrease n 78 l.sfgeui r17, 4 79 l.bf 2b 80 l.addi r19, r19, 4 // Increase src 81 82 /* When n > 0, copy the remaining bytes, otherwise jump to exit */ 83 l.sfeqi r17, 0 84 l.bf 4f 85 86 /* Byte copy loop */ 87 3: l.addi r17, r17, -1 // Decrease n 88 l.sb 0(r19), r13 // *src = cccc 89 l.sfnei r17, 0 90 l.bf 3b 91 l.addi r19, r19, 1 // Increase src 92 93 4: l.jr r9 94 l.ori r11, r3, 0 95