1/* 2 * OpenRISC memset.S 3 * 4 * Hand-optimized assembler version of memset for OpenRISC. 5 * Algorithm inspired by several other arch-specific memset routines 6 * in the kernel tree 7 * 8 * Copyright (C) 2015 Olof Kindgren <olof.kindgren@gmail.com> 9 * 10 * This program is free software; you can redistribute it and/or 11 * modify it under the terms of the GNU General Public License 12 * as published by the Free Software Foundation; either version 13 * 2 of the License, or (at your option) any later version. 14 */ 15 16 .global memset 17 .type memset, @function 18memset: 19 /* arguments: 20 * r3 = *s 21 * r4 = c 22 * r5 = n 23 * r13, r15, r17, r19 used as temp regs 24 */ 25 26 /* Exit if n == 0 */ 27 l.sfeqi r5, 0 28 l.bf 4f 29 30 /* Truncate c to char */ 31 l.andi r13, r4, 0xff 32 33 /* Skip word extension if c is 0 */ 34 l.sfeqi r13, 0 35 l.bf 1f 36 /* Check for at least two whole words (8 bytes) */ 37 l.sfleui r5, 7 38 39 /* Extend char c to 32-bit word cccc in r13 */ 40 l.slli r15, r13, 16 // r13 = 000c, r15 = 0c00 41 l.or r13, r13, r15 // r13 = 0c0c, r15 = 0c00 42 l.slli r15, r13, 8 // r13 = 0c0c, r15 = c0c0 43 l.or r13, r13, r15 // r13 = cccc, r15 = c0c0 44 451: l.addi r19, r3, 0 // Set r19 = src 46 /* Jump to byte copy loop if less than two words */ 47 l.bf 3f 48 l.or r17, r5, r0 // Set r17 = n 49 50 /* Mask out two LSBs to check alignment */ 51 l.andi r15, r3, 0x3 52 53 /* lsb == 00, jump to word copy loop */ 54 l.sfeqi r15, 0 55 l.bf 2f 56 l.addi r19, r3, 0 // Set r19 = src 57 58 /* lsb == 01,10 or 11 */ 59 l.sb 0(r3), r13 // *src = c 60 l.addi r17, r17, -1 // Decrease n 61 62 l.sfeqi r15, 3 63 l.bf 2f 64 l.addi r19, r3, 1 // src += 1 65 66 /* lsb == 01 or 10 */ 67 l.sb 1(r3), r13 // *(src+1) = c 68 l.addi r17, r17, -1 // Decrease n 69 70 l.sfeqi r15, 2 71 l.bf 2f 72 l.addi r19, r3, 2 // src += 2 73 74 /* lsb == 01 */ 75 l.sb 2(r3), r13 // *(src+2) = c 76 l.addi r17, r17, -1 // Decrease n 77 l.addi r19, r3, 3 // src += 3 78 79 /* Word copy loop */ 802: l.sw 0(r19), r13 // *src = cccc 81 l.addi r17, r17, -4 // Decrease n 82 l.sfgeui r17, 4 83 l.bf 2b 84 l.addi r19, r19, 4 // Increase src 85 86 /* When n > 0, copy the remaining bytes, otherwise jump to exit */ 87 l.sfeqi r17, 0 88 l.bf 4f 89 90 /* Byte copy loop */ 913: l.addi r17, r17, -1 // Decrease n 92 l.sb 0(r19), r13 // *src = cccc 93 l.sfnei r17, 0 94 l.bf 3b 95 l.addi r19, r19, 1 // Increase src 96 974: l.jr r9 98 l.ori r11, r3, 0 99