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