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94 lines
2.1 KiB
94 lines
2.1 KiB
/* SPDX-License-Identifier: GPL-2.0-or-later */ |
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/* |
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* OpenRISC memset.S |
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* |
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* Hand-optimized assembler version of memset for OpenRISC. |
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* Algorithm inspired by several other arch-specific memset routines |
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* in the kernel tree |
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* |
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* Copyright (C) 2015 Olof Kindgren <olof.kindgren@gmail.com> |
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*/ |
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.global memset |
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.type memset, @function |
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memset: |
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/* arguments: |
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* r3 = *s |
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* r4 = c |
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* r5 = n |
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* r13, r15, r17, r19 used as temp regs |
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*/ |
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/* Exit if n == 0 */ |
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l.sfeqi r5, 0 |
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l.bf 4f |
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/* Truncate c to char */ |
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l.andi r13, r4, 0xff |
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/* Skip word extension if c is 0 */ |
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l.sfeqi r13, 0 |
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l.bf 1f |
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/* Check for at least two whole words (8 bytes) */ |
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l.sfleui r5, 7 |
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/* Extend char c to 32-bit word cccc in r13 */ |
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l.slli r15, r13, 16 // r13 = 000c, r15 = 0c00 |
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l.or r13, r13, r15 // r13 = 0c0c, r15 = 0c00 |
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l.slli r15, r13, 8 // r13 = 0c0c, r15 = c0c0 |
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l.or r13, r13, r15 // r13 = cccc, r15 = c0c0 |
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1: l.addi r19, r3, 0 // Set r19 = src |
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/* Jump to byte copy loop if less than two words */ |
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l.bf 3f |
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l.or r17, r5, r0 // Set r17 = n |
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/* Mask out two LSBs to check alignment */ |
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l.andi r15, r3, 0x3 |
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/* lsb == 00, jump to word copy loop */ |
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l.sfeqi r15, 0 |
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l.bf 2f |
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l.addi r19, r3, 0 // Set r19 = src |
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/* lsb == 01,10 or 11 */ |
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l.sb 0(r3), r13 // *src = c |
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l.addi r17, r17, -1 // Decrease n |
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l.sfeqi r15, 3 |
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l.bf 2f |
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l.addi r19, r3, 1 // src += 1 |
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/* lsb == 01 or 10 */ |
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l.sb 1(r3), r13 // *(src+1) = c |
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l.addi r17, r17, -1 // Decrease n |
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l.sfeqi r15, 2 |
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l.bf 2f |
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l.addi r19, r3, 2 // src += 2 |
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/* lsb == 01 */ |
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l.sb 2(r3), r13 // *(src+2) = c |
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l.addi r17, r17, -1 // Decrease n |
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l.addi r19, r3, 3 // src += 3 |
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/* Word copy loop */ |
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2: l.sw 0(r19), r13 // *src = cccc |
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l.addi r17, r17, -4 // Decrease n |
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l.sfgeui r17, 4 |
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l.bf 2b |
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l.addi r19, r19, 4 // Increase src |
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/* When n > 0, copy the remaining bytes, otherwise jump to exit */ |
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l.sfeqi r17, 0 |
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l.bf 4f |
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/* Byte copy loop */ |
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3: l.addi r17, r17, -1 // Decrease n |
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l.sb 0(r19), r13 // *src = cccc |
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l.sfnei r17, 0 |
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l.bf 3b |
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l.addi r19, r19, 1 // Increase src |
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4: l.jr r9 |
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l.ori r11, r3, 0
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