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Diffstat (limited to '')
| -rw-r--r-- | arch/openrisc/lib/memset.S | 98 |
1 files changed, 98 insertions, 0 deletions
diff --git a/arch/openrisc/lib/memset.S b/arch/openrisc/lib/memset.S new file mode 100644 index 000000000..92cc2eac2 --- /dev/null +++ b/arch/openrisc/lib/memset.S @@ -0,0 +1,98 @@ +/* + * 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> + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + */ + + .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 |