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Diffstat (limited to '')
| -rw-r--r-- | arch/nds32/lib/memmove.S | 70 |
1 files changed, 70 insertions, 0 deletions
diff --git a/arch/nds32/lib/memmove.S b/arch/nds32/lib/memmove.S new file mode 100644 index 000000000..c823aada2 --- /dev/null +++ b/arch/nds32/lib/memmove.S @@ -0,0 +1,70 @@ +// SPDX-License-Identifier: GPL-2.0 +// Copyright (C) 2005-2017 Andes Technology Corporation + +#include <linux/linkage.h> + +/* + void *memmove(void *dst, const void *src, int n); + + dst: $r0 + src: $r1 + n : $r2 + ret: $r0 - pointer to the memory area dst. +*/ + .text + +ENTRY(memmove) + move $r5, $r0 ! Set return value = det + beq $r0, $r1, exit_memcpy ! Exit when det = src + beqz $r2, exit_memcpy ! Exit when n = 0 + pushm $t0, $t1 ! Save reg + srli $p1, $r2, #2 ! $p1 is how many words to copy + + ! Avoid data lost when memory overlap + ! Copy data reversely when src < dst + slt $p0, $r0, $r1 ! check if $r0 < $r1 + beqz $p0, do_reverse ! branch if dst > src + + ! No reverse, dst < src + andi $r2, $r2, #3 ! How many bytes are less than a word + li $t0, #1 ! Determining copy direction in byte_cpy + beqz $p1, byte_cpy ! When n is less than a word + +word_cpy: + lmw.bim $p0, [$r1], $p0 ! Read a word from src + addi $p1, $p1, #-1 ! How many words left to copy + smw.bim $p0, [$r0], $p0 ! Copy the word to det + bnez $p1, word_cpy ! If remained words > 0 + beqz $r2, end_memcpy ! No left bytes to copy + b byte_cpy + +do_reverse: + add $r0, $r0, $r2 ! Start with the end of $r0 + add $r1, $r1, $r2 ! Start with the end of $r1 + andi $r2, $r2, #3 ! How many bytes are less than a word + li $t0, #-1 ! Determining copy direction in byte_cpy + beqz $p1, reverse_byte_cpy ! When n is less than a word + +reverse_word_cpy: + lmw.adm $p0, [$r1], $p0 ! Read a word from src + addi $p1, $p1, #-1 ! How many words left to copy + smw.adm $p0, [$r0], $p0 ! Copy the word to det + bnez $p1, reverse_word_cpy ! If remained words > 0 + beqz $r2, end_memcpy ! No left bytes to copy + +reverse_byte_cpy: + addi $r0, $r0, #-1 + addi $r1, $r1, #-1 +byte_cpy: ! Less than 4 bytes to copy now + lb.bi $p0, [$r1], $t0 ! Read a byte from src + addi $r2, $r2, #-1 ! How many bytes left to copy + sb.bi $p0, [$r0], $t0 ! copy the byte to det + bnez $r2, byte_cpy ! If remained bytes > 0 + +end_memcpy: + popm $t0, $t1 +exit_memcpy: + move $r0, $r5 + ret + +ENDPROC(memmove) |