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https://github.com/edk2-porting/linux-next.git
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71 lines
2.0 KiB
ArmAsm
71 lines
2.0 KiB
ArmAsm
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// SPDX-License-Identifier: GPL-2.0
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// Copyright (C) 2005-2017 Andes Technology Corporation
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#include <linux/linkage.h>
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/*
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void *memmove(void *dst, const void *src, int n);
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dst: $r0
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src: $r1
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n : $r2
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ret: $r0 - pointer to the memory area dst.
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*/
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.text
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ENTRY(memmove)
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move $r5, $r0 ! Set return value = det
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beq $r0, $r1, exit_memcpy ! Exit when det = src
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beqz $r2, exit_memcpy ! Exit when n = 0
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pushm $t0, $t1 ! Save reg
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srli $p1, $r2, #2 ! $p1 is how many words to copy
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! Avoid data lost when memory overlap
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! Copy data reversely when src < dst
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slt $p0, $r0, $r1 ! check if $r0 < $r1
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beqz $p0, do_reverse ! branch if dst > src
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! No reverse, dst < src
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andi $r2, $r2, #3 ! How many bytes are less than a word
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li $t0, #1 ! Determining copy direction in byte_cpy
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beqz $p1, byte_cpy ! When n is less than a word
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word_cpy:
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lmw.bim $p0, [$r1], $p0 ! Read a word from src
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addi $p1, $p1, #-1 ! How many words left to copy
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smw.bim $p0, [$r0], $p0 ! Copy the word to det
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bnez $p1, word_cpy ! If remained words > 0
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beqz $r2, end_memcpy ! No left bytes to copy
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b byte_cpy
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do_reverse:
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add $r0, $r0, $r2 ! Start with the end of $r0
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add $r1, $r1, $r2 ! Start with the end of $r1
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andi $r2, $r2, #3 ! How many bytes are less than a word
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li $t0, #-1 ! Determining copy direction in byte_cpy
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beqz $p1, reverse_byte_cpy ! When n is less than a word
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reverse_word_cpy:
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lmw.adm $p0, [$r1], $p0 ! Read a word from src
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addi $p1, $p1, #-1 ! How many words left to copy
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smw.adm $p0, [$r0], $p0 ! Copy the word to det
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bnez $p1, reverse_word_cpy ! If remained words > 0
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beqz $r2, end_memcpy ! No left bytes to copy
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reverse_byte_cpy:
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addi $r0, $r0, #-1
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addi $r1, $r1, #-1
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byte_cpy: ! Less than 4 bytes to copy now
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lb.bi $p0, [$r1], $t0 ! Read a byte from src
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addi $r2, $r2, #-1 ! How many bytes left to copy
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sb.bi $p0, [$r0], $t0 ! copy the byte to det
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bnez $r2, byte_cpy ! If remained bytes > 0
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end_memcpy:
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popm $t0, $t1
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exit_memcpy:
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move $r0, $r5
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ret
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ENDPROC(memmove)
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