1 // SPDX-License-Identifier: GPL-2.0 2 // Copyright (C) 2005-2017 Andes Technology Corporation 3 4 #include <linux/linkage.h> 5 6 /* 7 void *memmove(void *dst, const void *src, int n); 8 9 dst: $r0 10 src: $r1 11 n : $r2 12 ret: $r0 - pointer to the memory area dst. 13 */ 14 .text 15 16 ENTRY(memmove) 17 move $r5, $r0 ! Set return value = det 18 beq $r0, $r1, exit_memcpy ! Exit when det = src 19 beqz $r2, exit_memcpy ! Exit when n = 0 20 pushm $t0, $t1 ! Save reg 21 srli $p1, $r2, #2 ! $p1 is how many words to copy 22 23 ! Avoid data lost when memory overlap 24 ! Copy data reversely when src < dst 25 slt $p0, $r0, $r1 ! check if $r0 < $r1 26 beqz $p0, do_reverse ! branch if dst > src 27 28 ! No reverse, dst < src 29 andi $r2, $r2, #3 ! How many bytes are less than a word 30 li $t0, #1 ! Determining copy direction in byte_cpy 31 beqz $p1, byte_cpy ! When n is less than a word 32 33 word_cpy: 34 lmw.bim $p0, [$r1], $p0 ! Read a word from src 35 addi $p1, $p1, #-1 ! How many words left to copy 36 smw.bim $p0, [$r0], $p0 ! Copy the word to det 37 bnez $p1, word_cpy ! If remained words > 0 38 beqz $r2, end_memcpy ! No left bytes to copy 39 b byte_cpy 40 41 do_reverse: 42 add $r0, $r0, $r2 ! Start with the end of $r0 43 add $r1, $r1, $r2 ! Start with the end of $r1 44 andi $r2, $r2, #3 ! How many bytes are less than a word 45 li $t0, #-1 ! Determining copy direction in byte_cpy 46 beqz $p1, reverse_byte_cpy ! When n is less than a word 47 48 reverse_word_cpy: 49 lmw.adm $p0, [$r1], $p0 ! Read a word from src 50 addi $p1, $p1, #-1 ! How many words left to copy 51 smw.adm $p0, [$r0], $p0 ! Copy the word to det 52 bnez $p1, reverse_word_cpy ! If remained words > 0 53 beqz $r2, end_memcpy ! No left bytes to copy 54 55 reverse_byte_cpy: 56 addi $r0, $r0, #-1 57 addi $r1, $r1, #-1 58 byte_cpy: ! Less than 4 bytes to copy now 59 lb.bi $p0, [$r1], $t0 ! Read a byte from src 60 addi $r2, $r2, #-1 ! How many bytes left to copy 61 sb.bi $p0, [$r0], $t0 ! copy the byte to det 62 bnez $r2, byte_cpy ! If remained bytes > 0 63 64 end_memcpy: 65 popm $t0, $t1 66 exit_memcpy: 67 move $r0, $r5 68 ret 69 70 ENDPROC(memmove) 71