github.com/mtsmfm/go/src@v0.0.0-20221020090648-44bdcb9f8fde/runtime/memmove_riscv64.s (about) 1 // Copyright 2016 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 #include "textflag.h" 6 7 // See memmove Go doc for important implementation constraints. 8 9 // void runtime·memmove(void*, void*, uintptr) 10 TEXT runtime·memmove<ABIInternal>(SB),NOSPLIT,$-0-24 11 #ifndef GOEXPERIMENT_regabiargs 12 MOV to+0(FP), A0 13 MOV from+8(FP), A1 14 MOV n+16(FP), A2 15 #endif 16 ADD A1, A2, T5 17 18 // If the destination is ahead of the source, start at the end of the 19 // buffer and go backward. 20 BLTU A1, A0, b 21 22 // If less than eight bytes, do one byte at a time. 23 SLTU $8, A2, T3 24 BNE T3, ZERO, f_outcheck 25 26 // Do one byte at a time until from is eight-aligned. 27 JMP f_aligncheck 28 f_align: 29 MOVB (A1), T3 30 MOVB T3, (A0) 31 ADD $1, A0 32 ADD $1, A1 33 f_aligncheck: 34 AND $7, A1, T3 35 BNE T3, ZERO, f_align 36 37 // Do eight bytes at a time as long as there is room. 38 ADD $-7, T5, T6 39 JMP f_wordscheck 40 f_words: 41 MOV (A1), T3 42 MOV T3, (A0) 43 ADD $8, A0 44 ADD $8, A1 45 f_wordscheck: 46 SLTU T6, A1, T3 47 BNE T3, ZERO, f_words 48 49 // Finish off the remaining partial word. 50 JMP f_outcheck 51 f_out: 52 MOVB (A1), T3 53 MOVB T3, (A0) 54 ADD $1, A0 55 ADD $1, A1 56 f_outcheck: 57 BNE A1, T5, f_out 58 59 RET 60 61 b: 62 ADD A0, A2, T4 63 // If less than eight bytes, do one byte at a time. 64 SLTU $8, A2, T3 65 BNE T3, ZERO, b_outcheck 66 67 // Do one byte at a time until from+n is eight-aligned. 68 JMP b_aligncheck 69 b_align: 70 ADD $-1, T4 71 ADD $-1, T5 72 MOVB (T5), T3 73 MOVB T3, (T4) 74 b_aligncheck: 75 AND $7, T5, T3 76 BNE T3, ZERO, b_align 77 78 // Do eight bytes at a time as long as there is room. 79 ADD $7, A1, T6 80 JMP b_wordscheck 81 b_words: 82 ADD $-8, T4 83 ADD $-8, T5 84 MOV (T5), T3 85 MOV T3, (T4) 86 b_wordscheck: 87 SLTU T5, T6, T3 88 BNE T3, ZERO, b_words 89 90 // Finish off the remaining partial word. 91 JMP b_outcheck 92 b_out: 93 ADD $-1, T4 94 ADD $-1, T5 95 MOVB (T5), T3 96 MOVB T3, (T4) 97 b_outcheck: 98 BNE T5, A1, b_out 99 100 RET