1 // Copyright 2014 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 // void runtimememmove(void*, void*, uintptr) 8 TEXT runtimememmove(SB), NOSPLIT, $-8-24 9 MOVD to+0(FP), R3 10 MOVD from+8(FP), R4 11 MOVD n+16(FP), R5 12 CMP $0, R5 13 BNE check 14 RET 15 16 check: 17 AND $~7, R5, R7 // R7 is N&~7 18 // TODO(mwhudson): this is written this way to avoid tickling 19 // warnings from addpool when written as AND $7, R5, R6 (see 20 // https://golang.org/issue/12708) 21 SUB R7, R5, R6 // R6 is N&7 22 23 CMP R3, R4 24 BLT backward 25 26 // Copying forward proceeds by copying R7/8 words then copying R6 bytes. 27 // R3 and R4 are advanced as we copy. 28 29 // (There may be implementations of armv8 where copying by bytes until 30 // at least one of source or dest is word aligned is a worthwhile 31 // optimization, but the on the one tested so far (xgene) it did not 32 // make a significance difference.) 33 34 CMP $0, R7 // Do we need to do any word-by-word copying? 35 BEQ noforwardlarge 36 37 ADD R3, R7, R9 // R9 points just past where we copy by word 38 39 forwardlargeloop: 40 MOVD.P 8(R4), R8 // R8 is just a scratch register 41 MOVD.P R8, 8(R3) 42 CMP R3, R9 43 BNE forwardlargeloop 44 45 noforwardlarge: 46 CMP $0, R6 // Do we need to do any byte-by-byte copying? 47 BNE forwardtail 48 RET 49 50 forwardtail: 51 ADD R3, R6, R9 // R9 points just past the destination memory 52 53 forwardtailloop: 54 MOVBU.P 1(R4), R8 55 MOVBU.P R8, 1(R3) 56 CMP R3, R9 57 BNE forwardtailloop 58 RET 59 60 backward: 61 // Copying backwards proceeds by copying R6 bytes then copying R7/8 words. 62 // R3 and R4 are advanced to the end of the destination/source buffers 63 // respectively and moved back as we copy. 64 65 ADD R4, R5, R4 // R4 points just past the last source byte 66 ADD R3, R5, R3 // R3 points just past the last destination byte 67 68 CMP $0, R6 // Do we need to do any byte-by-byte copying? 69 BEQ nobackwardtail 70 71 SUB R6, R3, R9 // R9 points at the lowest destination byte that should be copied by byte. 72 backwardtailloop: 73 MOVBU.W -1(R4), R8 74 MOVBU.W R8, -1(R3) 75 CMP R9, R3 76 BNE backwardtailloop 77 78 nobackwardtail: 79 CMP $0, R7 // Do we need to do any word-by-word copying? 80 BNE backwardlarge 81 RET 82 83 backwardlarge: 84 SUB R7, R3, R9 // R9 points at the lowest destination byte 85 86 backwardlargeloop: 87 MOVD.W -8(R4), R8 88 MOVD.W R8, -8(R3) 89 CMP R9, R3 90 BNE backwardlargeloop 91 RET 92
