1// Inferno's libkern/memmove-386.s 2// https://bitbucket.org/inferno-os/inferno-os/src/default/libkern/memmove-386.s 3// 4// Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved. 5// Revisions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com). All rights reserved. 6// Portions Copyright 2009 The Go Authors. All rights reserved. 7// 8// Permission is hereby granted, free of charge, to any person obtaining a copy 9// of this software and associated documentation files (the "Software"), to deal 10// in the Software without restriction, including without limitation the rights 11// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 12// copies of the Software, and to permit persons to whom the Software is 13// furnished to do so, subject to the following conditions: 14// 15// The above copyright notice and this permission notice shall be included in 16// all copies or substantial portions of the Software. 17// 18// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 19// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 20// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 21// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 22// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 23// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 24// THE SOFTWARE. 25 26#include "textflag.h" 27 28// See memmove Go doc for important implementation constraints. 29 30// func memmove(to, from unsafe.Pointer, n uintptr) 31TEXT runtime·memmove(SB), NOSPLIT, $0-12 32 MOVL to+0(FP), DI 33 MOVL from+4(FP), SI 34 MOVL n+8(FP), BX 35 36 // REP instructions have a high startup cost, so we handle small sizes 37 // with some straightline code. The REP MOVSL instruction is really fast 38 // for large sizes. The cutover is approximately 1K. 39tail: 40 TESTL BX, BX 41 JEQ move_0 42 CMPL BX, $2 43 JBE move_1or2 44 CMPL BX, $4 45 JB move_3 46 JE move_4 47 CMPL BX, $8 48 JBE move_5through8 49 CMPL BX, $16 50 JBE move_9through16 51 52/* 53 * check and set for backwards 54 */ 55 CMPL SI, DI 56 JLS back 57 58/* 59 * forward copy loop 60 */ 61forward: 62 MOVL BX, CX 63 SHRL $2, CX 64 ANDL $3, BX 65 66 REP; MOVSL 67 JMP tail 68/* 69 * check overlap 70 */ 71back: 72 MOVL SI, CX 73 ADDL BX, CX 74 CMPL CX, DI 75 JLS forward 76/* 77 * whole thing backwards has 78 * adjusted addresses 79 */ 80 81 ADDL BX, DI 82 ADDL BX, SI 83 STD 84 85/* 86 * copy 87 */ 88 MOVL BX, CX 89 SHRL $2, CX 90 ANDL $3, BX 91 92 SUBL $4, DI 93 SUBL $4, SI 94 REP; MOVSL 95 96 CLD 97 ADDL $4, DI 98 ADDL $4, SI 99 SUBL BX, DI 100 SUBL BX, SI 101 JMP tail 102 103move_1or2: 104 MOVB (SI), AX 105 MOVB -1(SI)(BX*1), CX 106 MOVB AX, (DI) 107 MOVB CX, -1(DI)(BX*1) 108 RET 109move_0: 110 RET 111move_3: 112 MOVW (SI), AX 113 MOVB 2(SI), CX 114 MOVW AX, (DI) 115 MOVB CX, 2(DI) 116 RET 117move_4: 118 // We need a separate case for 4 to make sure we write pointers atomically. 119 MOVL (SI), AX 120 MOVL AX, (DI) 121 RET 122move_5through8: 123 MOVL (SI), AX 124 MOVL -4(SI)(BX*1), CX 125 MOVL AX, (DI) 126 MOVL CX, -4(DI)(BX*1) 127 RET 128move_9through16: 129 MOVL (SI), AX 130 MOVL 4(SI), CX 131 MOVL -8(SI)(BX*1), DX 132 MOVL -4(SI)(BX*1), BP 133 MOVL AX, (DI) 134 MOVL CX, 4(DI) 135 MOVL DX, -8(DI)(BX*1) 136 MOVL BP, -4(DI)(BX*1) 137 RET 138