1 /* 2 * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org> 3 * 4 * Permission is hereby granted, free of charge, to any person obtaining 5 * a copy of this software and associated documentation files (the 6 * "Software"), to deal in the Software without restriction, including 7 * without limitation the rights to use, copy, modify, merge, publish, 8 * distribute, sublicense, and/or sell copies of the Software, and to 9 * permit persons to whom the Software is furnished to do so, subject to 10 * the following conditions: 11 * 12 * The above copyright notice and this permission notice shall be 13 * included in all copies or substantial portions of the Software. 14 * 15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 18 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS 19 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN 20 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN 21 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 22 * SOFTWARE. 23 */ 24 25 using System; 26 using System.Collections.Generic; 27 28 abstract class Opcode { 29 30 internal Opcode() 31 { 32 } 33 34 /* 35 * Execute this opcode. 36 */ 37 internal abstract void Run(CPU cpu); 38 39 /* 40 * Resolve the target (word reference) for this opcode. 41 */ 42 internal virtual void ResolveTarget(Word target) 43 { 44 throw new Exception("Not a call opcode"); 45 } 46 47 /* 48 * Resolve the jump offset for this opcode. Displacement is 49 * relative to the address of the opcode that immediately follows 50 * the jump code; thus, 0 implies no jump at all. 51 */ 52 internal virtual void ResolveJump(int disp) 53 { 54 throw new Exception("Not a jump opcode"); 55 } 56 57 /* 58 * Get the Word that this opcode references; this can happen 59 * only with "call" and "const" opcodes. For all other opcodes, 60 * this method returns null. 61 */ 62 internal virtual Word GetReference(T0Comp ctx) 63 { 64 return null; 65 } 66 67 /* 68 * Get the data block that this opcode references; this can happen 69 * only with "const" opcodes. For all other opcodes, this method 70 * returns null. 71 */ 72 internal virtual ConstData GetDataBlock(T0Comp ctx) 73 { 74 return null; 75 } 76 77 /* 78 * Test whether this opcode may "fall through", i.e. execution 79 * may at least potentially proceed to the next opcode. 80 */ 81 internal virtual bool MayFallThrough { 82 get { 83 return true; 84 } 85 } 86 87 /* 88 * Get jump displacement. For non-jump opcodes, this returns 0. 89 */ 90 internal virtual int JumpDisp { 91 get { 92 return 0; 93 } 94 } 95 96 /* 97 * Get stack effect for this opcode (number of elements added to 98 * the stack, could be negative). For OpcodeCall, this returns 99 * 0. 100 */ 101 internal virtual int StackAction { 102 get { 103 return 0; 104 } 105 } 106 107 internal abstract CodeElement ToCodeElement(); 108 109 /* 110 * This method is called for the CodeElement corresponding to 111 * this opcode, at gcode[off]; it is used to compute actual 112 * byte jump offsets when converting code to C. 113 */ 114 internal virtual void FixUp(CodeElement[] gcode, int off) 115 { 116 } 117 } 118