/* * Copyright (c) 2016 Thomas Pornin * * Permission is hereby granted, free of charge, to any person obtaining * a copy of this software and associated documentation files (the * "Software"), to deal in the Software without restriction, including * without limitation the rights to use, copy, modify, merge, publish, * distribute, sublicense, and/or sell copies of the Software, and to * permit persons to whom the Software is furnished to do so, subject to * the following conditions: * * The above copyright notice and this permission notice shall be * included in all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE * SOFTWARE. */ using System; using System.Collections.Generic; abstract class Opcode { internal Opcode() { } /* * Execute this opcode. */ internal abstract void Run(CPU cpu); /* * Resolve the target (word reference) for this opcode. */ internal virtual void ResolveTarget(Word target) { throw new Exception("Not a call opcode"); } /* * Resolve the jump offset for this opcode. Displacement is * relative to the address of the opcode that immediately follows * the jump code; thus, 0 implies no jump at all. */ internal virtual void ResolveJump(int disp) { throw new Exception("Not a jump opcode"); } /* * Get the Word that this opcode references; this can happen * only with "call" and "const" opcodes. For all other opcodes, * this method returns null. */ internal virtual Word GetReference(T0Comp ctx) { return null; } /* * Get the data block that this opcode references; this can happen * only with "const" opcodes. For all other opcodes, this method * returns null. */ internal virtual ConstData GetDataBlock(T0Comp ctx) { return null; } /* * Test whether this opcode may "fall through", i.e. execution * may at least potentially proceed to the next opcode. */ internal virtual bool MayFallThrough { get { return true; } } /* * Get jump displacement. For non-jump opcodes, this returns 0. */ internal virtual int JumpDisp { get { return 0; } } /* * Get stack effect for this opcode (number of elements added to * the stack, could be negative). For OpcodeCall, this returns * 0. */ internal virtual int StackAction { get { return 0; } } internal abstract CodeElement ToCodeElement(); /* * This method is called for the CodeElement corresponding to * this opcode, at gcode[off]; it is used to compute actual * byte jump offsets when converting code to C. */ internal virtual void FixUp(CodeElement[] gcode, int off) { } }