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/*
* Copyright (c) 2016 Thomas Pornin <pornin@bolet.org>
*
* 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)
{
}
}
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