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95 lines
3.6 KiB
C#
95 lines
3.6 KiB
C#
/*
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* Copyright 2018 faddenSoft
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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using System;
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using System.Diagnostics;
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namespace SourceGen {
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/// <summary>
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/// Weak reference to a symbol for use in an operand or data statement. The reference
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/// is by name; if the symbol disappears or changes value, the reference can be ignored.
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/// This also specifies which part of the numeric value is of interest, so we can reference
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/// the high or low byte of a 16-bit value in (say) LDA #imm.
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///
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/// Instances are immutable.
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/// </summary>
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public class WeakSymbolRef {
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/// <summary>
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/// This identifies the part of the value that we're interested in. All values are
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/// signed 32-bit integers.
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/// </summary>
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public enum Part {
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// This indicates which byte we start with, useful for immediate operands
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// and things like PEA. By popular convention, these are referred to as
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// low, high, and bank.
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//
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// With 16-bit registers, Merlin 32 grabs the high *word*, while cc65's assembler
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// grabs the high *byte*. One is a shift, the other is a byte select. We use
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// low/high/bank just to mean position here.
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//
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// (Could make this orthogonal with a pair of bit fields, one for position and
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// one for width, but there's really only three widths of interest (1, 2, 3 bytes)
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// and that's defined by context.)
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Unknown = 0,
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Low, // LDA #label, LDA #<label
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High, // LDA #>label
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Bank, // LDA #^label
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}
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/// <summary>
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/// Label of symbol of interest.
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/// </summary>
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public string Label { get; private set; }
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/// <summary>
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/// Which part of the value we're referencing.
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/// </summary>
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public Part ValuePart { get; private set; }
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/// <summary>
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/// Full constructor.
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/// </summary>
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public WeakSymbolRef(string label, Part part) {
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Debug.Assert(label != null);
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Label = label;
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ValuePart = part;
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}
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public static bool operator ==(WeakSymbolRef a, WeakSymbolRef b) {
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if (ReferenceEquals(a, b)) {
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return true; // same object, or both null
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}
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if (ReferenceEquals(a, null) || ReferenceEquals(b, null)) {
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return false; // one is null
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}
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return Asm65.Label.LABEL_COMPARER.Equals(a.Label, b.Label) &&
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a.ValuePart == b.ValuePart;
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}
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public static bool operator !=(WeakSymbolRef a, WeakSymbolRef b) {
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return !(a == b);
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}
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public override bool Equals(object obj) {
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return obj is WeakSymbolRef && this == (WeakSymbolRef)obj;
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}
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public override int GetHashCode() {
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return Asm65.Label.ToNormal(Label).GetHashCode() ^ (int)ValuePart;
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}
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public override string ToString() {
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return "WeakSym: " + Label + ":" + ValuePart;
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}
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}
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}
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