1 files changed, 172 insertions, 0 deletions
diff --git a/T0/Word.cs b/T0/Word.cs
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+++ b/T0/Word.cs
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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;
+
+/*
+ * A "word" is a function with a name. Words can be either native or
+ * interpreted; native words are implemented as some in-compiler special
+ * code.
+ *
+ * Some native words (not all of them) have a C implementation and can
+ * thus be part of the generated C code. Native words with no C
+ * implementation can be used only during compilation; this is typically
+ * the case for words that support the syntax (e.g. 'if').
+ */
+
+abstract class Word {
+
+	/*
+	 * The compiler context for this word.
+	 */
+	internal T0Comp TC {
+		get; private set;
+	}
+
+	/*
+	 * Immediate words are executed immediately when encountered in the
+	 * source code, even while compiling another word.
+	 */
+	internal bool Immediate {
+		get; set;
+	}
+
+	/*
+	 * Each word has a unique name. Names are case-sensitive.
+	 */
+	internal string Name {
+		get; private set;
+	}
+
+	/*
+	 * Words are allocated slot numbers when output code is generated.
+	 */
+	internal int Slot {
+		get; set;
+	}
+
+	/*
+	 * Each word may have a known stack effect.
+	 */
+	internal SType StackEffect {
+		get; set;
+	}
+
+	internal Word(T0Comp owner, string name)
+	{
+		TC = owner;
+		Name = name;
+		StackEffect = SType.UNKNOWN;
+	}
+
+	/*
+	 * Resolving a word means looking up all references to external
+	 * words.
+	 */
+	internal virtual void Resolve()
+	{
+	}
+
+	/*
+	 * Execute this word. If the word is native, then its code is
+	 * run right away; if the word is interpreted, then the entry
+	 * sequence is executed.
+	 */
+	internal virtual void Run(CPU cpu)
+	{
+		throw new Exception(String.Format(
+			"cannot run '{0}' at compile-time", Name));
+	}
+
+	/*
+	 * All words may have an explicit C implementations. To be part
+	 * of the generated C code, a word must either be interpreted,
+	 * or have an explicit C implementation, or both.
+	 */
+	internal string CCode {
+		get; set;
+	}
+
+	/*
+	 * Get all words referenced from this one. This implies
+	 * resolving the word.
+	 */
+	internal virtual List<Word> GetReferences()
+	{
+		return new List<Word>();
+	}
+
+	/*
+	 * Get all data blocks directly referenced from this one. This
+	 * implies resolving the word.
+	 */
+	internal virtual List<ConstData> GetDataBlocks()
+	{
+		return new List<ConstData>();
+	}
+
+	/*
+	 * Produce the code elements for this word.
+	 */
+	internal virtual void GenerateCodeElements(List<CodeElement> dst)
+	{
+		throw new Exception("Word does not yield code elements");
+	}
+
+	/*
+	 * Compute/verify stack effect for this word.
+	 */
+	internal virtual void AnalyseFlow()
+	{
+	}
+
+	/*
+	 * Get maximum data stack usage for this word. This is the number
+	 * of extra slots that this word may need on the data stack. If
+	 * the stack effect is not known, this returns -1.
+	 */
+	internal virtual int MaxDataStack {
+		get {
+			SType se = StackEffect;
+			if (!se.IsKnown) {
+				return -1;
+			}
+			if (se.NoExit) {
+				return 0;
+			} else {
+				return Math.Min(0, se.DataOut - se.DataIn);
+			}
+		}
+	}
+
+	/*
+	 * Get maximum return stack usage for this word.
+	 */
+	internal virtual int MaxReturnStack {
+		get {
+			return 0;
+		}
+	}
+}