feat(core/asm): add macro expansion
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dualfroz committed
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42f330110b
commit
2004647201
1 file changed
+225
@@ -0,0 +1,225 @@
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using System;
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using System.Collections.Generic;
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namespace Chip8.Core.Assembly;
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public sealed class MacroExpander
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{
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const int expansionDepthLimit = 256;
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sealed class MacroDefinition
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{
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public string name = "";
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public List<string> parameters = new();
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public List<List<Token>> body = new();
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public SourcePosition position;
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}
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readonly Dictionary<string, MacroDefinition> macros = new(StringComparer.OrdinalIgnoreCase);
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public List<Token> expand(List<Token> tokens)
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{
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List<List<Token>> lines = splitLines(tokens);
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List<List<Token>> withoutDefinitions = collectDefinitions(lines);
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var output = new List<List<Token>>();
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emitLines(withoutDefinitions, output, 0);
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return joinLines(output);
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}
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List<List<Token>> collectDefinitions(List<List<Token>> lines)
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{
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var remaining = new List<List<Token>>();
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int index = 0;
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while (index < lines.Count)
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{
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List<Token> line = lines[index];
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if (line.Count > 0 && line[0].isIdentifier("MACRO"))
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{
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index = readDefinition(lines, index);
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}
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else
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{
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remaining.Add(line);
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index++;
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}
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}
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return remaining;
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}
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int readDefinition(List<List<Token>> lines, int index)
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{
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List<Token> header = lines[index];
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if (header.Count < 2)
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{
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throw new AsmException("MACRO needs a name", header[0].position);
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}
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var definition = new MacroDefinition { name = header[1].text, position = header[0].position };
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for (int p = 2; p < header.Count; p++)
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{
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if (header[p].kind == TokenKind.Comma)
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{
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continue;
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}
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if (header[p].kind != TokenKind.Identifier)
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{
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throw new AsmException("macro parameter must be a name", header[p].position);
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}
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definition.parameters.Add(header[p].text);
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}
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int cursor = index + 1;
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while (cursor < lines.Count)
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{
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List<Token> line = lines[cursor];
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if (line.Count > 0 && (line[0].isIdentifier("ENDM") || line[0].isIdentifier("ENDMACRO")))
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{
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macros[definition.name] = definition;
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return cursor + 1;
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}
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definition.body.Add(line);
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cursor++;
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}
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throw new AsmException("macro '" + definition.name + "' is missing ENDM", definition.position);
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}
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void emitLines(List<List<Token>> lines, List<List<Token>> output, int depth)
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{
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if (depth > expansionDepthLimit)
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{
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throw new AsmException("macro expansion too deep (recursive macro?)", lines.Count > 0 && lines[0].Count > 0 ? lines[0][0].position : new SourcePosition(0, 0));
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}
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foreach (List<Token> original in lines)
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{
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List<Token> line = original;
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if (line.Count >= 2 && line[0].kind == TokenKind.Identifier && line[1].kind == TokenKind.Colon)
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{
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output.Add(new List<Token> { line[0], line[1] });
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line = line.GetRange(2, line.Count - 2);
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}
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if (line.Count > 0 && line[0].kind == TokenKind.Identifier && macros.TryGetValue(line[0].text, out MacroDefinition? definition))
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{
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List<List<Token>> expanded = instantiate(definition, line);
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emitLines(expanded, output, depth + 1);
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}
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else if (line.Count > 0)
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{
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output.Add(line);
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}
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}
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}
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static List<List<Token>> instantiate(MacroDefinition definition, List<Token> call)
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{
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List<List<Token>> arguments = splitArguments(call, 1);
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if (arguments.Count != definition.parameters.Count)
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{
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throw new AsmException(
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"macro '" + definition.name + "' expects " + definition.parameters.Count + " argument(s), got " + arguments.Count,
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call[0].position);
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}
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var binding = new Dictionary<string, List<Token>>(StringComparer.OrdinalIgnoreCase);
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for (int p = 0; p < definition.parameters.Count; p++)
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{
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binding[definition.parameters[p]] = arguments[p];
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}
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var result = new List<List<Token>>();
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foreach (List<Token> bodyLine in definition.body)
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{
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var substituted = new List<Token>();
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foreach (Token token in bodyLine)
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{
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if (token.kind == TokenKind.Identifier && binding.TryGetValue(token.text, out List<Token>? replacement))
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{
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substituted.AddRange(replacement);
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}
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else
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{
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substituted.Add(token);
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}
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}
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result.Add(substituted);
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}
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return result;
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}
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static List<List<Token>> splitArguments(List<Token> line, int start)
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{
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var arguments = new List<List<Token>>();
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var current = new List<Token>();
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int depth = 0;
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for (int index = start; index < line.Count; index++)
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{
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Token token = line[index];
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if (token.kind == TokenKind.LeftParen || token.kind == TokenKind.LeftBracket)
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{
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depth++;
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}
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else if (token.kind == TokenKind.RightParen || token.kind == TokenKind.RightBracket)
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{
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depth--;
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}
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if (token.kind == TokenKind.Comma && depth == 0)
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{
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arguments.Add(current);
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current = new List<Token>();
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continue;
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}
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current.Add(token);
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}
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if (current.Count > 0)
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{
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arguments.Add(current);
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}
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return arguments;
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}
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static List<List<Token>> splitLines(List<Token> tokens)
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{
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var lines = new List<List<Token>>();
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var current = new List<Token>();
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foreach (Token token in tokens)
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{
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if (token.kind == TokenKind.EndOfLine || token.kind == TokenKind.EndOfFile)
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{
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if (current.Count > 0)
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{
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lines.Add(current);
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current = new List<Token>();
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}
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continue;
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}
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current.Add(token);
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}
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return lines;
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}
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static List<Token> joinLines(List<List<Token>> lines)
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{
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var tokens = new List<Token>();
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foreach (List<Token> line in lines)
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{
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tokens.AddRange(line);
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SourcePosition position = line.Count > 0 ? line[line.Count - 1].position : new SourcePosition(0, 0);
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tokens.Add(new Token(TokenKind.EndOfLine, "\\n", 0, position));
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}
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tokens.Add(new Token(TokenKind.EndOfFile, "", 0, new SourcePosition(0, 0)));
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return tokens;
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}
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}
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