pkg/wasm_builder/lib/src/ir/instructions.dart

// Copyright (c) 2023, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

import '../../source_map.dart';
import '../serialize/serialize.dart';
import 'ir.dart';

class Instructions implements Serializable {
  /// The locals used by this group of instructions.
  final List<Local> locals;

  /// Names of the locals in `locals`.
  ///
  /// Most of the locals won't have names, so this is a [Map] instead of [List]
  /// like [locals], with local indices as keys and names as values.
  final Map<int, String> localNames;

  /// A sequence of Wasm instructions.
  final List<Instruction> instructions;

  final Map<Instruction, StackTrace>? _stackTraces;

  final List<String> _traceLines;

  /// A string trace.
  late final trace = _traceLines.join();

  /// Mappings for the instructions in [_instructions] to their source code.
  ///
  /// Since we add mappings as we generate instructions, this will be sorted
  /// based on [SourceMapping.instructionOffset].
  final List<SourceMapping>? _sourceMappings;

  /// Create a new instruction sequence.
  Instructions(this.locals, this.localNames, this.instructions,
      this._stackTraces, this._traceLines, this._sourceMappings);

  @override
  void serialize(Serializer s) {
    final sourceMappings = _sourceMappings;
    int sourceMappingIdx = 0;
    for (int instructionIdx = 0;
        instructionIdx < instructions.length;
        instructionIdx += 1) {
      final i = instructions[instructionIdx];
      if (_stackTraces != null) s.debugTrace(_stackTraces[i]!);

      if (sourceMappings != null) {
        // Skip to the mapping that covers the current instruction.
        while (sourceMappingIdx < sourceMappings.length - 1 &&
            sourceMappings[sourceMappingIdx + 1].instructionOffset <=
                instructionIdx) {
          sourceMappingIdx += 1;
        }

        if (sourceMappingIdx < sourceMappings.length) {
          final mapping = sourceMappings[sourceMappingIdx];
          if (mapping.instructionOffset <= instructionIdx) {
            s.sourceMapSerializer.addMapping(s.offset, mapping.sourceInfo);
            sourceMappingIdx += 1;
          }
        }
      }

      i.serialize(s);
    }

    s.sourceMapSerializer.addMapping(s.offset, null);
  }
}