pkg/wasm_builder/lib/src/builder/globals.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 '../ir/ir.dart' as ir;
import 'builder.dart';
import 'util.dart';

class GlobalsBuilder with Builder<ir.Globals> {
  final ModuleBuilder _moduleBuilder;
  final _importedGlobals = <ir.ImportedGlobal>[];
  final _globalBuilders = <GlobalBuilder>[];

  GlobalsBuilder(this._moduleBuilder);

  void collectUsedTypes(Set<ir.DefType> usedTypes) {
    for (final global in _globalBuilders) {
      final defType = global.type.type.containedDefType;
      if (defType != null) usedTypes.add(defType);
      global.initializer.collectUsedTypes(usedTypes);
    }
    for (final global in _importedGlobals) {
      final defType = global.type.type.containedDefType;
      if (defType != null) usedTypes.add(defType);
    }
  }

  /// Defines a new global variable in this module.
  GlobalBuilder define(ir.GlobalType type, [String? name]) {
    final global = GlobalBuilder(
      _moduleBuilder,
      ir.FinalizableIndex(),
      type,
      name,
    );
    _globalBuilders.add(global);
    return global;
  }

  /// Imports a global variable into this module.
  ir.ImportedGlobal import(String module, String name, ir.GlobalType type) {
    final global = ir.ImportedGlobal(
      _moduleBuilder.module,
      module,
      name,
      ir.FinalizableIndex(),
      type,
    );
    _importedGlobals.add(global);
    return global;
  }

  @override
  ir.Globals forceBuild() {
    final order = <GlobalBuilder>{};

    void dfs(GlobalBuilder b) {
      final instructions = b.initializer.build();
      for (final i in instructions.instructions) {
        if (i is ir.GlobalGet) {
          final global = i.global;
          if (global is GlobalBuilder && !order.contains(global)) {
            dfs(global);
          }
        }
      }
      order.add(b);
    }

    for (final g in _globalBuilders) {
      dfs(g);
    }

    final built = finalizeImportsAndBuilders<ir.DefinedGlobal>(
      _importedGlobals,
      order,
    );
    return ir.Globals(_importedGlobals, built);
  }
}