pkg/dart2wasm/lib/target.dart

// Copyright (c) 2022, 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 'package:kernel/ast.dart';
import 'package:kernel/class_hierarchy.dart';
import 'package:kernel/clone.dart';
import 'package:kernel/core_types.dart';
import 'package:kernel/reference_from_index.dart';
import 'package:kernel/target/changed_structure_notifier.dart';
import 'package:kernel/target/targets.dart';
import 'package:kernel/transformations/mixin_full_resolution.dart'
    as transformMixins show transformLibraries;

import 'package:dart2wasm/constants_backend.dart';
import 'package:dart2wasm/transformers.dart' as wasmTrans;

class WasmTarget extends Target {
  Class? _growableList;
  Class? _immutableList;
  Class? _immutableMap;
  Class? _unmodifiableSet;
  Class? _compactLinkedCustomHashMap;
  Class? _compactLinkedHashSet;
  Class? _oneByteString;
  Class? _twoByteString;

  @override
  late final ConstantsBackend constantsBackend;

  @override
  String get name => 'wasm';

  @override
  TargetFlags get flags => TargetFlags(enableNullSafety: true);

  @override
  List<String> get extraIndexedLibraries => const <String>[
        "dart:collection",
        "dart:typed_data",
      ];

  void _patchHostEndian(CoreTypes coreTypes) {
    // Fix Endian.host to be a const field equal to Endian.little instead of
    // a final field. Wasm is a little-endian platform.
    // Can't use normal patching process for this because CFE does not
    // support patching fields.
    // See http://dartbug.com/32836 for the background.
    final Field host =
        coreTypes.index.getField('dart:typed_data', 'Endian', 'host');
    final Field little =
        coreTypes.index.getField('dart:typed_data', 'Endian', 'little');
    host.isConst = true;
    host.initializer = new CloneVisitorNotMembers().clone(little.initializer!)
      ..parent = host;
  }

  @override
  void performPreConstantEvaluationTransformations(
      Component component,
      CoreTypes coreTypes,
      List<Library> libraries,
      DiagnosticReporter diagnosticReporter,
      {void Function(String msg)? logger,
      ChangedStructureNotifier? changedStructureNotifier}) {
    constantsBackend = WasmConstantsBackend(coreTypes);
    _patchHostEndian(coreTypes);
  }

  @override
  void performModularTransformationsOnLibraries(
      Component component,
      CoreTypes coreTypes,
      ClassHierarchy hierarchy,
      List<Library> libraries,
      Map<String, String>? environmentDefines,
      DiagnosticReporter diagnosticReporter,
      ReferenceFromIndex? referenceFromIndex,
      {void logger(String msg)?,
      ChangedStructureNotifier? changedStructureNotifier}) {
    transformMixins.transformLibraries(
        this, coreTypes, hierarchy, libraries, referenceFromIndex);
    logger?.call("Transformed mixin applications");

    wasmTrans.transformLibraries(libraries, coreTypes, hierarchy);
  }

  @override
  void performTransformationsOnProcedure(
      CoreTypes coreTypes,
      ClassHierarchy hierarchy,
      Procedure procedure,
      Map<String, String>? environmentDefines,
      {void logger(String msg)?}) {
    wasmTrans.transformProcedure(procedure, coreTypes, hierarchy);
  }

  @override
  Expression instantiateInvocation(CoreTypes coreTypes, Expression receiver,
      String name, Arguments arguments, int offset, bool isSuper) {
    throw "Unsupported: instantiateInvocation";
  }

  Expression instantiateNoSuchMethodError(CoreTypes coreTypes,
      Expression receiver, String name, Arguments arguments, int offset,
      {bool isMethod: false,
      bool isGetter: false,
      bool isSetter: false,
      bool isField: false,
      bool isLocalVariable: false,
      bool isDynamic: false,
      bool isSuper: false,
      bool isStatic: false,
      bool isConstructor: false,
      bool isTopLevel: false}) {
    throw "Unsupported: instantiateNoSuchMethodError";
  }

  @override
  bool get supportsSetLiterals => false;

  @override
  int get enabledLateLowerings => LateLowering.all;

  @override
  int get enabledConstructorTearOffLowerings => ConstructorTearOffLowering.all;

  @override
  bool get supportsExplicitGetterCalls => true;

  @override
  bool get supportsLateLoweringSentinel => false;

  @override
  bool get useStaticFieldLowering => false;

  @override
  bool enableNative(Uri uri) => true;

  @override
  Class concreteListLiteralClass(CoreTypes coreTypes) {
    return _growableList ??=
        coreTypes.index.getClass('dart:core', '_GrowableList');
  }

  @override
  Class concreteConstListLiteralClass(CoreTypes coreTypes) {
    return _immutableList ??=
        coreTypes.index.getClass('dart:core', '_ImmutableList');
  }

  @override
  Class concreteMapLiteralClass(CoreTypes coreTypes) {
    return _compactLinkedCustomHashMap ??= coreTypes.index
        .getClass('dart:collection', '_CompactLinkedCustomHashMap');
  }

  @override
  Class concreteConstMapLiteralClass(CoreTypes coreTypes) {
    return _immutableMap ??=
        coreTypes.index.getClass('dart:collection', '_ImmutableMap');
  }

  @override
  Class concreteSetLiteralClass(CoreTypes coreTypes) {
    return _compactLinkedHashSet ??=
        coreTypes.index.getClass('dart:collection', '_CompactLinkedHashSet');
  }

  @override
  Class concreteConstSetLiteralClass(CoreTypes coreTypes) {
    return _unmodifiableSet ??=
        coreTypes.index.getClass('dart:collection', '_UnmodifiableSet');
  }

  @override
  Class concreteStringLiteralClass(CoreTypes coreTypes, String value) {
    const int maxLatin1 = 0xff;
    for (int i = 0; i < value.length; ++i) {
      if (value.codeUnitAt(i) > maxLatin1) {
        return _twoByteString ??=
            coreTypes.index.getClass('dart:core', '_TwoByteString');
      }
    }
    return _oneByteString ??=
        coreTypes.index.getClass('dart:core', '_OneByteString');
  }

  @override
  bool isSupportedPragma(String pragmaName) => pragmaName.startsWith("wasm:");
}