pkg/compiler/lib/src/ssa/builder_kernel.dart

// Copyright (c) 2016, 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' as ir;

import '../closure.dart';
import '../common.dart';
import '../common/codegen.dart' show CodegenRegistry;
import '../common/names.dart';
import '../common_elements.dart';
import '../compiler.dart';
import '../constants/values.dart'
    show
        ConstantValue,
        InterceptorConstantValue,
        StringConstantValue,
        TypeConstantValue;
import '../dump_info.dart';
import '../elements/entities.dart';
import '../elements/jumps.dart';
import '../elements/names.dart';
import '../elements/types.dart';
import '../io/source_information.dart';
import '../js/js.dart' as js;
import '../js_backend/allocator_analysis.dart' show JAllocatorAnalysis;
import '../js_backend/backend.dart' show JavaScriptBackend;
import '../js_backend/runtime_types.dart' show RuntimeTypesSubstitutions;
import '../js_emitter/js_emitter.dart' show NativeEmitter;
import '../js_model/locals.dart'
    show forEachOrderedParameter, GlobalLocalsMap, JumpVisitor;
import '../js_model/elements.dart' show JGeneratorBody;
import '../kernel/element_map.dart';
import '../kernel/kernel_backend_strategy.dart';
import '../native/native.dart' as native;
import '../types/abstract_value_domain.dart';
import '../types/types.dart';
import '../universe/call_structure.dart';
import '../universe/feature.dart';
import '../universe/selector.dart';
import '../universe/side_effects.dart' show SideEffects;
import '../universe/target_checks.dart' show TargetChecks;
import '../universe/use.dart'
    show ConstantUse, ConstrainedDynamicUse, StaticUse;
import '../universe/world_builder.dart' show CodegenWorldBuilder;
import '../world.dart';
import 'graph_builder.dart';
import 'jump_handler.dart';
import 'kernel_string_builder.dart';
import 'locals_handler.dart';
import 'loop_handler.dart';
import 'nodes.dart';
import 'ssa.dart';
import 'ssa_branch_builder.dart';
import 'switch_continue_analysis.dart';
import 'type_builder.dart';

// TODO(johnniwinther): Merge this with [KernelInliningState].
class StackFrame {
  final StackFrame parent;
  final MemberEntity member;
  final AsyncMarker asyncMarker;
  final KernelToLocalsMap localsMap;
  final KernelToTypeInferenceMap typeInferenceMap;
  final SourceInformationBuilder<ir.Node> sourceInformationBuilder;

  StackFrame(this.parent, this.member, this.asyncMarker, this.localsMap,
      this.typeInferenceMap, this.sourceInformationBuilder);
}

class KernelSsaGraphBuilder extends ir.Visitor
    with GraphBuilder, SsaBuilderFieldMixin {
  final MemberEntity targetElement;
  final MemberEntity initialTargetElement;

  final JClosedWorld closedWorld;
  final CodegenWorldBuilder _worldBuilder;
  final CodegenRegistry registry;
  final ClosureDataLookup closureDataLookup;
  JAllocatorAnalysis _allocatorAnalysis;

  /// A stack of [InterfaceType]s that have been seen during inlining of
  /// factory constructors.  These types are preserved in [HInvokeStatic]s and
  /// [HCreate]s inside the inline code and registered during code generation
  /// for these nodes.
  // TODO(karlklose): consider removing this and keeping the (substituted) types
  // of the type variables in an environment (like the [LocalsHandler]).
  final List<InterfaceType> currentImplicitInstantiations = <InterfaceType>[];

  /// Used to report information about inlining (which occurs while building the
  /// SSA graph), when dump-info is enabled.
  final InfoReporter _infoReporter;

  HInstruction rethrowableException;

  final Compiler compiler;

  @override
  JavaScriptBackend get backend => compiler.backend;

  final SourceInformationStrategy<ir.Node> _sourceInformationStrategy;
  final KernelToElementMapForBuilding _elementMap;
  final GlobalTypeInferenceResults _globalInferenceResults;
  final GlobalLocalsMap _globalLocalsMap;
  LoopHandler<ir.Node> loopHandler;
  TypeBuilder typeBuilder;

  final NativeEmitter nativeEmitter;

  // [ir.Let] and [ir.LocalInitializer] bindings.
  final Map<ir.VariableDeclaration, HInstruction> letBindings =
      <ir.VariableDeclaration, HInstruction>{};

  /// True if we are visiting the expression of a throw statement; we assume
  /// this is a slow path.
  bool _inExpressionOfThrow = false;

  final List<KernelInliningState> _inliningStack = <KernelInliningState>[];
  Local _returnLocal;
  DartType _returnType;
  bool _inLazyInitializerExpression = false;

  StackFrame _currentFrame;

  KernelSsaGraphBuilder(
      this.initialTargetElement,
      InterfaceType instanceType,
      this.compiler,
      this._elementMap,
      this._globalInferenceResults,
      this._globalLocalsMap,
      this.closedWorld,
      this._worldBuilder,
      this.registry,
      this.closureDataLookup,
      this.nativeEmitter,
      this._sourceInformationStrategy)
      : this.targetElement = _effectiveTargetElementFor(initialTargetElement),
        _infoReporter = compiler.dumpInfoTask,
        _allocatorAnalysis = closedWorld.allocatorAnalysis {
    _enterFrame(targetElement);
    this.loopHandler = new KernelLoopHandler(this);
    typeBuilder = new KernelTypeBuilder(this, _elementMap, _globalLocalsMap);
    graph.element = targetElement;
    graph.sourceInformation =
        _sourceInformationBuilder.buildVariableDeclaration();
    this.localsHandler = new LocalsHandler(this, targetElement, targetElement,
        instanceType, nativeData, interceptorData);
  }

  KernelToLocalsMap get localsMap => _currentFrame.localsMap;

  CommonElements get _commonElements => _elementMap.commonElements;

  KernelToTypeInferenceMap get _typeInferenceMap =>
      _currentFrame.typeInferenceMap;

  SourceInformationBuilder get _sourceInformationBuilder =>
      _currentFrame.sourceInformationBuilder;

  static MemberEntity _effectiveTargetElementFor(MemberEntity member) {
    if (member is JGeneratorBody) return member.function;
    return member;
  }

  void _enterFrame(MemberEntity member) {
    AsyncMarker asyncMarker = AsyncMarker.SYNC;
    ir.FunctionNode function = getFunctionNode(_elementMap, member);
    if (function != null) {
      asyncMarker = getAsyncMarker(function);
    }
    _currentFrame = new StackFrame(
        _currentFrame,
        member,
        asyncMarker,
        _globalLocalsMap.getLocalsMap(member),
        new KernelToTypeInferenceMapImpl(member, _globalInferenceResults),
        _currentFrame != null
            ? _currentFrame.sourceInformationBuilder.forContext(member)
            : _sourceInformationStrategy.createBuilderForContext(member));
  }

  void _leaveFrame() {
    _currentFrame = _currentFrame.parent;
  }

  HGraph build() {
    return reporter.withCurrentElement(localsMap.currentMember, () {
      // TODO(het): no reason to do this here...
      HInstruction.idCounter = 0;
      MemberDefinition definition =
          _elementMap.getMemberDefinition(initialTargetElement);

      switch (definition.kind) {
        case MemberKind.regular:
        case MemberKind.closureCall:
          ir.Node target = definition.node;
          if (target is ir.Procedure) {
            if (target.isExternal) {
              buildExternalFunctionNode(
                  targetElement, _ensureDefaultArgumentValues(target.function));
            } else {
              buildFunctionNode(
                  targetElement, _ensureDefaultArgumentValues(target.function));
            }
          } else if (target is ir.Field) {
            if (handleConstantField(targetElement, registry, closedWorld)) {
              // No code is generated for `targetElement`: All references inline
              // the constant value.
              return null;
            } else if (targetElement.isStatic || targetElement.isTopLevel) {
              backend.constants.registerLazyStatic(targetElement);
            }
            buildField(target);
          } else if (target is ir.FunctionExpression) {
            buildFunctionNode(
                targetElement, _ensureDefaultArgumentValues(target.function));
          } else if (target is ir.FunctionDeclaration) {
            buildFunctionNode(
                targetElement, _ensureDefaultArgumentValues(target.function));
          } else {
            throw 'No case implemented to handle target: '
                '$target for $targetElement';
          }
          break;
        case MemberKind.constructor:
          ir.Constructor constructor = definition.node;
          _ensureDefaultArgumentValues(constructor.function);
          buildConstructor(targetElement, constructor);
          break;
        case MemberKind.constructorBody:
          ir.Constructor constructor = definition.node;
          _ensureDefaultArgumentValues(constructor.function);
          buildConstructorBody(constructor);
          break;
        case MemberKind.closureField:
          failedAt(targetElement, "Unexpected closure field: $targetElement");
          break;
        case MemberKind.signature:
          ir.Node target = definition.node;
          ir.FunctionNode originalClosureNode;
          if (target is ir.Procedure) {
            originalClosureNode = target.function;
          } else if (target is ir.FunctionExpression) {
            originalClosureNode = target.function;
          } else if (target is ir.FunctionDeclaration) {
            originalClosureNode = target.function;
          } else {
            failedAt(
                targetElement,
                "Unexpected function signature: "
                "$targetElement inside a non-closure: $target");
          }
          buildMethodSignature(originalClosureNode);
          break;
        case MemberKind.generatorBody:
          buildGeneratorBody(
              initialTargetElement, _functionNodeOf(definition.node));
          break;
      }
      assert(graph.isValid());

      if (backend.tracer.isEnabled) {
        MemberEntity member = definition.member;
        String name = member.name;
        if (member.isInstanceMember ||
            member.isConstructor ||
            member.isStatic) {
          name = "${member.enclosingClass.name}.$name";
          if (definition.kind == MemberKind.constructorBody) {
            name += " (body)";
          }
        }
        backend.tracer.traceCompilation(name);
        backend.tracer.traceGraph('builder', graph);
      }

      return graph;
    });
  }

  ir.FunctionNode _functionNodeOf(ir.TreeNode node) {
    if (node is ir.Member) return node.function;
    if (node is ir.FunctionDeclaration) return node.function;
    if (node is ir.FunctionExpression) return node.function;
    return null;
  }

  ir.FunctionNode _ensureDefaultArgumentValues(ir.FunctionNode function) {
    // Register all [function]'s default argument values.
    //
    // Default values might be (or contain) functions that are not referenced
    // from anywhere else so we need to ensure these are enqueued.  Stubs and
    // `Function.apply` data are created after the codegen queue is closed, so
    // we force these functions into the queue by registering the constants as
    // used in advance. See language/cyclic_default_values_test.dart for an
    // example.
    //
    // TODO(sra): We could be more precise if stubs and `Function.apply` data
    // were generated by the codegen enqueuer. In practice even in huge programs
    // there are only very small number of constants created here that are not
    // actually used.
    void registerDefaultValue(ir.VariableDeclaration node) {
      ConstantValue constantValue =
          _elementMap.getConstantValue(node.initializer, implicitNull: true);
      assert(
          constantValue != null,
          failedAt(_elementMap.getMethod(function.parent),
              'No constant computed for $node'));
      registry?.registerConstantUse(new ConstantUse.init(constantValue));
    }

    function.positionalParameters
        .skip(function.requiredParameterCount)
        .forEach(registerDefaultValue);
    function.namedParameters.forEach(registerDefaultValue);
    return function;
  }

  @override
  ConstantValue getFieldInitialConstantValue(FieldEntity field) {
    assert(field == targetElement);
    return _elementMap.getFieldConstantValue(field);
  }

  void buildField(ir.Field node) {
    _inLazyInitializerExpression = node.isStatic;
    FieldEntity field = _elementMap.getMember(node);
    openFunction(field, checks: TargetChecks.none);
    if (node.isInstanceMember && options.enableTypeAssertions) {
      HInstruction thisInstruction = localsHandler.readThis(
          sourceInformation: _sourceInformationBuilder.buildGet(node));
      // Use dynamic type because the type computed by the inferrer is
      // narrowed to the type annotation.
      HInstruction parameter =
          new HParameterValue(field, abstractValueDomain.dynamicType);
      // Add the parameter as the last instruction of the entry block.
      // If the method is intercepted, we want the actual receiver
      // to be the first parameter.
      graph.entry.addBefore(graph.entry.last, parameter);
      HInstruction value = typeBuilder.potentiallyCheckOrTrustTypeOfParameter(
          parameter, _getDartTypeIfValid(node.type));
      add(new HFieldSet(abstractValueDomain, field, thisInstruction, value));
    } else {
      if (node.initializer != null) {
        node.initializer.accept(this);
        HInstruction fieldValue = pop();
        HInstruction checkInstruction =
            typeBuilder.potentiallyCheckOrTrustTypeOfAssignment(
                fieldValue, _getDartTypeIfValid(node.type));
        stack.add(checkInstruction);
      } else {
        stack.add(graph.addConstantNull(closedWorld));
      }
      HInstruction value = pop();
      closeAndGotoExit(new HReturn(abstractValueDomain, value,
          _sourceInformationBuilder.buildReturn(node)));
    }
    closeFunction();
  }

  DartType _getDartTypeIfValid(ir.DartType type) {
    if (type is ir.InvalidType) return null;
    return _elementMap.getDartType(type);
  }

  /// Pops the most recent instruction from the stack and 'boolifies' it.
  ///
  /// Boolification is checking if the value is '=== true'.
  @override
  HInstruction popBoolified() {
    HInstruction value = pop();
    if (typeBuilder.checkOrTrustTypes) {
      InterfaceType type = commonElements.boolType;
      return typeBuilder.potentiallyCheckOrTrustTypeOfAssignment(value, type,
          kind: HTypeConversion.BOOLEAN_CONVERSION_CHECK);
    }
    HInstruction result = new HBoolify(value, abstractValueDomain.boolType);
    add(result);
    return result;
  }

  /// Extend current method parameters with parameters for the class type
  /// parameters.  If the class has type parameters but does not need them, bind
  /// to `dynamic` (represented as `null`) so the bindings are available for
  /// building types up the inheritance chain of generative constructors.
  void _addClassTypeVariablesIfNeeded(MemberEntity member) {
    if (!member.isConstructor && member is! ConstructorBodyEntity) {
      return;
    }
    ClassEntity cls = member.enclosingClass;
    InterfaceType thisType = _elementMap.elementEnvironment.getThisType(cls);
    if (thisType.typeArguments.isEmpty) {
      return;
    }
    bool needsTypeArguments = rtiNeed.classNeedsTypeArguments(cls);
    thisType.typeArguments.forEach((DartType _typeVariable) {
      TypeVariableType typeVariableType = _typeVariable;
      HInstruction param;
      if (needsTypeArguments) {
        param = addParameter(
            typeVariableType.element, abstractValueDomain.nonNullType);
      } else {
        // Unused, so bind to `dynamic`.
        param = graph.addConstantNull(closedWorld);
      }
      Local local = localsHandler.getTypeVariableAsLocal(typeVariableType);
      localsHandler.directLocals[local] = param;
    });
  }

  /// Extend current method parameters with parameters for the function type
  /// variables.
  ///
  /// TODO(johnniwinther): Do we need this?
  /// If the method has type variables but does not need them, bind to `dynamic`
  /// (represented as `null`).
  void _addFunctionTypeVariablesIfNeeded(MemberEntity member) {
    if (member is! FunctionEntity) return;

    List<TypeVariableType> typeVariables =
        _elementMap.elementEnvironment.getFunctionTypeVariables(member);
    if (typeVariables.isEmpty) {
      return;
    }
    bool needsTypeArguments = rtiNeed.methodNeedsTypeArguments(member);
    typeVariables.forEach((TypeVariableType typeVariableType) {
      HInstruction param;
      if (needsTypeArguments) {
        param = addParameter(
            typeVariableType.element, abstractValueDomain.nonNullType);
      } else {
        // Unused, so bind to `dynamic`.
        param = graph.addConstantNull(closedWorld);
      }
      Local local = localsHandler.getTypeVariableAsLocal(typeVariableType);
      localsHandler.directLocals[local] = param;
      functionTypeParameterLocals.add(local);
    });
  }

  List<Local> functionTypeParameterLocals = <Local>[];

  /// Builds a generative constructor.
  ///
  /// Generative constructors are built in stages, in effect inlining the
  /// initializers and constructor bodies up the inheritance chain.
  ///
  ///  1. Extend method parameters with parameters the class's type parameters.
  ///
  ///  2. Add type checks for value parameters (might need result of (1)).
  ///
  ///  3. Walk inheritance chain to build bindings for type parameters of
  ///     superclasses and mixed-in classes.
  ///
  ///  4. Collect initializer values. Walk up inheritance chain to collect field
  ///     initializers from field declarations, initializing parameters and
  ///     initializer.
  ///
  ///  5. Create reified type information for instance.
  ///
  ///  6. Allocate instance and assign initializers and reified type information
  ///     to fields by calling JavaScript constructor.
  ///
  ///  7. Walk inheritance chain to call or inline constructor bodies.
  ///
  /// All the bindings are put in the constructor's locals handler. The
  /// implication is that a class cannot be extended or mixed-in twice. If we in
  /// future support repeated uses of a mixin class, we should do so by cloning
  /// the mixin class in the Kernel input.
  void buildConstructor(ConstructorEntity constructor, ir.Constructor node) {
    SourceInformation sourceInformation =
        _sourceInformationBuilder.buildCreate(node);
    ClassEntity cls = constructor.enclosingClass;

    if (_inliningStack.isEmpty) {
      openFunction(constructor,
          functionNode: node.function, checks: TargetChecks.none);
    }

    // [fieldValues] accumulates the field initializer values, which may be
    // overwritten by initializer-list initializers.
    ConstructorData constructorData = new ConstructorData();
    _buildInitializers(node, constructorData);

    List<HInstruction> constructorArguments = <HInstruction>[];
    // Doing this instead of fieldValues.forEach because we haven't defined the
    // order of the arguments here. We can define that with JElements.
    bool isCustomElement = nativeData.isNativeOrExtendsNative(cls) &&
        !nativeData.isJsInteropClass(cls);
    InterfaceType thisType = _elementMap.elementEnvironment.getThisType(cls);
    List<FieldEntity> fields = <FieldEntity>[];
    _worldBuilder.forEachInstanceField(cls,
        (ClassEntity enclosingClass, FieldEntity member) {
      HInstruction value = constructorData.fieldValues[member];
      if (value == null) {
        assert(
            _allocatorAnalysis.isInitializedInAllocator(member) ||
                isCustomElement ||
                reporter.hasReportedError,
            'No initializer value for field ${member}');
      } else {
        fields.add(member);
        DartType type = _elementMap.elementEnvironment.getFieldType(member);
        type = localsHandler.substInContext(type);
        constructorArguments.add(
            typeBuilder.potentiallyCheckOrTrustTypeOfAssignment(value, type));
      }
    });

    addImplicitInstantiation(thisType);
    List<DartType> instantiatedTypes =
        new List<InterfaceType>.from(currentImplicitInstantiations);

    HInstruction newObject;
    if (isCustomElement) {
      // Bulk assign to the initialized fields.
      newObject = graph.explicitReceiverParameter;
      // Null guard ensures an error if we are being called from an explicit
      // 'new' of the constructor instead of via an upgrade. It is optimized out
      // if there are field initializers.
      add(new HFieldGet(null, newObject, abstractValueDomain.dynamicType,
          isAssignable: false));
      for (int i = 0; i < fields.length; i++) {
        add(new HFieldSet(abstractValueDomain, fields[i], newObject,
            constructorArguments[i]));
      }
    } else {
      // Create the runtime type information, if needed.
      bool needsTypeArguments =
          closedWorld.rtiNeed.classNeedsTypeArguments(cls);
      if (needsTypeArguments) {
        // Read the values of the type arguments and create a
        // HTypeInfoExpression to set on the newly created object.
        List<HInstruction> typeArguments = <HInstruction>[];
        InterfaceType thisType =
            _elementMap.elementEnvironment.getThisType(cls);
        for (DartType typeVariable in thisType.typeArguments) {
          HInstruction argument = localsHandler
              .readLocal(localsHandler.getTypeVariableAsLocal(typeVariable));
          typeArguments.add(argument);
        }

        HInstruction typeInfo = new HTypeInfoExpression(
            TypeInfoExpressionKind.INSTANCE,
            thisType,
            typeArguments,
            abstractValueDomain.dynamicType);
        add(typeInfo);
        constructorArguments.add(typeInfo);
      }

      newObject = new HCreate(cls, constructorArguments,
          abstractValueDomain.createNonNullExact(cls), sourceInformation,
          instantiatedTypes: instantiatedTypes,
          hasRtiInput: needsTypeArguments);

      add(newObject);
    }
    removeImplicitInstantiation(thisType);

    HInstruction interceptor;
    // Generate calls to the constructor bodies.
    for (ir.Constructor body in constructorData.constructorChain.reversed) {
      if (_isEmptyStatement(body.function.body)) continue;

      List<HInstruction> bodyCallInputs = <HInstruction>[];
      if (isCustomElement) {
        if (interceptor == null) {
          ConstantValue constant = new InterceptorConstantValue(cls);
          interceptor = graph.addConstant(constant, closedWorld);
        }
        bodyCallInputs.add(interceptor);
      }
      bodyCallInputs.add(newObject);

      // Pass uncaptured arguments first, captured arguments in a box, then type
      // arguments.

      ConstructorEntity inlinedConstructor = _elementMap.getConstructor(body);

      inlinedFrom(inlinedConstructor, () {
        void handleParameter(ir.VariableDeclaration node) {
          Local parameter = localsMap.getLocalVariable(node);
          // If [parameter] is boxed, it will be a field in the box passed as
          // the last parameter. So no need to directly pass it.
          if (!localsHandler.isBoxed(parameter)) {
            bodyCallInputs.add(localsHandler.readLocal(parameter));
          }
        }

        // Provide the parameters to the generative constructor body.
        body.function.positionalParameters.forEach(handleParameter);
        body.function.namedParameters.toList()
          ..sort(namedOrdering)
          ..forEach(handleParameter);

        // If there are locals that escape (i.e. mutated in closures), we pass the
        // box to the constructor.
        CapturedScope scopeData =
            closureDataLookup.getCapturedScope(inlinedConstructor);
        if (scopeData.requiresContextBox) {
          bodyCallInputs.add(localsHandler.readLocal(scopeData.context));
        }

        // Pass type arguments.
        ClassEntity inlinedConstructorClass = inlinedConstructor.enclosingClass;
        if (closedWorld.rtiNeed
            .classNeedsTypeArguments(inlinedConstructorClass)) {
          InterfaceType thisType = _elementMap.elementEnvironment
              .getThisType(inlinedConstructorClass);
          for (DartType typeVariable in thisType.typeArguments) {
            DartType result = localsHandler.substInContext(typeVariable);
            HInstruction argument =
                typeBuilder.analyzeTypeArgument(result, sourceElement);
            bodyCallInputs.add(argument);
          }
        }

        ConstructorBodyEntity constructorBody =
            _elementMap.getConstructorBody(body);
        if (!isCustomElement && // TODO(13836): Fix inlining.
            _tryInlineMethod(constructorBody, null, null, bodyCallInputs, node,
                sourceInformation)) {
          pop();
        } else {
          _invokeConstructorBody(body, bodyCallInputs,
              _sourceInformationBuilder.buildDeclaration(constructor));
        }
      });
    }

    if (_inliningStack.isEmpty) {
      closeAndGotoExit(
          new HReturn(abstractValueDomain, newObject, sourceInformation));
      closeFunction();
    } else {
      localsHandler.updateLocal(_returnLocal, newObject,
          sourceInformation: sourceInformation);
    }
  }

  static bool _isEmptyStatement(ir.Statement body) {
    if (body is ir.EmptyStatement) return true;
    if (body is ir.Block) return body.statements.every(_isEmptyStatement);
    return false;
  }

  void _invokeConstructorBody(ir.Constructor constructor,
      List<HInstruction> inputs, SourceInformation sourceInformation) {
    MemberEntity constructorBody = _elementMap.getConstructorBody(constructor);
    HInvokeConstructorBody invoke = new HInvokeConstructorBody(constructorBody,
        inputs, abstractValueDomain.nonNullType, sourceInformation);
    add(invoke);
  }

  /// Sets context for generating code that is the result of inlining
  /// [inlinedTarget].
  inlinedFrom(MemberEntity inlinedTarget, f()) {
    reporter.withCurrentElement(inlinedTarget, () {
      _enterFrame(inlinedTarget);
      var result = f();
      _leaveFrame();
      return result;
    });
  }

  void _ensureTypeVariablesForInitializers(
      ConstructorData constructorData, ClassEntity enclosingClass) {
    if (!constructorData.includedClasses.add(enclosingClass)) return;
    if (rtiNeed.classNeedsTypeArguments(enclosingClass)) {
      // If [enclosingClass] needs RTI, we have to give a value to its type
      // parameters. For a super constructor call, the type is the supertype
      // of current class. For a redirecting constructor, the type is the
      // current type. [LocalsHandler.substInContext] takes care of both.
      InterfaceType thisType =
          _elementMap.elementEnvironment.getThisType(enclosingClass);
      InterfaceType type = localsHandler.substInContext(thisType);
      List<DartType> arguments = type.typeArguments;
      List<DartType> typeVariables = thisType.typeArguments;
      assert(arguments.length == typeVariables.length);
      Iterator<DartType> variables = typeVariables.iterator;
      type.typeArguments.forEach((DartType argument) {
        variables.moveNext();
        TypeVariableType typeVariable = variables.current;
        localsHandler.updateLocal(
            localsHandler.getTypeVariableAsLocal(typeVariable),
            typeBuilder.analyzeTypeArgument(argument, sourceElement));
      });
    }
  }

  /// Collects the values for field initializers for the direct fields of
  /// [clazz].
  void _collectFieldValues(ir.Class clazz, ConstructorData constructorData) {
    ClassEntity cls = _elementMap.getClass(clazz);
    _worldBuilder.forEachDirectInstanceField(cls, (FieldEntity field) {
      _ensureTypeVariablesForInitializers(
          constructorData, field.enclosingClass);

      MemberDefinition definition = _elementMap.getMemberDefinition(field);
      ir.Field node;
      switch (definition.kind) {
        case MemberKind.regular:
          node = definition.node;
          break;
        default:
          failedAt(field, "Unexpected member definition $definition.");
      }

      if (node.initializer == null) {
        // Unassigned fields of native classes are not initialized to
        // prevent overwriting pre-initialized native properties.
        if (!nativeData.isNativeOrExtendsNative(cls)) {
          if (!_allocatorAnalysis.isInitializedInAllocator(field)) {
            constructorData.fieldValues[field] =
                graph.addConstantNull(closedWorld);
          }
        }
      } else if (node.initializer is! ir.NullLiteral ||
          !nativeData.isNativeClass(cls)) {
        // Compile the initializer in the context of the field so we know that
        // class type parameters are accessed as values.
        // TODO(sra): It would be sufficient to know the context was a field
        // initializer.
        if (!_allocatorAnalysis.isInitializedInAllocator(field)) {
          inlinedFrom(field, () {
            node.initializer.accept(this);
            constructorData.fieldValues[field] = pop();
          });
        }
      }
    });
  }

  static bool isRedirectingConstructor(ir.Constructor constructor) =>
      constructor.initializers
          .any((initializer) => initializer is ir.RedirectingInitializer);

  /// Collects field initializers all the way up the inheritance chain.
  void _buildInitializers(
      ir.Constructor constructor, ConstructorData constructorData) {
    assert(
        _elementMap.getConstructor(constructor) == localsMap.currentMember,
        failedAt(
            localsMap.currentMember,
            'Expected ${localsMap.currentMember} '
            'but found ${_elementMap.getConstructor(constructor)}.'));
    constructorData.constructorChain.add(constructor);

    if (!isRedirectingConstructor(constructor)) {
      // Compute values for field initializers, but only if this is not a
      // redirecting constructor, since the target will compute the fields.
      _collectFieldValues(constructor.enclosingClass, constructorData);
    }
    var foundSuperOrRedirectCall = false;
    for (var initializer in constructor.initializers) {
      if (initializer is ir.FieldInitializer) {
        // TODO(sra): Skip fields initialized in allocator.
        initializer.value.accept(this);
        constructorData.fieldValues[_elementMap.getField(initializer.field)] =
            pop();
      } else if (initializer is ir.SuperInitializer) {
        assert(!foundSuperOrRedirectCall);
        foundSuperOrRedirectCall = true;
        _inlineSuperInitializer(initializer, constructorData, constructor);
      } else if (initializer is ir.RedirectingInitializer) {
        assert(!foundSuperOrRedirectCall);
        foundSuperOrRedirectCall = true;
        _inlineRedirectingInitializer(
            initializer, constructorData, constructor);
      } else if (initializer is ir.LocalInitializer) {
        // LocalInitializer is like a let-expression that is in scope for the
        // rest of the initializers.
        ir.VariableDeclaration variable = initializer.variable;
        assert(variable.isFinal);
        variable.initializer.accept(this);
        HInstruction value = pop();
        // TODO(sra): Apply inferred type information.
        letBindings[variable] = value;
      } else if (initializer is ir.AssertInitializer) {
        // Assert in initializer is currently not supported in dart2js.
        // TODO(johnniwinther): Support assert in initializer.
      } else if (initializer is ir.InvalidInitializer) {
        assert(false, 'ir.InvalidInitializer not handled');
      } else {
        assert(false, 'Unhandled initializer ir.${initializer.runtimeType}');
      }
    }

    if (!foundSuperOrRedirectCall) {
      assert(
          _elementMap.getClass(constructor.enclosingClass) ==
                  _elementMap.commonElements.objectClass ||
              constructor.initializers.any(_ErroneousInitializerVisitor.check),
          'All constructors should have super- or redirecting- initializers,'
          ' except Object()'
          ' ${constructor.initializers}');
    }
  }

  List<HInstruction> _normalizeAndBuildArguments(
      ir.FunctionNode function, ir.Arguments arguments) {
    var builtArguments = <HInstruction>[];
    var positionalIndex = 0;
    function.positionalParameters.forEach((ir.VariableDeclaration node) {
      if (positionalIndex < arguments.positional.length) {
        arguments.positional[positionalIndex++].accept(this);
        builtArguments.add(pop());
      } else {
        ConstantValue constantValue =
            _elementMap.getConstantValue(node.initializer, implicitNull: true);
        assert(
            constantValue != null,
            failedAt(_elementMap.getMethod(function.parent),
                'No constant computed for $node'));
        builtArguments.add(graph.addConstant(constantValue, closedWorld));
      }
    });
    function.namedParameters.toList()
      ..sort(namedOrdering)
      ..forEach((ir.VariableDeclaration node) {
        var correspondingNamed = arguments.named
            .firstWhere((named) => named.name == node.name, orElse: () => null);
        if (correspondingNamed != null) {
          correspondingNamed.value.accept(this);
          builtArguments.add(pop());
        } else {
          ConstantValue constantValue = _elementMap
              .getConstantValue(node.initializer, implicitNull: true);
          assert(
              constantValue != null,
              failedAt(_elementMap.getMethod(function.parent),
                  'No constant computed for $node'));
          builtArguments.add(graph.addConstant(constantValue, closedWorld));
        }
      });

    return builtArguments;
  }

  /// Inlines the given redirecting [constructor]'s initializers by collecting
  /// its field values and building its constructor initializers. We visit super
  /// constructors all the way up to the [Object] constructor.
  void _inlineRedirectingInitializer(ir.RedirectingInitializer initializer,
      ConstructorData constructorData, ir.Constructor caller) {
    var superOrRedirectConstructor = initializer.target;
    var arguments = _normalizeAndBuildArguments(
        superOrRedirectConstructor.function, initializer.arguments);

    // Redirecting initializer already has [localsHandler] bindings for type
    // parameters from the redirecting constructor.

    // For redirecting constructors, the fields will be initialized later by the
    // effective target, so we don't do it here.

    _inlineSuperOrRedirectCommon(initializer, superOrRedirectConstructor,
        arguments, constructorData, caller);
  }

  /// Inlines the given super [constructor]'s initializers by collecting its
  /// field values and building its constructor initializers. We visit super
  /// constructors all the way up to the [Object] constructor.
  void _inlineSuperInitializer(ir.SuperInitializer initializer,
      ConstructorData constructorData, ir.Constructor caller) {
    var target = initializer.target;
    var arguments =
        _normalizeAndBuildArguments(target.function, initializer.arguments);

    ir.Class callerClass = caller.enclosingClass;
    ir.Supertype supertype = callerClass.supertype;

    if (callerClass.mixedInType != null) {
      _collectFieldValues(callerClass.mixedInType.classNode, constructorData);
    }

    // The class of the super-constructor may not be the supertype class. In
    // this case, we must go up the class hierarchy until we reach the class
    // containing the super-constructor.
    while (supertype.classNode != target.enclosingClass) {
      // Fields from unnamed mixin application classes (ie Object&Foo) get
      // "collected" with the regular supertype fields, so we must bind type
      // parameters from both the supertype and the supertype's mixin classes
      // before collecting the field values.
      _collectFieldValues(supertype.classNode, constructorData);
      supertype = supertype.classNode.supertype;
    }
    supertype = supertype.classNode.supertype;

    _inlineSuperOrRedirectCommon(
        initializer, target, arguments, constructorData, caller);
  }

  void _inlineSuperOrRedirectCommon(
      ir.Initializer initializer,
      ir.Constructor constructor,
      List<HInstruction> arguments,
      ConstructorData constructorData,
      ir.Constructor caller) {
    var index = 0;

    ConstructorEntity element = _elementMap.getConstructor(constructor);
    ScopeInfo oldScopeInfo = localsHandler.scopeInfo;

    inlinedFrom(element, () {
      void handleParameter(ir.VariableDeclaration node) {
        Local parameter = localsMap.getLocalVariable(node);
        HInstruction argument = arguments[index++];
        // Because we are inlining the initializer, we must update
        // what was given as parameter. This will be used in case
        // there is a parameter check expression in the initializer.
        parameters[parameter] = argument;
        localsHandler.updateLocal(parameter, argument);
      }

      constructor.function.positionalParameters.forEach(handleParameter);
      constructor.function.namedParameters.toList()
        ..sort(namedOrdering)
        ..forEach(handleParameter);

      _ensureTypeVariablesForInitializers(
          constructorData, element.enclosingClass);

      // Set the locals handler state as if we were inlining the constructor.
      ScopeInfo newScopeInfo = closureDataLookup.getScopeInfo(element);
      localsHandler.scopeInfo = newScopeInfo;
      localsHandler.enterScope(closureDataLookup.getCapturedScope(element),
          _sourceInformationBuilder.buildDeclaration(element));
      _buildInitializers(constructor, constructorData);
    });
    localsHandler.scopeInfo = oldScopeInfo;
  }

  /// Constructs a special signature function for a closure. It is unique in
  /// that no corresponding ir.Node actually exists for it. We just use the
  /// targetElement.
  void buildMethodSignature(ir.FunctionNode originalClosureNode) {
    openFunction(targetElement);
    List<HInstruction> typeArguments = <HInstruction>[];

    // Add function type variables.
    FunctionType functionType =
        _elementMap.getFunctionType(originalClosureNode);
    functionType.forEachTypeVariable((TypeVariableType typeVariableType) {
      if (options.strongMode ||
          typeVariableType.element.typeDeclaration is ClassEntity) {
        DartType result = localsHandler.substInContext(typeVariableType);
        HInstruction argument =
            typeBuilder.analyzeTypeArgument(result, sourceElement);
        typeArguments.add(argument);
      }
    });
    push(new HTypeInfoExpression(
        TypeInfoExpressionKind.COMPLETE,
        _elementMap.getFunctionType(originalClosureNode),
        typeArguments,
        abstractValueDomain.functionType));
    HInstruction value = pop();
    close(new HReturn(abstractValueDomain, value,
            _sourceInformationBuilder.buildReturn(originalClosureNode)))
        .addSuccessor(graph.exit);

    closeFunction();
  }

  /// Builds generative constructor body.
  void buildConstructorBody(ir.Constructor constructor) {
    openFunction(_elementMap.getConstructorBody(constructor),
        functionNode: constructor.function, checks: TargetChecks.none);
    constructor.function.body.accept(this);
    closeFunction();
  }

  /// Builds a SSA graph for FunctionNodes, found in FunctionExpressions and
  /// Procedures.
  void buildFunctionNode(
      FunctionEntity function, ir.FunctionNode functionNode) {
    if (functionNode.asyncMarker != ir.AsyncMarker.Sync) {
      buildGenerator(function, functionNode);
      return;
    }

    // TODO(sra): Static methods with no tear-off can be generated with no
    // checks.
    // TODO(sra): Instance methods can be generated with reduced checks if
    // called only from non-dynamic call-sites.
    openFunction(function, functionNode: functionNode);

    // If [functionNode] is `operator==` we explicitly add a null check at the
    // beginning of the method. This is to avoid having call sites do the null
    // check.
    if (function.name == '==') {
      if (!_commonElements.operatorEqHandlesNullArgument(function)) {
        handleIf(
            visitCondition: () {
              HParameterValue parameter = parameters.values.first;
              push(new HIdentity(parameter, graph.addConstantNull(closedWorld),
                  null, abstractValueDomain.boolType));
            },
            visitThen: () {
              closeAndGotoExit(new HReturn(
                  abstractValueDomain,
                  graph.addConstantBool(false, closedWorld),
                  _sourceInformationBuilder.buildReturn(functionNode)));
            },
            visitElse: null,
            sourceInformation: _sourceInformationBuilder.buildIf(functionNode));
      }
    }
    if (const bool.fromEnvironment('unreachable-throw')) {
      var emptyParameters = parameters.values
          .where((p) => abstractValueDomain.isEmpty(p.instructionType));
      if (emptyParameters.length > 0) {
        addComment('${emptyParameters} inferred as [empty]');
        add(new HInvokeStatic(
            commonElements.assertUnreachableMethod,
            <HInstruction>[],
            abstractValueDomain.dynamicType,
            const <DartType>[]));
        closeFunction();
        return;
      }
    }
    functionNode.body.accept(this);
    closeFunction();
  }

  /// Adds a JavaScript comment to the output. The comment will be omitted in
  /// minified mode.  Each line in [text] is preceded with `//` and indented.
  /// Use sparingly. In order for the comment to be retained it is modeled as
  /// having side effects which will inhibit code motion.
  // TODO(sra): Figure out how to keep comment anchored without effects.
  void addComment(String text) {
    add(new HForeignCode(js.js.statementTemplateYielding(new js.Comment(text)),
        abstractValueDomain.dynamicType, <HInstruction>[],
        isStatement: true));
  }

  /// Builds a SSA graph for a sync*/async/async* generator.  We generate a
  /// entry function which tail-calls a body function. The entry contains
  /// per-invocation checks and the body, which is later transformed, contains
  /// the re-entrant 'state machine' code.
  void buildGenerator(FunctionEntity function, ir.FunctionNode functionNode) {
    openFunction(function, functionNode: functionNode);

    // Prepare to tail-call the body.

    // Is 'buildAsyncBody' the best location for the entry?
    var sourceInformation = _sourceInformationBuilder.buildAsyncBody();

    // Forward all the parameters to the body.
    List<HInstruction> inputs = <HInstruction>[];
    if (graph.thisInstruction != null) {
      inputs.add(graph.thisInstruction);
    }
    if (graph.explicitReceiverParameter != null) {
      inputs.add(graph.explicitReceiverParameter);
    }
    for (Local local in parameters.keys) {
      inputs.add(localsHandler.readLocal(local));
    }
    for (Local local in functionTypeParameterLocals) {
      inputs.add(localsHandler.readLocal(local));
    }

    // Add the type parameter for the generator's element type.
    DartType elementType = _elementMap.elementEnvironment
        .getAsyncOrSyncStarElementType(function.asyncMarker, _returnType);

    if (elementType.containsFreeTypeVariables) {
      // Type must be computed in the entry function, where the type variables
      // are in scope, and passed to the body function.
      inputs.add(typeBuilder.analyzeTypeArgument(elementType, function));
    } else {
      // Types with no type variables can be emitted as part of the generator,
      // avoiding an extra argument.
      if (_generatedEntryIsEmpty()) {
        // If the entry function is empty (e.g. no argument checks) and the type
        // can be generated in body, 'inline' the body by generating it in
        // place. This works because the subsequent transformation of the code
        // is 'correct' for the empty entry function code.
        graph.needsAsyncRewrite = true;
        graph.asyncElementType = elementType;
        functionNode.body.accept(this);
        closeFunction();
        return;
      }
    }

    JGeneratorBody body = _elementMap.getGeneratorBody(function);
    backend.outputUnitData.registerColocatedMembers(function, body);
    push(new HInvokeGeneratorBody(
        body,
        inputs,
        abstractValueDomain.dynamicType, // TODO: better type.
        sourceInformation));

    closeAndGotoExit(
        new HReturn(abstractValueDomain, pop(), sourceInformation));

    closeFunction();
  }

  /// Builds a SSA graph for a sync*/async/async* generator body.
  void buildGeneratorBody(
      JGeneratorBody function, ir.FunctionNode functionNode) {
    FunctionEntity entry = function.function;
    openFunction(entry, functionNode: functionNode, checks: TargetChecks.none);
    graph.needsAsyncRewrite = true;
    if (!function.elementType.containsFreeTypeVariables) {
      // We can generate the element type in place
      graph.asyncElementType = function.elementType;
    }
    functionNode.body.accept(this);
    closeFunction();
  }

  bool _generatedEntryIsEmpty() {
    HBasicBlock block = current;
    // If `block.id` is not 1 then we generated some control flow.
    if (block.id != 1) return false;
    for (HInstruction node = block.first; node != null; node = node.next) {
      if (node is HGoto) continue;
      return false;
    }
    return true;
  }

  void _potentiallyAddFunctionParameterTypeChecks(
      ir.FunctionNode function, TargetChecks targetChecks) {
    // Put the type checks in the first successor of the entry,
    // because that is where the type guards will also be inserted.
    // This way we ensure that a type guard will dominate the type
    // check.

    if (targetChecks.checkTypeParameters) {
      checkTypeVariableBounds(targetElement);
    }

    MemberDefinition definition =
        _elementMap.getMemberDefinition(targetElement);
    bool nodeIsConstructorBody = definition.kind == MemberKind.constructorBody;

    void _handleParameter(ir.VariableDeclaration variable) {
      Local local = localsMap.getLocalVariable(variable);
      if (nodeIsConstructorBody &&
          closureDataLookup.getCapturedScope(targetElement).isBoxed(local)) {
        // If local is boxed, then `variable` will be a field inside the box
        // passed as the last parameter, so no need to update our locals
        // handler or check types at this point.
        return;
      }
      HInstruction newParameter = localsHandler.directLocals[local];
      DartType type = _getDartTypeIfValid(variable.type);

      if (options.strongMode) {
        if (targetChecks.checkAllParameters ||
            (targetChecks.checkCovariantParameters &&
                (variable.isGenericCovariantImpl || variable.isCovariant))) {
          newParameter = typeBuilder.potentiallyCheckOrTrustTypeOfParameter(
              newParameter, type);
        } else {
          newParameter = typeBuilder.trustTypeOfParameter(newParameter, type);
        }
      } else {
        newParameter = typeBuilder.potentiallyCheckOrTrustTypeOfParameter(
            newParameter, type);
      }

      localsHandler.directLocals[local] = newParameter;
    }

    function.positionalParameters.forEach(_handleParameter);
    function.namedParameters.toList()..forEach(_handleParameter);
  }

  void checkTypeVariableBounds(FunctionEntity method) {
    if (rtiNeed.methodNeedsTypeArguments(method) &&
        options.parameterCheckPolicy.isEmitted) {
      ir.FunctionNode function = getFunctionNode(_elementMap, method);
      for (ir.TypeParameter typeParameter in function.typeParameters) {
        Local local = localsMap.getLocalTypeVariable(
            new ir.TypeParameterType(typeParameter), _elementMap);
        HInstruction newParameter = localsHandler.directLocals[local];
        DartType bound = _getDartTypeIfValid(typeParameter.bound);
        if (!bound.isDynamic &&
            !bound.isVoid &&
            bound != _commonElements.objectType) {
          _assertIsType(
              newParameter,
              bound,
              "The type argument '",
              "' is not a subtype of the type variable bound '",
              "' of type variable '${local.name}' in '${method.name}'.");
        }
      }
    }
  }

  /// Builds a SSA graph for FunctionNodes of external methods.
  void buildExternalFunctionNode(
      FunctionEntity function, ir.FunctionNode functionNode) {
    // TODO(johnniwinther): Non-js-interop external functions should
    // throw a runtime error.
    assert(functionNode.body == null);
    openFunction(function, functionNode: functionNode);

    if (closedWorld.nativeData.isNativeMember(targetElement)) {
      nativeEmitter.nativeMethods.add(targetElement);
      String nativeName;
      if (closedWorld.nativeData.hasFixedBackendName(targetElement)) {
        nativeName = closedWorld.nativeData.getFixedBackendName(targetElement);
      } else {
        nativeName = targetElement.name;
      }

      String templateReceiver = '';
      List<String> templateArguments = <String>[];
      List<HInstruction> inputs = <HInstruction>[];
      if (targetElement.isInstanceMember) {
        templateReceiver = '#.';
        inputs.add(localsHandler.readThis(
            sourceInformation:
                _sourceInformationBuilder.buildGet(functionNode)));
      }

      for (ir.VariableDeclaration param in functionNode.positionalParameters) {
        templateArguments.add('#');
        Local local = localsMap.getLocalVariable(param);
        // Convert Dart function to JavaScript function.
        HInstruction argument = localsHandler.readLocal(local);
        ir.DartType type = param.type;
        if (type is ir.FunctionType) {
          int arity = type.positionalParameters.length;
          _pushStaticInvocation(
              _commonElements.closureConverter,
              [argument, graph.addConstantInt(arity, closedWorld)],
              abstractValueDomain.dynamicType,
              const <DartType>[]);
          argument = pop();
        }
        inputs.add(argument);
      }

      String arguments = templateArguments.join(',');

      // TODO(sra): Use declared type or NativeBehavior type.
      AbstractValue typeMask = abstractValueDomain.dynamicType;
      String template;
      if (targetElement.isGetter) {
        template = '${templateReceiver}$nativeName';
      } else if (targetElement.isSetter) {
        template = '${templateReceiver}$nativeName = ${arguments}';
      } else {
        template = '${templateReceiver}$nativeName(${arguments})';
      }

      push(new HForeignCode(
          js.js.uncachedExpressionTemplate(template), typeMask, inputs,
          effects: new SideEffects()));
      // TODO(johnniwinther): Provide source information.
      HInstruction value = pop();
      if (targetElement.isSetter) {
        value = graph.addConstantNull(closedWorld);
      }
      close(new HReturn(abstractValueDomain, value,
              _sourceInformationBuilder.buildReturn(functionNode)))
          .addSuccessor(graph.exit);
    }
    // TODO(sra): Handle JS-interop methods.
    closeFunction();
  }

  void addImplicitInstantiation(DartType type) {
    if (type != null) {
      currentImplicitInstantiations.add(type);
    }
  }

  void removeImplicitInstantiation(DartType type) {
    if (type != null) {
      currentImplicitInstantiations.removeLast();
    }
  }

  void openFunction(MemberEntity member,
      {ir.FunctionNode functionNode, TargetChecks checks}) {
    // TODO(sra): Pass from all sites.
    checks ??= TargetChecks.dynamicChecks;

    Map<Local, AbstractValue> parameterMap = <Local, AbstractValue>{};
    if (functionNode != null) {
      void handleParameter(ir.VariableDeclaration node) {
        Local local = localsMap.getLocalVariable(node);
        parameterMap[local] =
            _typeInferenceMap.getInferredTypeOfParameter(local);
      }

      functionNode.positionalParameters.forEach(handleParameter);
      functionNode.namedParameters.toList()
        ..sort(namedOrdering)
        ..forEach(handleParameter);
      _returnType = _elementMap.getDartType(functionNode.returnType);
    }

    HBasicBlock block = graph.addNewBlock();
    open(graph.entry);

    localsHandler.startFunction(
        targetElement,
        closureDataLookup.getScopeInfo(targetElement),
        closureDataLookup.getCapturedScope(targetElement),
        parameterMap,
        _sourceInformationBuilder.buildDeclaration(targetElement),
        isGenerativeConstructorBody: targetElement is ConstructorBodyEntity);
    close(new HGoto(abstractValueDomain)).addSuccessor(block);

    open(block);

    _addClassTypeVariablesIfNeeded(member);
    _addFunctionTypeVariablesIfNeeded(member);

    if (functionNode != null) {
      _potentiallyAddFunctionParameterTypeChecks(functionNode, checks);
    }
    _insertTraceCall(member);
    _insertCoverageCall(member);
  }

  void closeFunction() {
    if (!isAborted()) closeAndGotoExit(new HGoto(abstractValueDomain));
    graph.finalize(abstractValueDomain);
  }

  @override
  void defaultExpression(ir.Expression expression) {
    // TODO(het): This is only to get tests working.
    _trap('Unhandled ir.${expression.runtimeType}  $expression');
  }

  @override
  void defaultStatement(ir.Statement statement) {
    _trap('Unhandled ir.${statement.runtimeType}  $statement');
    pop();
  }

  void _trap(String message) {
    HInstruction nullValue = graph.addConstantNull(closedWorld);
    HInstruction errorMessage = graph.addConstantString(message, closedWorld);
    HInstruction trap = new HForeignCode(
        js.js.parseForeignJS("#.#"),
        abstractValueDomain.dynamicType,
        <HInstruction>[nullValue, errorMessage]);
    trap.sideEffects
      ..setAllSideEffects()
      ..setDependsOnSomething();
    push(trap);
  }

  /// Returns the current source element. This is used by the type builder.
  ///
  /// The returned element is a declaration element.
  // TODO(efortuna): Update this when we implement inlining.
  // TODO(sra): Re-implement type builder using Kernel types and the
  // `target` for context.
  @override
  MemberEntity get sourceElement => _currentFrame.member;

  @override
  void visitCheckLibraryIsLoaded(ir.CheckLibraryIsLoaded checkLoad) {
    ImportEntity import = _elementMap.getImport(checkLoad.import);
    String loadId = deferredLoadTask.getImportDeferName(
        _elementMap.getSpannable(targetElement, checkLoad), import);
    HInstruction prefixConstant = graph.addConstantString(loadId, closedWorld);
    HInstruction uriConstant =
        graph.addConstantString('${import.uri}', closedWorld);
    _pushStaticInvocation(
        _commonElements.checkDeferredIsLoaded,
        [prefixConstant, uriConstant],
        _typeInferenceMap
            .getReturnTypeOf(_commonElements.checkDeferredIsLoaded),
        const <DartType>[]);
  }

  @override
  void visitLoadLibrary(ir.LoadLibrary loadLibrary) {
    String loadId = deferredLoadTask.getImportDeferName(
        _elementMap.getSpannable(targetElement, loadLibrary),
        _elementMap.getImport(loadLibrary.import));
    // TODO(efortuna): Source information!
    push(new HInvokeStatic(
        commonElements.loadDeferredLibrary,
        [graph.addConstantString(loadId, closedWorld)],
        abstractValueDomain.nonNullType,
        const <DartType>[],
        targetCanThrow: false));
  }

  @override
  void visitBlock(ir.Block block) {
    assert(!isAborted());
    if (!isReachable) return; // This can only happen when inlining.
    for (ir.Statement statement in block.statements) {
      statement.accept(this);
      if (!isReachable) {
        // The block has been aborted by a return or a throw.
        if (stack.isNotEmpty) {
          reporter.internalError(
              NO_LOCATION_SPANNABLE, 'Non-empty instruction stack.');
        }
        return;
      }
    }
    assert(!current.isClosed());
    if (stack.isNotEmpty) {
      reporter.internalError(
          NO_LOCATION_SPANNABLE, 'Non-empty instruction stack');
    }
  }

  @override
  void visitEmptyStatement(ir.EmptyStatement node) {
    // Empty statement adds no instructions to current block.
  }

  @override
  void visitExpressionStatement(ir.ExpressionStatement node) {
    if (!isReachable) return;
    ir.Expression expression = node.expression;
    if (expression is ir.Throw && _inliningStack.isEmpty) {
      _visitThrowExpression(expression.expression);
      handleInTryStatement();
      SourceInformation sourceInformation =
          _sourceInformationBuilder.buildThrow(node.expression);
      closeAndGotoExit(
          new HThrow(abstractValueDomain, pop(), sourceInformation));
    } else {
      expression.accept(this);
      pop();
    }
  }

  /// Returns true if the [type] is a valid return type for an asynchronous
  /// function.
  ///
  /// Asynchronous functions return a `Future`, and a valid return is thus
  /// either dynamic, Object, or Future.
  ///
  /// We do not accept the internal Future implementation class.
  bool isValidAsyncReturnType(DartType type) {
    // TODO(sigurdm): In an internal library a function could be declared:
    //
    // _FutureImpl foo async => 1;
    //
    // This should be valid (because the actual value returned from an async
    // function is a `_FutureImpl`), but currently false is returned in this
    // case.
    return type.isDynamic ||
        type == _commonElements.objectType ||
        (type is InterfaceType && type.element == _commonElements.futureClass);
  }

  @override
  void visitReturnStatement(ir.ReturnStatement node) {
    SourceInformation sourceInformation =
        _sourceInformationBuilder.buildReturn(node);
    HInstruction value;
    if (node.expression == null) {
      value = graph.addConstantNull(closedWorld);
    } else {
      node.expression.accept(this);
      value = pop();
      if (_currentFrame.asyncMarker == AsyncMarker.ASYNC) {
        if (options.enableTypeAssertions &&
            !isValidAsyncReturnType(_returnType)) {
          generateTypeError(
              "Async function returned a Future,"
              " was declared to return a ${_returnType}.",
              sourceInformation);
          pop();
          return;
        }
      } else {
        value = typeBuilder.potentiallyCheckOrTrustTypeOfAssignment(
            value, _returnType);
      }
    }
    handleInTryStatement();
    _emitReturn(value, sourceInformation);
  }

  @override
  void visitForStatement(ir.ForStatement node) {
    assert(isReachable);
    assert(node.body != null);
    void buildInitializer() {
      for (ir.VariableDeclaration declaration in node.variables) {
        declaration.accept(this);
      }
    }

    HInstruction buildCondition() {
      if (node.condition == null) {
        return graph.addConstantBool(true, closedWorld);
      }
      node.condition.accept(this);
      return popBoolified();
    }

    void buildUpdate() {
      for (ir.Expression expression in node.updates) {
        expression.accept(this);
        assert(!isAborted());
        // The result of the update instruction isn't used, and can just
        // be dropped.
        pop();
      }
    }

    void buildBody() {
      node.body.accept(this);
    }

    JumpTarget jumpTarget = localsMap.getJumpTargetForFor(node);
    loopHandler.handleLoop(
        node,
        localsMap.getCapturedLoopScope(closureDataLookup, node),
        jumpTarget,
        buildInitializer,
        buildCondition,
        buildUpdate,
        buildBody,
        _sourceInformationBuilder.buildLoop(node));
  }

  @override
  void visitForInStatement(ir.ForInStatement node) {
    if (node.isAsync) {
      _buildAsyncForIn(node);
    } else if (_typeInferenceMap.isJsIndexableIterator(
        node, abstractValueDomain)) {
      // If the expression being iterated over is a JS indexable type, we can
      // generate an optimized version of for-in that uses indexing.
      _buildForInIndexable(node);
    } else {
      _buildForInIterator(node);
    }
  }

  /// Builds the graph for a for-in node with an indexable expression.
  ///
  /// In this case we build:
  ///
  ///    int end = a.length;
  ///    for (int i = 0;
  ///         i < a.length;
  ///         checkConcurrentModificationError(a.length == end, a), ++i) {
  ///      <declaredIdentifier> = a[i];
  ///      <body>
  ///    }
  _buildForInIndexable(ir.ForInStatement node) {
    SyntheticLocal indexVariable = localsHandler.createLocal('_i');

    // These variables are shared by initializer, condition, body and update.
    HInstruction array; // Set in buildInitializer.
    bool isFixed; // Set in buildInitializer.
    HInstruction originalLength = null; // Set for growable lists.

    HInstruction buildGetLength(SourceInformation sourceInformation) {
      HGetLength result = new HGetLength(
          array, abstractValueDomain.positiveIntType,
          isAssignable: !isFixed)
        ..sourceInformation = sourceInformation;
      add(result);
      return result;
    }

    void buildConcurrentModificationErrorCheck() {
      if (originalLength == null) return;
      // The static call checkConcurrentModificationError() is expanded in
      // codegen to:
      //
      //     array.length == _end || throwConcurrentModificationError(array)
      //
      SourceInformation sourceInformation =
          _sourceInformationBuilder.buildForInMoveNext(node);
      HInstruction length = buildGetLength(sourceInformation);
      push(new HIdentity(
          length, originalLength, null, abstractValueDomain.boolType)
        ..sourceInformation = sourceInformation);
      _pushStaticInvocation(
          _commonElements.checkConcurrentModificationError,
          [pop(), array],
          _typeInferenceMap.getReturnTypeOf(
              _commonElements.checkConcurrentModificationError),
          const <DartType>[],
          sourceInformation: sourceInformation);
      pop();
    }

    void buildInitializer() {
      SourceInformation sourceInformation =
          _sourceInformationBuilder.buildForInIterator(node);

      node.iterable.accept(this);
      array = pop();
      isFixed =
          abstractValueDomain.isFixedLengthJsIndexable(array.instructionType);
      localsHandler.updateLocal(
          indexVariable, graph.addConstantInt(0, closedWorld),
          sourceInformation: sourceInformation);
      originalLength = buildGetLength(sourceInformation);
    }

    HInstruction buildCondition() {
      SourceInformation sourceInformation =
          _sourceInformationBuilder.buildForInMoveNext(node);
      HInstruction index = localsHandler.readLocal(indexVariable,
          sourceInformation: sourceInformation);
      HInstruction length = buildGetLength(sourceInformation);
      HInstruction compare =
          new HLess(index, length, null, abstractValueDomain.boolType)
            ..sourceInformation = sourceInformation;
      add(compare);
      return compare;
    }

    void buildBody() {
      // If we had mechanically inlined ArrayIterator.moveNext(), it would have
      // inserted the ConcurrentModificationError check as part of the
      // condition.  It is not necessary on the first iteration since there is
      // no code between calls to `get iterator` and `moveNext`, so the test is
      // moved to the loop update.

      // Find a type for the element. Use the element type of the indexer of the
      // array, as this is stronger than the iterator's `get current` type, for
      // example, `get current` includes null.
      // TODO(sra): The element type of a container type mask might be better.
      AbstractValue type = _typeInferenceMap.inferredIndexType(node);

      SourceInformation sourceInformation =
          _sourceInformationBuilder.buildForInCurrent(node);
      HInstruction index = localsHandler.readLocal(indexVariable,
          sourceInformation: sourceInformation);
      HInstruction value = new HIndex(array, index, null, type)
        ..sourceInformation = sourceInformation;
      add(value);

      Local loopVariableLocal = localsMap.getLocalVariable(node.variable);
      localsHandler.updateLocal(loopVariableLocal, value,
          sourceInformation: sourceInformation);
      // Hint to name loop value after name of loop variable.
      if (loopVariableLocal is! SyntheticLocal) {
        value.sourceElement ??= loopVariableLocal;
      }

      node.body.accept(this);
    }

    void buildUpdate() {
      // See buildBody as to why we check here.
      buildConcurrentModificationErrorCheck();

      // TODO(sra): It would be slightly shorter to generate `a[i++]` in the
      // body (and that more closely follows what an inlined iterator would do)
      // but the code is horrible as `i+1` is carried around the loop in an
      // additional variable.
      SourceInformation sourceInformation =
          _sourceInformationBuilder.buildForInSet(node);
      HInstruction index = localsHandler.readLocal(indexVariable,
          sourceInformation: sourceInformation);
      HInstruction one = graph.addConstantInt(1, closedWorld);
      HInstruction addInstruction =
          new HAdd(index, one, null, abstractValueDomain.positiveIntType)
            ..sourceInformation = sourceInformation;
      add(addInstruction);
      localsHandler.updateLocal(indexVariable, addInstruction,
          sourceInformation: sourceInformation);
    }

    loopHandler.handleLoop(
        node,
        localsMap.getCapturedLoopScope(closureDataLookup, node),
        localsMap.getJumpTargetForForIn(node),
        buildInitializer,
        buildCondition,
        buildUpdate,
        buildBody,
        _sourceInformationBuilder.buildLoop(node));
  }

  _buildForInIterator(ir.ForInStatement node) {
    // Generate a structure equivalent to:
    //   Iterator<E> $iter = <iterable>.iterator;
    //   while ($iter.moveNext()) {
    //     <variable> = $iter.current;
    //     <body>
    //   }

    // The iterator is shared between initializer, condition and body.
    HInstruction iterator;

    void buildInitializer() {
      AbstractValue mask = _typeInferenceMap.typeOfIterator(node);
      node.iterable.accept(this);
      HInstruction receiver = pop();
      _pushDynamicInvocation(
          node,
          mask,
          Selectors.iterator,
          <HInstruction>[receiver],
          const <DartType>[],
          _sourceInformationBuilder.buildForInIterator(node));
      iterator = pop();
    }

    HInstruction buildCondition() {
      AbstractValue mask = _typeInferenceMap.typeOfIteratorMoveNext(node);
      _pushDynamicInvocation(
          node,
          mask,
          Selectors.moveNext,
          <HInstruction>[iterator],
          const <DartType>[],
          _sourceInformationBuilder.buildForInMoveNext(node));
      return popBoolified();
    }

    void buildBody() {
      SourceInformation sourceInformation =
          _sourceInformationBuilder.buildForInCurrent(node);
      AbstractValue mask = _typeInferenceMap.typeOfIteratorCurrent(node);
      _pushDynamicInvocation(node, mask, Selectors.current, [iterator],
          const <DartType>[], sourceInformation);

      Local loopVariableLocal = localsMap.getLocalVariable(node.variable);
      HInstruction value = typeBuilder.potentiallyCheckOrTrustTypeOfAssignment(
          pop(), _getDartTypeIfValid(node.variable.type));
      localsHandler.updateLocal(loopVariableLocal, value,
          sourceInformation: sourceInformation);
      // Hint to name loop value after name of loop variable.
      if (loopVariableLocal is! SyntheticLocal) {
        value.sourceElement ??= loopVariableLocal;
      }
      node.body.accept(this);
    }

    loopHandler.handleLoop(
        node,
        localsMap.getCapturedLoopScope(closureDataLookup, node),
        localsMap.getJumpTargetForForIn(node),
        buildInitializer,
        buildCondition,
        () {},
        buildBody,
        _sourceInformationBuilder.buildLoop(node));
  }

  void _buildAsyncForIn(ir.ForInStatement node) {
    // The async-for is implemented with a StreamIterator.
    HInstruction streamIterator;

    node.iterable.accept(this);

    List<HInstruction> arguments = [pop()];
    ClassEntity cls = _commonElements.streamIterator;
    DartType typeArg = _elementMap.getDartType(node.variable.type);
    InterfaceType instanceType =
        localsHandler.substInContext(new InterfaceType(cls, [typeArg]));
    addImplicitInstantiation(instanceType);
    SourceInformation sourceInformation =
        _sourceInformationBuilder.buildForInIterator(node);
    // TODO(johnniwinther): Pass type arguments to constructors like calling
    // a generic method.
    if (rtiNeed.classNeedsTypeArguments(cls)) {
      _addTypeArguments(arguments, [typeArg], sourceInformation);
    }
    ConstructorEntity constructor = _commonElements.streamIteratorConstructor;
    _pushStaticInvocation(constructor, arguments,
        _typeInferenceMap.getReturnTypeOf(constructor), const <DartType>[],
        instanceType: instanceType, sourceInformation: sourceInformation);

    streamIterator = pop();

    void buildInitializer() {}

    HInstruction buildCondition() {
      AbstractValue mask = _typeInferenceMap.typeOfIteratorMoveNext(node);
      _pushDynamicInvocation(
          node,
          mask,
          Selectors.moveNext,
          [streamIterator],
          const <DartType>[],
          _sourceInformationBuilder.buildForInMoveNext(node));
      HInstruction future = pop();
      push(new HAwait(future, abstractValueDomain.dynamicType));
      return popBoolified();
    }

    void buildBody() {
      AbstractValue mask = _typeInferenceMap.typeOfIteratorCurrent(node);
      _pushDynamicInvocation(
          node,
          mask,
          Selectors.current,
          [streamIterator],
          const <DartType>[],
          _sourceInformationBuilder.buildForInIterator(node));
      localsHandler.updateLocal(
          localsMap.getLocalVariable(node.variable), pop());
      node.body.accept(this);
    }

    void buildUpdate() {}

    // Creates a synthetic try/finally block in case anything async goes amiss.
    TryCatchFinallyBuilder tryBuilder = new TryCatchFinallyBuilder(
        this, _sourceInformationBuilder.buildLoop(node));
    // Build fake try body:
    loopHandler.handleLoop(
        node,
        localsMap.getCapturedLoopScope(closureDataLookup, node),
        localsMap.getJumpTargetForForIn(node),
        buildInitializer,
        buildCondition,
        buildUpdate,
        buildBody,
        _sourceInformationBuilder.buildLoop(node));

    void finalizerFunction() {
      _pushDynamicInvocation(node, null, Selectors.cancel, [streamIterator],
          const <DartType>[], _sourceInformationBuilder.buildGeneric(node));
      add(new HAwait(pop(), abstractValueDomain.dynamicType));
    }

    tryBuilder
      ..closeTryBody()
      ..buildFinallyBlock(finalizerFunction)
      ..cleanUp();
  }

  HInstruction callSetRuntimeTypeInfo(HInstruction typeInfo,
      HInstruction newObject, SourceInformation sourceInformation) {
    // Set the runtime type information on the object.
    FunctionEntity typeInfoSetterFn = _commonElements.setRuntimeTypeInfo;
    // TODO(efortuna): Insert source information in this static invocation.
    _pushStaticInvocation(typeInfoSetterFn, <HInstruction>[newObject, typeInfo],
        abstractValueDomain.dynamicType, const <DartType>[],
        sourceInformation: sourceInformation);

    // The new object will now be referenced through the
    // `setRuntimeTypeInfo` call. We therefore set the type of that
    // instruction to be of the object's type.
    assert(
        stack.last is HInvokeStatic || stack.last == newObject,
        failedAt(
            CURRENT_ELEMENT_SPANNABLE,
            "Unexpected `stack.last`: Found ${stack.last}, "
            "expected ${newObject} or an HInvokeStatic. "
            "State: typeInfo=$typeInfo, stack=$stack."));
    stack.last.instructionType = newObject.instructionType;
    return pop();
  }

  @override
  void visitWhileStatement(ir.WhileStatement node) {
    assert(isReachable);
    HInstruction buildCondition() {
      node.condition.accept(this);
      return popBoolified();
    }

    loopHandler.handleLoop(
        node,
        localsMap.getCapturedLoopScope(closureDataLookup, node),
        localsMap.getJumpTargetForWhile(node),
        () {},
        buildCondition,
        () {}, () {
      node.body.accept(this);
    }, _sourceInformationBuilder.buildLoop(node));
  }

  @override
  visitDoStatement(ir.DoStatement node) {
    SourceInformation sourceInformation =
        _sourceInformationBuilder.buildLoop(node);
    // TODO(efortuna): I think this can be rewritten using
    // LoopHandler.handleLoop with some tricks about when the "update" happens.
    LocalsHandler savedLocals = new LocalsHandler.from(localsHandler);
    CapturedLoopScope loopClosureInfo =
        localsMap.getCapturedLoopScope(closureDataLookup, node);
    localsHandler.startLoop(loopClosureInfo, sourceInformation);
    JumpTarget target = localsMap.getJumpTargetForDo(node);
    JumpHandler jumpHandler = loopHandler.beginLoopHeader(node, target);
    HLoopInformation loopInfo = current.loopInformation;
    HBasicBlock loopEntryBlock = current;
    HBasicBlock bodyEntryBlock = current;
    bool hasContinues = target != null && target.isContinueTarget;
    if (hasContinues) {
      // Add extra block to hang labels on.
      // It doesn't currently work if they are on the same block as the
      // HLoopInfo. The handling of HLabeledBlockInformation will visit a
      // SubGraph that starts at the same block again, so the HLoopInfo is
      // either handled twice, or it's handled after the labeled block info,
      // both of which generate the wrong code.
      // Using a separate block is just a simple workaround.
      bodyEntryBlock = openNewBlock();
    }
    localsHandler.enterLoopBody(loopClosureInfo, sourceInformation);
    node.body.accept(this);

    // If there are no continues we could avoid the creation of the condition
    // block. This could also lead to a block having multiple entries and exits.
    HBasicBlock bodyExitBlock;
    bool isAbortingBody = false;
    if (current != null) {
      bodyExitBlock = close(new HGoto(abstractValueDomain));
    } else {
      isAbortingBody = true;
      bodyExitBlock = lastOpenedBlock;
    }

    SubExpression conditionExpression;
    bool loopIsDegenerate = isAbortingBody && !hasContinues;
    if (!loopIsDegenerate) {
      HBasicBlock conditionBlock = addNewBlock();

      List<LocalsHandler> continueHandlers = <LocalsHandler>[];
      jumpHandler
          .forEachContinue((HContinue instruction, LocalsHandler locals) {
        instruction.block.addSuccessor(conditionBlock);
        continueHandlers.add(locals);
      });

      if (!isAbortingBody) {
        bodyExitBlock.addSuccessor(conditionBlock);
      }

      if (!continueHandlers.isEmpty) {
        if (!isAbortingBody) continueHandlers.add(localsHandler);
        localsHandler =
            savedLocals.mergeMultiple(continueHandlers, conditionBlock);
        SubGraph bodyGraph = new SubGraph(bodyEntryBlock, bodyExitBlock);
        List<LabelDefinition> labels = jumpHandler.labels;
        HSubGraphBlockInformation bodyInfo =
            new HSubGraphBlockInformation(bodyGraph);
        HLabeledBlockInformation info;
        if (!labels.isEmpty) {
          info =
              new HLabeledBlockInformation(bodyInfo, labels, isContinue: true);
        } else {
          info = new HLabeledBlockInformation.implicit(bodyInfo, target,
              isContinue: true);
        }
        bodyEntryBlock.setBlockFlow(info, conditionBlock);
      }
      open(conditionBlock);

      node.condition.accept(this);
      assert(!isAborted());
      HInstruction conditionInstruction = popBoolified();
      HBasicBlock conditionEndBlock = close(new HLoopBranch(abstractValueDomain,
          conditionInstruction, HLoopBranch.DO_WHILE_LOOP));

      HBasicBlock avoidCriticalEdge = addNewBlock();
      conditionEndBlock.addSuccessor(avoidCriticalEdge);
      open(avoidCriticalEdge);
      close(new HGoto(abstractValueDomain));
      avoidCriticalEdge.addSuccessor(loopEntryBlock); // The back-edge.

      conditionExpression =
          new SubExpression(conditionBlock, conditionEndBlock);

      // Avoid a critical edge from the condition to the loop-exit body.
      HBasicBlock conditionExitBlock = addNewBlock();
      open(conditionExitBlock);
      close(new HGoto(abstractValueDomain));
      conditionEndBlock.addSuccessor(conditionExitBlock);

      loopHandler.endLoop(
          loopEntryBlock, conditionExitBlock, jumpHandler, localsHandler);

      loopEntryBlock.postProcessLoopHeader();
      SubGraph bodyGraph = new SubGraph(loopEntryBlock, bodyExitBlock);
      HLoopBlockInformation loopBlockInfo = new HLoopBlockInformation(
          HLoopBlockInformation.DO_WHILE_LOOP,
          null,
          wrapExpressionGraph(conditionExpression),
          wrapStatementGraph(bodyGraph),
          null,
          loopEntryBlock.loopInformation.target,
          loopEntryBlock.loopInformation.labels,
          sourceInformation);
      loopEntryBlock.setBlockFlow(loopBlockInfo, current);
      loopInfo.loopBlockInformation = loopBlockInfo;
    } else {
      // Since the loop has no back edge, we remove the loop information on the
      // header.
      loopEntryBlock.loopInformation = null;

      if (jumpHandler.hasAnyBreak()) {
        // Null branchBlock because the body of the do-while loop always aborts,
        // so we never get to the condition.
        loopHandler.endLoop(loopEntryBlock, null, jumpHandler, localsHandler);

        // Since the body of the loop has a break, we attach a synthesized label
        // to the body.
        SubGraph bodyGraph = new SubGraph(bodyEntryBlock, bodyExitBlock);
        JumpTarget target = localsMap.getJumpTargetForDo(node);
        LabelDefinition label =
            target.addLabel(null, 'loop', isBreakTarget: true);
        HLabeledBlockInformation info = new HLabeledBlockInformation(
            new HSubGraphBlockInformation(bodyGraph), <LabelDefinition>[label]);
        loopEntryBlock.setBlockFlow(info, current);
        jumpHandler.forEachBreak((HBreak breakInstruction, _) {
          HBasicBlock block = breakInstruction.block;
          block.addAtExit(new HBreak.toLabel(
              abstractValueDomain, label, sourceInformation));
          block.remove(breakInstruction);
        });
      }
    }
    jumpHandler.close();
  }

  @override
  void visitIfStatement(ir.IfStatement node) {
    handleIf(
        visitCondition: () => node.condition.accept(this),
        visitThen: () => node.then.accept(this),
        visitElse: () => node.otherwise?.accept(this),
        sourceInformation: _sourceInformationBuilder.buildIf(node));
  }

  void handleIf(
      {ir.Node node,
      void visitCondition(),
      void visitThen(),
      void visitElse(),
      SourceInformation sourceInformation}) {
    SsaBranchBuilder branchBuilder = new SsaBranchBuilder(this,
        node == null ? node : _elementMap.getSpannable(targetElement, node));
    branchBuilder.handleIf(visitCondition, visitThen, visitElse,
        sourceInformation: sourceInformation);
  }

  @override
  void visitAsExpression(ir.AsExpression node) {
    SourceInformation sourceInformation =
        _sourceInformationBuilder.buildAs(node);
    node.operand.accept(this);
    HInstruction expressionInstruction = pop();

    if (node.type is ir.InvalidType) {
      generateTypeError('invalid type', sourceInformation);
      return;
    }

    DartType type = _elementMap.getDartType(node.type);
    if (!node.isTypeError || options.implicitDowncastCheckPolicy.isEmitted) {
      HInstruction converted = typeBuilder.buildTypeConversion(
          expressionInstruction,
          localsHandler.substInContext(type),
          node.isTypeError
              ? HTypeConversion.CHECKED_MODE_CHECK
              : HTypeConversion.CAST_TYPE_CHECK,
          sourceInformation: sourceInformation);
      if (converted != expressionInstruction) {
        add(converted);
      }
      stack.add(converted);
    } else {
      stack.add(expressionInstruction);
    }
  }

  void generateError(FunctionEntity function, String message,
      AbstractValue typeMask, SourceInformation sourceInformation) {
    HInstruction errorMessage = graph.addConstantString(message, closedWorld);
    _pushStaticInvocation(
        function, [errorMessage], typeMask, const <DartType>[],
        sourceInformation: sourceInformation);
  }

  void generateTypeError(String message, SourceInformation sourceInformation) {
    generateError(
        _commonElements.throwTypeError,
        message,
        _typeInferenceMap.getReturnTypeOf(_commonElements.throwTypeError),
        sourceInformation);
  }

  void generateUnsupportedError(
      String message, SourceInformation sourceInformation) {
    generateError(
        _commonElements.throwUnsupportedError,
        message,
        _typeInferenceMap
            .getReturnTypeOf(_commonElements.throwUnsupportedError),
        sourceInformation);
  }

  @override
  void visitAssertStatement(ir.AssertStatement node) {
    if (!options.enableUserAssertions) return;
    if (node.message == null) {
      node.condition.accept(this);
      _pushStaticInvocation(
          _commonElements.assertHelper,
          <HInstruction>[pop()],
          _typeInferenceMap.getReturnTypeOf(_commonElements.assertHelper),
          const <DartType>[]);
      pop();
      return;
    }

    // if (assertTest(condition)) assertThrow(message);
    void buildCondition() {
      node.condition.accept(this);
      _pushStaticInvocation(
          _commonElements.assertTest,
          <HInstruction>[pop()],
          _typeInferenceMap.getReturnTypeOf(_commonElements.assertTest),
          const <DartType>[]);
    }

    void fail() {
      node.message.accept(this);
      _pushStaticInvocation(
          _commonElements.assertThrow,
          <HInstruction>[pop()],
          _typeInferenceMap.getReturnTypeOf(_commonElements.assertThrow),
          const <DartType>[]);
      pop();
    }

    handleIf(visitCondition: buildCondition, visitThen: fail);
  }

  /// Creates a [JumpHandler] for a statement. The node must be a jump
  /// target. If there are no breaks or continues targeting the statement,
  /// a special "null handler" is returned.
  ///
  /// [isLoopJump] is true when the jump handler is for a loop. This is used
  /// to distinguish the synthesized loop created for a switch statement with
  /// continue statements from simple switch statements.
  JumpHandler createJumpHandler(ir.TreeNode node, JumpTarget target,
      {bool isLoopJump: false}) {
    if (target == null) {
      // No breaks or continues to this node.
      return new NullJumpHandler(reporter);
    }
    if (isLoopJump && node is ir.SwitchStatement) {
      return new KernelSwitchCaseJumpHandler(this, target, node, localsMap);
    }

    return new JumpHandler(this, target);
  }

  @override
  void visitBreakStatement(ir.BreakStatement node) {
    assert(!isAborted());
    handleInTryStatement();
    JumpTarget target = localsMap.getJumpTargetForBreak(node);
    assert(target != null);
    JumpHandler handler = jumpTargets[target];
    assert(handler != null);
    SourceInformation sourceInformation =
        _sourceInformationBuilder.buildGoto(node);
    if (localsMap.generateContinueForBreak(node)) {
      if (handler.labels.isNotEmpty) {
        handler.generateContinue(sourceInformation, handler.labels.first);
      } else {
        handler.generateContinue(sourceInformation);
      }
    } else {
      if (handler.labels.isNotEmpty) {
        handler.generateBreak(sourceInformation, handler.labels.first);
      } else {
        handler.generateBreak(sourceInformation);
      }
    }
  }

  @override
  void visitLabeledStatement(ir.LabeledStatement node) {
    ir.Statement body = node.body;
    if (JumpVisitor.canBeBreakTarget(body)) {
      // loops and switches handle breaks on their own
      body.accept(this);
      return;
    }
    JumpTarget jumpTarget = localsMap.getJumpTargetForLabel(node);
    if (jumpTarget == null) {
      // The label is not needed.
      body.accept(this);
      return;
    }

    JumpHandler handler = createJumpHandler(node, jumpTarget);

    LocalsHandler beforeLocals = new LocalsHandler.from(localsHandler);

    HBasicBlock newBlock = openNewBlock();
    body.accept(this);
    SubGraph bodyGraph = new SubGraph(newBlock, lastOpenedBlock);

    HBasicBlock joinBlock = graph.addNewBlock();
    List<LocalsHandler> breakHandlers = <LocalsHandler>[];
    handler.forEachBreak((HBreak breakInstruction, LocalsHandler locals) {
      breakInstruction.block.addSuccessor(joinBlock);
      breakHandlers.add(locals);
    });

    if (!isAborted()) {
      goto(current, joinBlock);
      breakHandlers.add(localsHandler);
    }

    open(joinBlock);
    localsHandler = beforeLocals.mergeMultiple(breakHandlers, joinBlock);

    // There was at least one reachable break, so the label is needed.
    newBlock.setBlockFlow(
        new HLabeledBlockInformation(
            new HSubGraphBlockInformation(bodyGraph), handler.labels),
        joinBlock);
    handler.close();
  }

  /// Loop through the cases in a switch and create a mapping of case
  /// expressions to constants.
  Map<ir.Expression, ConstantValue> _buildSwitchCaseConstants(
      ir.SwitchStatement switchStatement) {
    Map<ir.Expression, ConstantValue> constants =
        new Map<ir.Expression, ConstantValue>();
    for (ir.SwitchCase switchCase in switchStatement.cases) {
      for (ir.Expression caseExpression in switchCase.expressions) {
        ConstantValue constant = _elementMap.getConstantValue(caseExpression);
        constants[caseExpression] = constant;
      }
    }
    return constants;
  }

  @override
  void visitContinueSwitchStatement(ir.ContinueSwitchStatement node) {
    handleInTryStatement();
    JumpTarget target = localsMap.getJumpTargetForContinueSwitch(node);
    assert(target != null);
    JumpHandler handler = jumpTargets[target];
    assert(handler != null);
    assert(target.labels.isNotEmpty);
    handler.generateContinue(
        _sourceInformationBuilder.buildGoto(node), target.labels.first);
  }

  @override
  void visitSwitchStatement(ir.SwitchStatement node) {
    SourceInformation sourceInformation =
        _sourceInformationBuilder.buildSwitch(node);
    // The switch case indices must match those computed in
    // [KernelSwitchCaseJumpHandler].
    bool hasContinue = false;
    Map<ir.SwitchCase, int> caseIndex = new Map<ir.SwitchCase, int>();
    int switchIndex = 1;
    bool hasDefault = false;
    for (ir.SwitchCase switchCase in node.cases) {
      if (_isDefaultCase(switchCase)) {
        hasDefault = true;
      }
      if (SwitchContinueAnalysis.containsContinue(switchCase.body)) {
        hasContinue = true;
      }
      caseIndex[switchCase] = switchIndex;
      switchIndex++;
    }

    JumpHandler jumpHandler =
        createJumpHandler(node, localsMap.getJumpTargetForSwitch(node));
    if (!hasContinue) {
      // If the switch statement has no switch cases targeted by continue
      // statements we encode the switch statement directly.
      _buildSimpleSwitchStatement(node, jumpHandler, sourceInformation);
    } else {
      _buildComplexSwitchStatement(
          node, jumpHandler, caseIndex, hasDefault, sourceInformation);
    }
  }

  /// Helper for building switch statements.
  static bool _isDefaultCase(ir.SwitchCase switchCase) =>
      switchCase == null || switchCase.isDefault;

  /// Helper for building switch statements.
  HInstruction _buildExpression(ir.SwitchStatement switchStatement) {
    switchStatement.expression.accept(this);
    return pop();
  }

  /// Helper method for creating the list of constants that make up the
  /// switch case branches.
  List<ConstantValue> _getSwitchConstants(
      ir.SwitchStatement parentSwitch, ir.SwitchCase switchCase) {
    Map<ir.Expression, ConstantValue> constantsLookup =
        _buildSwitchCaseConstants(parentSwitch);
    List<ConstantValue> constantList = <ConstantValue>[];
    if (switchCase != null) {
      for (var expression in switchCase.expressions) {
        constantList.add(constantsLookup[expression]);
      }
    }
    return constantList;
  }

  /// Builds a simple switch statement which does not handle uses of continue
  /// statements to labeled switch cases.
  void _buildSimpleSwitchStatement(ir.SwitchStatement switchStatement,
      JumpHandler jumpHandler, SourceInformation sourceInformation) {
    void buildSwitchCase(ir.SwitchCase switchCase) {
      switchCase.body.accept(this);
    }

    _handleSwitch(
        switchStatement,
        jumpHandler,
        _buildExpression,
        switchStatement.cases,
        _getSwitchConstants,
        _isDefaultCase,
        buildSwitchCase,
        sourceInformation);
    jumpHandler.close();
  }

  /// Builds a switch statement that can handle arbitrary uses of continue
  /// statements to labeled switch cases.
  void _buildComplexSwitchStatement(
      ir.SwitchStatement switchStatement,
      JumpHandler jumpHandler,
      Map<ir.SwitchCase, int> caseIndex,
      bool hasDefault,
      SourceInformation sourceInformation) {
    // If the switch statement has switch cases targeted by continue
    // statements we create the following encoding:
    //
    //   switch (e) {
    //     l_1: case e0: s_1; break;
    //     l_2: case e1: s_2; continue l_i;
    //     ...
    //     l_n: default: s_n; continue l_j;
    //   }
    //
    // is encoded as
    //
    //   var target;
    //   switch (e) {
    //     case e1: target = 1; break;
    //     case e2: target = 2; break;
    //     ...
    //     default: target = n; break;
    //   }
    //   l: while (true) {
    //    switch (target) {
    //       case 1: s_1; break l;
    //       case 2: s_2; target = i; continue l;
    //       ...
    //       case n: s_n; target = j; continue l;
    //     }
    //   }
    //
    // This is because JS does not have this same "continue label" semantics so
    // we encode it in the form of a state machine.

    JumpTarget switchTarget = localsMap.getJumpTargetForSwitch(switchStatement);
    localsHandler.updateLocal(switchTarget, graph.addConstantNull(closedWorld));

    var switchCases = switchStatement.cases;
    if (!hasDefault) {
      // Use null as the marker for a synthetic default clause.
      // The synthetic default is added because otherwise there would be no
      // good place to give a default value to the local.
      switchCases = new List<ir.SwitchCase>.from(switchCases);
      switchCases.add(null);
    }

    void buildSwitchCase(ir.SwitchCase switchCase) {
      SourceInformation caseSourceInformation = sourceInformation;
      if (switchCase != null) {
        caseSourceInformation = _sourceInformationBuilder.buildGoto(switchCase);
        // Generate 'target = i; break;' for switch case i.
        int index = caseIndex[switchCase];
        HInstruction value = graph.addConstantInt(index, closedWorld);
        localsHandler.updateLocal(switchTarget, value,
            sourceInformation: caseSourceInformation);
      } else {
        // Generate synthetic default case 'target = null; break;'.
        HInstruction nullValue = graph.addConstantNull(closedWorld);
        localsHandler.updateLocal(switchTarget, nullValue,
            sourceInformation: caseSourceInformation);
      }
      jumpTargets[switchTarget].generateBreak(caseSourceInformation);
    }

    _handleSwitch(
        switchStatement,
        jumpHandler,
        _buildExpression,
        switchCases,
        _getSwitchConstants,
        _isDefaultCase,
        buildSwitchCase,
        sourceInformation);
    jumpHandler.close();

    HInstruction buildCondition() => graph.addConstantBool(true, closedWorld);

    void buildSwitch() {
      HInstruction buildExpression(ir.SwitchStatement notUsed) {
        return localsHandler.readLocal(switchTarget);
      }

      List<ConstantValue> getConstants(
          ir.SwitchStatement parentSwitch, ir.SwitchCase switchCase) {
        return <ConstantValue>[
          constantSystem.createIntFromInt(caseIndex[switchCase])
        ];
      }

      void buildSwitchCase(ir.SwitchCase switchCase) {
        switchCase.body.accept(this);
        if (!isAborted()) {
          // Ensure that we break the loop if the case falls through. (This
          // is only possible for the last case.)
          jumpTargets[switchTarget].generateBreak(sourceInformation);
        }
      }

      // Pass a [NullJumpHandler] because the target for the contained break
      // is not the generated switch statement but instead the loop generated
      // in the call to [handleLoop] below.
      _handleSwitch(
          switchStatement, // nor is buildExpression.
          new NullJumpHandler(reporter),
          buildExpression,
          switchStatement.cases,
          getConstants,
          (_) => false, // No case is default.
          buildSwitchCase,
          sourceInformation);
    }

    void buildLoop() {
      loopHandler.handleLoop(
          switchStatement,
          localsMap.getCapturedLoopScope(closureDataLookup, switchStatement),
          switchTarget,
          () {},
          buildCondition,
          () {},
          buildSwitch,
          _sourceInformationBuilder.buildLoop(switchStatement));
    }

    if (hasDefault) {
      buildLoop();
    } else {
      // If the switch statement has no default case, surround the loop with
      // a test of the target. So:
      // `if (target) while (true) ...` If there's no default case, target is
      // null, so we don't drop into the while loop.
      void buildCondition() {
        js.Template code = js.js.parseForeignJS('#');
        push(new HForeignCode(code, abstractValueDomain.boolType,
            [localsHandler.readLocal(switchTarget)],
            nativeBehavior: native.NativeBehavior.PURE));
      }

      handleIf(
          node: switchStatement,
          visitCondition: buildCondition,
          visitThen: buildLoop,
          visitElse: () => {},
          sourceInformation: sourceInformation);
    }
  }

  /// Creates a switch statement.
  ///
  /// [jumpHandler] is the [JumpHandler] for the created switch statement.
  /// [buildSwitchCase] creates the statements for the switch case.
  void _handleSwitch(
      ir.SwitchStatement switchStatement,
      JumpHandler jumpHandler,
      HInstruction buildExpression(ir.SwitchStatement statement),
      List<ir.SwitchCase> switchCases,
      List<ConstantValue> getConstants(
          ir.SwitchStatement parentSwitch, ir.SwitchCase switchCase),
      bool isDefaultCase(ir.SwitchCase switchCase),
      void buildSwitchCase(ir.SwitchCase switchCase),
      SourceInformation sourceInformation) {
    HBasicBlock expressionStart = openNewBlock();
    HInstruction expression = buildExpression(switchStatement);

    if (switchCases.isEmpty) {
      return;
    }

    HSwitch switchInstruction =
        new HSwitch(abstractValueDomain, <HInstruction>[expression]);
    HBasicBlock expressionEnd = close(switchInstruction);
    LocalsHandler savedLocals = localsHandler;

    List<HStatementInformation> statements = <HStatementInformation>[];
    bool hasDefault = false;
    for (ir.SwitchCase switchCase in switchCases) {
      HBasicBlock block = graph.addNewBlock();
      for (ConstantValue constant
          in getConstants(switchStatement, switchCase)) {
        HConstant hConstant = graph.addConstant(constant, closedWorld);
        switchInstruction.inputs.add(hConstant);
        hConstant.usedBy.add(switchInstruction);
        expressionEnd.addSuccessor(block);
      }

      if (isDefaultCase(switchCase)) {
        // An HSwitch has n inputs and n+1 successors, the last being the
        // default case.
        expressionEnd.addSuccessor(block);
        hasDefault = true;
      }
      open(block);
      localsHandler = new LocalsHandler.from(savedLocals);
      buildSwitchCase(switchCase);
      if (!isAborted() &&
          // TODO(johnniwinther): Reinsert this if `isReachable` is no longer
          // set to `false` when `_tryInlineMethod` sees an always throwing
          // method.
          //switchCase == switchCases.last &&
          !isDefaultCase(switchCase)) {
        // If there is no default, we will add one later to avoid
        // the critical edge. So we generate a break statement to make
        // sure the last case does not fall through to the default case.
        jumpHandler.generateBreak(sourceInformation);
      }
      statements.add(
          new HSubGraphBlockInformation(new SubGraph(block, lastOpenedBlock)));
    }

    // Add a join-block if necessary.
    // We create [joinBlock] early, and then go through the cases that might
    // want to jump to it. In each case, if we add [joinBlock] as a successor
    // of another block, we also add an element to [caseHandlers] that is used
    // to create the phis in [joinBlock].
    // If we never jump to the join block, [caseHandlers] will stay empty, and
    // the join block is never added to the graph.
    HBasicBlock joinBlock = new HBasicBlock();
    List<LocalsHandler> caseHandlers = <LocalsHandler>[];
    jumpHandler.forEachBreak((HBreak instruction, LocalsHandler locals) {
      instruction.block.addSuccessor(joinBlock);
      caseHandlers.add(locals);
    });
    jumpHandler.forEachContinue((HContinue instruction, LocalsHandler locals) {
      assert(
          false,
          failedAt(_elementMap.getSpannable(targetElement, switchStatement),
              'Continue cannot target a switch.'));
    });
    if (!isAborted()) {
      current.close(new HGoto(abstractValueDomain));
      lastOpenedBlock.addSuccessor(joinBlock);
      caseHandlers.add(localsHandler);
    }
    if (!hasDefault) {
      // Always create a default case, to avoid a critical edge in the
      // graph.
      HBasicBlock defaultCase = addNewBlock();
      expressionEnd.addSuccessor(defaultCase);
      open(defaultCase);
      close(new HGoto(abstractValueDomain));
      defaultCase.addSuccessor(joinBlock);
      caseHandlers.add(savedLocals);
      statements.add(new HSubGraphBlockInformation(
          new SubGraph(defaultCase, defaultCase)));
    }
    assert(caseHandlers.length == joinBlock.predecessors.length);
    if (caseHandlers.length != 0) {
      graph.addBlock(joinBlock);
      open(joinBlock);
      if (caseHandlers.length == 1) {
        localsHandler = caseHandlers[0];
      } else {
        localsHandler = savedLocals.mergeMultiple(caseHandlers, joinBlock);
      }
    } else {
      // The joinblock is not used.
      joinBlock = null;
    }

    HSubExpressionBlockInformation expressionInfo =
        new HSubExpressionBlockInformation(
            new SubExpression(expressionStart, expressionEnd));
    expressionStart.setBlockFlow(
        new HSwitchBlockInformation(expressionInfo, statements,
            jumpHandler.target, jumpHandler.labels, sourceInformation),
        joinBlock);

    jumpHandler.close();
  }

  @override
  void visitConditionalExpression(ir.ConditionalExpression node) {
    SsaBranchBuilder brancher = new SsaBranchBuilder(this);
    brancher.handleConditional(() => node.condition.accept(this),
        () => node.then.accept(this), () => node.otherwise.accept(this));
  }

  @override
  void visitLogicalExpression(ir.LogicalExpression node) {
    SsaBranchBuilder brancher = new SsaBranchBuilder(this);
    String operator = node.operator;
    // ir.LogicalExpression claims to allow '??' as an operator but currently
    // that is expanded into a let-tree.
    assert(operator == '&&' || operator == '||');
    _handleLogicalExpression(node.left, () => node.right.accept(this), brancher,
        operator, _sourceInformationBuilder.buildBinary(node));
  }

  /// Optimizes logical binary expression where the left has the same logical
  /// binary operator.
  ///
  /// This method transforms the operator by optimizing the case where [left] is
  /// a logical "and" or logical "or". Then it uses [branchBuilder] to build the
  /// graph for the optimized expression.
  ///
  /// For example, `(x && y) && z` is transformed into `x && (y && z)`:
  ///
  void _handleLogicalExpression(
      ir.Expression left,
      void visitRight(),
      SsaBranchBuilder brancher,
      String operator,
      SourceInformation sourceInformation) {
    if (left is ir.LogicalExpression && left.operator == operator) {
      ir.Expression innerLeft = left.left;
      ir.Expression middle = left.right;
      _handleLogicalExpression(
          innerLeft,
          () => _handleLogicalExpression(middle, visitRight, brancher, operator,
              _sourceInformationBuilder.buildBinary(middle)),
          brancher,
          operator,
          sourceInformation);
    } else {
      brancher.handleLogicalBinary(
          () => left.accept(this), visitRight, sourceInformation,
          isAnd: operator == '&&');
    }
  }

  @override
  void visitIntLiteral(ir.IntLiteral node) {
    stack.add(graph.addConstantIntAsUnsigned(node.value, closedWorld));
  }

  @override
  void visitDoubleLiteral(ir.DoubleLiteral node) {
    stack.add(graph.addConstantDouble(node.value, closedWorld));
  }

  @override
  void visitBoolLiteral(ir.BoolLiteral node) {
    stack.add(graph.addConstantBool(node.value, closedWorld));
  }

  @override
  void visitStringLiteral(ir.StringLiteral node) {
    stack.add(graph.addConstantString(node.value, closedWorld));
  }

  @override
  void visitSymbolLiteral(ir.SymbolLiteral node) {
    stack.add(
        graph.addConstant(_elementMap.getConstantValue(node), closedWorld));
    registry?.registerConstSymbol(node.value);
  }

  @override
  void visitNullLiteral(ir.NullLiteral node) {
    stack.add(graph.addConstantNull(closedWorld));
  }

  /// Set the runtime type information if necessary.
  HInstruction _setListRuntimeTypeInfoIfNeeded(HInstruction object,
      InterfaceType type, SourceInformation sourceInformation) {
    if (!rtiNeed.classNeedsTypeArguments(type.element) || type.treatAsRaw) {
      return object;
    }
    List<HInstruction> arguments = <HInstruction>[];
    for (DartType argument in type.typeArguments) {
      arguments.add(typeBuilder.analyzeTypeArgument(argument, sourceElement));
    }
    // TODO(15489): Register at codegen.
    registry?.registerInstantiation(type);
    return callSetRuntimeTypeInfoWithTypeArguments(
        type, arguments, object, sourceInformation);
  }

  @override
  void visitListLiteral(ir.ListLiteral node) {
    HInstruction listInstruction;
    if (node.isConst) {
      listInstruction =
          graph.addConstant(_elementMap.getConstantValue(node), closedWorld);
    } else {
      List<HInstruction> elements = <HInstruction>[];
      for (ir.Expression element in node.expressions) {
        element.accept(this);
        elements.add(pop());
      }
      listInstruction = buildLiteralList(elements);
      add(listInstruction);
      SourceInformation sourceInformation =
          _sourceInformationBuilder.buildListLiteral(node);
      InterfaceType type = localsHandler.substInContext(
          _commonElements.listType(_elementMap.getDartType(node.typeArgument)));
      listInstruction = _setListRuntimeTypeInfoIfNeeded(
          listInstruction, type, sourceInformation);
    }

    AbstractValue type = _typeInferenceMap.typeOfListLiteral(
        targetElement, node, abstractValueDomain);
    if (!abstractValueDomain.containsAll(type)) {
      listInstruction.instructionType = type;
    }
    stack.add(listInstruction);
  }

  @override
  void visitMapLiteral(ir.MapLiteral node) {
    if (node.isConst) {
      stack.add(
          graph.addConstant(_elementMap.getConstantValue(node), closedWorld));
      return;
    }

    // The map literal constructors take the key-value pairs as a List
    List<HInstruction> constructorArgs = <HInstruction>[];
    for (ir.MapEntry mapEntry in node.entries) {
      mapEntry.accept(this);
      constructorArgs.add(pop());
      constructorArgs.add(pop());
    }

    // The constructor is a procedure because it's a factory.
    FunctionEntity constructor;
    List<HInstruction> inputs = <HInstruction>[];
    if (constructorArgs.isEmpty) {
      constructor = _commonElements.mapLiteralConstructorEmpty;
    } else {
      constructor = _commonElements.mapLiteralConstructor;
      HLiteralList argList = buildLiteralList(constructorArgs);
      add(argList);
      inputs.add(argList);
    }

    assert(
        constructor is ConstructorEntity && constructor.isFactoryConstructor);

    InterfaceType type = localsHandler.substInContext(_commonElements.mapType(
        _elementMap.getDartType(node.keyType),
        _elementMap.getDartType(node.valueType)));
    ClassEntity cls = constructor.enclosingClass;

    if (rtiNeed.classNeedsTypeArguments(cls)) {
      List<HInstruction> typeInputs = <HInstruction>[];
      type.typeArguments.forEach((DartType argument) {
        typeInputs
            .add(typeBuilder.analyzeTypeArgument(argument, sourceElement));
      });

      // We lift this common call pattern into a helper function to save space
      // in the output.
      if (typeInputs
          .every((HInstruction input) => input.isNull(abstractValueDomain))) {
        if (constructorArgs.isEmpty) {
          constructor = _commonElements.mapLiteralUntypedEmptyMaker;
        } else {
          constructor = _commonElements.mapLiteralUntypedMaker;
        }
      } else {
        inputs.addAll(typeInputs);
      }
    }

    // If runtime type information is needed and the map literal has no type
    // parameters, 'constructor' is a static function that forwards the call to
    // the factory constructor without type parameters.
    assert(constructor.isFunction ||
        (constructor is ConstructorEntity && constructor.isFactoryConstructor));

    // The instruction type will always be a subtype of the mapLiteralClass, but
    // type inference might discover a more specific type, or find nothing (in
    // dart2js unit tests).

    AbstractValue mapType = abstractValueDomain
        .createNonNullSubtype(_commonElements.mapLiteralClass);
    AbstractValue returnTypeMask =
        _typeInferenceMap.getReturnTypeOf(constructor);
    AbstractValue instructionType =
        abstractValueDomain.intersection(mapType, returnTypeMask);

    addImplicitInstantiation(type);
    _pushStaticInvocation(
        constructor, inputs, instructionType, const <DartType>[]);
    removeImplicitInstantiation(type);
  }

  @override
  void visitMapEntry(ir.MapEntry mapEntry) {
    // Visit value before the key because each will push an expression to the
    // stack, so when we pop them off, the key is popped first, then the value.
    mapEntry.value.accept(this);
    mapEntry.key.accept(this);
  }

  @override
  void visitTypeLiteral(ir.TypeLiteral node) {
    SourceInformation sourceInformation =
        _sourceInformationBuilder.buildGet(node);
    ir.DartType type = node.type;
    if (type is ir.InterfaceType ||
        type is ir.DynamicType ||
        type is ir.TypedefType ||
        type is ir.FunctionType) {
      ConstantValue constant = _elementMap.getConstantValue(node);
      stack.add(graph.addConstant(constant, closedWorld,
          sourceInformation: sourceInformation));
      return;
    }
    assert(
        type is ir.TypeParameterType,
        failedAt(
            CURRENT_ELEMENT_SPANNABLE, "Unexpected type literal ${node}."));
    // For other types (e.g. TypeParameterType, function types from expanded
    // typedefs), look-up or construct a reified type representation and convert
    // to a RuntimeType.

    DartType dartType = _elementMap.getDartType(type);
    dartType = localsHandler.substInContext(dartType);
    HInstruction value = typeBuilder.analyzeTypeArgument(
        dartType, sourceElement,
        sourceInformation: sourceInformation);
    _pushStaticInvocation(
        _commonElements.runtimeTypeToString,
        <HInstruction>[value],
        abstractValueDomain.stringType,
        const <DartType>[],
        sourceInformation: sourceInformation);
    _pushStaticInvocation(
        _commonElements.createRuntimeType,
        <HInstruction>[pop()],
        _typeInferenceMap.getReturnTypeOf(_commonElements.createRuntimeType),
        const <DartType>[],
        sourceInformation: sourceInformation);
  }

  @override
  void visitStaticGet(ir.StaticGet node) {
    ir.Member staticTarget = node.target;
    SourceInformation sourceInformation =
        _sourceInformationBuilder.buildGet(node);
    if (staticTarget is ir.Procedure &&
        staticTarget.kind == ir.ProcedureKind.Getter) {
      FunctionEntity getter = _elementMap.getMember(staticTarget);
      // Invoke the getter
      _pushStaticInvocation(getter, const <HInstruction>[],
          _typeInferenceMap.getReturnTypeOf(getter), const <DartType>[],
          sourceInformation: sourceInformation);
    } else if (staticTarget is ir.Field) {
      FieldEntity field = _elementMap.getField(staticTarget);
      ConstantValue value = _elementMap.getFieldConstantValue(field);
      if (value != null) {
        if (!field.isAssignable) {
          var unit = compiler.backend.outputUnitData.outputUnitForMember(field);
          // TODO(sigmund): this is not equivalent to what the old FE does: if
          // there is no prefix the old FE wouldn't treat this in any special
          // way. Also, if the prefix points to a constant in the main output
          // unit, the old FE would still generate a deferred wrapper here.
          if (!compiler.backend.outputUnitData
              .hasOnlyNonDeferredImportPaths(targetElement, field)) {
            stack.add(graph.addDeferredConstant(
                value, unit, sourceInformation, compiler, closedWorld));
          } else {
            stack.add(graph.addConstant(value, closedWorld,
                sourceInformation: sourceInformation));
          }
        } else {
          push(new HStatic(field, _typeInferenceMap.getInferredTypeOf(field),
              sourceInformation));
        }
      } else {
        push(new HLazyStatic(field, _typeInferenceMap.getInferredTypeOf(field),
            sourceInformation));
      }
    } else {
      MemberEntity member = _elementMap.getMember(staticTarget);
      push(new HStatic(member, _typeInferenceMap.getInferredTypeOf(member),
          sourceInformation));
    }
  }

  @override
  void visitStaticSet(ir.StaticSet node) {
    node.value.accept(this);
    HInstruction value = pop();

    ir.Member staticTarget = node.target;
    if (staticTarget is ir.Procedure) {
      FunctionEntity setter = _elementMap.getMember(staticTarget);
      // Invoke the setter
      _pushStaticInvocation(setter, <HInstruction>[value],
          _typeInferenceMap.getReturnTypeOf(setter), const <DartType>[]);
      pop();
    } else {
      add(new HStaticStore(
          abstractValueDomain,
          _elementMap.getMember(staticTarget),
          typeBuilder.potentiallyCheckOrTrustTypeOfAssignment(
              value, _getDartTypeIfValid(staticTarget.setterType))));
    }
    stack.add(value);
  }

  @override
  void visitPropertyGet(ir.PropertyGet node) {
    node.receiver.accept(this);
    HInstruction receiver = pop();

    _pushDynamicInvocation(
        node,
        _typeInferenceMap.receiverTypeOfGet(node),
        new Selector.getter(_elementMap.getName(node.name)),
        <HInstruction>[receiver],
        const <DartType>[],
        _sourceInformationBuilder.buildGet(node));
  }

  @override
  void visitVariableGet(ir.VariableGet node) {
    ir.VariableDeclaration variable = node.variable;
    HInstruction letBinding = letBindings[variable];
    if (letBinding != null) {
      stack.add(letBinding);
      return;
    }

    Local local = localsMap.getLocalVariable(node.variable);
    stack.add(localsHandler.readLocal(local,
        sourceInformation: _sourceInformationBuilder.buildGet(node)));
  }

  @override
  void visitPropertySet(ir.PropertySet node) {
    node.receiver.accept(this);
    HInstruction receiver = pop();
    node.value.accept(this);
    HInstruction value = pop();

    _pushDynamicInvocation(
        node,
        _typeInferenceMap.receiverTypeOfSet(node, abstractValueDomain),
        new Selector.setter(_elementMap.getName(node.name)),
        <HInstruction>[receiver, value],
        const <DartType>[],
        _sourceInformationBuilder.buildAssignment(node));

    pop();
    stack.add(value);
  }

  @override
  void visitDirectPropertyGet(ir.DirectPropertyGet node) {
    node.receiver.accept(this);
    HInstruction receiver = pop();

    // Fake direct call with a dynamic call.
    // TODO(sra): Implement direct invocations properly.
    _pushDynamicInvocation(
        node,
        _typeInferenceMap.receiverTypeOfDirectGet(node),
        new Selector.getter(_elementMap.getMember(node.target).memberName),
        <HInstruction>[receiver],
        const <DartType>[],