Decouple WorkItem from Compiler

pkg/compiler/lib/src/enqueue.dart

 // Copyright (c) 2012, 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.
 
 library dart2js.enqueue;
 
 import 'dart:collection' show Queue;
 
 import 'cache_strategy.dart';
 import 'common/backend_api.dart' show Backend;
@@ skipping 36 matching lines @@
 
   String get name => 'Enqueue';
 
   EnqueueTask(Compiler compiler)
       : this.compiler = compiler,
         super(compiler.measurer) {
     _resolution = new ResolutionEnqueuer(
         this,
         compiler.options,
         compiler.resolution,
-        compiler.enqueuerFilter,
         compiler.options.analyzeOnly && compiler.options.analyzeMain
-            ? const EnqueuerStrategy()
+            ? const DirectEnqueuerStrategy()
             : const TreeShakingEnqueuerStrategy(),
         compiler.globalDependencies,
         compiler.backend,
         compiler.coreClasses,
         compiler.cacheStrategy);
     _codegen = compiler.backend.createCodegenEnqueuer(this, compiler);
   }
 
   ResolutionEnqueuer get resolution => _resolution;
   Enqueuer get codegen => _codegen;
 
   void forgetElement(Element element) {
     resolution.forgetElement(element, compiler);
     codegen.forgetElement(element, compiler);
   }
 }
 
 abstract class Enqueuer {
-  CompilerTask get task;
   WorldBuilder get universe;
   native.NativeEnqueuer get nativeEnqueuer;
   void forgetElement(Element element, Compiler compiler);
-  void processInstantiatedClassMembers(ClassElement cls);
-  void processInstantiatedClassMember(ClassElement cls, Element member);
-  void handleUnseenSelectorInternal(DynamicUse dynamicUse);
-  void registerStaticUse(StaticUse staticUse);
-  void registerStaticUseInternal(StaticUse staticUse);
-  void registerDynamicUse(DynamicUse dynamicUse);
+
+  // TODO(johnniwinther): Initialize [_impactStrategy] to `null`.
+  ImpactStrategy _impactStrategy = const ImpactStrategy();
+
+  ImpactStrategy get impactStrategy => _impactStrategy;
+
+  void open(ImpactStrategy impactStrategy) {
+    _impactStrategy = impactStrategy;
+  }
+
+  void close() {
+    // TODO(johnniwinther): Set [_impactStrategy] to `null` and [queueIsClosed]
+    // to `false` here.
+    _impactStrategy = const ImpactStrategy();
+  }
 
   /// Returns [:true:] if this enqueuer is the resolution enqueuer.
   bool get isResolutionQueue;
 
   bool queueIsClosed;
 
   bool get queueIsEmpty;
 
   ImpactUseCase get impactUse;
 
-  /**
-   * Documentation wanted -- johnniwinther
-   *
-   * Invariant: [element] must be a declaration element.
-   */
-  void addToWorkList(Element element);
-
-  void enableIsolateSupport();
-
-  void registerInstantiatedType(InterfaceType type);
   void forEach(void f(WorkItem work));
 
-  /// Apply the [worldImpact] to this enqueuer. If the [impactSource] is provided
-  /// the impact strategy will remove it from the element impact cache, if it is
-  /// no longer needed.
-  void applyImpact(ImpactStrategy impactStrategy, WorldImpact worldImpact,
-      {Element impactSource});
+  /// Apply the [worldImpact] to this enqueuer. If the [impactSource] is
+  /// provided the impact strategy will remove it from the element impact cache,
+  /// if it is no longer needed.
+  void applyImpact(WorldImpact worldImpact, {Element impactSource});
   bool checkNoEnqueuedInvokedInstanceMethods();
   void logSummary(log(message));
 
   /// Returns [:true:] if [member] has been processed by this enqueuer.
   bool isProcessed(Element member);
 
   Iterable<Entity> get processedEntities;
 
   Iterable<ClassElement> get processedClasses;
 }
 
+abstract class EnqueuerImpl extends Enqueuer {
+  CompilerTask get task;
+  void processInstantiatedClassMembers(ClassElement cls);
+  void processInstantiatedClassMember(ClassElement cls, Element member);
+  void registerStaticUse(StaticUse staticUse);
+  void registerStaticUseInternal(StaticUse staticUse);
+  void registerTypeUse(TypeUse typeUse);
+  void registerTypeUseInternal(TypeUse typeUse);
+  void registerDynamicUse(DynamicUse dynamicUse);
+  void handleUnseenSelectorInternal(DynamicUse dynamicUse);
+}
+
 /// [Enqueuer] which is specific to resolution.
-class ResolutionEnqueuer extends Enqueuer {
+class ResolutionEnqueuer extends EnqueuerImpl {
   final CompilerTask task;
   final String name;
   final Resolution resolution;
-  final QueueFilter filter;
   final CompilerOptions options;
   final Backend backend;
   final GlobalDependencyRegistry globalDependencies;
   final CommonElements commonElements;
   final native.NativeEnqueuer nativeEnqueuer;
 
   final EnqueuerStrategy strategy;
   final Map<String, Set<Element>> instanceMembersByName =
       new Map<String, Set<Element>>();
   final Map<String, Set<Element>> instanceFunctionsByName =
       new Map<String, Set<Element>>();
   final Set<ClassElement> _processedClasses = new Set<ClassElement>();
   Set<ClassElement> recentClasses = new Setlet<ClassElement>();
   final ResolutionWorldBuilderImpl _universe;
 
   bool queueIsClosed = false;
 
   WorldImpactVisitor impactVisitor;
 
-  ImpactStrategy impactStrategy;
-
   ResolutionEnqueuer(
       this.task,
       this.options,
       this.resolution,
-      this.filter,
       this.strategy,
       this.globalDependencies,
       Backend backend,
       CommonElements commonElements,
       CacheStrategy cacheStrategy,
       [this.name = 'resolution enqueuer'])
       : this.backend = backend,
         this.commonElements = commonElements,
         this.nativeEnqueuer = backend.nativeResolutionEnqueuer(),
         processedElements = new Set<AstElement>(),
         queue = new Queue<ResolutionWorkItem>(),
         deferredQueue = new Queue<_DeferredAction>(),
         _universe = new ResolutionWorldBuilderImpl(
             backend, commonElements, cacheStrategy, const TypeMaskStrategy()) {
-    impactVisitor = new _EnqueuerImpactVisitor(this);
+    impactVisitor = new EnqueuerImplImpactVisitor(this);
   }
 
   ResolutionWorldBuilder get universe => _universe;
 
   OpenWorld get openWorld => universe.openWorld;
 
   bool get queueIsEmpty => queue.isEmpty;
 
   DiagnosticReporter get reporter => resolution.reporter;
 
   bool isClassProcessed(ClassElement cls) => _processedClasses.contains(cls);
 
   Iterable<ClassElement> get processedClasses => _processedClasses;
 
   /**
    * Documentation wanted -- johnniwinther
    *
    * Invariant: [element] must be a declaration element.
    */
   void addToWorkList(Element element) {
     assert(invariant(element, element.isDeclaration));
     internalAddToWorkList(element);
   }
 
-  void applyImpact(ImpactStrategy impactStrategy, WorldImpact worldImpact,
-      {Element impactSource}) {
+  void applyImpact(WorldImpact worldImpact, {Element impactSource}) {
+    if (worldImpact.isEmpty) return;
     impactStrategy.visitImpact(
         impactSource, worldImpact, impactVisitor, impactUse);
   }
 
   void registerInstantiatedType(InterfaceType type) {
     _registerInstantiatedType(type, globalDependency: true);
   }
 
   void _registerInstantiatedType(InterfaceType type,
       {ConstructorElement constructor,
       bool mirrorUsage: false,
       bool nativeUsage: false,
       bool globalDependency: false,
       bool isRedirection: false}) {
     task.measure(() {
       ClassElement cls = type.element;
       cls.ensureResolved(resolution);
       bool isNative = backend.isNative(cls);
       _universe.registerTypeInstantiation(type,
           constructor: constructor,
           isNative: isNative,
           byMirrors: mirrorUsage,
           isRedirection: isRedirection, onImplemented: (ClassElement cls) {
-        backend.registerImplementedClass(cls, this);
+        applyImpact(backend.registerImplementedClass(cls, forResolution: true));
       });
       if (globalDependency && !mirrorUsage) {
         globalDependencies.registerDependency(type.element);
       }
       if (nativeUsage) {
         nativeEnqueuer.onInstantiatedType(type);
       }
       backend.registerInstantiatedType(type);
       // TODO(johnniwinther): Share this reasoning with [Universe].
       if (!cls.isAbstract || isNative || mirrorUsage) {
         processInstantiatedClass(cls);
       }
     });
   }
 
   bool checkNoEnqueuedInvokedInstanceMethods() {
-    return filter.checkNoEnqueuedInvokedInstanceMethods(this);
+    return strategy.checkEnqueuerConsistency(this);
   }
 
   void processInstantiatedClassMembers(ClassElement cls) {
     strategy.processInstantiatedClass(this, cls);
   }
 
   void processInstantiatedClassMember(ClassElement cls, Element member) {
     assert(invariant(member, member.isDeclaration));
     if (isProcessed(member)) return;
     if (!member.isInstanceMember) return;
@@ skipping 27 matching lines @@
         addToWorkList(member);
         return;
       }
     } else if (member.isFunction) {
       FunctionElement function = member;
       function.computeType(resolution);
       if (function.name == Identifiers.noSuchMethod_) {
         registerNoSuchMethod(function);
       }
       if (function.name == Identifiers.call && !cls.typeVariables.isEmpty) {
-        registerCallMethodWithFreeTypeVariables(function);
+        _registerCallMethodWithFreeTypeVariables(function);
       }
       // If there is a property access with the same name as a method we
       // need to emit the method.
       if (_universe.hasInvokedGetter(function, openWorld)) {
         registerClosurizedMember(function);
         addToWorkList(function);
         return;
       }
       // Store the member in [instanceFunctionsByName] to catch
       // getters on the function.
@@ skipping 44 matching lines @@
         if (_processedClasses.contains(superclass)) return;
 
         _processedClasses.add(superclass);
         recentClasses.add(superclass);
         superclass.ensureResolved(resolution);
         superclass.implementation.forEachMember(processInstantiatedClassMember);
         resolution.ensureClassMembers(superclass);
         // We only tell the backend once that [superclass] was instantiated, so
         // any additional dependencies must be treated as global
         // dependencies.
-        backend.registerInstantiatedClass(superclass, this);
+        applyImpact(
+            backend.registerInstantiatedClass(superclass, forResolution: true));
       }
 
       ClassElement superclass = cls;
       while (superclass != null) {
         processClass(superclass);
         superclass = superclass.superclass;
       }
     });
   }
 
@@ skipping 63 matching lines @@
    */
   void registerStaticUse(StaticUse staticUse) {
     strategy.processStaticUse(this, staticUse);
   }
 
   void registerStaticUseInternal(StaticUse staticUse) {
     Element element = staticUse.element;
     assert(invariant(element, element.isDeclaration,
         message: "Element ${element} is not the declaration."));
     _universe.registerStaticUse(staticUse);
-    backend.registerStaticUse(this, element);
+    applyImpact(backend.registerStaticUse(element, forResolution: true));
     bool addElement = true;
     switch (staticUse.kind) {
       case StaticUseKind.STATIC_TEAR_OFF:
-        backend.registerGetOfStaticFunction(this);
+        applyImpact(backend.registerGetOfStaticFunction());
         break;
       case StaticUseKind.FIELD_GET:
       case StaticUseKind.FIELD_SET:
       case StaticUseKind.CLOSURE:
         // TODO(johnniwinther): Avoid this. Currently [FIELD_GET] and
         // [FIELD_SET] contains [BoxFieldElement]s which we cannot enqueue.
         // Also [CLOSURE] contains [LocalFunctionElement] which we cannot
         // enqueue.
         LocalFunctionElement closure = staticUse.element;
         if (closure.type.containsTypeVariables) {
           universe.closuresWithFreeTypeVariables.add(closure);
         }
         addElement = false;
         break;
       case StaticUseKind.SUPER_FIELD_SET:
       case StaticUseKind.SUPER_TEAR_OFF:
       case StaticUseKind.GENERAL:
+      case StaticUseKind.DIRECT_USE:
         break;
       case StaticUseKind.CONSTRUCTOR_INVOKE:
       case StaticUseKind.CONST_CONSTRUCTOR_INVOKE:
         _registerInstantiatedType(staticUse.type,
             constructor: staticUse.element, globalDependency: false);
         break;
       case StaticUseKind.REDIRECTION:
         _registerInstantiatedType(staticUse.type,
             constructor: staticUse.element,
             globalDependency: false,
             isRedirection: true);
         break;
       case StaticUseKind.DIRECT_INVOKE:
         invariant(
             element, 'Direct static use is not supported for resolution.');
         break;
     }
     if (addElement) {
       addToWorkList(element);
     }
   }
 
-  void _registerTypeUse(TypeUse typeUse) {
+  void registerTypeUse(TypeUse typeUse) {
+    strategy.processTypeUse(this, typeUse);
+  }
+
+  void registerTypeUseInternal(TypeUse typeUse) {
     DartType type = typeUse.type;
     switch (typeUse.kind) {
       case TypeUseKind.INSTANTIATION:
         _registerInstantiatedType(type, globalDependency: false);
         break;
       case TypeUseKind.MIRROR_INSTANTIATION:
         _registerInstantiatedType(type,
             mirrorUsage: true, globalDependency: false);
         break;
       case TypeUseKind.NATIVE_INSTANTIATION:
@@ skipping 16 matching lines @@
   }
 
   void _registerIsCheck(DartType type) {
     type = _universe.registerIsCheck(type, resolution);
     // Even in checked mode, type annotations for return type and argument
     // types do not imply type checks, so there should never be a check
     // against the type variable of a typedef.
     assert(!type.isTypeVariable || !type.element.enclosingElement.isTypedef);
   }
 
-  void registerCallMethodWithFreeTypeVariables(Element element) {
-    backend.registerCallMethodWithFreeTypeVariables(element, this);
+  void _registerCallMethodWithFreeTypeVariables(Element element) {
+    applyImpact(backend.registerCallMethodWithFreeTypeVariables(element,
+        forResolution: true));
     _universe.callMethodsWithFreeTypeVariables.add(element);
   }
 
   void registerClosurizedMember(TypedElement element) {
     assert(element.isInstanceMember);
     if (element.computeType(resolution).containsTypeVariables) {
-      backend.registerClosureWithFreeTypeVariables(element, this);
+      applyImpact(backend.registerClosureWithFreeTypeVariables(element,
+          forResolution: true));
       _universe.closuresWithFreeTypeVariables.add(element);
     }
-    backend.registerBoundClosure(this);
+    applyImpact(backend.registerBoundClosure());
     _universe.closurizedMembers.add(element);
   }
 
   void forEach(void f(WorkItem work)) {
     do {
       while (queue.isNotEmpty) {
         // TODO(johnniwinther): Find an optimal process order.
-        filter.processWorkItem(f, queue.removeLast());
+        WorkItem work = queue.removeLast();
+        if (!isProcessed(work.element)) {
+          strategy.processWorkItem(f, work);
+          registerProcessedElement(work.element);
+        }
       }
       List recents = recentClasses.toList(growable: false);
       recentClasses.clear();
       if (!onQueueEmpty(recents)) recentClasses.addAll(recents);
     } while (queue.isNotEmpty || recentClasses.isNotEmpty);
   }
 
   void logSummary(log(message)) {
     log('Resolved ${processedElements.length} elements.');
     nativeEnqueuer.logSummary(log);
@@ skipping 71 matching lines @@
       }
     }
 
     if (element.isGetter && element.name == Identifiers.runtimeType_) {
       // Enable runtime type support if we discover a getter called runtimeType.
       // We have to enable runtime type before hitting the codegen, so
       // that constructors know whether they need to generate code for
       // runtime type.
       _universe.hasRuntimeTypeSupport = true;
       // TODO(ahe): Record precise dependency here.
-      backend.registerRuntimeType(this);
+      applyImpact(backend.registerRuntimeType());
     } else if (commonElements.isFunctionApplyMethod(element)) {
       _universe.hasFunctionApplySupport = true;
     }
 
     return true;
   }
 
   void registerNoSuchMethod(Element element) {
     backend.registerNoSuchMethod(element);
   }
 
   void enableIsolateSupport() {
     _universe.hasIsolateSupport = true;
-    backend.enableIsolateSupport(this);
+    applyImpact(backend.enableIsolateSupport(forResolution: true));
   }
 
   /**
    * Adds an action to the deferred task queue.
    *
    * The action is performed the next time the resolution queue has been
    * emptied.
    *
    * The queue is processed in FIFO order.
    */
@@ skipping 30 matching lines @@
 
   void forgetElement(Element element, Compiler compiler) {
     _universe.forgetElement(element, compiler);
     _processedClasses.remove(element);
     instanceMembersByName[element.name]?.remove(element);
     instanceFunctionsByName[element.name]?.remove(element);
     processedElements.remove(element);
   }
 }
 
-/// Parameterizes filtering of which work items are enqueued.
-class QueueFilter {
-  bool checkNoEnqueuedInvokedInstanceMethods(Enqueuer enqueuer) {
+void removeFromSet(Map<String, Set<Element>> map, Element element) {
+  Set<Element> set = map[element.name];
+  if (set == null) return;
+  set.remove(element);
+}
+
+/// Strategy used by the enqueuer to populate the world.
+class EnqueuerStrategy {
+  const EnqueuerStrategy();
+
+  /// Process a class instantiated in live code.
+  void processInstantiatedClass(EnqueuerImpl enqueuer, ClassElement cls) {}
+
+  /// Process a static use of and element in live code.
+  void processStaticUse(EnqueuerImpl enqueuer, StaticUse staticUse) {}
+
+  /// Process a type use in live code.
+  void processTypeUse(EnqueuerImpl enqueuer, TypeUse typeUse) {}
+
+  /// Process a dynamic use for a call site in live code.
+  void processDynamicUse(EnqueuerImpl enqueuer, DynamicUse dynamicUse) {}
+
+  /// Check enqueuer consistency after the queue has been closed.
+  bool checkEnqueuerConsistency(EnqueuerImpl enqueuer) {
     enqueuer.task.measure(() {
-      // Run through the classes and see if we need to compile methods.
+      // Run through the classes and see if we need to enqueue more methods.
       for (ClassElement classElement
           in enqueuer.universe.directlyInstantiatedClasses) {
         for (ClassElement currentClass = classElement;
             currentClass != null;
             currentClass = currentClass.superclass) {
           enqueuer.processInstantiatedClassMembers(currentClass);
         }
       }
     });
     return true;
   }
 
+  /// Process [work] using [f].
   void processWorkItem(void f(WorkItem work), WorkItem work) {
     f(work);
   }
 }
 
-void removeFromSet(Map<String, Set<Element>> map, Element element) {
-  Set<Element> set = map[element.name];
-  if (set == null) return;
-  set.remove(element);
+/// Strategy that only enqueues directly used elements.
+class DirectEnqueuerStrategy extends EnqueuerStrategy {
+  const DirectEnqueuerStrategy();
+  void processStaticUse(EnqueuerImpl enqueuer, StaticUse staticUse) {
+    if (staticUse.kind == StaticUseKind.DIRECT_USE) {
+      enqueuer.registerStaticUseInternal(staticUse);
+    }
+  }
 }
 
-/// Strategy used by the enqueuer to populate the world.
-// TODO(johnniwinther): Merge this interface with [QueueFilter].
-class EnqueuerStrategy {
-  const EnqueuerStrategy();
-
-  /// Process a class instantiated in live code.
-  void processInstantiatedClass(Enqueuer enqueuer, ClassElement cls) {}
-
-  /// Process a static use of and element in live code.
-  void processStaticUse(Enqueuer enqueuer, StaticUse staticUse) {}
-
-  /// Process a dynamic use for a call site in live code.
-  void processDynamicUse(Enqueuer enqueuer, DynamicUse dynamicUse) {}
-}
-
-class TreeShakingEnqueuerStrategy implements EnqueuerStrategy {
+/// Strategy used for tree-shaking.
+class TreeShakingEnqueuerStrategy extends EnqueuerStrategy {
   const TreeShakingEnqueuerStrategy();
 
   @override
-  void processInstantiatedClass(Enqueuer enqueuer, ClassElement cls) {
+  void processInstantiatedClass(EnqueuerImpl enqueuer, ClassElement cls) {
     cls.implementation.forEachMember(enqueuer.processInstantiatedClassMember);
   }
 
   @override
-  void processStaticUse(Enqueuer enqueuer, StaticUse staticUse) {
+  void processStaticUse(EnqueuerImpl enqueuer, StaticUse staticUse) {
     enqueuer.registerStaticUseInternal(staticUse);
   }
 
   @override
-  void processDynamicUse(Enqueuer enqueuer, DynamicUse dynamicUse) {
+  void processTypeUse(EnqueuerImpl enqueuer, TypeUse typeUse) {
+    enqueuer.registerTypeUseInternal(typeUse);
+  }
+
+  @override
+  void processDynamicUse(EnqueuerImpl enqueuer, DynamicUse dynamicUse) {
     enqueuer.handleUnseenSelectorInternal(dynamicUse);
   }
 }
 
-class _EnqueuerImpactVisitor implements WorldImpactVisitor {
-  final ResolutionEnqueuer enqueuer;
+class EnqueuerImplImpactVisitor implements WorldImpactVisitor {
+  final EnqueuerImpl enqueuer;
 
-  _EnqueuerImpactVisitor(this.enqueuer);
+  EnqueuerImplImpactVisitor(this.enqueuer);
 
   @override
   void visitDynamicUse(DynamicUse dynamicUse) {
     enqueuer.registerDynamicUse(dynamicUse);
   }
 
   @override
   void visitStaticUse(StaticUse staticUse) {
     enqueuer.registerStaticUse(staticUse);
   }
 
   @override
   void visitTypeUse(TypeUse typeUse) {
-    enqueuer._registerTypeUse(typeUse);
+    enqueuer.registerTypeUse(typeUse);
   }
 }
 
 typedef void _DeferredActionFunction();
 
 class _DeferredAction {
   final Element element;
   final _DeferredActionFunction action;
 
   _DeferredAction(this.element, this.action);
 }