Start moving the JavaScript backend related code into a separate library

lib/compiler/implementation/js_backend/backend.dart

Index: lib/compiler/implementation/js_backend/backend.dart
diff --git a/lib/compiler/implementation/js_backend/backend.dart b/lib/compiler/implementation/js_backend/backend.dart
new file mode 100644
index 0000000000000000000000000000000000000000..3984bc0de12611a125c84003c06dbdb63b1f8810
--- /dev/null
+++ b/lib/compiler/implementation/js_backend/backend.dart
@@ -0,0 +1,273 @@
+// 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.
+
+class InvocationInfo {
+  int parameterCount;
+  List<HType> providedTypes;
+  List<Element> compiledFunctions;
+
+  InvocationInfo(List<HType> types)
+      : parameterCount = types != null ? types.length : -1,
+        providedTypes = types,
+        compiledFunctions = new List<Element>();
+
+  addCompiledFunction(FunctionElement function) =>
+      compiledFunctions.add(function);
+
+  void clearTypeInformation() => providedTypes = null;
+  bool get hasTypeInformation() => providedTypes != null;
+
+}
+
+class JavaScriptBackend extends Backend {
+  SsaBuilderTask builder;
+  SsaOptimizerTask optimizer;
+  SsaCodeGeneratorTask generator;
+  CodeEmitterTask emitter;
+  final Map<Element, Map<Element, HType>> fieldInitializers;
+  final Map<Element, Map<Element, HType>> fieldConstructorSetters;
+  final Map<Element, Map<Element, HType>> fieldSettersType;
+
+  final Map<SourceString, Map<Selector, InvocationInfo>> invocationInfo;
+
+  List<CompilerTask> get tasks() {
+    return <CompilerTask>[builder, optimizer, generator, emitter];
+  }
+
+  JavaScriptBackend(Compiler compiler, bool generateSourceMap)
+      : emitter = new CodeEmitterTask(compiler, generateSourceMap),
+        fieldInitializers = new Map<Element, Map<Element, HType>>(),
+        fieldConstructorSetters = new Map<Element, Map<Element, HType>>(),
+        fieldSettersType = new Map<Element, Map<Element, HType>>(),
+        invocationInfo = new Map<SourceString, Map<Selector, InvocationInfo>>(),
+        super(compiler) {
+    builder = new SsaBuilderTask(this);
+    optimizer = new SsaOptimizerTask(this);
+    generator = new SsaCodeGeneratorTask(this);
+  }
+
+  void enqueueHelpers(Enqueuer world) {
+    enqueueAllTopLevelFunctions(compiler.jsHelperLibrary, world);
+    enqueueAllTopLevelFunctions(compiler.interceptorsLibrary, world);
+    for (var helper in [const SourceString('Closure'),
+                        const SourceString('ConstantMap'),
+                        const SourceString('ConstantProtoMap')]) {
+      var e = compiler.findHelper(helper);
+      if (e !== null) world.registerInstantiatedClass(e);
+    }
+  }
+
+  CodeBuffer codegen(WorkItem work) {
+    HGraph graph = builder.build(work);
+    optimizer.optimize(work, graph);
+    if (work.allowSpeculativeOptimization
+        && optimizer.trySpeculativeOptimizations(work, graph)) {
+      CodeBuffer codeBuffer = generator.generateBailoutMethod(work, graph);
+      compiler.codegenWorld.addBailoutCode(work, codeBuffer);
+      optimizer.prepareForSpeculativeOptimizations(work, graph);
+      optimizer.optimize(work, graph);
+    }
+    return generator.generateMethod(work, graph);
+  }
+
+  void processNativeClasses(Enqueuer world,
+                            Collection<LibraryElement> libraries) {
+    native.processNativeClasses(world, emitter, libraries);
+  }
+
+  void assembleProgram() {
+    emitter.assembleProgram();
+  }
+
+  void updateFieldInitializers(Element field, HType propagatedType) {
+    assert(field.isField());
+    assert(field.isMember());
+    Map<Element, HType> fields =
+        fieldInitializers.putIfAbsent(
+          field.getEnclosingClass(), () => new Map<Element, HType>());
+    if (!fields.containsKey(field)) {
+      fields[field] = propagatedType;
+    } else {
+      fields[field] = fields[field].union(propagatedType);
+    }
+  }
+
+  HType typeFromInitializersSoFar(Element field) {
+    assert(field.isField());
+    assert(field.isMember());
+    if (!fieldInitializers.containsKey(field.getEnclosingClass())) {
+      return HType.CONFLICTING;
+    }
+    Map<Element, HType> fields = fieldInitializers[field.getEnclosingClass()];
+    return fields[field];
+  }
+
+  void updateFieldConstructorSetters(Element field, HType type) {
+    assert(field.isField());
+    assert(field.isMember());
+    Map<Element, HType> fields =
+        fieldConstructorSetters.putIfAbsent(
+            field.getEnclosingClass(), () => new Map<Element, HType>());
+    if (!fields.containsKey(field)) {
+      fields[field] = type;
+    } else {
+      fields[field] = fields[field].union(type);
+    }
+  }
+
+  // Check if this field is set in the constructor body.
+  bool hasConstructorBodyFieldSetter(Element field) {
+    ClassElement enclosingClass = field.getEnclosingClass();
+    if (!fieldConstructorSetters.containsKey(enclosingClass)) {
+      return false;
+    }
+    return fieldConstructorSetters[enclosingClass][field] != null;
+  }
+
+  // Provide an optimistic estimate of the type of a field after construction.
+  // If the constructor body has setters for fields returns HType.UNKNOWN.
+  // This only takes the initializer lists and field assignments in the
+  // constructor body into account. The constructor body might have method calls
+  // that could alter the field.
+  HType optimisticFieldTypeAfterConstruction(Element field) {
+    assert(field.isField());
+    assert(field.isMember());
+
+    ClassElement classElement = field.getEnclosingClass();
+    if (hasConstructorBodyFieldSetter(field)) {
+      // If there are field setters but there is only constructor then the type
+      // of the field is determined by the assignments in the constructor
+      // body.
+      if (classElement.constructors.length == 1) {
+        return fieldConstructorSetters[classElement][field];
+      } else {
+        return HType.UNKNOWN;
+      }
+    } else if (fieldInitializers.containsKey(classElement)) {
+      HType type = fieldInitializers[classElement][field];
+      return type == null ? HType.CONFLICTING : type;
+    } else {
+      return HType.CONFLICTING;
+    }
+  }
+
+  void updateFieldSetters(Element field, HType type) {
+    assert(field.isField());
+    assert(field.isMember());
+    Map<Element, HType> fields =
+        fieldSettersType.putIfAbsent(
+          field.getEnclosingClass(), () => new Map<Element, HType>());
+    if (!fields.containsKey(field)) {
+      fields[field] = type;
+    } else {
+      fields[field] = fields[field].union(type);
+    }
+  }
+
+  // Returns the type that field setters are setting the field to based on what
+  // have been seen during compilation so far.
+  HType fieldSettersTypeSoFar(Element field) {
+    assert(field.isField());
+    assert(field.isMember());
+    ClassElement enclosingClass = field.getEnclosingClass();
+    if (!fieldSettersType.containsKey(enclosingClass)) {
+      return HType.CONFLICTING;
+    }
+    Map<Element, HType> fields = fieldSettersType[enclosingClass];
+    if (!fields.containsKey(field)) return HType.CONFLICTING;
+    return fields[field];
+  }
+
+  /**
+   *  Register a dynamic invocation and collect the provided types for the
+   *  named selector.
+   */
+  void registerDynamicInvocation(HInvokeDynamicMethod node, Selector selector) {
+    Map<Selector, InvocationInfo> invocationInfos =
+        invocationInfo.putIfAbsent(node.name,
+                                   () => new Map<Selector, InvocationInfo>());
+    InvocationInfo info = invocationInfos[selector];
+    if (info != null) {
+      // If we don't know anything useful about the types adding more
+      // information will not help.
+      if (!info.hasTypeInformation) return;
+
+      // Update the type information with the provided types.
+      bool typesChanged = false;
+      List<HType> types = info.providedTypes;
+      bool allUnknown = true;
+      for (int i = 0; i < types.length; i++) {
+        HType newType = types[i].union(node.inputs[i + 1].propagatedType);
+        if (newType != types[i]) {
+          typesChanged = true;
+          types[i] = newType;
+        }
+        if (types[i] != HType.UNKNOWN) allUnknown = false;
+      }
+      // If the provided types change we need to recompile all functions which
+      // have been compiled under the now invalidated assumptions.
+      if (typesChanged && info.compiledFunctions.length != 0) {
+        if (compiler.phase == Compiler.PHASE_COMPILING) {
+          info.compiledFunctions.forEach(
+              compiler.enqueuer.codegen.eagerRecompile);
+          info.compiledFunctions.clear();
+        }
+      }
+      // If all information is lost no need to keep it around.
+      if (allUnknown) info.clearTypeInformation();
+    } else {
+      // Gather the type information provided. If the types contains no useful
+      // information there is no need to actually store them.
+      bool allUnknown = true;
+      for (int i = 1; i < node.inputs.length; i++) {
+        if (node.inputs[i].propagatedType != HType.UNKNOWN) {
+          allUnknown = false;
+          break;
+        }
+      }
+      List<HType> types = null;
+      if (!allUnknown) {
+        types = new List<HType>(node.inputs.length - 1);
+        for (int i = 0; i < types.length; i++) {
+          types[i] = node.inputs[i + 1].propagatedType;
+        }
+      }
+      InvocationInfo info = new InvocationInfo(types);
+      invocationInfos[selector] = info;
+    }
+  }
+
+  /**
+   * Retreive the types of the parameters used for calling the [element]
+   * function. The types are optimistic in the sense as they are based on the
+   * possible invocations of the function seen so far. As compiling more
+   * code can invalidate this asumption the function is registered for being
+   * re-compiled if new possible invocations of this function invalidate these
+   * asumptions.
+   */
+  List<HType> optimisticParameterTypesWithRecompilationOnTypeChange(
+      FunctionElement element) {
+    Map<Selector, InvocationInfo> invocationInfos =
+        invocationInfo[element.name];
+    if (invocationInfos == null) return null;
+
+    int foundCount = 0;
+    InvocationInfo found = null;
+    invocationInfos.forEach((Selector selector, InvocationInfo info) {
+      if (selector.applies(element, compiler)) {
+        found = info;
+        foundCount++;
+      }
+    });
+
+    if (foundCount == 1 && found.hasTypeInformation) {
+      FunctionSignature signature = element.computeSignature(compiler);
+      if (signature.parameterCount == found.parameterCount) {
+        found.addCompiledFunction(element);
+        return found.providedTypes;
+      }
+    }
+    return null;
+  }
+}