Make LocalsHandler depend on GraphBuilder instead of SsaBuilder.

pkg/compiler/lib/src/ssa/builder.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.
 
 import 'dart:collection';
 
 import 'package:js_runtime/shared/embedded_names.dart';
 
 import '../closure.dart';
 import '../common.dart';
@@ skipping 21 matching lines @@
 import '../resolution/tree_elements.dart' show TreeElements;
 import '../tree/tree.dart' as ast;
 import '../types/types.dart';
 import '../universe/call_structure.dart' show CallStructure;
 import '../universe/selector.dart' show Selector;
 import '../universe/side_effects.dart' show SideEffects;
 import '../universe/use.dart' show DynamicUse, StaticUse, TypeUse;
 import '../util/util.dart';
 import '../world.dart' show ClassWorld;
 import 'graph_builder.dart';
+import 'locals_handler.dart';
 import 'nodes.dart';
 import 'optimize.dart';
 import 'types.dart';
 
 /// A synthetic local variable only used with the SSA graph.
 ///
 /// For instance used for holding return value of function or the exception of a
 /// try-catch statement.
 class SyntheticLocal extends Local {
   final String name;
@@ skipping 64 matching lines @@
           }
           compiler.tracer.traceCompilation(name, work.compilationContext);
           compiler.tracer.traceGraph('builder', graph);
         }
         return graph;
       });
     });
   }
 }
 
-/**
- * Keeps track of locals (including parameters and phis) when building. The
- * 'this' reference is treated as parameter and hence handled by this class,
- * too.
- */
-class LocalsHandler {
-  /**
-   * The values of locals that can be directly accessed (without redirections
-   * to boxes or closure-fields).
-   *
-   * [directLocals] is iterated, so it is "insertion ordered" to make the
-   * iteration order a function only of insertions and not a function of
-   * e.g. Element hash codes.  I'd prefer to use a SortedMap but some elements
-   * don't have source locations for [Elements.compareByPosition].
-   */
-  Map<Local, HInstruction> directLocals = new Map<Local, HInstruction>();
-  Map<Local, CapturedVariable> redirectionMapping =
-      new Map<Local, CapturedVariable>();
-  SsaBuilder builder;
-  ClosureClassMap closureData;
-  Map<TypeVariableType, TypeVariableLocal> typeVariableLocals =
-      new Map<TypeVariableType, TypeVariableLocal>();
-  final ExecutableElement executableContext;
-
-  /// The class that defines the current type environment or null if no type
-  /// variables are in scope.
-  ClassElement get contextClass => executableContext.contextClass;
-
-  /// The type of the current instance, if concrete.
-  ///
-  /// This allows for handling fixed type argument in case of inlining. For
-  /// instance, checking `'foo'` against `String` instead of `T` in `main`:
-  ///
-  ///     class Foo<T> {
-  ///       T field;
-  ///       Foo(this.field);
-  ///     }
-  ///     main() {
-  ///       new Foo<String>('foo');
-  ///     }
-  ///
-  /// [instanceType] is not used if it contains type variables, since these
-  /// might not be in scope or from the current instance.
-  ///
-  final InterfaceType instanceType;
-
-  SourceInformationBuilder get sourceInformationBuilder {
-    return builder.sourceInformationBuilder;
-  }
-
-  LocalsHandler(
-      this.builder, this.executableContext, InterfaceType instanceType)
-      : this.instanceType = instanceType == null ||
-            instanceType.containsTypeVariables ? null : instanceType;
-
-  /// Substituted type variables occurring in [type] into the context of
-  /// [contextClass].
-  DartType substInContext(DartType type) {
-    if (contextClass != null) {
-      ClassElement typeContext = Types.getClassContext(type);
-      if (typeContext != null) {
-        type = type.substByContext(contextClass.asInstanceOf(typeContext));
-      }
-    }
-    if (instanceType != null) {
-      type = type.substByContext(instanceType);
-    }
-    return type;
-  }
-
-  get typesTask => builder.compiler.typesTask;
-
-  /**
-   * Creates a new [LocalsHandler] based on [other]. We only need to
-   * copy the [directLocals], since the other fields can be shared
-   * throughout the AST visit.
-   */
-  LocalsHandler.from(LocalsHandler other)
-      : directLocals = new Map<Local, HInstruction>.from(other.directLocals),
-        redirectionMapping = other.redirectionMapping,
-        executableContext = other.executableContext,
-        instanceType = other.instanceType,
-        builder = other.builder,
-        closureData = other.closureData;
-
-  /**
-   * Redirects accesses from element [from] to element [to]. The [to] element
-   * must be a boxed variable or a variable that is stored in a closure-field.
-   */
-  void redirectElement(Local from, CapturedVariable to) {
-    assert(redirectionMapping[from] == null);
-    redirectionMapping[from] = to;
-    assert(isStoredInClosureField(from) || isBoxed(from));
-  }
-
-  HInstruction createBox() {
-    // TODO(floitsch): Clean up this hack. Should we create a box-object by
-    // just creating an empty object literal?
-    JavaScriptBackend backend = builder.backend;
-    HInstruction box = new HForeignCode(
-        js.js.parseForeignJS('{}'), backend.nonNullType, <HInstruction>[],
-        nativeBehavior: native.NativeBehavior.PURE_ALLOCATION);
-    builder.add(box);
-    return box;
-  }
-
-  /**
-   * If the scope (function or loop) [node] has captured variables then this
-   * method creates a box and sets up the redirections.
-   */
-  void enterScope(ast.Node node, Element element) {
-    // See if any variable in the top-scope of the function is captured. If yes
-    // we need to create a box-object.
-    ClosureScope scopeData = closureData.capturingScopes[node];
-    if (scopeData == null) return;
-    HInstruction box;
-    // The scope has captured variables.
-    if (element != null && element.isGenerativeConstructorBody) {
-      // The box is passed as a parameter to a generative
-      // constructor body.
-      JavaScriptBackend backend = builder.backend;
-      box = builder.addParameter(scopeData.boxElement, backend.nonNullType);
-    } else {
-      box = createBox();
-    }
-    // Add the box to the known locals.
-    directLocals[scopeData.boxElement] = box;
-    // Make sure that accesses to the boxed locals go into the box. We also
-    // need to make sure that parameters are copied into the box if necessary.
-    scopeData.forEachCapturedVariable(
-        (LocalVariableElement from, BoxFieldElement to) {
-      // The [from] can only be a parameter for function-scopes and not
-      // loop scopes.
-      if (from.isRegularParameter && !element.isGenerativeConstructorBody) {
-        // Now that the redirection is set up, the update to the local will
-        // write the parameter value into the box.
-        // Store the captured parameter in the box. Get the current value
-        // before we put the redirection in place.
-        // We don't need to update the local for a generative
-        // constructor body, because it receives a box that already
-        // contains the updates as the last parameter.
-        HInstruction instruction = readLocal(from);
-        redirectElement(from, to);
-        updateLocal(from, instruction);
-      } else {
-        redirectElement(from, to);
-      }
-    });
-  }
-
-  /**
-   * Replaces the current box with a new box and copies over the given list
-   * of elements from the old box into the new box.
-   */
-  void updateCaptureBox(
-      BoxLocal boxElement, List<LocalVariableElement> toBeCopiedElements) {
-    // Create a new box and copy over the values from the old box into the
-    // new one.
-    HInstruction oldBox = readLocal(boxElement);
-    HInstruction newBox = createBox();
-    for (LocalVariableElement boxedVariable in toBeCopiedElements) {
-      // [readLocal] uses the [boxElement] to find its box. By replacing it
-      // behind its back we can still get to the old values.
-      updateLocal(boxElement, oldBox);
-      HInstruction oldValue = readLocal(boxedVariable);
-      updateLocal(boxElement, newBox);
-      updateLocal(boxedVariable, oldValue);
-    }
-    updateLocal(boxElement, newBox);
-  }
-
-  /**
-   * Documentation wanted -- johnniwinther
-   *
-   * Invariant: [function] must be an implementation element.
-   */
-  void startFunction(AstElement element, ast.Node node) {
-    assert(invariant(element, element.isImplementation));
-    Compiler compiler = builder.compiler;
-    closureData = compiler.closureToClassMapper
-        .computeClosureToClassMapping(element.resolvedAst);
-
-    if (element is FunctionElement) {
-      FunctionElement functionElement = element;
-      FunctionSignature params = functionElement.functionSignature;
-      ClosureScope scopeData = closureData.capturingScopes[node];
-      params.orderedForEachParameter((ParameterElement parameterElement) {
-        if (element.isGenerativeConstructorBody) {
-          if (scopeData != null &&
-              scopeData.isCapturedVariable(parameterElement)) {
-            // The parameter will be a field in the box passed as the
-            // last parameter. So no need to have it.
-            return;
-          }
-        }
-        HInstruction parameter = builder.addParameter(parameterElement,
-            TypeMaskFactory.inferredTypeForElement(parameterElement, compiler));
-        builder.parameters[parameterElement] = parameter;
-        directLocals[parameterElement] = parameter;
-      });
-    }
-
-    enterScope(node, element);
-
-    // If the freeVariableMapping is not empty, then this function was a
-    // nested closure that captures variables. Redirect the captured
-    // variables to fields in the closure.
-    closureData.forEachFreeVariable((Local from, CapturedVariable to) {
-      redirectElement(from, to);
-    });
-    JavaScriptBackend backend = compiler.backend;
-    if (closureData.isClosure) {
-      // Inside closure redirect references to itself to [:this:].
-      HThis thisInstruction =
-          new HThis(closureData.thisLocal, backend.nonNullType);
-      builder.graph.thisInstruction = thisInstruction;
-      builder.graph.entry.addAtEntry(thisInstruction);
-      updateLocal(closureData.closureElement, thisInstruction);
-    } else if (element.isInstanceMember) {
-      // Once closures have been mapped to classes their instance members might
-      // not have any thisElement if the closure was created inside a static
-      // context.
-      HThis thisInstruction =
-          new HThis(closureData.thisLocal, builder.getTypeOfThis());
-      builder.graph.thisInstruction = thisInstruction;
-      builder.graph.entry.addAtEntry(thisInstruction);
-      directLocals[closureData.thisLocal] = thisInstruction;
-    }
-
-    // If this method is an intercepted method, add the extra
-    // parameter to it, that is the actual receiver for intercepted
-    // classes, or the same as [:this:] for non-intercepted classes.
-    ClassElement cls = element.enclosingClass;
-
-    // When the class extends a native class, the instance is pre-constructed
-    // and passed to the generative constructor factory function as a parameter.
-    // Instead of allocating and initializing the object, the constructor
-    // 'upgrades' the native subclass object by initializing the Dart fields.
-    bool isNativeUpgradeFactory =
-        element.isGenerativeConstructor && backend.isNativeOrExtendsNative(cls);
-    if (backend.isInterceptedMethod(element)) {
-      bool isInterceptorClass = backend.isInterceptorClass(cls.declaration);
-      String name = isInterceptorClass ? 'receiver' : '_';
-      SyntheticLocal parameter = new SyntheticLocal(name, executableContext);
-      HParameterValue value =
-          new HParameterValue(parameter, builder.getTypeOfThis());
-      builder.graph.explicitReceiverParameter = value;
-      builder.graph.entry.addAfter(directLocals[closureData.thisLocal], value);
-      if (builder.lastAddedParameter == null) {
-        // If this is the first parameter inserted, make sure it stays first.
-        builder.lastAddedParameter = value;
-      }
-      if (isInterceptorClass) {
-        // Only use the extra parameter in intercepted classes.
-        directLocals[closureData.thisLocal] = value;
-      }
-    } else if (isNativeUpgradeFactory) {
-      SyntheticLocal parameter =
-          new SyntheticLocal('receiver', executableContext);
-      // Unlike `this`, receiver is nullable since direct calls to generative
-      // constructor call the constructor with `null`.
-      ClassWorld classWorld = compiler.world;
-      HParameterValue value =
-          new HParameterValue(parameter, new TypeMask.exact(cls, classWorld));
-      builder.graph.explicitReceiverParameter = value;
-      builder.graph.entry.addAtEntry(value);
-    }
-  }
-
-  /**
-   * Returns true if the local can be accessed directly. Boxed variables or
-   * captured variables that are stored in the closure-field return [:false:].
-   */
-  bool isAccessedDirectly(Local local) {
-    assert(local != null);
-    return !redirectionMapping.containsKey(local) &&
-        !closureData.variablesUsedInTryOrGenerator.contains(local);
-  }
-
-  bool isStoredInClosureField(Local local) {
-    assert(local != null);
-    if (isAccessedDirectly(local)) return false;
-    CapturedVariable redirectTarget = redirectionMapping[local];
-    if (redirectTarget == null) return false;
-    return redirectTarget is ClosureFieldElement;
-  }
-
-  bool isBoxed(Local local) {
-    if (isAccessedDirectly(local)) return false;
-    if (isStoredInClosureField(local)) return false;
-    return redirectionMapping.containsKey(local);
-  }
-
-  bool isUsedInTryOrGenerator(Local local) {
-    return closureData.variablesUsedInTryOrGenerator.contains(local);
-  }
-
-  /**
-   * Returns an [HInstruction] for the given element. If the element is
-   * boxed or stored in a closure then the method generates code to retrieve
-   * the value.
-   */
-  HInstruction readLocal(Local local, {SourceInformation sourceInformation}) {
-    if (isAccessedDirectly(local)) {
-      if (directLocals[local] == null) {
-        if (local is TypeVariableElement) {
-          builder.reporter.internalError(builder.compiler.currentElement,
-              "Runtime type information not available for $local.");
-        } else {
-          builder.reporter.internalError(
-              local, "Cannot find value $local in ${directLocals.keys}.");
-        }
-      }
-      HInstruction value = directLocals[local];
-      if (sourceInformation != null) {
-        value = new HRef(value, sourceInformation);
-        builder.add(value);
-      }
-      return value;
-    } else if (isStoredInClosureField(local)) {
-      ClosureFieldElement redirect = redirectionMapping[local];
-      HInstruction receiver = readLocal(closureData.closureElement);
-      TypeMask type = local is BoxLocal
-          ? builder.backend.nonNullType
-          : builder.getTypeOfCapturedVariable(redirect);
-      HInstruction fieldGet = new HFieldGet(redirect, receiver, type);
-      builder.add(fieldGet);
-      return fieldGet..sourceInformation = sourceInformation;
-    } else if (isBoxed(local)) {
-      BoxFieldElement redirect = redirectionMapping[local];
-      // In the function that declares the captured variable the box is
-      // accessed as direct local. Inside the nested closure the box is
-      // accessed through a closure-field.
-      // Calling [readLocal] makes sure we generate the correct code to get
-      // the box.
-      HInstruction box = readLocal(redirect.box);
-      HInstruction lookup = new HFieldGet(
-          redirect, box, builder.getTypeOfCapturedVariable(redirect));
-      builder.add(lookup);
-      return lookup..sourceInformation = sourceInformation;
-    } else {
-      assert(isUsedInTryOrGenerator(local));
-      HLocalValue localValue = getLocal(local);
-      HInstruction instruction = new HLocalGet(
-          local, localValue, builder.backend.dynamicType, sourceInformation);
-      builder.add(instruction);
-      return instruction;
-    }
-  }
-
-  HInstruction readThis() {
-    HInstruction res = readLocal(closureData.thisLocal);
-    if (res.instructionType == null) {
-      res.instructionType = builder.getTypeOfThis();
-    }
-    return res;
-  }
-
-  HLocalValue getLocal(Local local, {SourceInformation sourceInformation}) {
-    // If the element is a parameter, we already have a
-    // HParameterValue for it. We cannot create another one because
-    // it could then have another name than the real parameter. And
-    // the other one would not know it is just a copy of the real
-    // parameter.
-    if (local is ParameterElement) {
-      assert(invariant(local, builder.parameters.containsKey(local),
-          message: "No local value for parameter $local in "
-              "${builder.parameters}."));
-      return builder.parameters[local];
-    }
-
-    return builder.activationVariables.putIfAbsent(local, () {
-      JavaScriptBackend backend = builder.backend;
-      HLocalValue localValue = new HLocalValue(local, backend.nonNullType)
-        ..sourceInformation = sourceInformation;
-      builder.graph.entry.addAtExit(localValue);
-      return localValue;
-    });
-  }
-
-  Local getTypeVariableAsLocal(TypeVariableType type) {
-    return typeVariableLocals.putIfAbsent(type, () {
-      return new TypeVariableLocal(type, executableContext);
-    });
-  }
-
-  /**
-   * Sets the [element] to [value]. If the element is boxed or stored in a
-   * closure then the method generates code to set the value.
-   */
-  void updateLocal(Local local, HInstruction value,
-      {SourceInformation sourceInformation}) {
-    if (value is HRef) {
-      HRef ref = value;
-      value = ref.value;
-    }
-    assert(!isStoredInClosureField(local));
-    if (isAccessedDirectly(local)) {
-      directLocals[local] = value;
-    } else if (isBoxed(local)) {
-      BoxFieldElement redirect = redirectionMapping[local];
-      // The box itself could be captured, or be local. A local variable that
-      // is captured will be boxed, but the box itself will be a local.
-      // Inside the closure the box is stored in a closure-field and cannot
-      // be accessed directly.
-      HInstruction box = readLocal(redirect.box);
-      builder.add(new HFieldSet(redirect, box, value)
-        ..sourceInformation = sourceInformation);
-    } else {
-      assert(isUsedInTryOrGenerator(local));
-      HLocalValue localValue = getLocal(local);
-      builder.add(new HLocalSet(local, localValue, value)
-        ..sourceInformation = sourceInformation);
-    }
-  }
-
-  /**
-   * This function, startLoop, must be called before visiting any children of
-   * the loop. In particular it needs to be called before executing the
-   * initializers.
-   *
-   * The [LocalsHandler] will make the boxes and updates at the right moment.
-   * The builder just needs to call [enterLoopBody] and [enterLoopUpdates]
-   * (for [ast.For] loops) at the correct places. For phi-handling
-   * [beginLoopHeader] and [endLoop] must also be called.
-   *
-   * The correct place for the box depends on the given loop. In most cases
-   * the box will be created when entering the loop-body: while, do-while, and
-   * for-in (assuming the call to [:next:] is inside the body) can always be
-   * constructed this way.
-   *
-   * Things are slightly more complicated for [ast.For] loops. If no declared
-   * loop variable is boxed then the loop-body approach works here too. If a
-   * loop-variable is boxed we need to introduce a new box for the
-   * loop-variable before we enter the initializer so that the initializer
-   * writes the values into the box. In any case we need to create the box
-   * before the condition since the condition could box the variable.
-   * Since the first box is created outside the actual loop we have a second
-   * location where a box is created: just before the updates. This is
-   * necessary since updates are considered to be part of the next iteration
-   * (and can again capture variables).
-   *
-   * For example the following Dart code prints 1 3 -- 3 4.
-   *
-   *     var fs = [];
-   *     for (var i = 0; i < 3; (f() { fs.add(f); print(i); i++; })()) {
-   *       i++;
-   *     }
-   *     print("--");
-   *     for (var i = 0; i < 2; i++) fs[i]();
-   *
-   * We solve this by emitting the following code (only for [ast.For] loops):
-   *  <Create box>    <== move the first box creation outside the loop.
-   *  <initializer>;
-   *  loop-entry:
-   *    if (!<condition>) goto loop-exit;
-   *    <body>
-   *    <update box>  // create a new box and copy the captured loop-variables.
-   *    <updates>
-   *    goto loop-entry;
-   *  loop-exit:
-   */
-  void startLoop(ast.Node node) {
-    ClosureScope scopeData = closureData.capturingScopes[node];
-    if (scopeData == null) return;
-    if (scopeData.hasBoxedLoopVariables()) {
-      // If there are boxed loop variables then we set up the box and
-      // redirections already now. This way the initializer can write its
-      // values into the box.
-      // For other loops the box will be created when entering the body.
-      enterScope(node, null);
-    }
-  }
-
-  /**
-   * Create phis at the loop entry for local variables (ready for the values
-   * from the back edge).  Populate the phis with the current values.
-   */
-  void beginLoopHeader(HBasicBlock loopEntry) {
-    // Create a copy because we modify the map while iterating over it.
-    Map<Local, HInstruction> savedDirectLocals =
-        new Map<Local, HInstruction>.from(directLocals);
-
-    JavaScriptBackend backend = builder.backend;
-    // Create phis for all elements in the definitions environment.
-    savedDirectLocals.forEach((Local local, HInstruction instruction) {
-      if (isAccessedDirectly(local)) {
-        // We know 'this' cannot be modified.
-        if (local != closureData.thisLocal) {
-          HPhi phi =
-              new HPhi.singleInput(local, instruction, backend.dynamicType);
-          loopEntry.addPhi(phi);
-          directLocals[local] = phi;
-        } else {
-          directLocals[local] = instruction;
-        }
-      }
-    });
-  }
-
-  void enterLoopBody(ast.Node node) {
-    ClosureScope scopeData = closureData.capturingScopes[node];
-    if (scopeData == null) return;
-    // If there are no declared boxed loop variables then we did not create the
-    // box before the initializer and we have to create the box now.
-    if (!scopeData.hasBoxedLoopVariables()) {
-      enterScope(node, null);
-    }
-  }
-
-  void enterLoopUpdates(ast.Node node) {
-    // If there are declared boxed loop variables then the updates might have
-    // access to the box and we must switch to a new box before executing the
-    // updates.
-    // In all other cases a new box will be created when entering the body of
-    // the next iteration.
-    ClosureScope scopeData = closureData.capturingScopes[node];
-    if (scopeData == null) return;
-    if (scopeData.hasBoxedLoopVariables()) {
-      updateCaptureBox(scopeData.boxElement, scopeData.boxedLoopVariables);
-    }
-  }
-
-  /**
-   * Goes through the phis created in beginLoopHeader entry and adds the
-   * input from the back edge (from the current value of directLocals) to them.
-   */
-  void endLoop(HBasicBlock loopEntry) {
-    // If the loop has an aborting body, we don't update the loop
-    // phis.
-    if (loopEntry.predecessors.length == 1) return;
-    loopEntry.forEachPhi((HPhi phi) {
-      Local element = phi.sourceElement;
-      HInstruction postLoopDefinition = directLocals[element];
-      phi.addInput(postLoopDefinition);
-    });
-  }
-
-  /**
-   * Merge [otherLocals] into this locals handler, creating phi-nodes when
-   * there is a conflict.
-   * If a phi node is necessary, it will use this handler's instruction as the
-   * first input, and the otherLocals instruction as the second.
-   */
-  void mergeWith(LocalsHandler otherLocals, HBasicBlock joinBlock) {
-    // If an element is in one map but not the other we can safely
-    // ignore it. It means that a variable was declared in the
-    // block. Since variable declarations are scoped the declared
-    // variable cannot be alive outside the block. Note: this is only
-    // true for nodes where we do joins.
-    Map<Local, HInstruction> joinedLocals = new Map<Local, HInstruction>();
-    JavaScriptBackend backend = builder.backend;
-    otherLocals.directLocals.forEach((Local local, HInstruction instruction) {
-      // We know 'this' cannot be modified.
-      if (local == closureData.thisLocal) {
-        assert(directLocals[local] == instruction);
-        joinedLocals[local] = instruction;
-      } else {
-        HInstruction mine = directLocals[local];
-        if (mine == null) return;
-        if (identical(instruction, mine)) {
-          joinedLocals[local] = instruction;
-        } else {
-          HInstruction phi = new HPhi.manyInputs(
-              local, <HInstruction>[mine, instruction], backend.dynamicType);
-          joinBlock.addPhi(phi);
-          joinedLocals[local] = phi;
-        }
-      }
-    });
-    directLocals = joinedLocals;
-  }
-
-  /**
-   * When control flow merges, this method can be used to merge several
-   * localsHandlers into a new one using phis.  The new localsHandler is
-   * returned.  Unless it is also in the list, the current localsHandler is not
-   * used for its values, only for its declared variables. This is a way to
-   * exclude local values from the result when they are no longer in scope.
-   */
-  LocalsHandler mergeMultiple(
-      List<LocalsHandler> localsHandlers, HBasicBlock joinBlock) {
-    assert(localsHandlers.length > 0);
-    if (localsHandlers.length == 1) return localsHandlers[0];
-    Map<Local, HInstruction> joinedLocals = new Map<Local, HInstruction>();
-    HInstruction thisValue = null;
-    JavaScriptBackend backend = builder.backend;
-    directLocals.forEach((Local local, HInstruction instruction) {
-      if (local != closureData.thisLocal) {
-        HPhi phi = new HPhi.noInputs(local, backend.dynamicType);
-        joinedLocals[local] = phi;
-        joinBlock.addPhi(phi);
-      } else {
-        // We know that "this" never changes, if it's there.
-        // Save it for later. While merging, there is no phi for "this",
-        // so we don't have to special case it in the merge loop.
-        thisValue = instruction;
-      }
-    });
-    for (LocalsHandler handler in localsHandlers) {
-      handler.directLocals.forEach((Local local, HInstruction instruction) {
-        HPhi phi = joinedLocals[local];
-        if (phi != null) {
-          phi.addInput(instruction);
-        }
-      });
-    }
-    if (thisValue != null) {
-      // If there was a "this" for the scope, add it to the new locals.
-      joinedLocals[closureData.thisLocal] = thisValue;
-    }
-
-    // Remove locals that are not in all handlers.
-    directLocals = new Map<Local, HInstruction>();
-    joinedLocals.forEach((Local local, HInstruction instruction) {
-      if (local != closureData.thisLocal &&
-          instruction.inputs.length != localsHandlers.length) {
-        joinBlock.removePhi(instruction);
-      } else {
-        directLocals[local] = instruction;
-      }
-    });
-    return this;
-  }
-}
-
 // Represents a single break/continue instruction.
 class JumpHandlerEntry {
   final HJump jumpInstruction;
   final LocalsHandler locals;
   bool isBreak() => jumpInstruction is HBreak;
   bool isContinue() => jumpInstruction is HContinue;
   JumpHandlerEntry(this.jumpInstruction, this.locals);
 }
 
 abstract class JumpHandler {
@@ skipping 271 matching lines @@
   /**
    * This stack contains declaration elements of the functions being built
    * or inlined by this builder.
    */
   final List<Element> sourceElementStack = <Element>[];
 
   LocalsHandler localsHandler;
 
   HInstruction rethrowableException;
 
-  HParameterValue lastAddedParameter;
-
-  Map<ParameterElement, HInstruction> parameters =
-      <ParameterElement, HInstruction>{};
-
   Map<JumpTarget, JumpHandler> jumpTargets = <JumpTarget, JumpHandler>{};
 
-  /**
-   * Variables stored in the current activation. These variables are
-   * being updated in try/catch blocks, and should be
-   * accessed indirectly through [HLocalGet] and [HLocalSet].
-   */
-  Map<Local, HLocalValue> activationVariables = <Local, HLocalValue>{};
-
   // We build the Ssa graph by simulating a stack machine.
   List<HInstruction> stack = <HInstruction>[];
 
   /// Returns `true` if the current element is an `async` function.
   bool get isBuildingAsyncFunction {
     Element element = sourceElement;
     return (element is FunctionElement &&
         element.asyncMarker == AsyncMarker.ASYNC);
   }
 
   // TODO(sigmund): make most args optional
   SsaBuilder(
       this.target,
       this.resolvedAst,
       this.context,
       this.registry,
       JavaScriptBackend backend,
       this.nativeEmitter,
       SourceInformationStrategy sourceInformationFactory)
       : this.compiler = backend.compiler,
         this.infoReporter = backend.compiler.dumpInfoTask,
         this.backend = backend,
         this.constantSystem = backend.constantSystem,
         this.rti = backend.rti {
     assert(target.isImplementation);
     graph.element = target;
-    localsHandler = new LocalsHandler(this, target, null);
     sourceElementStack.add(target);
     sourceInformationBuilder =
         sourceInformationFactory.createBuilderForContext(resolvedAst);
     graph.sourceInformation =
         sourceInformationBuilder.buildVariableDeclaration();
+    localsHandler = new LocalsHandler(this, target, null, compiler);
   }
 
   BackendHelpers get helpers => backend.helpers;
 
   RuntimeTypesEncoder get rtiEncoder => backend.rtiEncoder;
 
   DiagnosticReporter get reporter => compiler.reporter;
 
   CoreClasses get coreClasses => compiler.coreClasses;
 
@@ skipping 382 matching lines @@
       sourceElementStack.add(element.declaration);
       var result = f();
       sourceInformationBuilder = oldSourceInformationBuilder;
       sourceElementStack.removeLast();
       return result;
     });
   }
 
   /**
    * Return null so it is simple to remove the optional parameters completely
-   * from interop methods to match JavaScript semantics for ommitted arguments.
+   * from interop methods to match JavaScript semantics for omitted arguments.
    */
   HInstruction handleConstantForOptionalParameterJsInterop(Element parameter) =>
       null;
 
   HInstruction handleConstantForOptionalParameter(ParameterElement parameter) {
     ConstantValue constantValue =
         backend.constants.getConstantValue(parameter.constant);
     assert(invariant(parameter, constantValue != null,
         message: 'No constant computed for $parameter'));
     return graph.addConstant(constantValue, compiler);
@@ skipping 29 matching lines @@
         backend.constants.getConstantValueForNode(node, elements);
     assert(invariant(node, constantValue != null,
         message: 'No constant computed for $node'));
     return constantValue;
   }
 
   HInstruction addConstant(ast.Node node) {
     return graph.addConstant(getConstantForNode(node), compiler);
   }
 
-  TypeMask cachedTypeOfThis;
-
-  TypeMask getTypeOfThis() {
-    TypeMask result = cachedTypeOfThis;
-    if (result == null) {
-      ThisLocal local = localsHandler.closureData.thisLocal;
-      ClassElement cls = local.enclosingClass;
-      ClassWorld classWorld = compiler.world;
-      if (classWorld.isUsedAsMixin(cls)) {
-        // If the enclosing class is used as a mixin, [:this:] can be
-        // of the class that mixins the enclosing class. These two
-        // classes do not have a subclass relationship, so, for
-        // simplicity, we mark the type as an interface type.
-        result = new TypeMask.nonNullSubtype(cls.declaration, compiler.world);
-      } else {
-        result = new TypeMask.nonNullSubclass(cls.declaration, compiler.world);
-      }
-      cachedTypeOfThis = result;
-    }
-    return result;
-  }
-
-  Map<Element, TypeMask> cachedTypesOfCapturedVariables =
-      new Map<Element, TypeMask>();
-
-  TypeMask getTypeOfCapturedVariable(Element element) {
-    assert(element.isField);
-    return cachedTypesOfCapturedVariables.putIfAbsent(element, () {
-      return TypeMaskFactory.inferredTypeForElement(element, compiler);
-    });
-  }
-
   /**
    * Documentation wanted -- johnniwinther
    *
    * Invariant: [functionElement] must be an implementation element.
    */
   HGraph buildMethod(FunctionElement functionElement) {
     assert(invariant(functionElement, functionElement.isImplementation));
     graph.calledInLoop = compiler.world.isCalledInLoop(functionElement);
     ast.FunctionExpression function = resolvedAst.node;
     assert(function != null);
@@ skipping 126 matching lines @@
         ConstructorBodyElementX origin = new ConstructorBodyElementX(
             constructorResolvedAst, constructor.origin);
         origin.applyPatch(patch);
         classElement.origin.addBackendMember(bodyElement.origin);
       }
     }
     assert(bodyElement.isGenerativeConstructorBody);
     return bodyElement;
   }
 
-  HParameterValue addParameter(Entity parameter, TypeMask type) {
-    assert(inliningStack.isEmpty);
-    HParameterValue result = new HParameterValue(parameter, type);
-    if (lastAddedParameter == null) {
-      graph.entry.addBefore(graph.entry.first, result);
-    } else {
-      graph.entry.addAfter(lastAddedParameter, result);
-    }
-    lastAddedParameter = result;
-    return result;
-  }
-
   /**
    * This method sets up the local state of the builder for inlining [function].
    * The arguments of the function are inserted into the [localsHandler].
    *
    * When inlining a function, [:return:] statements are not emitted as
    * [HReturn] instructions. Instead, the value of a synthetic element is
    * updated in the [localsHandler]. This function creates such an element and
    * stores it in the [returnLocal] field.
    */
   void setupStateForInlining(
       FunctionElement function, List<HInstruction> compiledArguments,
       {InterfaceType instanceType}) {
     ResolvedAst resolvedAst = function.resolvedAst;
     assert(resolvedAst != null);
-    localsHandler = new LocalsHandler(this, function, instanceType);
+    localsHandler = new LocalsHandler(this, function, instanceType, compiler);
     localsHandler.closureData =
         compiler.closureToClassMapper.computeClosureToClassMapping(resolvedAst);
     returnLocal = new SyntheticLocal("result", function);
     localsHandler.updateLocal(returnLocal, graph.addConstantNull(compiler));
 
     inTryStatement = false; // TODO(lry): why? Document.
 
     int argumentIndex = 0;
     if (function.isInstanceMember) {
       localsHandler.updateLocal(localsHandler.closureData.thisLocal,
@@ skipping 3777 matching lines @@
 
     var nativeBehavior = new native.NativeBehavior()
       ..sideEffects.setAllSideEffects();
 
     DartType type = element.isConstructor
         ? element.enclosingClass.thisType
         : element.type.returnType;
     // Native behavior effects here are similar to native/behavior.dart.
     // The return type is dynamic if we don't trust js-interop type
     // declarations.
-    nativeBehavior.typesReturned.add(compiler
-        .options.trustJSInteropTypeAnnotations ? type : const DynamicType());
+    nativeBehavior.typesReturned.add(
+        compiler.options.trustJSInteropTypeAnnotations
+            ? type
+            : const DynamicType());
 
     // The allocation effects include the declared type if it is native (which
     // includes js interop types).
     if (type.element != null && backend.isNative(type.element)) {
       nativeBehavior.typesInstantiated.add(type);
     }
 
     // It also includes any other JS interop type if we don't trust the
     // annotation or if is declared too broad.
     if (!compiler.options.trustJSInteropTypeAnnotations ||
@@ skipping 2968 matching lines @@
   const _LoopTypeVisitor();
   int visitNode(ast.Node node) => HLoopBlockInformation.NOT_A_LOOP;
   int visitWhile(ast.While node) => HLoopBlockInformation.WHILE_LOOP;
   int visitFor(ast.For node) => HLoopBlockInformation.FOR_LOOP;
   int visitDoWhile(ast.DoWhile node) => HLoopBlockInformation.DO_WHILE_LOOP;
   int visitAsyncForIn(ast.AsyncForIn node) => HLoopBlockInformation.FOR_IN_LOOP;
   int visitSyncForIn(ast.SyncForIn node) => HLoopBlockInformation.FOR_IN_LOOP;
   int visitSwitchStatement(ast.SwitchStatement node) =>
       HLoopBlockInformation.SWITCH_CONTINUE_LOOP;
 }