Revert "Move dart2js from sdk/lib/_internal/compiler to pkg/compiler"

pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart

Index: pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
diff --git a/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart b/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
deleted file mode 100644
index 4ea9bebb5900e8c8b9236a5ab003c9ac7846253d..0000000000000000000000000000000000000000
--- a/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
+++ /dev/null
@@ -1,954 +0,0 @@
-// Copyright (c) 2013, 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.
-
-// IrNodes are kept in a separate library to have precise control over their
-// dependencies on other parts of the system.
-library dart2js.ir_nodes;
-
-import '../constants/expressions.dart';
-import '../constants/values.dart' as values show ConstantValue;
-import '../dart2jslib.dart' as dart2js show invariant;
-import '../elements/elements.dart';
-import '../universe/universe.dart' show Selector, SelectorKind;
-import '../dart_types.dart' show DartType, GenericType;
-
-abstract class Node {
-  static int hashCount = 0;
-  final int hashCode = hashCount = (hashCount + 1) & 0x3fffffff;
-
-  /// A pointer to the parent node. Is null until set by optimization passes.
-  Node parent;
-
-  accept(Visitor visitor);
-}
-
-abstract class Expression extends Node {
-  Expression plug(Expression expr) => throw 'impossible';
-}
-
-/// The base class of things that variables can refer to: primitives,
-/// continuations, function and continuation parameters, etc.
-abstract class Definition extends Node {
-  // The head of a linked-list of occurrences, in no particular order.
-  Reference firstRef = null;
-
-  bool get hasAtMostOneUse  => firstRef == null || firstRef.next == null;
-  bool get hasExactlyOneUse => firstRef != null && firstRef.next == null;
-  bool get hasAtLeastOneUse => firstRef != null;
-  bool get hasMultipleUses  => !hasAtMostOneUse;
-
-  void substituteFor(Definition other) {
-    if (other.firstRef == null) return;
-    Reference previous, current = other.firstRef;
-    do {
-      current.definition = this;
-      previous = current;
-      current = current.next;
-    } while (current != null);
-    previous.next = firstRef;
-    if (firstRef != null) firstRef.previous = previous;
-    firstRef = other.firstRef;
-  }
-}
-
-/// An expression that cannot throw or diverge and has no side-effects.
-/// All primitives are named using the identity of the [Primitive] object.
-///
-/// Primitives may allocate objects, this is not considered side-effect here.
-///
-/// Although primitives may not mutate state, they may depend on state.
-abstract class Primitive extends Definition {
-  /// The [VariableElement] or [ParameterElement] from which the primitive
-  /// binding originated.
-  Element hint;
-
-  /// Register in which the variable binding this primitive can be allocated.
-  /// Separate register spaces are used for primitives with different [element].
-  /// Assigned by [RegisterAllocator], is null before that phase.
-  int registerIndex;
-
-  /// Use the given element as a hint for naming this primitive.
-  ///
-  /// Has no effect if this primitive already has a non-null [element].
-  void useElementAsHint(Element hint) {
-    if (this.hint == null) {
-      this.hint = hint;
-    }
-  }
-}
-
-/// Operands to invocations and primitives are always variables.  They point to
-/// their definition and are doubly-linked into a list of occurrences.
-class Reference {
-  Definition definition;
-  Reference previous = null;
-  Reference next = null;
-
-  /// A pointer to the parent node. Is null until set by optimization passes.
-  Node parent;
-
-  Reference(this.definition) {
-    next = definition.firstRef;
-    if (next != null) next.previous = this;
-    definition.firstRef = this;
-  }
-
-  /// Unlinks this reference from the list of occurrences.
-  void unlink() {
-    if (previous == null) {
-      assert(definition.firstRef == this);
-      definition.firstRef = next;
-    } else {
-      previous.next = next;
-    }
-    if (next != null) next.previous = previous;
-  }
-}
-
-/// Binding a value (primitive or constant): 'let val x = V in E'.  The bound
-/// value is in scope in the body.
-/// During one-pass construction a LetVal with an empty body is used to
-/// represent one-level context 'let val x = V in []'.
-class LetPrim extends Expression implements InteriorNode {
-  final Primitive primitive;
-  Expression body = null;
-
-  LetPrim(this.primitive);
-
-  Expression plug(Expression expr) {
-    assert(body == null);
-    return body = expr;
-  }
-
-  accept(Visitor visitor) => visitor.visitLetPrim(this);
-}
-
-
-/// Binding a continuation: 'let cont k(v) = E in E'.  The bound continuation
-/// is in scope in the body and the continuation parameter is in scope in the
-/// continuation body.
-/// During one-pass construction a LetCont with an empty continuation body is
-/// used to represent the one-level context 'let cont k(v) = [] in E'.
-class LetCont extends Expression implements InteriorNode {
-  Continuation continuation;
-  Expression body;
-
-  LetCont(this.continuation, this.body);
-
-  Expression plug(Expression expr) {
-    assert(continuation != null && continuation.body == null);
-    return continuation.body = expr;
-  }
-
-  accept(Visitor visitor) => visitor.visitLetCont(this);
-}
-
-abstract class Invoke {
-  Selector get selector;
-  List<Reference> get arguments;
-}
-
-/// Represents a node with a child node, which can be accessed through the
-/// `body` member. A typical usage is when removing a node from the CPS graph:
-///
-///     Node child          = node.body;
-///     InteriorNode parent = node.parent;
-///
-///     child.parent = parent;
-///     parent.body  = child;
-abstract class InteriorNode implements Node {
-  Expression body;
-}
-
-/// Invoke a static function or static field getter/setter.
-class InvokeStatic extends Expression implements Invoke {
-  /// [FunctionElement] or [FieldElement].
-  final Entity target;
-
-  /**
-   * The selector encodes how the function is invoked: number of positional
-   * arguments, names used in named arguments. This information is required
-   * to build the [StaticCallSiteTypeInformation] for the inference graph.
-   */
-  final Selector selector;
-
-  final Reference continuation;
-  final List<Reference> arguments;
-
-  InvokeStatic(this.target, this.selector, Continuation cont,
-               List<Definition> args)
-      : continuation = new Reference(cont),
-        arguments = _referenceList(args) {
-    assert(target is ErroneousElement || selector.name == target.name);
-  }
-
-  accept(Visitor visitor) => visitor.visitInvokeStatic(this);
-}
-
-/// Invoke a method, operator, getter, setter, or index getter/setter.
-/// Converting a method to a function object is treated as a getter invocation.
-class InvokeMethod extends Expression implements Invoke {
-  final Reference receiver;
-  final Selector selector;
-  final Reference continuation;
-  final List<Reference> arguments;
-
-  InvokeMethod(Definition receiver,
-               this.selector,
-               Continuation cont,
-               List<Definition> args)
-      : receiver = new Reference(receiver),
-        continuation = new Reference(cont),
-        arguments = _referenceList(args) {
-    assert(selector != null);
-    assert(selector.kind == SelectorKind.CALL ||
-           selector.kind == SelectorKind.OPERATOR ||
-           (selector.kind == SelectorKind.GETTER && arguments.isEmpty) ||
-           (selector.kind == SelectorKind.SETTER && arguments.length == 1) ||
-           (selector.kind == SelectorKind.INDEX && arguments.length == 1) ||
-           (selector.kind == SelectorKind.INDEX && arguments.length == 2));
-  }
-
-  accept(Visitor visitor) => visitor.visitInvokeMethod(this);
-}
-
-/// Invoke a method, operator, getter, setter, or index getter/setter from the
-/// super class in tail position.
-class InvokeSuperMethod extends Expression implements Invoke {
-  final Selector selector;
-  final Reference continuation;
-  final List<Reference> arguments;
-
-  InvokeSuperMethod(this.selector,
-                    Continuation cont,
-                    List<Definition> args)
-      : continuation = new Reference(cont),
-        arguments = _referenceList(args) {
-    assert(selector != null);
-    assert(selector.kind == SelectorKind.CALL ||
-           selector.kind == SelectorKind.OPERATOR ||
-           (selector.kind == SelectorKind.GETTER && arguments.isEmpty) ||
-           (selector.kind == SelectorKind.SETTER && arguments.length == 1) ||
-           (selector.kind == SelectorKind.INDEX && arguments.length == 1) ||
-           (selector.kind == SelectorKind.INDEX && arguments.length == 2));
-  }
-
-  accept(Visitor visitor) => visitor.visitInvokeSuperMethod(this);
-}
-
-/// Non-const call to a constructor. The [target] may be a generative
-/// constructor, factory, or redirecting factory.
-class InvokeConstructor extends Expression implements Invoke {
-  final DartType type;
-  final FunctionElement target;
-  final Reference continuation;
-  final List<Reference> arguments;
-  final Selector selector;
-
-  /// The class being instantiated. This is the same as `target.enclosingClass`
-  /// and `type.element`.
-  ClassElement get targetClass => target.enclosingElement;
-
-  /// True if this is an invocation of a factory constructor.
-  bool get isFactory => target.isFactoryConstructor;
-
-  InvokeConstructor(this.type,
-                    this.target,
-                    this.selector,
-                    Continuation cont,
-                    List<Definition> args)
-      : continuation = new Reference(cont),
-        arguments = _referenceList(args) {
-    assert(dart2js.invariant(target,
-        target.isErroneous || target.isConstructor,
-        message: "Constructor invocation target is not a constructor: "
-                 "$target."));
-    assert(dart2js.invariant(target,
-        target.isErroneous ||
-        type.isDynamic ||
-        type.element == target.enclosingClass.declaration,
-        message: "Constructor invocation type ${type} does not match enclosing "
-                 "class of target ${target}."));
-  }
-
-  accept(Visitor visitor) => visitor.visitInvokeConstructor(this);
-}
-
-/// "as" casts and "is" checks.
-// We might want to turn "is"-checks into a [Primitive] as it can never diverge.
-// But then we need to special-case for is-checks with an erroneous .type as
-// these will throw.
-class TypeOperator extends Expression {
-  final Reference receiver;
-  final DartType type;
-  final Reference continuation;
-  // TODO(johnniwinther): Use `Operator` class to encapsule the operator type.
-  final bool isTypeTest;
-
-  TypeOperator(Primitive receiver,
-               this.type,
-               Continuation cont,
-               {bool this.isTypeTest})
-      : this.receiver = new Reference(receiver),
-        this.continuation = new Reference(cont) {
-    assert(isTypeTest != null);
-  }
-
-  bool get isTypeCast => !isTypeTest;
-
-  accept(Visitor visitor) => visitor.visitTypeOperator(this);
-}
-
-/// Invoke [toString] on each argument and concatenate the results.
-class ConcatenateStrings extends Expression {
-  final Reference continuation;
-  final List<Reference> arguments;
-
-  ConcatenateStrings(Continuation cont, List<Definition> args)
-      : continuation = new Reference(cont),
-        arguments = _referenceList(args);
-
-  accept(Visitor visitor) => visitor.visitConcatenateStrings(this);
-}
-
-/// Gets the value from a closure variable. The identity of the variable is
-/// determined by a [Local].
-///
-/// Closure variables can be seen as ref cells that are not first-class values.
-/// A [LetPrim] with a [GetClosureVariable] can then be seen as:
-///
-///   let prim p = ![variable] in [body]
-///
-class GetClosureVariable extends Primitive {
-  final Local variable;
-
-  GetClosureVariable(this.variable) {
-    assert(variable != null);
-  }
-
-  accept(Visitor visitor) => visitor.visitGetClosureVariable(this);
-}
-
-/// Assign or declare a closure variable. The identity of the variable is
-/// determined by a [Local].
-///
-/// Closure variables can be seen as ref cells that are not first-class values.
-/// If [isDeclaration], this can seen as a let binding:
-///
-///   let [variable] = ref [value] in [body]
-///
-/// And otherwise, it can be seen as a dereferencing assignment:
-///
-///   { ![variable] := [value]; [body] }
-///
-/// Closure variables without a declaring [SetClosureVariable] are implicitly
-/// declared at the entry to the [variable]'s enclosing function.
-class SetClosureVariable extends Expression implements InteriorNode {
-  final Local variable;
-  final Reference value;
-  Expression body;
-
-  /// If true, this declares a new copy of the closure variable. If so, all
-  /// uses of the closure variable must occur in the [body].
-  ///
-  /// There can be at most one declaration per closure variable. If there is no
-  /// declaration, only one copy exists (per function execution). It is best to
-  /// avoid declaring closure variables if it is not necessary.
-  final bool isDeclaration;
-
-  SetClosureVariable(this.variable, Primitive value,
-                     {this.isDeclaration : false })
-      : this.value = new Reference(value) {
-    assert(variable != null);
-  }
-
-  accept(Visitor visitor) => visitor.visitSetClosureVariable(this);
-
-  Expression plug(Expression expr) {
-    assert(body == null);
-    return body = expr;
-  }
-}
-
-/// Create a potentially recursive function and store it in a closure variable.
-/// The function can access itself using [GetClosureVariable] on [variable].
-/// There must not exist a [SetClosureVariable] to [variable].
-///
-/// This can be seen as a let rec binding:
-///
-///   let rec [variable] = [definition] in [body]
-///
-class DeclareFunction extends Expression implements InteriorNode {
-  final Local variable;
-  final FunctionDefinition definition;
-  Expression body;
-
-  DeclareFunction(this.variable, this.definition);
-
-  Expression plug(Expression expr) {
-    assert(body == null);
-    return body = expr;
-  }
-
-  accept(Visitor visitor) => visitor.visitDeclareFunction(this);
-}
-
-/// Invoke a continuation in tail position.
-class InvokeContinuation extends Expression {
-  Reference continuation;
-  List<Reference> arguments;
-
-  // An invocation of a continuation is recursive if it occurs in the body of
-  // the continuation itself.
-  bool isRecursive;
-
-  InvokeContinuation(Continuation cont, List<Definition> args,
-                     {recursive: false})
-      : continuation = new Reference(cont),
-        arguments = _referenceList(args),
-        isRecursive = recursive {
-    assert(cont.parameters == null ||
-        cont.parameters.length == args.length);
-    if (recursive) cont.isRecursive = true;
-  }
-
-  /// A continuation invocation whose target and arguments will be filled
-  /// in later.
-  ///
-  /// Used as a placeholder for a jump whose target is not yet created
-  /// (e.g., in the translation of break and continue).
-  InvokeContinuation.uninitialized({recursive: false})
-      : continuation = null,
-        arguments = null,
-        isRecursive = recursive;
-
-  accept(Visitor visitor) => visitor.visitInvokeContinuation(this);
-}
-
-/// The base class of things which can be tested and branched on.
-abstract class Condition extends Node {
-}
-
-class IsTrue extends Condition {
-  final Reference value;
-
-  IsTrue(Definition val) : value = new Reference(val);
-
-  accept(Visitor visitor) => visitor.visitIsTrue(this);
-}
-
-/// Choose between a pair of continuations based on a condition value.
-class Branch extends Expression {
-  final Condition condition;
-  final Reference trueContinuation;
-  final Reference falseContinuation;
-
-  Branch(this.condition, Continuation trueCont, Continuation falseCont)
-      : trueContinuation = new Reference(trueCont),
-        falseContinuation = new Reference(falseCont);
-
-  accept(Visitor visitor) => visitor.visitBranch(this);
-}
-
-class Constant extends Primitive {
-  final ConstantExpression expression;
-
-  Constant(this.expression);
-
-  values.ConstantValue get value => expression.value;
-
-  accept(Visitor visitor) => visitor.visitConstant(this);
-}
-
-class This extends Primitive {
-  This();
-
-  accept(Visitor visitor) => visitor.visitThis(this);
-}
-
-/// Reify the given type variable as a [Type].
-/// This depends on the current binding of 'this'.
-class ReifyTypeVar extends Primitive {
-  final TypeVariableElement typeVariable;
-
-  ReifyTypeVar(this.typeVariable);
-
-  values.ConstantValue get constant => null;
-
-  accept(Visitor visitor) => visitor.visitReifyTypeVar(this);
-}
-
-class LiteralList extends Primitive {
-  /// The List type being created; this is not the type argument.
-  final GenericType type;
-  final List<Reference> values;
-
-  LiteralList(this.type, Iterable<Primitive> values)
-      : this.values = _referenceList(values);
-
-  accept(Visitor visitor) => visitor.visitLiteralList(this);
-}
-
-class LiteralMapEntry {
-  final Reference key;
-  final Reference value;
-
-  LiteralMapEntry(Primitive key, Primitive value)
-      : this.key = new Reference(key),
-        this.value = new Reference(value);
-}
-
-class LiteralMap extends Primitive {
-  final GenericType type;
-  final List<LiteralMapEntry> entries;
-
-  LiteralMap(this.type, this.entries);
-
-  accept(Visitor visitor) => visitor.visitLiteralMap(this);
-}
-
-/// Create a non-recursive function.
-class CreateFunction extends Primitive {
-  final FunctionDefinition definition;
-
-  CreateFunction(this.definition);
-
-  accept(Visitor visitor) => visitor.visitCreateFunction(this);
-}
-
-class Parameter extends Primitive {
-  Parameter(Element element) {
-    super.hint = element;
-  }
-
-  accept(Visitor visitor) => visitor.visitParameter(this);
-}
-
-/// Continuations are normally bound by 'let cont'.  A continuation with one
-/// parameter and no body is used to represent a function's return continuation.
-/// The return continuation is bound by the Function, not by 'let cont'.
-class Continuation extends Definition implements InteriorNode {
-  final List<Parameter> parameters;
-  Expression body = null;
-
-  // A continuation is recursive if it has any recursive invocations.
-  bool isRecursive = false;
-
-  bool get isReturnContinuation => body == null;
-
-  Continuation(this.parameters);
-
-  Continuation.retrn() : parameters = <Parameter>[new Parameter(null)];
-
-  accept(Visitor visitor) => visitor.visitContinuation(this);
-}
-
-/// A function definition, consisting of parameters and a body.  The parameters
-/// include a distinguished continuation parameter.
-class FunctionDefinition extends Node implements InteriorNode {
-  final FunctionElement element;
-  final Continuation returnContinuation;
-  final List<Parameter> parameters;
-  Expression body;
-  final List<ConstDeclaration> localConstants;
-
-  /// Values for optional parameters.
-  final List<ConstantExpression> defaultParameterValues;
-
-  FunctionDefinition(this.element, this.returnContinuation,
-      this.parameters, this.body, this.localConstants,
-      this.defaultParameterValues);
-
-  FunctionDefinition.abstract(this.element,
-                              this.parameters,
-                              this.defaultParameterValues)
-      : this.returnContinuation = null,
-        this.localConstants = const <ConstDeclaration>[];
-
-  accept(Visitor visitor) => visitor.visitFunctionDefinition(this);
-
-  /// Returns `true` if this function is abstract.
-  ///
-  /// If `true`, [body] and [returnContinuation] are `null` and [localConstants]
-  /// is empty.
-  bool get isAbstract => body == null;
-}
-
-List<Reference> _referenceList(Iterable<Definition> definitions) {
-  return definitions.map((e) => new Reference(e)).toList();
-}
-
-abstract class Visitor<T> {
-  T visit(Node node) => node.accept(this);
-  // Abstract classes.
-  T visitNode(Node node) => null;
-  T visitExpression(Expression node) => visitNode(node);
-  T visitDefinition(Definition node) => visitNode(node);
-  T visitPrimitive(Primitive node) => visitDefinition(node);
-  T visitCondition(Condition node) => visitNode(node);
-
-  // Concrete classes.
-  T visitFunctionDefinition(FunctionDefinition node) => visitNode(node);
-
-  // Expressions.
-  T visitLetPrim(LetPrim node) => visitExpression(node);
-  T visitLetCont(LetCont node) => visitExpression(node);
-  T visitInvokeStatic(InvokeStatic node) => visitExpression(node);
-  T visitInvokeContinuation(InvokeContinuation node) => visitExpression(node);
-  T visitInvokeMethod(InvokeMethod node) => visitExpression(node);
-  T visitInvokeSuperMethod(InvokeSuperMethod node) => visitExpression(node);
-  T visitInvokeConstructor(InvokeConstructor node) => visitExpression(node);
-  T visitConcatenateStrings(ConcatenateStrings node) => visitExpression(node);
-  T visitBranch(Branch node) => visitExpression(node);
-  T visitTypeOperator(TypeOperator node) => visitExpression(node);
-  T visitSetClosureVariable(SetClosureVariable node) => visitExpression(node);
-  T visitDeclareFunction(DeclareFunction node) => visitExpression(node);
-
-  // Definitions.
-  T visitLiteralList(LiteralList node) => visitPrimitive(node);
-  T visitLiteralMap(LiteralMap node) => visitPrimitive(node);
-  T visitConstant(Constant node) => visitPrimitive(node);
-  T visitThis(This node) => visitPrimitive(node);
-  T visitReifyTypeVar(ReifyTypeVar node) => visitPrimitive(node);
-  T visitCreateFunction(CreateFunction node) => visitPrimitive(node);
-  T visitGetClosureVariable(GetClosureVariable node) => visitPrimitive(node);
-  T visitParameter(Parameter node) => visitPrimitive(node);
-  T visitContinuation(Continuation node) => visitDefinition(node);
-
-  // Conditions.
-  T visitIsTrue(IsTrue node) => visitCondition(node);
-}
-
-/// Recursively visits the entire CPS term, and calls abstract `process*`
-/// (i.e. `processLetPrim`) functions in pre-order.
-abstract class RecursiveVisitor extends Visitor {
-  // Ensures that RecursiveVisitor contains overrides for all relevant nodes.
-  // As a rule of thumb, nodes with structure to traverse should be overridden
-  // with the appropriate visits in this class (for example, visitLetCont),
-  // while leaving other nodes for subclasses (i.e., visitLiteralList).
-  visitNode(Node node) {
-    throw "RecursiveVisitor is stale, add missing visit overrides";
-  }
-
-  processReference(Reference ref) {}
-
-  processFunctionDefinition(FunctionDefinition node) {}
-  visitFunctionDefinition(FunctionDefinition node) {
-    processFunctionDefinition(node);
-    node.parameters.forEach(visitParameter);
-    visit(node.body);
-  }
-
-  // Expressions.
-
-  processLetPrim(LetPrim node) {}
-  visitLetPrim(LetPrim node) {
-    processLetPrim(node);
-    visit(node.primitive);
-    visit(node.body);
-  }
-
-  processLetCont(LetCont node) {}
-  visitLetCont(LetCont node) {
-    processLetCont(node);
-    visit(node.continuation);
-    visit(node.body);
-  }
-
-  processInvokeStatic(InvokeStatic node) {}
-  visitInvokeStatic(InvokeStatic node) {
-    processInvokeStatic(node);
-    processReference(node.continuation);
-    node.arguments.forEach(processReference);
-  }
-
-  processInvokeContinuation(InvokeContinuation node) {}
-  visitInvokeContinuation(InvokeContinuation node) {
-    processInvokeContinuation(node);
-    processReference(node.continuation);
-    node.arguments.forEach(processReference);
-  }
-
-  processInvokeMethod(InvokeMethod node) {}
-  visitInvokeMethod(InvokeMethod node) {
-    processInvokeMethod(node);
-    processReference(node.receiver);
-    processReference(node.continuation);
-    node.arguments.forEach(processReference);
-  }
-
-  processInvokeSuperMethod(InvokeSuperMethod node) {}
-  visitInvokeSuperMethod(InvokeSuperMethod node) {
-    processInvokeSuperMethod(node);
-    processReference(node.continuation);
-    node.arguments.forEach(processReference);
-  }
-
-  processInvokeConstructor(InvokeConstructor node) {}
-  visitInvokeConstructor(InvokeConstructor node) {
-    processInvokeConstructor(node);
-    processReference(node.continuation);
-    node.arguments.forEach(processReference);
-  }
-
-  processConcatenateStrings(ConcatenateStrings node) {}
-  visitConcatenateStrings(ConcatenateStrings node) {
-    processConcatenateStrings(node);
-    processReference(node.continuation);
-    node.arguments.forEach(processReference);
-  }
-
-
-  processBranch(Branch node) {}
-  visitBranch(Branch node) {
-    processBranch(node);
-    processReference(node.trueContinuation);
-    processReference(node.falseContinuation);
-    visit(node.condition);
-  }
-
-  processTypeOperator(TypeOperator node) {}
-  visitTypeOperator(TypeOperator node) {
-    processTypeOperator(node);
-    processReference(node.continuation);
-    processReference(node.receiver);
-  }
-
-  processSetClosureVariable(SetClosureVariable node) {}
-  visitSetClosureVariable(SetClosureVariable node) {
-    processSetClosureVariable(node);
-    processReference(node.value);
-    visit(node.body);
-  }
-
-  processDeclareFunction(DeclareFunction node) {}
-  visitDeclareFunction(DeclareFunction node) {
-    processDeclareFunction(node);
-    visit(node.definition);
-    visit(node.body);
-  }
-
-  // Definitions.
-
-  processLiteralList(LiteralList node) {}
-  visitLiteralList(LiteralList node) {
-    processLiteralList(node);
-    node.values.forEach(processReference);
-  }
-
-  processLiteralMap(LiteralMap node) {}
-  visitLiteralMap(LiteralMap node) {
-    processLiteralMap(node);
-    for (LiteralMapEntry entry in node.entries) {
-      processReference(entry.key);
-      processReference(entry.value);
-    }
-  }
-
-  processConstant(Constant node) {}
-  visitConstant(Constant node) => processConstant(node);
-
-  processThis(This node) {}
-  visitThis(This node) => processThis(node);
-
-  processReifyTypeVar(ReifyTypeVar node) {}
-  visitReifyTypeVar(ReifyTypeVar node) => processReifyTypeVar(node);
-
-  processCreateFunction(CreateFunction node) {}
-  visitCreateFunction(CreateFunction node) {
-    processCreateFunction(node);
-    visit(node.definition);
-  }
-
-  processGetClosureVariable(GetClosureVariable node) {}
-  visitGetClosureVariable(GetClosureVariable node) =>
-      processGetClosureVariable(node);
-
-  processParameter(Parameter node) {}
-  visitParameter(Parameter node) => processParameter(node);
-
-  processContinuation(Continuation node) {}
-  visitContinuation(Continuation node) {
-    processContinuation(node);
-    node.parameters.forEach(visitParameter);
-    visit(node.body);
-  }
-
-  // Conditions.
-
-  processIsTrue(IsTrue node) {}
-  visitIsTrue(IsTrue node) {
-    processIsTrue(node);
-    processReference(node.value);
-  }
-}
-
-/// Keeps track of currently unused register indices.
-class RegisterArray {
-  int nextIndex = 0;
-  final List<int> freeStack = <int>[];
-
-  /// Returns an index that is currently unused.
-  int makeIndex() {
-    if (freeStack.isEmpty) {
-      return nextIndex++;
-    } else {
-      return freeStack.removeLast();
-    }
-  }
-
-  void releaseIndex(int index) {
-    freeStack.add(index);
-  }
-}
-
-/// Assigns indices to each primitive in the IR such that primitives that are
-/// live simultaneously never get assigned the same index.
-/// This information is used by the dart tree builder to generate fewer
-/// redundant variables.
-/// Currently, the liveness analysis is very simple and is often inadequate
-/// for removing all of the redundant variables.
-class RegisterAllocator extends Visitor {
-  /// Separate register spaces for each source-level variable/parameter.
-  /// Note that null is used as key for primitives without elements.
-  final Map<Element, RegisterArray> elementRegisters =
-      <Element, RegisterArray>{};
-
-  RegisterArray getRegisterArray(Element element) {
-    RegisterArray registers = elementRegisters[element];
-    if (registers == null) {
-      registers = new RegisterArray();
-      elementRegisters[element] = registers;
-    }
-    return registers;
-  }
-
-  void allocate(Primitive primitive) {
-    if (primitive.registerIndex == null) {
-      primitive.registerIndex = getRegisterArray(primitive.hint).makeIndex();
-    }
-  }
-
-  void release(Primitive primitive) {
-    // Do not share indices for temporaries as this may obstruct inlining.
-    if (primitive.hint == null) return;
-    if (primitive.registerIndex != null) {
-      getRegisterArray(primitive.hint).releaseIndex(primitive.registerIndex);
-    }
-  }
-
-  void visitReference(Reference reference) {
-    allocate(reference.definition);
-  }
-
-  void visitFunctionDefinition(FunctionDefinition node) {
-    if (!node.isAbstract) {
-      visit(node.body);
-    }
-    node.parameters.forEach(allocate); // Assign indices to unused parameters.
-    elementRegisters.clear();
-  }
-
-  void visitLetPrim(LetPrim node) {
-    visit(node.body);
-    release(node.primitive);
-    visit(node.primitive);
-  }
-
-  void visitLetCont(LetCont node) {
-    visit(node.continuation);
-    visit(node.body);
-  }
-
-  void visitInvokeStatic(InvokeStatic node) {
-    node.arguments.forEach(visitReference);
-  }
-
-  void visitInvokeContinuation(InvokeContinuation node) {
-    node.arguments.forEach(visitReference);
-  }
-
-  void visitInvokeMethod(InvokeMethod node) {
-    visitReference(node.receiver);
-    node.arguments.forEach(visitReference);
-  }
-
-  void visitInvokeSuperMethod(InvokeSuperMethod node) {
-    node.arguments.forEach(visitReference);
-  }
-
-  void visitInvokeConstructor(InvokeConstructor node) {
-    node.arguments.forEach(visitReference);
-  }
-
-  void visitConcatenateStrings(ConcatenateStrings node) {
-    node.arguments.forEach(visitReference);
-  }
-
-  void visitBranch(Branch node) {
-    visit(node.condition);
-  }
-
-  void visitLiteralList(LiteralList node) {
-    node.values.forEach(visitReference);
-  }
-
-  void visitLiteralMap(LiteralMap node) {
-    for (LiteralMapEntry entry in node.entries) {
-      visitReference(entry.key);
-      visitReference(entry.value);
-    }
-  }
-
-  void visitTypeOperator(TypeOperator node) {
-    visitReference(node.receiver);
-  }
-
-  void visitConstant(Constant node) {
-  }
-
-  void visitThis(This node) {
-  }
-
-  void visitReifyTypeVar(ReifyTypeVar node) {
-  }
-
-  void visitCreateFunction(CreateFunction node) {
-    new RegisterAllocator().visit(node.definition);
-  }
-
-  void visitGetClosureVariable(GetClosureVariable node) {
-  }
-
-  void visitSetClosureVariable(SetClosureVariable node) {
-    visit(node.body);
-    visitReference(node.value);
-  }
-
-  void visitDeclareFunction(DeclareFunction node) {
-    new RegisterAllocator().visit(node.definition);
-    visit(node.body);
-  }
-
-  void visitParameter(Parameter node) {
-    throw "Parameters should not be visited by RegisterAllocator";
-  }
-
-  void visitContinuation(Continuation node) {
-    visit(node.body);
-
-    // Arguments get allocated left-to-right, so we release parameters
-    // right-to-left. This increases the likelihood that arguments can be
-    // transferred without intermediate assignments.
-    for (int i = node.parameters.length - 1; i >= 0; --i) {
-      release(node.parameters[i]);
-    }
-  }
-
-  void visitIsTrue(IsTrue node) {
-    visitReference(node.value);
-  }
-
-}
-