Overhaul tree IR visitor and rename IR classes.

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

 // Copyright (c) 2014, 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.
 
 part of dart2js.cps_ir.optimizers;
 
 /**
  * [ShrinkingReducer] applies shrinking reductions to CPS terms as described
  * in 'Compiling with Continuations, Continued' by Andrew Kennedy.
  */
-class ShrinkingReducer extends PassMixin {
+class ShrinkingReducer extends Pass {
   String get passName => 'Shrinking reductions';
 
   Set<_ReductionTask> _worklist;
 
   static final _DeletedNode _DELETED = new _DeletedNode();
 
   /// Applies shrinking reductions to root, mutating root in the process.
   @override
-  void rewriteExecutableDefinition(ExecutableDefinition root) {
+  void rewrite(RootNode root) {
+    if (root.isEmpty) return;
+
     _worklist = new Set<_ReductionTask>();
     _RedexVisitor redexVisitor = new _RedexVisitor(_worklist);
 
     // Set all parent pointers.
     new ParentVisitor().visit(root);
 
     // Sweep over the term, collecting redexes into the worklist.
     redexVisitor.visit(root);
 
     // Process the worklist.
@@ skipping 426 matching lines @@
       Node parent = primitive.parent;
       // The parent might be the deleted sentinel, or it might be a
       // Continuation or FunctionDefinition if the primitive is an argument.
       if (parent is LetPrim && _isDeadVal(parent)) {
         worklist.add(new _ReductionTask(_ReductionKind.DEAD_VAL, parent));
       }
     } else if (reference.definition is Continuation) {
       Continuation cont = reference.definition;
       Node parent = cont.parent;
       // The parent might be the deleted sentinel, or it might be a
-      // RunnableBody if the continuation is the return continuation.
+      // Body if the continuation is the return continuation.
       if (parent is LetCont) {
         if (cont.isRecursive && cont.hasAtMostOneUse) {
           // Convert recursive to nonrecursive continuations.  If the
           // continuation is still in use, it is either dead and will be
           // removed, or it is called nonrecursively outside its body.
           cont.isRecursive = false;
         }
         if (_isDeadCont(cont)) {
           worklist.add(new _ReductionTask(_ReductionKind.DEAD_CONT, cont));
         } else if (_isBetaContLin(cont)) {
           worklist.add(new _ReductionTask(_ReductionKind.BETA_CONT_LIN, cont));
         }
       }
     }
   }
 }
 
 /// Traverses the CPS term and sets node.parent for each visited node.
 class ParentVisitor extends RecursiveVisitor {
   processFunctionDefinition(FunctionDefinition node) {
     node.body.parent = node;
     if (node.thisParameter != null) node.thisParameter.parent = node;
     int index = 0;
     node.parameters.forEach((Definition parameter) {
       parameter.parent = node;
       if (parameter is Parameter) parameter.parentIndex = index++;
     });
   }
 
-  processRunnableBody(RunnableBody node) {
+  processBody(Body node) {
     node.returnContinuation.parent = node;
     node.body.parent = node;
   }
 
   processConstructorDefinition(ConstructorDefinition node) {
     node.body.parent = node;
     int index = 0;
     node.parameters.forEach((Definition parameter) {
       parameter.parent = node;
       if (parameter is Parameter) parameter.parentIndex = index++;
     });
     node.initializers.forEach((Initializer i) => i.parent = node);
   }
 
   // Expressions.
 
   processFieldInitializer(FieldInitializer node) {
     node.body.parent = node;
   }
 
   processSuperInitializer(SuperInitializer node) {
-    node.arguments.forEach((RunnableBody argument) => argument.parent = node);
+    node.arguments.forEach((Body argument) => argument.parent = node);
   }
 
   processLetPrim(LetPrim node) {
     node.primitive.parent = node;
     node.body.parent = node;
   }
 
   processLetCont(LetCont node) {
     int index = 0;
     node.continuations.forEach((Continuation continuation) {
@@ skipping 184 matching lines @@
   }
 
   String toString() => "$kind: $node";
 }
 
 /// A dummy class used solely to mark nodes as deleted once they are removed
 /// from a term.
 class _DeletedNode extends Node {
   accept(_) => null;
 }