dart2js cps: Clean up and avoid processing unreachable code.

pkg/compiler/lib/src/tree_ir/optimization/loop_rewriter.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.
 
 library tree_ir.optimization.loop_rewriter;
 
 import 'optimization.dart' show Pass;
 import '../tree_ir_nodes.dart';
 
 /// Rewrites [WhileTrue] statements into [For] statements.
@@ skipping 34 matching lines @@
 ///   L:
 ///   while (E) {
 ///     S1
 ///   };
 ///   S2
 ///
 /// A similar transformation is used when S2 occurs in the 'then' position.
 ///
 /// Note that the pattern above needs no iteration since nested ifs have been
 /// collapsed previously in the [StatementRewriter] phase.
-/// 
+///
 ///
 /// PULL INTO UPDATE EXPRESSION:
-/// 
+///
 /// Assignment expressions before the unique continue to a [whileCondition] are
 /// pulled into the updates for the loop.
-/// 
+///
 ///   L:
 ///   for (; condition; updates) {
 ///     S [ x = E; continue L ]
 ///   }
 ///     ==>
 ///   L:
 ///   for (; condition; updates, x = E) {
 ///     S [ continue L ]
 ///   }
 ///
-/// The decision to only pull in assignments is a heuristic to balance 
+/// The decision to only pull in assignments is a heuristic to balance
 /// readability and stack trace usability versus the modest code size
 /// reduction one might get by aggressively moving expressions into the
 /// updates.
 class LoopRewriter extends RecursiveTransformer
                    implements Pass {
   String get passName => 'Loop rewriter';
 
   Set<Label> usedContinueLabels = new Set<Label>();
 
   /// Maps loop labels to a list, if that loop can accept update expressions.
   /// The list will then be populated while traversing the body of that loop.
   /// If a loop is not in the map, update expressions cannot be hoisted there.
   Map<Label, List<Expression>> updateExpressions = <Label, List<Expression>>{};
 
   void rewrite(FunctionDefinition root) {
     root.body = visitStatement(root.body);
   }
 
-  @override
-  void visitInnerFunction(FunctionDefinition node) {
-    node.body = new LoopRewriter().visitStatement(node.body);
-  }
-
   Statement visitContinue(Continue node) {
     usedContinueLabels.add(node.target);
     return node;
   }
 
   Statement visitWhileTrue(WhileTrue node) {
     assert(!usedContinueLabels.contains(node.label));
 
     // Pull labeled statements outside the loop when possible.
     // [head] and [tail] are the first and last labeled statements that were
@@ skipping 86 matching lines @@
         } else {
           return next;
         }
       }
     }
     // The expression statements could not be pulled into a loop update.
     node.next = next;
     return statements.first;
   }
 }