dart2js cps: Avoid deep recursion using trampolines and basic blocks.

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

 // Copyright (c) 2015, 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 dart2js.cps_ir.redundant_join_elimination;
 
 import 'cps_ir_nodes.dart';
 import 'optimizers.dart';
 
 /// Eliminates redundant join points.
@@ skipping 216 matching lines @@
 /// 
 /// After lifting LetConts in the main pass above, parameter objects can have
 /// multiple bindings. Each reference implicitly refers to the binding that
 /// is currently in scope.
 /// 
 /// This returns the IR to its normal form after redundant joins have been
 /// eliminated.
 class AlphaRenamer extends RecursiveVisitor {
   Map<Parameter, Parameter> renaming = <Parameter, Parameter>{};
 
-  visitContinuation(Continuation cont) {
+  processContinuation(Continuation cont) {
     if (cont.isReturnContinuation) return;
 
     List<Parameter> shadowedKeys = <Parameter>[];
     List<Parameter> shadowedValues = <Parameter>[];
 
     // Create new parameters and update the environment.
     for (int i = 0; i < cont.parameters.length; ++i) {
       Parameter param = cont.parameters[i];
       shadowedKeys.add(param);
       shadowedValues.add(renaming.remove(param));
       // If the parameter appears to belong to another continuation,
       // create a new parameter object for this continuation.
       if (param.parent != cont) {
         Parameter newParam = new Parameter(param.hint);
         renaming[param] = newParam;
         cont.parameters[i] = newParam;
         newParam.parent = cont;
       }
     }
 
-    // Visit the body with the updated environment.
-    visit(cont.body);
-
-    // Restore the original environment.
-    for (int i = 0; i < cont.parameters.length; ++i) {
-      renaming.remove(cont.parameters[i]);
-      if (shadowedValues[i] != null) {
-        renaming[shadowedKeys[i]] = shadowedValues[i];
+    pushAction(() {
+      // Restore the original environment.
+      for (int i = 0; i < cont.parameters.length; ++i) {
+        renaming.remove(cont.parameters[i]);
+        if (shadowedValues[i] != null) {
+          renaming[shadowedKeys[i]] = shadowedValues[i];
+        }
       }
-    }
+    });
   }
 
   processReference(Reference ref) {
     Parameter target = renaming[ref.definition];
     if (target != null) {
       ref.changeTo(target);
     }
   }
 }