dart2js cps: Use a strictness flag on Branch instead of rewriting.

pkg/compiler/lib/src/tree_ir/tree_ir_builder.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_builder;
 
 import '../diagnostics/invariant.dart' show
     InternalErrorFunction;
 import '../diagnostics/spannable.dart' show
     CURRENT_ELEMENT_SPANNABLE;
 import '../elements/elements.dart';
 import '../cps_ir/cps_ir_nodes.dart' as cps_ir;
 import 'tree_ir_nodes.dart';
+import '../constants/values.dart';
 
 typedef Statement NodeCallback(Statement next);
 
 /**
  * Builder translates from CPS-based IR to direct-style Tree.
  *
  * A call `Invoke(fun, cont, args)`, where cont is a singly-referenced
  * non-exit continuation `Cont(v, body)` is translated into a direct-style call
  * whose value is bound in the continuation body:
  *
@@ skipping 246 matching lines @@
     return result;
   }
 
   /// Translates a CPS primitive to a tree expression.
   ///
   /// This simply calls the visit method for the primitive.
   Expression translatePrimitive(cps_ir.Primitive prim) {
     return prim.accept(this);
   }
 
-  /// Translates a condition to a tree expression.
-  Expression translateCondition(cps_ir.Condition condition) {
-    cps_ir.IsTrue isTrue = condition;
-    return getVariableUse(isTrue.value);
-  }
-
   /************************ INTERIOR EXPRESSIONS  ************************/
   //
   // Visit methods for interior expressions must return a function:
   //
   //    (Statement next) => <result statement>
   //
 
   NodeCallback visitLetPrim(cps_ir.LetPrim node) => (Statement next) {
     Variable variable = getVariable(node.primitive);
     Expression value = translatePrimitive(node.primitive);
@@ skipping 197 matching lines @@
                                   translateExpression(cont.body));
             } else {
               return cont.hasExactlyOneUse && !node.isEscapingTry
                   ? translateExpression(cont.body)
                   : new Break(getLabel(cont));
             }
           });
     }
   }
 
+  /// Translates a branch condition to a tree expression.
+  Expression translateCondition(cps_ir.Branch branch) {
+    Expression value = getVariableUse(branch.condition);
+    if (branch.isStrictCheck) {
+      return new ApplyBuiltinOperator(
+          BuiltinOperator.StrictEq,
+          <Expression>[value, new Constant(new TrueConstantValue())]);
+    } else {
+      return value;
+    }
+  }
+
   Statement visitBranch(cps_ir.Branch node) {
-    Expression condition = translateCondition(node.condition);
+    Expression condition = translateCondition(node);
     Statement thenStatement, elseStatement;
     cps_ir.Continuation cont = node.trueContinuation.definition;
     assert(cont.parameters.isEmpty);
     thenStatement = cont.hasExactlyOneUse
         ? translateExpression(cont.body)
         : new Break(labels[cont]);
     cont = node.falseContinuation.definition;
     assert(cont.parameters.isEmpty);
     elseStatement = cont.hasExactlyOneUse
         ? translateExpression(cont.body)
@@ skipping 158 matching lines @@
   unexpectedNode(cps_ir.Node node) {
     internalError(CURRENT_ELEMENT_SPANNABLE, 'Unexpected IR node: $node');
   }
 
   visitFunctionDefinition(cps_ir.FunctionDefinition node) {
     unexpectedNode(node);
   }
   visitParameter(cps_ir.Parameter node) => unexpectedNode(node);
   visitContinuation(cps_ir.Continuation node) => unexpectedNode(node);
   visitMutableVariable(cps_ir.MutableVariable node) => unexpectedNode(node);
-  visitIsTrue(cps_ir.IsTrue node) => unexpectedNode(node);
 }