dart2js cps: Refactor and optimize string concatenations.

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 '../dart2jslib.dart' as dart2js;
 import '../elements/elements.dart';
 import '../cps_ir/cps_ir_nodes.dart' as cps_ir;
 import '../util/util.dart' show CURRENT_ELEMENT_SPANNABLE;
@@ skipping 346 matching lines @@
   }
 
   Statement visitInvokeMethodDirectly(cps_ir.InvokeMethodDirectly node) {
     Expression receiver = getVariableUse(node.receiver);
     List<Expression> arguments = translateArguments(node.arguments);
     Expression invoke = new InvokeMethodDirectly(receiver, node.target,
         node.selector, arguments);
     return continueWithExpression(node.continuation, invoke);
   }
 
-  Statement visitConcatenateStrings(cps_ir.ConcatenateStrings node) {
-    List<Expression> arguments = translateArguments(node.arguments);
-    Expression concat = new ConcatenateStrings(arguments);
-    return continueWithExpression(node.continuation, concat);
-  }
-
   Statement visitThrow(cps_ir.Throw node) {
     Expression value = getVariableUse(node.value);
     return new Throw(value);
   }
 
   Statement visitRethrow(cps_ir.Rethrow node) {
     return new Rethrow();
   }
 
   Statement visitUnreachable(cps_ir.Unreachable node) {
@@ skipping 109 matching lines @@
     thenStatement =
         cont.hasExactlyOneUse ? visit(cont.body) : new Break(labels[cont]);
     cont = node.falseContinuation.definition;
     assert(cont.parameters.isEmpty);
     elseStatement =
         cont.hasExactlyOneUse ? visit(cont.body) : new Break(labels[cont]);
     return new If(condition, thenStatement, elseStatement);
   }
 
   Expression visitConstant(cps_ir.Constant node) {
-    return new Constant(node.expression, node.value);
+    return new Constant(node.value);
   }
 
   Expression visitLiteralList(cps_ir.LiteralList node) {
     return new LiteralList(
             node.type,
             translateArguments(node.values));
   }
 
   Expression visitLiteralMap(cps_ir.LiteralMap node) {
     return new LiteralMap(
@@ skipping 78 matching lines @@
     return new ApplyBuiltinOperator(node.operator,
                                     translateArguments(node.arguments));
   }
 
   @override
   visitForeignCode(cps_ir.ForeignCode node) {
     unexpectedNode(node);
   }
 }