dart2js cps: Refactor and optimize string concatenations.

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

Index: pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
diff --git a/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart b/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
index 3c735d1aeae6649b17f3e168186c96f59572605c..f5a851019a1d8a437f8ff7cb63dc6a59ccd0ea81 100644
--- a/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
+++ b/pkg/compiler/lib/src/cps_ir/cps_ir_nodes.dart
@@ -424,18 +424,6 @@ class TypeCast extends Expression {
   accept(Visitor visitor) => visitor.visitTypeCast(this);
 }
 
-/// Invoke [toString] on each argument and concatenate the results.
-class ConcatenateStrings extends Expression {
-  final List<Reference<Primitive>> arguments;
-  final Reference<Continuation> continuation;
-
-  ConcatenateStrings(List<Primitive> args, Continuation cont)
-      : arguments = _referenceList(args),
-        continuation = new Reference<Continuation>(cont);
-
-  accept(Visitor visitor) => visitor.visitConcatenateStrings(this);
-}
-
 /// Apply a built-in operator.
 ///
 /// It must be known that the arguments have the proper types.
@@ -727,10 +715,9 @@ class CreateInvocationMirror extends Primitive {
 }
 
 class Constant extends Primitive {
-  final ConstantExpression expression;
-  final values.ConstantValue value;
+  values.ConstantValue value;

[karlklose, 2015/06/19 08:33:45]

Is this field mutated now or can we keep it final?

[asgerf, 2015/06/19 11:04:34]

We can keep it final.

 
-  Constant(this.expression, this.value);
+  Constant(this.value);
 
   accept(Visitor visitor) => visitor.visitConstant(this);
 }
@@ -924,7 +911,6 @@ abstract class Visitor<T> {
   T visitInvokeMethod(InvokeMethod node);
   T visitInvokeMethodDirectly(InvokeMethodDirectly node);
   T visitInvokeConstructor(InvokeConstructor node);
-  T visitConcatenateStrings(ConcatenateStrings node);
   T visitThrow(Throw node);
   T visitRethrow(Rethrow node);
   T visitBranch(Branch node);
@@ -1048,13 +1034,6 @@ class RecursiveVisitor implements Visitor {
     node.arguments.forEach(processReference);
   }
 
-  processConcatenateStrings(ConcatenateStrings node) {}
-  visitConcatenateStrings(ConcatenateStrings node) {
-    processConcatenateStrings(node);
-    processReference(node.continuation);
-    node.arguments.forEach(processReference);
-  }
-
   processThrow(Throw node) {}
   visitThrow(Throw node) {
     processThrow(node);