Simplify generated code for string interpolation by delaying the constant folding.

lib/compiler/implementation/ssa/codegen.dart

 // Copyright (c) 2012, 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.
 
 class SsaCodeGeneratorTask extends CompilerTask {
   final JavaScriptBackend backend;
   SsaCodeGeneratorTask(JavaScriptBackend backend)
       : this.backend = backend,
         super(backend.compiler);
   String get name() => 'SSA code generator';
@@ skipping 1792 matching lines @@
 
   void visitStaticStore(HStaticStore node) {
     world.registerStaticUse(node.element);
     beginExpression(JSPrecedence.ASSIGNMENT_PRECEDENCE);
     buffer.add(compiler.namer.isolateAccess(node.element));
     buffer.add(' = ');
     use(node.inputs[0], JSPrecedence.ASSIGNMENT_PRECEDENCE);
     endExpression(JSPrecedence.ASSIGNMENT_PRECEDENCE);
   }
 
+  void visitStringConcat(HStringConcat node) {
+    JSBinaryOperatorPrecedence operatorPrecedences = JSPrecedence.binary['+'];
+    beginExpression(operatorPrecedences.precedence);
+    useStringified(node.inputs[0], operatorPrecedences.left);
+    buffer.add(' + ');
+    // If the right hand side is a string concatenation itself it is
+    // safe to make it left associative.
+    JSPrecedence rightPrecedence = (node.inputs[1] is HStringConcat)

[Lasse Reichstein Nielsen, 2012/06/06 12:11:40]

JSPrecedence -> int.
The JSPrecedence class is just a static class container for the int-constants
(i.e., it's just a namespace).

[kasperl, 2012/06/06 13:31:03]

Done.

+        ? JSPrecedence.ADDITIVE_PRECEDENCE
+        : operatorPrecedences.right;
+    useStringified(node.inputs[1], rightPrecedence);
+    endExpression(operatorPrecedences.precedence);
+  }
+
+  void useStringified(HInstruction node, JSPrecedence precedence) {
+    if (node.isString()) {
+      use(node, precedence);
+    } else {
+      Element convertToString = compiler.findHelper(const SourceString("S"));
+      world.registerStaticUse(convertToString);
+      buffer.add(compiler.namer.isolateAccess(convertToString));

[Lasse Reichstein Nielsen, 2012/06/06 12:11:40]

Maybe we should have a function that does all this, so we can just write:
  addHelper(const SourceString("S"));

+      buffer.add('(');
+      use(node, JSPrecedence.EXPRESSION_PRECEDENCE);
+      buffer.add(')');
+    }
+  }
+
   void visitLiteralList(HLiteralList node) {
     generateArrayLiteral(node);
   }
 
   void generateArrayLiteral(HLiteralList node) {
     buffer.add('[');
     int len = node.inputs.length;
     for (int i = 0; i < len; i++) {
       if (i != 0) buffer.add(', ');
       use(node.inputs[i], JSPrecedence.ASSIGNMENT_PRECEDENCE);
@@ skipping 750 matching lines @@
       startBailoutSwitch();
     }
   }
 
   void endLabeledBlock(HLabeledBlockInformation labeledBlockInfo) {
     if (labeledBlockInfo.body.start.hasGuards()) {
       endBailoutSwitch();
     }
   }
 }