[turbofan] Flatten cons strings before embedding them into optimized code.

src/compiler/js-graph.cc

Index: src/compiler/js-graph.cc
diff --git a/src/compiler/js-graph.cc b/src/compiler/js-graph.cc
index 9c1baa00e644f9c5d2091a1f4c7c55909dfa1ac2..594cb6445bac0ff397b0f4bc88a11a432ffac98a 100644
--- a/src/compiler/js-graph.cc
+++ b/src/compiler/js-graph.cc
@@ -72,7 +72,9 @@ Node* JSGraph::NaNConstant() {
 
 
 Node* JSGraph::HeapConstant(Handle<HeapObject> value) {
-  // TODO(bmeurer): Flatten cons strings here before we canonicalize them?
+  if (value->IsConsString()) {

[Yang, 2015/12/16 06:24:16]

String::Flatten already checks for cons string. No need to do it here.

[Benedikt Meurer, 2015/12/16 06:26:02]

That doesn't really help, since we'd have to test for string at least :-)

+    value = String::Flatten(Handle<String>::cast(value), TENURED);
+  }
   Node** loc = cache_.FindHeapConstant(value);
   if (*loc == nullptr) {
     *loc = graph()->NewNode(common()->HeapConstant(value));