Symbols for type cells.

src/full-codegen.cc

Index: src/full-codegen.cc
diff --git a/src/full-codegen.cc b/src/full-codegen.cc
index 16bb6c0d01330e73bacb096ed5d70619ed615078..dc645952d8ff6dcb12c02016569b306e71031aee 100644
--- a/src/full-codegen.cc
+++ b/src/full-codegen.cc
@@ -388,10 +388,13 @@ unsigned FullCodeGenerator::EmitBackEdgeTable() {
 
 void FullCodeGenerator::InitializeFeedbackVector() {
   int length = info_->function()->slot_count();
-  ASSERT_EQ(isolate()->heap()->the_hole_value(),
-            *TypeFeedbackInfo::UninitializedSentinel(isolate()));
-  feedback_vector_ = isolate()->factory()->NewFixedArrayWithHoles(length,
-                                                                  TENURED);
+  feedback_vector_ = isolate()->factory()->NewFixedArray(length, TENURED);
+  Handle<Object> sentinel = TypeFeedbackInfo::UninitializedSentinel(isolate());
+  // Ensure that it's safe to set without using a write barrier.
+  ASSERT_EQ(isolate()->heap()->uninitialized_symbol(), *sentinel);
+  for (int i = 0; i < length; i++) {
+    feedback_vector_->set(i, *sentinel, SKIP_WRITE_BARRIER);
+  }
 }