Remove superfluous HInnerAllocatedObject in BuildEmitDeepCopy

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index b03bf699389be7864587415c6143280159f27979..d82d6b84329adae37fc5802c667111ecd9fa9abb 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -10022,10 +10022,22 @@ void HOptimizedGraphBuilder::BuildEmitDeepCopy(
   }
 
   // Copy in-object properties.
-  HValue* object_properties =
-      AddInstruction(new(zone) HInnerAllocatedObject(target, object_offset));
-  BuildEmitInObjectProperties(boilerplate_object, original_boilerplate_object,
-      object_properties, target, offset, data_target, data_offset);
+  Handle<DescriptorArray> descriptors(
+      boilerplate_object->map()->instance_descriptors());
+  int descriptor_count = boilerplate_object->map()->NumberOfOwnDescriptors();
+  bool has_field = false;
+  for (int i = 0; i < descriptor_count; i++) {
+    PropertyDetails details = descriptors->GetDetails(i);
+    if (details.type() != FIELD) continue;
+    has_field = true;
+  }

[Toon Verwaest, 2013/06/27 04:32:22]

Isn't there a utility function to test for this condition? If not, add one to
jsobject or map. Specifically to test for fields you can also look at the unused
property fields, inobject properties etc to check this condition in O(1).

[danno, 2013/06/27 13:55:51]

OK, I now use map()->NumberOfFields(). I'll leave it to you to optimize
NumberOfFields to use a O(1) algorithm :-)

+
+  if (has_field) {
+    HValue* object_properties =
+        AddInstruction(new(zone) HInnerAllocatedObject(target, object_offset));
+    BuildEmitInObjectProperties(boilerplate_object, original_boilerplate_object,
+        object_properties, target, offset, data_target, data_offset);
+  }
 
   // Create allocation site info.
   if (mode == TRACK_ALLOCATION_SITE &&