Supporting AllocationSiteInfo for Nested arrays

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index 18894c1d56123f99fe02df5967ea06ffdac8a857..6b4e68acd971b27a93f9f25e044be0ebb0270005 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -1461,6 +1461,13 @@ MaybeObject* JSObject::ResetElements() {
 }
 
 
+bool JSObject::ShouldTrackAllocationInfo() {

[danno, 2013/02/11 15:05:21]

How abound adding:

if (!IsJSArray()) return true;

This centralizes the policy for tracking on all objects to this function,
hopefully obviating the need for the extra IsJSArray check at the caller sites
(please update those, too).

[mvstanton, 2013/02/15 07:36:43]

Done.

+  if (map()->CanTrackAllocationSite()) {
+    return true;
+  }
+  return false;
+}
+
 MaybeObject* JSObject::AddFastPropertyUsingMap(Map* map) {
   ASSERT(this->map()->NumberOfOwnDescriptors() + 1 ==
          map->NumberOfOwnDescriptors());
@@ -5625,6 +5632,13 @@ void JSArray::EnsureSize(int required_size) {
 }
 
 
+bool JSArray::ShouldTrackAllocationInfo() {

[danno, 2013/02/11 15:05:21]

I'm a little confused how JSArray::ShouldTrackAllocationInfo differs from
JSObject::ShouldTrackAllocation info. If possible, I think JSObject's version
should "do it all", i.e. even casting to JSArray and check the GetMode result on
GetElementsKind(). The idea is that there is a single method on JSObject that
returns whether the SiteAllocationInfo should be allocated without doing any
additional checks on the object's instance type.

[mvstanton, 2013/02/15 07:36:43]

I was thinking in terms of virtual overrides, where some object might bring
other factors into the decision. In the case of JSArray, it's a check on
ElementsKind...for other objects maybe it would be something different. I'll
consolidate this under JSObject, thx.

+  ASSERT(map()->CanTrackAllocationSite());
+  AllocationSiteMode mode = AllocationSiteInfo::GetMode(GetElementsKind());
+  return mode == TRACK_ALLOCATION_SITE;
+}
+
+
 void JSArray::set_length(Smi* length) {
   // Don't need a write barrier for a Smi.
   set_length(static_cast<Object*>(length), SKIP_WRITE_BARRIER);