Pretenuring calculation fields in AllocationSite.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 267ef133abc43373b84b02fbd9c3e8e63b2ce85a..4bddefbf76ef689309e1677aa85e0d2e10ffe76e 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -8020,6 +8020,9 @@ class AllocationSite: public Struct {
   // walked in a particular order. So [[1, 2], 1, 2] will have one
   // nested_site, but [[1, 2], 3, [4]] will have a list of two.
   DECL_ACCESSORS(nested_site, Object)
+  DECL_ACCESSORS(memento_found_count, Smi)
+  DECL_ACCESSORS(memento_create_count, Smi)

[Hannes Payer (out of office), 2013/10/28 10:46:54]

If we encounter that allocation sites are getting too big, we could just use
half a word for the found and create count.

[mvstanton, 2013/10/28 11:29:28]

I actually had something like this for a while, but pulled it out for lack of
evidence in favor of simplicity. How about we'll recognize that the field layout
may be wasteful, or have cache line issues, at the moment we are testing these.
(very soon, but not yet).

+  DECL_ACCESSORS(pretenure_decision, Smi)

[Hannes Payer (out of office), 2013/10/28 10:46:54]

Hmm, maybe this is good enough for this CL but I think this should become a more
general pretenure_status field, where we encode the current state of pretenuring
for the given allocation site:
1-Bit bool pretenure yes/no
3-Bits decision counter, how many times have we changed our mind to pretenure.
If we have done that too often, we should probably stop emitting mementos.
Maybe more stuff... Again, if size is not a problem we can have separate fields
which feel a bit wasteful.

   DECL_ACCESSORS(dependent_code, DependentCode)
   DECL_ACCESSORS(weak_next, Object)
 
@@ -8059,7 +8062,13 @@ class AllocationSite: public Struct {
 
   static const int kTransitionInfoOffset = HeapObject::kHeaderSize;
   static const int kNestedSiteOffset = kTransitionInfoOffset + kPointerSize;
-  static const int kDependentCodeOffset = kNestedSiteOffset + kPointerSize;
+  static const int kMementoFoundCountOffset = kNestedSiteOffset + kPointerSize;
+  static const int kMementoCreateCountOffset =
+      kMementoFoundCountOffset + kPointerSize;
+  static const int kPretenureDecisionOffset =
+      kMementoCreateCountOffset + kPointerSize;
+  static const int kDependentCodeOffset =
+      kPretenureDecisionOffset + kPointerSize;
   static const int kWeakNextOffset = kDependentCodeOffset + kPointerSize;
   static const int kSize = kWeakNextOffset + kPointerSize;