Allow FastCloneShallowObjectStub to use AllocationMementos.

src/code-stubs.h

Index: src/code-stubs.h
diff --git a/src/code-stubs.h b/src/code-stubs.h
index d2101ae293b6cee60ef3ca597bc483ab9b4d18ba..2fadce35a0561d6d427689cc716f85bd62c59713 100644
--- a/src/code-stubs.h
+++ b/src/code-stubs.h
@@ -673,13 +673,18 @@ class FastCloneShallowObjectStub : public HydrogenCodeStub {
   // Maximum number of properties in copied object.
   static const int kMaximumClonedProperties = 6;
 
-  explicit FastCloneShallowObjectStub(int length)
-      : length_(length) {
+  FastCloneShallowObjectStub(AllocationSiteMode allocation_site_mode,

[Michael Starzinger, 2013/10/10 13:27:39]

As discussed offline: I don't think it makes much sense to keep the
allocation_site as part of the minor key because it's value is statically
chosen. I don't (yet) see a use-case where we need more that one stub per
length. Let's drop that and decide whether to tack allocations when we compile
the stub.

[mvstanton, 2013/10/10 14:09:04]

Good comment, I added FLAG_allocation_site_pretenuring to express this,
currently turned off.

+                             int length)
+      : allocation_site_mode_(allocation_site_mode),
+        length_(length) {
     ASSERT_GE(length_, 0);
     ASSERT_LE(length_, kMaximumClonedProperties);
   }
 
   int length() const { return length_; }
+  AllocationSiteMode allocation_site_mode() const {
+    return allocation_site_mode_;
+  }
 
   virtual Handle<Code> GenerateCode(Isolate* isolate);
 
@@ -688,10 +693,20 @@ class FastCloneShallowObjectStub : public HydrogenCodeStub {
       CodeStubInterfaceDescriptor* descriptor);
 
  private:
+  AllocationSiteMode allocation_site_mode_;
   int length_;
 
+  class AllocationSiteModeBits: public BitField<AllocationSiteMode, 0, 1> {};
+  class LengthBits: public BitField<int, 1, 4> {};
+  // Ensure data fits within available bits.
+  STATIC_ASSERT(LAST_ALLOCATION_SITE_MODE == 1);
+  STATIC_ASSERT(kMaximumClonedProperties < 16);
+
   Major MajorKey() { return FastCloneShallowObject; }
-  int NotMissMinorKey() { return length_; }
+  int NotMissMinorKey() {
+    return AllocationSiteModeBits::encode(allocation_site_mode_)
+        | LengthBits::encode(length_);
+  }
 
   DISALLOW_COPY_AND_ASSIGN(FastCloneShallowObjectStub);
 };