A change in the way we place TransitionElementKinds in the tree.

src/elements-kind.cc

Index: src/elements-kind.cc
diff --git a/src/elements-kind.cc b/src/elements-kind.cc
index 7b1651a953fc8120f4c1a29fcb9bef77c330e62c..792c334286c36aa060ae1dd53d9ec09f5a65e4da 100644
--- a/src/elements-kind.cc
+++ b/src/elements-kind.cc
@@ -136,4 +136,27 @@ bool IsMoreGeneralElementsKindTransition(ElementsKind from_kind,
 }
 
 
+ElementsKind GetUnifiedFastElementsKind(ElementsKind e1, ElementsKind e2) {
+  ASSERT(IsFastElementsKind(e1));
+  ASSERT(IsFastElementsKind(e2));  

[danno, 2012/11/14 15:28:18]

I think you can simplify this code:

int i1 = GetSequenceIndexFromFastElementsKind(e1);
int i2 = GetSequenceIndexFromFastElementsKind(e2);

ElementsKind result = GetFastElementsKindFromSequenceIndex(max(i1, i2);
return ((IsFastHoleyElementKind(e1) != IsFastHoleyElementsKind(e2))
 ? GetHoleyElementsKind(result)
 : result;

[mvstanton, 2012/11/16 15:15:06]

Done.

+  if (e1 == e2) {
+    return e1;
+  }
+  
+  int i1 = GetSequenceIndexFromFastElementsKind(e1);
+  int i2 = GetSequenceIndexFromFastElementsKind(e2);
+  ASSERT(i1 != i2);
+  int max = i1 > i2 ? i1 : i2;
+  int min = i1 < i2 ? i1 : i2;
+  // The only reason not to take the max as the result is if the max is packed and the
+  // min is holey
+  ElementsKind eMax = GetFastElementsKindFromSequenceIndex(max);
+  ElementsKind eMin = GetFastElementsKindFromSequenceIndex(min);
+  if (IsFastPackedElementsKind(eMax) && !IsFastPackedElementsKind(eMin)) {
+    return GetNextMoreGeneralFastElementsKind(eMin, false);
+  }
+  return eMax;
+}
+
+
 } }  // namespace v8::internal