Use proper return type for attribute index.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173638 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/IR/AttributeImpl.h b/lib/IR/AttributeImpl.h
index babc14e..f9a716c 100644
--- a/lib/IR/AttributeImpl.h
+++ b/lib/IR/AttributeImpl.h
@@ -137,7 +137,7 @@
   /// is the index of the return, parameter, or function object that the
   /// attributes are applied to, not the index into the AttrNodes list where the
   /// attributes reside.
-  unsigned getSlotIndex(unsigned Slot) const { return AttrNodes[Slot].first; }
+  uint64_t getSlotIndex(unsigned Slot) const { return AttrNodes[Slot].first; }
 
   /// \brief Retrieve the attributes for the given "slot" in the AttrNode list.
   /// \p Slot is an index into the AttrNodes list, not the index of the return /