Declare Sentinel fragments as mutable to get rid

of some pointless casting. This fragment logically
does not belong to ilist anyway, but to "ghostly"
NodeType.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@65843 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/BasicBlock.h

@@ -38,14 +38,14 @@ template<> struct ilist_traits<Instruction>
     // NodeTy, which becomes the sentinel. Dereferencing the sentinel is
     // forbidden (save the ilist_node<NodeTy>) so no one will ever notice
     // the superposition.
-    return const_cast<Instruction*>(static_cast<const Instruction*>(&Sentinel));
+    return static_cast<Instruction*>(&Sentinel);
   }
   static void destroySentinel(Instruction*) {}
   static iplist<Instruction> &getList(BasicBlock *BB);
   static ValueSymbolTable *getSymTab(BasicBlock *ItemParent);
   static int getListOffset();
 private:
-  ilist_node<Instruction> Sentinel;
+  mutable ilist_node<Instruction> Sentinel;
 };
 
 /// This represents a single basic block in LLVM. A basic block is simply a