Remove unnecessary classof()'s

isa<> et al. automatically infer when the cast is an upcast (including a
self-cast), so these are no longer necessary.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165767 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Bitcode/Reader/BitcodeReader.cpp

@@ -211,7 +211,6 @@ namespace {
     }
 
     /// @brief Methods to support type inquiry through isa, cast, and dyn_cast.
-    //static inline bool classof(const ConstantPlaceHolder *) { return true; }
     static bool classof(const Value *V) {
       return isa<ConstantExpr>(V) &&
              cast<ConstantExpr>(V)->getOpcode() == Instruction::UserOp1;