Use "isa" since the variable isn't used.

llvm-svn: 367985
diff --git a/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp b/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp
index f55f6f9..e4f29fb 100644
--- a/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp
+++ b/llvm/lib/Target/BPF/BPFAbstractMemberAccess.cpp
@@ -311,7 +311,7 @@
 
   // Child is a derived/pointer type, which is due to type casting.
   // Pointer type cannot be in the middle of chain.
-  if (const auto *PtrTy = dyn_cast<DIDerivedType>(CType))
+  if (isa<DIDerivedType>(CType))
     return false;
 
   // Parent is a pointer type.