Address nikic's comment

Author: tclin914

llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

@@ -1869,9 +1869,10 @@ Instruction *InstCombinerImpl::foldCastedBitwiseLogic(BinaryOperator &I) {
 
     // Do the logic op in the intermediate width, then widen more.
     Value *NarrowLogic = Builder.CreateBinOp(LogicOpc, X, Y, I.getName());
-    if (auto *Disjoint = dyn_cast<PossiblyDisjointInst>(&I);
-        Disjoint && Disjoint->isDisjoint())
-      cast<PossiblyDisjointInst>(NarrowLogic)->setIsDisjoint(true);
+    auto *Disjoint = dyn_cast<PossiblyDisjointInst>(&I);
+    auto *NewDisjoint = dyn_cast<PossiblyDisjointInst>(NarrowLogic);
+    if (Disjoint && NewDisjoint)
+      NewDisjoint->setIsDisjoint(Disjoint->isDisjoint());
     return CastInst::Create(CastOpcode, NarrowLogic, DestTy);
   }