[TargetLowering] Use dropFlags API. NFC.

Author: dtcxzyw

llvm/lib/CodeGen/SelectionDAG/TargetLowering.cpp

@@ -2560,13 +2560,9 @@ bool TargetLowering::SimplifyDemandedBits(
     APInt TruncMask = DemandedBits.zext(OperandBitWidth);
     if (SimplifyDemandedBits(Src, TruncMask, DemandedElts, Known, TLO,
                              Depth + 1)) {
-      if (Flags.hasNoSignedWrap() || Flags.hasNoUnsignedWrap()) {
-        // Disable the nsw and nuw flags. We can no longer guarantee that we
-        // won't wrap after simplification.
-        Flags.setNoSignedWrap(false);
-        Flags.setNoUnsignedWrap(false);
-        Op->setFlags(Flags);
-      }
+      // Disable the nsw and nuw flags. We can no longer guarantee that we
+      // won't wrap after simplification.
+      Op->dropFlags(SDNodeFlags::NoWrap);
       return true;
     }
     Known = Known.trunc(BitWidth);