[PATCH] D42986: [TargetLowering] try to create -1 constant operand for math ops via demanded bits

[Craig Topper via Phabricator via llvm-commits]

craig.topper added inline comments.


================
Comment at: lib/CodeGen/SelectionDAG/TargetLowering.cpp:1246
+      SDValue Neg1 = TLO.DAG.getAllOnesConstant(dl, VT);
+      SDValue NewMath = TLO.DAG.getNode(Op.getOpcode(), dl, VT, Op0, Neg1);
+      return TLO.CombineTo(Op, NewMath);
----------------
Do we need to do anything with NSW/NUW flags?


https://reviews.llvm.org/D42986