[PATCH] D33391: [DAGCombine] fold (add/uaddo (xor a, -1), 1) -> (sub 0, a)

[Amaury SECHET via Phabricator via llvm-commits]

deadalnix added inline comments.


================
Comment at: lib/CodeGen/SelectionDAG/DAGCombiner.cpp:2095
+    return DAG.getNode(ISD::USUBO, DL, N->getVTList(),
+                       DAG.getConstant(0, DL, VT), N0.getOperand(0));
+
----------------
efriedma wrote:
> Are you sure this sets the overflow bit correctly?
You made me doubt, so I put some test together, and it does indeed overflow correctly.


https://reviews.llvm.org/D33391