DAGCombiner: Simplify inverted bit tests
Fold (xor (and x, y), y) -> (and (not x), y)
This removes an opportunity for a constant to appear twice.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@181395 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 2e09ec0..700ee12 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3460,6 +3460,15 @@
return DAG.getNode(NewOpcode, N->getDebugLoc(), VT, LHS, RHS);
}
}
+ // fold (xor (and x, y), y) -> (and (not x), y)
+ if (N0.getOpcode() == ISD::AND && N0.getNode()->hasOneUse() &&
+ N0->getOperand(1) == N1) {
+ SDValue X = N0->getOperand(0);
+ SDValue NotX = DAG.getNode(ISD::XOR, X.getDebugLoc(), VT, X,
+ DAG.getConstant(APInt::getAllOnesValue(VT.getSizeInBits()), VT));
+ AddToWorkList(NotX.getNode());
+ return DAG.getNode(ISD::AND, N->getDebugLoc(), VT, NotX, N1);
+ }
// fold (xor (xor x, c1), c2) -> (xor x, (xor c1, c2))
if (N1C && N0.getOpcode() == ISD::XOR) {
ConstantSDNode *N00C = dyn_cast<ConstantSDNode>(N0.getOperand(0));