================
@@ -2627,6 +2629,93 @@ SDValue DAGCombiner::foldSubToAvg(SDNode *N, const SDLoc
&DL) {
return SDValue();
}
+/// Try to fold a pointer arithmetic node.
+/// This needs to be done separately from normal addition, because pointer
+/// addition is not commutative.
+SDValue DAGCombiner::visitPTRADD(SDNode *N) {
+ SDValue N0 = N->getOperand(0);
+ SDValue N1 = N->getOperand(1);
+ EVT PtrVT = N0.getValueType();
+ EVT IntVT = N1.getValueType();
+ SDLoc DL(N);
+
+ // This is already ensured by an assert in SelectionDAG::getNode(). Several
+ // combines here depend on this assumption.
+ assert(PtrVT == IntVT &&
+ "PTRADD with different operand types is not supported");
+
+ // fold (ptradd undef, y) -> undef
+ if (N0.isUndef())
----------------
ritter-x2a wrote:
I've added some in the `ptradd-sdag-undef-poison.ll` test. Can't have them diff
nicely like the other tests because the folds are already enabled on trunk, but
I did verify that additions are generated if the folds are disabled again.
We obviously need to ignore the undef deprecator github action for this test
(or should I limit it to poison?).
https://github.com/llvm/llvm-project/pull/142739
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