================
@@ -2628,6 +2630,87 @@ 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 x, 0) -> x
+ if (isNullConstant(N1))
+ return N0;
+
+ // fold (ptradd 0, x) -> x
+ if (isNullConstant(N0) && PtrVT == IntVT)
+ return N1;
----------------
ritter-x2a wrote:
Yes, @arichardson argued for adding it redundantly here in [a thread
below](https://app.graphite.dev/github/pr/llvm/llvm-project/142739/%5BAMDGPU%5D%5BSDAG%5D-Add-ISD-PTRADD-DAG-combines#comment-PRRC_kwDOBITxeM5_IBA7),
to highlight this constraint more explicitly for when the assertion might be
relaxed in the future.
https://github.com/llvm/llvm-project/pull/142739
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