[llvm] [SelectionDAG] Introduce ISD::PTRADD (PR #140017)

[Fabian Ritter via llvm-commits]

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@@ -2388,7 +2391,7 @@ static bool canFoldInAddressingMode(SDNode *N, SDNode *Use, SelectionDAG &DAG,
   }
 
   TargetLowering::AddrMode AM;
-  if (N->getOpcode() == ISD::ADD) {
+  if (N->getOpcode() == ISD::ADD || N->getOpcode() == ISD::PTRADD) {
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ritter-x2a wrote:

Thanks for looking into this! The original PR, from which this is extracted, is from an effort to support an AArch64 memory safety ISA extension; I strongly suspect that supporting ARM's pre-indexed addressing mode in the presence of PTRADD was the motivation for this line. If this is too ARM-specific to be included in this PR, I can drop it and leave it for @rgwott to include in the updated #105669.

https://github.com/llvm/llvm-project/pull/140017