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

[Matt Arsenault via llvm-commits]

================
@@ -1502,6 +1502,11 @@ enum NodeType {
   // Outputs: [rv], output chain, glue
   PATCHPOINT,
 
+  // PTRADD represents pointer arithmatic semantics, for targets that opt in
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arsenm wrote:

```suggestion
  // PTRADD represents pointer arithmetic semantics, for targets that opt in
```

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