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

[Fabian Ritter via llvm-commits]

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@@ -469,9 +470,13 @@ class TargetMachine {
   }
 
   /// True if target has some particular form of dealing with pointer arithmetic
-  /// semantics. False if pointer arithmetic should not be preserved for passes
-  /// such as instruction selection, and can fallback to regular arithmetic.
-  virtual bool shouldPreservePtrArith(const Function &F) const { return false; }
+  /// semantics for pointers with the given value type. False if pointer
+  /// arithmetic should not be preserved for passes such as instruction
+  /// selection, and can fallback to regular arithmetic.
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ritter-x2a wrote:

Unless we add a DAGCombine that replaces ptradd with add (which would need a similar option to disable for backends that want to handle ptradd properly), modifying existing backends to use ptradd without causing regressions is a significant effort (that's at least my experience from working on it for AMDGPU).
Should I add an "This should be removed when PTRADD nodes are widely supported by backends." comment to the function?

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