[llvm] [AMDGPU][SDAG] Handle ISD::PTRADD in VOP3 patterns (PR #143881)

[Fabian Ritter via llvm-commits]

ritter-x2a wrote:

### Merge activity

* **Sep 18, 1:00 PM UTC**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/143881).


https://github.com/llvm/llvm-project/pull/143881