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

[Jay Foad via llvm-commits]

jayfoad wrote:

Sorry I have probably missed some prior discussion on this, but: is the difference between ISD::ADD and ISD::PTRADD meaningful for _any_ of our selection patterns? If not, could we leave the selection patterns as they are and instead replace PTRADD with ADD before selection (either as a legalization, or some other custom way of doing it).

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