[clang] [llvm] [AMDGPU] Extend readlane, writelane and readfirstlane intrinsic lowering for generic types (PR #89217)

[Vikram Hegde via cfe-commits]

vikramRH wrote:

> > > > @jayfoad's testcase fails and the same test should be repeated for all 3 intrinsics
> > > 
> > > 
> > > added MIR tests for 3 intrinsics. The issue is that Im not able to attach the glue nodes to newly created laneop pieces since they fail at selection. #87509 should enable this,
> > 
> > 
> > I am not really comfortable waiting for #87509 to fix convergence tokens in this expansion. Is it really true that this expansion cannot be fixed independent of future work on `CONVERGENCE_GLUE`? There is no way to manually handle the same glue operands??
> 
> I guess one way would be to have custom selection for each of the new node type introduced, but would this be a proper way forward ? (this would be in general for all convergent SDNodes i guess if selection is not made generic)

Or drop the new nodes altogether and legelaize to intrinsics directly ?

https://github.com/llvm/llvm-project/pull/89217