[llvm] [AMDGPU] New AMDGPUInsertSingleUseVDST pass (PR #72388)

[Jay Foad via llvm-commits]

jayfoad wrote:

> I am unsure about the test coverage here because there are barely any tests covering wide registers or subregister access. Based on the TODO comment about MCRegUnits I guess these may not work correctly yet? Even so it might be good to have tests that show what doesn't work, so that future patches can demonstrate improvements.
> 
> I although think many of the liveins for blocks in the test can be shorten or removed. I have annotate a few as examples.

I have completely redone the tests now, simplifying as much as I could, commenting them, and adding some tests for 64-bit and 16-bit registers. Please take another look!

https://github.com/llvm/llvm-project/pull/72388