[llvm] [AMDGPU] Fix GFX1250 hazard: S_SET_VGPR_MSB dropped (PR #184904)

[Stanislav Mekhanoshin via llvm-commits]

rampitec wrote:

> > Either move mitigation into the VGPR lowering itself (easy), or change pass ordering and prove nothing will break (hard).
> 
> @rampitec can you make a decision on which approach to use? I can't decide because I don't know about the "very good reason" for running VGPR lowering after the hazard recognizer.

For one there are some hazard mitigations which create new VGPR uses. For the most part back then pass design was different and lowering was replacing actual registers with v0-v255 which is not a concern now.

https://github.com/llvm/llvm-project/pull/184904