[clang] [llvm] [AMDGPU] Introduce GFX9/10.1/10.3/11 Generic Targets (PR #76955)

[Matt Arsenault via cfe-commits]

https://github.com/arsenm commented:

I think this needs codegen tests for the gfx900 vs. gfx906 mad_mix/fma_fix issue 

https://github.com/llvm/llvm-project/pull/76955