[llvm] [AMDGPU] Cgscc amdgpu attributor (PR #179719)

[Shilei Tian via llvm-commits]

shiltian wrote:

Like I mentioned earlier, most of the attributes in AMDGPUAttributor were designed and implemented to run as a module pass. This is not about whether we can or can't run them as a CGSCC pass. It is about correctness. Some attributes might still produce correct results in a CGSCC pass, but they could be suboptimal. For them, it is less concerning. However, unless we split them up or rewrite them so that partial information still gives correct, even if suboptimal, results, we can't simply run the whole thing as a CGSCC pass.

https://github.com/llvm/llvm-project/pull/179719