[llvm] [AMDGPU][SIInsertWaitcnts] Track SCC. Insert KM_CNT waits for SCC writes. (PR #157843)

[Petar Avramovic via llvm-commits]

petar-avramovic wrote:

### Merge activity

* **Sep 18, 12:39 PM UTC**: A user started a stack merge that includes this pull request via [Graphite](https://app.graphite.dev/github/pr/llvm/llvm-project/157843).


https://github.com/llvm/llvm-project/pull/157843