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

[Jay Foad via llvm-commits]

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@@ -1145,6 +1172,8 @@ void WaitcntBrackets::print(raw_ostream &OS) const {
           OS << RelScore << ":s" << J << " ";
         }
       }
+      if (T == KM_CNT && SCCScore > 0)
+        OS << SCCScore << ":SCC ";
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jayfoad wrote:

Nit:
```suggestion
        OS << SCCScore << ":scc ";
```

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