[llvm] [AMDGPU] Add DS loop wait optimization infrastructure (1/4) (PR #171942)

[Matt Arsenault via llvm-commits]

================
@@ -573,6 +596,10 @@ class SIInsertWaitcnts {
                              WaitcntBrackets &ScoreBrackets);
   bool insertWaitcntInBlock(MachineFunction &MF, MachineBasicBlock &Block,
                             WaitcntBrackets &ScoreBrackets);
+
+  // DS loop wait optimization functions
+  bool isEligibleForDSLoopOpt(MachineLoop *ML, LoopDSWaitOptInfo &Info) const;
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arsenm wrote:

```suggestion
  bool isEligibleForDSLoopOpt(const MachineLoop &ML, LoopDSWaitOptInfo &Info) const;
```

https://github.com/llvm/llvm-project/pull/171942