[llvm] [MachineScheduler] Add option to skip large regions with high pressure (PR #178422)

[Francesco Petrogalli via llvm-commits]

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@@ -218,6 +218,11 @@ struct MachineSchedPolicy {
   // Compute DFSResult for use in scheduling heuristics.
   bool ComputeDFSResult = false;
 
+  // Skip scheduling for large regions with critical register pressure.
+  // When a region has more instructions than this threshold and register
+  // pressure exceeds limits, scheduling is skipped. 0 disables this feature.
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fpetrogalli wrote:

what would be these limits? just !empty RegionCriticalPSets?

https://github.com/llvm/llvm-project/pull/178422