[llvm] [AMDGPU][MachineScheduler] Alternative way to control excess RP. (PR #68004)

[Jeffrey Byrnes via llvm-commits]

================
@@ -1127,16 +1133,23 @@ bool OccInitialScheduleStage::shouldRevertScheduling(unsigned WavesAfter) {
 bool UnclusteredHighRPStage::shouldRevertScheduling(unsigned WavesAfter) {
   // If RP is not reduced in the unclustered reschedule stage, revert to the
   // old schedule.
-  if ((WavesAfter <= PressureBefore.getOccupancy(ST) &&
-       mayCauseSpilling(WavesAfter)) ||
-      GCNSchedStage::shouldRevertScheduling(WavesAfter)) {
-    LLVM_DEBUG(dbgs() << "Unclustered reschedule did not help.\n");
-    return true;
-  }
+  if (DAG.RegionsWithExcessRP[RegionIdx]) {
----------------
jrbyrnes wrote:

After https://github.com/llvm/llvm-project/commit/113052b2b022c4ce45c8003057ae4297d48ed843 , RP.less has excess RP comparisons that this should be consistent with:

```
return (NewVGPRRP > S.VGPRExcessLimit || NewAGPRRP > S.AGPRExcessLimit 
			|| NewSGPRRP > S.SGPRExcessLimit 
			|| /* Unified VGPR excess case */ ) 
			&&  !PressureAfter.less(ST, PressureBefore);
```

https://github.com/llvm/llvm-project/pull/68004