[llvm] [AMDGPU][Scheduler] Fix non-monotonic SlotIndex after schedule revert (PR #192039)

[Lucas Ramirez via llvm-commits]

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@@ -717,11 +720,14 @@ class PreRARematStage : public GCNSchedStage {
     std::vector<MachineInstr *> OrigMIOrder;
     /// Maximum pressure recorded in the region.
     GCNRegPressure MaxPressure;
+    /// Whether the region was already reverted by per-region checkScheduling.
+    bool AlreadyReverted = false;
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lucas-rami wrote:

This is handled by `PreRARematStage::RevertAllRegions` since a recent commit ([42127fa](https://github.com/llvm/llvm-project/commit/42127fa2775ca9102d4be00cafbe0fcd6f25299d)), so it's not necessary here.

https://github.com/llvm/llvm-project/pull/192039