[AMDGPU][Scheduler] Fix non-monotonic SlotIndex after schedule revert (#192039) modifyRegionSchedule restores the original instruction order by splicing MIs before RegionEnd. When an MI is already at the expected position (MII == RegionEnd) its SlotIndex was left unchanged, even though earlier splices may have shifted neighboring indices. This could leave a stale, lower-numbered slot on a non-moved MI, breaking SlotIndex monotonicity and corrupting LiveIntervals. The corruption surfaced as a "register isn't live" assertion in GCNDownwardRPTracker when PreRARematStage's finalizeGCNSchedStage globally reverted regions that were already locally reverted by checkScheduling. Fix by calling LIS->handleMove for non-moved MIs whose SlotIndex has become non-monotonic (PrevIdx >= MI_Idx). Additionally, track whether checkScheduling already reverted a region and skip the redundant global revert in finalizeGCNSchedStage. Assisted-by: Claude Opus
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