[llvm] [MachineBasicBlock] Fix use after free in SplitCriticalEdge (PR #68786)

[Matthias Braun via llvm-commits]

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@@ -1097,6 +1097,31 @@ static bool jumpTableHasOtherUses(const MachineFunction &MF,
   return false;
 }
 
+class MBBSplitCriticalEdgeDelegate : public MachineFunction::Delegate {
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MatzeB wrote:

Call this `SlotIndexUpdateDelegate` or similar? (as it doesn't seem very specific to splitting critical edges now.

https://github.com/llvm/llvm-project/pull/68786