[llvm] [MachineBasicBlock] Fix use after free in SplitCriticalEdge (PR #66188)

[Carl Ritson via llvm-commits]

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@@ -693,15 +693,15 @@ void MachineBasicBlock::updateTerminator(
   MachineBasicBlock *TBB = nullptr, *FBB = nullptr;
   SmallVector<MachineOperand, 4> Cond;
   DebugLoc DL = findBranchDebugLoc();
-  bool B = TII->analyzeBranch(*this, TBB, FBB, Cond);
+  bool B = TII->analyzeBranch(*this, TBB, FBB, Cond, /*AllowModify=*/false);
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perlfu wrote:

This is NFC, but I felt it was appropriate to add an explicit configuration of AllowModify=false here as SlotIndexes will be invalidated if analyzeBranch modifies the instructions.

https://github.com/llvm/llvm-project/pull/66188