[llvm] [CodeGen] Use optimized domtree for MachineFunction (PR #102107)

[Nikita Popov via llvm-commits]

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@@ -293,6 +293,10 @@ class LLVM_EXTERNAL_VISIBILITY MachineFunction {
   // numbered and this vector keeps track of the mapping from ID's to MBB's.
   std::vector<MachineBasicBlock*> MBBNumbering;
 
+  // MBBNumbering epoch, incremented after renumbering to detect use of old
+  // block numbers.
+  unsigned MBBNumberingEpoch;
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nikic wrote:

```suggestion
  unsigned MBBNumberingEpoch = 0;
```
Maybe I missed it somewhere, but I think this is uninitialized?

https://github.com/llvm/llvm-project/pull/102107