[llvm] [CodeGen] Fix stale LiveIntervals regmask tables after MachineBasicBl… (PR #209610)

[Nathan Corbyn via llvm-commits]

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@@ -482,6 +492,19 @@ class LiveIntervals {
   /// Compute RegMaskSlots and RegMaskBits.
   void computeRegMasks();
 
+  /// Shared implementation of insertMBBInMaps(). When \p AssumeRegMaskEmpty is
+  /// true, \p MBB must contain no regmask operands. splitAt() passes false
+  /// because it inserts a block already populated with regmask-bearing
+  /// instructions and fixes up the regmask slices via reassignRegMaskSlots().
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cofibrant wrote:

```suggestion
  /// true, \p MBB must contain no regmask operands.
```
Is an LLM writing these comments? Can't we just keep it simple?

https://github.com/llvm/llvm-project/pull/209610