[llvm] [LoopPeel] Fix branch weights' effect on block frequencies (PR #128785)

[Joel E. Denny via llvm-commits]

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@@ -7866,6 +7866,17 @@ The attributes in this metadata is added to all followup loops of the
 loop distribution pass. See
 :ref:`Transformation Metadata <transformation-metadata>` for details.
 
+'``llvm.loop.estimated_trip_count``' Metadata
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jdenny-ornl wrote:

In the other loop metadata, I understood `.` to separate levels in a naming hierarchy while `_` separates words in a single level's name.

For example: [‘llvm.loop.unroll_and_jam.count’ Metadata](https://llvm.org/docs/LangRef.html#llvm-loop-unroll-and-jam-count-metadata)

I didn't think of any way to break `estimated_trip_count` apart into a meaningful hierarchy.

Thanks for reviewing.  I'll work on your other comments.

https://github.com/llvm/llvm-project/pull/128785