[llvm] [BOLT][AArch64] Add support for compact code model (PR #112110)

[Paschalis Mpeis via llvm-commits]

https://github.com/paschalis-mpeis approved this pull request.

Hey Maks, thanks a for the update. Compact mode looks good.

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I'm not sure how LongJump might evolve in the future from code design point of view.
eg, if JITLink does relaxation for >128MB, then we may have 'Tentative Mode' (the original LongJmp pass) and 'Non-Tentative/Local Mode' (the evolution of compact-mode).

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Re code size decreases:
> I don't think we have such expectation. Just something I've noticed.

Okay thanks. Quickly comparing sizes of a single binary (~55MB of text) in compact mode versus the updated LongJmp (#96609):
- cold section had the same size
- LongJmp's hot section was smaller, I guess due to hot stub sharing (sharing has more than doubled since #96609)


https://github.com/llvm/llvm-project/pull/112110