[llvm] [SimplifyCFG] Do not run `simplifySwitchOfPowersOfTwo` in early invocations (PR #145477)

[Nikita Popov via llvm-commits]

nikic wrote:

> > Can you please add a PhaseOrdering test that demonstrates why this is useful?
> 
> To simply confirm this, as a PhaseOrdering test, do you have in mind a reduced version of `_ZN8zvariant19framing_offset_size17FramingOffsetSize12write_offset17h7af96b41ab784441E` (bench/zed-rs/original/8bnapxt4ilkd5y3egr7fzm1sv.ll, where the regression appears), and test it with default O2, correct?

Yes

https://github.com/llvm/llvm-project/pull/145477