[clang] [clang] Avoid evaluating the BitWidth expression over and over again (PR #66203)

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https://github.com/cor3ntin requested changes to this pull request.

I knew there was a deja-vu here :)

I'd rather we do the general solution then. Maybe we should pursue the discussion on phab. I can't imagine the general solution is going to ever be noticeably worse.

I have the possibility to push a branch here http://llvm-compile-time-tracker.com/
@AaronBallman 




https://github.com/llvm/llvm-project/pull/66203