[llvm] [LoopIdiom] Use costing to determine CRC strategy (PR #211040)

[Piotr Fusik via llvm-commits]

pfusik wrote:

> I may need some guidance regarding the behavior under optsize

CRC is normally a very small part of a program and we shouldn't over-engineer. I'd measure the code size for our tests and gather it in a table. This data should help us choose a simple strategy, even if it's suboptimal by a few bytes.

https://github.com/llvm/llvm-project/pull/211040