[llvm] [X86] Implement CRC32 const folding (PR #219452)

[Phoebe Wang via llvm-commits]

phoebewang wrote:

> [d836261](https://github.com/llvm/llvm-project/commit/d836261ca3c9ceffd550cc40c22bab5afa69e612) also does CRC calculation in a couple of files. I'm not sure if I should refactor the existing code to have a common crc_calc routine which can be called. If this should be done, then do let me know which file to have the routine as well so that code can be reused.

No idea how to share the code, but you do need to make the test input more random like that :)

https://github.com/llvm/llvm-project/pull/219452