[llvm] [clang] [clang-tools-extra] [InstCombine] Convert or concat to fshl if opposite or concat exists (PR #68502)

[Nikita Popov via cfe-commits]

nikic wrote:

Yes, I understand that this transform is only a step towards handling the full pattern. I'm asking for a complete, working example of the original motivating case. The snippets posted in https://github.com/llvm/llvm-project/pull/68502#discussion_r1351618002 do not appear to be correct, or I failed to assemble them correctly. Please provide complete src and tgt functions that verify with alive2.

https://github.com/llvm/llvm-project/pull/68502