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

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HaohaiWen 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 [#68502 (comment)](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.

Oh... sorry, I made a wrong IR example.
The real case looks like this: https://alive2.llvm.org/ce/z/-DXnJc
Both %x and %y are i16. The first or/fshl swaps half of of i32. The rest swaps byte, 4bit, 2bit.
I extended the fshl transformation to apply for both symmetric and asymmetric combination.



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