[llvm] [LV]: Teach LV to recursively (de)interleave. (PR #89018)

[Mel Chen via llvm-commits]

Mel-Chen wrote:

Would it be possible to directly add (de)interleave intrinsic 4 to achieve this? Such an implementation should be simpler and more maintainable. 
Using prime factor (de)interleave intrinsics to combine non-prime interleave factors would only be effective in saving the number of intrinsics needed when supporting large interleave factors. 
For RISCV, the current largest factor is 8. (Not sure if other targets support larger factors.)

https://github.com/llvm/llvm-project/pull/89018