[llvm] [INSTR COMBINE] implement combine select into cast (PR #114612)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

Please take a look at https://llvm.org/docs/InstCombineContributorGuide.html for guidelines for contributing to InstCombine, esp regarding proofs and tests.

But even before that, wasn't the consensus from https://github.com/llvm/llvm-project/issues/107034 that this is better handled in the backend on the SDAG level, rather than in InstCombine?

https://github.com/llvm/llvm-project/pull/114612