[llvm] [InstCombine] Fold more 'fcmp' 'select' instrs idioms into 'fabs' (PR #83381)

[Nikita Popov via llvm-commits]

nikic wrote:

(FWIW, I agree with @jcranmer-intel's last comment. I think the important part is that we don't have any individual InstCombine transform checking function-level flags, and instead propagate the function-level attribute to instruction flags *somewhere* else. And it looks like SROA is a good place to do this as far as this issue is concerned. If we run into more cases where the phi is not created by SROA, we may want an explicit pass to do this.)

https://github.com/llvm/llvm-project/pull/83381