[llvm] [InstCombine] optimize powi(X,Y)/X with Ofast (PR #67236)

[Nikita Popov via llvm-commits]

nikic wrote:

Looks OK, but FP is outside my area of expertise, in particular I wouldn't be able to say which FMF flags a transform should or should not require.

https://github.com/llvm/llvm-project/pull/67236