[llvm] [InstCombine] optimize exp(exp(x)) / exp(x) with fast-math (PR #66177)

[Nikita Popov via llvm-commits]

https://github.com/nikic requested changes to this pull request.

This pattern is too specific. I assume the motivation here is this special case where `exp(x)` has multiple uses, which means that the `x / exp(y)` to `x * exp(-y)` fold does not trigger. However, you should still be able to handle something more general, such as `exp(x) / exp(y)` to `exp(x - y)` where `exp(x)` has one use. This does not reduce the number of exp calls, but does reduce the number of division.

https://github.com/llvm/llvm-project/pull/66177