julia

06ad3f49 - Make various core math functions easier for the compiler to reason about (#43907)

Make various core math functions easier for the compiler to reason about (#43907) * ldexp: Break inference loop We have an inference loop fma_emulated -> ldexp -> ^(::Float64, ::Int) -> fma -> fma_emulated. The arguments to `^` are constant, so constprop will figure it out, but it does require a bunch of extra processing. There is a simpler way to write this using elementary bit operations. Since resolving the inference loop requires constprop, this was breaking #43852. That is fixable, but I think we should also make this change to avoid having an unnecessary inference loop in our basic math functions, which will make future analyses easier. * Make fma_emulated easier for the compiler to reason about The fact that the `exponent` call in `fma_emulated` requires reasoning about the ranges of the floating point values in question, which the compiler is not capable of doing (and is unlikely to ever do automatically). Thus, in order for the compiler to know that `fma_emulated` (and by extension `fma`) is :nothrow in a post-#43852 world, create a separate version of the `exponent` function that assumes its precondition. We could use `@assume_effects` instead, but this version is currently slightly easier on the compiler. * pow: Make integer vs float branch obvious to constprop The integer branch is nothrow, so if the caller does something like `^(x::Float64, 2.0)`, we'd like to discover that.