`simd_fpow` and `simd_fpowi` intrinsics are not exposed in `intrinsics::simd`

[folkertdev]

As a result, to test/use these intrinsics they must be redeclared outside of core, which is at best inelegant and at worst could lead to subtle bugs.

I think there are two options:

• this is an oversight, and we should define and expose these intrinsics
• there is an undocumented reason that these intrinsics are not exposed in the standard way
• edit: secret third thing: these intrinsics are not useful and should be removed

cc @calebzulawski it looks like you touched this last 5 years ago 07db2bf. Long time, but maybe you remember something?

@rustbot label +A-simd +F-core_intrinsics

[RalfJung]

As far as I can see, neither stdarch nor portable-simd use these intrinsics. So... should we just remove them? Or is there a reason for them to exist?

Cc @workingjubilee @calebzulawski @Amanieu

[folkertdev]

None of the targets/instruction sets I could think of seem to do anything smart

https://godbolt.org/z/KP1K66nhP

they just seem to spill to the stack and use the standard scalar pow functions. A strong argument for removing these intrinsics.

[workingjubilee]

then I'm pro-yeet, assuming there isn't something special I don't remember

[calebzulawski]

Odd that they don't do much at all. Seems ok to remove them to me, we can re-add (working) intrinsics if we try to expose a function that needs it

[RalfJung]

@folkertdev are you planning to make a PR that removes them? :)

[folkertdev]

Yes

[folkertdev]

I opened #137595