clean up round_from_int and to_int_unchecked after #232

[programmerjake]

you could remove round_from_int afaict because it's functionality is completely supplanted by cast

also to_int_unchecked should be generic over return type

Originally posted by @programmerjake in #232 (comment)

[programmerjake]

Yes, I was thinking "hm, do I want to touch fn round_from_int?" but then I realized I didn't have a good vibe anymore for how strong the consensus was around fn round_from_int and fn to_int_unchecked, so I was going to bring that up at our next sync.

Originally posted by @workingjubilee in #232 (comment)

[andy-thomason]

I had to add a round_to_uint for bit twiddling of exponents in my branch.

If cast covers this, I'll change it.

[workingjubilee]

Probably! Simd::cast is effectively a lanewise version of Rust's as, which means that for floats, it does a saturating conversion to the integer. Sight unseen, you may want to, for peeling out data from a float like the exponent, use Simd<f32>::{from,to}_bits instead.

[andy-thomason]

That is great as I'm translating scalar expressions to SIMD. Having something which is directly like as would be ideal.

The code is quite crude at the moment, but does produce a working translation.