[llvm] [DAG] Lower frem of power-2 using div/trunc/mul+sub (PR #91148)

[David Green via llvm-commits]

https://github.com/davemgreen commented:

> This expansion should also work for negative power-of-two divisors like -4.0.
> 
> This expansion should also work for fractional power-of-two divisors like +/ 0.25, unless there is some concern about the division overflowing?

Thanks for the suggestions. Negative power-2 sounds good -- I'll add those in. Values smaller than 1 unfortunately make it round to infinity in cases where the frem would be valid.

https://github.com/llvm/llvm-project/pull/91148