[Bug tree-optimization/67815] Optimize const1 * copysign (const2, y) into copysign (const1 * const2, y) if const1 > 0 or -copysign (const1 * const2, y) if const1 < 0

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67815

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Comment on attachment 36487
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36487
r2

I think for copysign we don't want/need the first_pass_instance guard, and
likely also not flag_unsafe_math_optimizations, we want only be able to
reassociate, which can_reassociate_p should already guarantee, and then what
Joseph talked about for inexact.