[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

[mpolacek at gcc dot gnu.org]

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

--- Comment #4 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
Created attachment 36487
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=36487&action=edit
r2

Untested preliminary patch.  I'm not sure about the floating-point matter in
there.