[Bug tree-optimization/123258] Multiplication by -1 not hoisted

[mjr19 at cam dot ac.uk]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123258

--- Comment #2 from mjr19 at cam dot ac.uk ---
(In reply to mjr19 from comment #0)
>
> But if one constant is -1, whether
> 
>  a(i+1)=a(i+1)*(-1.0)*-b(2)

I meant

  a(i+1)=a(i+1)*(-1.0)*b(2)

of course.