[Bug tree-optimization/113339] `-a/-b` is not simplified to `a/b` if done in seperate statements

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113339

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
So I looked into the wrong part of fold, but anyways PR 23669 added the folding
to fold instead (and I just noticed I implemented it originally).