[Bug tree-optimization/124545] VN nary lookup trick for converted plus/minus lacks inverse trick

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=124545

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Created attachment 63954
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=63954&action=edit
patch

tested on x86-64-linux, queued for stage1