[Bug middle-end/57806] Wasted work in propagate_nothrow()

[pchang9 at cs dot wisc.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57806

--- Comment #1 from Po-Chun Chang <pchang9 at cs dot wisc.edu> ---
Created attachment 30439
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=30439&action=edit
Suggested patch