https://gcc.gnu.org/bugzilla/show_bug.cgi?id=16351
--- Comment #44 from Jeffrey A. Law <law at redhat dot com> --- Duh, I should have remembered that we had returns_nonnull because I wrote a dataflow pass to find any NULLs that flow to such statements :-) The pieces that are missing are tagging functions with that attribute when we can prove they never return NULL. We'll be relying a lot of IPA to present functions in the right order, but it'd be a good improvement.