https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56888
--- Comment #42 from Eric Gallager <egallager at gcc dot gnu.org> --- (In reply to Rich Felker from comment #41) > > Josef Wolf mentioned that he ran into this on the gcc-help mailing list > > here: https://gcc.gnu.org/ml/gcc-help/2019-10/msg00079.html > > I don't think that's an instance of this issue. Well ok, maybe not THAT message specifically; see the rest of the thread though. > It's normal/expected that __builtin_foo compiles to a call to foo in the > absence of factors that lead to it being optimized to something simpler. > The idiom of using __builtin_foo to get the compiler to emit an optimized > implementation of foo for you, to serve as the public definition of foo, is > simply not valid. That's kinda a shame because it would be nice to be able to > do it for lots of math library functions, but of course in order for this to > be > able to work gcc would have to promise it can generate code for the operation > for all targets, which is unlikely to be reasonable.
