http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49813
--- Comment #50 from Kaveh Ghazi <ghazi at gcc dot gnu.org> 2011-07-27 23:13:18 UTC --- (In reply to comment #46) > Another note, about std::nextafter, std::nexttoward, & co: I see mpfr provides > an mpfr_nexttoward, which likely could be exploited in builtins.c pretty > easily. > Kaveh, do you have any plan about those? It's been several years since I did the mpfr work so my memory is a little foggy, but I think I intentionally skipped the next* functions. IIRC, these functions are very sensitive to the target floating point format. It wasn't clear to me that the "next" FP value in mpfr actually corresponded to the "next" value in the target FP format or how to verify if it was so. (I'm thinking mainly of the non-ieee formats here.) If these odd formats aren't used in GCC anymore then it might be okay to implement the builtins using mpfr. Alternatively, you can implement the builtins only for the formats where mpfr's format is identical to the target fp format. But then the optimization won't work everywhere so your library testcase will fail on some cpus. I'm not sure it's worth the trouble (and to answer your question I don't have any plans to work on it.)