https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83022
--- Comment #2 from Nathan Sidwell <nathan at gcc dot gnu.org> --- Yes, this is a measurable degradation in going from gcc 4.9 -> 5.0 with myrocks DB. Apparently 25% more queries/sec with gcc 4.9 (I think it's from a benchmark). Profiling (by others) has fingered this optimization. I am in the process of implementing a check to see if the only condition between the malloc and memset is 'ptr != 0'. I noticed the crazy default probabilities during investigating this. I think that's really a second-order problem.
