[gcc-6] GOT_PREL optimization doesn't work in gcc-6
There is problem with non-optimal code generated by GCC to access global variables in position-independent code: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=43129. This bug is remains open for the upstream GCC, but it was fixed in Google's GCC fork: https://gcc.gnu.org/ml/gcc-patches/2011-04/msg02196.html. We're maintaining own GCC version, which we trying to keep as close as possible to the upstream one (i.e. FSF one), however, we include there several patches from Google's GCC fork. This specific patch was successfully applied on top of our gcc-5; however, it was not easy to apply it on top of gcc-6 due to significant changes in gcc-6 internals. That code just doesn't compiles anymore. Need to be fixed.