https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86448
--- Comment #4 from kelvin at gcc dot gnu.org --- There are aspects of Michael's recent comment that I may not fully understand. I checked the source for milc, and it is C, so I added -fgnu89-inline to the list of OPTIMIZE options. Then I reran my tests with gcc8 (svn version 262483) on a DD2.2 power9 machine. OPTIMIZE = -O3 -fpeel-loops -funroll-loops -ftree-vectorize -fvect-cost-\ model -fno-strict-aliasing -msave-toc-indirect -mno-pointers-to-nested-function\ s -fno-aggressive-loop-optimizations -ffast-math -mveclibabi=mass -mrecip=rsqrt\ -fgnu89-inline -mcpu=power9 (vs. -mcpu=power8) LDOPT = -m64 -Wl,-q -Wl,-rpath=%{BASE_DIR}/lib64 I'm still not seeing the performance degradation Michael saw. Here are my most recent results: gcc8 gcc9 28.79 28.14 29.01 28.84 28.51 28.5 28.55 28.39 29.02 29.07 29.1 28.51 delta % delta average 28.83 28.575 0.255 0.88% Does anyone see anything I may be doing wrong?