https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86448
--- Comment #3 from Michael Meissner <meissner at gcc dot gnu.org> --- The options I use for spec are: -O3 -fpeel-loops -funroll-loops -ftree-vectorize -fvect-cost-model -msave-toc-indirect -mno-pointers-to-nested-functions -fno-aggressive-loop-optimizations -ffast-math -mveclibabi=mass -mrecip=rsqrt -mcpu=power<x> For C files I use: -fgnu89-inline For C++ files I use: -std=gnu++98 For Fortran files I use: -fstack-arrays I use -fno-strict-aliasing on milc (and perlbench) due to it playing pointer games that earlier compilers would generate the wrong code for. If memory serves, the -fno-strict-aliasing may not show the bug on power{7,8,9} systems. I know in the perlbench case, the code in spec violates the ISO C standard. I don't recall what the milc code is. I use -fno-aggressive-loop-optimizations because some of the benchmarks as written go beyond the end of arrays, and GCC over-optimizes these. I use version 8.1.3 of the MASS library. However, milc is not one of the benchmarks that heavily use the math library, so you can omit using MASS and -mveclibabi=mass.