https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81616
--- Comment #5 from Andrew Roberts <andrewm.roberts at sky dot com> --- I've been testing on a Ryzen system and also comparing with Haswell and Skylake. From my testing -mtune=znver1 does not perform well and never has, including as of last snapshot: gcc version 8.0.0 20171119 (experimental) (GCC) -mtune=generic seems a better option for all three systems as a default for -march=native This is only with one test case (attached), but I've seen the same across many other tests. See the attached testcase (matix.c) and performance logs Ryzen - znver1-tunebug.txt Haswell - znver1-tunebug2.txt Skylake - znver1-tunebug3.txt
