https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80313
Bug ID: 80313 Summary: -march=znver1 produce worse code than -march=haswell Product: gcc Version: 7.0.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: target Assignee: unassigned at gcc dot gnu.org Reporter: vincenzo.innocente at cern dot ch Target Milestone: --- Created attachment 41125 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=41125&action=edit sef contained scimark2 MC benchmark just got hold of a AMD Ryzen 7 1800X Eight-Core Processor and was surprised by the results running with -march=native the point is that the results can be reproduced on a haswell or broadwell as well! I used full scimark2, just the MC benchmark shows at least one problem this is on intel [innocent@vinavx3 fullMC]$ gcc -march=znver1 -O3 fullMC.c -g ; time ./a.out 1.245u 0.000s 0:01.24 100.0% 0+0k 0+0io 0pf+0w [innocent@vinavx3 fullMC]$ gcc -O3 fullMC.c -g ; time ./a.out 0.327u 0.000s 0:00.32 100.0% 0+0k 0+0io 0pf+0w [innocent@vinavx3 fullMC]$ gcc -march=broadwell -O3 fullMC.c -g ; time ./a.out 0.308u 0.000s 0:00.30 100.0% 0+0k 0+0io 0pf+0w this is on ryzen [innocent@vinzen0 fullMC]$ gcc -march=znver1 -O3 fullMC.c -g ; time ./a.out 1.354u 0.001s 0:01.35 100.0% 0+0k 0+0io 0pf+0w [innocent@vinzen0 fullMC]$ gcc -O3 fullMC.c -g ; time ./a.out 0.315u 0.000s 0:00.31 100.0% 0+0k 0+0io 0pf+0w [innocent@vinzen0 fullMC]$ gcc -march=broadwell -O3 fullMC.c -g ; time ./a.out 0.313u 0.001s 0:00.31 100.0% 0+0k 0+0io 0pf+0w