https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80859
--- Comment #13 from Thorsten Kurth <thorstenkurth at me dot com> --- Hello Jakub, the compiler options are just -fopenmp. I am sure it does not have to do anything with vectorization as I compare the code runtime with and without the target directives and thus vectorization should be the same between them. The remaining OpenMP sections are the same. In our work we have not seen 10x because of insufficient vectorization, it is usually because of cache locality but that is the same for OMP 4.5 and OMP 3 because the loops are not touched. I do not specify an ISA choice, but I will try specifying KNL now and will tell you what the compiler is going to do. Best Thorsten