[Bug target/84280] [6/7/8 Regression] Performance regression in g++-7 with Eigen for non-AVX2 CPUs

[patrikhuber at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84280

--- Comment #14 from Patrik Huber <patrikhuber at gmail dot com> ---
It even seems a few percent slower after the FDO stuff. But the `
-fprofile-use` is a bit weird. If there is no .gcda file, it doesn't complain.
If you give it a file that doesn't exist (e.g. -fprofile-use=foo), then it
doesn't complain either. So how can I check whether it really ran the FDO?