https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104014
--- Comment #7 from Jakub Jelinek <jakub at gcc dot gnu.org> --- (In reply to David Binderman from comment #6) > (In reply to Jakub Jelinek from comment #5) > > That makes no sense. > > Surprising. > > bootstrap-O3 tests more of the compiler than the ordinary bootstrap-O2 does. Not really. It tests different code paths in the compiler. > > And, -march=native is a moving target, different for each developer. > > Indeed it is. We all have different boxes. But adding -march=native > tests more of the compiler. Not really. > Agreed. But if a native bootstrap works for some machine, > we can be pretty sure it will work for all predecessor machines > of the same architecture. Certainly not. > > > --with-arch=native --with-cpu=native bootstraps aren't a good idea for > > gcc-testresults posts as well because it is hard to determine what exactly > > that native expands to. > > It wouldn't be impossible to require folks to specify what their native > target was. >From my experience, that is a total nightmare. People usually say in such case if they specify anything I'm using a Skylake or something similar, in better cases Intel i9-7680X or whatever they have. But mapping that to the actual -march= -misa1 -misa2 etc. options that the -march=native expands to is hard, one needs to look up what model/stepping such CPU has somewhere and exact set of ISAs it supports and then try to repeat what driver-*.c does manually. Sure, one can use gcc -v and paste the cc1 etc. invocation line, but people just don't do that, so it is another step where you need to ask them. So it is much better if people actually test --with-arch=skylake-avx512 or whatever exact -march= they have, that isn't a moving target.
