On Tue, Oct 22, 2013 at 1:58 PM, Bob Wilson <[email protected]> wrote:
> I really like GCC's -fprofile-generate and -fprofile-use, except I don't > think we should reuse those names for something that works differently. My > overall preference would be something like this (using those names as > placeholders): > > -fprofile-generate=<instrumentation-style> > -fprofile-use=<profile-style> > > e.g., "-fprofile-use=auto". That would at least unify the new options. > In fact, we may even be able to reuse those option names with > -fprofile-use being a synonym for -fprofile-use=gcc, which matches gcc's > option. I'm not at all familiar with how that option actually works in > gcc, so I can't say whether that would make sense. > I don't think we can re-use '-fprofile-use' in a way different from GCC here. GCC accepts it as "-fprofile-use=/path/..." and i could call my profile file "auto" or "gcc" or "clang" and expect it to work. I think it is best for instrumentation-based profiling to use '-fprofile-generate' and '-fprofile-use' just like GCC does, if with different file formats, etc. I don't see in flags in upstream GCC regarding sample-driven profiling, but "auto" I think is actively harmful in the name. There is nothing intrinsically automatic about it. It is "external" in the sense that it isn't from compiled-in instrumentation, but I don't see any reason for "auto" to indicate that to the user. I think for now, we should put this functionality behind a specific flag whose name is indicative of the user's expected behavior. The best idea I've seen is "-fsample-profile=/path/..." but I'd love to hear better suggestions.
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