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Re: Loop unrolling-related SPEC regressions?

Paolo Carlini <> writes:

> Jan Hubicka wrote:
>> >
>> > > browsing the latest results from Andreas, it looks like a few of them (e.g.,
>> > > 164.gzip, 186.crafty, 200.sixtrack) are showing a definite regression in the
>> > > PEAK case, characterized by -funroll-all-loops.
>> >
>> > It's not clear to me that -funroll-all-loops is the correct setting for
>> > PEAK, as bloating out the code may make the cache perform worse.
>> We do use them in the testing runs for exactly these purposes.
>> It tends to show the "bugs" that causes unnecesary code growth in some
>> areas unnoticed by other benchmarks.
>> THe base/peak flags are not supposed to bring best performance,
>> but be good for testing majority of gcc features.
> That's really enlightening Honza! Thanks for the clarification.
> We should also remember this when someone compares the SPEC numbers made available
> by other compiler producers with those of GCC: my guess is that this kind of
> rationale for choosing the PEAK flags it's unfortunately not so widespread...

Didn't I mention it that way?  Feel free to send a patch for my SPEC
page to clarify what we're doing...

 Andreas Jaeger
  SuSE Labs

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