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Re: -fprofile-generate and -fprofile-use
- From: Zdenek Dvorak <rakdver at atrey dot karlin dot mff dot cuni dot cz>
- To: Jan Hubicka <jh at suse dot cz>
- Cc: Peter Steinmetz <steinmtz at us dot ibm dot com>, gcc at gcc dot gnu dot org,girish_vaithees at yahoo dot com, hubicka at ucw dot cz, janis187 at us dot ibm dot com,Steven Bosscher <stevenb at suse dot de>
- Date: Fri, 2 Sep 2005 11:01:32 +0200
- Subject: Re: -fprofile-generate and -fprofile-use
- References: <20050831090340.GA23405@atrey.karlin.mff.cuni.cz> <OF6BA01E8F.9201293A-ON8625706E.0052A364-8625706E.005321D4@us.ibm.com> <20050901190450.GK24529@kam.mff.cuni.cz>
Hello,
> > >you may try adding -fmove-loop-invariants flag, which enables new
> > >invariant motion pass.
> >
> > That cleaned up both my simplified test case, and the code it
> > originated from. It also cleaned up a few other cases where I
> > was noticing worse performance with FDO enabled. Thanks!!
> >
> > Perhaps this option should be enabled by default when doing FDO
> > to replace the loop invariant motions done by the recently
> > disabled loop optimize pass.
>
> This sounds like sane idea. Zdenek, is -fmove-loop-invariants dangerous
> in some way or just disabled because old loop does the same?
-fmove-loop-invariants is enabled by default on killloop-branch, and
passes bootstrap & regtesting on i686 and x86_64; the branch does not
bootstrap for me on ia64 and ppc (but neither does mainline). I am
not aware of any correctness/ICE problems with -fmove-loop-invariants,
but given that it is disabled by default, this does not say much.
Zdenek