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Re: Inliner heuristics updated


On 5/26/05, Jan Hubicka <jh@suse.cz> wrote:
> > Yes.  In principle two stages of inlining could even make a better
> > code-size estimate if we're doing some simple optimization between
> > them.  So adding an extra switch for this early-inlining-of-small-functions
> > which would be automatically enabled for profile-based optimization
> > could be useful in general, especially at -O3 to get better size estimates.
> > Definitely I'd want to do some experiments if you can dig out the code
> > to do multiple inlining passes.
> 
> Hi,
> I am attaching the patch (not 100% polished, few testsuite failures).
> Quite amusingly the performance characteristics has changed since last
> time I tested it.  Now it seems to be performance neutral on GCC
> components (the slowdown has been actually caused by forgotten
> cgraph_verify_node call), it improves compile times by 12% on Gerald's
> testcase but it regress compile time wise on tramp3d by 30%.  On the
> other hand it makes tramp3d also 20% faster for me for some reason, so
> this tradeoff looks sort-of resonable.
> 
> With -ftree-based-profiling we now need 29s per iteration instead of 6s
> withhout, so the slowdown is still quite noticeable and additionally I
> noticed that compile times increase from 3m to 10m.  This is caused by
> fact that we use code size estimates computed before inlinig to drive
> the inliner, I will fix that.

You mean not re-computing the size estimate, but only using the update
from the simple formula, or not updating at all?  Anyway, this is good news!

Thanks,
Richard.


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