------- Comment #16 from rguenth at gcc dot gnu dot org 2010-03-28 15:46
-------
(In reply to comment #15)
> I've been discussing this on IRC a while ago with Richard Guenther, but forgot
> to add a record.
>
> It seems that for 4.5, it is best to leave inlining heruistics as it is. THe
> code size regression come mainly from bzip that is excercising kind of typical
> "bad luck" scenario. Other known problem in 4.5 inlining is tramp3d where we
> now deliver worse than best known performance, but still not worse than one of
> 4.4.
>
> I spent some time playing with this and only way to get 4.5 inliner to solve
> these faults is to add new parameter that allows early inlining to inline
> forwarder functions that do increase code size estimates by small amount.
> This
> helps to solve both tramp3d and bzip problems but also cause code size issues
> in some benchmarks (mostly not regressions over 4.4) and is quite ugly.
>
> Since re-tunning heuristics needs significant amount of effort and it was done
> earlier in stage1 of 4.5 after merging changes from pretty-ipa, it seems
> better
> to leave as it is now. Also after LTO merge it seems, according to results
> posted by Vladimir Marakov, that the inliner is actually perfomring very well
> compared to other compilers.
>
> For 4.6 I do have number of plans. With FRE in early optimization queue we
> invalidate need for some of early inlining and also IPA stuff should be making
> us less dependent on inling overall.
>
> But I would propose this PR to be wontfix for 4.5.
Indeed.
There is also some miscounting of overall unit size, Micha has a patch for
that (but it completely chokes tramp3d results). There is also the
early inliner cleanups I have done at some point. Thus, I suppose we can
look at this early during 4.6 development again.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
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CC| |rguenth at gcc dot gnu dot
| |org, matz at gcc dot gnu dot
| |org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40436
