http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54966
--- Comment #5 from rguenther at suse dot de <rguenther at suse dot de> 2012-10-23 14:02:05 UTC --- On Tue, 23 Oct 2012, hubicka at ucw dot cz wrote: > > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54966 > > --- Comment #4 from Jan Hubicka <hubicka at ucw dot cz> 2012-10-23 13:59:38 > UTC --- > > I'm not sure how we count the initial unit size, given that when not using > > LTO not merged comdats are probably counted here, so overall they add up > > while the initial LTO unit size may be considerably smaller than the sum > > of the non-LTO unit sizes. > > I do not realy see problem here. We simply count size of the unit by summing > all the functions in the callgraph prior inlining (after merging). So in the > case of LTO we count COMDATs once and if they are unused by non-LTO we promote > them to static and get better inlining due removing offline copies (that we > are > acccounting as inline decisions are made). In the case of non-LTO we count > COMDAT in every unit that has the COMDAT used + we have heuristic predicting > that most likely the COMDAT will be eliminated in the other units, too, if it > is eliminated in the current unit. So we inline them almost as aggressively > as > statics, but not quite. > > What kind of problem are you looking into? I was just guessing why our overall unit-growth heuristics would lead to different overall inlining with LTO vs. single TUs. Richard.
