[Bug lto/45375] [meta-bug] Issues with building Mozilla with LTO

[hubicka at ucw dot cz]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45375

--- Comment #149 from Jan Hubicka <hubicka at ucw dot cz> 2012-12-02 15:05:52 UTC ---
> > Please try to reduce HOT_BB_COUNT_WS_PERMILLE to 990. I also see some
> > regressions
> > on some SPEC benchmarks (such as GCC) and this helps. If it doesn't it would be
> > nice to know what value is needed for comparable size.
> 
> Unfortunately it doesn't help much, because with "--param
> hot-bb-count-ws-permille=990" the size is only 0.25% smaller:
> (With --param) : 42098856
> (Without     ) : 42204584
> 
> I will try smaller values later.

Hmm, that sounds like quite bad news - the histogram code was supposed to help
in such cases.  I will try to fix the non-PGO case and lets try to compare how
PGO/non-PGO compare first.  If you could put somewhere the -fdump-ipa-inline
dump, I will try to check if there is something obviously wrong.

In worst case we can resort to combining both heuristics - i.e. keeping the
hot_bb_fraction in addition to histogram code. In fact I planned to do that
this
way but Teresa removed the old code and I did not see good reason why to keep
it.

Honza