[Bug lto/44334] rnflow.f90 ~27% slower with -fwhole-program -flto after revision 159852

["dominiq at lps dot ens.fr" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44334

--- Comment #47 from Dominique d'Humieres <dominiq at lps dot ens.fr> 2011-01-25 19:06:04 UTC ---
> I sorted out increasing large function growth ratio as most safe way  
> to deal with (easier half of) this problem. Unlike the parameters for  
> inline limits it won't cause code size issues. It just allow somewhat  
> bigger functions and thus stress more the backend on its linearity.

Well, the choice is not '-finline-limit' versus '--param
large-function-growth': some polyhedron tests are sensitive to some value of
'-finline-limit' (ac, channel, fatigue, ...) and for most of them '--param
large-function-growth' does not change anything. 

fatigue is quite peculiar in that there is a big speed-up with -fwhole-program
for -finline-limit>=322and an additional small speed-up for --param
large-function-growth>=132. In addition the later prevent a bad choice with
-flto (this should probably be discussed in pr 45810 and this pr closed as
fixed).

Note that I am not interested by fine tuning, but to find some acceptable
values of the default parameters that give good results for all (most;-)
fortran codes).