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

["howarth at nitro dot med.uc.edu" <gcc-bugzilla at gcc dot gnu dot org>]

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

--- Comment #48 from Jack Howarth <howarth at nitro dot med.uc.edu> 2011-01-25 21:29:53 UTC ---
(In reply to comment #47)

> 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).

In my tests, --param large-function-growth=200 was sufficient to yield 60% of
the performance increase in the fatigue benchmark obtained by modifying both
-finline-limit and --param large-function-growth.  Unlike increasing
-finline-limit, none of the other pb05 benchmarks showed even minor regressions
in speed.