[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 #17 from Dominique d'Humieres <dominiq at lps dot ens.fr> 2010-12-21 10:46:06 UTC ---
For the record I have also tested the patch in comment #14 on
powerpc-apple-darwin9 at revision 168070. Without the patch I get

[karma] lin/test% gfc -Ofast -funroll-loops -ftree-loop-linear
-fomit-frame-pointer -finline-limit=600 --param hot-bb-frequency-fraction=2000
-fwhole-program -flto rnflow.f90
[karma] lin/test% time a.out > /dev/null
68.236u 6.947s 1:17.77 96.6%    0+0k 0+0io 0pf+0w
[karma] lin/test% gfc -Ofast -funroll-loops -ftree-loop-linear
-fomit-frame-pointer -finline-limit=600 -fwhole-program -flto rnflow.f90
[karma] lin/test% time a.out > /dev/null
65.229u 6.838s 1:14.61 96.5%    0+0k 0+0io 0pf+0w

Note a slight slow down with -param hot-bb-frequency-fraction=2000. With the
patch I get

[karma] lin/test% gfc -Ofast -funroll-loops -ftree-loop-linear
-fomit-frame-pointer -finline-limit=600 --param hot-bb-frequency-fraction=2000
-fwhole-program -flto rnflow.f90
[karma] lin/test% time a.out > /dev/null
69.690u 6.917s 1:19.44 96.4%    0+0k 0+0io 1pf+0w
[karma] lin/test% gfc -Ofast -funroll-loops -ftree-loop-linear
-fomit-frame-pointer -finline-limit=600 -fwhole-program -flto rnflow.f90
[karma] lin/test% time a.out > /dev/null
69.791u 7.225s 1:20.08 96.1%    0+0k 0+0io 0pf+0w

i.e.,  -param hot-bb-frequency-fraction=2000 does not change the timings, but
the resulting code is slower.