[Bug tree-optimization/59487] New: [4.9 Regression] When compiled with -fwhole-program rnflow.f90 runs up to 40% slower after r202826

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

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59487

            Bug ID: 59487
           Summary: [4.9 Regression] When compiled with -fwhole-program
                    rnflow.f90 runs up to 40% slower after r202826
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dominiq at lps dot ens.fr
                CC: burnus at gcc dot gnu.org, Ganesh.Gopalasubramanian at amd dot com,
                    rguenth at gcc dot gnu.org

When compiled with -fwhole-program rnflow.f90 runs up to 40% slower after
r202826 (Core i7 at 2.8Ghz):

[Book15] lin/test% /opt/gcc/gcc4.9p-202828/bin/gfortran -Ofast -fwhole-program
rnflow.f90
[Book15] lin/test% time a.out > /dev/null
18.244u 0.020s 0:18.26 100.0%    0+0k 3+1io 0pf+0w
[Book15] lin/test% /opt/gcc/gcc4.9p-202825/bin/gfortran -Ofast -fwhole-program
rnflow.f90
[Book15] lin/test% time a.out > /dev/null
13.022u 0.024s 0:13.04 100.0%    0+0k 4+1io 0pf+0w
[Book15] lin/test% gfcc -Ofast -fwhole-program rnflow.f90
[Book15] lin/test% time a.out > /dev/null
18.533u 0.036s 0:18.58 99.8%    0+0k 0+0io 45pf+0w
[Book15] lin/test% gfcc -Ofast rnflow.f90
[Book15] lin/test% time a.out > /dev/null
13.059u 0.020s 0:13.08 99.9%    0+0k 0+0io 0pf+0w
[Book15] lin/test% gfc -Ofast -fwhole-program rnflow.f90
[Book15] lin/test% time a.out > /dev/null
12.940u 0.028s 0:12.97 99.9%    0+0k 0+0io 14pf+0w

gfcc is r205891 and gfc r205924 with the patch for pr58721 at
http://gcc.gnu.org/ml/fortran/2013-12/msg00069.html which fixes also this
slowdown (the slowdown is ~20% on a Core2Duo at 2.5Ghz). This has been noticed
in the last comment of pr58464.