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

[rguenther at suse dot de]

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

--- Comment #4 from rguenther at suse dot de <rguenther at suse dot de> ---
"dominiq at lps dot ens.fr" <gcc-bugzilla@gcc.gnu.org> wrote:
>http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59487
>
>--- Comment #3 from Dominique d'Humieres <dominiq at lps dot ens.fr>
>---
>> r202826 was fixed later by the fix for PR58656 (rnflow regression), 
>> so your bisection converged on a bogus revision.
>
>OK! I was too focused on the -fwhole-program option. The slowdown after
>r202826
>was with/without this option. r203377 fixed the regression without the
>option,
>but not with it:

Still the regression must appear with a different revision.  The one you cited
has nothing to do with -fwhole-program.

Richard.

>[Book15] lin/test% /opt/gcc/gcc4.9p-202825/bin/gfortran -Ofast
>-fwhole-program
>rnflow.f90
>[Book15] lin/test% time a.out > /dev/null
>12.843u 0.017s 0:12.86 99.9%    0+0k 0+0io 0pf+0w
>[Book15] lin/test% /opt/gcc/gcc4.9p-202825/bin/gfortran -Ofast
>rnflow.f90
>[Book15] lin/test% time a.out > /dev/null
>12.889u 0.022s 0:12.92 99.8%    0+0k 0+0io 41pf+0w
>[Book15] lin/test% /opt/gcc/gcc4.9p-202828/bin/gfortran -Ofast
>rnflow.f90
>[Book15] lin/test% time a.out > /dev/null
>17.891u 0.019s 0:17.91 99.9%    0+0k 0+0io 0pf+0w
>[Book15] lin/test% /opt/gcc/gcc4.9p-202828/bin/gfortran -Ofast
>-fwhole-program
>rnflow.f90
>[Book15] lin/test% time a.out > /dev/null
>17.985u 0.021s 0:18.01 99.9%    0+0k 4+0io 41pf+0w
>[Book15] lin/test% /opt/gcc/gcc4.9p-203250/bin/gfortran -Ofast
>rnflow.f90
>[Book15] lin/test% time a.out > /dev/null
>17.974u 0.020s 0:17.99 100.0%    0+0k 0+0io 0pf+0w
>[Book15] lin/test% /opt/gcc/gcc4.9p-203250/bin/gfortran -Ofast
>-fwhole-program
>rnflow.f90
>[Book15] lin/test% time a.out > /dev/null
>18.182u 0.021s 0:18.21 99.9%    0+0k 0+1io 38pf+0w
>[Book15] lin/test% /opt/gcc/gcc4.9p-203492/bin/gfortran -Ofast
>rnflow.f90
>[Book15] lin/test% time a.out > /dev/null
>12.856u 0.018s 0:12.87 99.9%    0+0k 0+0io 0pf+0w
>[Book15] lin/test% /opt/gcc/gcc4.9p-203492/bin/gfortran -Ofast
>-fwhole-program
>rnflow.f90
>[Book15] lin/test% time a.out > /dev/null
>18.253u 0.021s 0:18.28 99.9%    0+0k 0+0io 39pf+0w
>
>AFAICT the usual incantations ('large-function-growth',
>'max-inline-insns-auto', or 'builtin-expect-probability') have no
>visible
>effect on this slowdown with -fwhole-program.