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[Bug lto/44334] rnflow.f90 ~27% slower with -fwhole-program -flto after revision 159852
- From: "dominiq at lps dot ens.fr" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Sun, 23 Jan 2011 11:43:42 +0000
- Subject: [Bug lto/44334] rnflow.f90 ~27% slower with -fwhole-program -flto after revision 159852
- Auto-submitted: auto-generated
- References: <bug-44334-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44334
--- Comment #30 from Dominique d'Humieres <dominiq at lps dot ens.fr> 2011-01-23 11:43:09 UTC ---
Concerning the timings in comment #27 they may reflect the fact the the inliner
is not aggressive enough for fortran codes and that it is worsen when using
-flto:
For rnflow.f90 I get
26.75s with -Ofast -funroll-loops -ftree-loop-linear -fomit-frame-pointer
26.66s with -Ofast -funroll-loops -ftree-loop-linear -fomit-frame-pointer
-finline-limit=600
27.60s with -Ofast -funroll-loops -ftree-loop-linear -fomit-frame-pointer
-fwhole-program -flto
27.14s with -Ofast -funroll-loops -ftree-loop-linear -fomit-frame-pointer
-finline-limit=600 -fwhole-program -flto
26.79s with -Ofast -funroll-loops -ftree-loop-linear -fomit-frame-pointer
-finline-limit=2000 -fwhole-program -flto
The result is more spectacular for fatigue.f90
8.50s with -Ofast -funroll-loops -ftree-loop-linear -fomit-frame-pointer
-finline-limit=600 -fwhole-program -flto
4.69s with -Ofast -funroll-loops -ftree-loop-linear -fomit-frame-pointer
-finline-limit=2000 -fwhole-program -flto
Note that revision 169136 seems to require higher values of -finline-limit:
before it, 600 was sufficient to see the speed-up (I have reported that in an
other pr), now it has been increased (I did not tried values lower than 2000
yet).