https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64099
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> --- (In reply to Dominique d'Humieres from comment #2) > > I don't see this on any of our testers. What CPU do you have and what > > default > > -march gets used for you? (thus please show -v output) > > My CPU is a 2.8 GHz Intel Core i7. All the versions reported in comment 0 > have been configured with > > ../p_work/configure --prefix=/opt/gcc/gcc4.10p-#rev.p#patch > --enable-languages=c,c++,lto,fortran,ada,objc,obj-c++ --with-gmp=/opt/mp > --with-system-zlib --enable-checking=release --with-isl=/opt/mp --enable-lto > --enable-plugin --with-arch=core2 --with-cpu=core2 Ok, so it is -march=core2 > but r216631 for which --enable-checking=release has been omitted. #rev. is > the revision and #patch is the number of patches required to bootstrap. > > > Btw, -flto should be redundant for a single-file benchmark - -fwhole-program > > is enough. > > I know, however I have seen in the past some regressions when -flto is > added. Since I can afford to double the compile time, I keep it in my > reference options. > > > Does -ftree-loop-linear make a difference for you? > > AFAICT it does not on fatigue.f90, but I see some (minor) improvements for > other tests in the suite. > > > Our testers use -ffast-math -funroll-loops -O3. > > Using '-O3 -ffast-math' instead of '-Ofast' almost double the runtime: Ugh - -Ofast is an alias for -O3 -ffast-math. Ah, no - it also enables --param allow-store-data-races=1 ... > [Book15] lin/test% gfortran -O3 -ffast-math -fwhole-program fatigue.f90 > [Book15] lin/test% time a.out > /dev/null > 2.648u 0.002s 0:02.65 99.6% 0+0k 0+3io 38pf+0w > [Book15] lin/test% gfortran -Ofast -fwhole-program fatigue.f90 > [Book15] lin/test% time a.out > /dev/null > 1.385u 0.002s 0:01.38 100.0% 0+0k 0+1io 0pf+0w > [Book15] lin/test% gfc -O3 -ffast-math -fwhole-program fatigue.f90 > [Book15] lin/test% time a.out > /dev/null > 2.952u 0.002s 0:02.96 99.6% 0+0k 0+0io 40pf+0w > [Book15] lin/test% gfc -Ofast -fwhole-program fatigue.f90 > [Book15] lin/test% time a.out > /dev/null > 1.643u 0.001s 0:01.64 100.0% 0+0k 0+1io 0pf+0w > > (gfortran is 4.9.2 and gfc is 5.0 r218134). > > The runtime increase with '-O3 -ffast-math' is ~0.4s between r217816 and > r217833 > > [Book15] lin/test% /opt/gcc/gcc4.10p-217816p2/bin/gfortran -O3 -ffast-math > -fwhole-program fatigue.f90 > [Book15] lin/test% time a.out > /dev/null > 2.654u 0.002s 0:02.66 99.6% 0+0k 0+1io 41pf+0w > [Book15] lin/test% /opt/gcc/gcc4.10p-217833p1/bin/gfortran -O3 -ffast-math > -fwhole-program fatigue.f90 > [Book15] lin/test% time a.out > /dev/null > 2.962u 0.001s 0:02.97 99.6% 0+0k 0+1io 39pf+0w > > > Can you bisect the regressions to a single commit? > > I can do it for the range r217816-r217833 (the candidates are r217824 and > r217827, may be r217828 also). As indicated by the p? in my coding scheme, I > cannot bootstrap in the range r216631-r216747 without at least two patches, > so bisecting this range will take much longer.
