[Bug c++/33604] significantly slower results with 4.3 compared to 4.2

["rguenth at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #2 from rguenth at gcc dot gnu dot org  2007-10-01 09:46 -------
With a more recent 4.3 version I get

     4.2   4.3
-O2  6.1s  5.1s
-O3  4.1s  5.1s

both -O3 variants have one function not inlined in the main loop.  For 4.2
it is

EiEval<EiMatrixProduct<EiMatrix<double, 3, 3>, EiMatrix<double, 3, 3> > >
operator*<double, EiMatrix<double, 3, 3>, EiMatrix<double, 3, 3>
>(EiObject<double, EiMatrix<double, 3, 3> > const&, EiObject<double,
EiMatrix<double, 3, 3> > const&)

for 4.3 it is

EiMatrix<double, 3, 3>& EiObject<double, EiMatrix<double, 3, 3>
>::operator=<EiSum<EiMatrix<double, 3, 3>,
EiScalarProduct<EiSum<EiMatrix<double, 3, 3>, EiMatrix<double, 3, 3> > > >
>(EiObject<double, EiSum<EiMatrix<double, 3, 3>,
EiScalarProduct<EiSum<EiMatrix<double, 3, 3>, EiMatrix<double, 3, 3> > > > >
const&)

but even complete inlining does not improve numbers much.  There's also
nothing obvious in the asm - we simply have too little registers and load/store
from/to memory very often.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33604