465.tonto in one of its hot loops does essentially what the following reduced
testcase does:
subroutine make_esss(esss,Ix,Iyz,e_x,ii_ivec)
real(kind=kind(1.0d0)), dimension(:), intent(inout) :: esss
real(kind=kind(1.0d0)), dimension(:,:), pointer :: Ix,Iyz
integer(kind=kind(1)), dimension(:), pointer :: e_x,ii_ivec
esss(:) = esss(:) + sum(Ix(:,e_x) * Iyz(:,ii_ivec), 1)
end subroutine
this is scalarized by the frontend to
atmp4 = e_x
atmp6 = ii_ivec
atmp8 = Ix(:,atmp4) * Iyz(:,atmp6)
atmp11 = sum (atmp8, 1)
ess = ess + atmp11
where the sum is not inline-expanded.
1) the temporaries for e_x and ii_ivec are not necessary
2) the sum can easily be inline-expanded as the shape of atmp8 is well-defined
3) we can avoid atmp8 by expanding sum(Ix(:,e_x), Iyz(:ii_ivec), 1) together
like
atmp11(z) = 0
do z=1,size(Ix,1)
atmp11(z) = atmp11(z) + Ix(z,e_x(e)) * Iyz(z,ii_ivec(e))
end do
or even avoid atmp11 alltogether and expand to
do e=1,size(esss,1)
tem = 0
do z=1,size(Ix,1)
tem = tem + Ix(z,e_x(e)) * Iyz(z,ii_ivec(e))
end do
esss(e) = esss(e) + tem
end do
given that esss does not have the target attribute and thus cannot
be aliased by e_x or ii_ivec.
--
Summary: Scalarization of reductions
Product: gcc
Version: 4.6.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: enhancement
Priority: P3
Component: fortran
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: rguenth at gcc dot gnu dot org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43829
