------- Comment #5 from rguenth at gcc dot gnu dot org 2010-04-22 14:00 -------
Now onto
subroutine test1(esss,Ix,Iyz)
real(kind=kind(1.0d0)), dimension(:), intent(out) :: esss
real(kind=kind(1.0d0)), dimension(:,:) :: Ix,Iyz
esss = sum(Ix * Iyz, 1)
end subroutine
noting that we can exchange the sum and the indexing of the assignment
making the sum() of rank one (and thus eligible for inline expansion).
Thus, expand it as
do i=1,size(esss)
esss(i) = sum(Ix(i,:) * Iyz(i,:))
end do
An even simpler testcase where we want to do this exchange is
subroutine test0(esss,Ix,Iyz)
real(kind=kind(1.0d0)), dimension(:), intent(out) :: esss
real(kind=kind(1.0d0)), dimension(:,:), intent(in) :: Ix
esss = sum(Ix, 1)
end subroutine
Thus, whenever the reduction is one-dimensional (though in this simpler
testcase we do not avoid the temporary for the sum intrinsic argument
which was the point of the excercise). So, slightly more complicated
to show that this is still beneficial:
subroutine test0(esss,Ix,Iyz)
real(kind=kind(1.0d0)), dimension(:), intent(out) :: esss
real(kind=kind(1.0d0)), dimension(:,:), intent(in) :: Ix
esss = esss + sum(Ix, 1)
end subroutine
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=43829
