[Bug fortran/55806] New: Missed optimization with ANY or ALL

["tkoenig at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55806

             Bug #: 55806
           Summary: Missed optimization with ANY or ALL
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: fortran
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: tkoenig@gcc.gnu.org


Mike Metcalf complains (correctly) in
<44daf54c-3de5-4b1c-a1f7-cb7bf0d496b0@googlegroups.com>
that using ANY as an idiom instead of .or. for a small number of conditions.



Look at this:

module mymod
contains
  subroutine bar(a,b,c)
    integer, dimension(3,3), intent(in) :: a,b
    integer, intent(out) :: c
    real, parameter :: acc = 1e-4
    integer :: i

    c = 0
    do i=1,3
       if (any([abs(a(i,1) - b(i,1)) > acc,  &
            abs(a(i,2) - b(i,2)) > acc, &
            abs(a(i,3) - b(i,3)) > acc])) cycle
       c = c + 1
    end do
  end subroutine bar
end module mymod

This generates a logical array, assigns the values to them,
and then loops over the array to generate the values:


              atmp.1.dtype = 273;
              atmp.1.dim[0].stride = 1;
              atmp.1.dim[0].lbound = 0;
              atmp.1.dim[0].ubound = 2;
              atmp.1.data = (void * restrict) &A.2;
              atmp.1.offset = 0;
              (*(logical(kind=4)[3] * restrict) atmp.1.data)[0] =
(real(kind=4)) ABS_EXPR <(*a)[(integer(kind=8)) i + -1] -
(*b)[(integer(kind=8)) i + -1]> > 9.99999974737875163555145263671875e-5;
              (*(logical(kind=4)[3] * restrict) atmp.1.data)[1] =
(real(kind=4)) ABS_EXPR <(*a)[(integer(kind=8)) i + 2] - (*b)[(integer(kind=8))
i + 2]> > 9.99999974737875163555145263671875e-5;
              (*(logical(kind=4)[3] * restrict) atmp.1.data)[2] =
(real(kind=4)) ABS_EXPR <(*a)[(integer(kind=8)) i + 5] - (*b)[(integer(kind=8))
i + 5]> > 9.99999974737875163555145263671875e-5;
              {
                integer(kind=8) S.4;

                S.4 = 0;
                while (1)
                  {
                    if (S.4 > 2) goto L.5;
                    if (NON_LVALUE_EXPR <(*(logical(kind=4)[3] * restrict)
atmp.1.data)[S.4]>)
                      {
                        test.0 = 1;
                        goto L.4;
                      }
                    S.4 = S.4 + 1;
                  }
                L.5:;
              }
              L.4:;
              if (test.0) goto L.1;
            }
            L.3:;
            *c = *c + 1;
            L.1:;
            D.1907 = i == 3;
            i = i + 1;
            if (D.1907) goto L.2;
          }

The middle-end then fails to remove this array.

Compare this to the result of

module mymod
contains
  subroutine bar(a,b,c)
    real, dimension(3,3), intent(in) :: a,b
    integer, intent(out) :: c
    real, parameter :: acc = 1e-4
    integer :: i

    c = 0.
    do i=1,3
       if (abs(a(i,1) - b(i,1)) > acc .or. &
            abs(a(i,2) - b(i,2)) > acc .or. &
            abs(a(i,3) - b(i,3)) > acc) cycle
       c = c + 1
    end do
  end subroutine bar
end module mymod

What the Fortran FE generates here isn't very idiomatic when you
write in a language like C.  Should we tackle this in the middle
end, or would issuing the version with .or instead of the ANY
to the middle end be preferred?