[Bug fortran/50919] New: [OOP] Don't use vtable for NON_OVERRIDABLE TBP

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50919

             Bug #: 50919
           Summary: [OOP] Don't use vtable for NON_OVERRIDABLE TBP
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Keywords: missed-optimization
          Severity: normal
          Priority: P3
         Component: fortran
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: burnus@gcc.gnu.org
                CC: janus@gcc.gnu.org


Current, gfortran uses always a vtable for type-bound procedures. However, a
vtable only makes sense if the type-bound procedure can be overridden (C++: if
it is "virtual").

Expected:
a) gfortran call the procedure directly, which allows for inlining and avoids
the pointer dereference.

b) When the ABI is changed, the procedure is no longer added to the vtable.
Hence, it should be added as item to
http://gcc.gnu.org/wiki/LibgfortranAbiCleanup


Test case. The dump shows the following rather than a simple "test ()":

callit (struct __class_m_T & restrict x)
{
  x->_vptr->test ();



module m
type t
contains
  procedure, nopass, NON_OVERRIDABLE :: test
end type t
contains
  subroutine test()
    print *, "t's test"
  end subroutine test

  subroutine callit(x)
    class(t) :: x
    call x%test()
  end subroutine
end module m
tob@archimedes:/dev/shm> less poly.f90.*
tob@archimedes:/dev/shm> cat poly.f90
module m
type t
contains
  procedure, nopass, NON_OVERRIDABLE :: test
end type t
contains
  subroutine test()
    print *, "t's test"
  end subroutine test

  subroutine callit(x)
    class(t) :: x
    call x%test()
  end subroutine
end module m