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

[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

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

[janus at gcc dot gnu.org]

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

janus at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2011-10-31
     Ever Confirmed|0                           |1

--- Comment #1 from janus at gcc dot gnu.org 2011-10-31 12:08:31 UTC ---
(In reply to comment #0)
> Expected:
> a) gfortran call the procedure directly, which allows for inlining and avoids
> the pointer dereference.

Good point. I hadn't thought of that ...


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

Here is an extended test case involving a type-bound subroutine and a
type-bound function (both of which have to be fixed):


module m

type t
contains
  procedure, nopass, NON_OVERRIDABLE :: testsub
  procedure, nopass, NON_OVERRIDABLE :: testfun
end type t

contains

  subroutine testsub()
    print *, "t's test"
  end subroutine

  integer function testfun()
    testfun = 1
  end function

end module m


  use m
  class(t), allocatable :: x
  allocate(x)
  call x%testsub()
  print *,x%testfun()
end

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

[janus at gcc dot gnu.org]

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

janus at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
         AssignedTo|unassigned at gcc dot       |janus at gcc dot gnu.org
                   |gnu.org                     |

--- Comment #2 from janus at gcc dot gnu.org 2011-10-31 12:31:03 UTC ---
Created attachment 25672
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=25672
patch

Here is a patch, which does two things:
1) The resolve.c part prevents the conversion to a PPC call (for functions and
subroutines).
2) The class.c parts prevents adding the non-overridable TBP to the vtable.

The second one breaks the ABI, while the first one does not. So, should I start
by committing the first part only, and waiting with the second one for the ABI
cleanup?

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

[janus at gcc dot gnu.org]

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

--- Comment #3 from janus at gcc dot gnu.org 2011-10-31 13:55:55 UTC ---
(In reply to comment #2)
> Created attachment 25672 [details]
> patch

... regtests cleanly!

[Bug fortran/50919] [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

--- Comment #4 from Tobias Burnus <burnus at gcc dot gnu.org> 2011-10-31 14:41:19 UTC ---
(In reply to comment #2)
> Created attachment 25672 [details]
> patch

Thanks for the patch!

> The second one breaks the ABI, while the first one does not. So, should I start
> by committing the first part only, and waiting with the second one for the ABI
> cleanup?

I think that's sensible: Submitting/committing the first one. And for the
second part: Add a link to this PR at
http://gcc.gnu.org/wiki/LibgfortranAbiCleanup

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

[janus at gcc dot gnu.org]

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

--- Comment #5 from janus at gcc dot gnu.org 2011-11-07 18:41:16 UTC ---
Author: janus
Date: Mon Nov  7 18:41:12 2011
New Revision: 181107

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=181107
Log:
2011-11-07  Janus Weil  <janus@gcc.gnu.org>

    PR fortran/50919
    * class.c (add_proc_comp): Don't add non-overridable procedures to the
    vtable.
    * resolve.c (resolve_typebound_function,resolve_typebound_subroutine):
    Don't generate a dynamic _vptr call for non-overridable procedures.

2011-11-07  Janus Weil  <janus@gcc.gnu.org>

    PR fortran/50919
    * gfortran.dg/typebound_call_21.f03: New.

Added:
    trunk/gcc/testsuite/gfortran.dg/typebound_call_21.f03
Modified:
    trunk/gcc/fortran/ChangeLog
    trunk/gcc/fortran/class.c
    trunk/gcc/fortran/resolve.c
    trunk/gcc/testsuite/ChangeLog

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

[janus at gcc dot gnu.org]

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

janus at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED

--- Comment #6 from janus at gcc dot gnu.org 2011-11-07 18:46:27 UTC ---
Fixed with r181107 (including both parts of the patch in comment 2). Closing.