[Bug middle-end/40205] OpenMP do loop with MAXINT gives wrong trip count

[Bug middle-end/40205] OpenMP do loop with MAXINT gives wrong trip count

[pkeir at outlook dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40205

--- Comment #3 from Paul Keir <pkeir at outlook dot com> 2012-09-30 21:29:22 UTC ---
Still present in GFortran 4.7.2 on 32-bit Ubuntu 12.04.1.

[Bug middle-end/40205] OpenMP do loop with MAXINT gives wrong trip count

[burnus at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40205

Tobias Burnus <burnus at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |burnus at gcc dot gnu.org
         Resolution|                            |WONTFIX

--- Comment #4 from Tobias Burnus <burnus at gcc dot gnu.org> 2012-10-17 17:10:40 UTC ---
(In reply to comment #0)
>   upper = huge(maxint)
>   lower = upper - 9    ! The 9 can of course be changed
> !$omp parallel do
>   do i = lower, upper

As the Fortran program is nonconforming (even without OpenMP), I close this PR
as WONTFIX.

The reason that the program is nonconforming is the same as the OpenMP issue:
One has "huge(i)+1" which is not representable.

In case of Fortran, the standard effectively mandates that the DO variable "i"
is "upper + 1" after the loop, but that number is not representable if "upper"
is "huge(i)". As it is not representable, the code is nonconforming. See PR
54932 for quotes from the standard.

(For the OpenMP part, one has "<= ubound" which is transformed to "< ubound+1".
That part could be fixed, but why should one bother if the Fortran code itself
is already invalid.)

[Bug middle-end/40205] OpenMP do loop with MAXINT gives wrong trip count

[steven at gcc dot gnu dot org]

------- Comment #2 from steven at gcc dot gnu dot org  2009-09-26 10:15 -------
Jakub, OpenMP bug, is this something you have time for?


-- 

steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40205

[Bug middle-end/40205] OpenMP do loop with MAXINT gives wrong trip count

[rguenth at gcc dot gnu dot org]

------- Comment #1 from rguenth at gcc dot gnu dot org  2009-05-20 11:28 -------
Confirmed.  extract_omp_for_data "canonicalizes" <= and >= to < and > by
adding/subtracting one to/from the bound.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
          Component|fortran                     |middle-end
     Ever Confirmed|0                           |1
           Keywords|                            |wrong-code
   Last reconfirmed|0000-00-00 00:00:00         |2009-05-20 11:28:36
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40205