[Bug c++/38650] New: [4.3/4.4 regression] Trouble with volatile and #pragma omp for

[Bug c++/38650] New: [4.3/4.4 regression] Trouble with volatile and #pragma omp for

[reichelt at gcc dot gnu dot org]

There is some strange behavior with #pragma omp for and volatiles:

=================================
void foo()
{
  volatile int i, j = 1;
#pragma omp for
  for (i = 0; i < j; i += 1)
    ;
}
=================================

bug.cc: In function 'void foo()':
bug.cc:4: internal compiler error: in gimplify_omp_for, at gimplify.c:5880
Please submit a full bug report, [etc.]

A similar code snippet (using ++i instead of i+=1 as incrememt) is accepted:

=================================
void foo()
{
  volatile int i, j = 1;
#pragma omp for
  for (i = 0; i < j; ++i)
    ;
}
=================================

Another slight variation (using i<1 instead of i<j as loop condition)
is rejected:

=================================
void foo()
{
  volatile int i;
#pragma omp for
  for (i = 0; i < 1; ++i)
    ;
}
=================================

bug.cc: In function 'void foo()':
bug.cc:5: error: invalid controlling predicate

The above only holds for the C++ frontend since GCC 4.3.0.
With the C frontend or GCC 4.2.x all three snippets compile fine.


I looked into the specification of OpenMP 3.0 and found nothing forbidding
the use of volatiles as loop counters. On the other hand volatile is IMHO
against the semantics of parallel for where magically changing loop counters
would make no sense. Maybe that's even a defect of the OpenMP specification.


-- 
           Summary: [4.3/4.4 regression] Trouble with volatile and #pragma
                    omp for
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Keywords: ice-on-valid-code, rejects-valid, monitored, openmp
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: reichelt at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38650

[Bug c++/38650] [4.3/4.4 regression] Trouble with volatile and #pragma omp for

[reichelt at gcc dot gnu dot org]

-- 

reichelt at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |4.3.3


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38650

[Bug c++/38650] [4.3/4.4 regression] Trouble with volatile and #pragma omp for

[jakub at gcc dot gnu dot org]

-- 

jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |jakub at gcc dot gnu dot org
                   |dot org                     |
             Status|UNCONFIRMED                 |ASSIGNED
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2008-12-28 17:50:13
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38650

[Bug c++/38650] [4.3/4.4 regression] Trouble with volatile and #pragma omp for

[jakub at gcc dot gnu dot org]

------- Comment #1 from jakub at gcc dot gnu dot org  2008-12-28 20:07 -------
Subject: Bug 38650

Author: jakub
Date: Sun Dec 28 20:06:00 2008
New Revision: 142940

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=142940
Log:
        PR c++/38650
        * semantics.c (finish_omp_for): Don't add CLEANUP_POINT_EXPR
        around volatile iteration var in condition and/or increment
        expression.

        * testsuite/libgomp.c/pr38650.c: New test.
        * testsuite/libgomp.c++/pr38650.C: New test.

Added:
    trunk/libgomp/testsuite/libgomp.c++/pr38650.C
    trunk/libgomp/testsuite/libgomp.c/pr38650.c
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/semantics.c
    trunk/libgomp/ChangeLog


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38650

[Bug c++/38650] [4.3 regression] Trouble with volatile and #pragma omp for

[jakub at gcc dot gnu dot org]

------- Comment #2 from jakub at gcc dot gnu dot org  2008-12-28 20:10 -------
Fixed on the trunk so far.


-- 

jakub at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|                            |4.3.2
      Known to work|                            |4.4.0
            Summary|[4.3/4.4 regression] Trouble|[4.3 regression] Trouble
                   |with volatile and #pragma   |with volatile and #pragma
                   |omp for                     |omp for


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38650

[Bug c++/38650] [4.3 regression] Trouble with volatile and #pragma omp for

[rguenth at gcc dot gnu dot org]

-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38650

[Bug c++/38650] [4.3 regression] Trouble with volatile and #pragma omp for

[rguenth at gcc dot gnu dot org]

------- Comment #3 from rguenth at gcc dot gnu dot org  2009-01-24 10:21 -------
GCC 4.3.3 is being released, adjusting target milestone.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.3.3                       |4.3.4


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38650

[Bug c++/38650] [4.3 regression] Trouble with volatile and #pragma omp for

[rguenth at gcc dot gnu dot org]

------- Comment #4 from rguenth at gcc dot gnu dot org  2009-08-04 12:29 -------
GCC 4.3.4 is being released, adjusting target milestone.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.3.4                       |4.3.5


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38650

[Bug c++/38650] [4.3 regression] Trouble with volatile and #pragma omp for

[rguenth at gcc dot gnu dot org]

------- Comment #5 from rguenth at gcc dot gnu dot org  2010-05-22 18:13 -------
GCC 4.3.5 is being released, adjusting target milestone.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.3.5                       |4.3.6


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38650