12.3. Placement of flush, barrier, taskwait and taskyield Directives

The following example is non-conforming, because the flush, barrier, taskwait, and taskyield directives are stand-alone directives and cannot be the immediate substatement of an if statement.

//%compiler: clang
//%cflags: -fopenmp

/*
* name: standalone.1
* type: C
* version: omp_3.1
*/

void standalone_wrong()
{
  int a = 1;

 if (a != 0)
  #pragma omp flush(a)
/* incorrect as flush cannot be immediate substatement
   of if statement */

 if (a != 0)
  #pragma omp barrier
/* incorrect as barrier cannot be immediate substatement
   of if statement */

 if (a!=0)
  #pragma omp taskyield
/* incorrect as taskyield cannot be immediate substatement of if statement
*/

 if (a != 0)
  #pragma omp taskwait
/* incorrect as taskwait cannot be immediate substatement
   of if statement */

}

The following example is non-conforming, because the flush, barrier, taskwait, and taskyield directives are stand-alone directives and cannot be the action statement of an if statement or a labeled branch target.

!!%compiler: gfortran
!!%cflags: -fopenmp

! name: standalone.1
! type: F-free
! version:     omp_3.1


SUBROUTINE STANDALONE_WRONG()

  INTEGER  A

  A = 1

  ! the FLUSH directive must not be the action statement
  ! in an IF statement
  IF (A .NE. 0) !$OMP FLUSH(A)

  ! the BARRIER directive must not be the action statement
  ! in an IF statement
  IF (A .NE. 0) !$OMP BARRIER

  ! the TASKWAIT directive must not be the action statement
  ! in an IF statement
  IF (A .NE. 0) !$OMP TASKWAIT

  ! the TASKYIELD directive must not be the action statement
  ! in an IF statement
  IF (A .NE. 0) !$OMP TASKYIELD

  GOTO 100

  ! the FLUSH directive must not be a labeled branch target
  ! statement
  100 !$OMP FLUSH(A)
  GOTO 200

  ! the BARRIER directive must not be a labeled branch target
  ! statement
  200 !$OMP BARRIER
  GOTO 300

  ! the TASKWAIT directive must not be a labeled branch target
  ! statement
  300 !$OMP TASKWAIT
  GOTO 400

  ! the TASKYIELD directive must not be a labeled branch target
  ! statement
  400 !$OMP TASKYIELD

END SUBROUTINE

The following version of the above example is conforming because the flush, barrier, taskwait, and taskyield directives are enclosed in a compound statement.

//%compiler: clang
//%cflags: -fopenmp

/*
* name: standalone.2
* type: C
* version: omp_3.1
*/
void standalone_ok()
{
  int a = 1;

  #pragma omp parallel
  {
     if (a != 0) {
  #pragma omp flush(a)
     }
     if (a != 0) {
  #pragma omp barrier
     }
     if (a != 0) {
  #pragma omp taskwait
     }
 if (a != 0) {
  #pragma omp taskyield
 }
  }
}

The following example is conforming because the flush, barrier, taskwait, and taskyield directives are enclosed in an if construct or follow the labeled branch target.

!!%compiler: gfortran
!!%cflags: -fopenmp

! name: standalone.2
! type: F-free
! version:     omp_3.1
SUBROUTINE STANDALONE_OK()
  INTEGER  A
  A = 1
  IF (A .NE. 0) THEN
    !$OMP FLUSH(A)
  ENDIF
  IF (A .NE. 0) THEN
    !$OMP BARRIER
  ENDIF
  IF (A .NE. 0) THEN
    !$OMP TASKWAIT
  ENDIF
  IF (A .NE. 0) THEN
    !$OMP TASKYIELD
  ENDIF
  GOTO 100
  100 CONTINUE
  !$OMP FLUSH(A)
  GOTO 200
  200 CONTINUE
  !$OMP BARRIER
  GOTO 300
  300 CONTINUE
  !$OMP TASKWAIT
  GOTO 400
  400 CONTINUE
  !$OMP TASKYIELD
END SUBROUTINE