[Patch, fortran] PR 50690 Disable common function elimination in WORKSHAREs

[Thomas Koenig]

Hi Jakub,

> I think disabling these optimizations in workshare/parallel workshare
> is reasonable, though perhaps you could enable it again in
> EXEC_OMP_PARALLEL{,_DO,_SECTIONS} nested in the
> EXEC_OMP_WORKSHARE/EXEC_OMP_PARALLEL_WORKSHARE.
>
> E.g. in
>    $omp parallel workshare
>      a = b
>      $omp parallel
>        c = cos(d) + cos(d)
>      $omp end parallel
>      e = f
>    $omp end parallel workshare
> the body of the inner $omp parallel can be optimized just fine.
>
> 	Jakub
>

I worked out a patch which does this.  However, in testing it, I came
across some very strange behavior (even without my patch):

With the program

program foo
   implicit none
   integer, parameter :: n = 100000000
   real, parameter :: eps = 3e-7
   integer :: i,j
   real :: A(n), B(5), C(n)
   real :: tmp
   B(1) = 3.344
   tmp = B(1)
   do i=1,10
      call random_number(a)
      c = a
      !$omp parallel default(shared)
      A(:) = A(:)*cos(B(1))+A(:)*cos(B(1))
      !$omp end parallel
   end do

   c = c*cos(b(1))+ c*cos(b(1))

   do j=1,n
      if (abs(a(j)-c(j)) > eps) then
         print *,1,j,a(j), c(j)
         call abort
      end if
   end do

end program foo

I get (without front end optimization, no __var in the .original dump)

ig25@linux-fd1f:~/Krempel/OMP> gfortran -fdump-tree-original -fopenmp 
workshare3.f90
ig25@linux-fd1f:~/Krempel/OMP> grep __var workshare3.f90.003t.original
ig25@linux-fd1f:~/Krempel/OMP> ./a.out
            1           1   2.95472956     -0.392916918

A fatal error occurred! Backtrace for this error:
#0  0x2BA3B412CF67
#1  0x2BA3B412E4B6
#2  0x2BA3B41F7318
#3  0x400E14 in MAIN__ at workshare3.f90:0
Abgebrochen

Is this a bug in my program or in the openmp implementation?

Regards

	Thomas