[FLANG][OpenMP] Support for Custom Reduction

[koparasy]

Is there a plan or a timeline on when we will have custom openmp reduction support on FLANG. The following fails with several errors:

module mymod
  type maxtype
    real :: val
  end type maxtype

!$omp declare reduction(mymax: maxtype : omp_out = getmax(omp_in,omp_out)) initializer(omp_priv=omp_orig)

contains
   function getmax(m1, m2)
      implicit none
!$omp declare target
      type(maxtype), intent(in) :: m1, m2
      type(maxtype) :: getmax

      if (m1%val > m2%val) then
        getmax%val = m1%val
      else
        getmax%val = m2%val
      endif
   end function getmax
end module mymod

[Meinersbur]

As far as I am aware, nobody is working on it yet.

See https://clang.llvm.org/docs/OpenMPSupport.html and https://flang.llvm.org/docs/OpenMPSupport.html for implementation progress.

[kiranchandramohan]

We have added most of the Flang parse-tree and semantic handling for user reduction. The Reduction support in the MLIR mid-end also is capable of handling user reductions. Only the part that connects the parse-tree to the MLIR mid-end is missing. We have been prioritising a few other features and bug fixes over declare reduction support.

For my information: is there an application that requires declare reduction support?

[koparasy]

We have added most of the Flang parse-tree and semantic handling for user reduction. The Reduction support in the MLIR mid-end also is capable of handling user reductions. Only the part that connects the parse-tree to the MLIR mid-end is missing. We have been prioritising a few other features and bug fixes over declare reduction support.

For my information: is there an application that requires declare reduction support?

Yes, one of our internal (not open source) applications require it.

[koparasy]

Is there some rough timeline on when you will have the MLIR mid-end fixed?

[tblah]

Is there some rough timeline on when you will have the MLIR mid-end fixed?

Kiran and I have no immediate plans to work on this. I cannot speak for the other organisations who contribute to flang.