[flang] [llvm] [mlir] [OpenMP][flang] Lowering of OpenMP custom reductions to MLIR (PR #168417)

[Tom Eccles via llvm-commits]

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@@ -0,0 +1,112 @@
+! This test checks lowering of OpenMP declare reduction Directive, with initialization
+! via a subroutine. This functionality is currently not implemented.
+
+!RUN: %flang_fc1 -emit-hlfir -fopenmp -fopenmp-version=52 %s -o - | FileCheck %s
+module maxtype_mod
+  implicit none
+
+  type maxtype
+     integer::sumval
+     integer::maxval
+  end type maxtype
+
+contains
+
+  subroutine initme(x,n)
+    type(maxtype) :: x,n
+    x%sumval=0
+    x%maxval=0
+  end subroutine initme
+
+  function mycombine(lhs, rhs)
+    type(maxtype) :: lhs, rhs
+    type(maxtype) :: mycombine
+    mycombine%sumval = lhs%sumval + rhs%sumval
+    mycombine%maxval = max(lhs%maxval, rhs%maxval)
+  end function mycombine
+
+  function func(x, n, init)
+    type(maxtype) :: func
+    integer :: n, i
+    type(maxtype) :: x(n)
+    type(maxtype) :: init
+    type(maxtype) :: res
+!$omp declare reduction(red_add_max:maxtype:omp_out=mycombine(omp_out,omp_in)) initializer(initme(omp_priv,omp_orig))
+    res=init
+!$omp simd reduction(red_add_max:res)
+    do i=1,n
+       res=mycombine(res,x(i))
+    enddo
+    func=res
+  end function func
+
+end module maxtype_mod
+!CHECK:  omp.declare_reduction @red_add_max : [[MAXTYPE:.*]] init {
+!CHECK:  ^bb0(%[[OMP_ORIG_ARG_I:.*]]: [[MAXTYPE]]):
+!CHECK:    %[[OMP_PRIV:.*]] = fir.alloca [[MAXTYPE]]
+!CHECK:    %[[OMP_ORIG:.*]] = fir.alloca [[MAXTYPE]]
+!CHECK:    fir.store %[[OMP_ORIG_ARG_I]] to %[[OMP_ORIG]] : !fir.ref<[[MAXTYPE]]>
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tblah wrote:

As I understand this PR, this will also apply to CPU reductions (thank you for implementing this!). Please could you add a test to make sure a todo message is generated for these types that need library calls instead of a misscompile.

https://github.com/llvm/llvm-project/pull/168417