[flang] Add TODO for polymorphic array argument in elemental procedure

[jeanPerier]

Summary

The current lowering fails to retrieve the shape of polymorphic array
arguments in elemental procedure reference.
Add a TODO because this is supported in the new HLFIR lowering, and
because the current lowering anyway attempts to re-evaluate the
argument to get its shape, which is not correct if the evaluation
has side effects.

Add a test to ensure this is supported with HLFIR.

[PeteSteinfeld]

All builds and tests correctly and looks good.

flang/lib/Lower/ConvertExpr.cpp

llvm::SmallVector<mlir::Value> genIterationShape() {
     // Otherwise, in elemental context, try to find the passed object and
     // retrieve the iteration shape from it.
     if (loweredProcRef && loweredProcRef->IsElemental()) {
       const std::optional<Fortran::evaluate::ActualArgument> passArg =
           extractPassedArgFromProcRef(*loweredProcRef, converter);
       if (passArg) {
         ExtValue exv = asScalarRef(*passArg->UnwrapExpr());
         fir::FirOpBuilder *builder = &converter.getFirOpBuilder();
-        return fir::factory::getExtents(getLoc(), *builder, exv);
+        auto extents = fir::factory::getExtents(getLoc(), *builder, exv);
+        if (extents.size() == 0)
+          TODO(getLoc(), "getting shape from polymorphic array in elemental "
+                         "procedure reference");
+        return extents;
       }
     }
     fir::emitFatalError(getLoc(),
                         "failed to compute the array expression shape");
   }
 
   bool explicitSpaceIsActive() const {
     return explicitSpace && explicitSpace->isActive();

flang/test/Lower/HLFIR/elemental-user-procedure-ref-polymorphic.f90

+! Test lowering of user defined elemental procedure reference to HLFIR
+! With polymorphic arguments.
+! RUN: bbc -emit-fir -hlfir -I nw -polymorphic-type -o - %s 2>&1 | FileCheck %s
+module def_some_types
+  type :: t
+    integer :: i
+  end type
+end module
+
+subroutine test_polymporphic_array(scalar)
+  use def_some_types
+  interface
+    function return_array_with_side_effects()
+      import :: t
+      class(t), pointer :: return_array_with_side_effects(:)
+    end function
+    integer elemental function elem(lhs, rhs)
+      import :: t
+      class(t), intent(in) :: lhs, rhs
+    end function elem
+  end interface
+  class(t) :: scalar
+  call bar(elem(scalar, return_array_with_side_effects()))
+contains
+end
+
+! CHECK-LABEL:   func.func @_QPtest_polymporphic_array(
+! CHECK:  %[[VAL_1:.*]] = fir.alloca !fir.class<!fir.ptr<!fir.array<?x!fir.type<_QMdef_some_typesTt{i:i32}>>>> {bindc_name = ".result"}
+! CHECK:  %[[VAL_2:.*]]:2 = hlfir.declare {{.*}}scalar
+! CHECK:  %[[VAL_3:.*]] = fir.call @_QPreturn_array_with_side_effects() {{.*}}: () -> !fir.class<!fir.ptr<!fir.array<?x!fir.type<_QMdef_some_typesTt{i:i32}>>>>
+! CHECK:  fir.save_result %[[VAL_3]] to %[[VAL_1:.*]] : !fir.class<!fir.ptr<!fir.array<?x!fir.type<_QMdef_some_typesTt{i:i32}>>>>, !fir.ref<!fir.class<!fir.ptr<!fir.array<?x!fir.type<_QMdef_some_typesTt{i:i32}>>>>>
+! CHECK:  %[[VAL_4:.*]]:2 = hlfir.declare %[[VAL_1]] {uniq_name = ".tmp.func_result"} : (!fir.ref<!fir.class<!fir.ptr<!fir.array<?x!fir.type<_QMdef_some_typesTt{i:i32}>>>>>) -> (!fir.ref<!fir.class<!fir.ptr<!fir.array<?x!fir.type<_QMdef_some_typesTt{i:i32}>>>>>, !fir.ref<!fir.class<!fir.ptr<!fir.array<?x!fir.type<_QMdef_some_typesTt{i:i32}>>>>>)
+! CHECK:  %[[VAL_5:.*]] = fir.load %[[VAL_4]]#0 : !fir.ref<!fir.class<!fir.ptr<!fir.array<?x!fir.type<_QMdef_some_typesTt{i:i32}>>>>>
+! CHECK:  %[[VAL_6:.*]] = arith.constant 0 : index
+! CHECK:  %[[VAL_7:.*]]:3 = fir.box_dims %[[VAL_5]], %[[VAL_6]] : (!fir.class<!fir.ptr<!fir.array<?x!fir.type<_QMdef_some_typesTt{i:i32}>>>>, index) -> (index, index, index)
+! CHECK:  %[[VAL_8:.*]] = fir.shape %[[VAL_7]]#1 : (index) -> !fir.shape<1>
+! CHECK:  %[[VAL_9:.*]] = hlfir.elemental %[[VAL_8]] : (!fir.shape<1>) -> !hlfir.expr<?xi32> {
+! CHECK:  ^bb0(%[[VAL_10:.*]]: index):
+! CHECK:    %[[VAL_11:.*]] = arith.constant 0 : index
+! CHECK:    %[[VAL_12:.*]]:3 = fir.box_dims %[[VAL_5]], %[[VAL_11]] : (!fir.class<!fir.ptr<!fir.array<?x!fir.type<_QMdef_some_typesTt{i:i32}>>>>, index) -> (index, index, index)
+! CHECK:    %[[VAL_13:.*]] = arith.constant 1 : index
+! CHECK:    %[[VAL_14:.*]] = arith.subi %[[VAL_12]]#0, %[[VAL_13]] : index
+! CHECK:    %[[VAL_15:.*]] = arith.addi %[[VAL_10]], %[[VAL_14]] : index
+! CHECK:    %[[VAL_16:.*]] = hlfir.designate %[[VAL_5]] (%[[VAL_15]])  : (!fir.class<!fir.ptr<!fir.array<?x!fir.type<_QMdef_some_typesTt{i:i32}>>>>, index) -> !fir.class<!fir.type<_QMdef_some_typesTt{i:i32}>>
+! CHECK:    %[[VAL_17:.*]] = fir.call @_QPelem(%[[VAL_2]]#0, %[[VAL_16]]) {{.*}}: (!fir.class<!fir.type<_QMdef_some_typesTt{i:i32}>>, !fir.class<!fir.type<_QMdef_some_typesTt{i:i32}>>) -> i32
+! CHECK:    hlfir.yield_element %[[VAL_17]] : i32
+! CHECK:  }
+! CHECK:  %[[VAL_18:.*]]:3 = hlfir.associate %[[VAL_9]](%[[VAL_8]]) {uniq_name = "adapt.valuebyref"} : (!hlfir.expr<?xi32>, !fir.shape<1>) -> (!fir.box<!fir.array<?xi32>>, !fir.ref<!fir.array<?xi32>>, i1)
+! CHECK:  fir.call @_QPbar(%[[VAL_18]]#1) {{.*}}: (!fir.ref<!fir.array<?xi32>>) -> ()