[flang][hlfir] Use actual type when copying an actual argument variable

[jeanPerier]

Summary

The copy must made according to the actual type, not the dummy type. In
case the dummy is polymorphic, these types will be different and the
dynamic type of the copy passed in the call should be the one of the
actual.

There is no support for "class(t), value" yet (it is hitting a TODO in
CallInterface that is moot for HLFIR but has not been lifted for lack of
proper testing) so the bug was dormant, but D151271 created a situation
where a copy is needed with polymorphic dummies and exposed the bug.
This led to a compile time assert
"value.isScalar() && fir::isa_trivial(value.getType())" in "hlfir::genAssociateExpr".

[vzakhari]

Thank you, Jean!

flang/lib/Lower/ConvertCall.cpp

if (arg.hasValueAttribute() ||
         // Constant expressions might be lowered as variables with
         // 'parameter' attribute. Even though the constant expressions
         // are not definable and explicit assignments to them are not
         // possible, we have to create a temporary copies when we pass
         // them down the call stack.
         entity.isParameter()) {
       // Make a copy in a temporary.
       auto copy = builder.create<hlfir::AsExprOp>(loc, entity);
+      mlir::Type storageType = entity.getType();
       hlfir::AssociateOp associate = hlfir::genAssociateExpr(
-          loc, builder, hlfir::Entity{copy}, dummyType, "adapt.valuebyref");
+          loc, builder, hlfir::Entity{copy}, storageType, "adapt.valuebyref");
       entity = hlfir::Entity{associate.getBase()};
       // Register the temporary destruction after the call.
       preparedDummy.setExprAssociateCleanUp(
           associate.getFirBase(), associate.getMustFreeStrorageFlag());
     } else if (mustDoCopyInOut) {
       // Copy-in non contiguous variables.
       assert(entity.getType().isa<fir::BaseBoxType>() &&
              "expect non simply contiguous variables to be boxes");

flang/test/Lower/HLFIR/calls-constant-expr-arg-polymorphic.f90

+! RUN: bbc -emit-fir -hlfir --polymorphic-type -o - %s | FileCheck %s
+
+! Test when constant argument are copied in memory
+! and passed to polymorphic arguments.
+! The copy is done in case the dummy later appear in a
+! copy-out that would create write to this memory location.
+  type t1
+    integer :: i
+  end type
+  type, extends(t1) :: t2
+    integer :: j
+  end type
+  interface
+  subroutine foo(x)
+    import :: t1
+    class(t1) :: x(:)
+  end subroutine
+  end interface
+
+  call foo([t2(0,0)])
+end
+! CHECK-LABEL:   func.func @_QQmain() {
+! CHECK:           %[[VAL_3:.*]]:2 = hlfir.declare %{{.*}}(%[[VAL_2:.*]]) {fortran_attrs = #fir.var_attrs<parameter>, uniq_name = "_QQro.1x_QFTt2.0"}
+! CHECK:           %[[VAL_4:.*]] = hlfir.as_expr %[[VAL_3]]#0 : (!fir.ref<!fir.array<1x!fir.type<_QFTt2{i:i32,j:i32}>>>) -> !hlfir.expr<1x!fir.type<_QFTt2{i:i32,j:i32}>>
+! CHECK:           %[[VAL_5:.*]]:3 = hlfir.associate %[[VAL_4]](%[[VAL_2]]) {uniq_name = "adapt.valuebyref"} : (!hlfir.expr<1x!fir.type<_QFTt2{i:i32,j:i32}>>, !fir.shape<1>) -> (!fir.ref<!fir.array<1x!fir.type<_QFTt2{i:i32,j:i32}>>>, !fir.ref<!fir.array<1x!fir.type<_QFTt2{i:i32,j:i32}>>>, i1)
+! CHECK:           %[[VAL_6:.*]] = fir.embox %[[VAL_5]]#0(%[[VAL_2]]) : (!fir.ref<!fir.array<1x!fir.type<_QFTt2{i:i32,j:i32}>>>, !fir.shape<1>) -> !fir.box<!fir.array<1x!fir.type<_QFTt2{i:i32,j:i32}>>>
+! CHECK:           %[[VAL_7:.*]] = fir.convert %[[VAL_6]] : (!fir.box<!fir.array<1x!fir.type<_QFTt2{i:i32,j:i32}>>>) -> !fir.class<!fir.array<?x!fir.type<_QFTt1{i:i32}>>>
+! CHECK:           fir.call @_QPfoo(%[[VAL_7]]) {{.*}}: (!fir.class<!fir.array<?x!fir.type<_QFTt1{i:i32}>>>) -> ()
+! CHECK:           hlfir.end_associate %[[VAL_5]]#1, %[[VAL_5]]#2 : !fir.ref<!fir.array<1x!fir.type<_QFTt2{i:i32,j:i32}>>>, i1