[flang] Add runtime default initialization for polymorphic intent(out) dummy

[clementval]

Summary

This patch adds runtime default initialization for polymorphic
dummy argument. The dynamic type might require default initialization
but not the declared type.

[clementval]

Do it for polymorphic dummy as the dynamic type might
require default initialization but not the declared type

[PeteSteinfeld]

Aside from the question on the comment, all builds and tests correctly and looks good.

flang/lib/Lower/ConvertVariable.cpp

628

Shouldn't this comment say "needs" rather than "might need"?

[jeanPerier]

flang/lib/Lower/ConvertVariable.cpp

628

I think "might need" is more accurate in the sense that the storage may not need default initialization: it only needs it if the dynamic type requires it. However, we do not know the dynamic type at compile time, so we must call the runtime, but the runtime may not do anything if the dynamic type turns out to not have a default initial value.

[clementval]

flang/lib/Lower/ConvertVariable.cpp

628

Jean is correct here. We are not sure it need default initialization but since it might we delegate it to the runtime.

flang/lib/Lower/ConvertVariable.cpp

mustBeDefaultInitializedAtRuntime(const Fortran::lower::pft::Variable &var) {
   if (!var.hasSymbol())
     return false;
   const Fortran::semantics::Symbol &sym = var.getSymbol();
   if (var.isGlobal())
     // Global variables are statically initialized.
     return false;
   if (Fortran::semantics::IsDummy(sym) && !Fortran::semantics::IsIntentOut(sym))
     return false;
+  // Polymorphic intent(out) dummy might need default initialization
+  // at runtime.
+  if (Fortran::semantics::IsPolymorphic(sym) &&
+      Fortran::semantics::IsDummy(sym) && Fortran::semantics::IsIntentOut(sym))
+    return true;
   // Local variables (including function results), and intent(out) dummies must
   // be default initialized at runtime if their type has default initialization.
   return hasDefaultInitialization(sym);
 }
 
 /// Call default initialization runtime routine to initialize \p var.
 static void
 defaultInitializeAtRuntime(Fortran::lower::AbstractConverter &converter,

flang/test/Lower/polymorphic.f90

contains
     generic :: write(formatted) => write_p1
     generic :: assignment(=) => assign_p1_int
     procedure :: host_assoc
     procedure, pass(poly) :: lt
     generic :: operator(<) => lt
   end type
 
   type, extends(p1) :: p2
-    real :: c
+    real :: c = 10.5
   end type
 
   type r1
     real, pointer :: rp(:) => null()
   end type
 
   type c1
     character(2) :: tmp = 'c1'
subroutine test_unlimited_polymorphic_alloc_array_ret()
     end select
   end subroutine
 
 ! CHECK-LABEL: func.func @_QMpolymorphic_testPtest_unlimited_polymorphic_alloc_array_ret() {
 ! CHECK: %[[RES_TMP:.*]] = fir.alloca !fir.class<!fir.heap<!fir.array<?xnone>>> {bindc_name = ".result"}
 ! CHECK: %[[RES:.*]] = fir.call @_QMpolymorphic_testPunlimited_polymorphic_alloc_array_ret() fastmath<contract> : () -> !fir.class<!fir.heap<!fir.array<?xnone>>>
 ! CHECK: fir.save_result %[[RES]] to %[[RES_TMP]] : !fir.class<!fir.heap<!fir.array<?xnone>>>, !fir.ref<!fir.class<!fir.heap<!fir.array<?xnone>>>>
 
+  subroutine test_unlimited_polymorphic_intentout(a)
+    class(*), intent(out) :: a
+  end subroutine
+
+! CHECK-LABEL: func.func @_QMpolymorphic_testPtest_unlimited_polymorphic_intentout(
+! CHECK-SAME: %[[ARG0:.*]]: !fir.class<none> {fir.bindc_name = "a"}) {
+! CHECK: %[[BOX_NONE:.*]] = fir.convert %[[ARG0]] : (!fir.class<none>) -> !fir.box<none>
+! CHECK: %{{.*}} = fir.call @_FortranAInitialize(%[[BOX_NONE]], %{{.*}}, %{{.*}}) {{.*}} : (!fir.box<none>, !fir.ref<i8>, i32) -> none
+
+  subroutine test_polymorphic_intentout(a)
+    class(p1), intent(out) :: a
+  end subroutine
+
+! CHECK-LABEL: func.func @_QMpolymorphic_testPtest_polymorphic_intentout(
+! CHECK-SAME: %[[ARG0:.*]]: !fir.class<!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>> {fir.bindc_name = "a"}) {
+! CHECK: %[[BOX_NONE:.*]] = fir.convert %[[ARG0]] : (!fir.class<!fir.type<_QMpolymorphic_testTp1{a:i32,b:i32}>>) -> !fir.box<none>
+! CHECK: %{{.*}} = fir.call @_FortranAInitialize(%[[BOX_NONE]], %{{.*}}, %{{.*}}) {{.*}} : (!fir.box<none>, !fir.ref<i8>, i32) -> none
+
 end module
 
 program test
   use polymorphic_test
   type(outer), allocatable :: o
   integer :: i(5)
   logical :: l(5)
   allocate(o)