bool *);
static tree gnat_to_gnu_field (Entity_Id, tree, int, bool, bool);
static bool same_discriminant_p (Entity_Id, Entity_Id);
-static bool array_type_has_nonaliased_component (Entity_Id, tree);
+static bool array_type_has_nonaliased_component (tree, Entity_Id);
static bool compile_time_known_address_p (Node_Id);
static bool cannot_be_superflat_p (Node_Id);
static void components_to_record (tree, Node_Id, tree, int, bool, tree *,
{
tem = build_array_type (tem, gnu_index_types[index]);
TYPE_MULTI_ARRAY_P (tem) = (index > 0);
- if (array_type_has_nonaliased_component (gnat_entity, tem))
+ if (array_type_has_nonaliased_component (tem, gnat_entity))
TYPE_NONALIASED_COMPONENT (tem) = 1;
}
{
gnu_type = build_array_type (gnu_type, gnu_index_types[index]);
TYPE_MULTI_ARRAY_P (gnu_type) = (index > 0);
- if (array_type_has_nonaliased_component (gnat_entity, gnu_type))
+ if (array_type_has_nonaliased_component (gnu_type, gnat_entity))
TYPE_NONALIASED_COMPONENT (gnu_type) = 1;
}
gnu_type
= build_array_type (gnat_to_gnu_type (Component_Type (gnat_entity)),
gnu_index_type);
- if (array_type_has_nonaliased_component (gnat_entity, gnu_type))
+ if (array_type_has_nonaliased_component (gnu_type, gnat_entity))
TYPE_NONALIASED_COMPONENT (gnu_type) = 1;
relate_alias_sets (gnu_type, gnu_string_type, ALIAS_SET_COPY);
}
superset superset
R ----------> D ----------> T
+ However, for composite types, conversions between derived types are
+ translated into VIEW_CONVERT_EXPRs so a sequence like:
+
+ type Comp1 is new Comp;
+ type Comp2 is new Comp;
+ procedure Proc (C : Comp1);
+
+ C : Comp2;
+ Proc (Comp1 (C));
+
+ is translated into:
+
+ C : Comp2;
+ Proc ((Comp1 &) &VIEW_CONVERT_EXPR <Comp1> (C));
+
+ and gimplified into:
+
+ C : Comp2;
+ Comp1 *C.0;
+ C.0 = (Comp1 *) &C;
+ Proc (C.0);
+
+ i.e. generates code involving type punning. Therefore, Comp1 needs
+ to conflict with Comp2 and an alias set copy is required.
+
The language rules ensure the parent type is already frozen here. */
if (Is_Derived_Type (gnat_entity))
{
tree gnu_parent_type = gnat_to_gnu_type (Etype (gnat_entity));
- relate_alias_sets (gnu_type, gnu_parent_type, ALIAS_SET_SUPERSET);
+ relate_alias_sets (gnu_type, gnu_parent_type,
+ Is_Composite_Type (gnat_entity)
+ ? ALIAS_SET_COPY : ALIAS_SET_SUPERSET);
}
/* Back-annotate the Alignment of the type if not already in the
Original_Record_Component (discr1) == Original_Record_Component (discr2);
}
-/* Return true if the array type specified by GNAT_TYPE and GNU_TYPE has
- a non-aliased component in the back-end sense. */
+/* Return true if the array type GNU_TYPE, which represents a dimension of
+ GNAT_TYPE, has a non-aliased component in the back-end sense. */
static bool
-array_type_has_nonaliased_component (Entity_Id gnat_type, tree gnu_type)
+array_type_has_nonaliased_component (tree gnu_type, Entity_Id gnat_type)
{
- /* If the type below this is a multi-array type, then
- this does not have aliased components. */
+ /* If the array type is not the innermost dimension of the GNAT type,
+ then it has a non-aliased component. */
if (TREE_CODE (TREE_TYPE (gnu_type)) == ARRAY_TYPE
&& TYPE_MULTI_ARRAY_P (TREE_TYPE (gnu_type)))
return true;
+ /* If the array type has an aliased component in the front-end sense,
+ then it also has an aliased component in the back-end sense. */
if (Has_Aliased_Components (gnat_type))
return false;
+ /* If this is a derived type, then it has a non-aliased component if
+ and only if its parent type also has one. */
+ if (Is_Derived_Type (gnat_type))
+ {
+ tree gnu_parent_type = gnat_to_gnu_type (Etype (gnat_type));
+ int index;
+ if (TREE_CODE (gnu_parent_type) == UNCONSTRAINED_ARRAY_TYPE)
+ gnu_parent_type
+ = TREE_TYPE (TREE_TYPE (TYPE_FIELDS (TREE_TYPE (gnu_parent_type))));
+ for (index = Number_Dimensions (gnat_type) - 1; index > 0; index--)
+ gnu_parent_type = TREE_TYPE (gnu_parent_type);
+ return TYPE_NONALIASED_COMPONENT (gnu_parent_type);
+ }
+
+ /* Otherwise, rely exclusively on properties of the element type. */
return type_for_nonaliased_component_p (TREE_TYPE (gnu_type));
}