ada: Partial implementation of redesign of support for object finalization

This set of changes is a partial reimplemention of the support for Ada
finalization in the GNAT compiler and run-time library, based on the
redesign done by Hristian Kirtchev in February 2022.  It only affects
the scope-based finalization of objects and does not touch the support
for finalization of dynamically allocated objects.

It also does not modify the internal architecture of this support in the
front-end but only changes its output, i.e. the expanded code.  In other
words, the code-based dispatching scheme in finalizers and the hook-based
approach for transient objects are replaced by finalization scope masters
and master nodes, which maintain a list of objects needing finalization,
but the expansion of the code that builds these masters is still performed
mainly during a dedicated post-processing phase.

gcc/ada/

	* Makefile.rtl (GNATRTL_NONTASKING_OBJS): Add s-finpri$(objext).
	* contracts.adb (Add_Call_Helper): Append freeze actions to the
	class-wide type rather than the specific tagged type.
	* einfo.ads (Finalization_Master_Node_Or_Node): Document.
	(Status_Flag_Or_Transient_Decl): Remove.
	* exp_attr.adb (Expand_N_Attribute_Reference) <Address>: Do not
	adjust a return object of a class-wide interface type.
	* exp_ch3.adb  (Expand_Freeze_Class_Wide_Type): Add test that
	Finalize_Address is not already present as a condition for calling
	Make_Finalize_Address_Body.
	(Expand_Freeze_Record_Type): Call Make_Finalize_Address_Body for
	class-wide types of both regular tagged types and interface types.
	* exp_ch4.adb (Process_Transients_In_Expression): Replace the use
	of hooks with the use of master nodes.
	* exp_ch6.adb (Build_Flag_For_Function): Delete.
	(Expand_N_Extended_Return_Statement): Create a master node for the
	return object if it does not exist.  At the end of the statement,
	generate a call to Suppress_Object_Finalize.
	(Expand_Non_Function_Return): Likewise just before the return.
	* exp_ch7.ads (Make_Master_Node_Declaration): Declare.
	(Make_Suppress_Object_Finalize_Call): Likewise.
	* exp_ch7.adb (Build_Finalization_Master): Defer generating the
	call to Set_Finalize_Address until freezing if the Finalize_Address
	procedure has not been analyzed yet.
	(Build_Finalizer): Reimplement the expansion using a finalization
	scope master per finalizer.
	(Insert_Actions_In_Scope_Around): Replace finalization hooks by
	master nodes and calls to the Finalize_Object.
	(Make_Master_Node_Declaration): New procedure.
	(Make_Suppress_Object_Finalize_Call): Likewise.
	* exp_util.ads (Build_Transient_Object_Statements): Delete.
	* exp_util.adb (Build_Transient_Object_Statements): Likewise.
	(Requires_Cleanup_Actions): Remove obsolete code and return true
	for master nodes.
	* gen_il-fields.ads (Opt_Field_Enum): Add
	Finalization_Master_Node_Or_Object and
	remove Status_Flag_Or_Transient_Decl.
	* gen_il-gen-gen_entities.adb (Allocatable_Kind): Likewise.
	* rtsfind.ads (RTU_Id): Add System_Finalization_Primitives.
	(RE_Id): Add entities of System_Finalization_Primitives.
	(RE_Unit_Table): Add entries for them.
	* sem_ch3.adb (Analyze_Object_Declaration): For an array whose type
	has an unconstrained first subtype and a controlled component, set
	the Is_Constr_Array_Subt_With_Bounds flag.
	* libgnat/s-finpri.ads: New file.
	* libgnat/s-finpri.adb: Likewise.

1 files changed, 4 insertions, 3 deletions

diff --git a/gcc/ada/exp_attr.adb b/gcc/ada/exp_attr.adb
index 8f32dc2..614f1fb 100644
--- a/gcc/ada/exp_attr.adb
+++ b/gcc/ada/exp_attr.adb
@@ -2701,13 +2701,14 @@ package body Exp_Attr is
          --  activation record object where the component corresponds to
          --  prefix of the attribute (for back ends that require "unnesting"
          --  of nested subprograms), since the address needs to be assigned
-         --  as-is to such components.
+         --  as-is to such components. Likewise for a return object.
 
          elsif Tagged_Type_Expansion
            and then Is_Class_Wide_Type (Ptyp)
            and then Is_Interface (Underlying_Type (Ptyp))
-           and then not (Nkind (Pref) in N_Has_Entity
-                          and then Is_Subprogram (Entity (Pref)))
+           and then not (Is_Entity_Name (Pref)
+                          and then (Is_Subprogram (Entity (Pref))
+                                     or else Is_Return_Object (Entity (Pref))))
            and then not Is_Unnested_Component_Init (N)
          then
             Rewrite (N,