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, 12 insertions, 11 deletions

diff --git a/gcc/ada/einfo.ads b/gcc/ada/einfo.ads
index 4870684..2496400 100644
--- a/gcc/ada/einfo.ads
+++ b/gcc/ada/einfo.ads
@@ -1305,6 +1305,16 @@ package Einfo is
 --       type. Empty for access-to-subprogram types. Empty for access types
 --       whose designated type does not need finalization actions.
 
+--    Finalization_Master_Node_Or_Object
+--       Defined in variables and constants that require finalization actions.
+--       The field contains the entity of an object (called a Master_Node) that
+--       contains the address of the finalizable object, along with an access
+--       value denoting the finalizable object's finalization procedure. The
+--       Master_Node may be attached to a finalization list associated with
+--       either the global scope or some dynamic scope (block or subprogram).
+--       Conversely, for a Master_Node entity, the field contains the entity
+--       of the finalizable object.
+
 --    Finalize_Storage_Only [base type only]
 --       Defined in all types. Set on direct controlled types to which a
 --       valid Finalize_Storage_Only pragma applies. This flag is also set on
@@ -4513,15 +4523,6 @@ package Einfo is
 --       from another predicate but does not add a predicate of its own, the
 --       expression may consist of the above xxxPredicate call on its own.
 
---    Status_Flag_Or_Transient_Decl
---       Defined in constant, loop, and variable entities. Applies to objects
---       that require special treatment by the finalization machinery, such as
---       extended return objects, conditional expression results, and objects
---       inside N_Expression_With_Actions nodes. The attribute contains the
---       entity of a flag which specifies a particular behavior over a region
---       of the extended return for the return objects, or the declaration of a
---       hook object for conditional expressions and N_Expression_With_Actions.
-
 --    Storage_Size_Variable [implementation base type only]
 --       Defined in access types and task type entities. This flag is set
 --       if a valid and effective pragma Storage_Size applies to the base
@@ -5294,7 +5295,6 @@ package Einfo is
    --    Esize
    --    Extra_Accessibility                   (constants only)
    --    Alignment
-   --    Status_Flag_Or_Transient_Decl
    --    Actual_Subtype
    --    Renamed_Object
    --    Renamed_Entity $$$
@@ -5304,6 +5304,7 @@ package Einfo is
    --    Related_Type                          (constants only)
    --    Initialization_Statements
    --    BIP_Initialization_Call
+   --    Finalization_Master_Node_Or_Object
    --    Last_Aggregate_Assignment
    --    Activation_Record_Component
    --    Encapsulating_State                   (constants only)
@@ -6174,7 +6175,6 @@ package Einfo is
    --    Esize
    --    Extra_Accessibility
    --    Alignment
-   --    Status_Flag_Or_Transient_Decl        (transient object only)
    --    Unset_Reference
    --    Actual_Subtype
    --    Renamed_Object
@@ -6191,6 +6191,7 @@ package Einfo is
    --    Related_Type
    --    Initialization_Statements
    --    BIP_Initialization_Call
+   --    Finalization_Master_Node_Or_Object
    --    Last_Aggregate_Assignment
    --    Activation_Record_Component
    --    Encapsulating_State