ada: Implement first half of Generalized Finalization

This implements the first half of the Generalized Finalization proposal,
namely the Finalizable aspect as well as its optional relaxed semantics
for the finalization operations, but the latter part is only implemented
for dynamically allocated objects.

In accordance with the spirit, if not the letter, of the proposal, this
implements the finalizable types declared with strict semantics for the
finalization operations as a direct generalization of controlled types,
which in turn makes it possible to reimplement the latter types in terms
of the former types and ensures full interoperability between them.

The relaxed semantics for the finalization operations is also a direct
generalization of the GNAT pragma No_Heap_Finalization for dynamically
allocated objects, in that it extends the effects of the pragma to all
access types designating the finalizable type, instead of just applying
them to library-level named access types.

gcc/ada/

	* aspects.ads (Aspect_Id): Add Aspect_Finalizable.
	(Implementation_Defined_Aspect): Add True for Aspect_Finalizable.
	(Operational_Aspect): Add True for Aspect_Finalizable.
	(Aspect_Argument): Add Expression for Aspect_Finalizable.
	(Is_Representation_Aspect): Add False for Aspect_Finalizable.
	(Aspect_Names): Add Name_Finalizable for Aspect_Finalizable.
	(Aspect_Delay): Add Always_Delay  for Aspect_Finalizable.
	* checks.adb: Add with and use clauses for Sem_Elab.
	(Install_Primitive_Elaboration_Check): Call Is_Controlled_Procedure.
	* einfo.ads (Has_Relaxed_Finalization): Document new flag.
	(Is_Controlled_Active): Update documentation.
	* exp_aggr.adb (Generate_Finalization_Actions): Replace Find_Prim_Op
	with Find_Controlled_Prim_Op for Name_Finalize.
	* exp_attr.adb (Expand_N_Attribute_Reference) <Finalization_Size>:
	Return 0 if the prefix type has relaxed finalization.
	* exp_ch3.adb (Build_Equivalent_Record_Aggregate): Return Empty if
	the type needs finalization.
	(Expand_Freeze_Record_Type): Call Find_Controlled_Prim_Op instead of
	Find_Prim_Op for Name_{Adjust,Initialize,Finalize}.
	Call Make_Finalize_Address_Body for all controlled types.
	* exp_ch4.adb (Insert_Dereference_Action): Do not generate a call to
	Adjust_Controlled_Dereference if the designated type has relaxed
	finalization.
	* exp_ch6.adb (Needs_BIP_Collection): Return false for an untagged
	type that has relaxed finalization.
	* exp_ch7.adb (Allows_Finalization_Collection): Return false if the
	designated type has relaxed finalization.
	(Check_Visibly_Controlled): Call Find_Controlled_Prim_Op instead of
	Find_Prim_Op.
	(Make_Adjust_Call): Likewise.
	(Make_Deep_Record_Body): Likewise.
	(Make_Final_Call): Likewise.
	(Make_Init_Call): Likewise.
	* exp_disp.adb (Set_All_DT_Position): Remove obsolete warning.
	* exp_util.ads: Add with and use clauses for Snames.
	(Find_Prim_Op): Add precondition.
	(Find_Controlled_Prim_Op): New function declaration.
	(Name_Of_Controlled_Prim_Op): Likewise.
	* exp_util.adb: Remove with and use clauses for Snames.
	(Build_Allocate_Deallocate_Proc): Do not build finalization actions
	if the designated type has relaxed finalization.
	(Find_Controlled_Prim_Op): New function.
	(Find_Last_Init): Call Find_Controlled_Prim_Op instead of
	Find_Prim_Op.
	(Name_Of_Controlled_Prim_Op): New function.
	* freeze.adb (Freeze_Entity.Freeze_Record_Type): Propagate the
	Has_Relaxed_Finalization flag from components.
	* gen_il-fields.ads (Opt_Field_Enum): Add Has_Relaxed_Finalization.
	* gen_il-gen-gen_entities.adb (Entity_Kind): Likewise.
	* sem_aux.adb (Is_By_Reference_Type): Return true for all controlled
	types.
	* sem_ch3.adb (Build_Derived_Record_Type): Do not special case types
	declared in Ada.Finalization.
	(Record_Type_Definition): Propagate the Has_Relaxed_Finalization
	flag from components.
	* sem_ch13.adb (Analyze_Aspects_At_Freeze_Point): Also process the
	Finalizable aspect.
	(Analyze_Aspect_Specifications): Likewise. Call Flag_Non_Static_Expr
	in more cases.
	(Check_Aspect_At_Freeze_Point): Likewise.
	(Inherit_Aspects_At_Freeze_Point): Likewise.
	(Resolve_Aspect_Expressions): Likewise.
	(Resolve_Finalizable_Argument): New procedure.
	(Validate_Finalizable_Aspect): Likewise.
	* sem_elab.ads: Add with and use clauses for Snames.
	(Is_Controlled_Procedure): New function declaration.
	* sem_elab.adb: Remove with and use clauses for Snames.
	(Is_Controlled_Proc): Move to...
	(Is_Controlled_Procedure): ...here and rename.
	(Check_A_Call): Call Find_Controlled_Prim_Op instead of
	Find_Prim_Op.
	(Is_Finalization_Procedure): Likewise.
	* sem_util.ads (Propagate_Controlled_Flags): Update documentation.
	* sem_util.adb (Is_Fully_Initialized_Type): Replace call to
	Find_Optional_Prim_Op with Find_Controlled_Prim_Op.
	Call Has_Null_Extension only for derived tagged types.
	(Propagate_Controlled_Flags): Propagate Has_Relaxed_Finalization.
	* snames.ads-tmpl (Name_Finalizable): New name.
	(Name_Relaxed_Finalization): Likewise.
	* libgnat/s-finroo.ads (Root_Controlled): Add Finalizable aspect.
	* doc/gnat_rm/gnat_language_extensions.rst: Document implementation
	of Generalized Finalization.
	* gnat_rm.texi: Regenerate.
	* gnat_ugn.texi: Regenerate.

1 files changed, 5 insertions, 4 deletions

diff --git a/gcc/ada/sem_util.ads b/gcc/ada/sem_util.ads
index 7363ad9..21e90dc 100644
--- a/gcc/ada/sem_util.ads
+++ b/gcc/ada/sem_util.ads
@@ -2920,10 +2920,11 @@ package Sem_Util is
       Comp     : Boolean := False;
       Deriv    : Boolean := False);
    --  Set Disable_Controlled, Finalize_Storage_Only, Has_Controlled_Component,
-   --  and Is_Controlled_Active on Typ when the flags are set on From_Typ. If
-   --  Comp is True, From_Typ is the type of a component of Typ while, if Deriv
-   --  is True, From_Typ is the parent type of Typ. This procedure can only set
-   --  flags for Typ, and never clear them.
+   --  Has_Relaxed_Finalization, and Is_Controlled_Active on Typ when the flags
+   --  are set on From_Typ. If Comp is True, From_Typ is assumed to be the type
+   --  of a component of Typ while, if Deriv is True, From_Typ is assumed to be
+   --  the parent type of Typ. This procedure can only set flags for Typ, and
+   --  never clear them.
 
    procedure Propagate_DIC_Attributes
      (Typ      : Entity_Id;