393 lines
20 KiB
Ada
393 lines
20 KiB
Ada
------------------------------------------------------------------------------
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-- --
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-- GNAT COMPILER COMPONENTS --
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-- --
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-- E X P _ D I S P --
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-- --
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-- GS p e c --
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-- --
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-- Copyright (C) 1992-2015, Free Software Foundation, Inc. --
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-- --
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-- GNAT is free software; you can redistribute it and/or modify it under --
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-- terms of the GNU General Public License as published by the Free Soft- --
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-- ware Foundation; either version 3, or (at your option) any later ver- --
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-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
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-- for more details. You should have received a copy of the GNU General --
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-- Public License distributed with GNAT; see file COPYING3. If not, go to --
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-- http://www.gnu.org/licenses for a complete copy of the license. --
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-- --
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-- GNAT was originally developed by the GNAT team at New York University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc. --
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-- --
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------------------------------------------------------------------------------
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-- This package contains routines involved in tagged types and dynamic
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-- dispatching expansion.
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with Types; use Types;
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with Uintp; use Uintp;
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package Exp_Disp is
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-------------------------------------
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-- Predefined primitive operations --
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-------------------------------------
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-- The predefined primitive operations (PPOs) are subprograms generated
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-- by GNAT for a particular tagged type. Their role is to provide support
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-- for different Ada language features such as the attribute 'Size or
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-- handling of dispatching triggers in select statements. PPOs are created
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-- when a tagged type is expanded or frozen. These subprograms are later
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-- collected and inserted into the dispatch table of a tagged type at
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-- fixed positions. Some of the PPOs that manipulate data in tagged objects
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-- require the generation of thunks.
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-- List of predefined primitive operations
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-- Leading underscores designate reserved names. Bracketed numerical
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-- values represent dispatch table slot numbers.
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-- _Size (1) - implementation of the attribute 'Size for any tagged
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-- type. Constructs of the form Prefix'Size are converted into
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-- Prefix._Size.
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-- TSS_Stream_Read (2) - implementation of the stream attribute Read
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-- for any tagged type.
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-- TSS_Stream_Write (3) - implementation of the stream attribute Write
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-- for any tagged type.
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-- TSS_Stream_Input (4) - implementation of the stream attribute Input
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-- for any tagged type.
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-- TSS_Stream_Output (5) - implementation of the stream attribute
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-- Output for any tagged type.
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-- Op_Eq (6) - implementation of the equality operator for any non-
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-- limited tagged type.
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-- _Assign (7) - implementation of the assignment operator for any
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-- non-limited tagged type.
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-- TSS_Deep_Adjust (8) - implementation of the finalization operation
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-- Adjust for any non-limited tagged type.
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-- TSS_Deep_Finalize (9) - implementation of the finalization
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-- operation Finalize for any non-limited tagged type.
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-- _Disp_Asynchronous_Select (10) - used in the expansion of ATC with
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-- dispatching triggers. Null implementation for limited interfaces,
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-- full body generation for types that implement limited interfaces,
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-- not generated for the rest of the cases. See Expand_N_Asynchronous_
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-- Select in Exp_Ch9 for more information.
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-- _Disp_Conditional_Select (11) - used in the expansion of conditional
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-- selects with dispatching triggers. Null implementation for limited
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-- interfaces, full body generation for types that implement limited
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-- interfaces, not generated for the rest of the cases. See Expand_N_
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-- Conditional_Entry_Call in Exp_Ch9 for more information.
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-- _Disp_Get_Prim_Op_Kind (12) - helper routine used in the expansion
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-- of ATC with dispatching triggers. Null implementation for limited
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-- interfaces, full body generation for types that implement limited
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-- interfaces, not generated for the rest of the cases.
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-- _Disp_Get_Task_Id (13) - helper routine used in the expansion of
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-- Abort, attributes 'Callable and 'Terminated for task interface
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-- class-wide types. Full body generation for task types, null
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-- implementation for limited interfaces, not generated for the rest
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-- of the cases. See Expand_N_Attribute_Reference in Exp_Attr and
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-- Expand_N_Abort_Statement in Exp_Ch9 for more information.
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-- _Disp_Requeue (14) - used in the expansion of dispatching requeue
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-- statements. Null implementation is provided for protected, task
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-- and synchronized interfaces. Protected and task types implementing
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-- concurrent interfaces receive full bodies. See Expand_N_Requeue_
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-- Statement in Exp_Ch9 for more information.
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-- _Disp_Timed_Select (15) - used in the expansion of timed selects
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-- with dispatching triggers. Null implementation for limited
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-- interfaces, full body generation for types that implement limited
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-- interfaces, not generated for the rest of the cases. See Expand_N_
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-- Timed_Entry_Call for more information.
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-- Life cycle of predefined primitive operations
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-- The specifications and bodies of the PPOs are created by
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-- Make_Predefined_Primitive_Specs and Predefined_Primitive_Bodies
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-- in Exp_Ch3. The generated specifications are immediately analyzed,
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-- while the bodies are left as freeze actions to the tagged type for
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-- which they are created.
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-- PPOs are collected and added to the Primitive_Operations list of
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-- a type by the regular analysis mechanism.
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-- PPOs are frozen by Exp_Ch3.Predefined_Primitive_Freeze
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-- Thunks for PPOs are created by Make_DT
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-- Dispatch table positions of PPOs are set by Set_All_DT_Position
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-- Calls to PPOs proceed as regular dispatching calls. If the PPO
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-- has a thunk, a call proceeds as a regular dispatching call with
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-- a thunk.
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-- Guidelines for addition of new predefined primitive operations
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-- Update the value of constant Max_Predef_Prims in a-tags.ads to
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-- indicate the new number of PPOs.
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-- Introduce a new predefined name for the new PPO in Snames.ads and
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-- Snames.adb.
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-- Categorize the new PPO name as predefined by adding an entry in
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-- Is_Predefined_Dispatching_Operation in Exp_Disp.
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-- Generate the specification of the new PPO in Make_Predefined_
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-- Primitive_Spec in Exp_Ch3.adb. The Is_Internal flag of the defining
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-- identifier of the specification must be set to True.
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-- Generate the body of the new PPO in Predefined_Primitive_Bodies in
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-- Exp_Ch3.adb. The Is_Internal flag of the defining identifier of the
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-- specification must be set to True.
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-- If the new PPO requires a thunk, add an entry in Freeze_Subprogram
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-- in Exp_Ch6.adb.
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-- When generating calls to a PPO, use Find_Prim_Op from Exp_Util.ads
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-- to retrieve the entity of the operation directly.
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-- Number of predefined primitive operations added by the Expander
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-- for a tagged type. If more predefined primitive operations are
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-- added, the following items must be changed:
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-- Ada.Tags.Max_Predef_Prims - indirect use
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-- Exp_Disp.Default_Prim_Op_Position - indirect use
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-- Exp_Disp.Set_All_DT_Position - direct use
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procedure Apply_Tag_Checks (Call_Node : Node_Id);
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-- Generate checks required on dispatching calls
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function Building_Static_DT (Typ : Entity_Id) return Boolean;
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pragma Inline (Building_Static_DT);
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-- Returns true when building statically allocated dispatch tables
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procedure Build_Static_Dispatch_Tables (N : Node_Id);
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-- N is a library level package declaration or package body. Build the
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-- static dispatch table of the tagged types defined at library level. In
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-- case of package declarations with private part the generated nodes are
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-- added at the end of the list of private declarations. Otherwise they are
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-- added to the end of the list of public declarations. In case of package
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-- bodies they are added to the end of the list of declarations of the
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-- package body.
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function Convert_Tag_To_Interface
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(Typ : Entity_Id; Expr : Node_Id) return Node_Id;
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pragma Inline (Convert_Tag_To_Interface);
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-- This function is used in class-wide interface conversions; the expanded
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-- code generated to convert a tagged object to a class-wide interface type
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-- involves referencing the tag component containing the secondary dispatch
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-- table associated with the interface. Given the expression Expr that
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-- references a tag component, we cannot generate an unchecked conversion
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-- to leave the expression decorated with the class-wide interface type Typ
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-- because an unchecked conversion cannot be seen as a no-op. An unchecked
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-- conversion is conceptually a function call and therefore the RM allows
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-- the backend to obtain a copy of the value of the actual object and store
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-- it in some other place (like a register); in such case the interface
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-- conversion is not equivalent to a displacement of the pointer to the
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-- interface and any further displacement fails. Although the functionality
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-- of this function is simple and could be done directly, the purpose of
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-- this routine is to leave well documented in the sources these
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-- occurrences.
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-- If Expr is an N_Selected_Component that references a tag generate:
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-- type ityp is non null access Typ;
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-- ityp!(Expr'Address).all
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-- if Expr is an N_Function_Call to Ada.Tags.Displace then generate:
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-- type ityp is non null access Typ;
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-- ityp!(Expr).all
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function CPP_Num_Prims (Typ : Entity_Id) return Nat;
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-- Return the number of primitives of the C++ part of the dispatch table.
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-- For types that are not derivations of CPP types return 0.
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procedure Expand_Dispatching_Call (Call_Node : Node_Id);
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-- Expand the call to the operation through the dispatch table and perform
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-- the required tag checks when appropriate. For CPP types tag checks are
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-- not relevant.
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procedure Expand_Interface_Actuals (Call_Node : Node_Id);
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-- Ada 2005 (AI-251): Displace all the actuals corresponding to class-wide
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-- interfaces to reference the interface tag of the actual object
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procedure Expand_Interface_Conversion (N : Node_Id);
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-- Ada 2005 (AI-251): N is a type-conversion node. Displace the pointer
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-- to the object to give access to the interface tag associated with the
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-- dispatch table of the target type.
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procedure Expand_Interface_Thunk
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(Prim : Node_Id;
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Thunk_Id : out Entity_Id;
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Thunk_Code : out Node_Id);
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-- Ada 2005 (AI-251): When a tagged type implements abstract interfaces we
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-- generate additional subprograms (thunks) associated with each primitive
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-- Prim to have a layout compatible with the C++ ABI. The thunk displaces
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-- the pointers to the actuals that depend on the controlling type before
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-- transferring control to the target subprogram. If there is no need to
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-- generate the thunk then Thunk_Id and Thunk_Code are set to Empty.
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-- Otherwise they are set to the defining identifier and the subprogram
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-- body of the generated thunk.
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function Has_CPP_Constructors (Typ : Entity_Id) return Boolean;
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-- Returns true if the type has CPP constructors
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function Is_Expanded_Dispatching_Call (N : Node_Id) return Boolean;
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-- Returns true if N is the expanded code of a dispatching call
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function Is_Predefined_Dispatching_Operation (E : Entity_Id) return Boolean;
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-- Ada 2005 (AI-251): Determines if E is a predefined primitive operation
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function Is_Predefined_Internal_Operation (E : Entity_Id) return Boolean;
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-- Similar to the previous one, but excludes stream operations, because
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-- these may be overridden, and need extra formals, like user-defined
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-- operations.
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function Is_Predefined_Interface_Primitive (E : Entity_Id) return Boolean;
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-- Ada 2005 (AI-345): Returns True if E is one of the predefined primitives
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-- required to implement interfaces.
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function Make_DT (Typ : Entity_Id; N : Node_Id := Empty) return List_Id;
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-- Expand the declarations for the Dispatch Table. The node N is the
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-- declaration that forces the generation of the table. It is used to place
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-- error messages when the declaration leads to the freezing of a given
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-- primitive operation that has an incomplete non- tagged formal.
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function Make_Disp_Asynchronous_Select_Body
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(Typ : Entity_Id) return Node_Id;
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-- Ada 2005 (AI-345): Generate the body of the primitive operation of type
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-- Typ used for dispatching in asynchronous selects. Generate a null body
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-- if Typ is an interface type.
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function Make_Disp_Asynchronous_Select_Spec
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(Typ : Entity_Id) return Node_Id;
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-- Ada 2005 (AI-345): Generate the specification of the primitive operation
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-- of type Typ used for dispatching in asynchronous selects.
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function Make_Disp_Conditional_Select_Body
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(Typ : Entity_Id) return Node_Id;
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-- Ada 2005 (AI-345): Generate the body of the primitive operation of type
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-- Typ used for dispatching in conditional selects. Generate a null body
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-- if Typ is an interface type.
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function Make_Disp_Conditional_Select_Spec
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(Typ : Entity_Id) return Node_Id;
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-- Ada 2005 (AI-345): Generate the specification of the primitive operation
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-- of type Typ used for dispatching in conditional selects.
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function Make_Disp_Get_Prim_Op_Kind_Body
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(Typ : Entity_Id) return Node_Id;
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-- Ada 2005 (AI-345): Generate the body of the primitive operation of type
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-- Typ used for retrieving the callable entity kind during dispatching in
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-- asynchronous selects. Generate a null body if Typ is an interface type.
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function Make_Disp_Get_Prim_Op_Kind_Spec
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(Typ : Entity_Id) return Node_Id;
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-- Ada 2005 (AI-345): Generate the specification of the primitive operation
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-- of the type Typ use for retrieving the callable entity kind during
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-- dispatching in asynchronous selects.
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function Make_Disp_Get_Task_Id_Body
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(Typ : Entity_Id) return Node_Id;
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-- Ada 2005 (AI-345): Generate body of the primitive operation of type Typ
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-- used for retrieving the _task_id field of a task interface class- wide
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-- type. Generate a null body if Typ is an interface or a non-task type.
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function Make_Disp_Get_Task_Id_Spec
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(Typ : Entity_Id) return Node_Id;
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-- Ada 2005 (AI-345): Generate the specification of the primitive operation
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-- of type Typ used for retrieving the _task_id field of a task interface
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-- class-wide type.
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function Make_Disp_Requeue_Body
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(Typ : Entity_Id) return Node_Id;
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-- Ada 2005 (AI05-0030): Generate the body of the primitive operation of
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-- type Typ used for dispatching on requeue statements. Generate a body
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-- containing a single null-statement if Typ is an interface type.
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function Make_Disp_Requeue_Spec
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(Typ : Entity_Id) return Node_Id;
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-- Ada 2005 (AI05-0030): Generate the specification of the primitive
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-- operation of type Typ used for dispatching requeue statements.
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function Make_Disp_Timed_Select_Body
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(Typ : Entity_Id) return Node_Id;
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-- Ada 2005 (AI-345): Generate the body of the primitive operation of type
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-- Typ used for dispatching in timed selects. Generate a body containing
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-- a single null-statement if Typ is an interface type.
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function Make_Disp_Timed_Select_Spec
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(Typ : Entity_Id) return Node_Id;
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-- Ada 2005 (AI-345): Generate the specification of the primitive operation
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-- of type Typ used for dispatching in timed selects.
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function Make_Select_Specific_Data_Table
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(Typ : Entity_Id) return List_Id;
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-- Ada 2005 (AI-345): Create and populate the auxiliary table in the TSD
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-- of Typ used for dispatching in asynchronous, conditional and timed
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-- selects. Generate code to set the primitive operation kinds and entry
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-- indexes of primitive operations and primitive wrappers.
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function Make_Tags (Typ : Entity_Id) return List_Id;
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-- Generate the entities associated with the primary and secondary tags of
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-- Typ and fill the contents of Access_Disp_Table. In case of library level
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-- tagged types this routine imports the forward declaration of the tag
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-- entity, that will be declared and exported by Make_DT.
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function Register_Primitive
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(Loc : Source_Ptr;
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Prim : Entity_Id) return List_Id;
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-- Build code to register Prim in the primary or secondary dispatch table.
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-- If Prim is associated with a secondary dispatch table then generate also
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-- its thunk and register it in the associated secondary dispatch table.
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-- In general the dispatch tables are always generated by Make_DT and
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-- Make_Secondary_DT; this routine is only used in two corner cases:
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--
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-- 1) To construct the dispatch table of a tagged type whose parent
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-- is a CPP_Class (see Build_Init_Procedure).
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-- 2) To handle late overriding of dispatching operations (see
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-- Check_Dispatching_Operation and Make_DT).
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--
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-- The caller is responsible for inserting the generated code in the
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-- proper place.
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procedure Set_All_DT_Position (Typ : Entity_Id);
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-- Set the DT_Position field for each primitive operation. In the CPP
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-- Class case check that no pragma CPP_Virtual is missing and that the
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-- DT_Position are coherent
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procedure Set_CPP_Constructors (Typ : Entity_Id);
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-- Typ is a CPP_Class type. Create the Init procedures of that type
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-- required to handle its default and non-default constructors. The
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-- functions to which pragma CPP_Constructor is applied in the sources
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-- are functions returning this type, and having an implicit access to the
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-- target object in its first argument; such implicit argument is explicit
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-- in the IP procedures built here.
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procedure Set_DT_Position_Value (Prim : Entity_Id; Value : Uint);
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-- Set the position of a dispatching primitive its dispatch table. For
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-- subprogram wrappers propagate the value to the wrapped subprogram.
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procedure Set_DTC_Entity_Value (Tagged_Type : Entity_Id; Prim : Entity_Id);
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-- Set the definite value of the DTC_Entity value associated with a given
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-- primitive of a tagged type. For subprogram wrappers, propagate the value
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-- to the wrapped subprogram.
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procedure Write_DT (Typ : Entity_Id);
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pragma Export (Ada, Write_DT);
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-- Debugging procedure (to be called within gdb)
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end Exp_Disp;
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