1------------------------------------------------------------------------------ 2-- -- 3-- GNAT COMPILER COMPONENTS -- 4-- -- 5-- E X P _ D I S P -- 6-- -- 7-- S p e c -- 8-- -- 9-- Copyright (C) 1992-2020, Free Software Foundation, Inc. -- 10-- -- 11-- GNAT is free software; you can redistribute it and/or modify it under -- 12-- terms of the GNU General Public License as published by the Free Soft- -- 13-- ware Foundation; either version 3, or (at your option) any later ver- -- 14-- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- 15-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- 16-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- 17-- for more details. You should have received a copy of the GNU General -- 18-- Public License distributed with GNAT; see file COPYING3. If not, go to -- 19-- http://www.gnu.org/licenses for a complete copy of the license. -- 20-- -- 21-- GNAT was originally developed by the GNAT team at New York University. -- 22-- Extensive contributions were provided by Ada Core Technologies Inc. -- 23-- -- 24------------------------------------------------------------------------------ 25 26-- This package contains routines involved in tagged types and dynamic 27-- dispatching expansion. 28 29with Types; use Types; 30with Uintp; use Uintp; 31 32package Exp_Disp is 33 34 ------------------------------------- 35 -- Predefined primitive operations -- 36 ------------------------------------- 37 38 -- The predefined primitive operations (PPOs) are subprograms generated 39 -- by GNAT for a particular tagged type. Their role is to provide support 40 -- for different Ada language features such as the attribute 'Size or 41 -- handling of dispatching triggers in select statements. PPOs are created 42 -- when a tagged type is expanded or frozen. These subprograms are later 43 -- collected and inserted into the dispatch table of a tagged type at 44 -- fixed positions. Some of the PPOs that manipulate data in tagged objects 45 -- require the generation of thunks. 46 47 -- List of predefined primitive operations 48 49 -- Leading underscores designate reserved names. Bracketed numerical 50 -- values represent dispatch table slot numbers. 51 52 -- _Size (1) - implementation of the attribute 'Size for any tagged 53 -- type. Constructs of the form Prefix'Size are converted into 54 -- Prefix._Size. 55 56 -- TSS_Stream_Read (2) - implementation of the stream attribute Read 57 -- for any tagged type. 58 59 -- TSS_Stream_Write (3) - implementation of the stream attribute Write 60 -- for any tagged type. 61 62 -- TSS_Stream_Input (4) - implementation of the stream attribute Input 63 -- for any tagged type. 64 65 -- TSS_Stream_Output (5) - implementation of the stream attribute 66 -- Output for any tagged type. 67 68 -- Op_Eq (6) - implementation of the equality operator for any non- 69 -- limited tagged type. 70 71 -- _Assign (7) - implementation of the assignment operator for any 72 -- non-limited tagged type. 73 74 -- TSS_Deep_Adjust (8) - implementation of the finalization operation 75 -- Adjust for any non-limited tagged type. 76 77 -- TSS_Deep_Finalize (9) - implementation of the finalization 78 -- operation Finalize for any non-limited tagged type. 79 80 -- Put_Image (10) - implementation of Put_Image attribute for any 81 -- tagged type. 82 83 -- _Disp_Asynchronous_Select (11) - used in the expansion of ATC with 84 -- dispatching triggers. Null implementation for limited interfaces, 85 -- full body generation for types that implement limited interfaces, 86 -- not generated for the rest of the cases. See Expand_N_Asynchronous_ 87 -- Select in Exp_Ch9 for more information. 88 89 -- _Disp_Conditional_Select (12) - used in the expansion of conditional 90 -- selects with dispatching triggers. Null implementation for limited 91 -- interfaces, full body generation for types that implement limited 92 -- interfaces, not generated for the rest of the cases. See Expand_N_ 93 -- Conditional_Entry_Call in Exp_Ch9 for more information. 94 95 -- _Disp_Get_Prim_Op_Kind (13) - helper routine used in the expansion 96 -- of ATC with dispatching triggers. Null implementation for limited 97 -- interfaces, full body generation for types that implement limited 98 -- interfaces, not generated for the rest of the cases. 99 100 -- _Disp_Get_Task_Id (14) - helper routine used in the expansion of 101 -- Abort, attributes 'Callable and 'Terminated for task interface 102 -- class-wide types. Full body generation for task types, null 103 -- implementation for limited interfaces, not generated for the rest 104 -- of the cases. See Expand_N_Attribute_Reference in Exp_Attr and 105 -- Expand_N_Abort_Statement in Exp_Ch9 for more information. 106 107 -- _Disp_Requeue (15) - used in the expansion of dispatching requeue 108 -- statements. Null implementation is provided for protected, task 109 -- and synchronized interfaces. Protected and task types implementing 110 -- concurrent interfaces receive full bodies. See Expand_N_Requeue_ 111 -- Statement in Exp_Ch9 for more information. 112 113 -- _Disp_Timed_Select (16) - used in the expansion of timed selects 114 -- with dispatching triggers. Null implementation for limited 115 -- interfaces, full body generation for types that implement limited 116 -- interfaces, not generated for the rest of the cases. See Expand_N_ 117 -- Timed_Entry_Call for more information. 118 119 -- Life cycle of predefined primitive operations 120 121 -- The specifications and bodies of the PPOs are created by 122 -- Make_Predefined_Primitive_Specs and Predefined_Primitive_Bodies 123 -- in Exp_Ch3. The generated specifications are immediately analyzed, 124 -- while the bodies are left as freeze actions to the tagged type for 125 -- which they are created. 126 127 -- PPOs are collected and added to the Primitive_Operations list of 128 -- a type by the regular analysis mechanism. 129 130 -- PPOs are frozen by Exp_Ch3.Predefined_Primitive_Freeze 131 132 -- Thunks for PPOs are created by Make_DT 133 134 -- Dispatch table positions of PPOs are set by Set_All_DT_Position 135 136 -- Calls to PPOs proceed as regular dispatching calls. If the PPO 137 -- has a thunk, a call proceeds as a regular dispatching call with 138 -- a thunk. 139 140 -- Guidelines for addition of new predefined primitive operations 141 142 -- Update the value of constant Max_Predef_Prims in a-tags.ads to 143 -- indicate the new number of PPOs. 144 145 -- Update Exp_Disp.Default_Prim_Op_Position. 146 147 -- Introduce a new predefined name for the new PPO in Snames.ads and 148 -- Snames.adb. 149 150 -- Categorize the new PPO name as predefined by adding an entry in 151 -- Is_Predefined_Dispatching_Operation in Sem_Util and Exp_Cg. 152 153 -- Generate the specification of the new PPO in Make_Predefined_ 154 -- Primitive_Spec in Exp_Ch3.adb. The Is_Internal flag of the defining 155 -- identifier of the specification must be set to True. 156 157 -- Generate the body of the new PPO in Predefined_Primitive_Bodies in 158 -- Exp_Ch3.adb. The Is_Internal flag of the defining identifier of the 159 -- specification must be set to True. 160 161 -- If the new PPO requires a thunk, add an entry in Freeze_Subprogram 162 -- in Exp_Ch6.adb. 163 164 -- When generating calls to a PPO, use Find_Prim_Op from exp_util.ads 165 -- to retrieve the entity of the operation directly. 166 167 procedure Apply_Tag_Checks (Call_Node : Node_Id); 168 -- Generate checks required on dispatching calls 169 170 function Building_Static_DT (Typ : Entity_Id) return Boolean; 171 pragma Inline (Building_Static_DT); 172 -- Returns true when building statically allocated dispatch tables 173 174 function Building_Static_Secondary_DT (Typ : Entity_Id) return Boolean; 175 pragma Inline (Building_Static_Secondary_DT); 176 -- Returns true when building statically allocated secondary dispatch 177 -- tables 178 179 procedure Build_Static_Dispatch_Tables (N : Node_Id); 180 -- N is a library level package declaration or package body. Build the 181 -- static dispatch table of the tagged types defined at library level. In 182 -- case of package declarations with private part the generated nodes are 183 -- added at the end of the list of private declarations. Otherwise they are 184 -- added to the end of the list of public declarations. In case of package 185 -- bodies they are added to the end of the list of declarations of the 186 -- package body. 187 188 function Convert_Tag_To_Interface 189 (Typ : Entity_Id; Expr : Node_Id) return Node_Id; 190 pragma Inline (Convert_Tag_To_Interface); 191 -- This function is used in class-wide interface conversions; the expanded 192 -- code generated to convert a tagged object to a class-wide interface type 193 -- involves referencing the tag component containing the secondary dispatch 194 -- table associated with the interface. Given the expression Expr that 195 -- references a tag component, we cannot generate an unchecked conversion 196 -- to leave the expression decorated with the class-wide interface type Typ 197 -- because an unchecked conversion cannot be seen as a no-op. An unchecked 198 -- conversion is conceptually a function call and therefore the RM allows 199 -- the backend to obtain a copy of the value of the actual object and store 200 -- it in some other place (like a register); in such case the interface 201 -- conversion is not equivalent to a displacement of the pointer to the 202 -- interface and any further displacement fails. Although the functionality 203 -- of this function is simple and could be done directly, the purpose of 204 -- this routine is to leave well documented in the sources these 205 -- occurrences. 206 207 -- If Expr is an N_Selected_Component that references a tag generate: 208 -- type ityp is non null access Typ; 209 -- ityp!(Expr'Address).all 210 211 -- if Expr is an N_Function_Call to Ada.Tags.Displace then generate: 212 -- type ityp is non null access Typ; 213 -- ityp!(Expr).all 214 215 function CPP_Num_Prims (Typ : Entity_Id) return Nat; 216 -- Return the number of primitives of the C++ part of the dispatch table. 217 -- For types that are not derivations of CPP types return 0. 218 219 function Elab_Flag_Needed (Typ : Entity_Id) return Boolean; 220 -- Return True if the elaboration of the tagged type Typ is completed at 221 -- run time by the execution of code located in the IP routine and the 222 -- expander must generate an extra elaboration flag to avoid performing 223 -- such elaboration twice. 224 225 procedure Expand_Dispatching_Call (Call_Node : Node_Id); 226 -- Expand the call to the operation through the dispatch table and perform 227 -- the required tag checks when appropriate. For CPP types tag checks are 228 -- not relevant. 229 230 procedure Expand_Interface_Actuals (Call_Node : Node_Id); 231 -- Ada 2005 (AI-251): Displace all the actuals corresponding to class-wide 232 -- interfaces to reference the interface tag of the actual object 233 234 procedure Expand_Interface_Conversion (N : Node_Id); 235 -- Ada 2005 (AI-251): N is a type-conversion node. Displace the pointer 236 -- to the object to give access to the interface tag associated with the 237 -- dispatch table of the target type. 238 239 procedure Expand_Interface_Thunk 240 (Prim : Node_Id; 241 Thunk_Id : out Entity_Id; 242 Thunk_Code : out Node_Id; 243 Iface : Entity_Id); 244 -- Ada 2005 (AI-251): When a tagged type implements abstract interfaces we 245 -- generate additional subprograms (thunks) associated with each primitive 246 -- Prim to have a layout compatible with the C++ ABI. The thunk displaces 247 -- the pointers to the actuals that depend on the controlling type before 248 -- transferring control to the target subprogram. If there is no need to 249 -- generate the thunk then Thunk_Id and Thunk_Code are set to Empty. 250 -- Otherwise they are set to the defining identifier and the subprogram 251 -- body of the generated thunk. 252 253 function Has_CPP_Constructors (Typ : Entity_Id) return Boolean; 254 -- Returns true if the type has CPP constructors 255 256 function Is_Expanded_Dispatching_Call (N : Node_Id) return Boolean; 257 -- Returns true if N is the expanded code of a dispatching call 258 259 function Make_DT (Typ : Entity_Id; N : Node_Id := Empty) return List_Id; 260 -- Expand the declarations for the Dispatch Table. The node N is the 261 -- declaration that forces the generation of the table. It is used to place 262 -- error messages when the declaration leads to the freezing of a given 263 -- primitive operation that has an incomplete non- tagged formal. 264 265 function Make_Disp_Asynchronous_Select_Body 266 (Typ : Entity_Id) return Node_Id; 267 -- Ada 2005 (AI-345): Generate the body of the primitive operation of type 268 -- Typ used for dispatching in asynchronous selects. Generate a null body 269 -- if Typ is an interface type. 270 271 function Make_Disp_Asynchronous_Select_Spec 272 (Typ : Entity_Id) return Node_Id; 273 -- Ada 2005 (AI-345): Generate the specification of the primitive operation 274 -- of type Typ used for dispatching in asynchronous selects. 275 276 function Make_Disp_Conditional_Select_Body 277 (Typ : Entity_Id) return Node_Id; 278 -- Ada 2005 (AI-345): Generate the body of the primitive operation of type 279 -- Typ used for dispatching in conditional selects. Generate a null body 280 -- if Typ is an interface type. 281 282 function Make_Disp_Conditional_Select_Spec 283 (Typ : Entity_Id) return Node_Id; 284 -- Ada 2005 (AI-345): Generate the specification of the primitive operation 285 -- of type Typ used for dispatching in conditional selects. 286 287 function Make_Disp_Get_Prim_Op_Kind_Body 288 (Typ : Entity_Id) return Node_Id; 289 -- Ada 2005 (AI-345): Generate the body of the primitive operation of type 290 -- Typ used for retrieving the callable entity kind during dispatching in 291 -- asynchronous selects. Generate a null body if Typ is an interface type. 292 293 function Make_Disp_Get_Prim_Op_Kind_Spec 294 (Typ : Entity_Id) return Node_Id; 295 -- Ada 2005 (AI-345): Generate the specification of the primitive operation 296 -- of the type Typ use for retrieving the callable entity kind during 297 -- dispatching in asynchronous selects. 298 299 function Make_Disp_Get_Task_Id_Body 300 (Typ : Entity_Id) return Node_Id; 301 -- Ada 2005 (AI-345): Generate body of the primitive operation of type Typ 302 -- used for retrieving the _task_id field of a task interface class- wide 303 -- type. Generate a null body if Typ is an interface or a non-task type. 304 305 function Make_Disp_Get_Task_Id_Spec 306 (Typ : Entity_Id) return Node_Id; 307 -- Ada 2005 (AI-345): Generate the specification of the primitive operation 308 -- of type Typ used for retrieving the _task_id field of a task interface 309 -- class-wide type. 310 311 function Make_Disp_Requeue_Body 312 (Typ : Entity_Id) return Node_Id; 313 -- Ada 2005 (AI05-0030): Generate the body of the primitive operation of 314 -- type Typ used for dispatching on requeue statements. Generate a body 315 -- containing a single null-statement if Typ is an interface type. 316 317 function Make_Disp_Requeue_Spec 318 (Typ : Entity_Id) return Node_Id; 319 -- Ada 2005 (AI05-0030): Generate the specification of the primitive 320 -- operation of type Typ used for dispatching requeue statements. 321 322 function Make_Disp_Timed_Select_Body 323 (Typ : Entity_Id) return Node_Id; 324 -- Ada 2005 (AI-345): Generate the body of the primitive operation of type 325 -- Typ used for dispatching in timed selects. Generate a body containing 326 -- a single null-statement if Typ is an interface type. 327 328 function Make_Disp_Timed_Select_Spec 329 (Typ : Entity_Id) return Node_Id; 330 -- Ada 2005 (AI-345): Generate the specification of the primitive operation 331 -- of type Typ used for dispatching in timed selects. 332 333 function Make_Select_Specific_Data_Table 334 (Typ : Entity_Id) return List_Id; 335 -- Ada 2005 (AI-345): Create and populate the auxiliary table in the TSD 336 -- of Typ used for dispatching in asynchronous, conditional and timed 337 -- selects. Generate code to set the primitive operation kinds and entry 338 -- indexes of primitive operations and primitive wrappers. 339 340 function Make_Tags (Typ : Entity_Id) return List_Id; 341 -- Generate the entities associated with the primary and secondary tags of 342 -- Typ and fill the contents of Access_Disp_Table. In case of library level 343 -- tagged types this routine imports the forward declaration of the tag 344 -- entity, that will be declared and exported by Make_DT. 345 346 function Register_Primitive 347 (Loc : Source_Ptr; 348 Prim : Entity_Id) return List_Id; 349 -- Build code to register Prim in the primary or secondary dispatch table. 350 -- If Prim is associated with a secondary dispatch table then generate also 351 -- its thunk and register it in the associated secondary dispatch table. 352 -- In general the dispatch tables are always generated by Make_DT and 353 -- Make_Secondary_DT; this routine is only used in two corner cases: 354 -- 355 -- 1) To construct the dispatch table of a tagged type whose parent 356 -- is a CPP_Class (see Build_Init_Procedure). 357 -- 2) To handle late overriding of dispatching operations (see 358 -- Check_Dispatching_Operation and Make_DT). 359 -- 360 -- The caller is responsible for inserting the generated code in the 361 -- proper place. 362 363 procedure Set_All_DT_Position (Typ : Entity_Id); 364 -- Set the DT_Position field for each primitive operation. In the CPP 365 -- Class case check that no pragma CPP_Virtual is missing and that the 366 -- DT_Position are coherent 367 368 procedure Set_CPP_Constructors (Typ : Entity_Id); 369 -- Typ is a CPP_Class type. Create the Init procedures of that type 370 -- required to handle its default and non-default constructors. The 371 -- functions to which pragma CPP_Constructor is applied in the sources 372 -- are functions returning this type, and having an implicit access to the 373 -- target object in its first argument; such implicit argument is explicit 374 -- in the IP procedures built here. 375 376 procedure Set_DT_Position_Value (Prim : Entity_Id; Value : Uint); 377 -- Set the position of a dispatching primitive its dispatch table. For 378 -- subprogram wrappers propagate the value to the wrapped subprogram. 379 380 procedure Set_DTC_Entity_Value (Tagged_Type : Entity_Id; Prim : Entity_Id); 381 -- Set the definite value of the DTC_Entity value associated with a given 382 -- primitive of a tagged type. For subprogram wrappers, propagate the value 383 -- to the wrapped subprogram. 384 385 procedure Write_DT (Typ : Entity_Id); 386 pragma Export (Ada, Write_DT); 387 -- Debugging procedure (to be called within gdb) 388 389end Exp_Disp; 390