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) 1992-2013, 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; 30 31package Exp_Disp is 32 33 ------------------------------------- 34 -- Predefined primitive operations -- 35 ------------------------------------- 36 37 -- The predefined primitive operations (PPOs) are subprograms generated 38 -- by GNAT for a particular tagged type. Their role is to provide support 39 -- for different Ada language features such as the attribute 'Size or 40 -- handling of dispatching triggers in select statements. PPOs are created 41 -- when a tagged type is expanded or frozen. These subprograms are later 42 -- collected and inserted into the dispatch table of a tagged type at 43 -- fixed positions. Some of the PPOs that manipulate data in tagged objects 44 -- require the generation of thunks. 45 46 -- List of predefined primitive operations 47 48 -- Leading underscores designate reserved names. Bracketed numerical 49 -- values represent dispatch table slot numbers. 50 51 -- _Size (1) - implementation of the attribute 'Size for any tagged 52 -- type. Constructs of the form Prefix'Size are converted into 53 -- Prefix._Size. 54 55 -- TSS_Stream_Read (2) - implementation of the stream attribute Read 56 -- for any tagged type. 57 58 -- TSS_Stream_Write (3) - implementation of the stream attribute Write 59 -- for any tagged type. 60 61 -- TSS_Stream_Input (4) - implementation of the stream attribute Input 62 -- for any tagged type. 63 64 -- TSS_Stream_Output (5) - implementation of the stream attribute 65 -- Output for any tagged type. 66 67 -- Op_Eq (6) - implementation of the equality operator for any non- 68 -- limited tagged type. 69 70 -- _Assign (7) - implementation of the assignment operator for any 71 -- non-limited tagged type. 72 73 -- TSS_Deep_Adjust (8) - implementation of the finalization operation 74 -- Adjust for any non-limited tagged type. 75 76 -- TSS_Deep_Finalize (9) - implementation of the finalization 77 -- operation Finalize for any non-limited tagged type. 78 79 -- _Disp_Asynchronous_Select (10) - used in the expansion of ATC with 80 -- dispatching triggers. Null implementation for limited interfaces, 81 -- full body generation for types that implement limited interfaces, 82 -- not generated for the rest of the cases. See Expand_N_Asynchronous_ 83 -- Select in Exp_Ch9 for more information. 84 85 -- _Disp_Conditional_Select (11) - used in the expansion of conditional 86 -- selects with dispatching triggers. Null implementation for limited 87 -- interfaces, full body generation for types that implement limited 88 -- interfaces, not generated for the rest of the cases. See Expand_N_ 89 -- Conditional_Entry_Call in Exp_Ch9 for more information. 90 91 -- _Disp_Get_Prim_Op_Kind (12) - helper routine used in the expansion 92 -- of ATC with dispatching triggers. Null implementation for limited 93 -- interfaces, full body generation for types that implement limited 94 -- interfaces, not generated for the rest of the cases. 95 96 -- _Disp_Get_Task_Id (13) - helper routine used in the expansion of 97 -- Abort, attributes 'Callable and 'Terminated for task interface 98 -- class-wide types. Full body generation for task types, null 99 -- implementation for limited interfaces, not generated for the rest 100 -- of the cases. See Expand_N_Attribute_Reference in Exp_Attr and 101 -- Expand_N_Abort_Statement in Exp_Ch9 for more information. 102 103 -- _Disp_Requeue (14) - used in the expansion of dispatching requeue 104 -- statements. Null implementation is provided for protected, task 105 -- and synchronized interfaces. Protected and task types implementing 106 -- concurrent interfaces receive full bodies. See Expand_N_Requeue_ 107 -- Statement in Exp_Ch9 for more information. 108 109 -- _Disp_Timed_Select (15) - used in the expansion of timed selects 110 -- with dispatching triggers. Null implementation for limited 111 -- interfaces, full body generation for types that implement limited 112 -- interfaces, not generated for the rest of the cases. See Expand_N_ 113 -- Timed_Entry_Call for more information. 114 115 -- Life cycle of predefined primitive operations 116 117 -- The specifications and bodies of the PPOs are created by 118 -- Make_Predefined_Primitive_Specs and Predefined_Primitive_Bodies 119 -- in Exp_Ch3. The generated specifications are immediately analyzed, 120 -- while the bodies are left as freeze actions to the tagged type for 121 -- which they are created. 122 123 -- PPOs are collected and added to the Primitive_Operations list of 124 -- a type by the regular analysis mechanism. 125 126 -- PPOs are frozen by Exp_Ch3.Predefined_Primitive_Freeze 127 128 -- Thunks for PPOs are created by Make_DT 129 130 -- Dispatch table positions of PPOs are set by Set_All_DT_Position 131 132 -- Calls to PPOs proceed as regular dispatching calls. If the PPO 133 -- has a thunk, a call proceeds as a regular dispatching call with 134 -- a thunk. 135 136 -- Guidelines for addition of new predefined primitive operations 137 138 -- Update the value of constant Max_Predef_Prims in a-tags.ads to 139 -- indicate the new number of PPOs. 140 141 -- Introduce a new predefined name for the new PPO in Snames.ads and 142 -- Snames.adb. 143 144 -- Categorize the new PPO name as predefined by adding an entry in 145 -- Is_Predefined_Dispatching_Operation in Exp_Disp. 146 147 -- Generate the specification of the new PPO in Make_Predefined_ 148 -- Primitive_Spec in Exp_Ch3.adb. The Is_Internal flag of the defining 149 -- identifier of the specification must be set to True. 150 151 -- Generate the body of the new PPO in Predefined_Primitive_Bodies in 152 -- Exp_Ch3.adb. The Is_Internal flag of the defining identifier of the 153 -- specification must be set to True. 154 155 -- If the new PPO requires a thunk, add an entry in Freeze_Subprogram 156 -- in Exp_Ch6.adb. 157 158 -- When generating calls to a PPO, use Find_Prim_Op from Exp_Util.ads 159 -- to retrieve the entity of the operation directly. 160 161 -- Number of predefined primitive operations added by the Expander 162 -- for a tagged type. If more predefined primitive operations are 163 -- added, the following items must be changed: 164 165 -- Ada.Tags.Max_Predef_Prims - indirect use 166 -- Exp_Disp.Default_Prim_Op_Position - indirect use 167 -- Exp_Disp.Set_All_DT_Position - direct use 168 169 procedure Apply_Tag_Checks (Call_Node : Node_Id); 170 -- Generate checks required on dispatching calls 171 172 function Building_Static_DT (Typ : Entity_Id) return Boolean; 173 pragma Inline (Building_Static_DT); 174 -- Returns true when building statically allocated dispatch tables 175 176 procedure Build_Static_Dispatch_Tables (N : Node_Id); 177 -- N is a library level package declaration or package body. Build the 178 -- static dispatch table of the tagged types defined at library level. In 179 -- case of package declarations with private part the generated nodes are 180 -- added at the end of the list of private declarations. Otherwise they are 181 -- added to the end of the list of public declarations. In case of package 182 -- bodies they are added to the end of the list of declarations of the 183 -- package body. 184 185 function Convert_Tag_To_Interface 186 (Typ : Entity_Id; Expr : Node_Id) return Node_Id; 187 pragma Inline (Convert_Tag_To_Interface); 188 -- This function is used in class-wide interface conversions; the expanded 189 -- code generated to convert a tagged object to a class-wide interface type 190 -- involves referencing the tag component containing the secondary dispatch 191 -- table associated with the interface. Given the expression Expr that 192 -- references a tag component, we cannot generate an unchecked conversion 193 -- to leave the expression decorated with the class-wide interface type Typ 194 -- because an unchecked conversion cannot be seen as a no-op. An unchecked 195 -- conversion is conceptually a function call and therefore the RM allows 196 -- the backend to obtain a copy of the value of the actual object and store 197 -- it in some other place (like a register); in such case the interface 198 -- conversion is not equivalent to a displacement of the pointer to the 199 -- interface and any further displacement fails. Although the functionality 200 -- of this function is simple and could be done directly, the purpose of 201 -- this routine is to leave well documented in the sources these 202 -- occurrences. 203 204 -- If Expr is an N_Selected_Component that references a tag generate: 205 -- type ityp is non null access Typ; 206 -- ityp!(Expr'Address).all 207 208 -- if Expr is an N_Function_Call to Ada.Tags.Displace then generate: 209 -- type ityp is non null access Typ; 210 -- ityp!(Expr).all 211 212 function CPP_Num_Prims (Typ : Entity_Id) return Nat; 213 -- Return the number of primitives of the C++ part of the dispatch table. 214 -- For types that are not derivations of CPP types return 0. 215 216 procedure Expand_Dispatching_Call (Call_Node : Node_Id); 217 -- Expand the call to the operation through the dispatch table and perform 218 -- the required tag checks when appropriate. For CPP types tag checks are 219 -- not relevant. 220 221 procedure Expand_Interface_Actuals (Call_Node : Node_Id); 222 -- Ada 2005 (AI-251): Displace all the actuals corresponding to class-wide 223 -- interfaces to reference the interface tag of the actual object 224 225 procedure Expand_Interface_Conversion (N : Node_Id); 226 -- Ada 2005 (AI-251): N is a type-conversion node. Displace the pointer 227 -- to the object to give access to the interface tag associated with the 228 -- dispatch table of the target type. 229 230 procedure Expand_Interface_Thunk 231 (Prim : Node_Id; 232 Thunk_Id : out Entity_Id; 233 Thunk_Code : out Node_Id); 234 -- Ada 2005 (AI-251): When a tagged type implements abstract interfaces we 235 -- generate additional subprograms (thunks) associated with each primitive 236 -- Prim to have a layout compatible with the C++ ABI. The thunk displaces 237 -- the pointers to the actuals that depend on the controlling type before 238 -- transferring control to the target subprogram. If there is no need to 239 -- generate the thunk then Thunk_Id and Thunk_Code are set to Empty. 240 -- Otherwise they are set to the defining identifier and the subprogram 241 -- body of the generated thunk. 242 243 function Has_CPP_Constructors (Typ : Entity_Id) return Boolean; 244 -- Returns true if the type has CPP constructors 245 246 function Is_Expanded_Dispatching_Call (N : Node_Id) return Boolean; 247 -- Returns true if N is the expanded code of a dispatching call 248 249 function Is_Predefined_Dispatching_Operation (E : Entity_Id) return Boolean; 250 -- Ada 2005 (AI-251): Determines if E is a predefined primitive operation 251 252 function Is_Predefined_Internal_Operation (E : Entity_Id) return Boolean; 253 -- Similar to the previous one, but excludes stream operations, because 254 -- these may be overridden, and need extra formals, like user-defined 255 -- operations. 256 257 function Is_Predefined_Interface_Primitive (E : Entity_Id) return Boolean; 258 -- Ada 2005 (AI-345): Returns True if E is one of the predefined primitives 259 -- required to implement interfaces. 260 261 function Make_DT (Typ : Entity_Id; N : Node_Id := Empty) return List_Id; 262 -- Expand the declarations for the Dispatch Table. The node N is the 263 -- declaration that forces the generation of the table. It is used to place 264 -- error messages when the declaration leads to the freezing of a given 265 -- primitive operation that has an incomplete non- tagged formal. 266 267 function Make_Disp_Asynchronous_Select_Body 268 (Typ : Entity_Id) return Node_Id; 269 -- Ada 2005 (AI-345): Generate the body of the primitive operation of type 270 -- Typ used for dispatching in asynchronous selects. Generate a null body 271 -- if Typ is an interface type. 272 273 function Make_Disp_Asynchronous_Select_Spec 274 (Typ : Entity_Id) return Node_Id; 275 -- Ada 2005 (AI-345): Generate the specification of the primitive operation 276 -- of type Typ used for dispatching in asynchronous selects. 277 278 function Make_Disp_Conditional_Select_Body 279 (Typ : Entity_Id) return Node_Id; 280 -- Ada 2005 (AI-345): Generate the body of the primitive operation of type 281 -- Typ used for dispatching in conditional selects. Generate a null body 282 -- if Typ is an interface type. 283 284 function Make_Disp_Conditional_Select_Spec 285 (Typ : Entity_Id) return Node_Id; 286 -- Ada 2005 (AI-345): Generate the specification of the primitive operation 287 -- of type Typ used for dispatching in conditional selects. 288 289 function Make_Disp_Get_Prim_Op_Kind_Body 290 (Typ : Entity_Id) return Node_Id; 291 -- Ada 2005 (AI-345): Generate the body of the primitive operation of type 292 -- Typ used for retrieving the callable entity kind during dispatching in 293 -- asynchronous selects. Generate a null body if Typ is an interface type. 294 295 function Make_Disp_Get_Prim_Op_Kind_Spec 296 (Typ : Entity_Id) return Node_Id; 297 -- Ada 2005 (AI-345): Generate the specification of the primitive operation 298 -- of the type Typ use for retrieving the callable entity kind during 299 -- dispatching in asynchronous selects. 300 301 function Make_Disp_Get_Task_Id_Body 302 (Typ : Entity_Id) return Node_Id; 303 -- Ada 2005 (AI-345): Generate body of the primitive operation of type Typ 304 -- used for retrieving the _task_id field of a task interface class- wide 305 -- type. Generate a null body if Typ is an interface or a non-task type. 306 307 function Make_Disp_Get_Task_Id_Spec 308 (Typ : Entity_Id) return Node_Id; 309 -- Ada 2005 (AI-345): Generate the specification of the primitive operation 310 -- of type Typ used for retrieving the _task_id field of a task interface 311 -- class-wide type. 312 313 function Make_Disp_Requeue_Body 314 (Typ : Entity_Id) return Node_Id; 315 -- Ada 2005 (AI05-0030): Generate the body of the primitive operation of 316 -- type Typ used for dispatching on requeue statements. Generate a body 317 -- containing a single null-statement if Typ is an interface type. 318 319 function Make_Disp_Requeue_Spec 320 (Typ : Entity_Id) return Node_Id; 321 -- Ada 2005 (AI05-0030): Generate the specification of the primitive 322 -- operation of type Typ used for dispatching requeue statements. 323 324 function Make_Disp_Timed_Select_Body 325 (Typ : Entity_Id) return Node_Id; 326 -- Ada 2005 (AI-345): Generate the body of the primitive operation of type 327 -- Typ used for dispatching in timed selects. Generate a body containing 328 -- a single null-statement if Typ is an interface type. 329 330 function Make_Disp_Timed_Select_Spec 331 (Typ : Entity_Id) return Node_Id; 332 -- Ada 2005 (AI-345): Generate the specification of the primitive operation 333 -- of type Typ used for dispatching in timed selects. 334 335 function Make_Select_Specific_Data_Table 336 (Typ : Entity_Id) return List_Id; 337 -- Ada 2005 (AI-345): Create and populate the auxiliary table in the TSD 338 -- of Typ used for dispatching in asynchronous, conditional and timed 339 -- selects. Generate code to set the primitive operation kinds and entry 340 -- indexes of primitive operations and primitive wrappers. 341 342 function Make_Tags (Typ : Entity_Id) return List_Id; 343 -- Generate the entities associated with the primary and secondary tags of 344 -- Typ and fill the contents of Access_Disp_Table. In case of library level 345 -- tagged types this routine imports the forward declaration of the tag 346 -- entity, that will be declared and exported by Make_DT. 347 348 function Make_VM_TSD (Typ : Entity_Id) return List_Id; 349 -- Build the Type Specific Data record associated with tagged type Typ. 350 -- Invoked only when generating code for VM targets. 351 352 function Register_Primitive 353 (Loc : Source_Ptr; 354 Prim : Entity_Id) return List_Id; 355 -- Build code to register Prim in the primary or secondary dispatch table. 356 -- If Prim is associated with a secondary dispatch table then generate also 357 -- its thunk and register it in the associated secondary dispatch table. 358 -- In general the dispatch tables are always generated by Make_DT and 359 -- Make_Secondary_DT; this routine is only used in two corner cases: 360 -- 361 -- 1) To construct the dispatch table of a tagged type whose parent 362 -- is a CPP_Class (see Build_Init_Procedure). 363 -- 2) To handle late overriding of dispatching operations (see 364 -- Check_Dispatching_Operation and Make_DT). 365 -- 366 -- The caller is responsible for inserting the generated code in the 367 -- proper place. 368 369 procedure Set_All_DT_Position (Typ : Entity_Id); 370 -- Set the DT_Position field for each primitive operation. In the CPP 371 -- Class case check that no pragma CPP_Virtual is missing and that the 372 -- DT_Position are coherent 373 374 procedure Set_CPP_Constructors (Typ : Entity_Id); 375 -- Typ is a CPP_Class type. Create the Init procedures of that type 376 -- required to handle its default and non-default constructors. The 377 -- functions to which pragma CPP_Constructor is applied in the sources 378 -- are functions returning this type, and having an implicit access to the 379 -- target object in its first argument; such implicit argument is explicit 380 -- in the IP procedures built here. 381 382 procedure Set_DTC_Entity_Value 383 (Tagged_Type : Entity_Id; 384 Prim : Entity_Id); 385 -- Set the definite value of the DTC_Entity value associated with a given 386 -- primitive of a tagged type. 387 388 procedure Write_DT (Typ : Entity_Id); 389 pragma Export (Ada, Write_DT); 390 -- Debugging procedure (to be called within gdb) 391 392end Exp_Disp; 393