1------------------------------------------------------------------------------ 2-- -- 3-- GNAT COMPILER COMPONENTS -- 4-- -- 5-- E X P _ U T I L -- 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-- Package containing utility procedures used throughout the expander 27 28with Exp_Tss; use Exp_Tss; 29with Namet; use Namet; 30with Rtsfind; use Rtsfind; 31with Sinfo; use Sinfo; 32with Types; use Types; 33with Uintp; use Uintp; 34 35package Exp_Util is 36 37 ----------------------------------------------- 38 -- Handling of Actions Associated with Nodes -- 39 ----------------------------------------------- 40 41 -- The evaluation of certain expression nodes involves the elaboration 42 -- of associated types and other declarations, and the execution of 43 -- statement sequences. Expansion routines generating such actions must 44 -- find an appropriate place in the tree to hang the actions so that 45 -- they will be evaluated at the appropriate point. 46 47 -- Some cases are simple: 48 49 -- For an expression occurring in a simple statement that is in a list 50 -- of statements, the actions are simply inserted into the list before 51 -- the associated statement. 52 53 -- For an expression occurring in a declaration (declarations always 54 -- appear in lists), the actions are similarly inserted into the list 55 -- just before the associated declaration. 56 57 -- The following special cases arise: 58 59 -- For actions associated with the right operand of a short circuit 60 -- form, the actions are first stored in the short circuit form node 61 -- in the Actions field. The expansion of these forms subsequently 62 -- expands the short circuit forms into if statements which can then 63 -- be moved as described above. 64 65 -- For actions appearing in the Condition expression of a while loop, 66 -- or an elsif clause, the actions are similarly temporarily stored in 67 -- in the node (N_Elsif_Part or N_Iteration_Scheme) associated with 68 -- the expression using the Condition_Actions field. Subsequently, the 69 -- expansion of these nodes rewrites the control structures involved to 70 -- reposition the actions in normal statement sequence. 71 72 -- For actions appearing in the then or else expression of a conditional 73 -- expression, these actions are similarly placed in the node, using the 74 -- Then_Actions or Else_Actions field as appropriate. Once again the 75 -- expansion of the N_If_Expression node rewrites the node so that the 76 -- actions can be positioned normally. 77 78 -- For actions coming from expansion of the expression in an expression 79 -- with actions node, the action is appended to the list of actions. 80 81 -- Basically what we do is to climb up to the tree looking for the 82 -- proper insertion point, as described by one of the above cases, 83 -- and then insert the appropriate action or actions. 84 85 -- Note if more than one insert call is made specifying the same 86 -- Assoc_Node, then the actions are elaborated in the order of the 87 -- calls, and this guarantee is preserved for the special cases above. 88 89 procedure Insert_Action 90 (Assoc_Node : Node_Id; 91 Ins_Action : Node_Id); 92 -- Insert the action Ins_Action at the appropriate point as described 93 -- above. The action is analyzed using the default checks after it is 94 -- inserted. Assoc_Node is the node with which the action is associated. 95 96 procedure Insert_Action 97 (Assoc_Node : Node_Id; 98 Ins_Action : Node_Id; 99 Suppress : Check_Id); 100 -- Insert the action Ins_Action at the appropriate point as described 101 -- above. The action is analyzed using the default checks as modified 102 -- by the given Suppress argument after it is inserted. Assoc_Node is 103 -- the node with which the action is associated. 104 105 procedure Insert_Actions 106 (Assoc_Node : Node_Id; 107 Ins_Actions : List_Id); 108 -- Insert the list of action Ins_Actions at the appropriate point as 109 -- described above. The actions are analyzed using the default checks 110 -- after they are inserted. Assoc_Node is the node with which the actions 111 -- are associated. Ins_Actions may be No_List, in which case the call has 112 -- no effect. 113 114 procedure Insert_Actions 115 (Assoc_Node : Node_Id; 116 Ins_Actions : List_Id; 117 Suppress : Check_Id); 118 -- Insert the list of action Ins_Actions at the appropriate point as 119 -- described above. The actions are analyzed using the default checks 120 -- as modified by the given Suppress argument after they are inserted. 121 -- Assoc_Node is the node with which the actions are associated. 122 -- Ins_Actions may be No_List, in which case the call has no effect. 123 124 procedure Insert_Action_After 125 (Assoc_Node : Node_Id; 126 Ins_Action : Node_Id); 127 -- Assoc_Node must be a node in a list. Same as Insert_Action but the 128 -- action will be inserted after N in a manner that is compatible with 129 -- the transient scope mechanism. 130 131 procedure Insert_Actions_After 132 (Assoc_Node : Node_Id; 133 Ins_Actions : List_Id); 134 -- Assoc_Node must be a node in a list. Same as Insert_Actions but 135 -- actions will be inserted after N in a manner that is compatible with 136 -- the transient scope mechanism. This procedure must be used instead 137 -- of Insert_List_After if Assoc_Node may be in a transient scope. 138 -- 139 -- Implementation limitation: Assoc_Node must be a statement. We can 140 -- generalize to expressions if there is a need but this is tricky to 141 -- implement because of short-circuits (among other things).??? 142 143 procedure Insert_Declaration (N : Node_Id; Decl : Node_Id); 144 -- N must be a subexpression (Nkind in N_Subexpr). This is similar to 145 -- Insert_Action (N, Decl), but inserts Decl outside the expression in 146 -- which N appears. This is called Insert_Declaration because the intended 147 -- use is for declarations that have no associated code. We can't go 148 -- moving other kinds of things out of the current expression, since they 149 -- could be executed conditionally (e.g. right operand of short circuit, 150 -- or THEN/ELSE of if expression). This is currently used only in 151 -- Modify_Tree_For_C mode, where it is needed because in C we have no 152 -- way of having declarations within an expression (a really annoying 153 -- limitation). 154 155 procedure Insert_Library_Level_Action (N : Node_Id); 156 -- This procedure inserts and analyzes the node N as an action at the 157 -- library level for the current unit (i.e. it is attached to the 158 -- Actions field of the N_Compilation_Aux node for the main unit). 159 160 procedure Insert_Library_Level_Actions (L : List_Id); 161 -- Similar, but inserts a list of actions 162 163 ----------------------- 164 -- Other Subprograms -- 165 ----------------------- 166 167 procedure Activate_Atomic_Synchronization (N : Node_Id); 168 -- N is a node for which atomic synchronization may be required (it is 169 -- either an identifier, expanded name, or selected/indexed component or 170 -- an explicit dereference). The caller has checked the basic conditions 171 -- (atomic variable appearing and Atomic_Sync not disabled). This function 172 -- checks if atomic synchronization is required and if so sets the flag 173 -- and if appropriate generates a warning (in -gnatw.n mode). 174 175 procedure Adjust_Condition (N : Node_Id); 176 -- The node N is an expression whose root-type is Boolean, and which 177 -- represents a boolean value used as a condition (i.e. a True/False 178 -- value). This routine handles the case of C and Fortran convention 179 -- boolean types, which have zero/non-zero semantics rather than the normal 180 -- 0/1 semantics, and also the case of an enumeration rep clause that 181 -- specifies a non-standard representation. On return, node N always has 182 -- the type Standard.Boolean, with a value that is a standard Boolean 183 -- values of 0/1 for False/True. This procedure is used in two situations. 184 -- First, the processing for a condition field always calls 185 -- Adjust_Condition, so that the boolean value presented to the backend is 186 -- a standard value. Second, for the code for boolean operations such as 187 -- AND, Adjust_Condition is called on both operands, and then the operation 188 -- is done in the domain of Standard_Boolean, then Adjust_Result_Type is 189 -- called on the result to possibly reset the original type. This procedure 190 -- also takes care of validity checking if Validity_Checks = Tests. 191 192 procedure Adjust_Result_Type (N : Node_Id; T : Entity_Id); 193 -- The processing of boolean operations like AND uses the procedure 194 -- Adjust_Condition so that it can operate on Standard.Boolean, which is 195 -- the only boolean type on which the backend needs to be able to implement 196 -- such operators. This means that the result is also of type 197 -- Standard.Boolean. In general the type must be reset back to the original 198 -- type to get proper semantics, and that is the purpose of this procedure. 199 -- N is the node (of type Standard.Boolean), and T is the desired type. As 200 -- an optimization, this procedure leaves the type as Standard.Boolean in 201 -- contexts where this is permissible (in particular for Condition fields, 202 -- and for operands of other logical operations higher up the tree). The 203 -- call to this procedure is completely ignored if the argument N is not of 204 -- type Boolean. 205 206 procedure Append_Freeze_Action (T : Entity_Id; N : Node_Id); 207 -- Add a new freeze action for the given type. The freeze action is 208 -- attached to the freeze node for the type. Actions will be elaborated in 209 -- the order in which they are added. Note that the added node is not 210 -- analyzed. The analyze call is found in Exp_Ch13.Expand_N_Freeze_Entity. 211 212 procedure Append_Freeze_Actions (T : Entity_Id; L : List_Id); 213 -- Adds the given list of freeze actions (declarations or statements) for 214 -- the given type. The freeze actions are attached to the freeze node for 215 -- the type. Actions will be elaborated in the order in which they are 216 -- added, and the actions within the list will be elaborated in list order. 217 -- Note that the added nodes are not analyzed. The analyze call is found in 218 -- Exp_Ch13.Expand_N_Freeze_Entity. 219 220 procedure Build_Allocate_Deallocate_Proc 221 (N : Node_Id; 222 Is_Allocate : Boolean); 223 -- Create a custom Allocate/Deallocate to be associated with an allocation 224 -- or deallocation: 225 -- 226 -- 1) controlled objects 227 -- 2) class-wide objects 228 -- 3) any kind of object on a subpool 229 -- 230 -- N must be an allocator or the declaration of a temporary variable which 231 -- represents the expression of the original allocator node, otherwise N 232 -- must be a free statement. If flag Is_Allocate is set, the generated 233 -- routine is allocate, deallocate otherwise. 234 235 function Build_Runtime_Call (Loc : Source_Ptr; RE : RE_Id) return Node_Id; 236 -- Build an N_Procedure_Call_Statement calling the given runtime entity. 237 -- The call has no parameters. The first argument provides the location 238 -- information for the tree and for error messages. The call node is not 239 -- analyzed on return, the caller is responsible for analyzing it. 240 241 function Build_Task_Image_Decls 242 (Loc : Source_Ptr; 243 Id_Ref : Node_Id; 244 A_Type : Entity_Id; 245 In_Init_Proc : Boolean := False) return List_Id; 246 -- Build declaration for a variable that holds an identifying string to be 247 -- used as a task name. Id_Ref is an identifier if the task is a variable, 248 -- and a selected or indexed component if the task is component of an 249 -- object. If it is an indexed component, A_Type is the corresponding array 250 -- type. Its index types are used to build the string as an image of the 251 -- index values. For composite types, the result includes two declarations: 252 -- one for a generated function that computes the image without using 253 -- concatenation, and one for the variable that holds the result. 254 -- 255 -- If In_Init_Proc is true, the call is part of the initialization of 256 -- a component of a composite type, and the enclosing initialization 257 -- procedure must be flagged as using the secondary stack. If In_Init_Proc 258 -- is false, the call is for a stand-alone object, and the generated 259 -- function itself must do its own cleanups. 260 261 function Component_May_Be_Bit_Aligned (Comp : Entity_Id) return Boolean; 262 -- This function is in charge of detecting record components that may 263 -- cause trouble in the back end if an attempt is made to assign the 264 -- component. The back end can handle such assignments with no problem if 265 -- the components involved are small (64-bits or less) records or scalar 266 -- items (including bit-packed arrays represented with modular types) or 267 -- are both aligned on a byte boundary (starting on a byte boundary, and 268 -- occupying an integral number of bytes). 269 -- 270 -- However, problems arise for records larger than 64 bits, or for arrays 271 -- (other than bit-packed arrays represented with a modular type) if the 272 -- component starts on a non-byte boundary, or does not occupy an integral 273 -- number of bytes (i.e. there are some bits possibly shared with fields 274 -- at the start or beginning of the component). The back end cannot handle 275 -- loading and storing such components in a single operation. 276 -- 277 -- This function is used to detect the troublesome situation. it is 278 -- conservative in the sense that it produces True unless it knows for 279 -- sure that the component is safe (as outlined in the first paragraph 280 -- above). The code generation for record and array assignment checks for 281 -- trouble using this function, and if so the assignment is generated 282 -- component-wise, which the back end is required to handle correctly. 283 -- 284 -- Note that in GNAT 3, the back end will reject such components anyway, 285 -- so the hard work in checking for this case is wasted in GNAT 3, but 286 -- it is harmless, so it is easier to do it in all cases, rather than 287 -- conditionalize it in GNAT 5 or beyond. 288 289 procedure Convert_To_Actual_Subtype (Exp : Node_Id); 290 -- The Etype of an expression is the nominal type of the expression, 291 -- not the actual subtype. Often these are the same, but not always. 292 -- For example, a reference to a formal of unconstrained type has the 293 -- unconstrained type as its Etype, but the actual subtype is obtained by 294 -- applying the actual bounds. This routine is given an expression, Exp, 295 -- and (if necessary), replaces it using Rewrite, with a conversion to 296 -- the actual subtype, building the actual subtype if necessary. If the 297 -- expression is already of the requested type, then it is unchanged. 298 299 function Corresponding_Runtime_Package (Typ : Entity_Id) return RTU_Id; 300 -- Return the id of the runtime package that will provide support for 301 -- concurrent type Typ. Currently only protected types are supported, 302 -- and the returned value is one of the following: 303 -- System_Tasking_Protected_Objects 304 -- System_Tasking_Protected_Objects_Entries 305 -- System_Tasking_Protected_Objects_Single_Entry 306 307 function Current_Sem_Unit_Declarations return List_Id; 308 -- Return the place where it is fine to insert declarations for the 309 -- current semantic unit. If the unit is a package body, return the 310 -- visible declarations of the corresponding spec. For RCI stubs, this 311 -- is necessary because the point at which they are generated may not 312 -- be the earliest point at which they are used. 313 314 function Duplicate_Subexpr 315 (Exp : Node_Id; 316 Name_Req : Boolean := False) return Node_Id; 317 -- Given the node for a subexpression, this function makes a logical copy 318 -- of the subexpression, and returns it. This is intended for use when the 319 -- expansion of an expression needs to repeat part of it. For example, 320 -- replacing a**2 by a*a requires two references to a which may be a 321 -- complex subexpression. Duplicate_Subexpr guarantees not to duplicate 322 -- side effects. If necessary, it generates actions to save the expression 323 -- value in a temporary, inserting these actions into the tree using 324 -- Insert_Actions with Exp as the insertion location. The original 325 -- expression and the returned result then become references to this saved 326 -- value. Exp must be analyzed on entry. On return, Exp is analyzed, but 327 -- the caller is responsible for analyzing the returned copy after it is 328 -- attached to the tree. The Name_Req flag is set to ensure that the result 329 -- is suitable for use in a context requiring name (e.g. the prefix of an 330 -- attribute reference). 331 -- 332 -- Note that if there are any run time checks in Exp, these same checks 333 -- will be duplicated in the returned duplicated expression. The two 334 -- following functions allow this behavior to be modified. 335 336 function Duplicate_Subexpr_No_Checks 337 (Exp : Node_Id; 338 Name_Req : Boolean := False) return Node_Id; 339 -- Identical in effect to Duplicate_Subexpr, except that Remove_Checks 340 -- is called on the result, so that the duplicated expression does not 341 -- include checks. This is appropriate for use when Exp, the original 342 -- expression is unconditionally elaborated before the duplicated 343 -- expression, so that there is no need to repeat any checks. 344 345 function Duplicate_Subexpr_Move_Checks 346 (Exp : Node_Id; 347 Name_Req : Boolean := False) return Node_Id; 348 -- Identical in effect to Duplicate_Subexpr, except that Remove_Checks is 349 -- called on Exp after the duplication is complete, so that the original 350 -- expression does not include checks. In this case the result returned 351 -- (the duplicated expression) will retain the original checks. This is 352 -- appropriate for use when the duplicated expression is sure to be 353 -- elaborated before the original expression Exp, so that there is no need 354 -- to repeat the checks. 355 356 procedure Ensure_Defined (Typ : Entity_Id; N : Node_Id); 357 -- This procedure ensures that type referenced by Typ is defined. For the 358 -- case of a type other than an Itype, nothing needs to be done, since 359 -- all such types have declaration nodes. For Itypes, an N_Itype_Reference 360 -- node is generated and inserted as an action on node N. This is typically 361 -- used to ensure that an Itype is properly defined outside a conditional 362 -- construct when it is referenced in more than one branch. 363 364 function Entry_Names_OK return Boolean; 365 -- Determine whether it is appropriate to dynamically allocate strings 366 -- which represent entry [family member] names. These strings are created 367 -- by the compiler and used by GDB. 368 369 procedure Evaluate_Name (Nam : Node_Id); 370 -- Remove all side effects from a name which appears as part of an object 371 -- renaming declaration. More comments are needed here that explain how 372 -- this differs from Force_Evaluation and Remove_Side_Effects ??? 373 374 procedure Evolve_And_Then (Cond : in out Node_Id; Cond1 : Node_Id); 375 -- Rewrites Cond with the expression: Cond and then Cond1. If Cond is 376 -- Empty, then simply returns Cond1 (this allows the use of Empty to 377 -- initialize a series of checks evolved by this routine, with a final 378 -- result of Empty indicating that no checks were required). The Sloc field 379 -- of the constructed N_And_Then node is copied from Cond1. 380 381 procedure Evolve_Or_Else (Cond : in out Node_Id; Cond1 : Node_Id); 382 -- Rewrites Cond with the expression: Cond or else Cond1. If Cond is Empty, 383 -- then simply returns Cond1 (this allows the use of Empty to initialize a 384 -- series of checks evolved by this routine, with a final result of Empty 385 -- indicating that no checks were required). The Sloc field of the 386 -- constructed N_Or_Else node is copied from Cond1. 387 388 procedure Expand_Static_Predicates_In_Choices (N : Node_Id); 389 -- N is either a case alternative or a variant. The Discrete_Choices field 390 -- of N points to a list of choices. If any of these choices is the name 391 -- of a (statically) predicated subtype, then it is rewritten as the series 392 -- of choices that correspond to the values allowed for the subtype. 393 394 procedure Expand_Subtype_From_Expr 395 (N : Node_Id; 396 Unc_Type : Entity_Id; 397 Subtype_Indic : Node_Id; 398 Exp : Node_Id); 399 -- Build a constrained subtype from the initial value in object 400 -- declarations and/or allocations when the type is indefinite (including 401 -- class-wide). 402 403 function Find_Interface_ADT 404 (T : Entity_Id; 405 Iface : Entity_Id) return Elmt_Id; 406 -- Ada 2005 (AI-251): Given a type T implementing the interface Iface, 407 -- return the element of Access_Disp_Table containing the tag of the 408 -- interface. 409 410 function Find_Interface_Tag 411 (T : Entity_Id; 412 Iface : Entity_Id) return Entity_Id; 413 -- Ada 2005 (AI-251): Given a type T implementing the interface Iface, 414 -- return the record component containing the tag of Iface. 415 416 function Find_Prim_Op (T : Entity_Id; Name : Name_Id) return Entity_Id; 417 -- Find the first primitive operation of type T whose name is 'Name'. 418 -- This function allows the use of a primitive operation which is not 419 -- directly visible. If T is a class wide type, then the reference is 420 -- to an operation of the corresponding root type. Raises Program_Error 421 -- exception if no primitive operation is found. This is normally an 422 -- internal error, but in some cases is an expected consequence of 423 -- illegalities elsewhere. 424 425 function Find_Prim_Op 426 (T : Entity_Id; 427 Name : TSS_Name_Type) return Entity_Id; 428 -- Find the first primitive operation of type T whose name has the form 429 -- indicated by the name parameter (i.e. is a type support subprogram 430 -- with the indicated suffix). This function allows use of a primitive 431 -- operation which is not directly visible. If T is a class wide type, 432 -- then the reference is to an operation of the corresponding root type. 433 -- Raises Program_Error exception if no primitive operation is found. 434 -- This is normally an internal error, but in some cases is an expected 435 -- consequence of illegalities elsewhere. 436 437 function Find_Protection_Object (Scop : Entity_Id) return Entity_Id; 438 -- Traverse the scope stack starting from Scop and look for an entry, 439 -- entry family, or a subprogram that has a Protection_Object and return 440 -- it. Raises Program_Error if no such entity is found since the context 441 -- in which this routine is invoked should always have a protection 442 -- object. 443 444 function Find_Protection_Type (Conc_Typ : Entity_Id) return Entity_Id; 445 -- Given a protected type or its corresponding record, find the type of 446 -- field _object. 447 448 procedure Force_Evaluation 449 (Exp : Node_Id; 450 Name_Req : Boolean := False); 451 -- Force the evaluation of the expression right away. Similar behavior 452 -- to Remove_Side_Effects when Variable_Ref is set to TRUE. That is to 453 -- say, it removes the side-effects and captures the values of the 454 -- variables. Remove_Side_Effects guarantees that multiple evaluations 455 -- of the same expression won't generate multiple side effects, whereas 456 -- Force_Evaluation further guarantees that all evaluations will yield 457 -- the same result. 458 459 function Fully_Qualified_Name_String 460 (E : Entity_Id; 461 Append_NUL : Boolean := True) return String_Id; 462 -- Generates the string literal corresponding to the fully qualified name 463 -- of entity E, in all upper case, with an ASCII.NUL appended at the end 464 -- of the name if Append_NUL is True. 465 466 procedure Generate_Poll_Call (N : Node_Id); 467 -- If polling is active, then a call to the Poll routine is built, 468 -- and then inserted before the given node N and analyzed. 469 470 procedure Get_Current_Value_Condition 471 (Var : Node_Id; 472 Op : out Node_Kind; 473 Val : out Node_Id); 474 -- This routine processes the Current_Value field of the variable Var. If 475 -- the Current_Value field is null or if it represents a known value, then 476 -- on return Cond is set to N_Empty, and Val is set to Empty. 477 -- 478 -- The other case is when Current_Value points to an N_If_Statement or an 479 -- N_Elsif_Part or a N_Iteration_Scheme node (see description in Einfo for 480 -- exact details). In this case, Get_Current_Condition digs out the 481 -- condition, and then checks if the condition is known false, known true, 482 -- or not known at all. In the first two cases, Get_Current_Condition will 483 -- return with Op set to the appropriate conditional operator (inverted if 484 -- the condition is known false), and Val set to the constant value. If the 485 -- condition is not known, then Op and Val are set for the empty case 486 -- (N_Empty and Empty). 487 -- 488 -- The check for whether the condition is true/false unknown depends 489 -- on the case: 490 -- 491 -- For an IF, the condition is known true in the THEN part, known false 492 -- in any ELSIF or ELSE part, and not known outside the IF statement in 493 -- question. 494 -- 495 -- For an ELSIF, the condition is known true in the ELSIF part, known 496 -- FALSE in any subsequent ELSIF, or ELSE part, and not known before the 497 -- ELSIF, or after the end of the IF statement. 498 -- 499 -- The caller can use this result to determine the value (for the case of 500 -- N_Op_Eq), or to determine the result of some other test in other cases 501 -- (e.g. no access check required if N_Op_Ne Null). 502 503 function Get_Stream_Size (E : Entity_Id) return Uint; 504 -- Return the stream size value of the subtype E 505 506 function Has_Access_Constraint (E : Entity_Id) return Boolean; 507 -- Given object or type E, determine if a discriminant is of an access type 508 509 function Has_Following_Address_Clause (D : Node_Id) return Boolean; 510 -- D is the node for an object declaration. This function searches the 511 -- current declarative part to look for an address clause for the object 512 -- being declared, and returns True if one is found. 513 514 function Homonym_Number (Subp : Entity_Id) return Nat; 515 -- Here subp is the entity for a subprogram. This routine returns the 516 -- homonym number used to disambiguate overloaded subprograms in the same 517 -- scope (the number is used as part of constructed names to make sure that 518 -- they are unique). The number is the ordinal position on the Homonym 519 -- chain, counting only entries in the current scope. If an entity is not 520 -- overloaded, the returned number will be one. 521 522 function Inside_Init_Proc return Boolean; 523 -- Returns True if current scope is within an init proc 524 525 function In_Library_Level_Package_Body (Id : Entity_Id) return Boolean; 526 -- Given an arbitrary entity, determine whether it appears at the library 527 -- level of a package body. 528 529 function In_Unconditional_Context (Node : Node_Id) return Boolean; 530 -- Node is the node for a statement or a component of a statement. This 531 -- function determines if the statement appears in a context that is 532 -- unconditionally executed, i.e. it is not within a loop or a conditional 533 -- or a case statement etc. 534 535 function Is_All_Null_Statements (L : List_Id) return Boolean; 536 -- Return True if all the items of the list are N_Null_Statement nodes. 537 -- False otherwise. True for an empty list. It is an error to call this 538 -- routine with No_List as the argument. 539 540 function Is_Displacement_Of_Object_Or_Function_Result 541 (Obj_Id : Entity_Id) return Boolean; 542 -- Determine whether Obj_Id is a source entity that has been initialized by 543 -- either a controlled function call or the assignment of another source 544 -- object. In both cases the initialization expression is rewritten as a 545 -- class-wide conversion of Ada.Tags.Displace. 546 547 function Is_Finalizable_Transient 548 (Decl : Node_Id; 549 Rel_Node : Node_Id) return Boolean; 550 -- Determine whether declaration Decl denotes a controlled transient which 551 -- should be finalized. Rel_Node is the related context. Even though some 552 -- transient are controlled, they may act as renamings of other objects or 553 -- function calls. 554 555 function Is_Fully_Repped_Tagged_Type (T : Entity_Id) return Boolean; 556 -- Tests given type T, and returns True if T is a non-discriminated tagged 557 -- type which has a record representation clause that specifies the layout 558 -- of all the components, including recursively components in all parent 559 -- types. We exclude discriminated types for convenience, it is extremely 560 -- unlikely that the special processing associated with the use of this 561 -- routine is useful for the case of a discriminated type, and testing for 562 -- component overlap would be a pain. 563 564 function Is_Library_Level_Tagged_Type (Typ : Entity_Id) return Boolean; 565 -- Return True if Typ is a library level tagged type. Currently we use 566 -- this information to build statically allocated dispatch tables. 567 568 function Is_Non_BIP_Func_Call (Expr : Node_Id) return Boolean; 569 -- Determine whether node Expr denotes a non build-in-place function call 570 571 function Is_Possibly_Unaligned_Object (N : Node_Id) return Boolean; 572 -- Node N is an object reference. This function returns True if it is 573 -- possible that the object may not be aligned according to the normal 574 -- default alignment requirement for its type (e.g. if it appears in a 575 -- packed record, or as part of a component that has a component clause.) 576 577 function Is_Possibly_Unaligned_Slice (N : Node_Id) return Boolean; 578 -- Determine whether the node P is a slice of an array where the slice 579 -- result may cause alignment problems because it has an alignment that 580 -- is not compatible with the type. Return True if so. 581 582 function Is_Ref_To_Bit_Packed_Array (N : Node_Id) return Boolean; 583 -- Determine whether the node P is a reference to a bit packed array, i.e. 584 -- whether the designated object is a component of a bit packed array, or a 585 -- subcomponent of such a component. If so, then all subscripts in P are 586 -- evaluated with a call to Force_Evaluation, and True is returned. 587 -- Otherwise False is returned, and P is not affected. 588 589 function Is_Ref_To_Bit_Packed_Slice (N : Node_Id) return Boolean; 590 -- Determine whether the node P is a reference to a bit packed slice, i.e. 591 -- whether the designated object is bit packed slice or a component of a 592 -- bit packed slice. Return True if so. 593 594 function Is_Related_To_Func_Return (Id : Entity_Id) return Boolean; 595 -- Determine whether object Id is related to an expanded return statement. 596 -- The case concerned is "return Id.all;". 597 598 function Is_Renamed_Object (N : Node_Id) return Boolean; 599 -- Returns True if the node N is a renamed object. An expression is 600 -- considered to be a renamed object if either it is the Name of an object 601 -- renaming declaration, or is the prefix of a name which is a renamed 602 -- object. For example, in: 603 -- 604 -- x : r renames a (1 .. 2) (1); 605 -- 606 -- We consider that a (1 .. 2) is a renamed object since it is the prefix 607 -- of the name in the renaming declaration. 608 609 function Is_Secondary_Stack_BIP_Func_Call (Expr : Node_Id) return Boolean; 610 -- Determine whether Expr denotes a build-in-place function which returns 611 -- its result on the secondary stack. 612 613 function Is_Tag_To_Class_Wide_Conversion 614 (Obj_Id : Entity_Id) return Boolean; 615 -- Determine whether object Obj_Id is the result of a tag-to-class-wide 616 -- type conversion. 617 618 function Is_Untagged_Derivation (T : Entity_Id) return Boolean; 619 -- Returns true if type T is not tagged and is a derived type, 620 -- or is a private type whose completion is such a type. 621 622 function Is_Volatile_Reference (N : Node_Id) return Boolean; 623 -- Checks if the node N represents a volatile reference, which can be 624 -- either a direct reference to a variable treated as volatile, or an 625 -- indexed/selected component where the prefix is treated as volatile, 626 -- or has Volatile_Components set. A slice of a volatile variable is 627 -- also volatile. 628 629 function Is_VM_By_Copy_Actual (N : Node_Id) return Boolean; 630 -- Returns True if we are compiling on VM targets and N is a node that 631 -- requires pass-by-copy in these targets. 632 633 procedure Kill_Dead_Code (N : Node_Id; Warn : Boolean := False); 634 -- N represents a node for a section of code that is known to be dead. Any 635 -- exception handler references and warning messages relating to this code 636 -- are removed. If Warn is True, a warning will be output at the start of N 637 -- indicating the deletion of the code. Note that the tree for the deleted 638 -- code is left intact so that e.g. cross-reference data is still valid. 639 640 procedure Kill_Dead_Code (L : List_Id; Warn : Boolean := False); 641 -- Like the above procedure, but applies to every element in the given 642 -- list. If Warn is True, a warning will be output at the start of N 643 -- indicating the deletion of the code. 644 645 function Known_Non_Negative (Opnd : Node_Id) return Boolean; 646 -- Given a node for a subexpression, determines if it represents a value 647 -- that cannot possibly be negative, and if so returns True. A value of 648 -- False means that it is not known if the value is positive or negative. 649 650 function Known_Non_Null (N : Node_Id) return Boolean; 651 -- Given a node N for a subexpression of an access type, determines if 652 -- this subexpression yields a value that is known at compile time to 653 -- be non-null and returns True if so. Returns False otherwise. It is 654 -- an error to call this function if N is not of an access type. 655 656 function Known_Null (N : Node_Id) return Boolean; 657 -- Given a node N for a subexpression of an access type, determines if this 658 -- subexpression yields a value that is known at compile time to be null 659 -- and returns True if so. Returns False otherwise. It is an error to call 660 -- this function if N is not of an access type. 661 662 function Make_Invariant_Call (Expr : Node_Id) return Node_Id; 663 -- Expr is an object of a type which Has_Invariants set (and which thus 664 -- also has an Invariant_Procedure set). If invariants are enabled, this 665 -- function returns a call to the Invariant procedure passing Expr as the 666 -- argument, and returns it unanalyzed. If invariants are not enabled, 667 -- returns a null statement. 668 669 function Make_Predicate_Call 670 (Typ : Entity_Id; 671 Expr : Node_Id; 672 Mem : Boolean := False) return Node_Id; 673 -- Typ is a type with Predicate_Function set. This routine builds a call to 674 -- this function passing Expr as the argument, and returns it unanalyzed. 675 -- If Mem is set True, this is the special call for the membership case, 676 -- and the function called is the Predicate_Function_M if present. 677 678 function Make_Predicate_Check 679 (Typ : Entity_Id; 680 Expr : Node_Id) return Node_Id; 681 -- Typ is a type with Predicate_Function set. This routine builds a Check 682 -- pragma whose first argument is Predicate, and the second argument is 683 -- a call to the predicate function of Typ with Expr as the argument. If 684 -- Predicate_Check is suppressed then a null statement is returned instead. 685 686 function Make_Subtype_From_Expr 687 (E : Node_Id; 688 Unc_Typ : Entity_Id) return Node_Id; 689 -- Returns a subtype indication corresponding to the actual type of an 690 -- expression E. Unc_Typ is an unconstrained array or record, or 691 -- a classwide type. 692 693 function Matching_Standard_Type (Typ : Entity_Id) return Entity_Id; 694 -- Given a scalar subtype Typ, returns a matching type in standard that 695 -- has the same object size value. For example, a 16 bit signed type will 696 -- typically return Standard_Short_Integer. For fixed-point types, this 697 -- will return integer types of the corresponding size. 698 699 function May_Generate_Large_Temp (Typ : Entity_Id) return Boolean; 700 -- Determines if the given type, Typ, may require a large temporary of the 701 -- kind that causes back-end trouble if stack checking is enabled. The 702 -- result is True only the size of the type is known at compile time and 703 -- large, where large is defined heuristically by the body of this routine. 704 -- The purpose of this routine is to help avoid generating troublesome 705 -- temporaries that interfere with stack checking mechanism. Note that the 706 -- caller has to check whether stack checking is actually enabled in order 707 -- to guide the expansion (typically of a function call). 708 709 function Needs_Constant_Address 710 (Decl : Node_Id; 711 Typ : Entity_Id) return Boolean; 712 -- Check whether the expression in an address clause is restricted to 713 -- consist of constants, when the object has a non-trivial initialization 714 -- or is controlled. 715 716 function Needs_Finalization (T : Entity_Id) return Boolean; 717 -- True if type T is controlled, or has controlled subcomponents. Also 718 -- True if T is a class-wide type, because some type extension might add 719 -- controlled subcomponents, except that if pragma Restrictions 720 -- (No_Finalization) applies, this is False for class-wide types. 721 722 function Non_Limited_Designated_Type (T : Entity_Id) return Entity_Id; 723 -- An anonymous access type may designate a limited view. Check whether 724 -- non-limited view is available during expansion, to examine components 725 -- or other characteristics of the full type. 726 727 function OK_To_Do_Constant_Replacement (E : Entity_Id) return Boolean; 728 -- This function is used when testing whether or not to replace a reference 729 -- to entity E by a known constant value. Such replacement must be done 730 -- only in a scope known to be safe for such replacements. In particular, 731 -- if we are within a subprogram and the entity E is declared outside the 732 -- subprogram then we cannot do the replacement, since we do not attempt to 733 -- trace subprogram call flow. It is also unsafe to replace statically 734 -- allocated values (since they can be modified outside the scope), and we 735 -- also inhibit replacement of Volatile or aliased objects since their 736 -- address might be captured in a way we do not detect. A value of True is 737 -- returned only if the replacement is safe. 738 739 function Possible_Bit_Aligned_Component (N : Node_Id) return Boolean; 740 -- This function is used during processing the assignment of a record or 741 -- indexed component. The argument N is either the left hand or right hand 742 -- side of an assignment, and this function determines if there is a record 743 -- component reference where the record may be bit aligned in a manner that 744 -- causes trouble for the back end (see Component_May_Be_Bit_Aligned for 745 -- further details). 746 747 function Power_Of_Two (N : Node_Id) return Nat; 748 -- Determines if N is a known at compile time value which is of the form 749 -- 2**K, where K is in the range 1 .. M, where the Esize of N is 2**(M+1). 750 -- If so, returns the value K, otherwise returns zero. The caller checks 751 -- that N is of an integer type. 752 753 procedure Process_Statements_For_Controlled_Objects (N : Node_Id); 754 -- N is a node which contains a non-handled statement list. Inspect the 755 -- statements looking for declarations of controlled objects. If at least 756 -- one such object is found, wrap the statement list in a block. 757 758 function Remove_Init_Call 759 (Var : Entity_Id; 760 Rep_Clause : Node_Id) return Node_Id; 761 -- Look for init_proc call or aggregate initialization statements for 762 -- variable Var, either among declarations between that of Var and a 763 -- subsequent Rep_Clause applying to Var, or in the list of freeze actions 764 -- associated with Var, and if found, remove and return that call node. 765 766 procedure Remove_Side_Effects 767 (Exp : Node_Id; 768 Name_Req : Boolean := False; 769 Variable_Ref : Boolean := False); 770 -- Given the node for a subexpression, this function replaces the node if 771 -- necessary by an equivalent subexpression that is guaranteed to be side 772 -- effect free. This is done by extracting any actions that could cause 773 -- side effects, and inserting them using Insert_Actions into the tree 774 -- to which Exp is attached. Exp must be analyzed and resolved before the 775 -- call and is analyzed and resolved on return. Name_Req may only be set to 776 -- True if Exp has the form of a name, and the effect is to guarantee that 777 -- any replacement maintains the form of name. If Variable_Ref is set to 778 -- TRUE, a variable is considered as side effect (used in implementing 779 -- Force_Evaluation). Note: after call to Remove_Side_Effects, it is 780 -- safe to call New_Copy_Tree to obtain a copy of the resulting expression. 781 782 function Represented_As_Scalar (T : Entity_Id) return Boolean; 783 -- Returns True iff the implementation of this type in code generation 784 -- terms is scalar. This is true for scalars in the Ada sense, and for 785 -- packed arrays which are represented by a scalar (modular) type. 786 787 function Requires_Cleanup_Actions 788 (N : Node_Id; 789 Lib_Level : Boolean) return Boolean; 790 -- Given a node N, determine whether its declarative and/or statement list 791 -- contains one of the following: 792 -- 793 -- 1) controlled objects 794 -- 2) library-level tagged types 795 -- 796 -- These cases require special actions on scope exit. The flag Lib_Level 797 -- is set True if the construct is at library level, and False otherwise. 798 799 function Safe_Unchecked_Type_Conversion (Exp : Node_Id) return Boolean; 800 -- Given the node for an N_Unchecked_Type_Conversion, return True if this 801 -- is an unchecked conversion that Gigi can handle directly. Otherwise 802 -- return False if it is one for which the front end must provide a 803 -- temporary. Note that the node need not be analyzed, and thus the Etype 804 -- field may not be set, but in that case it must be the case that the 805 -- Subtype_Mark field of the node is set/analyzed. 806 807 procedure Set_Current_Value_Condition (Cnode : Node_Id); 808 -- Cnode is N_If_Statement, N_Elsif_Part, or N_Iteration_Scheme (the latter 809 -- when a WHILE condition is present). This call checks whether Condition 810 -- (Cnode) has embedded expressions of a form that should result in setting 811 -- the Current_Value field of one or more entities, and if so sets these 812 -- fields to point to Cnode. 813 814 procedure Set_Elaboration_Flag (N : Node_Id; Spec_Id : Entity_Id); 815 -- N is the node for a subprogram or generic body, and Spec_Id is the 816 -- entity for the corresponding spec. If an elaboration entity is defined, 817 -- then this procedure generates an assignment statement to set it True, 818 -- immediately after the body is elaborated. However, no assignment is 819 -- generated in the case of library level procedures, since the setting of 820 -- the flag in this case is generated in the binder. We do that so that we 821 -- can detect cases where this is the only elaboration action that is 822 -- required. 823 824 procedure Set_Renamed_Subprogram (N : Node_Id; E : Entity_Id); 825 -- N is an node which is an entity name that represents the name of a 826 -- renamed subprogram. The node is rewritten to be an identifier that 827 -- refers directly to the renamed subprogram, given by entity E. 828 829 function Side_Effect_Free 830 (N : Node_Id; 831 Name_Req : Boolean := False; 832 Variable_Ref : Boolean := False) return Boolean; 833 -- Determines if the tree N represents an expression that is known not 834 -- to have side effects. If this function returns True, then for example 835 -- a call to Remove_Side_Effects has no effect. 836 -- 837 -- Name_Req controls the handling of volatile variable references. If 838 -- Name_Req is False (the normal case), then volatile references are 839 -- considered to be side effects. If Name_Req is True, then volatility 840 -- of variables is ignored. 841 -- 842 -- If Variable_Ref is True, then all variable references are considered to 843 -- be side effects (regardless of volatility or the setting of Name_Req). 844 845 function Side_Effect_Free 846 (L : List_Id; 847 Name_Req : Boolean := False; 848 Variable_Ref : Boolean := False) return Boolean; 849 -- Determines if all elements of the list L are side effect free. Name_Req 850 -- and Variable_Ref are as described above. 851 852 procedure Silly_Boolean_Array_Not_Test (N : Node_Id; T : Entity_Id); 853 -- N is the node for a boolean array NOT operation, and T is the type of 854 -- the array. This routine deals with the silly case where the subtype of 855 -- the boolean array is False..False or True..True, where it is required 856 -- that a Constraint_Error exception be raised (RM 4.5.6(6)). 857 858 procedure Silly_Boolean_Array_Xor_Test (N : Node_Id; T : Entity_Id); 859 -- N is the node for a boolean array XOR operation, and T is the type of 860 -- the array. This routine deals with the silly case where the subtype of 861 -- the boolean array is True..True, where a raise of a Constraint_Error 862 -- exception is required (RM 4.5.6(6)). 863 864 function Target_Has_Fixed_Ops 865 (Left_Typ : Entity_Id; 866 Right_Typ : Entity_Id; 867 Result_Typ : Entity_Id) return Boolean; 868 -- Returns True if and only if the target machine has direct support 869 -- for fixed-by-fixed multiplications and divisions for the given 870 -- operand and result types. This is called in package Exp_Fixd to 871 -- determine whether to expand such operations. 872 873 function Type_May_Have_Bit_Aligned_Components 874 (Typ : Entity_Id) return Boolean; 875 -- Determines if Typ is a composite type that has within it (looking down 876 -- recursively at any subcomponents), a record type which has component 877 -- that may be bit aligned (see Possible_Bit_Aligned_Component). The result 878 -- is conservative, in that a result of False is decisive. A result of True 879 -- means that such a component may or may not be present. 880 881 function Within_Case_Or_If_Expression (N : Node_Id) return Boolean; 882 -- Determine whether arbitrary node N is within a case or an if expression 883 884 function Within_Internal_Subprogram return Boolean; 885 -- Indicates that some expansion is taking place within the body of a 886 -- predefined primitive operation. Some expansion activity (e.g. predicate 887 -- checks) is disabled in such. 888 889 procedure Wrap_Cleanup_Procedure (N : Node_Id); 890 -- Given an N_Subprogram_Body node, this procedure adds an Abort_Defer call 891 -- at the start of the statement sequence, and an Abort_Undefer call at the 892 -- end of the statement sequence. All cleanup routines (i.e. those that are 893 -- called from "at end" handlers) must defer abort on entry and undefer 894 -- abort on exit. Note that it is assumed that the code for the procedure 895 -- does not contain any return statements which would allow the flow of 896 -- control to escape doing the undefer call. 897 898private 899 pragma Inline (Duplicate_Subexpr); 900 pragma Inline (Force_Evaluation); 901 pragma Inline (Is_Library_Level_Tagged_Type); 902end Exp_Util; 903