1------------------------------------------------------------------------------ 2-- -- 3-- GNAT COMPILER COMPONENTS -- 4-- -- 5-- E X P _ C H 5 -- 6-- -- 7-- B o d y -- 8-- -- 9-- Copyright (C) 1992-2018, 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 26with Aspects; use Aspects; 27with Atree; use Atree; 28with Checks; use Checks; 29with Debug; use Debug; 30with Einfo; use Einfo; 31with Elists; use Elists; 32with Errout; use Errout; 33with Exp_Aggr; use Exp_Aggr; 34with Exp_Ch6; use Exp_Ch6; 35with Exp_Ch7; use Exp_Ch7; 36with Exp_Ch11; use Exp_Ch11; 37with Exp_Dbug; use Exp_Dbug; 38with Exp_Pakd; use Exp_Pakd; 39with Exp_Tss; use Exp_Tss; 40with Exp_Util; use Exp_Util; 41with Inline; use Inline; 42with Namet; use Namet; 43with Nlists; use Nlists; 44with Nmake; use Nmake; 45with Opt; use Opt; 46with Restrict; use Restrict; 47with Rident; use Rident; 48with Rtsfind; use Rtsfind; 49with Sinfo; use Sinfo; 50with Sem; use Sem; 51with Sem_Aux; use Sem_Aux; 52with Sem_Ch3; use Sem_Ch3; 53with Sem_Ch8; use Sem_Ch8; 54with Sem_Ch13; use Sem_Ch13; 55with Sem_Eval; use Sem_Eval; 56with Sem_Res; use Sem_Res; 57with Sem_Util; use Sem_Util; 58with Snames; use Snames; 59with Stand; use Stand; 60with Stringt; use Stringt; 61with Tbuild; use Tbuild; 62with Uintp; use Uintp; 63with Validsw; use Validsw; 64 65package body Exp_Ch5 is 66 67 procedure Build_Formal_Container_Iteration 68 (N : Node_Id; 69 Container : Entity_Id; 70 Cursor : Entity_Id; 71 Init : out Node_Id; 72 Advance : out Node_Id; 73 New_Loop : out Node_Id); 74 -- Utility to create declarations and loop statement for both forms 75 -- of formal container iterators. 76 77 function Convert_To_Iterable_Type 78 (Container : Entity_Id; 79 Loc : Source_Ptr) return Node_Id; 80 -- Returns New_Occurrence_Of (Container), possibly converted to an ancestor 81 -- type, if the type of Container inherited the Iterable aspect from that 82 -- ancestor. 83 84 function Change_Of_Representation (N : Node_Id) return Boolean; 85 -- Determine if the right-hand side of assignment N is a type conversion 86 -- which requires a change of representation. Called only for the array 87 -- and record cases. 88 89 procedure Expand_Assign_Array (N : Node_Id; Rhs : Node_Id); 90 -- N is an assignment which assigns an array value. This routine process 91 -- the various special cases and checks required for such assignments, 92 -- including change of representation. Rhs is normally simply the right- 93 -- hand side of the assignment, except that if the right-hand side is a 94 -- type conversion or a qualified expression, then the RHS is the actual 95 -- expression inside any such type conversions or qualifications. 96 97 function Expand_Assign_Array_Loop 98 (N : Node_Id; 99 Larray : Entity_Id; 100 Rarray : Entity_Id; 101 L_Type : Entity_Id; 102 R_Type : Entity_Id; 103 Ndim : Pos; 104 Rev : Boolean) return Node_Id; 105 -- N is an assignment statement which assigns an array value. This routine 106 -- expands the assignment into a loop (or nested loops for the case of a 107 -- multi-dimensional array) to do the assignment component by component. 108 -- Larray and Rarray are the entities of the actual arrays on the left-hand 109 -- and right-hand sides. L_Type and R_Type are the types of these arrays 110 -- (which may not be the same, due to either sliding, or to a change of 111 -- representation case). Ndim is the number of dimensions and the parameter 112 -- Rev indicates if the loops run normally (Rev = False), or reversed 113 -- (Rev = True). The value returned is the constructed loop statement. 114 -- Auxiliary declarations are inserted before node N using the standard 115 -- Insert_Actions mechanism. 116 117 procedure Expand_Assign_Record (N : Node_Id); 118 -- N is an assignment of an untagged record value. This routine handles 119 -- the case where the assignment must be made component by component, 120 -- either because the target is not byte aligned, or there is a change 121 -- of representation, or when we have a tagged type with a representation 122 -- clause (this last case is required because holes in the tagged type 123 -- might be filled with components from child types). 124 125 procedure Expand_Assign_With_Target_Names (N : Node_Id); 126 -- (AI12-0125): N is an assignment statement whose RHS contains occurrences 127 -- of @ that designate the value of the LHS of the assignment. If the LHS 128 -- is side-effect free the target names can be replaced with a copy of the 129 -- LHS; otherwise the semantics of the assignment is described in terms of 130 -- a procedure with an in-out parameter, and expanded as such. 131 132 procedure Expand_Formal_Container_Loop (N : Node_Id); 133 -- Use the primitives specified in an Iterable aspect to expand a loop 134 -- over a so-called formal container, primarily for SPARK usage. 135 136 procedure Expand_Formal_Container_Element_Loop (N : Node_Id); 137 -- Same, for an iterator of the form " For E of C". In this case the 138 -- iterator provides the name of the element, and the cursor is generated 139 -- internally. 140 141 procedure Expand_Iterator_Loop (N : Node_Id); 142 -- Expand loop over arrays and containers that uses the form "for X of C" 143 -- with an optional subtype mark, or "for Y in C". 144 145 procedure Expand_Iterator_Loop_Over_Container 146 (N : Node_Id; 147 Isc : Node_Id; 148 I_Spec : Node_Id; 149 Container : Node_Id; 150 Container_Typ : Entity_Id); 151 -- Expand loop over containers that uses the form "for X of C" with an 152 -- optional subtype mark, or "for Y in C". Isc is the iteration scheme. 153 -- I_Spec is the iterator specification and Container is either the 154 -- Container (for OF) or the iterator (for IN). 155 156 procedure Expand_Predicated_Loop (N : Node_Id); 157 -- Expand for loop over predicated subtype 158 159 function Make_Tag_Ctrl_Assignment (N : Node_Id) return List_Id; 160 -- Generate the necessary code for controlled and tagged assignment, that 161 -- is to say, finalization of the target before, adjustment of the target 162 -- after and save and restore of the tag and finalization pointers which 163 -- are not 'part of the value' and must not be changed upon assignment. N 164 -- is the original Assignment node. 165 166 -------------------------------------- 167 -- Build_Formal_Container_iteration -- 168 -------------------------------------- 169 170 procedure Build_Formal_Container_Iteration 171 (N : Node_Id; 172 Container : Entity_Id; 173 Cursor : Entity_Id; 174 Init : out Node_Id; 175 Advance : out Node_Id; 176 New_Loop : out Node_Id) 177 is 178 Loc : constant Source_Ptr := Sloc (N); 179 Stats : constant List_Id := Statements (N); 180 Typ : constant Entity_Id := Base_Type (Etype (Container)); 181 182 Has_Element_Op : constant Entity_Id := 183 Get_Iterable_Type_Primitive (Typ, Name_Has_Element); 184 185 First_Op : Entity_Id; 186 Next_Op : Entity_Id; 187 188 begin 189 -- Use the proper set of primitives depending on the direction of 190 -- iteration. The legality of a reverse iteration has been checked 191 -- during analysis. 192 193 if Reverse_Present (Iterator_Specification (Iteration_Scheme (N))) then 194 First_Op := Get_Iterable_Type_Primitive (Typ, Name_Last); 195 Next_Op := Get_Iterable_Type_Primitive (Typ, Name_Previous); 196 197 else 198 First_Op := Get_Iterable_Type_Primitive (Typ, Name_First); 199 Next_Op := Get_Iterable_Type_Primitive (Typ, Name_Next); 200 end if; 201 202 -- Declaration for Cursor 203 204 Init := 205 Make_Object_Declaration (Loc, 206 Defining_Identifier => Cursor, 207 Object_Definition => New_Occurrence_Of (Etype (First_Op), Loc), 208 Expression => 209 Make_Function_Call (Loc, 210 Name => New_Occurrence_Of (First_Op, Loc), 211 Parameter_Associations => New_List ( 212 Convert_To_Iterable_Type (Container, Loc)))); 213 214 -- Statement that advances (in the right direction) cursor in loop 215 216 Advance := 217 Make_Assignment_Statement (Loc, 218 Name => New_Occurrence_Of (Cursor, Loc), 219 Expression => 220 Make_Function_Call (Loc, 221 Name => New_Occurrence_Of (Next_Op, Loc), 222 Parameter_Associations => New_List ( 223 Convert_To_Iterable_Type (Container, Loc), 224 New_Occurrence_Of (Cursor, Loc)))); 225 226 -- Iterator is rewritten as a while_loop 227 228 New_Loop := 229 Make_Loop_Statement (Loc, 230 Iteration_Scheme => 231 Make_Iteration_Scheme (Loc, 232 Condition => 233 Make_Function_Call (Loc, 234 Name => New_Occurrence_Of (Has_Element_Op, Loc), 235 Parameter_Associations => New_List ( 236 Convert_To_Iterable_Type (Container, Loc), 237 New_Occurrence_Of (Cursor, Loc)))), 238 Statements => Stats, 239 End_Label => Empty); 240 end Build_Formal_Container_Iteration; 241 242 ------------------------------ 243 -- Change_Of_Representation -- 244 ------------------------------ 245 246 function Change_Of_Representation (N : Node_Id) return Boolean is 247 Rhs : constant Node_Id := Expression (N); 248 begin 249 return 250 Nkind (Rhs) = N_Type_Conversion 251 and then 252 not Same_Representation (Etype (Rhs), Etype (Expression (Rhs))); 253 end Change_Of_Representation; 254 255 ------------------------------ 256 -- Convert_To_Iterable_Type -- 257 ------------------------------ 258 259 function Convert_To_Iterable_Type 260 (Container : Entity_Id; 261 Loc : Source_Ptr) return Node_Id 262 is 263 Typ : constant Entity_Id := Base_Type (Etype (Container)); 264 Aspect : constant Node_Id := Find_Aspect (Typ, Aspect_Iterable); 265 Result : Node_Id; 266 267 begin 268 Result := New_Occurrence_Of (Container, Loc); 269 270 if Entity (Aspect) /= Typ then 271 Result := 272 Make_Type_Conversion (Loc, 273 Subtype_Mark => New_Occurrence_Of (Entity (Aspect), Loc), 274 Expression => Result); 275 end if; 276 277 return Result; 278 end Convert_To_Iterable_Type; 279 280 ------------------------- 281 -- Expand_Assign_Array -- 282 ------------------------- 283 284 -- There are two issues here. First, do we let Gigi do a block move, or 285 -- do we expand out into a loop? Second, we need to set the two flags 286 -- Forwards_OK and Backwards_OK which show whether the block move (or 287 -- corresponding loops) can be legitimately done in a forwards (low to 288 -- high) or backwards (high to low) manner. 289 290 procedure Expand_Assign_Array (N : Node_Id; Rhs : Node_Id) is 291 Loc : constant Source_Ptr := Sloc (N); 292 293 Lhs : constant Node_Id := Name (N); 294 295 Act_Lhs : constant Node_Id := Get_Referenced_Object (Lhs); 296 Act_Rhs : Node_Id := Get_Referenced_Object (Rhs); 297 298 L_Type : constant Entity_Id := 299 Underlying_Type (Get_Actual_Subtype (Act_Lhs)); 300 R_Type : Entity_Id := 301 Underlying_Type (Get_Actual_Subtype (Act_Rhs)); 302 303 L_Slice : constant Boolean := Nkind (Act_Lhs) = N_Slice; 304 R_Slice : constant Boolean := Nkind (Act_Rhs) = N_Slice; 305 306 Crep : constant Boolean := Change_Of_Representation (N); 307 308 Larray : Node_Id; 309 Rarray : Node_Id; 310 311 Ndim : constant Pos := Number_Dimensions (L_Type); 312 313 Loop_Required : Boolean := False; 314 -- This switch is set to True if the array move must be done using 315 -- an explicit front end generated loop. 316 317 procedure Apply_Dereference (Arg : Node_Id); 318 -- If the argument is an access to an array, and the assignment is 319 -- converted into a procedure call, apply explicit dereference. 320 321 function Has_Address_Clause (Exp : Node_Id) return Boolean; 322 -- Test if Exp is a reference to an array whose declaration has 323 -- an address clause, or it is a slice of such an array. 324 325 function Is_Formal_Array (Exp : Node_Id) return Boolean; 326 -- Test if Exp is a reference to an array which is either a formal 327 -- parameter or a slice of a formal parameter. These are the cases 328 -- where hidden aliasing can occur. 329 330 function Is_Non_Local_Array (Exp : Node_Id) return Boolean; 331 -- Determine if Exp is a reference to an array variable which is other 332 -- than an object defined in the current scope, or a component or a 333 -- slice of such an object. Such objects can be aliased to parameters 334 -- (unlike local array references). 335 336 ----------------------- 337 -- Apply_Dereference -- 338 ----------------------- 339 340 procedure Apply_Dereference (Arg : Node_Id) is 341 Typ : constant Entity_Id := Etype (Arg); 342 begin 343 if Is_Access_Type (Typ) then 344 Rewrite (Arg, Make_Explicit_Dereference (Loc, 345 Prefix => Relocate_Node (Arg))); 346 Analyze_And_Resolve (Arg, Designated_Type (Typ)); 347 end if; 348 end Apply_Dereference; 349 350 ------------------------ 351 -- Has_Address_Clause -- 352 ------------------------ 353 354 function Has_Address_Clause (Exp : Node_Id) return Boolean is 355 begin 356 return 357 (Is_Entity_Name (Exp) and then 358 Present (Address_Clause (Entity (Exp)))) 359 or else 360 (Nkind (Exp) = N_Slice and then Has_Address_Clause (Prefix (Exp))); 361 end Has_Address_Clause; 362 363 --------------------- 364 -- Is_Formal_Array -- 365 --------------------- 366 367 function Is_Formal_Array (Exp : Node_Id) return Boolean is 368 begin 369 return 370 (Is_Entity_Name (Exp) and then Is_Formal (Entity (Exp))) 371 or else 372 (Nkind (Exp) = N_Slice and then Is_Formal_Array (Prefix (Exp))); 373 end Is_Formal_Array; 374 375 ------------------------ 376 -- Is_Non_Local_Array -- 377 ------------------------ 378 379 function Is_Non_Local_Array (Exp : Node_Id) return Boolean is 380 begin 381 case Nkind (Exp) is 382 when N_Indexed_Component 383 | N_Selected_Component 384 | N_Slice 385 => 386 return Is_Non_Local_Array (Prefix (Exp)); 387 388 when others => 389 return 390 not (Is_Entity_Name (Exp) 391 and then Scope (Entity (Exp)) = Current_Scope); 392 end case; 393 end Is_Non_Local_Array; 394 395 -- Determine if Lhs, Rhs are formal arrays or nonlocal arrays 396 397 Lhs_Formal : constant Boolean := Is_Formal_Array (Act_Lhs); 398 Rhs_Formal : constant Boolean := Is_Formal_Array (Act_Rhs); 399 400 Lhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Lhs); 401 Rhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Rhs); 402 403 -- Start of processing for Expand_Assign_Array 404 405 begin 406 -- Deal with length check. Note that the length check is done with 407 -- respect to the right-hand side as given, not a possible underlying 408 -- renamed object, since this would generate incorrect extra checks. 409 410 Apply_Length_Check (Rhs, L_Type); 411 412 -- We start by assuming that the move can be done in either direction, 413 -- i.e. that the two sides are completely disjoint. 414 415 Set_Forwards_OK (N, True); 416 Set_Backwards_OK (N, True); 417 418 -- Normally it is only the slice case that can lead to overlap, and 419 -- explicit checks for slices are made below. But there is one case 420 -- where the slice can be implicit and invisible to us: when we have a 421 -- one dimensional array, and either both operands are parameters, or 422 -- one is a parameter (which can be a slice passed by reference) and the 423 -- other is a non-local variable. In this case the parameter could be a 424 -- slice that overlaps with the other operand. 425 426 -- However, if the array subtype is a constrained first subtype in the 427 -- parameter case, then we don't have to worry about overlap, since 428 -- slice assignments aren't possible (other than for a slice denoting 429 -- the whole array). 430 431 -- Note: No overlap is possible if there is a change of representation, 432 -- so we can exclude this case. 433 434 if Ndim = 1 435 and then not Crep 436 and then 437 ((Lhs_Formal and Rhs_Formal) 438 or else 439 (Lhs_Formal and Rhs_Non_Local_Var) 440 or else 441 (Rhs_Formal and Lhs_Non_Local_Var)) 442 and then 443 (not Is_Constrained (Etype (Lhs)) 444 or else not Is_First_Subtype (Etype (Lhs))) 445 then 446 Set_Forwards_OK (N, False); 447 Set_Backwards_OK (N, False); 448 449 -- Note: the bit-packed case is not worrisome here, since if we have 450 -- a slice passed as a parameter, it is always aligned on a byte 451 -- boundary, and if there are no explicit slices, the assignment 452 -- can be performed directly. 453 end if; 454 455 -- If either operand has an address clause clear Backwards_OK and 456 -- Forwards_OK, since we cannot tell if the operands overlap. We 457 -- exclude this treatment when Rhs is an aggregate, since we know 458 -- that overlap can't occur. 459 460 if (Has_Address_Clause (Lhs) and then Nkind (Rhs) /= N_Aggregate) 461 or else Has_Address_Clause (Rhs) 462 then 463 Set_Forwards_OK (N, False); 464 Set_Backwards_OK (N, False); 465 end if; 466 467 -- We certainly must use a loop for change of representation and also 468 -- we use the operand of the conversion on the right-hand side as the 469 -- effective right-hand side (the component types must match in this 470 -- situation). 471 472 if Crep then 473 Act_Rhs := Get_Referenced_Object (Rhs); 474 R_Type := Get_Actual_Subtype (Act_Rhs); 475 Loop_Required := True; 476 477 -- We require a loop if the left side is possibly bit unaligned 478 479 elsif Possible_Bit_Aligned_Component (Lhs) 480 or else 481 Possible_Bit_Aligned_Component (Rhs) 482 then 483 Loop_Required := True; 484 485 -- Arrays with controlled components are expanded into a loop to force 486 -- calls to Adjust at the component level. 487 488 elsif Has_Controlled_Component (L_Type) then 489 Loop_Required := True; 490 491 -- If object is atomic/VFA, we cannot tolerate a loop 492 493 elsif Is_Atomic_Or_VFA_Object (Act_Lhs) 494 or else 495 Is_Atomic_Or_VFA_Object (Act_Rhs) 496 then 497 return; 498 499 -- Loop is required if we have atomic components since we have to 500 -- be sure to do any accesses on an element by element basis. 501 502 elsif Has_Atomic_Components (L_Type) 503 or else Has_Atomic_Components (R_Type) 504 or else Is_Atomic_Or_VFA (Component_Type (L_Type)) 505 or else Is_Atomic_Or_VFA (Component_Type (R_Type)) 506 then 507 Loop_Required := True; 508 509 -- Case where no slice is involved 510 511 elsif not L_Slice and not R_Slice then 512 513 -- The following code deals with the case of unconstrained bit packed 514 -- arrays. The problem is that the template for such arrays contains 515 -- the bounds of the actual source level array, but the copy of an 516 -- entire array requires the bounds of the underlying array. It would 517 -- be nice if the back end could take care of this, but right now it 518 -- does not know how, so if we have such a type, then we expand out 519 -- into a loop, which is inefficient but works correctly. If we don't 520 -- do this, we get the wrong length computed for the array to be 521 -- moved. The two cases we need to worry about are: 522 523 -- Explicit dereference of an unconstrained packed array type as in 524 -- the following example: 525 526 -- procedure C52 is 527 -- type BITS is array(INTEGER range <>) of BOOLEAN; 528 -- pragma PACK(BITS); 529 -- type A is access BITS; 530 -- P1,P2 : A; 531 -- begin 532 -- P1 := new BITS (1 .. 65_535); 533 -- P2 := new BITS (1 .. 65_535); 534 -- P2.ALL := P1.ALL; 535 -- end C52; 536 537 -- A formal parameter reference with an unconstrained bit array type 538 -- is the other case we need to worry about (here we assume the same 539 -- BITS type declared above): 540 541 -- procedure Write_All (File : out BITS; Contents : BITS); 542 -- begin 543 -- File.Storage := Contents; 544 -- end Write_All; 545 546 -- We expand to a loop in either of these two cases 547 548 -- Question for future thought. Another potentially more efficient 549 -- approach would be to create the actual subtype, and then do an 550 -- unchecked conversion to this actual subtype ??? 551 552 Check_Unconstrained_Bit_Packed_Array : declare 553 554 function Is_UBPA_Reference (Opnd : Node_Id) return Boolean; 555 -- Function to perform required test for the first case, above 556 -- (dereference of an unconstrained bit packed array). 557 558 ----------------------- 559 -- Is_UBPA_Reference -- 560 ----------------------- 561 562 function Is_UBPA_Reference (Opnd : Node_Id) return Boolean is 563 Typ : constant Entity_Id := Underlying_Type (Etype (Opnd)); 564 P_Type : Entity_Id; 565 Des_Type : Entity_Id; 566 567 begin 568 if Present (Packed_Array_Impl_Type (Typ)) 569 and then Is_Array_Type (Packed_Array_Impl_Type (Typ)) 570 and then not Is_Constrained (Packed_Array_Impl_Type (Typ)) 571 then 572 return True; 573 574 elsif Nkind (Opnd) = N_Explicit_Dereference then 575 P_Type := Underlying_Type (Etype (Prefix (Opnd))); 576 577 if not Is_Access_Type (P_Type) then 578 return False; 579 580 else 581 Des_Type := Designated_Type (P_Type); 582 return 583 Is_Bit_Packed_Array (Des_Type) 584 and then not Is_Constrained (Des_Type); 585 end if; 586 587 else 588 return False; 589 end if; 590 end Is_UBPA_Reference; 591 592 -- Start of processing for Check_Unconstrained_Bit_Packed_Array 593 594 begin 595 if Is_UBPA_Reference (Lhs) 596 or else 597 Is_UBPA_Reference (Rhs) 598 then 599 Loop_Required := True; 600 601 -- Here if we do not have the case of a reference to a bit packed 602 -- unconstrained array case. In this case gigi can most certainly 603 -- handle the assignment if a forwards move is allowed. 604 605 -- (could it handle the backwards case also???) 606 607 elsif Forwards_OK (N) then 608 return; 609 end if; 610 end Check_Unconstrained_Bit_Packed_Array; 611 612 -- The back end can always handle the assignment if the right side is a 613 -- string literal (note that overlap is definitely impossible in this 614 -- case). If the type is packed, a string literal is always converted 615 -- into an aggregate, except in the case of a null slice, for which no 616 -- aggregate can be written. In that case, rewrite the assignment as a 617 -- null statement, a length check has already been emitted to verify 618 -- that the range of the left-hand side is empty. 619 620 -- Note that this code is not executed if we have an assignment of a 621 -- string literal to a non-bit aligned component of a record, a case 622 -- which cannot be handled by the backend. 623 624 elsif Nkind (Rhs) = N_String_Literal then 625 if String_Length (Strval (Rhs)) = 0 626 and then Is_Bit_Packed_Array (L_Type) 627 then 628 Rewrite (N, Make_Null_Statement (Loc)); 629 Analyze (N); 630 end if; 631 632 return; 633 634 -- If either operand is bit packed, then we need a loop, since we can't 635 -- be sure that the slice is byte aligned. Similarly, if either operand 636 -- is a possibly unaligned slice, then we need a loop (since the back 637 -- end cannot handle unaligned slices). 638 639 elsif Is_Bit_Packed_Array (L_Type) 640 or else Is_Bit_Packed_Array (R_Type) 641 or else Is_Possibly_Unaligned_Slice (Lhs) 642 or else Is_Possibly_Unaligned_Slice (Rhs) 643 then 644 Loop_Required := True; 645 646 -- If we are not bit-packed, and we have only one slice, then no overlap 647 -- is possible except in the parameter case, so we can let the back end 648 -- handle things. 649 650 elsif not (L_Slice and R_Slice) then 651 if Forwards_OK (N) then 652 return; 653 end if; 654 end if; 655 656 -- If the right-hand side is a string literal, introduce a temporary for 657 -- it, for use in the generated loop that will follow. 658 659 if Nkind (Rhs) = N_String_Literal then 660 declare 661 Temp : constant Entity_Id := Make_Temporary (Loc, 'T', Rhs); 662 Decl : Node_Id; 663 664 begin 665 Decl := 666 Make_Object_Declaration (Loc, 667 Defining_Identifier => Temp, 668 Object_Definition => New_Occurrence_Of (L_Type, Loc), 669 Expression => Relocate_Node (Rhs)); 670 671 Insert_Action (N, Decl); 672 Rewrite (Rhs, New_Occurrence_Of (Temp, Loc)); 673 R_Type := Etype (Temp); 674 end; 675 end if; 676 677 -- Come here to complete the analysis 678 679 -- Loop_Required: Set to True if we know that a loop is required 680 -- regardless of overlap considerations. 681 682 -- Forwards_OK: Set to False if we already know that a forwards 683 -- move is not safe, else set to True. 684 685 -- Backwards_OK: Set to False if we already know that a backwards 686 -- move is not safe, else set to True 687 688 -- Our task at this stage is to complete the overlap analysis, which can 689 -- result in possibly setting Forwards_OK or Backwards_OK to False, and 690 -- then generating the final code, either by deciding that it is OK 691 -- after all to let Gigi handle it, or by generating appropriate code 692 -- in the front end. 693 694 declare 695 L_Index_Typ : constant Node_Id := Etype (First_Index (L_Type)); 696 R_Index_Typ : constant Node_Id := Etype (First_Index (R_Type)); 697 698 Left_Lo : constant Node_Id := Type_Low_Bound (L_Index_Typ); 699 Left_Hi : constant Node_Id := Type_High_Bound (L_Index_Typ); 700 Right_Lo : constant Node_Id := Type_Low_Bound (R_Index_Typ); 701 Right_Hi : constant Node_Id := Type_High_Bound (R_Index_Typ); 702 703 Act_L_Array : Node_Id; 704 Act_R_Array : Node_Id; 705 706 Cleft_Lo : Node_Id; 707 Cright_Lo : Node_Id; 708 Condition : Node_Id; 709 710 Cresult : Compare_Result; 711 712 begin 713 -- Get the expressions for the arrays. If we are dealing with a 714 -- private type, then convert to the underlying type. We can do 715 -- direct assignments to an array that is a private type, but we 716 -- cannot assign to elements of the array without this extra 717 -- unchecked conversion. 718 719 -- Note: We propagate Parent to the conversion nodes to generate 720 -- a well-formed subtree. 721 722 if Nkind (Act_Lhs) = N_Slice then 723 Larray := Prefix (Act_Lhs); 724 else 725 Larray := Act_Lhs; 726 727 if Is_Private_Type (Etype (Larray)) then 728 declare 729 Par : constant Node_Id := Parent (Larray); 730 begin 731 Larray := 732 Unchecked_Convert_To 733 (Underlying_Type (Etype (Larray)), Larray); 734 Set_Parent (Larray, Par); 735 end; 736 end if; 737 end if; 738 739 if Nkind (Act_Rhs) = N_Slice then 740 Rarray := Prefix (Act_Rhs); 741 else 742 Rarray := Act_Rhs; 743 744 if Is_Private_Type (Etype (Rarray)) then 745 declare 746 Par : constant Node_Id := Parent (Rarray); 747 begin 748 Rarray := 749 Unchecked_Convert_To 750 (Underlying_Type (Etype (Rarray)), Rarray); 751 Set_Parent (Rarray, Par); 752 end; 753 end if; 754 end if; 755 756 -- If both sides are slices, we must figure out whether it is safe 757 -- to do the move in one direction or the other. It is always safe 758 -- if there is a change of representation since obviously two arrays 759 -- with different representations cannot possibly overlap. 760 761 if (not Crep) and L_Slice and R_Slice then 762 Act_L_Array := Get_Referenced_Object (Prefix (Act_Lhs)); 763 Act_R_Array := Get_Referenced_Object (Prefix (Act_Rhs)); 764 765 -- If both left- and right-hand arrays are entity names, and refer 766 -- to different entities, then we know that the move is safe (the 767 -- two storage areas are completely disjoint). 768 769 if Is_Entity_Name (Act_L_Array) 770 and then Is_Entity_Name (Act_R_Array) 771 and then Entity (Act_L_Array) /= Entity (Act_R_Array) 772 then 773 null; 774 775 -- Otherwise, we assume the worst, which is that the two arrays 776 -- are the same array. There is no need to check if we know that 777 -- is the case, because if we don't know it, we still have to 778 -- assume it. 779 780 -- Generally if the same array is involved, then we have an 781 -- overlapping case. We will have to really assume the worst (i.e. 782 -- set neither of the OK flags) unless we can determine the lower 783 -- or upper bounds at compile time and compare them. 784 785 else 786 Cresult := 787 Compile_Time_Compare 788 (Left_Lo, Right_Lo, Assume_Valid => True); 789 790 if Cresult = Unknown then 791 Cresult := 792 Compile_Time_Compare 793 (Left_Hi, Right_Hi, Assume_Valid => True); 794 end if; 795 796 case Cresult is 797 when EQ | LE | LT => 798 Set_Backwards_OK (N, False); 799 800 when GE | GT => 801 Set_Forwards_OK (N, False); 802 803 when NE | Unknown => 804 Set_Backwards_OK (N, False); 805 Set_Forwards_OK (N, False); 806 end case; 807 end if; 808 end if; 809 810 -- If after that analysis Loop_Required is False, meaning that we 811 -- have not discovered some non-overlap reason for requiring a loop, 812 -- then the outcome depends on the capabilities of the back end. 813 814 if not Loop_Required then 815 -- Assume the back end can deal with all cases of overlap by 816 -- falling back to memmove if it cannot use a more efficient 817 -- approach. 818 819 return; 820 end if; 821 822 -- At this stage we have to generate an explicit loop, and we have 823 -- the following cases: 824 825 -- Forwards_OK = True 826 827 -- Rnn : right_index := right_index'First; 828 -- for Lnn in left-index loop 829 -- left (Lnn) := right (Rnn); 830 -- Rnn := right_index'Succ (Rnn); 831 -- end loop; 832 833 -- Note: the above code MUST be analyzed with checks off, because 834 -- otherwise the Succ could overflow. But in any case this is more 835 -- efficient. 836 837 -- Forwards_OK = False, Backwards_OK = True 838 839 -- Rnn : right_index := right_index'Last; 840 -- for Lnn in reverse left-index loop 841 -- left (Lnn) := right (Rnn); 842 -- Rnn := right_index'Pred (Rnn); 843 -- end loop; 844 845 -- Note: the above code MUST be analyzed with checks off, because 846 -- otherwise the Pred could overflow. But in any case this is more 847 -- efficient. 848 849 -- Forwards_OK = Backwards_OK = False 850 851 -- This only happens if we have the same array on each side. It is 852 -- possible to create situations using overlays that violate this, 853 -- but we simply do not promise to get this "right" in this case. 854 855 -- There are two possible subcases. If the No_Implicit_Conditionals 856 -- restriction is set, then we generate the following code: 857 858 -- declare 859 -- T : constant <operand-type> := rhs; 860 -- begin 861 -- lhs := T; 862 -- end; 863 864 -- If implicit conditionals are permitted, then we generate: 865 866 -- if Left_Lo <= Right_Lo then 867 -- <code for Forwards_OK = True above> 868 -- else 869 -- <code for Backwards_OK = True above> 870 -- end if; 871 872 -- In order to detect possible aliasing, we examine the renamed 873 -- expression when the source or target is a renaming. However, 874 -- the renaming may be intended to capture an address that may be 875 -- affected by subsequent code, and therefore we must recover 876 -- the actual entity for the expansion that follows, not the 877 -- object it renames. In particular, if source or target designate 878 -- a portion of a dynamically allocated object, the pointer to it 879 -- may be reassigned but the renaming preserves the proper location. 880 881 if Is_Entity_Name (Rhs) 882 and then 883 Nkind (Parent (Entity (Rhs))) = N_Object_Renaming_Declaration 884 and then Nkind (Act_Rhs) = N_Slice 885 then 886 Rarray := Rhs; 887 end if; 888 889 if Is_Entity_Name (Lhs) 890 and then 891 Nkind (Parent (Entity (Lhs))) = N_Object_Renaming_Declaration 892 and then Nkind (Act_Lhs) = N_Slice 893 then 894 Larray := Lhs; 895 end if; 896 897 -- Cases where either Forwards_OK or Backwards_OK is true 898 899 if Forwards_OK (N) or else Backwards_OK (N) then 900 if Needs_Finalization (Component_Type (L_Type)) 901 and then Base_Type (L_Type) = Base_Type (R_Type) 902 and then Ndim = 1 903 and then not No_Ctrl_Actions (N) 904 then 905 declare 906 Proc : constant Entity_Id := 907 TSS (Base_Type (L_Type), TSS_Slice_Assign); 908 Actuals : List_Id; 909 910 begin 911 Apply_Dereference (Larray); 912 Apply_Dereference (Rarray); 913 Actuals := New_List ( 914 Duplicate_Subexpr (Larray, Name_Req => True), 915 Duplicate_Subexpr (Rarray, Name_Req => True), 916 Duplicate_Subexpr (Left_Lo, Name_Req => True), 917 Duplicate_Subexpr (Left_Hi, Name_Req => True), 918 Duplicate_Subexpr (Right_Lo, Name_Req => True), 919 Duplicate_Subexpr (Right_Hi, Name_Req => True)); 920 921 Append_To (Actuals, 922 New_Occurrence_Of ( 923 Boolean_Literals (not Forwards_OK (N)), Loc)); 924 925 Rewrite (N, 926 Make_Procedure_Call_Statement (Loc, 927 Name => New_Occurrence_Of (Proc, Loc), 928 Parameter_Associations => Actuals)); 929 end; 930 931 else 932 Rewrite (N, 933 Expand_Assign_Array_Loop 934 (N, Larray, Rarray, L_Type, R_Type, Ndim, 935 Rev => not Forwards_OK (N))); 936 end if; 937 938 -- Case of both are false with No_Implicit_Conditionals 939 940 elsif Restriction_Active (No_Implicit_Conditionals) then 941 declare 942 T : constant Entity_Id := 943 Make_Defining_Identifier (Loc, Chars => Name_T); 944 945 begin 946 Rewrite (N, 947 Make_Block_Statement (Loc, 948 Declarations => New_List ( 949 Make_Object_Declaration (Loc, 950 Defining_Identifier => T, 951 Constant_Present => True, 952 Object_Definition => 953 New_Occurrence_Of (Etype (Rhs), Loc), 954 Expression => Relocate_Node (Rhs))), 955 956 Handled_Statement_Sequence => 957 Make_Handled_Sequence_Of_Statements (Loc, 958 Statements => New_List ( 959 Make_Assignment_Statement (Loc, 960 Name => Relocate_Node (Lhs), 961 Expression => New_Occurrence_Of (T, Loc)))))); 962 end; 963 964 -- Case of both are false with implicit conditionals allowed 965 966 else 967 -- Before we generate this code, we must ensure that the left and 968 -- right side array types are defined. They may be itypes, and we 969 -- cannot let them be defined inside the if, since the first use 970 -- in the then may not be executed. 971 972 Ensure_Defined (L_Type, N); 973 Ensure_Defined (R_Type, N); 974 975 -- We normally compare addresses to find out which way round to 976 -- do the loop, since this is reliable, and handles the cases of 977 -- parameters, conversions etc. But we can't do that in the bit 978 -- packed case, because addresses don't work there. 979 980 if not Is_Bit_Packed_Array (L_Type) then 981 Condition := 982 Make_Op_Le (Loc, 983 Left_Opnd => 984 Unchecked_Convert_To (RTE (RE_Integer_Address), 985 Make_Attribute_Reference (Loc, 986 Prefix => 987 Make_Indexed_Component (Loc, 988 Prefix => 989 Duplicate_Subexpr_Move_Checks (Larray, True), 990 Expressions => New_List ( 991 Make_Attribute_Reference (Loc, 992 Prefix => 993 New_Occurrence_Of 994 (L_Index_Typ, Loc), 995 Attribute_Name => Name_First))), 996 Attribute_Name => Name_Address)), 997 998 Right_Opnd => 999 Unchecked_Convert_To (RTE (RE_Integer_Address), 1000 Make_Attribute_Reference (Loc, 1001 Prefix => 1002 Make_Indexed_Component (Loc, 1003 Prefix => 1004 Duplicate_Subexpr_Move_Checks (Rarray, True), 1005 Expressions => New_List ( 1006 Make_Attribute_Reference (Loc, 1007 Prefix => 1008 New_Occurrence_Of 1009 (R_Index_Typ, Loc), 1010 Attribute_Name => Name_First))), 1011 Attribute_Name => Name_Address))); 1012 1013 -- For the bit packed and VM cases we use the bounds. That's OK, 1014 -- because we don't have to worry about parameters, since they 1015 -- cannot cause overlap. Perhaps we should worry about weird slice 1016 -- conversions ??? 1017 1018 else 1019 -- Copy the bounds 1020 1021 Cleft_Lo := New_Copy_Tree (Left_Lo); 1022 Cright_Lo := New_Copy_Tree (Right_Lo); 1023 1024 -- If the types do not match we add an implicit conversion 1025 -- here to ensure proper match 1026 1027 if Etype (Left_Lo) /= Etype (Right_Lo) then 1028 Cright_Lo := 1029 Unchecked_Convert_To (Etype (Left_Lo), Cright_Lo); 1030 end if; 1031 1032 -- Reset the Analyzed flag, because the bounds of the index 1033 -- type itself may be universal, and must must be reanalyzed 1034 -- to acquire the proper type for the back end. 1035 1036 Set_Analyzed (Cleft_Lo, False); 1037 Set_Analyzed (Cright_Lo, False); 1038 1039 Condition := 1040 Make_Op_Le (Loc, 1041 Left_Opnd => Cleft_Lo, 1042 Right_Opnd => Cright_Lo); 1043 end if; 1044 1045 if Needs_Finalization (Component_Type (L_Type)) 1046 and then Base_Type (L_Type) = Base_Type (R_Type) 1047 and then Ndim = 1 1048 and then not No_Ctrl_Actions (N) 1049 then 1050 1051 -- Call TSS procedure for array assignment, passing the 1052 -- explicit bounds of right- and left-hand sides. 1053 1054 declare 1055 Proc : constant Entity_Id := 1056 TSS (Base_Type (L_Type), TSS_Slice_Assign); 1057 Actuals : List_Id; 1058 1059 begin 1060 Apply_Dereference (Larray); 1061 Apply_Dereference (Rarray); 1062 Actuals := New_List ( 1063 Duplicate_Subexpr (Larray, Name_Req => True), 1064 Duplicate_Subexpr (Rarray, Name_Req => True), 1065 Duplicate_Subexpr (Left_Lo, Name_Req => True), 1066 Duplicate_Subexpr (Left_Hi, Name_Req => True), 1067 Duplicate_Subexpr (Right_Lo, Name_Req => True), 1068 Duplicate_Subexpr (Right_Hi, Name_Req => True)); 1069 1070 Append_To (Actuals, 1071 Make_Op_Not (Loc, 1072 Right_Opnd => Condition)); 1073 1074 Rewrite (N, 1075 Make_Procedure_Call_Statement (Loc, 1076 Name => New_Occurrence_Of (Proc, Loc), 1077 Parameter_Associations => Actuals)); 1078 end; 1079 1080 else 1081 Rewrite (N, 1082 Make_Implicit_If_Statement (N, 1083 Condition => Condition, 1084 1085 Then_Statements => New_List ( 1086 Expand_Assign_Array_Loop 1087 (N, Larray, Rarray, L_Type, R_Type, Ndim, 1088 Rev => False)), 1089 1090 Else_Statements => New_List ( 1091 Expand_Assign_Array_Loop 1092 (N, Larray, Rarray, L_Type, R_Type, Ndim, 1093 Rev => True)))); 1094 end if; 1095 end if; 1096 1097 Analyze (N, Suppress => All_Checks); 1098 end; 1099 1100 exception 1101 when RE_Not_Available => 1102 return; 1103 end Expand_Assign_Array; 1104 1105 ------------------------------ 1106 -- Expand_Assign_Array_Loop -- 1107 ------------------------------ 1108 1109 -- The following is an example of the loop generated for the case of a 1110 -- two-dimensional array: 1111 1112 -- declare 1113 -- R2b : Tm1X1 := 1; 1114 -- begin 1115 -- for L1b in 1 .. 100 loop 1116 -- declare 1117 -- R4b : Tm1X2 := 1; 1118 -- begin 1119 -- for L3b in 1 .. 100 loop 1120 -- vm1 (L1b, L3b) := vm2 (R2b, R4b); 1121 -- R4b := Tm1X2'succ(R4b); 1122 -- end loop; 1123 -- end; 1124 -- R2b := Tm1X1'succ(R2b); 1125 -- end loop; 1126 -- end; 1127 1128 -- Here Rev is False, and Tm1Xn are the subscript types for the right-hand 1129 -- side. The declarations of R2b and R4b are inserted before the original 1130 -- assignment statement. 1131 1132 function Expand_Assign_Array_Loop 1133 (N : Node_Id; 1134 Larray : Entity_Id; 1135 Rarray : Entity_Id; 1136 L_Type : Entity_Id; 1137 R_Type : Entity_Id; 1138 Ndim : Pos; 1139 Rev : Boolean) return Node_Id 1140 is 1141 Loc : constant Source_Ptr := Sloc (N); 1142 1143 Lnn : array (1 .. Ndim) of Entity_Id; 1144 Rnn : array (1 .. Ndim) of Entity_Id; 1145 -- Entities used as subscripts on left and right sides 1146 1147 L_Index_Type : array (1 .. Ndim) of Entity_Id; 1148 R_Index_Type : array (1 .. Ndim) of Entity_Id; 1149 -- Left and right index types 1150 1151 Assign : Node_Id; 1152 1153 F_Or_L : Name_Id; 1154 S_Or_P : Name_Id; 1155 1156 function Build_Step (J : Nat) return Node_Id; 1157 -- The increment step for the index of the right-hand side is written 1158 -- as an attribute reference (Succ or Pred). This function returns 1159 -- the corresponding node, which is placed at the end of the loop body. 1160 1161 ---------------- 1162 -- Build_Step -- 1163 ---------------- 1164 1165 function Build_Step (J : Nat) return Node_Id is 1166 Step : Node_Id; 1167 Lim : Name_Id; 1168 1169 begin 1170 if Rev then 1171 Lim := Name_First; 1172 else 1173 Lim := Name_Last; 1174 end if; 1175 1176 Step := 1177 Make_Assignment_Statement (Loc, 1178 Name => New_Occurrence_Of (Rnn (J), Loc), 1179 Expression => 1180 Make_Attribute_Reference (Loc, 1181 Prefix => 1182 New_Occurrence_Of (R_Index_Type (J), Loc), 1183 Attribute_Name => S_Or_P, 1184 Expressions => New_List ( 1185 New_Occurrence_Of (Rnn (J), Loc)))); 1186 1187 -- Note that on the last iteration of the loop, the index is increased 1188 -- (or decreased) past the corresponding bound. This is consistent with 1189 -- the C semantics of the back-end, where such an off-by-one value on a 1190 -- dead index variable is OK. However, in CodePeer mode this leads to 1191 -- spurious warnings, and thus we place a guard around the attribute 1192 -- reference. For obvious reasons we only do this for CodePeer. 1193 1194 if CodePeer_Mode then 1195 Step := 1196 Make_If_Statement (Loc, 1197 Condition => 1198 Make_Op_Ne (Loc, 1199 Left_Opnd => New_Occurrence_Of (Lnn (J), Loc), 1200 Right_Opnd => 1201 Make_Attribute_Reference (Loc, 1202 Prefix => New_Occurrence_Of (L_Index_Type (J), Loc), 1203 Attribute_Name => Lim)), 1204 Then_Statements => New_List (Step)); 1205 end if; 1206 1207 return Step; 1208 end Build_Step; 1209 1210 -- Start of processing for Expand_Assign_Array_Loop 1211 1212 begin 1213 if Rev then 1214 F_Or_L := Name_Last; 1215 S_Or_P := Name_Pred; 1216 else 1217 F_Or_L := Name_First; 1218 S_Or_P := Name_Succ; 1219 end if; 1220 1221 -- Setup index types and subscript entities 1222 1223 declare 1224 L_Index : Node_Id; 1225 R_Index : Node_Id; 1226 1227 begin 1228 L_Index := First_Index (L_Type); 1229 R_Index := First_Index (R_Type); 1230 1231 for J in 1 .. Ndim loop 1232 Lnn (J) := Make_Temporary (Loc, 'L'); 1233 Rnn (J) := Make_Temporary (Loc, 'R'); 1234 1235 L_Index_Type (J) := Etype (L_Index); 1236 R_Index_Type (J) := Etype (R_Index); 1237 1238 Next_Index (L_Index); 1239 Next_Index (R_Index); 1240 end loop; 1241 end; 1242 1243 -- Now construct the assignment statement 1244 1245 declare 1246 ExprL : constant List_Id := New_List; 1247 ExprR : constant List_Id := New_List; 1248 1249 begin 1250 for J in 1 .. Ndim loop 1251 Append_To (ExprL, New_Occurrence_Of (Lnn (J), Loc)); 1252 Append_To (ExprR, New_Occurrence_Of (Rnn (J), Loc)); 1253 end loop; 1254 1255 Assign := 1256 Make_Assignment_Statement (Loc, 1257 Name => 1258 Make_Indexed_Component (Loc, 1259 Prefix => Duplicate_Subexpr (Larray, Name_Req => True), 1260 Expressions => ExprL), 1261 Expression => 1262 Make_Indexed_Component (Loc, 1263 Prefix => Duplicate_Subexpr (Rarray, Name_Req => True), 1264 Expressions => ExprR)); 1265 1266 -- We set assignment OK, since there are some cases, e.g. in object 1267 -- declarations, where we are actually assigning into a constant. 1268 -- If there really is an illegality, it was caught long before now, 1269 -- and was flagged when the original assignment was analyzed. 1270 1271 Set_Assignment_OK (Name (Assign)); 1272 1273 -- Propagate the No_Ctrl_Actions flag to individual assignments 1274 1275 Set_No_Ctrl_Actions (Assign, No_Ctrl_Actions (N)); 1276 end; 1277 1278 -- Now construct the loop from the inside out, with the last subscript 1279 -- varying most rapidly. Note that Assign is first the raw assignment 1280 -- statement, and then subsequently the loop that wraps it up. 1281 1282 for J in reverse 1 .. Ndim loop 1283 Assign := 1284 Make_Block_Statement (Loc, 1285 Declarations => New_List ( 1286 Make_Object_Declaration (Loc, 1287 Defining_Identifier => Rnn (J), 1288 Object_Definition => 1289 New_Occurrence_Of (R_Index_Type (J), Loc), 1290 Expression => 1291 Make_Attribute_Reference (Loc, 1292 Prefix => New_Occurrence_Of (R_Index_Type (J), Loc), 1293 Attribute_Name => F_Or_L))), 1294 1295 Handled_Statement_Sequence => 1296 Make_Handled_Sequence_Of_Statements (Loc, 1297 Statements => New_List ( 1298 Make_Implicit_Loop_Statement (N, 1299 Iteration_Scheme => 1300 Make_Iteration_Scheme (Loc, 1301 Loop_Parameter_Specification => 1302 Make_Loop_Parameter_Specification (Loc, 1303 Defining_Identifier => Lnn (J), 1304 Reverse_Present => Rev, 1305 Discrete_Subtype_Definition => 1306 New_Occurrence_Of (L_Index_Type (J), Loc))), 1307 1308 Statements => New_List (Assign, Build_Step (J)))))); 1309 end loop; 1310 1311 return Assign; 1312 end Expand_Assign_Array_Loop; 1313 1314 -------------------------- 1315 -- Expand_Assign_Record -- 1316 -------------------------- 1317 1318 procedure Expand_Assign_Record (N : Node_Id) is 1319 Lhs : constant Node_Id := Name (N); 1320 Rhs : Node_Id := Expression (N); 1321 L_Typ : constant Entity_Id := Base_Type (Etype (Lhs)); 1322 1323 begin 1324 -- If change of representation, then extract the real right-hand side 1325 -- from the type conversion, and proceed with component-wise assignment, 1326 -- since the two types are not the same as far as the back end is 1327 -- concerned. 1328 1329 if Change_Of_Representation (N) then 1330 Rhs := Expression (Rhs); 1331 1332 -- If this may be a case of a large bit aligned component, then proceed 1333 -- with component-wise assignment, to avoid possible clobbering of other 1334 -- components sharing bits in the first or last byte of the component to 1335 -- be assigned. 1336 1337 elsif Possible_Bit_Aligned_Component (Lhs) 1338 or 1339 Possible_Bit_Aligned_Component (Rhs) 1340 then 1341 null; 1342 1343 -- If we have a tagged type that has a complete record representation 1344 -- clause, we must do we must do component-wise assignments, since child 1345 -- types may have used gaps for their components, and we might be 1346 -- dealing with a view conversion. 1347 1348 elsif Is_Fully_Repped_Tagged_Type (L_Typ) then 1349 null; 1350 1351 -- If neither condition met, then nothing special to do, the back end 1352 -- can handle assignment of the entire component as a single entity. 1353 1354 else 1355 return; 1356 end if; 1357 1358 -- At this stage we know that we must do a component wise assignment 1359 1360 declare 1361 Loc : constant Source_Ptr := Sloc (N); 1362 R_Typ : constant Entity_Id := Base_Type (Etype (Rhs)); 1363 Decl : constant Node_Id := Declaration_Node (R_Typ); 1364 RDef : Node_Id; 1365 F : Entity_Id; 1366 1367 function Find_Component 1368 (Typ : Entity_Id; 1369 Comp : Entity_Id) return Entity_Id; 1370 -- Find the component with the given name in the underlying record 1371 -- declaration for Typ. We need to use the actual entity because the 1372 -- type may be private and resolution by identifier alone would fail. 1373 1374 function Make_Component_List_Assign 1375 (CL : Node_Id; 1376 U_U : Boolean := False) return List_Id; 1377 -- Returns a sequence of statements to assign the components that 1378 -- are referenced in the given component list. The flag U_U is 1379 -- used to force the usage of the inferred value of the variant 1380 -- part expression as the switch for the generated case statement. 1381 1382 function Make_Field_Assign 1383 (C : Entity_Id; 1384 U_U : Boolean := False) return Node_Id; 1385 -- Given C, the entity for a discriminant or component, build an 1386 -- assignment for the corresponding field values. The flag U_U 1387 -- signals the presence of an Unchecked_Union and forces the usage 1388 -- of the inferred discriminant value of C as the right-hand side 1389 -- of the assignment. 1390 1391 function Make_Field_Assigns (CI : List_Id) return List_Id; 1392 -- Given CI, a component items list, construct series of statements 1393 -- for fieldwise assignment of the corresponding components. 1394 1395 -------------------- 1396 -- Find_Component -- 1397 -------------------- 1398 1399 function Find_Component 1400 (Typ : Entity_Id; 1401 Comp : Entity_Id) return Entity_Id 1402 is 1403 Utyp : constant Entity_Id := Underlying_Type (Typ); 1404 C : Entity_Id; 1405 1406 begin 1407 C := First_Entity (Utyp); 1408 while Present (C) loop 1409 if Chars (C) = Chars (Comp) then 1410 return C; 1411 end if; 1412 1413 Next_Entity (C); 1414 end loop; 1415 1416 raise Program_Error; 1417 end Find_Component; 1418 1419 -------------------------------- 1420 -- Make_Component_List_Assign -- 1421 -------------------------------- 1422 1423 function Make_Component_List_Assign 1424 (CL : Node_Id; 1425 U_U : Boolean := False) return List_Id 1426 is 1427 CI : constant List_Id := Component_Items (CL); 1428 VP : constant Node_Id := Variant_Part (CL); 1429 1430 Alts : List_Id; 1431 DC : Node_Id; 1432 DCH : List_Id; 1433 Expr : Node_Id; 1434 Result : List_Id; 1435 V : Node_Id; 1436 1437 begin 1438 Result := Make_Field_Assigns (CI); 1439 1440 if Present (VP) then 1441 V := First_Non_Pragma (Variants (VP)); 1442 Alts := New_List; 1443 while Present (V) loop 1444 DCH := New_List; 1445 DC := First (Discrete_Choices (V)); 1446 while Present (DC) loop 1447 Append_To (DCH, New_Copy_Tree (DC)); 1448 Next (DC); 1449 end loop; 1450 1451 Append_To (Alts, 1452 Make_Case_Statement_Alternative (Loc, 1453 Discrete_Choices => DCH, 1454 Statements => 1455 Make_Component_List_Assign (Component_List (V)))); 1456 Next_Non_Pragma (V); 1457 end loop; 1458 1459 -- If we have an Unchecked_Union, use the value of the inferred 1460 -- discriminant of the variant part expression as the switch 1461 -- for the case statement. The case statement may later be 1462 -- folded. 1463 1464 if U_U then 1465 Expr := 1466 New_Copy (Get_Discriminant_Value ( 1467 Entity (Name (VP)), 1468 Etype (Rhs), 1469 Discriminant_Constraint (Etype (Rhs)))); 1470 else 1471 Expr := 1472 Make_Selected_Component (Loc, 1473 Prefix => Duplicate_Subexpr (Rhs), 1474 Selector_Name => 1475 Make_Identifier (Loc, Chars (Name (VP)))); 1476 end if; 1477 1478 Append_To (Result, 1479 Make_Case_Statement (Loc, 1480 Expression => Expr, 1481 Alternatives => Alts)); 1482 end if; 1483 1484 return Result; 1485 end Make_Component_List_Assign; 1486 1487 ----------------------- 1488 -- Make_Field_Assign -- 1489 ----------------------- 1490 1491 function Make_Field_Assign 1492 (C : Entity_Id; 1493 U_U : Boolean := False) return Node_Id 1494 is 1495 A : Node_Id; 1496 Disc : Entity_Id; 1497 Expr : Node_Id; 1498 1499 begin 1500 -- The discriminant entity to be used in the retrieval below must 1501 -- be one in the corresponding type, given that the assignment may 1502 -- be between derived and parent types. 1503 1504 if Is_Derived_Type (Etype (Rhs)) then 1505 Disc := Find_Component (R_Typ, C); 1506 else 1507 Disc := C; 1508 end if; 1509 1510 -- In the case of an Unchecked_Union, use the discriminant 1511 -- constraint value as on the right-hand side of the assignment. 1512 1513 if U_U then 1514 Expr := 1515 New_Copy (Get_Discriminant_Value (C, 1516 Etype (Rhs), 1517 Discriminant_Constraint (Etype (Rhs)))); 1518 else 1519 Expr := 1520 Make_Selected_Component (Loc, 1521 Prefix => Duplicate_Subexpr (Rhs), 1522 Selector_Name => New_Occurrence_Of (Disc, Loc)); 1523 end if; 1524 1525 A := 1526 Make_Assignment_Statement (Loc, 1527 Name => 1528 Make_Selected_Component (Loc, 1529 Prefix => Duplicate_Subexpr (Lhs), 1530 Selector_Name => 1531 New_Occurrence_Of (Find_Component (L_Typ, C), Loc)), 1532 Expression => Expr); 1533 1534 -- Set Assignment_OK, so discriminants can be assigned 1535 1536 Set_Assignment_OK (Name (A), True); 1537 1538 if Componentwise_Assignment (N) 1539 and then Nkind (Name (A)) = N_Selected_Component 1540 and then Chars (Selector_Name (Name (A))) = Name_uParent 1541 then 1542 Set_Componentwise_Assignment (A); 1543 end if; 1544 1545 return A; 1546 end Make_Field_Assign; 1547 1548 ------------------------ 1549 -- Make_Field_Assigns -- 1550 ------------------------ 1551 1552 function Make_Field_Assigns (CI : List_Id) return List_Id is 1553 Item : Node_Id; 1554 Result : List_Id; 1555 1556 begin 1557 Item := First (CI); 1558 Result := New_List; 1559 1560 while Present (Item) loop 1561 1562 -- Look for components, but exclude _tag field assignment if 1563 -- the special Componentwise_Assignment flag is set. 1564 1565 if Nkind (Item) = N_Component_Declaration 1566 and then not (Is_Tag (Defining_Identifier (Item)) 1567 and then Componentwise_Assignment (N)) 1568 then 1569 Append_To 1570 (Result, Make_Field_Assign (Defining_Identifier (Item))); 1571 end if; 1572 1573 Next (Item); 1574 end loop; 1575 1576 return Result; 1577 end Make_Field_Assigns; 1578 1579 -- Start of processing for Expand_Assign_Record 1580 1581 begin 1582 -- Note that we use the base types for this processing. This results 1583 -- in some extra work in the constrained case, but the change of 1584 -- representation case is so unusual that it is not worth the effort. 1585 1586 -- First copy the discriminants. This is done unconditionally. It 1587 -- is required in the unconstrained left side case, and also in the 1588 -- case where this assignment was constructed during the expansion 1589 -- of a type conversion (since initialization of discriminants is 1590 -- suppressed in this case). It is unnecessary but harmless in 1591 -- other cases. 1592 1593 -- Special case: no copy if the target has no discriminants 1594 1595 if Has_Discriminants (L_Typ) 1596 and then Is_Unchecked_Union (Base_Type (L_Typ)) 1597 then 1598 null; 1599 1600 elsif Has_Discriminants (L_Typ) then 1601 F := First_Discriminant (R_Typ); 1602 while Present (F) loop 1603 1604 -- If we are expanding the initialization of a derived record 1605 -- that constrains or renames discriminants of the parent, we 1606 -- must use the corresponding discriminant in the parent. 1607 1608 declare 1609 CF : Entity_Id; 1610 1611 begin 1612 if Inside_Init_Proc 1613 and then Present (Corresponding_Discriminant (F)) 1614 then 1615 CF := Corresponding_Discriminant (F); 1616 else 1617 CF := F; 1618 end if; 1619 1620 if Is_Unchecked_Union (Base_Type (R_Typ)) then 1621 1622 -- Within an initialization procedure this is the 1623 -- assignment to an unchecked union component, in which 1624 -- case there is no discriminant to initialize. 1625 1626 if Inside_Init_Proc then 1627 null; 1628 1629 else 1630 -- The assignment is part of a conversion from a 1631 -- derived unchecked union type with an inferable 1632 -- discriminant, to a parent type. 1633 1634 Insert_Action (N, Make_Field_Assign (CF, True)); 1635 end if; 1636 1637 else 1638 Insert_Action (N, Make_Field_Assign (CF)); 1639 end if; 1640 1641 Next_Discriminant (F); 1642 end; 1643 end loop; 1644 1645 -- If the derived type has a stored constraint, assign the value 1646 -- of the corresponding discriminants explicitly, skipping those 1647 -- that are renamed discriminants. We cannot just retrieve them 1648 -- from the Rhs by selected component because they are invisible 1649 -- in the type of the right-hand side. 1650 1651 if Stored_Constraint (R_Typ) /= No_Elist then 1652 declare 1653 Assign : Node_Id; 1654 Discr_Val : Elmt_Id; 1655 1656 begin 1657 Discr_Val := First_Elmt (Stored_Constraint (R_Typ)); 1658 F := First_Entity (R_Typ); 1659 while Present (F) loop 1660 if Ekind (F) = E_Discriminant 1661 and then Is_Completely_Hidden (F) 1662 and then Present (Corresponding_Record_Component (F)) 1663 and then 1664 (not Is_Entity_Name (Node (Discr_Val)) 1665 or else Ekind (Entity (Node (Discr_Val))) /= 1666 E_Discriminant) 1667 then 1668 Assign := 1669 Make_Assignment_Statement (Loc, 1670 Name => 1671 Make_Selected_Component (Loc, 1672 Prefix => Duplicate_Subexpr (Lhs), 1673 Selector_Name => 1674 New_Occurrence_Of 1675 (Corresponding_Record_Component (F), Loc)), 1676 Expression => New_Copy (Node (Discr_Val))); 1677 1678 Set_Assignment_OK (Name (Assign)); 1679 Insert_Action (N, Assign); 1680 Next_Elmt (Discr_Val); 1681 end if; 1682 1683 Next_Entity (F); 1684 end loop; 1685 end; 1686 end if; 1687 end if; 1688 1689 -- We know the underlying type is a record, but its current view 1690 -- may be private. We must retrieve the usable record declaration. 1691 1692 if Nkind_In (Decl, N_Private_Type_Declaration, 1693 N_Private_Extension_Declaration) 1694 and then Present (Full_View (R_Typ)) 1695 then 1696 RDef := Type_Definition (Declaration_Node (Full_View (R_Typ))); 1697 else 1698 RDef := Type_Definition (Decl); 1699 end if; 1700 1701 if Nkind (RDef) = N_Derived_Type_Definition then 1702 RDef := Record_Extension_Part (RDef); 1703 end if; 1704 1705 if Nkind (RDef) = N_Record_Definition 1706 and then Present (Component_List (RDef)) 1707 then 1708 if Is_Unchecked_Union (R_Typ) then 1709 Insert_Actions (N, 1710 Make_Component_List_Assign (Component_List (RDef), True)); 1711 else 1712 Insert_Actions 1713 (N, Make_Component_List_Assign (Component_List (RDef))); 1714 end if; 1715 1716 Rewrite (N, Make_Null_Statement (Loc)); 1717 end if; 1718 end; 1719 end Expand_Assign_Record; 1720 1721 ------------------------------------- 1722 -- Expand_Assign_With_Target_Names -- 1723 ------------------------------------- 1724 1725 procedure Expand_Assign_With_Target_Names (N : Node_Id) is 1726 LHS : constant Node_Id := Name (N); 1727 LHS_Typ : constant Entity_Id := Etype (LHS); 1728 Loc : constant Source_Ptr := Sloc (N); 1729 RHS : constant Node_Id := Expression (N); 1730 1731 Ent : Entity_Id; 1732 -- The entity of the left-hand side 1733 1734 function Replace_Target (N : Node_Id) return Traverse_Result; 1735 -- Replace occurrences of the target name by the proper entity: either 1736 -- the entity of the LHS in simple cases, or the formal of the 1737 -- constructed procedure otherwise. 1738 1739 -------------------- 1740 -- Replace_Target -- 1741 -------------------- 1742 1743 function Replace_Target (N : Node_Id) return Traverse_Result is 1744 begin 1745 if Nkind (N) = N_Target_Name then 1746 Rewrite (N, New_Occurrence_Of (Ent, Sloc (N))); 1747 1748 -- The expression will be reanalyzed when the enclosing assignment 1749 -- is reanalyzed, so reset the entity, which may be a temporary 1750 -- created during analysis, e.g. a loop variable for an iterated 1751 -- component association. However, if entity is callable then 1752 -- resolution has established its proper identity (including in 1753 -- rewritten prefixed calls) so we must preserve it. 1754 1755 elsif Is_Entity_Name (N) then 1756 if Present (Entity (N)) 1757 and then not Is_Overloadable (Entity (N)) 1758 then 1759 Set_Entity (N, Empty); 1760 end if; 1761 end if; 1762 1763 Set_Analyzed (N, False); 1764 return OK; 1765 end Replace_Target; 1766 1767 procedure Replace_Target_Name is new Traverse_Proc (Replace_Target); 1768 1769 -- Local variables 1770 1771 New_RHS : Node_Id; 1772 Proc_Id : Entity_Id; 1773 1774 -- Start of processing for Expand_Assign_With_Target_Names 1775 1776 begin 1777 New_RHS := New_Copy_Tree (RHS); 1778 1779 -- The left-hand side is a direct name 1780 1781 if Is_Entity_Name (LHS) 1782 and then not Is_Renaming_Of_Object (Entity (LHS)) 1783 then 1784 Ent := Entity (LHS); 1785 Replace_Target_Name (New_RHS); 1786 1787 -- Generate: 1788 -- LHS := ... LHS ...; 1789 1790 Rewrite (N, 1791 Make_Assignment_Statement (Loc, 1792 Name => Relocate_Node (LHS), 1793 Expression => New_RHS)); 1794 1795 -- The left-hand side is not a direct name, but is side-effect free. 1796 -- Capture its value in a temporary to avoid multiple evaluations. 1797 1798 elsif Side_Effect_Free (LHS) then 1799 Ent := Make_Temporary (Loc, 'T'); 1800 Replace_Target_Name (New_RHS); 1801 1802 -- Generate: 1803 -- T : LHS_Typ := LHS; 1804 1805 Insert_Before_And_Analyze (N, 1806 Make_Object_Declaration (Loc, 1807 Defining_Identifier => Ent, 1808 Object_Definition => New_Occurrence_Of (LHS_Typ, Loc), 1809 Expression => New_Copy_Tree (LHS))); 1810 1811 -- Generate: 1812 -- LHS := ... T ...; 1813 1814 Rewrite (N, 1815 Make_Assignment_Statement (Loc, 1816 Name => Relocate_Node (LHS), 1817 Expression => New_RHS)); 1818 1819 -- Otherwise wrap the whole assignment statement in a procedure with an 1820 -- IN OUT parameter. The original assignment then becomes a call to the 1821 -- procedure with the left-hand side as an actual. 1822 1823 else 1824 Ent := Make_Temporary (Loc, 'T'); 1825 Replace_Target_Name (New_RHS); 1826 1827 -- Generate: 1828 -- procedure P (T : in out LHS_Typ) is 1829 -- begin 1830 -- T := ... T ...; 1831 -- end P; 1832 1833 Proc_Id := Make_Temporary (Loc, 'P'); 1834 1835 Insert_Before_And_Analyze (N, 1836 Make_Subprogram_Body (Loc, 1837 Specification => 1838 Make_Procedure_Specification (Loc, 1839 Defining_Unit_Name => Proc_Id, 1840 Parameter_Specifications => New_List ( 1841 Make_Parameter_Specification (Loc, 1842 Defining_Identifier => Ent, 1843 In_Present => True, 1844 Out_Present => True, 1845 Parameter_Type => 1846 New_Occurrence_Of (LHS_Typ, Loc)))), 1847 1848 Declarations => Empty_List, 1849 1850 Handled_Statement_Sequence => 1851 Make_Handled_Sequence_Of_Statements (Loc, 1852 Statements => New_List ( 1853 Make_Assignment_Statement (Loc, 1854 Name => New_Occurrence_Of (Ent, Loc), 1855 Expression => New_RHS))))); 1856 1857 -- Generate: 1858 -- P (LHS); 1859 1860 Rewrite (N, 1861 Make_Procedure_Call_Statement (Loc, 1862 Name => New_Occurrence_Of (Proc_Id, Loc), 1863 Parameter_Associations => New_List (Relocate_Node (LHS)))); 1864 end if; 1865 1866 -- Analyze rewritten node, either as assignment or procedure call 1867 1868 Analyze (N); 1869 end Expand_Assign_With_Target_Names; 1870 1871 ----------------------------------- 1872 -- Expand_N_Assignment_Statement -- 1873 ----------------------------------- 1874 1875 -- This procedure implements various cases where an assignment statement 1876 -- cannot just be passed on to the back end in untransformed state. 1877 1878 procedure Expand_N_Assignment_Statement (N : Node_Id) is 1879 Crep : constant Boolean := Change_Of_Representation (N); 1880 Lhs : constant Node_Id := Name (N); 1881 Loc : constant Source_Ptr := Sloc (N); 1882 Rhs : constant Node_Id := Expression (N); 1883 Typ : constant Entity_Id := Underlying_Type (Etype (Lhs)); 1884 Exp : Node_Id; 1885 1886 begin 1887 -- Special case to check right away, if the Componentwise_Assignment 1888 -- flag is set, this is a reanalysis from the expansion of the primitive 1889 -- assignment procedure for a tagged type, and all we need to do is to 1890 -- expand to assignment of components, because otherwise, we would get 1891 -- infinite recursion (since this looks like a tagged assignment which 1892 -- would normally try to *call* the primitive assignment procedure). 1893 1894 if Componentwise_Assignment (N) then 1895 Expand_Assign_Record (N); 1896 return; 1897 end if; 1898 1899 -- Defend against invalid subscripts on left side if we are in standard 1900 -- validity checking mode. No need to do this if we are checking all 1901 -- subscripts. 1902 1903 -- Note that we do this right away, because there are some early return 1904 -- paths in this procedure, and this is required on all paths. 1905 1906 if Validity_Checks_On 1907 and then Validity_Check_Default 1908 and then not Validity_Check_Subscripts 1909 then 1910 Check_Valid_Lvalue_Subscripts (Lhs); 1911 end if; 1912 1913 -- Separate expansion if RHS contain target names. Note that assignment 1914 -- may already have been expanded if RHS is aggregate. 1915 1916 if Nkind (N) = N_Assignment_Statement and then Has_Target_Names (N) then 1917 Expand_Assign_With_Target_Names (N); 1918 return; 1919 end if; 1920 1921 -- Ada 2005 (AI-327): Handle assignment to priority of protected object 1922 1923 -- Rewrite an assignment to X'Priority into a run-time call 1924 1925 -- For example: X'Priority := New_Prio_Expr; 1926 -- ...is expanded into Set_Ceiling (X._Object, New_Prio_Expr); 1927 1928 -- Note that although X'Priority is notionally an object, it is quite 1929 -- deliberately not defined as an aliased object in the RM. This means 1930 -- that it works fine to rewrite it as a call, without having to worry 1931 -- about complications that would other arise from X'Priority'Access, 1932 -- which is illegal, because of the lack of aliasing. 1933 1934 if Ada_Version >= Ada_2005 then 1935 declare 1936 Call : Node_Id; 1937 Conctyp : Entity_Id; 1938 Ent : Entity_Id; 1939 Subprg : Entity_Id; 1940 RT_Subprg_Name : Node_Id; 1941 1942 begin 1943 -- Handle chains of renamings 1944 1945 Ent := Name (N); 1946 while Nkind (Ent) in N_Has_Entity 1947 and then Present (Entity (Ent)) 1948 and then Present (Renamed_Object (Entity (Ent))) 1949 loop 1950 Ent := Renamed_Object (Entity (Ent)); 1951 end loop; 1952 1953 -- The attribute Priority applied to protected objects has been 1954 -- previously expanded into a call to the Get_Ceiling run-time 1955 -- subprogram. In restricted profiles this is not available. 1956 1957 if Is_Expanded_Priority_Attribute (Ent) then 1958 1959 -- Look for the enclosing concurrent type 1960 1961 Conctyp := Current_Scope; 1962 while not Is_Concurrent_Type (Conctyp) loop 1963 Conctyp := Scope (Conctyp); 1964 end loop; 1965 1966 pragma Assert (Is_Protected_Type (Conctyp)); 1967 1968 -- Generate the first actual of the call 1969 1970 Subprg := Current_Scope; 1971 while not Present (Protected_Body_Subprogram (Subprg)) loop 1972 Subprg := Scope (Subprg); 1973 end loop; 1974 1975 -- Select the appropriate run-time call 1976 1977 if Number_Entries (Conctyp) = 0 then 1978 RT_Subprg_Name := 1979 New_Occurrence_Of (RTE (RE_Set_Ceiling), Loc); 1980 else 1981 RT_Subprg_Name := 1982 New_Occurrence_Of (RTE (RO_PE_Set_Ceiling), Loc); 1983 end if; 1984 1985 Call := 1986 Make_Procedure_Call_Statement (Loc, 1987 Name => RT_Subprg_Name, 1988 Parameter_Associations => New_List ( 1989 New_Copy_Tree (First (Parameter_Associations (Ent))), 1990 Relocate_Node (Expression (N)))); 1991 1992 Rewrite (N, Call); 1993 Analyze (N); 1994 1995 return; 1996 end if; 1997 end; 1998 end if; 1999 2000 -- Deal with assignment checks unless suppressed 2001 2002 if not Suppress_Assignment_Checks (N) then 2003 2004 -- First deal with generation of range check if required 2005 2006 if Do_Range_Check (Rhs) then 2007 Generate_Range_Check (Rhs, Typ, CE_Range_Check_Failed); 2008 end if; 2009 2010 -- Then generate predicate check if required 2011 2012 Apply_Predicate_Check (Rhs, Typ); 2013 end if; 2014 2015 -- Check for a special case where a high level transformation is 2016 -- required. If we have either of: 2017 2018 -- P.field := rhs; 2019 -- P (sub) := rhs; 2020 2021 -- where P is a reference to a bit packed array, then we have to unwind 2022 -- the assignment. The exact meaning of being a reference to a bit 2023 -- packed array is as follows: 2024 2025 -- An indexed component whose prefix is a bit packed array is a 2026 -- reference to a bit packed array. 2027 2028 -- An indexed component or selected component whose prefix is a 2029 -- reference to a bit packed array is itself a reference ot a 2030 -- bit packed array. 2031 2032 -- The required transformation is 2033 2034 -- Tnn : prefix_type := P; 2035 -- Tnn.field := rhs; 2036 -- P := Tnn; 2037 2038 -- or 2039 2040 -- Tnn : prefix_type := P; 2041 -- Tnn (subscr) := rhs; 2042 -- P := Tnn; 2043 2044 -- Since P is going to be evaluated more than once, any subscripts 2045 -- in P must have their evaluation forced. 2046 2047 if Nkind_In (Lhs, N_Indexed_Component, N_Selected_Component) 2048 and then Is_Ref_To_Bit_Packed_Array (Prefix (Lhs)) 2049 then 2050 declare 2051 BPAR_Expr : constant Node_Id := Relocate_Node (Prefix (Lhs)); 2052 BPAR_Typ : constant Entity_Id := Etype (BPAR_Expr); 2053 Tnn : constant Entity_Id := 2054 Make_Temporary (Loc, 'T', BPAR_Expr); 2055 2056 begin 2057 -- Insert the post assignment first, because we want to copy the 2058 -- BPAR_Expr tree before it gets analyzed in the context of the 2059 -- pre assignment. Note that we do not analyze the post assignment 2060 -- yet (we cannot till we have completed the analysis of the pre 2061 -- assignment). As usual, the analysis of this post assignment 2062 -- will happen on its own when we "run into" it after finishing 2063 -- the current assignment. 2064 2065 Insert_After (N, 2066 Make_Assignment_Statement (Loc, 2067 Name => New_Copy_Tree (BPAR_Expr), 2068 Expression => New_Occurrence_Of (Tnn, Loc))); 2069 2070 -- At this stage BPAR_Expr is a reference to a bit packed array 2071 -- where the reference was not expanded in the original tree, 2072 -- since it was on the left side of an assignment. But in the 2073 -- pre-assignment statement (the object definition), BPAR_Expr 2074 -- will end up on the right-hand side, and must be reexpanded. To 2075 -- achieve this, we reset the analyzed flag of all selected and 2076 -- indexed components down to the actual indexed component for 2077 -- the packed array. 2078 2079 Exp := BPAR_Expr; 2080 loop 2081 Set_Analyzed (Exp, False); 2082 2083 if Nkind_In (Exp, N_Indexed_Component, 2084 N_Selected_Component) 2085 then 2086 Exp := Prefix (Exp); 2087 else 2088 exit; 2089 end if; 2090 end loop; 2091 2092 -- Now we can insert and analyze the pre-assignment 2093 2094 -- If the right-hand side requires a transient scope, it has 2095 -- already been placed on the stack. However, the declaration is 2096 -- inserted in the tree outside of this scope, and must reflect 2097 -- the proper scope for its variable. This awkward bit is forced 2098 -- by the stricter scope discipline imposed by GCC 2.97. 2099 2100 declare 2101 Uses_Transient_Scope : constant Boolean := 2102 Scope_Is_Transient 2103 and then N = Node_To_Be_Wrapped; 2104 2105 begin 2106 if Uses_Transient_Scope then 2107 Push_Scope (Scope (Current_Scope)); 2108 end if; 2109 2110 Insert_Before_And_Analyze (N, 2111 Make_Object_Declaration (Loc, 2112 Defining_Identifier => Tnn, 2113 Object_Definition => New_Occurrence_Of (BPAR_Typ, Loc), 2114 Expression => BPAR_Expr)); 2115 2116 if Uses_Transient_Scope then 2117 Pop_Scope; 2118 end if; 2119 end; 2120 2121 -- Now fix up the original assignment and continue processing 2122 2123 Rewrite (Prefix (Lhs), 2124 New_Occurrence_Of (Tnn, Loc)); 2125 2126 -- We do not need to reanalyze that assignment, and we do not need 2127 -- to worry about references to the temporary, but we do need to 2128 -- make sure that the temporary is not marked as a true constant 2129 -- since we now have a generated assignment to it. 2130 2131 Set_Is_True_Constant (Tnn, False); 2132 end; 2133 end if; 2134 2135 -- When we have the appropriate type of aggregate in the expression (it 2136 -- has been determined during analysis of the aggregate by setting the 2137 -- delay flag), let's perform in place assignment and thus avoid 2138 -- creating a temporary. 2139 2140 if Is_Delayed_Aggregate (Rhs) then 2141 Convert_Aggr_In_Assignment (N); 2142 Rewrite (N, Make_Null_Statement (Loc)); 2143 Analyze (N); 2144 2145 return; 2146 end if; 2147 2148 -- Apply discriminant check if required. If Lhs is an access type to a 2149 -- designated type with discriminants, we must always check. If the 2150 -- type has unknown discriminants, more elaborate processing below. 2151 2152 if Has_Discriminants (Etype (Lhs)) 2153 and then not Has_Unknown_Discriminants (Etype (Lhs)) 2154 then 2155 -- Skip discriminant check if change of representation. Will be 2156 -- done when the change of representation is expanded out. 2157 2158 if not Crep then 2159 Apply_Discriminant_Check (Rhs, Etype (Lhs), Lhs); 2160 end if; 2161 2162 -- If the type is private without discriminants, and the full type 2163 -- has discriminants (necessarily with defaults) a check may still be 2164 -- necessary if the Lhs is aliased. The private discriminants must be 2165 -- visible to build the discriminant constraints. 2166 2167 -- Only an explicit dereference that comes from source indicates 2168 -- aliasing. Access to formals of protected operations and entries 2169 -- create dereferences but are not semantic aliasings. 2170 2171 elsif Is_Private_Type (Etype (Lhs)) 2172 and then Has_Discriminants (Typ) 2173 and then Nkind (Lhs) = N_Explicit_Dereference 2174 and then Comes_From_Source (Lhs) 2175 then 2176 declare 2177 Lt : constant Entity_Id := Etype (Lhs); 2178 Ubt : Entity_Id := Base_Type (Typ); 2179 2180 begin 2181 -- In the case of an expander-generated record subtype whose base 2182 -- type still appears private, Typ will have been set to that 2183 -- private type rather than the underlying record type (because 2184 -- Underlying type will have returned the record subtype), so it's 2185 -- necessary to apply Underlying_Type again to the base type to 2186 -- get the record type we need for the discriminant check. Such 2187 -- subtypes can be created for assignments in certain cases, such 2188 -- as within an instantiation passed this kind of private type. 2189 -- It would be good to avoid this special test, but making changes 2190 -- to prevent this odd form of record subtype seems difficult. ??? 2191 2192 if Is_Private_Type (Ubt) then 2193 Ubt := Underlying_Type (Ubt); 2194 end if; 2195 2196 Set_Etype (Lhs, Ubt); 2197 Rewrite (Rhs, OK_Convert_To (Base_Type (Ubt), Rhs)); 2198 Apply_Discriminant_Check (Rhs, Ubt, Lhs); 2199 Set_Etype (Lhs, Lt); 2200 end; 2201 2202 -- If the Lhs has a private type with unknown discriminants, it may 2203 -- have a full view with discriminants, but those are nameable only 2204 -- in the underlying type, so convert the Rhs to it before potential 2205 -- checking. Convert Lhs as well, otherwise the actual subtype might 2206 -- not be constructible. If the discriminants have defaults the type 2207 -- is unconstrained and there is nothing to check. 2208 2209 elsif Has_Unknown_Discriminants (Base_Type (Etype (Lhs))) 2210 and then Has_Discriminants (Typ) 2211 and then not Has_Defaulted_Discriminants (Typ) 2212 then 2213 Rewrite (Rhs, OK_Convert_To (Base_Type (Typ), Rhs)); 2214 Rewrite (Lhs, OK_Convert_To (Base_Type (Typ), Lhs)); 2215 Apply_Discriminant_Check (Rhs, Typ, Lhs); 2216 2217 -- In the access type case, we need the same discriminant check, and 2218 -- also range checks if we have an access to constrained array. 2219 2220 elsif Is_Access_Type (Etype (Lhs)) 2221 and then Is_Constrained (Designated_Type (Etype (Lhs))) 2222 then 2223 if Has_Discriminants (Designated_Type (Etype (Lhs))) then 2224 2225 -- Skip discriminant check if change of representation. Will be 2226 -- done when the change of representation is expanded out. 2227 2228 if not Crep then 2229 Apply_Discriminant_Check (Rhs, Etype (Lhs)); 2230 end if; 2231 2232 elsif Is_Array_Type (Designated_Type (Etype (Lhs))) then 2233 Apply_Range_Check (Rhs, Etype (Lhs)); 2234 2235 if Is_Constrained (Etype (Lhs)) then 2236 Apply_Length_Check (Rhs, Etype (Lhs)); 2237 end if; 2238 2239 if Nkind (Rhs) = N_Allocator then 2240 declare 2241 Target_Typ : constant Entity_Id := Etype (Expression (Rhs)); 2242 C_Es : Check_Result; 2243 2244 begin 2245 C_Es := 2246 Get_Range_Checks 2247 (Lhs, 2248 Target_Typ, 2249 Etype (Designated_Type (Etype (Lhs)))); 2250 2251 Insert_Range_Checks 2252 (C_Es, 2253 N, 2254 Target_Typ, 2255 Sloc (Lhs), 2256 Lhs); 2257 end; 2258 end if; 2259 end if; 2260 2261 -- Apply range check for access type case 2262 2263 elsif Is_Access_Type (Etype (Lhs)) 2264 and then Nkind (Rhs) = N_Allocator 2265 and then Nkind (Expression (Rhs)) = N_Qualified_Expression 2266 then 2267 Analyze_And_Resolve (Expression (Rhs)); 2268 Apply_Range_Check 2269 (Expression (Rhs), Designated_Type (Etype (Lhs))); 2270 end if; 2271 2272 -- Ada 2005 (AI-231): Generate the run-time check 2273 2274 if Is_Access_Type (Typ) 2275 and then Can_Never_Be_Null (Etype (Lhs)) 2276 and then not Can_Never_Be_Null (Etype (Rhs)) 2277 2278 -- If an actual is an out parameter of a null-excluding access 2279 -- type, there is access check on entry, so we set the flag 2280 -- Suppress_Assignment_Checks on the generated statement to 2281 -- assign the actual to the parameter block, and we do not want 2282 -- to generate an additional check at this point. 2283 2284 and then not Suppress_Assignment_Checks (N) 2285 then 2286 Apply_Constraint_Check (Rhs, Etype (Lhs)); 2287 end if; 2288 2289 -- Ada 2012 (AI05-148): Update current accessibility level if Rhs is a 2290 -- stand-alone obj of an anonymous access type. Do not install the check 2291 -- when the Lhs denotes a container cursor and the Next function employs 2292 -- an access type, because this can never result in a dangling pointer. 2293 2294 if Is_Access_Type (Typ) 2295 and then Is_Entity_Name (Lhs) 2296 and then Ekind (Entity (Lhs)) /= E_Loop_Parameter 2297 and then Present (Effective_Extra_Accessibility (Entity (Lhs))) 2298 then 2299 declare 2300 function Lhs_Entity return Entity_Id; 2301 -- Look through renames to find the underlying entity. 2302 -- For assignment to a rename, we don't care about the 2303 -- Enclosing_Dynamic_Scope of the rename declaration. 2304 2305 ---------------- 2306 -- Lhs_Entity -- 2307 ---------------- 2308 2309 function Lhs_Entity return Entity_Id is 2310 Result : Entity_Id := Entity (Lhs); 2311 2312 begin 2313 while Present (Renamed_Object (Result)) loop 2314 2315 -- Renamed_Object must return an Entity_Name here 2316 -- because of preceding "Present (E_E_A (...))" test. 2317 2318 Result := Entity (Renamed_Object (Result)); 2319 end loop; 2320 2321 return Result; 2322 end Lhs_Entity; 2323 2324 -- Local Declarations 2325 2326 Access_Check : constant Node_Id := 2327 Make_Raise_Program_Error (Loc, 2328 Condition => 2329 Make_Op_Gt (Loc, 2330 Left_Opnd => 2331 Dynamic_Accessibility_Level (Rhs), 2332 Right_Opnd => 2333 Make_Integer_Literal (Loc, 2334 Intval => 2335 Scope_Depth 2336 (Enclosing_Dynamic_Scope 2337 (Lhs_Entity)))), 2338 Reason => PE_Accessibility_Check_Failed); 2339 2340 Access_Level_Update : constant Node_Id := 2341 Make_Assignment_Statement (Loc, 2342 Name => 2343 New_Occurrence_Of 2344 (Effective_Extra_Accessibility 2345 (Entity (Lhs)), Loc), 2346 Expression => 2347 Dynamic_Accessibility_Level (Rhs)); 2348 2349 begin 2350 if not Accessibility_Checks_Suppressed (Entity (Lhs)) then 2351 Insert_Action (N, Access_Check); 2352 end if; 2353 2354 Insert_Action (N, Access_Level_Update); 2355 end; 2356 end if; 2357 2358 -- Case of assignment to a bit packed array element. If there is a 2359 -- change of representation this must be expanded into components, 2360 -- otherwise this is a bit-field assignment. 2361 2362 if Nkind (Lhs) = N_Indexed_Component 2363 and then Is_Bit_Packed_Array (Etype (Prefix (Lhs))) 2364 then 2365 -- Normal case, no change of representation 2366 2367 if not Crep then 2368 Expand_Bit_Packed_Element_Set (N); 2369 return; 2370 2371 -- Change of representation case 2372 2373 else 2374 -- Generate the following, to force component-by-component 2375 -- assignments in an efficient way. Otherwise each component 2376 -- will require a temporary and two bit-field manipulations. 2377 2378 -- T1 : Elmt_Type; 2379 -- T1 := RhS; 2380 -- Lhs := T1; 2381 2382 declare 2383 Tnn : constant Entity_Id := Make_Temporary (Loc, 'T'); 2384 Stats : List_Id; 2385 2386 begin 2387 Stats := 2388 New_List ( 2389 Make_Object_Declaration (Loc, 2390 Defining_Identifier => Tnn, 2391 Object_Definition => 2392 New_Occurrence_Of (Etype (Lhs), Loc)), 2393 Make_Assignment_Statement (Loc, 2394 Name => New_Occurrence_Of (Tnn, Loc), 2395 Expression => Relocate_Node (Rhs)), 2396 Make_Assignment_Statement (Loc, 2397 Name => Relocate_Node (Lhs), 2398 Expression => New_Occurrence_Of (Tnn, Loc))); 2399 2400 Insert_Actions (N, Stats); 2401 Rewrite (N, Make_Null_Statement (Loc)); 2402 Analyze (N); 2403 end; 2404 end if; 2405 2406 -- Build-in-place function call case. This is for assignment statements 2407 -- that come from aggregate component associations or from init procs. 2408 -- User-written assignment statements with b-i-p calls are handled 2409 -- elsewhere. 2410 2411 elsif Is_Build_In_Place_Function_Call (Rhs) then 2412 pragma Assert (not Comes_From_Source (N)); 2413 Make_Build_In_Place_Call_In_Assignment (N, Rhs); 2414 2415 elsif Is_Tagged_Type (Typ) 2416 or else (Needs_Finalization (Typ) and then not Is_Array_Type (Typ)) 2417 then 2418 Tagged_Case : declare 2419 L : List_Id := No_List; 2420 Expand_Ctrl_Actions : constant Boolean := not No_Ctrl_Actions (N); 2421 2422 begin 2423 -- In the controlled case, we ensure that function calls are 2424 -- evaluated before finalizing the target. In all cases, it makes 2425 -- the expansion easier if the side effects are removed first. 2426 2427 Remove_Side_Effects (Lhs); 2428 Remove_Side_Effects (Rhs); 2429 2430 -- Avoid recursion in the mechanism 2431 2432 Set_Analyzed (N); 2433 2434 -- If dispatching assignment, we need to dispatch to _assign 2435 2436 if Is_Class_Wide_Type (Typ) 2437 2438 -- If the type is tagged, we may as well use the predefined 2439 -- primitive assignment. This avoids inlining a lot of code 2440 -- and in the class-wide case, the assignment is replaced 2441 -- by a dispatching call to _assign. It is suppressed in the 2442 -- case of assignments created by the expander that correspond 2443 -- to initializations, where we do want to copy the tag 2444 -- (Expand_Ctrl_Actions flag is set False in this case). It is 2445 -- also suppressed if restriction No_Dispatching_Calls is in 2446 -- force because in that case predefined primitives are not 2447 -- generated. 2448 2449 or else (Is_Tagged_Type (Typ) 2450 and then Chars (Current_Scope) /= Name_uAssign 2451 and then Expand_Ctrl_Actions 2452 and then 2453 not Restriction_Active (No_Dispatching_Calls)) 2454 then 2455 if Is_Limited_Type (Typ) then 2456 2457 -- This can happen in an instance when the formal is an 2458 -- extension of a limited interface, and the actual is 2459 -- limited. This is an error according to AI05-0087, but 2460 -- is not caught at the point of instantiation in earlier 2461 -- versions. 2462 2463 -- This is wrong, error messages cannot be issued during 2464 -- expansion, since they would be missed in -gnatc mode ??? 2465 2466 Error_Msg_N ("assignment not available on limited type", N); 2467 return; 2468 end if; 2469 2470 -- Fetch the primitive op _assign and proper type to call it. 2471 -- Because of possible conflicts between private and full view, 2472 -- fetch the proper type directly from the operation profile. 2473 2474 declare 2475 Op : constant Entity_Id := 2476 Find_Prim_Op (Typ, Name_uAssign); 2477 F_Typ : Entity_Id := Etype (First_Formal (Op)); 2478 2479 begin 2480 -- If the assignment is dispatching, make sure to use the 2481 -- proper type. 2482 2483 if Is_Class_Wide_Type (Typ) then 2484 F_Typ := Class_Wide_Type (F_Typ); 2485 end if; 2486 2487 L := New_List; 2488 2489 -- In case of assignment to a class-wide tagged type, before 2490 -- the assignment we generate run-time check to ensure that 2491 -- the tags of source and target match. 2492 2493 if not Tag_Checks_Suppressed (Typ) 2494 and then Is_Class_Wide_Type (Typ) 2495 and then Is_Tagged_Type (Typ) 2496 and then Is_Tagged_Type (Underlying_Type (Etype (Rhs))) 2497 then 2498 declare 2499 Lhs_Tag : Node_Id; 2500 Rhs_Tag : Node_Id; 2501 2502 begin 2503 if not Is_Interface (Typ) then 2504 Lhs_Tag := 2505 Make_Selected_Component (Loc, 2506 Prefix => Duplicate_Subexpr (Lhs), 2507 Selector_Name => 2508 Make_Identifier (Loc, Name_uTag)); 2509 Rhs_Tag := 2510 Make_Selected_Component (Loc, 2511 Prefix => Duplicate_Subexpr (Rhs), 2512 Selector_Name => 2513 Make_Identifier (Loc, Name_uTag)); 2514 else 2515 -- Displace the pointer to the base of the objects 2516 -- applying 'Address, which is later expanded into 2517 -- a call to RE_Base_Address. 2518 2519 Lhs_Tag := 2520 Make_Explicit_Dereference (Loc, 2521 Prefix => 2522 Unchecked_Convert_To (RTE (RE_Tag_Ptr), 2523 Make_Attribute_Reference (Loc, 2524 Prefix => Duplicate_Subexpr (Lhs), 2525 Attribute_Name => Name_Address))); 2526 Rhs_Tag := 2527 Make_Explicit_Dereference (Loc, 2528 Prefix => 2529 Unchecked_Convert_To (RTE (RE_Tag_Ptr), 2530 Make_Attribute_Reference (Loc, 2531 Prefix => Duplicate_Subexpr (Rhs), 2532 Attribute_Name => Name_Address))); 2533 end if; 2534 2535 Append_To (L, 2536 Make_Raise_Constraint_Error (Loc, 2537 Condition => 2538 Make_Op_Ne (Loc, 2539 Left_Opnd => Lhs_Tag, 2540 Right_Opnd => Rhs_Tag), 2541 Reason => CE_Tag_Check_Failed)); 2542 end; 2543 end if; 2544 2545 declare 2546 Left_N : Node_Id := Duplicate_Subexpr (Lhs); 2547 Right_N : Node_Id := Duplicate_Subexpr (Rhs); 2548 2549 begin 2550 -- In order to dispatch the call to _assign the type of 2551 -- the actuals must match. Add conversion (if required). 2552 2553 if Etype (Lhs) /= F_Typ then 2554 Left_N := Unchecked_Convert_To (F_Typ, Left_N); 2555 end if; 2556 2557 if Etype (Rhs) /= F_Typ then 2558 Right_N := Unchecked_Convert_To (F_Typ, Right_N); 2559 end if; 2560 2561 Append_To (L, 2562 Make_Procedure_Call_Statement (Loc, 2563 Name => New_Occurrence_Of (Op, Loc), 2564 Parameter_Associations => New_List ( 2565 Node1 => Left_N, 2566 Node2 => Right_N))); 2567 end; 2568 end; 2569 2570 else 2571 L := Make_Tag_Ctrl_Assignment (N); 2572 2573 -- We can't afford to have destructive Finalization Actions in 2574 -- the Self assignment case, so if the target and the source 2575 -- are not obviously different, code is generated to avoid the 2576 -- self assignment case: 2577 2578 -- if lhs'address /= rhs'address then 2579 -- <code for controlled and/or tagged assignment> 2580 -- end if; 2581 2582 -- Skip this if Restriction (No_Finalization) is active 2583 2584 if not Statically_Different (Lhs, Rhs) 2585 and then Expand_Ctrl_Actions 2586 and then not Restriction_Active (No_Finalization) 2587 then 2588 L := New_List ( 2589 Make_Implicit_If_Statement (N, 2590 Condition => 2591 Make_Op_Ne (Loc, 2592 Left_Opnd => 2593 Make_Attribute_Reference (Loc, 2594 Prefix => Duplicate_Subexpr (Lhs), 2595 Attribute_Name => Name_Address), 2596 2597 Right_Opnd => 2598 Make_Attribute_Reference (Loc, 2599 Prefix => Duplicate_Subexpr (Rhs), 2600 Attribute_Name => Name_Address)), 2601 2602 Then_Statements => L)); 2603 end if; 2604 2605 -- We need to set up an exception handler for implementing 2606 -- 7.6.1(18). The remaining adjustments are tackled by the 2607 -- implementation of adjust for record_controllers (see 2608 -- s-finimp.adb). 2609 2610 -- This is skipped if we have no finalization 2611 2612 if Expand_Ctrl_Actions 2613 and then not Restriction_Active (No_Finalization) 2614 then 2615 L := New_List ( 2616 Make_Block_Statement (Loc, 2617 Handled_Statement_Sequence => 2618 Make_Handled_Sequence_Of_Statements (Loc, 2619 Statements => L, 2620 Exception_Handlers => New_List ( 2621 Make_Handler_For_Ctrl_Operation (Loc))))); 2622 end if; 2623 end if; 2624 2625 Rewrite (N, 2626 Make_Block_Statement (Loc, 2627 Handled_Statement_Sequence => 2628 Make_Handled_Sequence_Of_Statements (Loc, Statements => L))); 2629 2630 -- If no restrictions on aborts, protect the whole assignment 2631 -- for controlled objects as per 9.8(11). 2632 2633 if Needs_Finalization (Typ) 2634 and then Expand_Ctrl_Actions 2635 and then Abort_Allowed 2636 then 2637 declare 2638 Blk : constant Entity_Id := 2639 New_Internal_Entity 2640 (E_Block, Current_Scope, Sloc (N), 'B'); 2641 AUD : constant Entity_Id := RTE (RE_Abort_Undefer_Direct); 2642 2643 begin 2644 Set_Is_Abort_Block (N); 2645 2646 Set_Scope (Blk, Current_Scope); 2647 Set_Etype (Blk, Standard_Void_Type); 2648 Set_Identifier (N, New_Occurrence_Of (Blk, Sloc (N))); 2649 2650 Prepend_To (L, Build_Runtime_Call (Loc, RE_Abort_Defer)); 2651 Set_At_End_Proc (Handled_Statement_Sequence (N), 2652 New_Occurrence_Of (AUD, Loc)); 2653 2654 -- Present the Abort_Undefer_Direct function to the backend 2655 -- so that it can inline the call to the function. 2656 2657 Add_Inlined_Body (AUD, N); 2658 2659 Expand_At_End_Handler 2660 (Handled_Statement_Sequence (N), Blk); 2661 end; 2662 end if; 2663 2664 -- N has been rewritten to a block statement for which it is 2665 -- known by construction that no checks are necessary: analyze 2666 -- it with all checks suppressed. 2667 2668 Analyze (N, Suppress => All_Checks); 2669 return; 2670 end Tagged_Case; 2671 2672 -- Array types 2673 2674 elsif Is_Array_Type (Typ) then 2675 declare 2676 Actual_Rhs : Node_Id := Rhs; 2677 2678 begin 2679 while Nkind_In (Actual_Rhs, N_Type_Conversion, 2680 N_Qualified_Expression) 2681 loop 2682 Actual_Rhs := Expression (Actual_Rhs); 2683 end loop; 2684 2685 Expand_Assign_Array (N, Actual_Rhs); 2686 return; 2687 end; 2688 2689 -- Record types 2690 2691 elsif Is_Record_Type (Typ) then 2692 Expand_Assign_Record (N); 2693 return; 2694 2695 -- Scalar types. This is where we perform the processing related to the 2696 -- requirements of (RM 13.9.1(9-11)) concerning the handling of invalid 2697 -- scalar values. 2698 2699 elsif Is_Scalar_Type (Typ) then 2700 2701 -- Case where right side is known valid 2702 2703 if Expr_Known_Valid (Rhs) then 2704 2705 -- Here the right side is valid, so it is fine. The case to deal 2706 -- with is when the left side is a local variable reference whose 2707 -- value is not currently known to be valid. If this is the case, 2708 -- and the assignment appears in an unconditional context, then 2709 -- we can mark the left side as now being valid if one of these 2710 -- conditions holds: 2711 2712 -- The expression of the right side has Do_Range_Check set so 2713 -- that we know a range check will be performed. Note that it 2714 -- can be the case that a range check is omitted because we 2715 -- make the assumption that we can assume validity for operands 2716 -- appearing in the right side in determining whether a range 2717 -- check is required 2718 2719 -- The subtype of the right side matches the subtype of the 2720 -- left side. In this case, even though we have not checked 2721 -- the range of the right side, we know it is in range of its 2722 -- subtype if the expression is valid. 2723 2724 if Is_Local_Variable_Reference (Lhs) 2725 and then not Is_Known_Valid (Entity (Lhs)) 2726 and then In_Unconditional_Context (N) 2727 then 2728 if Do_Range_Check (Rhs) 2729 or else Etype (Lhs) = Etype (Rhs) 2730 then 2731 Set_Is_Known_Valid (Entity (Lhs), True); 2732 end if; 2733 end if; 2734 2735 -- Case where right side may be invalid in the sense of the RM 2736 -- reference above. The RM does not require that we check for the 2737 -- validity on an assignment, but it does require that the assignment 2738 -- of an invalid value not cause erroneous behavior. 2739 2740 -- The general approach in GNAT is to use the Is_Known_Valid flag 2741 -- to avoid the need for validity checking on assignments. However 2742 -- in some cases, we have to do validity checking in order to make 2743 -- sure that the setting of this flag is correct. 2744 2745 else 2746 -- Validate right side if we are validating copies 2747 2748 if Validity_Checks_On 2749 and then Validity_Check_Copies 2750 then 2751 -- Skip this if left-hand side is an array or record component 2752 -- and elementary component validity checks are suppressed. 2753 2754 if Nkind_In (Lhs, N_Selected_Component, N_Indexed_Component) 2755 and then not Validity_Check_Components 2756 then 2757 null; 2758 else 2759 Ensure_Valid (Rhs); 2760 end if; 2761 2762 -- We can propagate this to the left side where appropriate 2763 2764 if Is_Local_Variable_Reference (Lhs) 2765 and then not Is_Known_Valid (Entity (Lhs)) 2766 and then In_Unconditional_Context (N) 2767 then 2768 Set_Is_Known_Valid (Entity (Lhs), True); 2769 end if; 2770 2771 -- Otherwise check to see what should be done 2772 2773 -- If left side is a local variable, then we just set its flag to 2774 -- indicate that its value may no longer be valid, since we are 2775 -- copying a potentially invalid value. 2776 2777 elsif Is_Local_Variable_Reference (Lhs) then 2778 Set_Is_Known_Valid (Entity (Lhs), False); 2779 2780 -- Check for case of a nonlocal variable on the left side which 2781 -- is currently known to be valid. In this case, we simply ensure 2782 -- that the right side is valid. We only play the game of copying 2783 -- validity status for local variables, since we are doing this 2784 -- statically, not by tracing the full flow graph. 2785 2786 elsif Is_Entity_Name (Lhs) 2787 and then Is_Known_Valid (Entity (Lhs)) 2788 then 2789 -- Note: If Validity_Checking mode is set to none, we ignore 2790 -- the Ensure_Valid call so don't worry about that case here. 2791 2792 Ensure_Valid (Rhs); 2793 2794 -- In all other cases, we can safely copy an invalid value without 2795 -- worrying about the status of the left side. Since it is not a 2796 -- variable reference it will not be considered 2797 -- as being known to be valid in any case. 2798 2799 else 2800 null; 2801 end if; 2802 end if; 2803 end if; 2804 2805 exception 2806 when RE_Not_Available => 2807 return; 2808 end Expand_N_Assignment_Statement; 2809 2810 ------------------------------ 2811 -- Expand_N_Block_Statement -- 2812 ------------------------------ 2813 2814 -- Encode entity names defined in block statement 2815 2816 procedure Expand_N_Block_Statement (N : Node_Id) is 2817 begin 2818 Qualify_Entity_Names (N); 2819 end Expand_N_Block_Statement; 2820 2821 ----------------------------- 2822 -- Expand_N_Case_Statement -- 2823 ----------------------------- 2824 2825 procedure Expand_N_Case_Statement (N : Node_Id) is 2826 Loc : constant Source_Ptr := Sloc (N); 2827 Expr : constant Node_Id := Expression (N); 2828 Alt : Node_Id; 2829 Len : Nat; 2830 Cond : Node_Id; 2831 Choice : Node_Id; 2832 Chlist : List_Id; 2833 2834 begin 2835 -- Check for the situation where we know at compile time which branch 2836 -- will be taken. 2837 2838 -- If the value is static but its subtype is predicated and the value 2839 -- does not obey the predicate, the value is marked non-static, and 2840 -- there can be no corresponding static alternative. In that case we 2841 -- replace the case statement with an exception, regardless of whether 2842 -- assertions are enabled or not, unless predicates are ignored. 2843 2844 if Compile_Time_Known_Value (Expr) 2845 and then Has_Predicates (Etype (Expr)) 2846 and then not Predicates_Ignored (Etype (Expr)) 2847 and then not Is_OK_Static_Expression (Expr) 2848 then 2849 Rewrite (N, 2850 Make_Raise_Constraint_Error (Loc, Reason => CE_Invalid_Data)); 2851 Analyze (N); 2852 return; 2853 2854 elsif Compile_Time_Known_Value (Expr) 2855 and then (not Has_Predicates (Etype (Expr)) 2856 or else Is_Static_Expression (Expr)) 2857 then 2858 Alt := Find_Static_Alternative (N); 2859 2860 -- Do not consider controlled objects found in a case statement which 2861 -- actually models a case expression because their early finalization 2862 -- will affect the result of the expression. 2863 2864 if not From_Conditional_Expression (N) then 2865 Process_Statements_For_Controlled_Objects (Alt); 2866 end if; 2867 2868 -- Move statements from this alternative after the case statement. 2869 -- They are already analyzed, so will be skipped by the analyzer. 2870 2871 Insert_List_After (N, Statements (Alt)); 2872 2873 -- That leaves the case statement as a shell. So now we can kill all 2874 -- other alternatives in the case statement. 2875 2876 Kill_Dead_Code (Expression (N)); 2877 2878 declare 2879 Dead_Alt : Node_Id; 2880 2881 begin 2882 -- Loop through case alternatives, skipping pragmas, and skipping 2883 -- the one alternative that we select (and therefore retain). 2884 2885 Dead_Alt := First (Alternatives (N)); 2886 while Present (Dead_Alt) loop 2887 if Dead_Alt /= Alt 2888 and then Nkind (Dead_Alt) = N_Case_Statement_Alternative 2889 then 2890 Kill_Dead_Code (Statements (Dead_Alt), Warn_On_Deleted_Code); 2891 end if; 2892 2893 Next (Dead_Alt); 2894 end loop; 2895 end; 2896 2897 Rewrite (N, Make_Null_Statement (Loc)); 2898 return; 2899 end if; 2900 2901 -- Here if the choice is not determined at compile time 2902 2903 declare 2904 Last_Alt : constant Node_Id := Last (Alternatives (N)); 2905 2906 Others_Present : Boolean; 2907 Others_Node : Node_Id; 2908 2909 Then_Stms : List_Id; 2910 Else_Stms : List_Id; 2911 2912 begin 2913 if Nkind (First (Discrete_Choices (Last_Alt))) = N_Others_Choice then 2914 Others_Present := True; 2915 Others_Node := Last_Alt; 2916 else 2917 Others_Present := False; 2918 end if; 2919 2920 -- First step is to worry about possible invalid argument. The RM 2921 -- requires (RM 5.4(13)) that if the result is invalid (e.g. it is 2922 -- outside the base range), then Constraint_Error must be raised. 2923 2924 -- Case of validity check required (validity checks are on, the 2925 -- expression is not known to be valid, and the case statement 2926 -- comes from source -- no need to validity check internally 2927 -- generated case statements). 2928 2929 if Validity_Check_Default 2930 and then not Predicates_Ignored (Etype (Expr)) 2931 then 2932 Ensure_Valid (Expr); 2933 end if; 2934 2935 -- If there is only a single alternative, just replace it with the 2936 -- sequence of statements since obviously that is what is going to 2937 -- be executed in all cases. 2938 2939 Len := List_Length (Alternatives (N)); 2940 2941 if Len = 1 then 2942 2943 -- We still need to evaluate the expression if it has any side 2944 -- effects. 2945 2946 Remove_Side_Effects (Expression (N)); 2947 Alt := First (Alternatives (N)); 2948 2949 -- Do not consider controlled objects found in a case statement 2950 -- which actually models a case expression because their early 2951 -- finalization will affect the result of the expression. 2952 2953 if not From_Conditional_Expression (N) then 2954 Process_Statements_For_Controlled_Objects (Alt); 2955 end if; 2956 2957 Insert_List_After (N, Statements (Alt)); 2958 2959 -- That leaves the case statement as a shell. The alternative that 2960 -- will be executed is reset to a null list. So now we can kill 2961 -- the entire case statement. 2962 2963 Kill_Dead_Code (Expression (N)); 2964 Rewrite (N, Make_Null_Statement (Loc)); 2965 return; 2966 2967 -- An optimization. If there are only two alternatives, and only 2968 -- a single choice, then rewrite the whole case statement as an 2969 -- if statement, since this can result in subsequent optimizations. 2970 -- This helps not only with case statements in the source of a 2971 -- simple form, but also with generated code (discriminant check 2972 -- functions in particular). 2973 2974 -- Note: it is OK to do this before expanding out choices for any 2975 -- static predicates, since the if statement processing will handle 2976 -- the static predicate case fine. 2977 2978 elsif Len = 2 then 2979 Chlist := Discrete_Choices (First (Alternatives (N))); 2980 2981 if List_Length (Chlist) = 1 then 2982 Choice := First (Chlist); 2983 2984 Then_Stms := Statements (First (Alternatives (N))); 2985 Else_Stms := Statements (Last (Alternatives (N))); 2986 2987 -- For TRUE, generate "expression", not expression = true 2988 2989 if Nkind (Choice) = N_Identifier 2990 and then Entity (Choice) = Standard_True 2991 then 2992 Cond := Expression (N); 2993 2994 -- For FALSE, generate "expression" and switch then/else 2995 2996 elsif Nkind (Choice) = N_Identifier 2997 and then Entity (Choice) = Standard_False 2998 then 2999 Cond := Expression (N); 3000 Else_Stms := Statements (First (Alternatives (N))); 3001 Then_Stms := Statements (Last (Alternatives (N))); 3002 3003 -- For a range, generate "expression in range" 3004 3005 elsif Nkind (Choice) = N_Range 3006 or else (Nkind (Choice) = N_Attribute_Reference 3007 and then Attribute_Name (Choice) = Name_Range) 3008 or else (Is_Entity_Name (Choice) 3009 and then Is_Type (Entity (Choice))) 3010 then 3011 Cond := 3012 Make_In (Loc, 3013 Left_Opnd => Expression (N), 3014 Right_Opnd => Relocate_Node (Choice)); 3015 3016 -- A subtype indication is not a legal operator in a membership 3017 -- test, so retrieve its range. 3018 3019 elsif Nkind (Choice) = N_Subtype_Indication then 3020 Cond := 3021 Make_In (Loc, 3022 Left_Opnd => Expression (N), 3023 Right_Opnd => 3024 Relocate_Node 3025 (Range_Expression (Constraint (Choice)))); 3026 3027 -- For any other subexpression "expression = value" 3028 3029 else 3030 Cond := 3031 Make_Op_Eq (Loc, 3032 Left_Opnd => Expression (N), 3033 Right_Opnd => Relocate_Node (Choice)); 3034 end if; 3035 3036 -- Now rewrite the case as an IF 3037 3038 Rewrite (N, 3039 Make_If_Statement (Loc, 3040 Condition => Cond, 3041 Then_Statements => Then_Stms, 3042 Else_Statements => Else_Stms)); 3043 Analyze (N); 3044 return; 3045 end if; 3046 end if; 3047 3048 -- If the last alternative is not an Others choice, replace it with 3049 -- an N_Others_Choice. Note that we do not bother to call Analyze on 3050 -- the modified case statement, since it's only effect would be to 3051 -- compute the contents of the Others_Discrete_Choices which is not 3052 -- needed by the back end anyway. 3053 3054 -- The reason for this is that the back end always needs some default 3055 -- for a switch, so if we have not supplied one in the processing 3056 -- above for validity checking, then we need to supply one here. 3057 3058 if not Others_Present then 3059 Others_Node := Make_Others_Choice (Sloc (Last_Alt)); 3060 3061 -- If Predicates_Ignored is true the value does not satisfy the 3062 -- predicate, and there is no Others choice, Constraint_Error 3063 -- must be raised (4.5.7 (21/3)). 3064 3065 if Predicates_Ignored (Etype (Expr)) then 3066 declare 3067 Except : constant Node_Id := 3068 Make_Raise_Constraint_Error (Loc, 3069 Reason => CE_Invalid_Data); 3070 New_Alt : constant Node_Id := 3071 Make_Case_Statement_Alternative (Loc, 3072 Discrete_Choices => New_List ( 3073 Make_Others_Choice (Loc)), 3074 Statements => New_List (Except)); 3075 3076 begin 3077 Append (New_Alt, Alternatives (N)); 3078 Analyze_And_Resolve (Except); 3079 end; 3080 3081 else 3082 Set_Others_Discrete_Choices 3083 (Others_Node, Discrete_Choices (Last_Alt)); 3084 Set_Discrete_Choices (Last_Alt, New_List (Others_Node)); 3085 end if; 3086 3087 end if; 3088 3089 -- Deal with possible declarations of controlled objects, and also 3090 -- with rewriting choice sequences for static predicate references. 3091 3092 Alt := First_Non_Pragma (Alternatives (N)); 3093 while Present (Alt) loop 3094 3095 -- Do not consider controlled objects found in a case statement 3096 -- which actually models a case expression because their early 3097 -- finalization will affect the result of the expression. 3098 3099 if not From_Conditional_Expression (N) then 3100 Process_Statements_For_Controlled_Objects (Alt); 3101 end if; 3102 3103 if Has_SP_Choice (Alt) then 3104 Expand_Static_Predicates_In_Choices (Alt); 3105 end if; 3106 3107 Next_Non_Pragma (Alt); 3108 end loop; 3109 end; 3110 end Expand_N_Case_Statement; 3111 3112 ----------------------------- 3113 -- Expand_N_Exit_Statement -- 3114 ----------------------------- 3115 3116 -- The only processing required is to deal with a possible C/Fortran 3117 -- boolean value used as the condition for the exit statement. 3118 3119 procedure Expand_N_Exit_Statement (N : Node_Id) is 3120 begin 3121 Adjust_Condition (Condition (N)); 3122 end Expand_N_Exit_Statement; 3123 3124 ---------------------------------- 3125 -- Expand_Formal_Container_Loop -- 3126 ---------------------------------- 3127 3128 procedure Expand_Formal_Container_Loop (N : Node_Id) is 3129 Loc : constant Source_Ptr := Sloc (N); 3130 Isc : constant Node_Id := Iteration_Scheme (N); 3131 I_Spec : constant Node_Id := Iterator_Specification (Isc); 3132 Cursor : constant Entity_Id := Defining_Identifier (I_Spec); 3133 Container : constant Node_Id := Entity (Name (I_Spec)); 3134 Stats : constant List_Id := Statements (N); 3135 3136 Advance : Node_Id; 3137 Init_Decl : Node_Id; 3138 Init_Name : Entity_Id; 3139 New_Loop : Node_Id; 3140 3141 begin 3142 -- The expansion of a formal container loop resembles the one for Ada 3143 -- containers. The only difference is that the primitives mention the 3144 -- domain of iteration explicitly, and function First applied to the 3145 -- container yields a cursor directly. 3146 3147 -- Cursor : Cursor_type := First (Container); 3148 -- while Has_Element (Cursor, Container) loop 3149 -- <original loop statements> 3150 -- Cursor := Next (Container, Cursor); 3151 -- end loop; 3152 3153 Build_Formal_Container_Iteration 3154 (N, Container, Cursor, Init_Decl, Advance, New_Loop); 3155 3156 Append_To (Stats, Advance); 3157 3158 -- Build a block to capture declaration of the cursor 3159 3160 Rewrite (N, 3161 Make_Block_Statement (Loc, 3162 Declarations => New_List (Init_Decl), 3163 Handled_Statement_Sequence => 3164 Make_Handled_Sequence_Of_Statements (Loc, 3165 Statements => New_List (New_Loop)))); 3166 3167 -- The loop parameter is declared by an object declaration, but within 3168 -- the loop we must prevent user assignments to it, so we analyze the 3169 -- declaration and reset the entity kind, before analyzing the rest of 3170 -- the loop. 3171 3172 Analyze (Init_Decl); 3173 Init_Name := Defining_Identifier (Init_Decl); 3174 Set_Ekind (Init_Name, E_Loop_Parameter); 3175 3176 -- The cursor was marked as a loop parameter to prevent user assignments 3177 -- to it, however this renders the advancement step illegal as it is not 3178 -- possible to change the value of a constant. Flag the advancement step 3179 -- as a legal form of assignment to remedy this side effect. 3180 3181 Set_Assignment_OK (Name (Advance)); 3182 Analyze (N); 3183 3184 -- Because we have to analyze the initial declaration of the loop 3185 -- parameter multiple times its scope is incorrectly set at this point 3186 -- to the one surrounding the block statement - so set the scope 3187 -- manually to be the actual block statement, and indicate that it is 3188 -- not visible after the block has been analyzed. 3189 3190 Set_Scope (Init_Name, Entity (Identifier (N))); 3191 Set_Is_Immediately_Visible (Init_Name, False); 3192 end Expand_Formal_Container_Loop; 3193 3194 ------------------------------------------ 3195 -- Expand_Formal_Container_Element_Loop -- 3196 ------------------------------------------ 3197 3198 procedure Expand_Formal_Container_Element_Loop (N : Node_Id) is 3199 Loc : constant Source_Ptr := Sloc (N); 3200 Isc : constant Node_Id := Iteration_Scheme (N); 3201 I_Spec : constant Node_Id := Iterator_Specification (Isc); 3202 Element : constant Entity_Id := Defining_Identifier (I_Spec); 3203 Container : constant Node_Id := Entity (Name (I_Spec)); 3204 Container_Typ : constant Entity_Id := Base_Type (Etype (Container)); 3205 Stats : constant List_Id := Statements (N); 3206 3207 Cursor : constant Entity_Id := 3208 Make_Defining_Identifier (Loc, 3209 Chars => New_External_Name (Chars (Element), 'C')); 3210 Elmt_Decl : Node_Id; 3211 Elmt_Ref : Node_Id; 3212 3213 Element_Op : constant Entity_Id := 3214 Get_Iterable_Type_Primitive (Container_Typ, Name_Element); 3215 3216 Advance : Node_Id; 3217 Init : Node_Id; 3218 New_Loop : Node_Id; 3219 3220 begin 3221 -- For an element iterator, the Element aspect must be present, 3222 -- (this is checked during analysis) and the expansion takes the form: 3223 3224 -- Cursor : Cursor_Type := First (Container); 3225 -- Elmt : Element_Type; 3226 -- while Has_Element (Cursor, Container) loop 3227 -- Elmt := Element (Container, Cursor); 3228 -- <original loop statements> 3229 -- Cursor := Next (Container, Cursor); 3230 -- end loop; 3231 3232 -- However this expansion is not legal if the element is indefinite. 3233 -- In that case we create a block to hold a variable declaration 3234 -- initialized with a call to Element, and generate: 3235 3236 -- Cursor : Cursor_Type := First (Container); 3237 -- while Has_Element (Cursor, Container) loop 3238 -- declare 3239 -- Elmt : Element_Type := Element (Container, Cursor); 3240 -- begin 3241 -- <original loop statements> 3242 -- Cursor := Next (Container, Cursor); 3243 -- end; 3244 -- end loop; 3245 3246 Build_Formal_Container_Iteration 3247 (N, Container, Cursor, Init, Advance, New_Loop); 3248 Append_To (Stats, Advance); 3249 3250 Set_Ekind (Cursor, E_Variable); 3251 Insert_Action (N, Init); 3252 3253 -- Declaration for Element 3254 3255 Elmt_Decl := 3256 Make_Object_Declaration (Loc, 3257 Defining_Identifier => Element, 3258 Object_Definition => New_Occurrence_Of (Etype (Element_Op), Loc)); 3259 3260 if not Is_Constrained (Etype (Element_Op)) then 3261 Set_Expression (Elmt_Decl, 3262 Make_Function_Call (Loc, 3263 Name => New_Occurrence_Of (Element_Op, Loc), 3264 Parameter_Associations => New_List ( 3265 Convert_To_Iterable_Type (Container, Loc), 3266 New_Occurrence_Of (Cursor, Loc)))); 3267 3268 Set_Statements (New_Loop, 3269 New_List 3270 (Make_Block_Statement (Loc, 3271 Declarations => New_List (Elmt_Decl), 3272 Handled_Statement_Sequence => 3273 Make_Handled_Sequence_Of_Statements (Loc, 3274 Statements => Stats)))); 3275 3276 else 3277 Elmt_Ref := 3278 Make_Assignment_Statement (Loc, 3279 Name => New_Occurrence_Of (Element, Loc), 3280 Expression => 3281 Make_Function_Call (Loc, 3282 Name => New_Occurrence_Of (Element_Op, Loc), 3283 Parameter_Associations => New_List ( 3284 Convert_To_Iterable_Type (Container, Loc), 3285 New_Occurrence_Of (Cursor, Loc)))); 3286 3287 Prepend (Elmt_Ref, Stats); 3288 3289 -- The element is assignable in the expanded code 3290 3291 Set_Assignment_OK (Name (Elmt_Ref)); 3292 3293 -- The loop is rewritten as a block, to hold the element declaration 3294 3295 New_Loop := 3296 Make_Block_Statement (Loc, 3297 Declarations => New_List (Elmt_Decl), 3298 Handled_Statement_Sequence => 3299 Make_Handled_Sequence_Of_Statements (Loc, 3300 Statements => New_List (New_Loop))); 3301 end if; 3302 3303 -- The element is only modified in expanded code, so it appears as 3304 -- unassigned to the warning machinery. We must suppress this spurious 3305 -- warning explicitly. 3306 3307 Set_Warnings_Off (Element); 3308 3309 Rewrite (N, New_Loop); 3310 3311 -- The loop parameter is declared by an object declaration, but within 3312 -- the loop we must prevent user assignments to it, so we analyze the 3313 -- declaration and reset the entity kind, before analyzing the rest of 3314 -- the loop. 3315 3316 Analyze (Elmt_Decl); 3317 Set_Ekind (Defining_Identifier (Elmt_Decl), E_Loop_Parameter); 3318 3319 Analyze (N); 3320 end Expand_Formal_Container_Element_Loop; 3321 3322 ----------------------------- 3323 -- Expand_N_Goto_Statement -- 3324 ----------------------------- 3325 3326 -- Add poll before goto if polling active 3327 3328 procedure Expand_N_Goto_Statement (N : Node_Id) is 3329 begin 3330 Generate_Poll_Call (N); 3331 end Expand_N_Goto_Statement; 3332 3333 --------------------------- 3334 -- Expand_N_If_Statement -- 3335 --------------------------- 3336 3337 -- First we deal with the case of C and Fortran convention boolean values, 3338 -- with zero/non-zero semantics. 3339 3340 -- Second, we deal with the obvious rewriting for the cases where the 3341 -- condition of the IF is known at compile time to be True or False. 3342 3343 -- Third, we remove elsif parts which have non-empty Condition_Actions and 3344 -- rewrite as independent if statements. For example: 3345 3346 -- if x then xs 3347 -- elsif y then ys 3348 -- ... 3349 -- end if; 3350 3351 -- becomes 3352 -- 3353 -- if x then xs 3354 -- else 3355 -- <<condition actions of y>> 3356 -- if y then ys 3357 -- ... 3358 -- end if; 3359 -- end if; 3360 3361 -- This rewriting is needed if at least one elsif part has a non-empty 3362 -- Condition_Actions list. We also do the same processing if there is a 3363 -- constant condition in an elsif part (in conjunction with the first 3364 -- processing step mentioned above, for the recursive call made to deal 3365 -- with the created inner if, this deals with properly optimizing the 3366 -- cases of constant elsif conditions). 3367 3368 procedure Expand_N_If_Statement (N : Node_Id) is 3369 Loc : constant Source_Ptr := Sloc (N); 3370 Hed : Node_Id; 3371 E : Node_Id; 3372 New_If : Node_Id; 3373 3374 Warn_If_Deleted : constant Boolean := 3375 Warn_On_Deleted_Code and then Comes_From_Source (N); 3376 -- Indicates whether we want warnings when we delete branches of the 3377 -- if statement based on constant condition analysis. We never want 3378 -- these warnings for expander generated code. 3379 3380 begin 3381 -- Do not consider controlled objects found in an if statement which 3382 -- actually models an if expression because their early finalization 3383 -- will affect the result of the expression. 3384 3385 if not From_Conditional_Expression (N) then 3386 Process_Statements_For_Controlled_Objects (N); 3387 end if; 3388 3389 Adjust_Condition (Condition (N)); 3390 3391 -- The following loop deals with constant conditions for the IF. We 3392 -- need a loop because as we eliminate False conditions, we grab the 3393 -- first elsif condition and use it as the primary condition. 3394 3395 while Compile_Time_Known_Value (Condition (N)) loop 3396 3397 -- If condition is True, we can simply rewrite the if statement now 3398 -- by replacing it by the series of then statements. 3399 3400 if Is_True (Expr_Value (Condition (N))) then 3401 3402 -- All the else parts can be killed 3403 3404 Kill_Dead_Code (Elsif_Parts (N), Warn_If_Deleted); 3405 Kill_Dead_Code (Else_Statements (N), Warn_If_Deleted); 3406 3407 Hed := Remove_Head (Then_Statements (N)); 3408 Insert_List_After (N, Then_Statements (N)); 3409 Rewrite (N, Hed); 3410 return; 3411 3412 -- If condition is False, then we can delete the condition and 3413 -- the Then statements 3414 3415 else 3416 -- We do not delete the condition if constant condition warnings 3417 -- are enabled, since otherwise we end up deleting the desired 3418 -- warning. Of course the backend will get rid of this True/False 3419 -- test anyway, so nothing is lost here. 3420 3421 if not Constant_Condition_Warnings then 3422 Kill_Dead_Code (Condition (N)); 3423 end if; 3424 3425 Kill_Dead_Code (Then_Statements (N), Warn_If_Deleted); 3426 3427 -- If there are no elsif statements, then we simply replace the 3428 -- entire if statement by the sequence of else statements. 3429 3430 if No (Elsif_Parts (N)) then 3431 if No (Else_Statements (N)) 3432 or else Is_Empty_List (Else_Statements (N)) 3433 then 3434 Rewrite (N, 3435 Make_Null_Statement (Sloc (N))); 3436 else 3437 Hed := Remove_Head (Else_Statements (N)); 3438 Insert_List_After (N, Else_Statements (N)); 3439 Rewrite (N, Hed); 3440 end if; 3441 3442 return; 3443 3444 -- If there are elsif statements, the first of them becomes the 3445 -- if/then section of the rebuilt if statement This is the case 3446 -- where we loop to reprocess this copied condition. 3447 3448 else 3449 Hed := Remove_Head (Elsif_Parts (N)); 3450 Insert_Actions (N, Condition_Actions (Hed)); 3451 Set_Condition (N, Condition (Hed)); 3452 Set_Then_Statements (N, Then_Statements (Hed)); 3453 3454 -- Hed might have been captured as the condition determining 3455 -- the current value for an entity. Now it is detached from 3456 -- the tree, so a Current_Value pointer in the condition might 3457 -- need to be updated. 3458 3459 Set_Current_Value_Condition (N); 3460 3461 if Is_Empty_List (Elsif_Parts (N)) then 3462 Set_Elsif_Parts (N, No_List); 3463 end if; 3464 end if; 3465 end if; 3466 end loop; 3467 3468 -- Loop through elsif parts, dealing with constant conditions and 3469 -- possible condition actions that are present. 3470 3471 if Present (Elsif_Parts (N)) then 3472 E := First (Elsif_Parts (N)); 3473 while Present (E) loop 3474 3475 -- Do not consider controlled objects found in an if statement 3476 -- which actually models an if expression because their early 3477 -- finalization will affect the result of the expression. 3478 3479 if not From_Conditional_Expression (N) then 3480 Process_Statements_For_Controlled_Objects (E); 3481 end if; 3482 3483 Adjust_Condition (Condition (E)); 3484 3485 -- If there are condition actions, then rewrite the if statement 3486 -- as indicated above. We also do the same rewrite for a True or 3487 -- False condition. The further processing of this constant 3488 -- condition is then done by the recursive call to expand the 3489 -- newly created if statement 3490 3491 if Present (Condition_Actions (E)) 3492 or else Compile_Time_Known_Value (Condition (E)) 3493 then 3494 New_If := 3495 Make_If_Statement (Sloc (E), 3496 Condition => Condition (E), 3497 Then_Statements => Then_Statements (E), 3498 Elsif_Parts => No_List, 3499 Else_Statements => Else_Statements (N)); 3500 3501 -- Elsif parts for new if come from remaining elsif's of parent 3502 3503 while Present (Next (E)) loop 3504 if No (Elsif_Parts (New_If)) then 3505 Set_Elsif_Parts (New_If, New_List); 3506 end if; 3507 3508 Append (Remove_Next (E), Elsif_Parts (New_If)); 3509 end loop; 3510 3511 Set_Else_Statements (N, New_List (New_If)); 3512 3513 if Present (Condition_Actions (E)) then 3514 Insert_List_Before (New_If, Condition_Actions (E)); 3515 end if; 3516 3517 Remove (E); 3518 3519 if Is_Empty_List (Elsif_Parts (N)) then 3520 Set_Elsif_Parts (N, No_List); 3521 end if; 3522 3523 Analyze (New_If); 3524 3525 -- Note this is not an implicit if statement, since it is part 3526 -- of an explicit if statement in the source (or of an implicit 3527 -- if statement that has already been tested). We set the flag 3528 -- after calling Analyze to avoid generating extra warnings 3529 -- specific to pure if statements, however (see 3530 -- Sem_Ch5.Analyze_If_Statement). 3531 3532 Set_Comes_From_Source (New_If, Comes_From_Source (N)); 3533 return; 3534 3535 -- No special processing for that elsif part, move to next 3536 3537 else 3538 Next (E); 3539 end if; 3540 end loop; 3541 end if; 3542 3543 -- Some more optimizations applicable if we still have an IF statement 3544 3545 if Nkind (N) /= N_If_Statement then 3546 return; 3547 end if; 3548 3549 -- Another optimization, special cases that can be simplified 3550 3551 -- if expression then 3552 -- return true; 3553 -- else 3554 -- return false; 3555 -- end if; 3556 3557 -- can be changed to: 3558 3559 -- return expression; 3560 3561 -- and 3562 3563 -- if expression then 3564 -- return false; 3565 -- else 3566 -- return true; 3567 -- end if; 3568 3569 -- can be changed to: 3570 3571 -- return not (expression); 3572 3573 -- Only do these optimizations if we are at least at -O1 level and 3574 -- do not do them if control flow optimizations are suppressed. 3575 3576 if Optimization_Level > 0 3577 and then not Opt.Suppress_Control_Flow_Optimizations 3578 then 3579 if Nkind (N) = N_If_Statement 3580 and then No (Elsif_Parts (N)) 3581 and then Present (Else_Statements (N)) 3582 and then List_Length (Then_Statements (N)) = 1 3583 and then List_Length (Else_Statements (N)) = 1 3584 then 3585 declare 3586 Then_Stm : constant Node_Id := First (Then_Statements (N)); 3587 Else_Stm : constant Node_Id := First (Else_Statements (N)); 3588 3589 begin 3590 if Nkind (Then_Stm) = N_Simple_Return_Statement 3591 and then 3592 Nkind (Else_Stm) = N_Simple_Return_Statement 3593 then 3594 declare 3595 Then_Expr : constant Node_Id := Expression (Then_Stm); 3596 Else_Expr : constant Node_Id := Expression (Else_Stm); 3597 3598 begin 3599 if Nkind (Then_Expr) = N_Identifier 3600 and then 3601 Nkind (Else_Expr) = N_Identifier 3602 then 3603 if Entity (Then_Expr) = Standard_True 3604 and then Entity (Else_Expr) = Standard_False 3605 then 3606 Rewrite (N, 3607 Make_Simple_Return_Statement (Loc, 3608 Expression => Relocate_Node (Condition (N)))); 3609 Analyze (N); 3610 return; 3611 3612 elsif Entity (Then_Expr) = Standard_False 3613 and then Entity (Else_Expr) = Standard_True 3614 then 3615 Rewrite (N, 3616 Make_Simple_Return_Statement (Loc, 3617 Expression => 3618 Make_Op_Not (Loc, 3619 Right_Opnd => 3620 Relocate_Node (Condition (N))))); 3621 Analyze (N); 3622 return; 3623 end if; 3624 end if; 3625 end; 3626 end if; 3627 end; 3628 end if; 3629 end if; 3630 end Expand_N_If_Statement; 3631 3632 -------------------------- 3633 -- Expand_Iterator_Loop -- 3634 -------------------------- 3635 3636 procedure Expand_Iterator_Loop (N : Node_Id) is 3637 Isc : constant Node_Id := Iteration_Scheme (N); 3638 I_Spec : constant Node_Id := Iterator_Specification (Isc); 3639 3640 Container : constant Node_Id := Name (I_Spec); 3641 Container_Typ : constant Entity_Id := Base_Type (Etype (Container)); 3642 3643 begin 3644 -- Processing for arrays 3645 3646 if Is_Array_Type (Container_Typ) then 3647 pragma Assert (Of_Present (I_Spec)); 3648 Expand_Iterator_Loop_Over_Array (N); 3649 3650 elsif Has_Aspect (Container_Typ, Aspect_Iterable) then 3651 if Of_Present (I_Spec) then 3652 Expand_Formal_Container_Element_Loop (N); 3653 else 3654 Expand_Formal_Container_Loop (N); 3655 end if; 3656 3657 -- Processing for containers 3658 3659 else 3660 Expand_Iterator_Loop_Over_Container 3661 (N, Isc, I_Spec, Container, Container_Typ); 3662 end if; 3663 end Expand_Iterator_Loop; 3664 3665 ------------------------------------- 3666 -- Expand_Iterator_Loop_Over_Array -- 3667 ------------------------------------- 3668 3669 procedure Expand_Iterator_Loop_Over_Array (N : Node_Id) is 3670 Isc : constant Node_Id := Iteration_Scheme (N); 3671 I_Spec : constant Node_Id := Iterator_Specification (Isc); 3672 Array_Node : constant Node_Id := Name (I_Spec); 3673 Array_Typ : constant Entity_Id := Base_Type (Etype (Array_Node)); 3674 Array_Dim : constant Pos := Number_Dimensions (Array_Typ); 3675 Id : constant Entity_Id := Defining_Identifier (I_Spec); 3676 Loc : constant Source_Ptr := Sloc (Isc); 3677 Stats : constant List_Id := Statements (N); 3678 Core_Loop : Node_Id; 3679 Dim1 : Int; 3680 Ind_Comp : Node_Id; 3681 Iterator : Entity_Id; 3682 3683 -- Start of processing for Expand_Iterator_Loop_Over_Array 3684 3685 begin 3686 -- for Element of Array loop 3687 3688 -- It requires an internally generated cursor to iterate over the array 3689 3690 pragma Assert (Of_Present (I_Spec)); 3691 3692 Iterator := Make_Temporary (Loc, 'C'); 3693 3694 -- Generate: 3695 -- Element : Component_Type renames Array (Iterator); 3696 -- Iterator is the index value, or a list of index values 3697 -- in the case of a multidimensional array. 3698 3699 Ind_Comp := 3700 Make_Indexed_Component (Loc, 3701 Prefix => Relocate_Node (Array_Node), 3702 Expressions => New_List (New_Occurrence_Of (Iterator, Loc))); 3703 3704 Prepend_To (Stats, 3705 Make_Object_Renaming_Declaration (Loc, 3706 Defining_Identifier => Id, 3707 Subtype_Mark => 3708 New_Occurrence_Of (Component_Type (Array_Typ), Loc), 3709 Name => Ind_Comp)); 3710 3711 -- Mark the loop variable as needing debug info, so that expansion 3712 -- of the renaming will result in Materialize_Entity getting set via 3713 -- Debug_Renaming_Declaration. (This setting is needed here because 3714 -- the setting in Freeze_Entity comes after the expansion, which is 3715 -- too late. ???) 3716 3717 Set_Debug_Info_Needed (Id); 3718 3719 -- Generate: 3720 3721 -- for Iterator in [reverse] Array'Range (Array_Dim) loop 3722 -- Element : Component_Type renames Array (Iterator); 3723 -- <original loop statements> 3724 -- end loop; 3725 3726 -- If this is an iteration over a multidimensional array, the 3727 -- innermost loop is over the last dimension in Ada, and over 3728 -- the first dimension in Fortran. 3729 3730 if Convention (Array_Typ) = Convention_Fortran then 3731 Dim1 := 1; 3732 else 3733 Dim1 := Array_Dim; 3734 end if; 3735 3736 Core_Loop := 3737 Make_Loop_Statement (Sloc (N), 3738 Iteration_Scheme => 3739 Make_Iteration_Scheme (Loc, 3740 Loop_Parameter_Specification => 3741 Make_Loop_Parameter_Specification (Loc, 3742 Defining_Identifier => Iterator, 3743 Discrete_Subtype_Definition => 3744 Make_Attribute_Reference (Loc, 3745 Prefix => Relocate_Node (Array_Node), 3746 Attribute_Name => Name_Range, 3747 Expressions => New_List ( 3748 Make_Integer_Literal (Loc, Dim1))), 3749 Reverse_Present => Reverse_Present (I_Spec))), 3750 Statements => Stats, 3751 End_Label => Empty); 3752 3753 -- Processing for multidimensional array. The body of each loop is 3754 -- a loop over a previous dimension, going in decreasing order in Ada 3755 -- and in increasing order in Fortran. 3756 3757 if Array_Dim > 1 then 3758 for Dim in 1 .. Array_Dim - 1 loop 3759 if Convention (Array_Typ) = Convention_Fortran then 3760 Dim1 := Dim + 1; 3761 else 3762 Dim1 := Array_Dim - Dim; 3763 end if; 3764 3765 Iterator := Make_Temporary (Loc, 'C'); 3766 3767 -- Generate the dimension loops starting from the innermost one 3768 3769 -- for Iterator in [reverse] Array'Range (Array_Dim - Dim) loop 3770 -- <core loop> 3771 -- end loop; 3772 3773 Core_Loop := 3774 Make_Loop_Statement (Sloc (N), 3775 Iteration_Scheme => 3776 Make_Iteration_Scheme (Loc, 3777 Loop_Parameter_Specification => 3778 Make_Loop_Parameter_Specification (Loc, 3779 Defining_Identifier => Iterator, 3780 Discrete_Subtype_Definition => 3781 Make_Attribute_Reference (Loc, 3782 Prefix => Relocate_Node (Array_Node), 3783 Attribute_Name => Name_Range, 3784 Expressions => New_List ( 3785 Make_Integer_Literal (Loc, Dim1))), 3786 Reverse_Present => Reverse_Present (I_Spec))), 3787 Statements => New_List (Core_Loop), 3788 End_Label => Empty); 3789 3790 -- Update the previously created object renaming declaration with 3791 -- the new iterator, by adding the index of the next loop to the 3792 -- indexed component, in the order that corresponds to the 3793 -- convention. 3794 3795 if Convention (Array_Typ) = Convention_Fortran then 3796 Append_To (Expressions (Ind_Comp), 3797 New_Occurrence_Of (Iterator, Loc)); 3798 else 3799 Prepend_To (Expressions (Ind_Comp), 3800 New_Occurrence_Of (Iterator, Loc)); 3801 end if; 3802 end loop; 3803 end if; 3804 3805 -- Inherit the loop identifier from the original loop. This ensures that 3806 -- the scope stack is consistent after the rewriting. 3807 3808 if Present (Identifier (N)) then 3809 Set_Identifier (Core_Loop, Relocate_Node (Identifier (N))); 3810 end if; 3811 3812 Rewrite (N, Core_Loop); 3813 Analyze (N); 3814 end Expand_Iterator_Loop_Over_Array; 3815 3816 ----------------------------------------- 3817 -- Expand_Iterator_Loop_Over_Container -- 3818 ----------------------------------------- 3819 3820 -- For a 'for ... in' loop, such as: 3821 3822 -- for Cursor in Iterator_Function (...) loop 3823 -- ... 3824 -- end loop; 3825 3826 -- we generate: 3827 3828 -- Iter : Iterator_Type := Iterator_Function (...); 3829 -- Cursor : Cursor_type := First (Iter); -- or Last for "reverse" 3830 -- while Has_Element (Cursor) loop 3831 -- ... 3832 -- 3833 -- Cursor := Iter.Next (Cursor); -- or Prev for "reverse" 3834 -- end loop; 3835 3836 -- For a 'for ... of' loop, such as: 3837 3838 -- for X of Container loop 3839 -- ... 3840 -- end loop; 3841 3842 -- the RM implies the generation of: 3843 3844 -- Iter : Iterator_Type := Container.Iterate; -- the Default_Iterator 3845 -- Cursor : Cursor_Type := First (Iter); -- or Last for "reverse" 3846 -- while Has_Element (Cursor) loop 3847 -- declare 3848 -- X : Element_Type renames Element (Cursor).Element.all; 3849 -- -- or Constant_Element 3850 -- begin 3851 -- ... 3852 -- end; 3853 -- Cursor := Iter.Next (Cursor); -- or Prev for "reverse" 3854 -- end loop; 3855 3856 -- In the general case, we do what the RM says. However, the operations 3857 -- Element and Iter.Next are slow, which is bad inside a loop, because they 3858 -- involve dispatching via interfaces, secondary stack manipulation, 3859 -- Busy/Lock incr/decr, and adjust/finalization/at-end handling. So for the 3860 -- predefined containers, we use an equivalent but optimized expansion. 3861 3862 -- In the optimized case, we make use of these: 3863 3864 -- procedure Next (Position : in out Cursor); -- instead of Iter.Next 3865 3866 -- function Pseudo_Reference 3867 -- (Container : aliased Vector'Class) return Reference_Control_Type; 3868 3869 -- type Element_Access is access all Element_Type; 3870 3871 -- function Get_Element_Access 3872 -- (Position : Cursor) return not null Element_Access; 3873 3874 -- Next is declared in the visible part of the container packages. 3875 -- The other three are added in the private part. (We're not supposed to 3876 -- pollute the namespace for clients. The compiler has no trouble breaking 3877 -- privacy to call things in the private part of an instance.) 3878 3879 -- Source: 3880 3881 -- for X of My_Vector loop 3882 -- X.Count := X.Count + 1; 3883 -- ... 3884 -- end loop; 3885 3886 -- The compiler will generate: 3887 3888 -- Iter : Reversible_Iterator'Class := Iterate (My_Vector); 3889 -- -- Reversible_Iterator is an interface. Iterate is the 3890 -- -- Default_Iterator aspect of Vector. This increments Lock, 3891 -- -- disallowing tampering with cursors. Unfortunately, it does not 3892 -- -- increment Busy. The result of Iterate is Limited_Controlled; 3893 -- -- finalization will decrement Lock. This is a build-in-place 3894 -- -- dispatching call to Iterate. 3895 3896 -- Cur : Cursor := First (Iter); -- or Last 3897 -- -- Dispatching call via interface. 3898 3899 -- Control : Reference_Control_Type := Pseudo_Reference (My_Vector); 3900 -- -- Pseudo_Reference increments Busy, to detect tampering with 3901 -- -- elements, as required by RM. Also redundantly increment 3902 -- -- Lock. Finalization of Control will decrement both Busy and 3903 -- -- Lock. Pseudo_Reference returns a record containing a pointer to 3904 -- -- My_Vector, used by Finalize. 3905 -- -- 3906 -- -- Control is not used below, except to finalize it -- it's purely 3907 -- -- an RAII thing. This is needed because we are eliminating the 3908 -- -- call to Reference within the loop. 3909 3910 -- while Has_Element (Cur) loop 3911 -- declare 3912 -- X : My_Element renames Get_Element_Access (Cur).all; 3913 -- -- Get_Element_Access returns a pointer to the element 3914 -- -- designated by Cur. No dispatching here, and no horsing 3915 -- -- around with access discriminants. This is instead of the 3916 -- -- existing 3917 -- -- 3918 -- -- X : My_Element renames Reference (Cur).Element.all; 3919 -- -- 3920 -- -- which creates a controlled object. 3921 -- begin 3922 -- -- Any attempt to tamper with My_Vector here in the loop 3923 -- -- will correctly raise Program_Error, because of the 3924 -- -- Control. 3925 -- 3926 -- X.Count := X.Count + 1; 3927 -- ... 3928 -- 3929 -- Next (Cur); -- or Prev 3930 -- -- This is instead of "Cur := Next (Iter, Cur);" 3931 -- end; 3932 -- -- No finalization here 3933 -- end loop; 3934 -- Finalize Iter and Control here, decrementing Lock twice and Busy 3935 -- once. 3936 3937 -- This optimization makes "for ... of" loops over 30 times faster in cases 3938 -- measured. 3939 3940 procedure Expand_Iterator_Loop_Over_Container 3941 (N : Node_Id; 3942 Isc : Node_Id; 3943 I_Spec : Node_Id; 3944 Container : Node_Id; 3945 Container_Typ : Entity_Id) 3946 is 3947 Id : constant Entity_Id := Defining_Identifier (I_Spec); 3948 Elem_Typ : constant Entity_Id := Etype (Id); 3949 Id_Kind : constant Entity_Kind := Ekind (Id); 3950 Loc : constant Source_Ptr := Sloc (N); 3951 Stats : constant List_Id := Statements (N); 3952 3953 Cursor : Entity_Id; 3954 Decl : Node_Id; 3955 Iter_Type : Entity_Id; 3956 Iterator : Entity_Id; 3957 Name_Init : Name_Id; 3958 Name_Step : Name_Id; 3959 New_Loop : Node_Id; 3960 3961 Fast_Element_Access_Op : Entity_Id := Empty; 3962 Fast_Step_Op : Entity_Id := Empty; 3963 -- Only for optimized version of "for ... of" 3964 3965 Iter_Pack : Entity_Id; 3966 -- The package in which the iterator interface is instantiated. This is 3967 -- typically an instance within the container package. 3968 3969 Pack : Entity_Id; 3970 -- The package in which the container type is declared 3971 3972 begin 3973 -- Determine the advancement and initialization steps for the cursor. 3974 -- Analysis of the expanded loop will verify that the container has a 3975 -- reverse iterator. 3976 3977 if Reverse_Present (I_Spec) then 3978 Name_Init := Name_Last; 3979 Name_Step := Name_Previous; 3980 else 3981 Name_Init := Name_First; 3982 Name_Step := Name_Next; 3983 end if; 3984 3985 -- The type of the iterator is the return type of the Iterate function 3986 -- used. For the "of" form this is the default iterator for the type, 3987 -- otherwise it is the type of the explicit function used in the 3988 -- iterator specification. The most common case will be an Iterate 3989 -- function in the container package. 3990 3991 -- The Iterator type is declared in an instance within the container 3992 -- package itself, for example: 3993 3994 -- package Vector_Iterator_Interfaces is new 3995 -- Ada.Iterator_Interfaces (Cursor, Has_Element); 3996 3997 -- If the container type is a derived type, the cursor type is found in 3998 -- the package of the ultimate ancestor type. 3999 4000 if Is_Derived_Type (Container_Typ) then 4001 Pack := Scope (Root_Type (Container_Typ)); 4002 else 4003 Pack := Scope (Container_Typ); 4004 end if; 4005 4006 if Of_Present (I_Spec) then 4007 Handle_Of : declare 4008 Container_Arg : Node_Id; 4009 4010 function Get_Default_Iterator 4011 (T : Entity_Id) return Entity_Id; 4012 -- Return the default iterator for a specific type. If the type is 4013 -- derived, we return the inherited or overridden one if 4014 -- appropriate. 4015 4016 -------------------------- 4017 -- Get_Default_Iterator -- 4018 -------------------------- 4019 4020 function Get_Default_Iterator 4021 (T : Entity_Id) return Entity_Id 4022 is 4023 Iter : constant Entity_Id := 4024 Entity (Find_Value_Of_Aspect (T, Aspect_Default_Iterator)); 4025 Prim : Elmt_Id; 4026 Op : Entity_Id; 4027 4028 begin 4029 Container_Arg := New_Copy_Tree (Container); 4030 4031 -- A previous version of GNAT allowed indexing aspects to be 4032 -- redefined on derived container types, while the default 4033 -- iterator was inherited from the parent type. This 4034 -- nonstandard extension is preserved for use by the 4035 -- modeling project under debug flag -gnatd.X. 4036 4037 if Debug_Flag_Dot_XX then 4038 if Base_Type (Etype (Container)) /= 4039 Base_Type (Etype (First_Formal (Iter))) 4040 then 4041 Container_Arg := 4042 Make_Type_Conversion (Loc, 4043 Subtype_Mark => 4044 New_Occurrence_Of 4045 (Etype (First_Formal (Iter)), Loc), 4046 Expression => Container_Arg); 4047 end if; 4048 4049 return Iter; 4050 4051 elsif Is_Derived_Type (T) then 4052 4053 -- The default iterator must be a primitive operation of the 4054 -- type, at the same dispatch slot position. The DT position 4055 -- may not be established if type is not frozen yet. 4056 4057 Prim := First_Elmt (Primitive_Operations (T)); 4058 while Present (Prim) loop 4059 Op := Node (Prim); 4060 4061 if Alias (Op) = Iter 4062 or else 4063 (Chars (Op) = Chars (Iter) 4064 and then Present (DTC_Entity (Op)) 4065 and then DT_Position (Op) = DT_Position (Iter)) 4066 then 4067 return Op; 4068 end if; 4069 4070 Next_Elmt (Prim); 4071 end loop; 4072 4073 -- If we didn't find it, then our parent type is not 4074 -- iterable, so we return the Default_Iterator aspect of 4075 -- this type. 4076 4077 return Iter; 4078 4079 -- Otherwise not a derived type 4080 4081 else 4082 return Iter; 4083 end if; 4084 end Get_Default_Iterator; 4085 4086 -- Local variables 4087 4088 Default_Iter : Entity_Id; 4089 Ent : Entity_Id; 4090 4091 Reference_Control_Type : Entity_Id := Empty; 4092 Pseudo_Reference : Entity_Id := Empty; 4093 4094 -- Start of processing for Handle_Of 4095 4096 begin 4097 if Is_Class_Wide_Type (Container_Typ) then 4098 Default_Iter := 4099 Get_Default_Iterator (Etype (Base_Type (Container_Typ))); 4100 else 4101 Default_Iter := Get_Default_Iterator (Etype (Container)); 4102 end if; 4103 4104 Cursor := Make_Temporary (Loc, 'C'); 4105 4106 -- For a container element iterator, the iterator type is obtained 4107 -- from the corresponding aspect, whose return type is descended 4108 -- from the corresponding interface type in some instance of 4109 -- Ada.Iterator_Interfaces. The actuals of that instantiation 4110 -- are Cursor and Has_Element. 4111 4112 Iter_Type := Etype (Default_Iter); 4113 4114 -- The iterator type, which is a class-wide type, may itself be 4115 -- derived locally, so the desired instantiation is the scope of 4116 -- the root type of the iterator type. 4117 4118 Iter_Pack := Scope (Root_Type (Etype (Iter_Type))); 4119 4120 -- Find declarations needed for "for ... of" optimization 4121 4122 Ent := First_Entity (Pack); 4123 while Present (Ent) loop 4124 if Chars (Ent) = Name_Get_Element_Access then 4125 Fast_Element_Access_Op := Ent; 4126 4127 elsif Chars (Ent) = Name_Step 4128 and then Ekind (Ent) = E_Procedure 4129 then 4130 Fast_Step_Op := Ent; 4131 4132 elsif Chars (Ent) = Name_Reference_Control_Type then 4133 Reference_Control_Type := Ent; 4134 4135 elsif Chars (Ent) = Name_Pseudo_Reference then 4136 Pseudo_Reference := Ent; 4137 end if; 4138 4139 Next_Entity (Ent); 4140 end loop; 4141 4142 if Present (Reference_Control_Type) 4143 and then Present (Pseudo_Reference) 4144 then 4145 Insert_Action (N, 4146 Make_Object_Declaration (Loc, 4147 Defining_Identifier => Make_Temporary (Loc, 'D'), 4148 Object_Definition => 4149 New_Occurrence_Of (Reference_Control_Type, Loc), 4150 Expression => 4151 Make_Function_Call (Loc, 4152 Name => 4153 New_Occurrence_Of (Pseudo_Reference, Loc), 4154 Parameter_Associations => 4155 New_List (New_Copy_Tree (Container_Arg))))); 4156 end if; 4157 4158 -- Rewrite domain of iteration as a call to the default iterator 4159 -- for the container type. The formal may be an access parameter 4160 -- in which case we must build a reference to the container. 4161 4162 declare 4163 Arg : Node_Id; 4164 begin 4165 if Is_Access_Type (Etype (First_Entity (Default_Iter))) then 4166 Arg := 4167 Make_Attribute_Reference (Loc, 4168 Prefix => Container_Arg, 4169 Attribute_Name => Name_Unrestricted_Access); 4170 else 4171 Arg := Container_Arg; 4172 end if; 4173 4174 Rewrite (Name (I_Spec), 4175 Make_Function_Call (Loc, 4176 Name => 4177 New_Occurrence_Of (Default_Iter, Loc), 4178 Parameter_Associations => New_List (Arg))); 4179 end; 4180 4181 Analyze_And_Resolve (Name (I_Spec)); 4182 4183 -- Find cursor type in proper iterator package, which is an 4184 -- instantiation of Iterator_Interfaces. 4185 4186 Ent := First_Entity (Iter_Pack); 4187 while Present (Ent) loop 4188 if Chars (Ent) = Name_Cursor then 4189 Set_Etype (Cursor, Etype (Ent)); 4190 exit; 4191 end if; 4192 4193 Next_Entity (Ent); 4194 end loop; 4195 4196 if Present (Fast_Element_Access_Op) then 4197 Decl := 4198 Make_Object_Renaming_Declaration (Loc, 4199 Defining_Identifier => Id, 4200 Subtype_Mark => 4201 New_Occurrence_Of (Elem_Typ, Loc), 4202 Name => 4203 Make_Explicit_Dereference (Loc, 4204 Prefix => 4205 Make_Function_Call (Loc, 4206 Name => 4207 New_Occurrence_Of (Fast_Element_Access_Op, Loc), 4208 Parameter_Associations => 4209 New_List (New_Occurrence_Of (Cursor, Loc))))); 4210 4211 else 4212 Decl := 4213 Make_Object_Renaming_Declaration (Loc, 4214 Defining_Identifier => Id, 4215 Subtype_Mark => 4216 New_Occurrence_Of (Elem_Typ, Loc), 4217 Name => 4218 Make_Indexed_Component (Loc, 4219 Prefix => Relocate_Node (Container_Arg), 4220 Expressions => 4221 New_List (New_Occurrence_Of (Cursor, Loc)))); 4222 end if; 4223 4224 -- The defining identifier in the iterator is user-visible and 4225 -- must be visible in the debugger. 4226 4227 Set_Debug_Info_Needed (Id); 4228 4229 -- If the container does not have a variable indexing aspect, 4230 -- the element is a constant in the loop. The container itself 4231 -- may be constant, in which case the element is a constant as 4232 -- well. The container has been rewritten as a call to Iterate, 4233 -- so examine original node. 4234 4235 if No (Find_Value_Of_Aspect 4236 (Container_Typ, Aspect_Variable_Indexing)) 4237 or else not Is_Variable (Original_Node (Container)) 4238 then 4239 Set_Ekind (Id, E_Constant); 4240 end if; 4241 4242 Prepend_To (Stats, Decl); 4243 end Handle_Of; 4244 4245 -- X in Iterate (S) : type of iterator is type of explicitly given 4246 -- Iterate function, and the loop variable is the cursor. It will be 4247 -- assigned in the loop and must be a variable. 4248 4249 else 4250 Iter_Type := Etype (Name (I_Spec)); 4251 4252 -- The iterator type, which is a class-wide type, may itself be 4253 -- derived locally, so the desired instantiation is the scope of 4254 -- the root type of the iterator type, as in the "of" case. 4255 4256 Iter_Pack := Scope (Root_Type (Etype (Iter_Type))); 4257 Cursor := Id; 4258 end if; 4259 4260 Iterator := Make_Temporary (Loc, 'I'); 4261 4262 -- For both iterator forms, add a call to the step operation to advance 4263 -- the cursor. Generate: 4264 4265 -- Cursor := Iterator.Next (Cursor); 4266 4267 -- or else 4268 4269 -- Cursor := Next (Cursor); 4270 4271 if Present (Fast_Element_Access_Op) and then Present (Fast_Step_Op) then 4272 declare 4273 Curs_Name : constant Node_Id := New_Occurrence_Of (Cursor, Loc); 4274 Step_Call : Node_Id; 4275 4276 begin 4277 Step_Call := 4278 Make_Procedure_Call_Statement (Loc, 4279 Name => 4280 New_Occurrence_Of (Fast_Step_Op, Loc), 4281 Parameter_Associations => New_List (Curs_Name)); 4282 4283 Append_To (Stats, Step_Call); 4284 Set_Assignment_OK (Curs_Name); 4285 end; 4286 4287 else 4288 declare 4289 Rhs : Node_Id; 4290 4291 begin 4292 Rhs := 4293 Make_Function_Call (Loc, 4294 Name => 4295 Make_Selected_Component (Loc, 4296 Prefix => New_Occurrence_Of (Iterator, Loc), 4297 Selector_Name => Make_Identifier (Loc, Name_Step)), 4298 Parameter_Associations => New_List ( 4299 New_Occurrence_Of (Cursor, Loc))); 4300 4301 Append_To (Stats, 4302 Make_Assignment_Statement (Loc, 4303 Name => New_Occurrence_Of (Cursor, Loc), 4304 Expression => Rhs)); 4305 Set_Assignment_OK (Name (Last (Stats))); 4306 end; 4307 end if; 4308 4309 -- Generate: 4310 -- while Has_Element (Cursor) loop 4311 -- <Stats> 4312 -- end loop; 4313 4314 -- Has_Element is the second actual in the iterator package 4315 4316 New_Loop := 4317 Make_Loop_Statement (Loc, 4318 Iteration_Scheme => 4319 Make_Iteration_Scheme (Loc, 4320 Condition => 4321 Make_Function_Call (Loc, 4322 Name => 4323 New_Occurrence_Of 4324 (Next_Entity (First_Entity (Iter_Pack)), Loc), 4325 Parameter_Associations => New_List ( 4326 New_Occurrence_Of (Cursor, Loc)))), 4327 4328 Statements => Stats, 4329 End_Label => Empty); 4330 4331 -- If present, preserve identifier of loop, which can be used in an exit 4332 -- statement in the body. 4333 4334 if Present (Identifier (N)) then 4335 Set_Identifier (New_Loop, Relocate_Node (Identifier (N))); 4336 end if; 4337 4338 -- Create the declarations for Iterator and cursor and insert them 4339 -- before the source loop. Given that the domain of iteration is already 4340 -- an entity, the iterator is just a renaming of that entity. Possible 4341 -- optimization ??? 4342 4343 Insert_Action (N, 4344 Make_Object_Renaming_Declaration (Loc, 4345 Defining_Identifier => Iterator, 4346 Subtype_Mark => New_Occurrence_Of (Iter_Type, Loc), 4347 Name => Relocate_Node (Name (I_Spec)))); 4348 4349 -- Create declaration for cursor 4350 4351 declare 4352 Cursor_Decl : constant Node_Id := 4353 Make_Object_Declaration (Loc, 4354 Defining_Identifier => Cursor, 4355 Object_Definition => 4356 New_Occurrence_Of (Etype (Cursor), Loc), 4357 Expression => 4358 Make_Selected_Component (Loc, 4359 Prefix => 4360 New_Occurrence_Of (Iterator, Loc), 4361 Selector_Name => 4362 Make_Identifier (Loc, Name_Init))); 4363 4364 begin 4365 -- The cursor is only modified in expanded code, so it appears 4366 -- as unassigned to the warning machinery. We must suppress this 4367 -- spurious warning explicitly. The cursor's kind is that of the 4368 -- original loop parameter (it is a constant if the domain of 4369 -- iteration is constant). 4370 4371 Set_Warnings_Off (Cursor); 4372 Set_Assignment_OK (Cursor_Decl); 4373 4374 Insert_Action (N, Cursor_Decl); 4375 Set_Ekind (Cursor, Id_Kind); 4376 end; 4377 4378 -- If the range of iteration is given by a function call that returns 4379 -- a container, the finalization actions have been saved in the 4380 -- Condition_Actions of the iterator. Insert them now at the head of 4381 -- the loop. 4382 4383 if Present (Condition_Actions (Isc)) then 4384 Insert_List_Before (N, Condition_Actions (Isc)); 4385 end if; 4386 4387 Rewrite (N, New_Loop); 4388 Analyze (N); 4389 end Expand_Iterator_Loop_Over_Container; 4390 4391 ----------------------------- 4392 -- Expand_N_Loop_Statement -- 4393 ----------------------------- 4394 4395 -- 1. Remove null loop entirely 4396 -- 2. Deal with while condition for C/Fortran boolean 4397 -- 3. Deal with loops with a non-standard enumeration type range 4398 -- 4. Deal with while loops where Condition_Actions is set 4399 -- 5. Deal with loops over predicated subtypes 4400 -- 6. Deal with loops with iterators over arrays and containers 4401 -- 7. Insert polling call if required 4402 4403 procedure Expand_N_Loop_Statement (N : Node_Id) is 4404 Loc : constant Source_Ptr := Sloc (N); 4405 Scheme : constant Node_Id := Iteration_Scheme (N); 4406 Stmt : Node_Id; 4407 4408 begin 4409 -- Delete null loop 4410 4411 if Is_Null_Loop (N) then 4412 Rewrite (N, Make_Null_Statement (Loc)); 4413 return; 4414 end if; 4415 4416 -- Deal with condition for C/Fortran Boolean 4417 4418 if Present (Scheme) then 4419 Adjust_Condition (Condition (Scheme)); 4420 end if; 4421 4422 -- Generate polling call 4423 4424 if Is_Non_Empty_List (Statements (N)) then 4425 Generate_Poll_Call (First (Statements (N))); 4426 end if; 4427 4428 -- Nothing more to do for plain loop with no iteration scheme 4429 4430 if No (Scheme) then 4431 null; 4432 4433 -- Case of for loop (Loop_Parameter_Specification present) 4434 4435 -- Note: we do not have to worry about validity checking of the for loop 4436 -- range bounds here, since they were frozen with constant declarations 4437 -- and it is during that process that the validity checking is done. 4438 4439 elsif Present (Loop_Parameter_Specification (Scheme)) then 4440 declare 4441 LPS : constant Node_Id := 4442 Loop_Parameter_Specification (Scheme); 4443 Loop_Id : constant Entity_Id := Defining_Identifier (LPS); 4444 Ltype : constant Entity_Id := Etype (Loop_Id); 4445 Btype : constant Entity_Id := Base_Type (Ltype); 4446 Expr : Node_Id; 4447 Decls : List_Id; 4448 New_Id : Entity_Id; 4449 4450 begin 4451 -- Deal with loop over predicates 4452 4453 if Is_Discrete_Type (Ltype) 4454 and then Present (Predicate_Function (Ltype)) 4455 then 4456 Expand_Predicated_Loop (N); 4457 4458 -- Handle the case where we have a for loop with the range type 4459 -- being an enumeration type with non-standard representation. 4460 -- In this case we expand: 4461 4462 -- for x in [reverse] a .. b loop 4463 -- ... 4464 -- end loop; 4465 4466 -- to 4467 4468 -- for xP in [reverse] integer 4469 -- range etype'Pos (a) .. etype'Pos (b) 4470 -- loop 4471 -- declare 4472 -- x : constant etype := Pos_To_Rep (xP); 4473 -- begin 4474 -- ... 4475 -- end; 4476 -- end loop; 4477 4478 elsif Is_Enumeration_Type (Btype) 4479 and then Present (Enum_Pos_To_Rep (Btype)) 4480 then 4481 New_Id := 4482 Make_Defining_Identifier (Loc, 4483 Chars => New_External_Name (Chars (Loop_Id), 'P')); 4484 4485 -- If the type has a contiguous representation, successive 4486 -- values can be generated as offsets from the first literal. 4487 4488 if Has_Contiguous_Rep (Btype) then 4489 Expr := 4490 Unchecked_Convert_To (Btype, 4491 Make_Op_Add (Loc, 4492 Left_Opnd => 4493 Make_Integer_Literal (Loc, 4494 Enumeration_Rep (First_Literal (Btype))), 4495 Right_Opnd => New_Occurrence_Of (New_Id, Loc))); 4496 else 4497 -- Use the constructed array Enum_Pos_To_Rep 4498 4499 Expr := 4500 Make_Indexed_Component (Loc, 4501 Prefix => 4502 New_Occurrence_Of (Enum_Pos_To_Rep (Btype), Loc), 4503 Expressions => 4504 New_List (New_Occurrence_Of (New_Id, Loc))); 4505 end if; 4506 4507 -- Build declaration for loop identifier 4508 4509 Decls := 4510 New_List ( 4511 Make_Object_Declaration (Loc, 4512 Defining_Identifier => Loop_Id, 4513 Constant_Present => True, 4514 Object_Definition => New_Occurrence_Of (Ltype, Loc), 4515 Expression => Expr)); 4516 4517 Rewrite (N, 4518 Make_Loop_Statement (Loc, 4519 Identifier => Identifier (N), 4520 4521 Iteration_Scheme => 4522 Make_Iteration_Scheme (Loc, 4523 Loop_Parameter_Specification => 4524 Make_Loop_Parameter_Specification (Loc, 4525 Defining_Identifier => New_Id, 4526 Reverse_Present => Reverse_Present (LPS), 4527 4528 Discrete_Subtype_Definition => 4529 Make_Subtype_Indication (Loc, 4530 4531 Subtype_Mark => 4532 New_Occurrence_Of (Standard_Natural, Loc), 4533 4534 Constraint => 4535 Make_Range_Constraint (Loc, 4536 Range_Expression => 4537 Make_Range (Loc, 4538 4539 Low_Bound => 4540 Make_Attribute_Reference (Loc, 4541 Prefix => 4542 New_Occurrence_Of (Btype, Loc), 4543 4544 Attribute_Name => Name_Pos, 4545 4546 Expressions => New_List ( 4547 Relocate_Node 4548 (Type_Low_Bound (Ltype)))), 4549 4550 High_Bound => 4551 Make_Attribute_Reference (Loc, 4552 Prefix => 4553 New_Occurrence_Of (Btype, Loc), 4554 4555 Attribute_Name => Name_Pos, 4556 4557 Expressions => New_List ( 4558 Relocate_Node 4559 (Type_High_Bound 4560 (Ltype))))))))), 4561 4562 Statements => New_List ( 4563 Make_Block_Statement (Loc, 4564 Declarations => Decls, 4565 Handled_Statement_Sequence => 4566 Make_Handled_Sequence_Of_Statements (Loc, 4567 Statements => Statements (N)))), 4568 4569 End_Label => End_Label (N))); 4570 4571 -- The loop parameter's entity must be removed from the loop 4572 -- scope's entity list and rendered invisible, since it will 4573 -- now be located in the new block scope. Any other entities 4574 -- already associated with the loop scope, such as the loop 4575 -- parameter's subtype, will remain there. 4576 4577 -- In an element loop, the loop will contain a declaration for 4578 -- a cursor variable; otherwise the loop id is the first entity 4579 -- in the scope constructed for the loop. 4580 4581 if Comes_From_Source (Loop_Id) then 4582 pragma Assert (First_Entity (Scope (Loop_Id)) = Loop_Id); 4583 null; 4584 end if; 4585 4586 Set_First_Entity (Scope (Loop_Id), Next_Entity (Loop_Id)); 4587 Remove_Homonym (Loop_Id); 4588 4589 if Last_Entity (Scope (Loop_Id)) = Loop_Id then 4590 Set_Last_Entity (Scope (Loop_Id), Empty); 4591 end if; 4592 4593 Analyze (N); 4594 4595 -- Nothing to do with other cases of for loops 4596 4597 else 4598 null; 4599 end if; 4600 end; 4601 4602 -- Second case, if we have a while loop with Condition_Actions set, then 4603 -- we change it into a plain loop: 4604 4605 -- while C loop 4606 -- ... 4607 -- end loop; 4608 4609 -- changed to: 4610 4611 -- loop 4612 -- <<condition actions>> 4613 -- exit when not C; 4614 -- ... 4615 -- end loop 4616 4617 elsif Present (Scheme) 4618 and then Present (Condition_Actions (Scheme)) 4619 and then Present (Condition (Scheme)) 4620 then 4621 declare 4622 ES : Node_Id; 4623 4624 begin 4625 ES := 4626 Make_Exit_Statement (Sloc (Condition (Scheme)), 4627 Condition => 4628 Make_Op_Not (Sloc (Condition (Scheme)), 4629 Right_Opnd => Condition (Scheme))); 4630 4631 Prepend (ES, Statements (N)); 4632 Insert_List_Before (ES, Condition_Actions (Scheme)); 4633 4634 -- This is not an implicit loop, since it is generated in response 4635 -- to the loop statement being processed. If this is itself 4636 -- implicit, the restriction has already been checked. If not, 4637 -- it is an explicit loop. 4638 4639 Rewrite (N, 4640 Make_Loop_Statement (Sloc (N), 4641 Identifier => Identifier (N), 4642 Statements => Statements (N), 4643 End_Label => End_Label (N))); 4644 4645 Analyze (N); 4646 end; 4647 4648 -- Here to deal with iterator case 4649 4650 elsif Present (Scheme) 4651 and then Present (Iterator_Specification (Scheme)) 4652 then 4653 Expand_Iterator_Loop (N); 4654 4655 -- An iterator loop may generate renaming declarations for elements 4656 -- that require debug information. This is the case in particular 4657 -- with element iterators, where debug information must be generated 4658 -- for the temporary that holds the element value. These temporaries 4659 -- are created within a transient block whose local declarations are 4660 -- transferred to the loop, which now has nontrivial local objects. 4661 4662 if Nkind (N) = N_Loop_Statement 4663 and then Present (Identifier (N)) 4664 then 4665 Qualify_Entity_Names (N); 4666 end if; 4667 end if; 4668 4669 -- When the iteration scheme mentiones attribute 'Loop_Entry, the loop 4670 -- is transformed into a conditional block where the original loop is 4671 -- the sole statement. Inspect the statements of the nested loop for 4672 -- controlled objects. 4673 4674 Stmt := N; 4675 4676 if Subject_To_Loop_Entry_Attributes (Stmt) then 4677 Stmt := Find_Loop_In_Conditional_Block (Stmt); 4678 end if; 4679 4680 Process_Statements_For_Controlled_Objects (Stmt); 4681 end Expand_N_Loop_Statement; 4682 4683 ---------------------------- 4684 -- Expand_Predicated_Loop -- 4685 ---------------------------- 4686 4687 -- Note: the expander can handle generation of loops over predicated 4688 -- subtypes for both the dynamic and static cases. Depending on what 4689 -- we decide is allowed in Ada 2012 mode and/or extensions allowed 4690 -- mode, the semantic analyzer may disallow one or both forms. 4691 4692 procedure Expand_Predicated_Loop (N : Node_Id) is 4693 Loc : constant Source_Ptr := Sloc (N); 4694 Isc : constant Node_Id := Iteration_Scheme (N); 4695 LPS : constant Node_Id := Loop_Parameter_Specification (Isc); 4696 Loop_Id : constant Entity_Id := Defining_Identifier (LPS); 4697 Ltype : constant Entity_Id := Etype (Loop_Id); 4698 Stat : constant List_Id := Static_Discrete_Predicate (Ltype); 4699 Stmts : constant List_Id := Statements (N); 4700 4701 begin 4702 -- Case of iteration over non-static predicate, should not be possible 4703 -- since this is not allowed by the semantics and should have been 4704 -- caught during analysis of the loop statement. 4705 4706 if No (Stat) then 4707 raise Program_Error; 4708 4709 -- If the predicate list is empty, that corresponds to a predicate of 4710 -- False, in which case the loop won't run at all, and we rewrite the 4711 -- entire loop as a null statement. 4712 4713 elsif Is_Empty_List (Stat) then 4714 Rewrite (N, Make_Null_Statement (Loc)); 4715 Analyze (N); 4716 4717 -- For expansion over a static predicate we generate the following 4718 4719 -- declare 4720 -- J : Ltype := min-val; 4721 -- begin 4722 -- loop 4723 -- body 4724 -- case J is 4725 -- when endpoint => J := startpoint; 4726 -- when endpoint => J := startpoint; 4727 -- ... 4728 -- when max-val => exit; 4729 -- when others => J := Lval'Succ (J); 4730 -- end case; 4731 -- end loop; 4732 -- end; 4733 4734 -- with min-val replaced by max-val and Succ replaced by Pred if the 4735 -- loop parameter specification carries a Reverse indicator. 4736 4737 -- To make this a little clearer, let's take a specific example: 4738 4739 -- type Int is range 1 .. 10; 4740 -- subtype StaticP is Int with 4741 -- predicate => StaticP in 3 | 10 | 5 .. 7; 4742 -- ... 4743 -- for L in StaticP loop 4744 -- Put_Line ("static:" & J'Img); 4745 -- end loop; 4746 4747 -- In this case, the loop is transformed into 4748 4749 -- begin 4750 -- J : L := 3; 4751 -- loop 4752 -- body 4753 -- case J is 4754 -- when 3 => J := 5; 4755 -- when 7 => J := 10; 4756 -- when 10 => exit; 4757 -- when others => J := L'Succ (J); 4758 -- end case; 4759 -- end loop; 4760 -- end; 4761 4762 -- In addition, if the loop specification is given by a subtype 4763 -- indication that constrains a predicated type, the bounds of 4764 -- iteration are given by those of the subtype indication. 4765 4766 else 4767 Static_Predicate : declare 4768 S : Node_Id; 4769 D : Node_Id; 4770 P : Node_Id; 4771 Alts : List_Id; 4772 Cstm : Node_Id; 4773 4774 -- If the domain is an itype, note the bounds of its range. 4775 4776 L_Hi : Node_Id := Empty; 4777 L_Lo : Node_Id := Empty; 4778 4779 function Lo_Val (N : Node_Id) return Node_Id; 4780 -- Given static expression or static range, returns an identifier 4781 -- whose value is the low bound of the expression value or range. 4782 4783 function Hi_Val (N : Node_Id) return Node_Id; 4784 -- Given static expression or static range, returns an identifier 4785 -- whose value is the high bound of the expression value or range. 4786 4787 ------------ 4788 -- Hi_Val -- 4789 ------------ 4790 4791 function Hi_Val (N : Node_Id) return Node_Id is 4792 begin 4793 if Is_OK_Static_Expression (N) then 4794 return New_Copy (N); 4795 else 4796 pragma Assert (Nkind (N) = N_Range); 4797 return New_Copy (High_Bound (N)); 4798 end if; 4799 end Hi_Val; 4800 4801 ------------ 4802 -- Lo_Val -- 4803 ------------ 4804 4805 function Lo_Val (N : Node_Id) return Node_Id is 4806 begin 4807 if Is_OK_Static_Expression (N) then 4808 return New_Copy (N); 4809 else 4810 pragma Assert (Nkind (N) = N_Range); 4811 return New_Copy (Low_Bound (N)); 4812 end if; 4813 end Lo_Val; 4814 4815 -- Start of processing for Static_Predicate 4816 4817 begin 4818 -- Convert loop identifier to normal variable and reanalyze it so 4819 -- that this conversion works. We have to use the same defining 4820 -- identifier, since there may be references in the loop body. 4821 4822 Set_Analyzed (Loop_Id, False); 4823 Set_Ekind (Loop_Id, E_Variable); 4824 4825 -- In most loops the loop variable is assigned in various 4826 -- alternatives in the body. However, in the rare case when 4827 -- the range specifies a single element, the loop variable 4828 -- may trigger a spurious warning that is could be constant. 4829 -- This warning might as well be suppressed. 4830 4831 Set_Warnings_Off (Loop_Id); 4832 4833 if Is_Itype (Ltype) then 4834 L_Hi := High_Bound (Scalar_Range (Ltype)); 4835 L_Lo := Low_Bound (Scalar_Range (Ltype)); 4836 end if; 4837 4838 -- Loop to create branches of case statement 4839 4840 Alts := New_List; 4841 4842 if Reverse_Present (LPS) then 4843 4844 -- Initial value is largest value in predicate. 4845 4846 if Is_Itype (Ltype) then 4847 D := 4848 Make_Object_Declaration (Loc, 4849 Defining_Identifier => Loop_Id, 4850 Object_Definition => New_Occurrence_Of (Ltype, Loc), 4851 Expression => L_Hi); 4852 4853 else 4854 D := 4855 Make_Object_Declaration (Loc, 4856 Defining_Identifier => Loop_Id, 4857 Object_Definition => New_Occurrence_Of (Ltype, Loc), 4858 Expression => Hi_Val (Last (Stat))); 4859 end if; 4860 4861 P := Last (Stat); 4862 while Present (P) loop 4863 if No (Prev (P)) then 4864 S := Make_Exit_Statement (Loc); 4865 else 4866 S := 4867 Make_Assignment_Statement (Loc, 4868 Name => New_Occurrence_Of (Loop_Id, Loc), 4869 Expression => Hi_Val (Prev (P))); 4870 Set_Suppress_Assignment_Checks (S); 4871 end if; 4872 4873 Append_To (Alts, 4874 Make_Case_Statement_Alternative (Loc, 4875 Statements => New_List (S), 4876 Discrete_Choices => New_List (Lo_Val (P)))); 4877 4878 Prev (P); 4879 end loop; 4880 4881 if Is_Itype (Ltype) 4882 and then Is_OK_Static_Expression (L_Lo) 4883 and then 4884 Expr_Value (L_Lo) /= Expr_Value (Lo_Val (First (Stat))) 4885 then 4886 Append_To (Alts, 4887 Make_Case_Statement_Alternative (Loc, 4888 Statements => New_List (Make_Exit_Statement (Loc)), 4889 Discrete_Choices => New_List (L_Lo))); 4890 end if; 4891 4892 else 4893 -- Initial value is smallest value in predicate 4894 4895 if Is_Itype (Ltype) then 4896 D := 4897 Make_Object_Declaration (Loc, 4898 Defining_Identifier => Loop_Id, 4899 Object_Definition => New_Occurrence_Of (Ltype, Loc), 4900 Expression => L_Lo); 4901 else 4902 D := 4903 Make_Object_Declaration (Loc, 4904 Defining_Identifier => Loop_Id, 4905 Object_Definition => New_Occurrence_Of (Ltype, Loc), 4906 Expression => Lo_Val (First (Stat))); 4907 end if; 4908 4909 P := First (Stat); 4910 while Present (P) loop 4911 if No (Next (P)) then 4912 S := Make_Exit_Statement (Loc); 4913 else 4914 S := 4915 Make_Assignment_Statement (Loc, 4916 Name => New_Occurrence_Of (Loop_Id, Loc), 4917 Expression => Lo_Val (Next (P))); 4918 Set_Suppress_Assignment_Checks (S); 4919 end if; 4920 4921 Append_To (Alts, 4922 Make_Case_Statement_Alternative (Loc, 4923 Statements => New_List (S), 4924 Discrete_Choices => New_List (Hi_Val (P)))); 4925 4926 Next (P); 4927 end loop; 4928 4929 if Is_Itype (Ltype) 4930 and then Is_OK_Static_Expression (L_Hi) 4931 and then 4932 Expr_Value (L_Hi) /= Expr_Value (Lo_Val (Last (Stat))) 4933 then 4934 Append_To (Alts, 4935 Make_Case_Statement_Alternative (Loc, 4936 Statements => New_List (Make_Exit_Statement (Loc)), 4937 Discrete_Choices => New_List (L_Hi))); 4938 end if; 4939 end if; 4940 4941 -- Add others choice 4942 4943 declare 4944 Name_Next : Name_Id; 4945 4946 begin 4947 if Reverse_Present (LPS) then 4948 Name_Next := Name_Pred; 4949 else 4950 Name_Next := Name_Succ; 4951 end if; 4952 4953 S := 4954 Make_Assignment_Statement (Loc, 4955 Name => New_Occurrence_Of (Loop_Id, Loc), 4956 Expression => 4957 Make_Attribute_Reference (Loc, 4958 Prefix => New_Occurrence_Of (Ltype, Loc), 4959 Attribute_Name => Name_Next, 4960 Expressions => New_List ( 4961 New_Occurrence_Of (Loop_Id, Loc)))); 4962 Set_Suppress_Assignment_Checks (S); 4963 end; 4964 4965 Append_To (Alts, 4966 Make_Case_Statement_Alternative (Loc, 4967 Discrete_Choices => New_List (Make_Others_Choice (Loc)), 4968 Statements => New_List (S))); 4969 4970 -- Construct case statement and append to body statements 4971 4972 Cstm := 4973 Make_Case_Statement (Loc, 4974 Expression => New_Occurrence_Of (Loop_Id, Loc), 4975 Alternatives => Alts); 4976 Append_To (Stmts, Cstm); 4977 4978 -- Rewrite the loop 4979 4980 Set_Suppress_Assignment_Checks (D); 4981 4982 Rewrite (N, 4983 Make_Block_Statement (Loc, 4984 Declarations => New_List (D), 4985 Handled_Statement_Sequence => 4986 Make_Handled_Sequence_Of_Statements (Loc, 4987 Statements => New_List ( 4988 Make_Loop_Statement (Loc, 4989 Statements => Stmts, 4990 End_Label => Empty))))); 4991 4992 Analyze (N); 4993 end Static_Predicate; 4994 end if; 4995 end Expand_Predicated_Loop; 4996 4997 ------------------------------ 4998 -- Make_Tag_Ctrl_Assignment -- 4999 ------------------------------ 5000 5001 function Make_Tag_Ctrl_Assignment (N : Node_Id) return List_Id is 5002 Asn : constant Node_Id := Relocate_Node (N); 5003 L : constant Node_Id := Name (N); 5004 Loc : constant Source_Ptr := Sloc (N); 5005 Res : constant List_Id := New_List; 5006 T : constant Entity_Id := Underlying_Type (Etype (L)); 5007 5008 Comp_Asn : constant Boolean := Is_Fully_Repped_Tagged_Type (T); 5009 Ctrl_Act : constant Boolean := Needs_Finalization (T) 5010 and then not No_Ctrl_Actions (N); 5011 Save_Tag : constant Boolean := Is_Tagged_Type (T) 5012 and then not Comp_Asn 5013 and then not No_Ctrl_Actions (N) 5014 and then Tagged_Type_Expansion; 5015 Adj_Call : Node_Id; 5016 Fin_Call : Node_Id; 5017 Tag_Id : Entity_Id; 5018 5019 begin 5020 -- Finalize the target of the assignment when controlled 5021 5022 -- We have two exceptions here: 5023 5024 -- 1. If we are in an init proc since it is an initialization more 5025 -- than an assignment. 5026 5027 -- 2. If the left-hand side is a temporary that was not initialized 5028 -- (or the parent part of a temporary since it is the case in 5029 -- extension aggregates). Such a temporary does not come from 5030 -- source. We must examine the original node for the prefix, because 5031 -- it may be a component of an entry formal, in which case it has 5032 -- been rewritten and does not appear to come from source either. 5033 5034 -- Case of init proc 5035 5036 if not Ctrl_Act then 5037 null; 5038 5039 -- The left-hand side is an uninitialized temporary object 5040 5041 elsif Nkind (L) = N_Type_Conversion 5042 and then Is_Entity_Name (Expression (L)) 5043 and then Nkind (Parent (Entity (Expression (L)))) = 5044 N_Object_Declaration 5045 and then No_Initialization (Parent (Entity (Expression (L)))) 5046 then 5047 null; 5048 5049 else 5050 Fin_Call := 5051 Make_Final_Call 5052 (Obj_Ref => Duplicate_Subexpr_No_Checks (L), 5053 Typ => Etype (L)); 5054 5055 if Present (Fin_Call) then 5056 Append_To (Res, Fin_Call); 5057 end if; 5058 end if; 5059 5060 -- Save the Tag in a local variable Tag_Id 5061 5062 if Save_Tag then 5063 Tag_Id := Make_Temporary (Loc, 'A'); 5064 5065 Append_To (Res, 5066 Make_Object_Declaration (Loc, 5067 Defining_Identifier => Tag_Id, 5068 Object_Definition => New_Occurrence_Of (RTE (RE_Tag), Loc), 5069 Expression => 5070 Make_Selected_Component (Loc, 5071 Prefix => Duplicate_Subexpr_No_Checks (L), 5072 Selector_Name => 5073 New_Occurrence_Of (First_Tag_Component (T), Loc)))); 5074 5075 -- Otherwise Tag_Id is not used 5076 5077 else 5078 Tag_Id := Empty; 5079 end if; 5080 5081 -- If the tagged type has a full rep clause, expand the assignment into 5082 -- component-wise assignments. Mark the node as unanalyzed in order to 5083 -- generate the proper code and propagate this scenario by setting a 5084 -- flag to avoid infinite recursion. 5085 5086 if Comp_Asn then 5087 Set_Analyzed (Asn, False); 5088 Set_Componentwise_Assignment (Asn, True); 5089 end if; 5090 5091 Append_To (Res, Asn); 5092 5093 -- Restore the tag 5094 5095 if Save_Tag then 5096 Append_To (Res, 5097 Make_Assignment_Statement (Loc, 5098 Name => 5099 Make_Selected_Component (Loc, 5100 Prefix => Duplicate_Subexpr_No_Checks (L), 5101 Selector_Name => 5102 New_Occurrence_Of (First_Tag_Component (T), Loc)), 5103 Expression => New_Occurrence_Of (Tag_Id, Loc))); 5104 end if; 5105 5106 -- Adjust the target after the assignment when controlled (not in the 5107 -- init proc since it is an initialization more than an assignment). 5108 5109 if Ctrl_Act then 5110 Adj_Call := 5111 Make_Adjust_Call 5112 (Obj_Ref => Duplicate_Subexpr_Move_Checks (L), 5113 Typ => Etype (L)); 5114 5115 if Present (Adj_Call) then 5116 Append_To (Res, Adj_Call); 5117 end if; 5118 end if; 5119 5120 return Res; 5121 5122 exception 5123 5124 -- Could use comment here ??? 5125 5126 when RE_Not_Available => 5127 return Empty_List; 5128 end Make_Tag_Ctrl_Assignment; 5129 5130end Exp_Ch5; 5131