1------------------------------------------------------------------------------ 2-- -- 3-- GNAT COMPILER COMPONENTS -- 4-- -- 5-- E X P _ C H 5 -- 6-- -- 7-- B o d y -- 8-- -- 9-- Copyright (C) 1992-2003, 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 2, 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 COPYING. If not, write -- 19-- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, -- 20-- MA 02111-1307, USA. -- 21-- -- 22-- GNAT was originally developed by the GNAT team at New York University. -- 23-- Extensive contributions were provided by Ada Core Technologies Inc. -- 24-- -- 25------------------------------------------------------------------------------ 26 27with Atree; use Atree; 28with Checks; use Checks; 29with Einfo; use Einfo; 30with Exp_Aggr; use Exp_Aggr; 31with Exp_Ch7; use Exp_Ch7; 32with Exp_Ch11; use Exp_Ch11; 33with Exp_Dbug; use Exp_Dbug; 34with Exp_Pakd; use Exp_Pakd; 35with Exp_Util; use Exp_Util; 36with Hostparm; use Hostparm; 37with Nlists; use Nlists; 38with Nmake; use Nmake; 39with Opt; use Opt; 40with Restrict; use Restrict; 41with Rtsfind; use Rtsfind; 42with Sinfo; use Sinfo; 43with Sem; use Sem; 44with Sem_Ch8; use Sem_Ch8; 45with Sem_Ch13; use Sem_Ch13; 46with Sem_Eval; use Sem_Eval; 47with Sem_Res; use Sem_Res; 48with Sem_Util; use Sem_Util; 49with Snames; use Snames; 50with Stand; use Stand; 51with Stringt; use Stringt; 52with Tbuild; use Tbuild; 53with Ttypes; use Ttypes; 54with Uintp; use Uintp; 55with Validsw; use Validsw; 56 57package body Exp_Ch5 is 58 59 function Change_Of_Representation (N : Node_Id) return Boolean; 60 -- Determine if the right hand side of the assignment N is a type 61 -- conversion which requires a change of representation. Called 62 -- only for the array and record cases. 63 64 procedure Expand_Assign_Array (N : Node_Id; Rhs : Node_Id); 65 -- N is an assignment which assigns an array value. This routine process 66 -- the various special cases and checks required for such assignments, 67 -- including change of representation. Rhs is normally simply the right 68 -- hand side of the assignment, except that if the right hand side is 69 -- a type conversion or a qualified expression, then the Rhs is the 70 -- actual expression inside any such type conversions or qualifications. 71 72 function Expand_Assign_Array_Loop 73 (N : Node_Id; 74 Larray : Entity_Id; 75 Rarray : Entity_Id; 76 L_Type : Entity_Id; 77 R_Type : Entity_Id; 78 Ndim : Pos; 79 Rev : Boolean) return Node_Id; 80 -- N is an assignment statement which assigns an array value. This routine 81 -- expands the assignment into a loop (or nested loops for the case of a 82 -- multi-dimensional array) to do the assignment component by component. 83 -- Larray and Rarray are the entities of the actual arrays on the left 84 -- hand and right hand sides. L_Type and R_Type are the types of these 85 -- arrays (which may not be the same, due to either sliding, or to a 86 -- change of representation case). Ndim is the number of dimensions and 87 -- the parameter Rev indicates if the loops run normally (Rev = False), 88 -- or reversed (Rev = True). The value returned is the constructed 89 -- loop statement. Auxiliary declarations are inserted before node N 90 -- using the standard Insert_Actions mechanism. 91 92 procedure Expand_Assign_Record (N : Node_Id); 93 -- N is an assignment of a non-tagged record value. This routine handles 94 -- the case where the assignment must be made component by component, 95 -- either because the target is not byte aligned, or there is a change 96 -- of representation. 97 98 function Make_Tag_Ctrl_Assignment (N : Node_Id) return List_Id; 99 -- Generate the necessary code for controlled and Tagged assignment, 100 -- that is to say, finalization of the target before, adjustement of 101 -- the target after and save and restore of the tag and finalization 102 -- pointers which are not 'part of the value' and must not be changed 103 -- upon assignment. N is the original Assignment node. 104 105 function Possible_Bit_Aligned_Component (N : Node_Id) return Boolean; 106 -- This function is used in processing the assignment of a record or 107 -- indexed component. The argument N is either the left hand or right 108 -- hand side of an assignment, and this function determines if there 109 -- is a record component reference where the record may be bit aligned 110 -- in a manner that causes trouble for the back end (see description 111 -- of Sem_Util.Component_May_Be_Bit_Aligned for further details). 112 113 ------------------------------ 114 -- Change_Of_Representation -- 115 ------------------------------ 116 117 function Change_Of_Representation (N : Node_Id) return Boolean is 118 Rhs : constant Node_Id := Expression (N); 119 begin 120 return 121 Nkind (Rhs) = N_Type_Conversion 122 and then 123 not Same_Representation (Etype (Rhs), Etype (Expression (Rhs))); 124 end Change_Of_Representation; 125 126 ------------------------- 127 -- Expand_Assign_Array -- 128 ------------------------- 129 130 -- There are two issues here. First, do we let Gigi do a block move, or 131 -- do we expand out into a loop? Second, we need to set the two flags 132 -- Forwards_OK and Backwards_OK which show whether the block move (or 133 -- corresponding loops) can be legitimately done in a forwards (low to 134 -- high) or backwards (high to low) manner. 135 136 procedure Expand_Assign_Array (N : Node_Id; Rhs : Node_Id) is 137 Loc : constant Source_Ptr := Sloc (N); 138 139 Lhs : constant Node_Id := Name (N); 140 141 Act_Lhs : constant Node_Id := Get_Referenced_Object (Lhs); 142 Act_Rhs : Node_Id := Get_Referenced_Object (Rhs); 143 144 L_Type : constant Entity_Id := 145 Underlying_Type (Get_Actual_Subtype (Act_Lhs)); 146 R_Type : Entity_Id := 147 Underlying_Type (Get_Actual_Subtype (Act_Rhs)); 148 149 L_Slice : constant Boolean := Nkind (Act_Lhs) = N_Slice; 150 R_Slice : constant Boolean := Nkind (Act_Rhs) = N_Slice; 151 152 Crep : constant Boolean := Change_Of_Representation (N); 153 154 Larray : Node_Id; 155 Rarray : Node_Id; 156 157 Ndim : constant Pos := Number_Dimensions (L_Type); 158 159 Loop_Required : Boolean := False; 160 -- This switch is set to True if the array move must be done using 161 -- an explicit front end generated loop. 162 163 function Has_Address_Clause (Exp : Node_Id) return Boolean; 164 -- Test if Exp is a reference to an array whose declaration has 165 -- an address clause, or it is a slice of such an array. 166 167 function Is_Formal_Array (Exp : Node_Id) return Boolean; 168 -- Test if Exp is a reference to an array which is either a formal 169 -- parameter or a slice of a formal parameter. These are the cases 170 -- where hidden aliasing can occur. 171 172 function Is_Non_Local_Array (Exp : Node_Id) return Boolean; 173 -- Determine if Exp is a reference to an array variable which is other 174 -- than an object defined in the current scope, or a slice of such 175 -- an object. Such objects can be aliased to parameters (unlike local 176 -- array references). 177 178 function Possible_Unaligned_Slice (Arg : Node_Id) return Boolean; 179 -- Returns True if Arg (either the left or right hand side of the 180 -- assignment) is a slice that could be unaligned wrt the array type. 181 -- This is true if Arg is a component of a packed record, or is 182 -- a record component to which a component clause applies. This 183 -- is a little pessimistic, but the result of an unnecessary 184 -- decision that something is possibly unaligned is only to 185 -- generate a front end loop, which is not so terrible. 186 -- It would really be better if backend handled this ??? 187 188 ------------------------ 189 -- Has_Address_Clause -- 190 ------------------------ 191 192 function Has_Address_Clause (Exp : Node_Id) return Boolean is 193 begin 194 return 195 (Is_Entity_Name (Exp) and then 196 Present (Address_Clause (Entity (Exp)))) 197 or else 198 (Nkind (Exp) = N_Slice and then Has_Address_Clause (Prefix (Exp))); 199 end Has_Address_Clause; 200 201 --------------------- 202 -- Is_Formal_Array -- 203 --------------------- 204 205 function Is_Formal_Array (Exp : Node_Id) return Boolean is 206 begin 207 return 208 (Is_Entity_Name (Exp) and then Is_Formal (Entity (Exp))) 209 or else 210 (Nkind (Exp) = N_Slice and then Is_Formal_Array (Prefix (Exp))); 211 end Is_Formal_Array; 212 213 ------------------------ 214 -- Is_Non_Local_Array -- 215 ------------------------ 216 217 function Is_Non_Local_Array (Exp : Node_Id) return Boolean is 218 begin 219 return (Is_Entity_Name (Exp) 220 and then Scope (Entity (Exp)) /= Current_Scope) 221 or else (Nkind (Exp) = N_Slice 222 and then Is_Non_Local_Array (Prefix (Exp))); 223 end Is_Non_Local_Array; 224 225 ------------------------------ 226 -- Possible_Unaligned_Slice -- 227 ------------------------------ 228 229 function Possible_Unaligned_Slice (Arg : Node_Id) return Boolean is 230 begin 231 -- No issue if this is not a slice, or else strict alignment 232 -- is not required in any case. 233 234 if Nkind (Arg) /= N_Slice 235 or else not Target_Strict_Alignment 236 then 237 return False; 238 end if; 239 240 -- No issue if the component type is a byte or byte aligned 241 242 declare 243 Array_Typ : constant Entity_Id := Etype (Arg); 244 Comp_Typ : constant Entity_Id := Component_Type (Array_Typ); 245 Pref : constant Node_Id := Prefix (Arg); 246 247 begin 248 if Known_Alignment (Array_Typ) then 249 if Alignment (Array_Typ) = 1 then 250 return False; 251 end if; 252 253 elsif Known_Component_Size (Array_Typ) then 254 if Component_Size (Array_Typ) = 1 then 255 return False; 256 end if; 257 258 elsif Known_Esize (Comp_Typ) then 259 if Esize (Comp_Typ) <= System_Storage_Unit then 260 return False; 261 end if; 262 end if; 263 264 -- No issue if this is not a selected component 265 266 if Nkind (Pref) /= N_Selected_Component then 267 return False; 268 end if; 269 270 -- Else we test for a possibly unaligned component 271 272 return 273 Is_Packed (Etype (Pref)) 274 or else 275 Present (Component_Clause (Entity (Selector_Name (Pref)))); 276 end; 277 end Possible_Unaligned_Slice; 278 279 -- Determine if Lhs, Rhs are formal arrays or nonlocal arrays 280 281 Lhs_Formal : constant Boolean := Is_Formal_Array (Act_Lhs); 282 Rhs_Formal : constant Boolean := Is_Formal_Array (Act_Rhs); 283 284 Lhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Lhs); 285 Rhs_Non_Local_Var : constant Boolean := Is_Non_Local_Array (Act_Rhs); 286 287 -- Start of processing for Expand_Assign_Array 288 289 begin 290 -- Deal with length check, note that the length check is done with 291 -- respect to the right hand side as given, not a possible underlying 292 -- renamed object, since this would generate incorrect extra checks. 293 294 Apply_Length_Check (Rhs, L_Type); 295 296 -- We start by assuming that the move can be done in either 297 -- direction, i.e. that the two sides are completely disjoint. 298 299 Set_Forwards_OK (N, True); 300 Set_Backwards_OK (N, True); 301 302 -- Normally it is only the slice case that can lead to overlap, 303 -- and explicit checks for slices are made below. But there is 304 -- one case where the slice can be implicit and invisible to us 305 -- and that is the case where we have a one dimensional array, 306 -- and either both operands are parameters, or one is a parameter 307 -- and the other is a global variable. In this case the parameter 308 -- could be a slice that overlaps with the other parameter. 309 310 -- Check for the case of slices requiring an explicit loop. Normally 311 -- it is only the explicit slice cases that bother us, but in the 312 -- case of one dimensional arrays, parameters can be slices that 313 -- are passed by reference, so we can have aliasing for assignments 314 -- from one parameter to another, or assignments between parameters 315 -- and nonlocal variables. However, if the array subtype is a 316 -- constrained first subtype in the parameter case, then we don't 317 -- have to worry about overlap, since slice assignments aren't 318 -- possible (other than for a slice denoting the whole array). 319 320 -- Note: overlap is never possible if there is a change of 321 -- representation, so we can exclude this case. 322 323 if Ndim = 1 324 and then not Crep 325 and then 326 ((Lhs_Formal and Rhs_Formal) 327 or else 328 (Lhs_Formal and Rhs_Non_Local_Var) 329 or else 330 (Rhs_Formal and Lhs_Non_Local_Var)) 331 and then 332 (not Is_Constrained (Etype (Lhs)) 333 or else not Is_First_Subtype (Etype (Lhs))) 334 335 -- In the case of compiling for the Java Virtual Machine, 336 -- slices are always passed by making a copy, so we don't 337 -- have to worry about overlap. We also want to prevent 338 -- generation of "<" comparisons for array addresses, 339 -- since that's a meaningless operation on the JVM. 340 341 and then not Java_VM 342 then 343 Set_Forwards_OK (N, False); 344 Set_Backwards_OK (N, False); 345 346 -- Note: the bit-packed case is not worrisome here, since if 347 -- we have a slice passed as a parameter, it is always aligned 348 -- on a byte boundary, and if there are no explicit slices, the 349 -- assignment can be performed directly. 350 end if; 351 352 -- We certainly must use a loop for change of representation 353 -- and also we use the operand of the conversion on the right 354 -- hand side as the effective right hand side (the component 355 -- types must match in this situation). 356 357 if Crep then 358 Act_Rhs := Get_Referenced_Object (Rhs); 359 R_Type := Get_Actual_Subtype (Act_Rhs); 360 Loop_Required := True; 361 362 -- We require a loop if the left side is possibly bit unaligned 363 364 elsif Possible_Bit_Aligned_Component (Lhs) 365 or else 366 Possible_Bit_Aligned_Component (Rhs) 367 then 368 Loop_Required := True; 369 370 -- Arrays with controlled components are expanded into a loop 371 -- to force calls to adjust at the component level. 372 373 elsif Has_Controlled_Component (L_Type) then 374 Loop_Required := True; 375 376 -- Case where no slice is involved 377 378 elsif not L_Slice and not R_Slice then 379 380 -- The following code deals with the case of unconstrained bit 381 -- packed arrays. The problem is that the template for such 382 -- arrays contains the bounds of the actual source level array, 383 384 -- But the copy of an entire array requires the bounds of the 385 -- underlying array. It would be nice if the back end could take 386 -- care of this, but right now it does not know how, so if we 387 -- have such a type, then we expand out into a loop, which is 388 -- inefficient but works correctly. If we don't do this, we 389 -- get the wrong length computed for the array to be moved. 390 -- The two cases we need to worry about are: 391 392 -- Explicit deference of an unconstrained packed array type as 393 -- in the following example: 394 395 -- procedure C52 is 396 -- type BITS is array(INTEGER range <>) of BOOLEAN; 397 -- pragma PACK(BITS); 398 -- type A is access BITS; 399 -- P1,P2 : A; 400 -- begin 401 -- P1 := new BITS (1 .. 65_535); 402 -- P2 := new BITS (1 .. 65_535); 403 -- P2.ALL := P1.ALL; 404 -- end C52; 405 406 -- A formal parameter reference with an unconstrained bit 407 -- array type is the other case we need to worry about (here 408 -- we assume the same BITS type declared above: 409 410 -- procedure Write_All (File : out BITS; Contents : in BITS); 411 -- begin 412 -- File.Storage := Contents; 413 -- end Write_All; 414 415 -- We expand to a loop in either of these two cases. 416 417 -- Question for future thought. Another potentially more efficient 418 -- approach would be to create the actual subtype, and then do an 419 -- unchecked conversion to this actual subtype ??? 420 421 Check_Unconstrained_Bit_Packed_Array : declare 422 423 function Is_UBPA_Reference (Opnd : Node_Id) return Boolean; 424 -- Function to perform required test for the first case, 425 -- above (dereference of an unconstrained bit packed array) 426 427 ----------------------- 428 -- Is_UBPA_Reference -- 429 ----------------------- 430 431 function Is_UBPA_Reference (Opnd : Node_Id) return Boolean is 432 Typ : constant Entity_Id := Underlying_Type (Etype (Opnd)); 433 P_Type : Entity_Id; 434 Des_Type : Entity_Id; 435 436 begin 437 if Present (Packed_Array_Type (Typ)) 438 and then Is_Array_Type (Packed_Array_Type (Typ)) 439 and then not Is_Constrained (Packed_Array_Type (Typ)) 440 then 441 return True; 442 443 elsif Nkind (Opnd) = N_Explicit_Dereference then 444 P_Type := Underlying_Type (Etype (Prefix (Opnd))); 445 446 if not Is_Access_Type (P_Type) then 447 return False; 448 449 else 450 Des_Type := Designated_Type (P_Type); 451 return 452 Is_Bit_Packed_Array (Des_Type) 453 and then not Is_Constrained (Des_Type); 454 end if; 455 456 else 457 return False; 458 end if; 459 end Is_UBPA_Reference; 460 461 -- Start of processing for Check_Unconstrained_Bit_Packed_Array 462 463 begin 464 if Is_UBPA_Reference (Lhs) 465 or else 466 Is_UBPA_Reference (Rhs) 467 then 468 Loop_Required := True; 469 470 -- Here if we do not have the case of a reference to a bit 471 -- packed unconstrained array case. In this case gigi can 472 -- most certainly handle the assignment if a forwards move 473 -- is allowed. 474 475 -- (could it handle the backwards case also???) 476 477 elsif Forwards_OK (N) then 478 return; 479 end if; 480 end Check_Unconstrained_Bit_Packed_Array; 481 482 -- Gigi can always handle the assignment if the right side is a string 483 -- literal (note that overlap is definitely impossible in this case). 484 -- If the type is packed, a string literal is always converted into a 485 -- aggregate, except in the case of a null slice, for which no aggregate 486 -- can be written. In that case, rewrite the assignment as a null 487 -- statement, a length check has already been emitted to verify that 488 -- the range of the left-hand side is empty. 489 490 -- Note that this code is not executed if we had an assignment of 491 -- a string literal to a non-bit aligned component of a record, a 492 -- case which cannot be handled by the backend 493 494 elsif Nkind (Rhs) = N_String_Literal then 495 if String_Length (Strval (Rhs)) = 0 496 and then Is_Bit_Packed_Array (L_Type) 497 then 498 Rewrite (N, Make_Null_Statement (Loc)); 499 Analyze (N); 500 end if; 501 502 return; 503 504 -- If either operand is bit packed, then we need a loop, since we 505 -- can't be sure that the slice is byte aligned. Similarly, if either 506 -- operand is a possibly unaligned slice, then we need a loop (since 507 -- gigi cannot handle unaligned slices). 508 509 elsif Is_Bit_Packed_Array (L_Type) 510 or else Is_Bit_Packed_Array (R_Type) 511 or else Possible_Unaligned_Slice (Lhs) 512 or else Possible_Unaligned_Slice (Rhs) 513 then 514 Loop_Required := True; 515 516 -- If we are not bit-packed, and we have only one slice, then no 517 -- overlap is possible except in the parameter case, so we can let 518 -- gigi handle things. 519 520 elsif not (L_Slice and R_Slice) then 521 if Forwards_OK (N) then 522 return; 523 end if; 524 end if; 525 526 -- Come here to compelete the analysis 527 528 -- Loop_Required: Set to True if we know that a loop is required 529 -- regardless of overlap considerations. 530 531 -- Forwards_OK: Set to False if we already know that a forwards 532 -- move is not safe, else set to True. 533 534 -- Backwards_OK: Set to False if we already know that a backwards 535 -- move is not safe, else set to True 536 537 -- Our task at this stage is to complete the overlap analysis, which 538 -- can result in possibly setting Forwards_OK or Backwards_OK to 539 -- False, and then generating the final code, either by deciding 540 -- that it is OK after all to let Gigi handle it, or by generating 541 -- appropriate code in the front end. 542 543 declare 544 L_Index_Typ : constant Node_Id := Etype (First_Index (L_Type)); 545 R_Index_Typ : constant Node_Id := Etype (First_Index (R_Type)); 546 547 Left_Lo : constant Node_Id := Type_Low_Bound (L_Index_Typ); 548 Left_Hi : constant Node_Id := Type_High_Bound (L_Index_Typ); 549 Right_Lo : constant Node_Id := Type_Low_Bound (R_Index_Typ); 550 Right_Hi : constant Node_Id := Type_High_Bound (R_Index_Typ); 551 552 Act_L_Array : Node_Id; 553 Act_R_Array : Node_Id; 554 555 Cleft_Lo : Node_Id; 556 Cright_Lo : Node_Id; 557 Condition : Node_Id; 558 559 Cresult : Compare_Result; 560 561 begin 562 -- Get the expressions for the arrays. If we are dealing with a 563 -- private type, then convert to the underlying type. We can do 564 -- direct assignments to an array that is a private type, but 565 -- we cannot assign to elements of the array without this extra 566 -- unchecked conversion. 567 568 if Nkind (Act_Lhs) = N_Slice then 569 Larray := Prefix (Act_Lhs); 570 else 571 Larray := Act_Lhs; 572 573 if Is_Private_Type (Etype (Larray)) then 574 Larray := 575 Unchecked_Convert_To 576 (Underlying_Type (Etype (Larray)), Larray); 577 end if; 578 end if; 579 580 if Nkind (Act_Rhs) = N_Slice then 581 Rarray := Prefix (Act_Rhs); 582 else 583 Rarray := Act_Rhs; 584 585 if Is_Private_Type (Etype (Rarray)) then 586 Rarray := 587 Unchecked_Convert_To 588 (Underlying_Type (Etype (Rarray)), Rarray); 589 end if; 590 end if; 591 592 -- If both sides are slices, we must figure out whether 593 -- it is safe to do the move in one direction or the other 594 -- It is always safe if there is a change of representation 595 -- since obviously two arrays with different representations 596 -- cannot possibly overlap. 597 598 if (not Crep) and L_Slice and R_Slice then 599 Act_L_Array := Get_Referenced_Object (Prefix (Act_Lhs)); 600 Act_R_Array := Get_Referenced_Object (Prefix (Act_Rhs)); 601 602 -- If both left and right hand arrays are entity names, and 603 -- refer to different entities, then we know that the move 604 -- is safe (the two storage areas are completely disjoint). 605 606 if Is_Entity_Name (Act_L_Array) 607 and then Is_Entity_Name (Act_R_Array) 608 and then Entity (Act_L_Array) /= Entity (Act_R_Array) 609 then 610 null; 611 612 -- Otherwise, we assume the worst, which is that the two 613 -- arrays are the same array. There is no need to check if 614 -- we know that is the case, because if we don't know it, 615 -- we still have to assume it! 616 617 -- Generally if the same array is involved, then we have 618 -- an overlapping case. We will have to really assume the 619 -- worst (i.e. set neither of the OK flags) unless we can 620 -- determine the lower or upper bounds at compile time and 621 -- compare them. 622 623 else 624 Cresult := Compile_Time_Compare (Left_Lo, Right_Lo); 625 626 if Cresult = Unknown then 627 Cresult := Compile_Time_Compare (Left_Hi, Right_Hi); 628 end if; 629 630 case Cresult is 631 when LT | LE | EQ => Set_Backwards_OK (N, False); 632 when GT | GE => Set_Forwards_OK (N, False); 633 when NE | Unknown => Set_Backwards_OK (N, False); 634 Set_Forwards_OK (N, False); 635 end case; 636 end if; 637 end if; 638 639 -- If after that analysis, Forwards_OK is still True, and 640 -- Loop_Required is False, meaning that we have not discovered 641 -- some non-overlap reason for requiring a loop, then we can 642 -- still let gigi handle it. 643 644 if not Loop_Required then 645 if Forwards_OK (N) then 646 return; 647 648 else 649 null; 650 -- Here is where a memmove would be appropriate ??? 651 end if; 652 end if; 653 654 -- At this stage we have to generate an explicit loop, and 655 -- we have the following cases: 656 657 -- Forwards_OK = True 658 659 -- Rnn : right_index := right_index'First; 660 -- for Lnn in left-index loop 661 -- left (Lnn) := right (Rnn); 662 -- Rnn := right_index'Succ (Rnn); 663 -- end loop; 664 665 -- Note: the above code MUST be analyzed with checks off, 666 -- because otherwise the Succ could overflow. But in any 667 -- case this is more efficient! 668 669 -- Forwards_OK = False, Backwards_OK = True 670 671 -- Rnn : right_index := right_index'Last; 672 -- for Lnn in reverse left-index loop 673 -- left (Lnn) := right (Rnn); 674 -- Rnn := right_index'Pred (Rnn); 675 -- end loop; 676 677 -- Note: the above code MUST be analyzed with checks off, 678 -- because otherwise the Pred could overflow. But in any 679 -- case this is more efficient! 680 681 -- Forwards_OK = Backwards_OK = False 682 683 -- This only happens if we have the same array on each side. It is 684 -- possible to create situations using overlays that violate this, 685 -- but we simply do not promise to get this "right" in this case. 686 687 -- There are two possible subcases. If the No_Implicit_Conditionals 688 -- restriction is set, then we generate the following code: 689 690 -- declare 691 -- T : constant <operand-type> := rhs; 692 -- begin 693 -- lhs := T; 694 -- end; 695 696 -- If implicit conditionals are permitted, then we generate: 697 698 -- if Left_Lo <= Right_Lo then 699 -- <code for Forwards_OK = True above> 700 -- else 701 -- <code for Backwards_OK = True above> 702 -- end if; 703 704 -- Cases where either Forwards_OK or Backwards_OK is true 705 706 if Forwards_OK (N) or else Backwards_OK (N) then 707 Rewrite (N, 708 Expand_Assign_Array_Loop 709 (N, Larray, Rarray, L_Type, R_Type, Ndim, 710 Rev => not Forwards_OK (N))); 711 712 -- Case of both are false with No_Implicit_Conditionals 713 714 elsif Restrictions (No_Implicit_Conditionals) then 715 declare 716 T : constant Entity_Id := 717 Make_Defining_Identifier (Loc, Chars => Name_T); 718 719 begin 720 Rewrite (N, 721 Make_Block_Statement (Loc, 722 Declarations => New_List ( 723 Make_Object_Declaration (Loc, 724 Defining_Identifier => T, 725 Constant_Present => True, 726 Object_Definition => 727 New_Occurrence_Of (Etype (Rhs), Loc), 728 Expression => Relocate_Node (Rhs))), 729 730 Handled_Statement_Sequence => 731 Make_Handled_Sequence_Of_Statements (Loc, 732 Statements => New_List ( 733 Make_Assignment_Statement (Loc, 734 Name => Relocate_Node (Lhs), 735 Expression => New_Occurrence_Of (T, Loc)))))); 736 end; 737 738 -- Case of both are false with implicit conditionals allowed 739 740 else 741 -- Before we generate this code, we must ensure that the 742 -- left and right side array types are defined. They may 743 -- be itypes, and we cannot let them be defined inside the 744 -- if, since the first use in the then may not be executed. 745 746 Ensure_Defined (L_Type, N); 747 Ensure_Defined (R_Type, N); 748 749 -- We normally compare addresses to find out which way round 750 -- to do the loop, since this is realiable, and handles the 751 -- cases of parameters, conversions etc. But we can't do that 752 -- in the bit packed case or the Java VM case, because addresses 753 -- don't work there. 754 755 if not Is_Bit_Packed_Array (L_Type) and then not Java_VM then 756 Condition := 757 Make_Op_Le (Loc, 758 Left_Opnd => 759 Unchecked_Convert_To (RTE (RE_Integer_Address), 760 Make_Attribute_Reference (Loc, 761 Prefix => 762 Make_Indexed_Component (Loc, 763 Prefix => 764 Duplicate_Subexpr_Move_Checks (Larray, True), 765 Expressions => New_List ( 766 Make_Attribute_Reference (Loc, 767 Prefix => 768 New_Reference_To 769 (L_Index_Typ, Loc), 770 Attribute_Name => Name_First))), 771 Attribute_Name => Name_Address)), 772 773 Right_Opnd => 774 Unchecked_Convert_To (RTE (RE_Integer_Address), 775 Make_Attribute_Reference (Loc, 776 Prefix => 777 Make_Indexed_Component (Loc, 778 Prefix => 779 Duplicate_Subexpr_Move_Checks (Rarray, True), 780 Expressions => New_List ( 781 Make_Attribute_Reference (Loc, 782 Prefix => 783 New_Reference_To 784 (R_Index_Typ, Loc), 785 Attribute_Name => Name_First))), 786 Attribute_Name => Name_Address))); 787 788 -- For the bit packed and Java VM cases we use the bounds. 789 -- That's OK, because we don't have to worry about parameters, 790 -- since they cannot cause overlap. Perhaps we should worry 791 -- about weird slice conversions ??? 792 793 else 794 -- Copy the bounds and reset the Analyzed flag, because the 795 -- bounds of the index type itself may be universal, and must 796 -- must be reaanalyzed to acquire the proper type for Gigi. 797 798 Cleft_Lo := New_Copy_Tree (Left_Lo); 799 Cright_Lo := New_Copy_Tree (Right_Lo); 800 Set_Analyzed (Cleft_Lo, False); 801 Set_Analyzed (Cright_Lo, False); 802 803 Condition := 804 Make_Op_Le (Loc, 805 Left_Opnd => Cleft_Lo, 806 Right_Opnd => Cright_Lo); 807 end if; 808 809 Rewrite (N, 810 Make_Implicit_If_Statement (N, 811 Condition => Condition, 812 813 Then_Statements => New_List ( 814 Expand_Assign_Array_Loop 815 (N, Larray, Rarray, L_Type, R_Type, Ndim, 816 Rev => False)), 817 818 Else_Statements => New_List ( 819 Expand_Assign_Array_Loop 820 (N, Larray, Rarray, L_Type, R_Type, Ndim, 821 Rev => True)))); 822 end if; 823 824 Analyze (N, Suppress => All_Checks); 825 end; 826 827 exception 828 when RE_Not_Available => 829 return; 830 end Expand_Assign_Array; 831 832 ------------------------------ 833 -- Expand_Assign_Array_Loop -- 834 ------------------------------ 835 836 -- The following is an example of the loop generated for the case of 837 -- a two-dimensional array: 838 839 -- declare 840 -- R2b : Tm1X1 := 1; 841 -- begin 842 -- for L1b in 1 .. 100 loop 843 -- declare 844 -- R4b : Tm1X2 := 1; 845 -- begin 846 -- for L3b in 1 .. 100 loop 847 -- vm1 (L1b, L3b) := vm2 (R2b, R4b); 848 -- R4b := Tm1X2'succ(R4b); 849 -- end loop; 850 -- end; 851 -- R2b := Tm1X1'succ(R2b); 852 -- end loop; 853 -- end; 854 855 -- Here Rev is False, and Tm1Xn are the subscript types for the right 856 -- hand side. The declarations of R2b and R4b are inserted before the 857 -- original assignment statement. 858 859 function Expand_Assign_Array_Loop 860 (N : Node_Id; 861 Larray : Entity_Id; 862 Rarray : Entity_Id; 863 L_Type : Entity_Id; 864 R_Type : Entity_Id; 865 Ndim : Pos; 866 Rev : Boolean) return Node_Id 867 is 868 Loc : constant Source_Ptr := Sloc (N); 869 870 Lnn : array (1 .. Ndim) of Entity_Id; 871 Rnn : array (1 .. Ndim) of Entity_Id; 872 -- Entities used as subscripts on left and right sides 873 874 L_Index_Type : array (1 .. Ndim) of Entity_Id; 875 R_Index_Type : array (1 .. Ndim) of Entity_Id; 876 -- Left and right index types 877 878 Assign : Node_Id; 879 880 F_Or_L : Name_Id; 881 S_Or_P : Name_Id; 882 883 begin 884 if Rev then 885 F_Or_L := Name_Last; 886 S_Or_P := Name_Pred; 887 else 888 F_Or_L := Name_First; 889 S_Or_P := Name_Succ; 890 end if; 891 892 -- Setup index types and subscript entities 893 894 declare 895 L_Index : Node_Id; 896 R_Index : Node_Id; 897 898 begin 899 L_Index := First_Index (L_Type); 900 R_Index := First_Index (R_Type); 901 902 for J in 1 .. Ndim loop 903 Lnn (J) := 904 Make_Defining_Identifier (Loc, 905 Chars => New_Internal_Name ('L')); 906 907 Rnn (J) := 908 Make_Defining_Identifier (Loc, 909 Chars => New_Internal_Name ('R')); 910 911 L_Index_Type (J) := Etype (L_Index); 912 R_Index_Type (J) := Etype (R_Index); 913 914 Next_Index (L_Index); 915 Next_Index (R_Index); 916 end loop; 917 end; 918 919 -- Now construct the assignment statement 920 921 declare 922 ExprL : constant List_Id := New_List; 923 ExprR : constant List_Id := New_List; 924 925 begin 926 for J in 1 .. Ndim loop 927 Append_To (ExprL, New_Occurrence_Of (Lnn (J), Loc)); 928 Append_To (ExprR, New_Occurrence_Of (Rnn (J), Loc)); 929 end loop; 930 931 Assign := 932 Make_Assignment_Statement (Loc, 933 Name => 934 Make_Indexed_Component (Loc, 935 Prefix => Duplicate_Subexpr (Larray, Name_Req => True), 936 Expressions => ExprL), 937 Expression => 938 Make_Indexed_Component (Loc, 939 Prefix => Duplicate_Subexpr (Rarray, Name_Req => True), 940 Expressions => ExprR)); 941 942 -- Propagate the No_Ctrl_Actions flag to individual assignments 943 944 Set_No_Ctrl_Actions (Assign, No_Ctrl_Actions (N)); 945 end; 946 947 -- Now construct the loop from the inside out, with the last subscript 948 -- varying most rapidly. Note that Assign is first the raw assignment 949 -- statement, and then subsequently the loop that wraps it up. 950 951 for J in reverse 1 .. Ndim loop 952 Assign := 953 Make_Block_Statement (Loc, 954 Declarations => New_List ( 955 Make_Object_Declaration (Loc, 956 Defining_Identifier => Rnn (J), 957 Object_Definition => 958 New_Occurrence_Of (R_Index_Type (J), Loc), 959 Expression => 960 Make_Attribute_Reference (Loc, 961 Prefix => New_Occurrence_Of (R_Index_Type (J), Loc), 962 Attribute_Name => F_Or_L))), 963 964 Handled_Statement_Sequence => 965 Make_Handled_Sequence_Of_Statements (Loc, 966 Statements => New_List ( 967 Make_Implicit_Loop_Statement (N, 968 Iteration_Scheme => 969 Make_Iteration_Scheme (Loc, 970 Loop_Parameter_Specification => 971 Make_Loop_Parameter_Specification (Loc, 972 Defining_Identifier => Lnn (J), 973 Reverse_Present => Rev, 974 Discrete_Subtype_Definition => 975 New_Reference_To (L_Index_Type (J), Loc))), 976 977 Statements => New_List ( 978 Assign, 979 980 Make_Assignment_Statement (Loc, 981 Name => New_Occurrence_Of (Rnn (J), Loc), 982 Expression => 983 Make_Attribute_Reference (Loc, 984 Prefix => 985 New_Occurrence_Of (R_Index_Type (J), Loc), 986 Attribute_Name => S_Or_P, 987 Expressions => New_List ( 988 New_Occurrence_Of (Rnn (J), Loc))))))))); 989 end loop; 990 991 return Assign; 992 end Expand_Assign_Array_Loop; 993 994 -------------------------- 995 -- Expand_Assign_Record -- 996 -------------------------- 997 998 -- The only processing required is in the change of representation 999 -- case, where we must expand the assignment to a series of field 1000 -- by field assignments. 1001 1002 procedure Expand_Assign_Record (N : Node_Id) is 1003 Lhs : constant Node_Id := Name (N); 1004 Rhs : Node_Id := Expression (N); 1005 1006 begin 1007 -- If change of representation, then extract the real right hand 1008 -- side from the type conversion, and proceed with component-wise 1009 -- assignment, since the two types are not the same as far as the 1010 -- back end is concerned. 1011 1012 if Change_Of_Representation (N) then 1013 Rhs := Expression (Rhs); 1014 1015 -- If this may be a case of a large bit aligned component, then 1016 -- proceed with component-wise assignment, to avoid possible 1017 -- clobbering of other components sharing bits in the first or 1018 -- last byte of the component to be assigned. 1019 1020 elsif Possible_Bit_Aligned_Component (Lhs) 1021 or 1022 Possible_Bit_Aligned_Component (Rhs) 1023 then 1024 null; 1025 1026 -- If neither condition met, then nothing special to do, the back end 1027 -- can handle assignment of the entire component as a single entity. 1028 1029 else 1030 return; 1031 end if; 1032 1033 -- At this stage we know that we must do a component wise assignment 1034 1035 declare 1036 Loc : constant Source_Ptr := Sloc (N); 1037 R_Typ : constant Entity_Id := Base_Type (Etype (Rhs)); 1038 L_Typ : constant Entity_Id := Base_Type (Etype (Lhs)); 1039 Decl : constant Node_Id := Declaration_Node (R_Typ); 1040 RDef : Node_Id; 1041 F : Entity_Id; 1042 1043 function Find_Component 1044 (Typ : Entity_Id; 1045 Comp : Entity_Id) return Entity_Id; 1046 -- Find the component with the given name in the underlying record 1047 -- declaration for Typ. We need to use the actual entity because 1048 -- the type may be private and resolution by identifier alone would 1049 -- fail. 1050 1051 function Make_Component_List_Assign (CL : Node_Id) return List_Id; 1052 -- Returns a sequence of statements to assign the components that 1053 -- are referenced in the given component list. 1054 1055 function Make_Field_Assign (C : Entity_Id) return Node_Id; 1056 -- Given C, the entity for a discriminant or component, build 1057 -- an assignment for the corresponding field values. 1058 1059 function Make_Field_Assigns (CI : List_Id) return List_Id; 1060 -- Given CI, a component items list, construct series of statements 1061 -- for fieldwise assignment of the corresponding components. 1062 1063 -------------------- 1064 -- Find_Component -- 1065 -------------------- 1066 1067 function Find_Component 1068 (Typ : Entity_Id; 1069 Comp : Entity_Id) return Entity_Id 1070 is 1071 Utyp : constant Entity_Id := Underlying_Type (Typ); 1072 C : Entity_Id; 1073 1074 begin 1075 C := First_Entity (Utyp); 1076 1077 while Present (C) loop 1078 if Chars (C) = Chars (Comp) then 1079 return C; 1080 end if; 1081 Next_Entity (C); 1082 end loop; 1083 1084 raise Program_Error; 1085 end Find_Component; 1086 1087 -------------------------------- 1088 -- Make_Component_List_Assign -- 1089 -------------------------------- 1090 1091 function Make_Component_List_Assign (CL : Node_Id) return List_Id is 1092 CI : constant List_Id := Component_Items (CL); 1093 VP : constant Node_Id := Variant_Part (CL); 1094 1095 Result : List_Id; 1096 Alts : List_Id; 1097 V : Node_Id; 1098 DC : Node_Id; 1099 DCH : List_Id; 1100 1101 begin 1102 Result := Make_Field_Assigns (CI); 1103 1104 if Present (VP) then 1105 1106 V := First_Non_Pragma (Variants (VP)); 1107 Alts := New_List; 1108 while Present (V) loop 1109 1110 DCH := New_List; 1111 DC := First (Discrete_Choices (V)); 1112 while Present (DC) loop 1113 Append_To (DCH, New_Copy_Tree (DC)); 1114 Next (DC); 1115 end loop; 1116 1117 Append_To (Alts, 1118 Make_Case_Statement_Alternative (Loc, 1119 Discrete_Choices => DCH, 1120 Statements => 1121 Make_Component_List_Assign (Component_List (V)))); 1122 Next_Non_Pragma (V); 1123 end loop; 1124 1125 Append_To (Result, 1126 Make_Case_Statement (Loc, 1127 Expression => 1128 Make_Selected_Component (Loc, 1129 Prefix => Duplicate_Subexpr (Rhs), 1130 Selector_Name => 1131 Make_Identifier (Loc, Chars (Name (VP)))), 1132 Alternatives => Alts)); 1133 1134 end if; 1135 1136 return Result; 1137 end Make_Component_List_Assign; 1138 1139 ----------------------- 1140 -- Make_Field_Assign -- 1141 ----------------------- 1142 1143 function Make_Field_Assign (C : Entity_Id) return Node_Id is 1144 A : Node_Id; 1145 1146 begin 1147 A := 1148 Make_Assignment_Statement (Loc, 1149 Name => 1150 Make_Selected_Component (Loc, 1151 Prefix => Duplicate_Subexpr (Lhs), 1152 Selector_Name => 1153 New_Occurrence_Of (Find_Component (L_Typ, C), Loc)), 1154 Expression => 1155 Make_Selected_Component (Loc, 1156 Prefix => Duplicate_Subexpr (Rhs), 1157 Selector_Name => New_Occurrence_Of (C, Loc))); 1158 1159 -- Set Assignment_OK, so discriminants can be assigned 1160 1161 Set_Assignment_OK (Name (A), True); 1162 return A; 1163 end Make_Field_Assign; 1164 1165 ------------------------ 1166 -- Make_Field_Assigns -- 1167 ------------------------ 1168 1169 function Make_Field_Assigns (CI : List_Id) return List_Id is 1170 Item : Node_Id; 1171 Result : List_Id; 1172 1173 begin 1174 Item := First (CI); 1175 Result := New_List; 1176 1177 while Present (Item) loop 1178 if Nkind (Item) = N_Component_Declaration then 1179 Append_To 1180 (Result, Make_Field_Assign (Defining_Identifier (Item))); 1181 end if; 1182 1183 Next (Item); 1184 end loop; 1185 1186 return Result; 1187 end Make_Field_Assigns; 1188 1189 -- Start of processing for Expand_Assign_Record 1190 1191 begin 1192 -- Note that we use the base types for this processing. This results 1193 -- in some extra work in the constrained case, but the change of 1194 -- representation case is so unusual that it is not worth the effort. 1195 1196 -- First copy the discriminants. This is done unconditionally. It 1197 -- is required in the unconstrained left side case, and also in the 1198 -- case where this assignment was constructed during the expansion 1199 -- of a type conversion (since initialization of discriminants is 1200 -- suppressed in this case). It is unnecessary but harmless in 1201 -- other cases. 1202 1203 if Has_Discriminants (L_Typ) then 1204 F := First_Discriminant (R_Typ); 1205 while Present (F) loop 1206 Insert_Action (N, Make_Field_Assign (F)); 1207 Next_Discriminant (F); 1208 end loop; 1209 end if; 1210 1211 -- We know the underlying type is a record, but its current view 1212 -- may be private. We must retrieve the usable record declaration. 1213 1214 if Nkind (Decl) = N_Private_Type_Declaration 1215 and then Present (Full_View (R_Typ)) 1216 then 1217 RDef := Type_Definition (Declaration_Node (Full_View (R_Typ))); 1218 else 1219 RDef := Type_Definition (Decl); 1220 end if; 1221 1222 if Nkind (RDef) = N_Record_Definition 1223 and then Present (Component_List (RDef)) 1224 then 1225 Insert_Actions 1226 (N, Make_Component_List_Assign (Component_List (RDef))); 1227 1228 Rewrite (N, Make_Null_Statement (Loc)); 1229 end if; 1230 1231 end; 1232 end Expand_Assign_Record; 1233 1234 ----------------------------------- 1235 -- Expand_N_Assignment_Statement -- 1236 ----------------------------------- 1237 1238 -- For array types, deal with slice assignments and setting the flags 1239 -- to indicate if it can be statically determined which direction the 1240 -- move should go in. Also deal with generating range/length checks. 1241 1242 procedure Expand_N_Assignment_Statement (N : Node_Id) is 1243 Loc : constant Source_Ptr := Sloc (N); 1244 Lhs : constant Node_Id := Name (N); 1245 Rhs : constant Node_Id := Expression (N); 1246 Typ : constant Entity_Id := Underlying_Type (Etype (Lhs)); 1247 Exp : Node_Id; 1248 1249 begin 1250 -- First deal with generation of range check if required. For now 1251 -- we do this only for discrete types. 1252 1253 if Do_Range_Check (Rhs) 1254 and then Is_Discrete_Type (Typ) 1255 then 1256 Set_Do_Range_Check (Rhs, False); 1257 Generate_Range_Check (Rhs, Typ, CE_Range_Check_Failed); 1258 end if; 1259 1260 -- Check for a special case where a high level transformation is 1261 -- required. If we have either of: 1262 1263 -- P.field := rhs; 1264 -- P (sub) := rhs; 1265 1266 -- where P is a reference to a bit packed array, then we have to unwind 1267 -- the assignment. The exact meaning of being a reference to a bit 1268 -- packed array is as follows: 1269 1270 -- An indexed component whose prefix is a bit packed array is a 1271 -- reference to a bit packed array. 1272 1273 -- An indexed component or selected component whose prefix is a 1274 -- reference to a bit packed array is itself a reference ot a 1275 -- bit packed array. 1276 1277 -- The required transformation is 1278 1279 -- Tnn : prefix_type := P; 1280 -- Tnn.field := rhs; 1281 -- P := Tnn; 1282 1283 -- or 1284 1285 -- Tnn : prefix_type := P; 1286 -- Tnn (subscr) := rhs; 1287 -- P := Tnn; 1288 1289 -- Since P is going to be evaluated more than once, any subscripts 1290 -- in P must have their evaluation forced. 1291 1292 if (Nkind (Lhs) = N_Indexed_Component 1293 or else 1294 Nkind (Lhs) = N_Selected_Component) 1295 and then Is_Ref_To_Bit_Packed_Array (Prefix (Lhs)) 1296 then 1297 declare 1298 BPAR_Expr : constant Node_Id := Relocate_Node (Prefix (Lhs)); 1299 BPAR_Typ : constant Entity_Id := Etype (BPAR_Expr); 1300 Tnn : constant Entity_Id := 1301 Make_Defining_Identifier (Loc, 1302 Chars => New_Internal_Name ('T')); 1303 1304 begin 1305 -- Insert the post assignment first, because we want to copy 1306 -- the BPAR_Expr tree before it gets analyzed in the context 1307 -- of the pre assignment. Note that we do not analyze the 1308 -- post assignment yet (we cannot till we have completed the 1309 -- analysis of the pre assignment). As usual, the analysis 1310 -- of this post assignment will happen on its own when we 1311 -- "run into" it after finishing the current assignment. 1312 1313 Insert_After (N, 1314 Make_Assignment_Statement (Loc, 1315 Name => New_Copy_Tree (BPAR_Expr), 1316 Expression => New_Occurrence_Of (Tnn, Loc))); 1317 1318 -- At this stage BPAR_Expr is a reference to a bit packed 1319 -- array where the reference was not expanded in the original 1320 -- tree, since it was on the left side of an assignment. But 1321 -- in the pre-assignment statement (the object definition), 1322 -- BPAR_Expr will end up on the right hand side, and must be 1323 -- reexpanded. To achieve this, we reset the analyzed flag 1324 -- of all selected and indexed components down to the actual 1325 -- indexed component for the packed array. 1326 1327 Exp := BPAR_Expr; 1328 loop 1329 Set_Analyzed (Exp, False); 1330 1331 if Nkind (Exp) = N_Selected_Component 1332 or else 1333 Nkind (Exp) = N_Indexed_Component 1334 then 1335 Exp := Prefix (Exp); 1336 else 1337 exit; 1338 end if; 1339 end loop; 1340 1341 -- Now we can insert and analyze the pre-assignment. 1342 1343 -- If the right-hand side requires a transient scope, it has 1344 -- already been placed on the stack. However, the declaration is 1345 -- inserted in the tree outside of this scope, and must reflect 1346 -- the proper scope for its variable. This awkward bit is forced 1347 -- by the stricter scope discipline imposed by GCC 2.97. 1348 1349 declare 1350 Uses_Transient_Scope : constant Boolean := 1351 Scope_Is_Transient and then N = Node_To_Be_Wrapped; 1352 1353 begin 1354 if Uses_Transient_Scope then 1355 New_Scope (Scope (Current_Scope)); 1356 end if; 1357 1358 Insert_Before_And_Analyze (N, 1359 Make_Object_Declaration (Loc, 1360 Defining_Identifier => Tnn, 1361 Object_Definition => New_Occurrence_Of (BPAR_Typ, Loc), 1362 Expression => BPAR_Expr)); 1363 1364 if Uses_Transient_Scope then 1365 Pop_Scope; 1366 end if; 1367 end; 1368 1369 -- Now fix up the original assignment and continue processing 1370 1371 Rewrite (Prefix (Lhs), 1372 New_Occurrence_Of (Tnn, Loc)); 1373 1374 -- We do not need to reanalyze that assignment, and we do not need 1375 -- to worry about references to the temporary, but we do need to 1376 -- make sure that the temporary is not marked as a true constant 1377 -- since we now have a generate assignment to it! 1378 1379 Set_Is_True_Constant (Tnn, False); 1380 end; 1381 end if; 1382 1383 -- When we have the appropriate type of aggregate in the 1384 -- expression (it has been determined during analysis of the 1385 -- aggregate by setting the delay flag), let's perform in place 1386 -- assignment and thus avoid creating a temporay. 1387 1388 if Is_Delayed_Aggregate (Rhs) then 1389 Convert_Aggr_In_Assignment (N); 1390 Rewrite (N, Make_Null_Statement (Loc)); 1391 Analyze (N); 1392 return; 1393 end if; 1394 1395 -- Apply discriminant check if required. If Lhs is an access type 1396 -- to a designated type with discriminants, we must always check. 1397 1398 if Has_Discriminants (Etype (Lhs)) then 1399 1400 -- Skip discriminant check if change of representation. Will be 1401 -- done when the change of representation is expanded out. 1402 1403 if not Change_Of_Representation (N) then 1404 Apply_Discriminant_Check (Rhs, Etype (Lhs), Lhs); 1405 end if; 1406 1407 -- If the type is private without discriminants, and the full type 1408 -- has discriminants (necessarily with defaults) a check may still be 1409 -- necessary if the Lhs is aliased. The private determinants must be 1410 -- visible to build the discriminant constraints. 1411 1412 -- Only an explicit dereference that comes from source indicates 1413 -- aliasing. Access to formals of protected operations and entries 1414 -- create dereferences but are not semantic aliasings. 1415 1416 elsif Is_Private_Type (Etype (Lhs)) 1417 and then Has_Discriminants (Typ) 1418 and then Nkind (Lhs) = N_Explicit_Dereference 1419 and then Comes_From_Source (Lhs) 1420 then 1421 declare 1422 Lt : constant Entity_Id := Etype (Lhs); 1423 begin 1424 Set_Etype (Lhs, Typ); 1425 Rewrite (Rhs, OK_Convert_To (Base_Type (Typ), Rhs)); 1426 Apply_Discriminant_Check (Rhs, Typ, Lhs); 1427 Set_Etype (Lhs, Lt); 1428 end; 1429 1430 -- If the Lhs has a private type with unknown discriminants, it 1431 -- may have a full view with discriminants, but those are nameable 1432 -- only in the underlying type, so convert the Rhs to it before 1433 -- potential checking. 1434 1435 elsif Has_Unknown_Discriminants (Base_Type (Etype (Lhs))) 1436 and then Has_Discriminants (Typ) 1437 then 1438 Rewrite (Rhs, OK_Convert_To (Base_Type (Typ), Rhs)); 1439 Apply_Discriminant_Check (Rhs, Typ, Lhs); 1440 1441 -- In the access type case, we need the same discriminant check, 1442 -- and also range checks if we have an access to constrained array. 1443 1444 elsif Is_Access_Type (Etype (Lhs)) 1445 and then Is_Constrained (Designated_Type (Etype (Lhs))) 1446 then 1447 if Has_Discriminants (Designated_Type (Etype (Lhs))) then 1448 1449 -- Skip discriminant check if change of representation. Will be 1450 -- done when the change of representation is expanded out. 1451 1452 if not Change_Of_Representation (N) then 1453 Apply_Discriminant_Check (Rhs, Etype (Lhs)); 1454 end if; 1455 1456 elsif Is_Array_Type (Designated_Type (Etype (Lhs))) then 1457 Apply_Range_Check (Rhs, Etype (Lhs)); 1458 1459 if Is_Constrained (Etype (Lhs)) then 1460 Apply_Length_Check (Rhs, Etype (Lhs)); 1461 end if; 1462 1463 if Nkind (Rhs) = N_Allocator then 1464 declare 1465 Target_Typ : constant Entity_Id := Etype (Expression (Rhs)); 1466 C_Es : Check_Result; 1467 1468 begin 1469 C_Es := 1470 Range_Check 1471 (Lhs, 1472 Target_Typ, 1473 Etype (Designated_Type (Etype (Lhs)))); 1474 1475 Insert_Range_Checks 1476 (C_Es, 1477 N, 1478 Target_Typ, 1479 Sloc (Lhs), 1480 Lhs); 1481 end; 1482 end if; 1483 end if; 1484 1485 -- Apply range check for access type case 1486 1487 elsif Is_Access_Type (Etype (Lhs)) 1488 and then Nkind (Rhs) = N_Allocator 1489 and then Nkind (Expression (Rhs)) = N_Qualified_Expression 1490 then 1491 Analyze_And_Resolve (Expression (Rhs)); 1492 Apply_Range_Check 1493 (Expression (Rhs), Designated_Type (Etype (Lhs))); 1494 end if; 1495 1496 -- If we are assigning an access type and the left side is an 1497 -- entity, then make sure that Is_Known_Non_Null properly 1498 -- reflects the state of the entity after the assignment 1499 1500 if Is_Access_Type (Typ) 1501 and then Is_Entity_Name (Lhs) 1502 and then Known_Non_Null (Rhs) 1503 and then Safe_To_Capture_Value (N, Entity (Lhs)) 1504 then 1505 Set_Is_Known_Non_Null (Entity (Lhs), Known_Non_Null (Rhs)); 1506 end if; 1507 1508 -- Case of assignment to a bit packed array element 1509 1510 if Nkind (Lhs) = N_Indexed_Component 1511 and then Is_Bit_Packed_Array (Etype (Prefix (Lhs))) 1512 then 1513 Expand_Bit_Packed_Element_Set (N); 1514 return; 1515 1516 -- Case of tagged type assignment 1517 1518 elsif Is_Tagged_Type (Typ) 1519 or else (Controlled_Type (Typ) and then not Is_Array_Type (Typ)) 1520 then 1521 Tagged_Case : declare 1522 L : List_Id := No_List; 1523 Expand_Ctrl_Actions : constant Boolean := not No_Ctrl_Actions (N); 1524 1525 begin 1526 -- In the controlled case, we need to make sure that function 1527 -- calls are evaluated before finalizing the target. In all 1528 -- cases, it makes the expansion easier if the side-effects 1529 -- are removed first. 1530 1531 Remove_Side_Effects (Lhs); 1532 Remove_Side_Effects (Rhs); 1533 1534 -- Avoid recursion in the mechanism 1535 1536 Set_Analyzed (N); 1537 1538 -- If dispatching assignment, we need to dispatch to _assign 1539 1540 if Is_Class_Wide_Type (Typ) 1541 1542 -- If the type is tagged, we may as well use the predefined 1543 -- primitive assignment. This avoids inlining a lot of code 1544 -- and in the class-wide case, the assignment is replaced by 1545 -- a dispatch call to _assign. Note that this cannot be done 1546 -- when discriminant checks are locally suppressed (as in 1547 -- extension aggregate expansions) because otherwise the 1548 -- discriminant check will be performed within the _assign 1549 -- call. 1550 1551 or else (Is_Tagged_Type (Typ) 1552 and then Chars (Current_Scope) /= Name_uAssign 1553 and then Expand_Ctrl_Actions 1554 and then not Discriminant_Checks_Suppressed (Empty)) 1555 then 1556 -- Fetch the primitive op _assign and proper type to call 1557 -- it. Because of possible conflits between private and 1558 -- full view the proper type is fetched directly from the 1559 -- operation profile. 1560 1561 declare 1562 Op : constant Entity_Id := 1563 Find_Prim_Op (Typ, Name_uAssign); 1564 F_Typ : Entity_Id := Etype (First_Formal (Op)); 1565 1566 begin 1567 -- If the assignment is dispatching, make sure to use the 1568 -- ??? where is rest of this comment ??? 1569 1570 if Is_Class_Wide_Type (Typ) then 1571 F_Typ := Class_Wide_Type (F_Typ); 1572 end if; 1573 1574 L := New_List ( 1575 Make_Procedure_Call_Statement (Loc, 1576 Name => New_Reference_To (Op, Loc), 1577 Parameter_Associations => New_List ( 1578 Unchecked_Convert_To (F_Typ, Duplicate_Subexpr (Lhs)), 1579 Unchecked_Convert_To (F_Typ, 1580 Duplicate_Subexpr (Rhs))))); 1581 end; 1582 1583 else 1584 L := Make_Tag_Ctrl_Assignment (N); 1585 1586 -- We can't afford to have destructive Finalization Actions 1587 -- in the Self assignment case, so if the target and the 1588 -- source are not obviously different, code is generated to 1589 -- avoid the self assignment case 1590 -- 1591 -- if lhs'address /= rhs'address then 1592 -- <code for controlled and/or tagged assignment> 1593 -- end if; 1594 1595 if not Statically_Different (Lhs, Rhs) 1596 and then Expand_Ctrl_Actions 1597 then 1598 L := New_List ( 1599 Make_Implicit_If_Statement (N, 1600 Condition => 1601 Make_Op_Ne (Loc, 1602 Left_Opnd => 1603 Make_Attribute_Reference (Loc, 1604 Prefix => Duplicate_Subexpr (Lhs), 1605 Attribute_Name => Name_Address), 1606 1607 Right_Opnd => 1608 Make_Attribute_Reference (Loc, 1609 Prefix => Duplicate_Subexpr (Rhs), 1610 Attribute_Name => Name_Address)), 1611 1612 Then_Statements => L)); 1613 end if; 1614 1615 -- We need to set up an exception handler for implementing 1616 -- 7.6.1 (18). The remaining adjustments are tackled by the 1617 -- implementation of adjust for record_controllers (see 1618 -- s-finimp.adb) 1619 1620 -- This is skipped if we have no finalization 1621 1622 if Expand_Ctrl_Actions 1623 and then not Restrictions (No_Finalization) 1624 then 1625 L := New_List ( 1626 Make_Block_Statement (Loc, 1627 Handled_Statement_Sequence => 1628 Make_Handled_Sequence_Of_Statements (Loc, 1629 Statements => L, 1630 Exception_Handlers => New_List ( 1631 Make_Exception_Handler (Loc, 1632 Exception_Choices => 1633 New_List (Make_Others_Choice (Loc)), 1634 Statements => New_List ( 1635 Make_Raise_Program_Error (Loc, 1636 Reason => 1637 PE_Finalize_Raised_Exception) 1638 )))))); 1639 end if; 1640 end if; 1641 1642 Rewrite (N, 1643 Make_Block_Statement (Loc, 1644 Handled_Statement_Sequence => 1645 Make_Handled_Sequence_Of_Statements (Loc, Statements => L))); 1646 1647 -- If no restrictions on aborts, protect the whole assignement 1648 -- for controlled objects as per 9.8(11) 1649 1650 if Controlled_Type (Typ) 1651 and then Expand_Ctrl_Actions 1652 and then Abort_Allowed 1653 then 1654 declare 1655 Blk : constant Entity_Id := 1656 New_Internal_Entity ( 1657 E_Block, Current_Scope, Sloc (N), 'B'); 1658 1659 begin 1660 Set_Scope (Blk, Current_Scope); 1661 Set_Etype (Blk, Standard_Void_Type); 1662 Set_Identifier (N, New_Occurrence_Of (Blk, Sloc (N))); 1663 1664 Prepend_To (L, Build_Runtime_Call (Loc, RE_Abort_Defer)); 1665 Set_At_End_Proc (Handled_Statement_Sequence (N), 1666 New_Occurrence_Of (RTE (RE_Abort_Undefer_Direct), Loc)); 1667 Expand_At_End_Handler 1668 (Handled_Statement_Sequence (N), Blk); 1669 end; 1670 end if; 1671 1672 Analyze (N); 1673 return; 1674 end Tagged_Case; 1675 1676 -- Array types 1677 1678 elsif Is_Array_Type (Typ) then 1679 declare 1680 Actual_Rhs : Node_Id := Rhs; 1681 1682 begin 1683 while Nkind (Actual_Rhs) = N_Type_Conversion 1684 or else 1685 Nkind (Actual_Rhs) = N_Qualified_Expression 1686 loop 1687 Actual_Rhs := Expression (Actual_Rhs); 1688 end loop; 1689 1690 Expand_Assign_Array (N, Actual_Rhs); 1691 return; 1692 end; 1693 1694 -- Record types 1695 1696 elsif Is_Record_Type (Typ) then 1697 Expand_Assign_Record (N); 1698 return; 1699 1700 -- Scalar types. This is where we perform the processing related 1701 -- to the requirements of (RM 13.9.1(9-11)) concerning the handling 1702 -- of invalid scalar values. 1703 1704 elsif Is_Scalar_Type (Typ) then 1705 1706 -- Case where right side is known valid 1707 1708 if Expr_Known_Valid (Rhs) then 1709 1710 -- Here the right side is valid, so it is fine. The case to 1711 -- deal with is when the left side is a local variable reference 1712 -- whose value is not currently known to be valid. If this is 1713 -- the case, and the assignment appears in an unconditional 1714 -- context, then we can mark the left side as now being valid. 1715 1716 if Is_Local_Variable_Reference (Lhs) 1717 and then not Is_Known_Valid (Entity (Lhs)) 1718 and then In_Unconditional_Context (N) 1719 then 1720 Set_Is_Known_Valid (Entity (Lhs), True); 1721 end if; 1722 1723 -- Case where right side may be invalid in the sense of the RM 1724 -- reference above. The RM does not require that we check for 1725 -- the validity on an assignment, but it does require that the 1726 -- assignment of an invalid value not cause erroneous behavior. 1727 1728 -- The general approach in GNAT is to use the Is_Known_Valid flag 1729 -- to avoid the need for validity checking on assignments. However 1730 -- in some cases, we have to do validity checking in order to make 1731 -- sure that the setting of this flag is correct. 1732 1733 else 1734 -- Validate right side if we are validating copies 1735 1736 if Validity_Checks_On 1737 and then Validity_Check_Copies 1738 then 1739 Ensure_Valid (Rhs); 1740 1741 -- We can propagate this to the left side where appropriate 1742 1743 if Is_Local_Variable_Reference (Lhs) 1744 and then not Is_Known_Valid (Entity (Lhs)) 1745 and then In_Unconditional_Context (N) 1746 then 1747 Set_Is_Known_Valid (Entity (Lhs), True); 1748 end if; 1749 1750 -- Otherwise check to see what should be done 1751 1752 -- If left side is a local variable, then we just set its 1753 -- flag to indicate that its value may no longer be valid, 1754 -- since we are copying a potentially invalid value. 1755 1756 elsif Is_Local_Variable_Reference (Lhs) then 1757 Set_Is_Known_Valid (Entity (Lhs), False); 1758 1759 -- Check for case of a nonlocal variable on the left side 1760 -- which is currently known to be valid. In this case, we 1761 -- simply ensure that the right side is valid. We only play 1762 -- the game of copying validity status for local variables, 1763 -- since we are doing this statically, not by tracing the 1764 -- full flow graph. 1765 1766 elsif Is_Entity_Name (Lhs) 1767 and then Is_Known_Valid (Entity (Lhs)) 1768 then 1769 -- Note that the Ensure_Valid call is ignored if the 1770 -- Validity_Checking mode is set to none so we do not 1771 -- need to worry about that case here. 1772 1773 Ensure_Valid (Rhs); 1774 1775 -- In all other cases, we can safely copy an invalid value 1776 -- without worrying about the status of the left side. Since 1777 -- it is not a variable reference it will not be considered 1778 -- as being known to be valid in any case. 1779 1780 else 1781 null; 1782 end if; 1783 end if; 1784 end if; 1785 1786 -- Defend against invalid subscripts on left side if we are in 1787 -- standard validity checking mode. No need to do this if we 1788 -- are checking all subscripts. 1789 1790 if Validity_Checks_On 1791 and then Validity_Check_Default 1792 and then not Validity_Check_Subscripts 1793 then 1794 Check_Valid_Lvalue_Subscripts (Lhs); 1795 end if; 1796 1797 exception 1798 when RE_Not_Available => 1799 return; 1800 end Expand_N_Assignment_Statement; 1801 1802 ------------------------------ 1803 -- Expand_N_Block_Statement -- 1804 ------------------------------ 1805 1806 -- Encode entity names defined in block statement 1807 1808 procedure Expand_N_Block_Statement (N : Node_Id) is 1809 begin 1810 Qualify_Entity_Names (N); 1811 end Expand_N_Block_Statement; 1812 1813 ----------------------------- 1814 -- Expand_N_Case_Statement -- 1815 ----------------------------- 1816 1817 procedure Expand_N_Case_Statement (N : Node_Id) is 1818 Loc : constant Source_Ptr := Sloc (N); 1819 Expr : constant Node_Id := Expression (N); 1820 Alt : Node_Id; 1821 Len : Nat; 1822 Cond : Node_Id; 1823 Choice : Node_Id; 1824 Chlist : List_Id; 1825 1826 begin 1827 -- Check for the situation where we know at compile time which 1828 -- branch will be taken 1829 1830 if Compile_Time_Known_Value (Expr) then 1831 Alt := Find_Static_Alternative (N); 1832 1833 -- Move the statements from this alternative after the case 1834 -- statement. They are already analyzed, so will be skipped 1835 -- by the analyzer. 1836 1837 Insert_List_After (N, Statements (Alt)); 1838 1839 -- That leaves the case statement as a shell. The alternative 1840 -- that will be executed is reset to a null list. So now we can 1841 -- kill the entire case statement. 1842 1843 Kill_Dead_Code (Expression (N)); 1844 Kill_Dead_Code (Alternatives (N)); 1845 Rewrite (N, Make_Null_Statement (Loc)); 1846 return; 1847 end if; 1848 1849 -- Here if the choice is not determined at compile time 1850 1851 declare 1852 Last_Alt : constant Node_Id := Last (Alternatives (N)); 1853 1854 Others_Present : Boolean; 1855 Others_Node : Node_Id; 1856 1857 Then_Stms : List_Id; 1858 Else_Stms : List_Id; 1859 1860 begin 1861 if Nkind (First (Discrete_Choices (Last_Alt))) = N_Others_Choice then 1862 Others_Present := True; 1863 Others_Node := Last_Alt; 1864 else 1865 Others_Present := False; 1866 end if; 1867 1868 -- First step is to worry about possible invalid argument. The RM 1869 -- requires (RM 5.4(13)) that if the result is invalid (e.g. it is 1870 -- outside the base range), then Constraint_Error must be raised. 1871 1872 -- Case of validity check required (validity checks are on, the 1873 -- expression is not known to be valid, and the case statement 1874 -- comes from source -- no need to validity check internally 1875 -- generated case statements). 1876 1877 if Validity_Check_Default then 1878 Ensure_Valid (Expr); 1879 end if; 1880 1881 -- If there is only a single alternative, just replace it with 1882 -- the sequence of statements since obviously that is what is 1883 -- going to be executed in all cases. 1884 1885 Len := List_Length (Alternatives (N)); 1886 1887 if Len = 1 then 1888 -- We still need to evaluate the expression if it has any 1889 -- side effects. 1890 1891 Remove_Side_Effects (Expression (N)); 1892 1893 Insert_List_After (N, Statements (First (Alternatives (N)))); 1894 1895 -- That leaves the case statement as a shell. The alternative 1896 -- that will be executed is reset to a null list. So now we can 1897 -- kill the entire case statement. 1898 1899 Kill_Dead_Code (Expression (N)); 1900 Rewrite (N, Make_Null_Statement (Loc)); 1901 return; 1902 end if; 1903 1904 -- An optimization. If there are only two alternatives, and only 1905 -- a single choice, then rewrite the whole case statement as an 1906 -- if statement, since this can result in susbequent optimizations. 1907 -- This helps not only with case statements in the source of a 1908 -- simple form, but also with generated code (discriminant check 1909 -- functions in particular) 1910 1911 if Len = 2 then 1912 Chlist := Discrete_Choices (First (Alternatives (N))); 1913 1914 if List_Length (Chlist) = 1 then 1915 Choice := First (Chlist); 1916 1917 Then_Stms := Statements (First (Alternatives (N))); 1918 Else_Stms := Statements (Last (Alternatives (N))); 1919 1920 -- For TRUE, generate "expression", not expression = true 1921 1922 if Nkind (Choice) = N_Identifier 1923 and then Entity (Choice) = Standard_True 1924 then 1925 Cond := Expression (N); 1926 1927 -- For FALSE, generate "expression" and switch then/else 1928 1929 elsif Nkind (Choice) = N_Identifier 1930 and then Entity (Choice) = Standard_False 1931 then 1932 Cond := Expression (N); 1933 Else_Stms := Statements (First (Alternatives (N))); 1934 Then_Stms := Statements (Last (Alternatives (N))); 1935 1936 -- For a range, generate "expression in range" 1937 1938 elsif Nkind (Choice) = N_Range 1939 or else (Nkind (Choice) = N_Attribute_Reference 1940 and then Attribute_Name (Choice) = Name_Range) 1941 or else (Is_Entity_Name (Choice) 1942 and then Is_Type (Entity (Choice))) 1943 or else Nkind (Choice) = N_Subtype_Indication 1944 then 1945 Cond := 1946 Make_In (Loc, 1947 Left_Opnd => Expression (N), 1948 Right_Opnd => Relocate_Node (Choice)); 1949 1950 -- For any other subexpression "expression = value" 1951 1952 else 1953 Cond := 1954 Make_Op_Eq (Loc, 1955 Left_Opnd => Expression (N), 1956 Right_Opnd => Relocate_Node (Choice)); 1957 end if; 1958 1959 -- Now rewrite the case as an IF 1960 1961 Rewrite (N, 1962 Make_If_Statement (Loc, 1963 Condition => Cond, 1964 Then_Statements => Then_Stms, 1965 Else_Statements => Else_Stms)); 1966 Analyze (N); 1967 return; 1968 end if; 1969 end if; 1970 1971 -- If the last alternative is not an Others choice, replace it 1972 -- with an N_Others_Choice. Note that we do not bother to call 1973 -- Analyze on the modified case statement, since it's only effect 1974 -- would be to compute the contents of the Others_Discrete_Choices 1975 -- which is not needed by the back end anyway. 1976 1977 -- The reason we do this is that the back end always needs some 1978 -- default for a switch, so if we have not supplied one in the 1979 -- processing above for validity checking, then we need to 1980 -- supply one here. 1981 1982 if not Others_Present then 1983 Others_Node := Make_Others_Choice (Sloc (Last_Alt)); 1984 Set_Others_Discrete_Choices 1985 (Others_Node, Discrete_Choices (Last_Alt)); 1986 Set_Discrete_Choices (Last_Alt, New_List (Others_Node)); 1987 end if; 1988 end; 1989 end Expand_N_Case_Statement; 1990 1991 ----------------------------- 1992 -- Expand_N_Exit_Statement -- 1993 ----------------------------- 1994 1995 -- The only processing required is to deal with a possible C/Fortran 1996 -- boolean value used as the condition for the exit statement. 1997 1998 procedure Expand_N_Exit_Statement (N : Node_Id) is 1999 begin 2000 Adjust_Condition (Condition (N)); 2001 end Expand_N_Exit_Statement; 2002 2003 ----------------------------- 2004 -- Expand_N_Goto_Statement -- 2005 ----------------------------- 2006 2007 -- Add poll before goto if polling active 2008 2009 procedure Expand_N_Goto_Statement (N : Node_Id) is 2010 begin 2011 Generate_Poll_Call (N); 2012 end Expand_N_Goto_Statement; 2013 2014 --------------------------- 2015 -- Expand_N_If_Statement -- 2016 --------------------------- 2017 2018 -- First we deal with the case of C and Fortran convention boolean 2019 -- values, with zero/non-zero semantics. 2020 2021 -- Second, we deal with the obvious rewriting for the cases where the 2022 -- condition of the IF is known at compile time to be True or False. 2023 2024 -- Third, we remove elsif parts which have non-empty Condition_Actions 2025 -- and rewrite as independent if statements. For example: 2026 2027 -- if x then xs 2028 -- elsif y then ys 2029 -- ... 2030 -- end if; 2031 2032 -- becomes 2033 -- 2034 -- if x then xs 2035 -- else 2036 -- <<condition actions of y>> 2037 -- if y then ys 2038 -- ... 2039 -- end if; 2040 -- end if; 2041 2042 -- This rewriting is needed if at least one elsif part has a non-empty 2043 -- Condition_Actions list. We also do the same processing if there is 2044 -- a constant condition in an elsif part (in conjunction with the first 2045 -- processing step mentioned above, for the recursive call made to deal 2046 -- with the created inner if, this deals with properly optimizing the 2047 -- cases of constant elsif conditions). 2048 2049 procedure Expand_N_If_Statement (N : Node_Id) is 2050 Loc : constant Source_Ptr := Sloc (N); 2051 Hed : Node_Id; 2052 E : Node_Id; 2053 New_If : Node_Id; 2054 2055 begin 2056 Adjust_Condition (Condition (N)); 2057 2058 -- The following loop deals with constant conditions for the IF. We 2059 -- need a loop because as we eliminate False conditions, we grab the 2060 -- first elsif condition and use it as the primary condition. 2061 2062 while Compile_Time_Known_Value (Condition (N)) loop 2063 2064 -- If condition is True, we can simply rewrite the if statement 2065 -- now by replacing it by the series of then statements. 2066 2067 if Is_True (Expr_Value (Condition (N))) then 2068 2069 -- All the else parts can be killed 2070 2071 Kill_Dead_Code (Elsif_Parts (N)); 2072 Kill_Dead_Code (Else_Statements (N)); 2073 2074 Hed := Remove_Head (Then_Statements (N)); 2075 Insert_List_After (N, Then_Statements (N)); 2076 Rewrite (N, Hed); 2077 return; 2078 2079 -- If condition is False, then we can delete the condition and 2080 -- the Then statements 2081 2082 else 2083 -- We do not delete the condition if constant condition 2084 -- warnings are enabled, since otherwise we end up deleting 2085 -- the desired warning. Of course the backend will get rid 2086 -- of this True/False test anyway, so nothing is lost here. 2087 2088 if not Constant_Condition_Warnings then 2089 Kill_Dead_Code (Condition (N)); 2090 end if; 2091 2092 Kill_Dead_Code (Then_Statements (N)); 2093 2094 -- If there are no elsif statements, then we simply replace 2095 -- the entire if statement by the sequence of else statements. 2096 2097 if No (Elsif_Parts (N)) then 2098 2099 if No (Else_Statements (N)) 2100 or else Is_Empty_List (Else_Statements (N)) 2101 then 2102 Rewrite (N, 2103 Make_Null_Statement (Sloc (N))); 2104 2105 else 2106 Hed := Remove_Head (Else_Statements (N)); 2107 Insert_List_After (N, Else_Statements (N)); 2108 Rewrite (N, Hed); 2109 end if; 2110 2111 return; 2112 2113 -- If there are elsif statements, the first of them becomes 2114 -- the if/then section of the rebuilt if statement This is 2115 -- the case where we loop to reprocess this copied condition. 2116 2117 else 2118 Hed := Remove_Head (Elsif_Parts (N)); 2119 Insert_Actions (N, Condition_Actions (Hed)); 2120 Set_Condition (N, Condition (Hed)); 2121 Set_Then_Statements (N, Then_Statements (Hed)); 2122 2123 if Is_Empty_List (Elsif_Parts (N)) then 2124 Set_Elsif_Parts (N, No_List); 2125 end if; 2126 end if; 2127 end if; 2128 end loop; 2129 2130 -- Loop through elsif parts, dealing with constant conditions and 2131 -- possible expression actions that are present. 2132 2133 if Present (Elsif_Parts (N)) then 2134 E := First (Elsif_Parts (N)); 2135 while Present (E) loop 2136 Adjust_Condition (Condition (E)); 2137 2138 -- If there are condition actions, then we rewrite the if 2139 -- statement as indicated above. We also do the same rewrite 2140 -- if the condition is True or False. The further processing 2141 -- of this constant condition is then done by the recursive 2142 -- call to expand the newly created if statement 2143 2144 if Present (Condition_Actions (E)) 2145 or else Compile_Time_Known_Value (Condition (E)) 2146 then 2147 -- Note this is not an implicit if statement, since it is 2148 -- part of an explicit if statement in the source (or of an 2149 -- implicit if statement that has already been tested). 2150 2151 New_If := 2152 Make_If_Statement (Sloc (E), 2153 Condition => Condition (E), 2154 Then_Statements => Then_Statements (E), 2155 Elsif_Parts => No_List, 2156 Else_Statements => Else_Statements (N)); 2157 2158 -- Elsif parts for new if come from remaining elsif's of parent 2159 2160 while Present (Next (E)) loop 2161 if No (Elsif_Parts (New_If)) then 2162 Set_Elsif_Parts (New_If, New_List); 2163 end if; 2164 2165 Append (Remove_Next (E), Elsif_Parts (New_If)); 2166 end loop; 2167 2168 Set_Else_Statements (N, New_List (New_If)); 2169 2170 if Present (Condition_Actions (E)) then 2171 Insert_List_Before (New_If, Condition_Actions (E)); 2172 end if; 2173 2174 Remove (E); 2175 2176 if Is_Empty_List (Elsif_Parts (N)) then 2177 Set_Elsif_Parts (N, No_List); 2178 end if; 2179 2180 Analyze (New_If); 2181 return; 2182 2183 -- No special processing for that elsif part, move to next 2184 2185 else 2186 Next (E); 2187 end if; 2188 end loop; 2189 end if; 2190 2191 -- Some more optimizations applicable if we still have an IF statement 2192 2193 if Nkind (N) /= N_If_Statement then 2194 return; 2195 end if; 2196 2197 -- Another optimization, special cases that can be simplified 2198 2199 -- if expression then 2200 -- return true; 2201 -- else 2202 -- return false; 2203 -- end if; 2204 2205 -- can be changed to: 2206 2207 -- return expression; 2208 2209 -- and 2210 2211 -- if expression then 2212 -- return false; 2213 -- else 2214 -- return true; 2215 -- end if; 2216 2217 -- can be changed to: 2218 2219 -- return not (expression); 2220 2221 if Nkind (N) = N_If_Statement 2222 and then No (Elsif_Parts (N)) 2223 and then Present (Else_Statements (N)) 2224 and then List_Length (Then_Statements (N)) = 1 2225 and then List_Length (Else_Statements (N)) = 1 2226 then 2227 declare 2228 Then_Stm : constant Node_Id := First (Then_Statements (N)); 2229 Else_Stm : constant Node_Id := First (Else_Statements (N)); 2230 2231 begin 2232 if Nkind (Then_Stm) = N_Return_Statement 2233 and then 2234 Nkind (Else_Stm) = N_Return_Statement 2235 then 2236 declare 2237 Then_Expr : constant Node_Id := Expression (Then_Stm); 2238 Else_Expr : constant Node_Id := Expression (Else_Stm); 2239 2240 begin 2241 if Nkind (Then_Expr) = N_Identifier 2242 and then 2243 Nkind (Else_Expr) = N_Identifier 2244 then 2245 if Entity (Then_Expr) = Standard_True 2246 and then Entity (Else_Expr) = Standard_False 2247 then 2248 Rewrite (N, 2249 Make_Return_Statement (Loc, 2250 Expression => Relocate_Node (Condition (N)))); 2251 Analyze (N); 2252 return; 2253 2254 elsif Entity (Then_Expr) = Standard_False 2255 and then Entity (Else_Expr) = Standard_True 2256 then 2257 Rewrite (N, 2258 Make_Return_Statement (Loc, 2259 Expression => 2260 Make_Op_Not (Loc, 2261 Right_Opnd => Relocate_Node (Condition (N))))); 2262 Analyze (N); 2263 return; 2264 end if; 2265 end if; 2266 end; 2267 end if; 2268 end; 2269 end if; 2270 end Expand_N_If_Statement; 2271 2272 ----------------------------- 2273 -- Expand_N_Loop_Statement -- 2274 ----------------------------- 2275 2276 -- 1. Deal with while condition for C/Fortran boolean 2277 -- 2. Deal with loops with a non-standard enumeration type range 2278 -- 3. Deal with while loops where Condition_Actions is set 2279 -- 4. Insert polling call if required 2280 2281 procedure Expand_N_Loop_Statement (N : Node_Id) is 2282 Loc : constant Source_Ptr := Sloc (N); 2283 Isc : constant Node_Id := Iteration_Scheme (N); 2284 2285 begin 2286 if Present (Isc) then 2287 Adjust_Condition (Condition (Isc)); 2288 end if; 2289 2290 if Is_Non_Empty_List (Statements (N)) then 2291 Generate_Poll_Call (First (Statements (N))); 2292 end if; 2293 2294 if No (Isc) then 2295 return; 2296 end if; 2297 2298 -- Handle the case where we have a for loop with the range type being 2299 -- an enumeration type with non-standard representation. In this case 2300 -- we expand: 2301 2302 -- for x in [reverse] a .. b loop 2303 -- ... 2304 -- end loop; 2305 2306 -- to 2307 2308 -- for xP in [reverse] integer 2309 -- range etype'Pos (a) .. etype'Pos (b) loop 2310 -- declare 2311 -- x : constant etype := Pos_To_Rep (xP); 2312 -- begin 2313 -- ... 2314 -- end; 2315 -- end loop; 2316 2317 if Present (Loop_Parameter_Specification (Isc)) then 2318 declare 2319 LPS : constant Node_Id := Loop_Parameter_Specification (Isc); 2320 Loop_Id : constant Entity_Id := Defining_Identifier (LPS); 2321 Ltype : constant Entity_Id := Etype (Loop_Id); 2322 Btype : constant Entity_Id := Base_Type (Ltype); 2323 Expr : Node_Id; 2324 New_Id : Entity_Id; 2325 2326 begin 2327 if not Is_Enumeration_Type (Btype) 2328 or else No (Enum_Pos_To_Rep (Btype)) 2329 then 2330 return; 2331 end if; 2332 2333 New_Id := 2334 Make_Defining_Identifier (Loc, 2335 Chars => New_External_Name (Chars (Loop_Id), 'P')); 2336 2337 -- If the type has a contiguous representation, successive 2338 -- values can be generated as offsets from the first literal. 2339 2340 if Has_Contiguous_Rep (Btype) then 2341 Expr := 2342 Unchecked_Convert_To (Btype, 2343 Make_Op_Add (Loc, 2344 Left_Opnd => 2345 Make_Integer_Literal (Loc, 2346 Enumeration_Rep (First_Literal (Btype))), 2347 Right_Opnd => New_Reference_To (New_Id, Loc))); 2348 else 2349 -- Use the constructed array Enum_Pos_To_Rep. 2350 2351 Expr := 2352 Make_Indexed_Component (Loc, 2353 Prefix => New_Reference_To (Enum_Pos_To_Rep (Btype), Loc), 2354 Expressions => New_List (New_Reference_To (New_Id, Loc))); 2355 end if; 2356 2357 Rewrite (N, 2358 Make_Loop_Statement (Loc, 2359 Identifier => Identifier (N), 2360 2361 Iteration_Scheme => 2362 Make_Iteration_Scheme (Loc, 2363 Loop_Parameter_Specification => 2364 Make_Loop_Parameter_Specification (Loc, 2365 Defining_Identifier => New_Id, 2366 Reverse_Present => Reverse_Present (LPS), 2367 2368 Discrete_Subtype_Definition => 2369 Make_Subtype_Indication (Loc, 2370 2371 Subtype_Mark => 2372 New_Reference_To (Standard_Natural, Loc), 2373 2374 Constraint => 2375 Make_Range_Constraint (Loc, 2376 Range_Expression => 2377 Make_Range (Loc, 2378 2379 Low_Bound => 2380 Make_Attribute_Reference (Loc, 2381 Prefix => 2382 New_Reference_To (Btype, Loc), 2383 2384 Attribute_Name => Name_Pos, 2385 2386 Expressions => New_List ( 2387 Relocate_Node 2388 (Type_Low_Bound (Ltype)))), 2389 2390 High_Bound => 2391 Make_Attribute_Reference (Loc, 2392 Prefix => 2393 New_Reference_To (Btype, Loc), 2394 2395 Attribute_Name => Name_Pos, 2396 2397 Expressions => New_List ( 2398 Relocate_Node 2399 (Type_High_Bound (Ltype))))))))), 2400 2401 Statements => New_List ( 2402 Make_Block_Statement (Loc, 2403 Declarations => New_List ( 2404 Make_Object_Declaration (Loc, 2405 Defining_Identifier => Loop_Id, 2406 Constant_Present => True, 2407 Object_Definition => New_Reference_To (Ltype, Loc), 2408 Expression => Expr)), 2409 2410 Handled_Statement_Sequence => 2411 Make_Handled_Sequence_Of_Statements (Loc, 2412 Statements => Statements (N)))), 2413 2414 End_Label => End_Label (N))); 2415 Analyze (N); 2416 end; 2417 2418 -- Second case, if we have a while loop with Condition_Actions set, 2419 -- then we change it into a plain loop: 2420 2421 -- while C loop 2422 -- ... 2423 -- end loop; 2424 2425 -- changed to: 2426 2427 -- loop 2428 -- <<condition actions>> 2429 -- exit when not C; 2430 -- ... 2431 -- end loop 2432 2433 elsif Present (Isc) 2434 and then Present (Condition_Actions (Isc)) 2435 then 2436 declare 2437 ES : Node_Id; 2438 2439 begin 2440 ES := 2441 Make_Exit_Statement (Sloc (Condition (Isc)), 2442 Condition => 2443 Make_Op_Not (Sloc (Condition (Isc)), 2444 Right_Opnd => Condition (Isc))); 2445 2446 Prepend (ES, Statements (N)); 2447 Insert_List_Before (ES, Condition_Actions (Isc)); 2448 2449 -- This is not an implicit loop, since it is generated in 2450 -- response to the loop statement being processed. If this 2451 -- is itself implicit, the restriction has already been 2452 -- checked. If not, it is an explicit loop. 2453 2454 Rewrite (N, 2455 Make_Loop_Statement (Sloc (N), 2456 Identifier => Identifier (N), 2457 Statements => Statements (N), 2458 End_Label => End_Label (N))); 2459 2460 Analyze (N); 2461 end; 2462 end if; 2463 end Expand_N_Loop_Statement; 2464 2465 ------------------------------- 2466 -- Expand_N_Return_Statement -- 2467 ------------------------------- 2468 2469 procedure Expand_N_Return_Statement (N : Node_Id) is 2470 Loc : constant Source_Ptr := Sloc (N); 2471 Exp : constant Node_Id := Expression (N); 2472 Exptyp : Entity_Id; 2473 T : Entity_Id; 2474 Utyp : Entity_Id; 2475 Scope_Id : Entity_Id; 2476 Kind : Entity_Kind; 2477 Call : Node_Id; 2478 Acc_Stat : Node_Id; 2479 Goto_Stat : Node_Id; 2480 Lab_Node : Node_Id; 2481 Cur_Idx : Nat; 2482 Return_Type : Entity_Id; 2483 Result_Exp : Node_Id; 2484 Result_Id : Entity_Id; 2485 Result_Obj : Node_Id; 2486 2487 begin 2488 -- Case where returned expression is present 2489 2490 if Present (Exp) then 2491 2492 -- Always normalize C/Fortran boolean result. This is not always 2493 -- necessary, but it seems a good idea to minimize the passing 2494 -- around of non-normalized values, and in any case this handles 2495 -- the processing of barrier functions for protected types, which 2496 -- turn the condition into a return statement. 2497 2498 Exptyp := Etype (Exp); 2499 2500 if Is_Boolean_Type (Exptyp) 2501 and then Nonzero_Is_True (Exptyp) 2502 then 2503 Adjust_Condition (Exp); 2504 Adjust_Result_Type (Exp, Exptyp); 2505 end if; 2506 2507 -- Do validity check if enabled for returns 2508 2509 if Validity_Checks_On 2510 and then Validity_Check_Returns 2511 then 2512 Ensure_Valid (Exp); 2513 end if; 2514 end if; 2515 2516 -- Find relevant enclosing scope from which return is returning 2517 2518 Cur_Idx := Scope_Stack.Last; 2519 loop 2520 Scope_Id := Scope_Stack.Table (Cur_Idx).Entity; 2521 2522 if Ekind (Scope_Id) /= E_Block 2523 and then Ekind (Scope_Id) /= E_Loop 2524 then 2525 exit; 2526 2527 else 2528 Cur_Idx := Cur_Idx - 1; 2529 pragma Assert (Cur_Idx >= 0); 2530 end if; 2531 end loop; 2532 2533 if No (Exp) then 2534 Kind := Ekind (Scope_Id); 2535 2536 -- If it is a return from procedures do no extra steps. 2537 2538 if Kind = E_Procedure or else Kind = E_Generic_Procedure then 2539 return; 2540 end if; 2541 2542 pragma Assert (Is_Entry (Scope_Id)); 2543 2544 -- Look at the enclosing block to see whether the return is from 2545 -- an accept statement or an entry body. 2546 2547 for J in reverse 0 .. Cur_Idx loop 2548 Scope_Id := Scope_Stack.Table (J).Entity; 2549 exit when Is_Concurrent_Type (Scope_Id); 2550 end loop; 2551 2552 -- If it is a return from accept statement it should be expanded 2553 -- as a call to RTS Complete_Rendezvous and a goto to the end of 2554 -- the accept body. 2555 2556 -- (cf : Expand_N_Accept_Statement, Expand_N_Selective_Accept, 2557 -- Expand_N_Accept_Alternative in exp_ch9.adb) 2558 2559 if Is_Task_Type (Scope_Id) then 2560 2561 Call := (Make_Procedure_Call_Statement (Loc, 2562 Name => New_Reference_To 2563 (RTE (RE_Complete_Rendezvous), Loc))); 2564 Insert_Before (N, Call); 2565 -- why not insert actions here??? 2566 Analyze (Call); 2567 2568 Acc_Stat := Parent (N); 2569 while Nkind (Acc_Stat) /= N_Accept_Statement loop 2570 Acc_Stat := Parent (Acc_Stat); 2571 end loop; 2572 2573 Lab_Node := Last (Statements 2574 (Handled_Statement_Sequence (Acc_Stat))); 2575 2576 Goto_Stat := Make_Goto_Statement (Loc, 2577 Name => New_Occurrence_Of 2578 (Entity (Identifier (Lab_Node)), Loc)); 2579 2580 Set_Analyzed (Goto_Stat); 2581 2582 Rewrite (N, Goto_Stat); 2583 Analyze (N); 2584 2585 -- If it is a return from an entry body, put a Complete_Entry_Body 2586 -- call in front of the return. 2587 2588 elsif Is_Protected_Type (Scope_Id) then 2589 2590 Call := 2591 Make_Procedure_Call_Statement (Loc, 2592 Name => New_Reference_To 2593 (RTE (RE_Complete_Entry_Body), Loc), 2594 Parameter_Associations => New_List 2595 (Make_Attribute_Reference (Loc, 2596 Prefix => 2597 New_Reference_To 2598 (Object_Ref 2599 (Corresponding_Body (Parent (Scope_Id))), 2600 Loc), 2601 Attribute_Name => Name_Unchecked_Access))); 2602 2603 Insert_Before (N, Call); 2604 Analyze (Call); 2605 2606 end if; 2607 2608 return; 2609 end if; 2610 2611 T := Etype (Exp); 2612 Return_Type := Etype (Scope_Id); 2613 Utyp := Underlying_Type (Return_Type); 2614 2615 -- Check the result expression of a scalar function against 2616 -- the subtype of the function by inserting a conversion. 2617 -- This conversion must eventually be performed for other 2618 -- classes of types, but for now it's only done for scalars. 2619 -- ??? 2620 2621 if Is_Scalar_Type (T) then 2622 Rewrite (Exp, Convert_To (Return_Type, Exp)); 2623 Analyze (Exp); 2624 end if; 2625 2626 -- Implement the rules of 6.5(8-10), which require a tag check in 2627 -- the case of a limited tagged return type, and tag reassignment 2628 -- for nonlimited tagged results. These actions are needed when 2629 -- the return type is a specific tagged type and the result 2630 -- expression is a conversion or a formal parameter, because in 2631 -- that case the tag of the expression might differ from the tag 2632 -- of the specific result type. 2633 2634 if Is_Tagged_Type (Utyp) 2635 and then not Is_Class_Wide_Type (Utyp) 2636 and then (Nkind (Exp) = N_Type_Conversion 2637 or else Nkind (Exp) = N_Unchecked_Type_Conversion 2638 or else (Is_Entity_Name (Exp) 2639 and then Ekind (Entity (Exp)) in Formal_Kind)) 2640 then 2641 -- When the return type is limited, perform a check that the 2642 -- tag of the result is the same as the tag of the return type. 2643 2644 if Is_Limited_Type (Return_Type) then 2645 Insert_Action (Exp, 2646 Make_Raise_Constraint_Error (Loc, 2647 Condition => 2648 Make_Op_Ne (Loc, 2649 Left_Opnd => 2650 Make_Selected_Component (Loc, 2651 Prefix => Duplicate_Subexpr (Exp), 2652 Selector_Name => 2653 New_Reference_To (Tag_Component (Utyp), Loc)), 2654 Right_Opnd => 2655 Unchecked_Convert_To (RTE (RE_Tag), 2656 New_Reference_To 2657 (Access_Disp_Table (Base_Type (Utyp)), Loc))), 2658 Reason => CE_Tag_Check_Failed)); 2659 2660 -- If the result type is a specific nonlimited tagged type, 2661 -- then we have to ensure that the tag of the result is that 2662 -- of the result type. This is handled by making a copy of the 2663 -- expression in the case where it might have a different tag, 2664 -- namely when the expression is a conversion or a formal 2665 -- parameter. We create a new object of the result type and 2666 -- initialize it from the expression, which will implicitly 2667 -- force the tag to be set appropriately. 2668 2669 else 2670 Result_Id := 2671 Make_Defining_Identifier (Loc, New_Internal_Name ('R')); 2672 Result_Exp := New_Reference_To (Result_Id, Loc); 2673 2674 Result_Obj := 2675 Make_Object_Declaration (Loc, 2676 Defining_Identifier => Result_Id, 2677 Object_Definition => New_Reference_To (Return_Type, Loc), 2678 Constant_Present => True, 2679 Expression => Relocate_Node (Exp)); 2680 2681 Set_Assignment_OK (Result_Obj); 2682 Insert_Action (Exp, Result_Obj); 2683 2684 Rewrite (Exp, Result_Exp); 2685 Analyze_And_Resolve (Exp, Return_Type); 2686 end if; 2687 end if; 2688 2689 -- Deal with returning variable length objects and controlled types 2690 2691 -- Nothing to do if we are returning by reference, or this is not 2692 -- a type that requires special processing (indicated by the fact 2693 -- that it requires a cleanup scope for the secondary stack case) 2694 2695 if Is_Return_By_Reference_Type (T) 2696 or else not Requires_Transient_Scope (Return_Type) 2697 then 2698 null; 2699 2700 -- Case of secondary stack not used 2701 2702 elsif Function_Returns_With_DSP (Scope_Id) then 2703 2704 -- Here what we need to do is to always return by reference, since 2705 -- we will return with the stack pointer depressed. We may need to 2706 -- do a copy to a local temporary before doing this return. 2707 2708 No_Secondary_Stack_Case : declare 2709 Local_Copy_Required : Boolean := False; 2710 -- Set to True if a local copy is required 2711 2712 Copy_Ent : Entity_Id; 2713 -- Used for the target entity if a copy is required 2714 2715 Decl : Node_Id; 2716 -- Declaration used to create copy if needed 2717 2718 procedure Test_Copy_Required (Expr : Node_Id); 2719 -- Determines if Expr represents a return value for which a 2720 -- copy is required. More specifically, a copy is not required 2721 -- if Expr represents an object or component of an object that 2722 -- is either in the local subprogram frame, or is constant. 2723 -- If a copy is required, then Local_Copy_Required is set True. 2724 2725 ------------------------ 2726 -- Test_Copy_Required -- 2727 ------------------------ 2728 2729 procedure Test_Copy_Required (Expr : Node_Id) is 2730 Ent : Entity_Id; 2731 2732 begin 2733 -- If component, test prefix (object containing component) 2734 2735 if Nkind (Expr) = N_Indexed_Component 2736 or else 2737 Nkind (Expr) = N_Selected_Component 2738 then 2739 Test_Copy_Required (Prefix (Expr)); 2740 return; 2741 2742 -- See if we have an entity name 2743 2744 elsif Is_Entity_Name (Expr) then 2745 Ent := Entity (Expr); 2746 2747 -- Constant entity is always OK, no copy required 2748 2749 if Ekind (Ent) = E_Constant then 2750 return; 2751 2752 -- No copy required for local variable 2753 2754 elsif Ekind (Ent) = E_Variable 2755 and then Scope (Ent) = Current_Subprogram 2756 then 2757 return; 2758 end if; 2759 end if; 2760 2761 -- All other cases require a copy 2762 2763 Local_Copy_Required := True; 2764 end Test_Copy_Required; 2765 2766 -- Start of processing for No_Secondary_Stack_Case 2767 2768 begin 2769 -- No copy needed if result is from a function call. 2770 -- In this case the result is already being returned by 2771 -- reference with the stack pointer depressed. 2772 2773 -- To make up for a gcc 2.8.1 deficiency (???), we perform 2774 -- the copy for array types if the constrained status of the 2775 -- target type is different from that of the expression. 2776 2777 if Requires_Transient_Scope (T) 2778 and then 2779 (not Is_Array_Type (T) 2780 or else Is_Constrained (T) = Is_Constrained (Return_Type) 2781 or else Controlled_Type (T)) 2782 and then Nkind (Exp) = N_Function_Call 2783 then 2784 Set_By_Ref (N); 2785 2786 -- We always need a local copy for a controlled type, since 2787 -- we are required to finalize the local value before return. 2788 -- The copy will automatically include the required finalize. 2789 -- Moreover, gigi cannot make this copy, since we need special 2790 -- processing to ensure proper behavior for finalization. 2791 2792 -- Note: the reason we are returning with a depressed stack 2793 -- pointer in the controlled case (even if the type involved 2794 -- is constrained) is that we must make a local copy to deal 2795 -- properly with the requirement that the local result be 2796 -- finalized. 2797 2798 elsif Controlled_Type (Utyp) then 2799 Copy_Ent := 2800 Make_Defining_Identifier (Loc, 2801 Chars => New_Internal_Name ('R')); 2802 2803 -- Build declaration to do the copy, and insert it, setting 2804 -- Assignment_OK, because we may be copying a limited type. 2805 -- In addition we set the special flag to inhibit finalize 2806 -- attachment if this is a controlled type (since this attach 2807 -- must be done by the caller, otherwise if we attach it here 2808 -- we will finalize the returned result prematurely). 2809 2810 Decl := 2811 Make_Object_Declaration (Loc, 2812 Defining_Identifier => Copy_Ent, 2813 Object_Definition => New_Occurrence_Of (Return_Type, Loc), 2814 Expression => Relocate_Node (Exp)); 2815 2816 Set_Assignment_OK (Decl); 2817 Set_Delay_Finalize_Attach (Decl); 2818 Insert_Action (N, Decl); 2819 2820 -- Now the actual return uses the copied value 2821 2822 Rewrite (Exp, New_Occurrence_Of (Copy_Ent, Loc)); 2823 Analyze_And_Resolve (Exp, Return_Type); 2824 2825 -- Since we have made the copy, gigi does not have to, so 2826 -- we set the By_Ref flag to prevent another copy being made. 2827 2828 Set_By_Ref (N); 2829 2830 -- Non-controlled cases 2831 2832 else 2833 Test_Copy_Required (Exp); 2834 2835 -- If a local copy is required, then gigi will make the 2836 -- copy, otherwise, we can return the result directly, 2837 -- so set By_Ref to suppress the gigi copy. 2838 2839 if not Local_Copy_Required then 2840 Set_By_Ref (N); 2841 end if; 2842 end if; 2843 end No_Secondary_Stack_Case; 2844 2845 -- Here if secondary stack is used 2846 2847 else 2848 -- Make sure that no surrounding block will reclaim the 2849 -- secondary-stack on which we are going to put the result. 2850 -- Not only may this introduce secondary stack leaks but worse, 2851 -- if the reclamation is done too early, then the result we are 2852 -- returning may get clobbered. See example in 7417-003. 2853 2854 declare 2855 S : Entity_Id := Current_Scope; 2856 2857 begin 2858 while Ekind (S) = E_Block or else Ekind (S) = E_Loop loop 2859 Set_Sec_Stack_Needed_For_Return (S, True); 2860 S := Enclosing_Dynamic_Scope (S); 2861 end loop; 2862 end; 2863 2864 -- Optimize the case where the result is a function call. In this 2865 -- case either the result is already on the secondary stack, or is 2866 -- already being returned with the stack pointer depressed and no 2867 -- further processing is required except to set the By_Ref flag to 2868 -- ensure that gigi does not attempt an extra unnecessary copy. 2869 -- (actually not just unnecessary but harmfully wrong in the case 2870 -- of a controlled type, where gigi does not know how to do a copy). 2871 -- To make up for a gcc 2.8.1 deficiency (???), we perform 2872 -- the copy for array types if the constrained status of the 2873 -- target type is different from that of the expression. 2874 2875 if Requires_Transient_Scope (T) 2876 and then 2877 (not Is_Array_Type (T) 2878 or else Is_Constrained (T) = Is_Constrained (Return_Type) 2879 or else Controlled_Type (T)) 2880 and then Nkind (Exp) = N_Function_Call 2881 then 2882 Set_By_Ref (N); 2883 2884 -- For controlled types, do the allocation on the sec-stack 2885 -- manually in order to call adjust at the right time 2886 -- type Anon1 is access Return_Type; 2887 -- for Anon1'Storage_pool use ss_pool; 2888 -- Anon2 : anon1 := new Return_Type'(expr); 2889 -- return Anon2.all; 2890 2891 elsif Controlled_Type (Utyp) then 2892 declare 2893 Loc : constant Source_Ptr := Sloc (N); 2894 Temp : constant Entity_Id := 2895 Make_Defining_Identifier (Loc, 2896 Chars => New_Internal_Name ('R')); 2897 Acc_Typ : constant Entity_Id := 2898 Make_Defining_Identifier (Loc, 2899 Chars => New_Internal_Name ('A')); 2900 Alloc_Node : Node_Id; 2901 2902 begin 2903 Set_Ekind (Acc_Typ, E_Access_Type); 2904 2905 Set_Associated_Storage_Pool (Acc_Typ, RTE (RE_SS_Pool)); 2906 2907 Alloc_Node := 2908 Make_Allocator (Loc, 2909 Expression => 2910 Make_Qualified_Expression (Loc, 2911 Subtype_Mark => New_Reference_To (Etype (Exp), Loc), 2912 Expression => Relocate_Node (Exp))); 2913 2914 Insert_List_Before_And_Analyze (N, New_List ( 2915 Make_Full_Type_Declaration (Loc, 2916 Defining_Identifier => Acc_Typ, 2917 Type_Definition => 2918 Make_Access_To_Object_Definition (Loc, 2919 Subtype_Indication => 2920 New_Reference_To (Return_Type, Loc))), 2921 2922 Make_Object_Declaration (Loc, 2923 Defining_Identifier => Temp, 2924 Object_Definition => New_Reference_To (Acc_Typ, Loc), 2925 Expression => Alloc_Node))); 2926 2927 Rewrite (Exp, 2928 Make_Explicit_Dereference (Loc, 2929 Prefix => New_Reference_To (Temp, Loc))); 2930 2931 Analyze_And_Resolve (Exp, Return_Type); 2932 end; 2933 2934 -- Otherwise use the gigi mechanism to allocate result on the 2935 -- secondary stack. 2936 2937 else 2938 Set_Storage_Pool (N, RTE (RE_SS_Pool)); 2939 2940 -- If we are generating code for the Java VM do not use 2941 -- SS_Allocate since everything is heap-allocated anyway. 2942 2943 if not Java_VM then 2944 Set_Procedure_To_Call (N, RTE (RE_SS_Allocate)); 2945 end if; 2946 end if; 2947 end if; 2948 2949 exception 2950 when RE_Not_Available => 2951 return; 2952 end Expand_N_Return_Statement; 2953 2954 ------------------------------ 2955 -- Make_Tag_Ctrl_Assignment -- 2956 ------------------------------ 2957 2958 function Make_Tag_Ctrl_Assignment (N : Node_Id) return List_Id is 2959 Loc : constant Source_Ptr := Sloc (N); 2960 L : constant Node_Id := Name (N); 2961 T : constant Entity_Id := Underlying_Type (Etype (L)); 2962 2963 Ctrl_Act : constant Boolean := Controlled_Type (T) 2964 and then not No_Ctrl_Actions (N); 2965 2966 Save_Tag : constant Boolean := Is_Tagged_Type (T) 2967 and then not No_Ctrl_Actions (N) 2968 and then not Java_VM; 2969 -- Tags are not saved and restored when Java_VM because JVM tags 2970 -- are represented implicitly in objects. 2971 2972 Res : List_Id; 2973 Tag_Tmp : Entity_Id; 2974 Prev_Tmp : Entity_Id; 2975 Next_Tmp : Entity_Id; 2976 Ctrl_Ref : Node_Id; 2977 Ctrl_Ref2 : Node_Id := Empty; 2978 Prev_Tmp2 : Entity_Id := Empty; -- prevent warning 2979 Next_Tmp2 : Entity_Id := Empty; -- prevent warning 2980 2981 begin 2982 Res := New_List; 2983 2984 -- Finalize the target of the assignment when controlled. 2985 -- We have two exceptions here: 2986 2987 -- 1. If we are in an init proc since it is an initialization 2988 -- more than an assignment 2989 2990 -- 2. If the left-hand side is a temporary that was not initialized 2991 -- (or the parent part of a temporary since it is the case in 2992 -- extension aggregates). Such a temporary does not come from 2993 -- source. We must examine the original node for the prefix, because 2994 -- it may be a component of an entry formal, in which case it has 2995 -- been rewritten and does not appear to come from source either. 2996 2997 -- Case of init proc 2998 2999 if not Ctrl_Act then 3000 null; 3001 3002 -- The left hand side is an uninitialized temporary 3003 3004 elsif Nkind (L) = N_Type_Conversion 3005 and then Is_Entity_Name (Expression (L)) 3006 and then No_Initialization (Parent (Entity (Expression (L)))) 3007 then 3008 null; 3009 else 3010 Append_List_To (Res, 3011 Make_Final_Call ( 3012 Ref => Duplicate_Subexpr_No_Checks (L), 3013 Typ => Etype (L), 3014 With_Detach => New_Reference_To (Standard_False, Loc))); 3015 end if; 3016 3017 Next_Tmp := Make_Defining_Identifier (Loc, New_Internal_Name ('C')); 3018 3019 -- Save the Tag in a local variable Tag_Tmp 3020 3021 if Save_Tag then 3022 Tag_Tmp := 3023 Make_Defining_Identifier (Loc, New_Internal_Name ('A')); 3024 3025 Append_To (Res, 3026 Make_Object_Declaration (Loc, 3027 Defining_Identifier => Tag_Tmp, 3028 Object_Definition => New_Reference_To (RTE (RE_Tag), Loc), 3029 Expression => 3030 Make_Selected_Component (Loc, 3031 Prefix => Duplicate_Subexpr_No_Checks (L), 3032 Selector_Name => New_Reference_To (Tag_Component (T), Loc)))); 3033 3034 -- Otherwise Tag_Tmp not used 3035 3036 else 3037 Tag_Tmp := Empty; 3038 end if; 3039 3040 -- Save the Finalization Pointers in local variables Prev_Tmp and 3041 -- Next_Tmp. For objects with Has_Controlled_Component set, these 3042 -- pointers are in the Record_Controller and if it is also 3043 -- Is_Controlled, we need to save the object pointers as well. 3044 3045 if Ctrl_Act then 3046 Ctrl_Ref := Duplicate_Subexpr_No_Checks (L); 3047 3048 if Has_Controlled_Component (T) then 3049 Ctrl_Ref := 3050 Make_Selected_Component (Loc, 3051 Prefix => Ctrl_Ref, 3052 Selector_Name => 3053 New_Reference_To (Controller_Component (T), Loc)); 3054 3055 if Is_Controlled (T) then 3056 Ctrl_Ref2 := Duplicate_Subexpr_No_Checks (L); 3057 end if; 3058 end if; 3059 3060 Prev_Tmp := Make_Defining_Identifier (Loc, New_Internal_Name ('B')); 3061 3062 Append_To (Res, 3063 Make_Object_Declaration (Loc, 3064 Defining_Identifier => Prev_Tmp, 3065 3066 Object_Definition => 3067 New_Reference_To (RTE (RE_Finalizable_Ptr), Loc), 3068 3069 Expression => 3070 Make_Selected_Component (Loc, 3071 Prefix => 3072 Unchecked_Convert_To (RTE (RE_Finalizable), Ctrl_Ref), 3073 Selector_Name => Make_Identifier (Loc, Name_Prev)))); 3074 3075 Next_Tmp := Make_Defining_Identifier (Loc, New_Internal_Name ('C')); 3076 3077 Append_To (Res, 3078 Make_Object_Declaration (Loc, 3079 Defining_Identifier => Next_Tmp, 3080 3081 Object_Definition => 3082 New_Reference_To (RTE (RE_Finalizable_Ptr), Loc), 3083 3084 Expression => 3085 Make_Selected_Component (Loc, 3086 Prefix => 3087 Unchecked_Convert_To (RTE (RE_Finalizable), 3088 New_Copy_Tree (Ctrl_Ref)), 3089 Selector_Name => Make_Identifier (Loc, Name_Next)))); 3090 3091 if Present (Ctrl_Ref2) then 3092 Prev_Tmp2 := 3093 Make_Defining_Identifier (Loc, New_Internal_Name ('B')); 3094 3095 Append_To (Res, 3096 Make_Object_Declaration (Loc, 3097 Defining_Identifier => Prev_Tmp2, 3098 3099 Object_Definition => 3100 New_Reference_To (RTE (RE_Finalizable_Ptr), Loc), 3101 3102 Expression => 3103 Make_Selected_Component (Loc, 3104 Prefix => 3105 Unchecked_Convert_To (RTE (RE_Finalizable), Ctrl_Ref2), 3106 Selector_Name => Make_Identifier (Loc, Name_Prev)))); 3107 3108 Next_Tmp2 := 3109 Make_Defining_Identifier (Loc, New_Internal_Name ('C')); 3110 3111 Append_To (Res, 3112 Make_Object_Declaration (Loc, 3113 Defining_Identifier => Next_Tmp2, 3114 3115 Object_Definition => 3116 New_Reference_To (RTE (RE_Finalizable_Ptr), Loc), 3117 3118 Expression => 3119 Make_Selected_Component (Loc, 3120 Prefix => 3121 Unchecked_Convert_To (RTE (RE_Finalizable), 3122 New_Copy_Tree (Ctrl_Ref2)), 3123 Selector_Name => Make_Identifier (Loc, Name_Next)))); 3124 end if; 3125 3126 -- If not controlled type, then Prev_Tmp and Ctrl_Ref unused 3127 3128 else 3129 Prev_Tmp := Empty; 3130 Ctrl_Ref := Empty; 3131 end if; 3132 3133 -- Do the Assignment 3134 3135 Append_To (Res, Relocate_Node (N)); 3136 3137 -- Restore the Tag 3138 3139 if Save_Tag then 3140 Append_To (Res, 3141 Make_Assignment_Statement (Loc, 3142 Name => 3143 Make_Selected_Component (Loc, 3144 Prefix => Duplicate_Subexpr_No_Checks (L), 3145 Selector_Name => New_Reference_To (Tag_Component (T), Loc)), 3146 Expression => New_Reference_To (Tag_Tmp, Loc))); 3147 end if; 3148 3149 -- Restore the finalization pointers 3150 3151 if Ctrl_Act then 3152 Append_To (Res, 3153 Make_Assignment_Statement (Loc, 3154 Name => 3155 Make_Selected_Component (Loc, 3156 Prefix => 3157 Unchecked_Convert_To (RTE (RE_Finalizable), 3158 New_Copy_Tree (Ctrl_Ref)), 3159 Selector_Name => Make_Identifier (Loc, Name_Prev)), 3160 Expression => New_Reference_To (Prev_Tmp, Loc))); 3161 3162 Append_To (Res, 3163 Make_Assignment_Statement (Loc, 3164 Name => 3165 Make_Selected_Component (Loc, 3166 Prefix => 3167 Unchecked_Convert_To (RTE (RE_Finalizable), 3168 New_Copy_Tree (Ctrl_Ref)), 3169 Selector_Name => Make_Identifier (Loc, Name_Next)), 3170 Expression => New_Reference_To (Next_Tmp, Loc))); 3171 3172 if Present (Ctrl_Ref2) then 3173 Append_To (Res, 3174 Make_Assignment_Statement (Loc, 3175 Name => 3176 Make_Selected_Component (Loc, 3177 Prefix => 3178 Unchecked_Convert_To (RTE (RE_Finalizable), 3179 New_Copy_Tree (Ctrl_Ref2)), 3180 Selector_Name => Make_Identifier (Loc, Name_Prev)), 3181 Expression => New_Reference_To (Prev_Tmp2, Loc))); 3182 3183 Append_To (Res, 3184 Make_Assignment_Statement (Loc, 3185 Name => 3186 Make_Selected_Component (Loc, 3187 Prefix => 3188 Unchecked_Convert_To (RTE (RE_Finalizable), 3189 New_Copy_Tree (Ctrl_Ref2)), 3190 Selector_Name => Make_Identifier (Loc, Name_Next)), 3191 Expression => New_Reference_To (Next_Tmp2, Loc))); 3192 end if; 3193 end if; 3194 3195 -- Adjust the target after the assignment when controlled. (not in 3196 -- the init proc since it is an initialization more than an 3197 -- assignment) 3198 3199 if Ctrl_Act then 3200 Append_List_To (Res, 3201 Make_Adjust_Call ( 3202 Ref => Duplicate_Subexpr_Move_Checks (L), 3203 Typ => Etype (L), 3204 Flist_Ref => New_Reference_To (RTE (RE_Global_Final_List), Loc), 3205 With_Attach => Make_Integer_Literal (Loc, 0))); 3206 end if; 3207 3208 return Res; 3209 3210 exception 3211 when RE_Not_Available => 3212 return Empty_List; 3213 end Make_Tag_Ctrl_Assignment; 3214 3215 ------------------------------------ 3216 -- Possible_Bit_Aligned_Component -- 3217 ------------------------------------ 3218 3219 function Possible_Bit_Aligned_Component (N : Node_Id) return Boolean is 3220 begin 3221 case Nkind (N) is 3222 3223 -- Case of indexed component 3224 3225 when N_Indexed_Component => 3226 declare 3227 P : constant Node_Id := Prefix (N); 3228 Ptyp : constant Entity_Id := Etype (P); 3229 3230 begin 3231 -- If we know the component size and it is less than 64, then 3232 -- we are definitely OK. The back end always does assignment 3233 -- of misaligned small objects correctly. 3234 3235 if Known_Static_Component_Size (Ptyp) 3236 and then Component_Size (Ptyp) <= 64 3237 then 3238 return False; 3239 3240 -- Otherwise, we need to test the prefix, to see if we are 3241 -- indexing from a possibly unaligned component. 3242 3243 else 3244 return Possible_Bit_Aligned_Component (P); 3245 end if; 3246 end; 3247 3248 -- Case of selected component 3249 3250 when N_Selected_Component => 3251 declare 3252 P : constant Node_Id := Prefix (N); 3253 Comp : constant Entity_Id := Entity (Selector_Name (N)); 3254 3255 begin 3256 -- If there is no component clause, then we are in the clear 3257 -- since the back end will never misalign a large component 3258 -- unless it is forced to do so. In the clear means we need 3259 -- only the recursive test on the prefix. 3260 3261 if Component_May_Be_Bit_Aligned (Comp) then 3262 return True; 3263 else 3264 return Possible_Bit_Aligned_Component (P); 3265 end if; 3266 end; 3267 3268 -- If we have neither a record nor array component, it means that 3269 -- we have fallen off the top testing prefixes recursively, and 3270 -- we now have a stand alone object, where we don't have a problem 3271 3272 when others => 3273 return False; 3274 3275 end case; 3276 end Possible_Bit_Aligned_Component; 3277 3278end Exp_Ch5; 3279