gcc/ada/utils2.c

   1 /****************************************************************************
   2  *                                                                          *
   3  *                         GNAT COMPILER COMPONENTS                         *
   4  *                                                                          *
   5  *                               U T I L S 2                                *
   6  *                                                                          *
   7  *                          C Implementation File                           *
   8  *                                                                          *
   9  *          Copyright (C) 1992-2006, 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,  51  Franklin  Street,  Fifth  Floor, *
  20  * Boston, MA 02110-1301, 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
  27 #include "config.h"
  28 #include "system.h"
  29 #include "coretypes.h"
  30 #include "tm.h"
  31 #include "tree.h"
  32 #include "rtl.h"
  33 #include "ggc.h"
  34 #include "flags.h"
  35 #include "output.h"
  36 #include "ada.h"
  37 #include "types.h"
  38 #include "atree.h"
  39 #include "stringt.h"
  40 #include "namet.h"
  41 #include "uintp.h"
  42 #include "fe.h"
  43 #include "elists.h"
  44 #include "nlists.h"
  45 #include "sinfo.h"
  46 #include "einfo.h"
  47 #include "ada-tree.h"
  48 #include "gigi.h"
  49
  50 static tree find_common_type (tree, tree);
  51 static bool contains_save_expr_p (tree);
  52 static tree contains_null_expr (tree);
  53 static tree compare_arrays (tree, tree, tree);
  54 static tree nonbinary_modular_operation (enum tree_code, tree, tree, tree);
  55 static tree build_simple_component_ref (tree, tree, tree, bool);
  56 \f
  57 /* Prepare expr to be an argument of a TRUTH_NOT_EXPR or other logical
  58    operation.
  59
  60    This preparation consists of taking the ordinary representation of
  61    an expression expr and producing a valid tree boolean expression
  62    describing whether expr is nonzero. We could simply always do
  63
  64       build_binary_op (NE_EXPR, expr, integer_zero_node, 1),
  65
  66    but we optimize comparisons, &&, ||, and !.
  67
  68    The resulting type should always be the same as the input type.
  69    This function is simpler than the corresponding C version since
  70    the only possible operands will be things of Boolean type.  */
  71
  72 tree
  73 gnat_truthvalue_conversion (tree expr)
  74 {
  75   tree type = TREE_TYPE (expr);
  76
  77   switch (TREE_CODE (expr))
  78     {
  79     case EQ_EXPR:  case NE_EXPR: case LE_EXPR: case GE_EXPR:
  80     case LT_EXPR:  case GT_EXPR:
  81     case TRUTH_ANDIF_EXPR:
  82     case TRUTH_ORIF_EXPR:
  83     case TRUTH_AND_EXPR:
  84     case TRUTH_OR_EXPR:
  85     case TRUTH_XOR_EXPR:
  86     case ERROR_MARK:
  87       return expr;
  88
  89     case INTEGER_CST:
  90       return (integer_zerop (expr) ? convert (type, integer_zero_node)
  91               : convert (type, integer_one_node));
  92
  93     case REAL_CST:
  94       return (real_zerop (expr) ? convert (type, integer_zero_node)
  95               : convert (type, integer_one_node));
  96
  97     case COND_EXPR:
  98       /* Distribute the conversion into the arms of a COND_EXPR.  */
  99       return fold
 100         (build3 (COND_EXPR, type, TREE_OPERAND (expr, 0),
 101                  gnat_truthvalue_conversion (TREE_OPERAND (expr, 1)),
 102                  gnat_truthvalue_conversion (TREE_OPERAND (expr, 2))));
 103
 104     default:
 105       return build_binary_op (NE_EXPR, type, expr,
 106                               convert (type, integer_zero_node));
 107     }
 108 }
 109 \f
 110 /* Return the base type of TYPE.  */
 111
 112 tree
 113 get_base_type (tree type)
 114 {
 115   if (TREE_CODE (type) == RECORD_TYPE
 116       && TYPE_JUSTIFIED_MODULAR_P (type))
 117     type = TREE_TYPE (TYPE_FIELDS (type));
 118
 119   while (TREE_TYPE (type)
 120          && (TREE_CODE (type) == INTEGER_TYPE
 121              || TREE_CODE (type) == REAL_TYPE))
 122     type = TREE_TYPE (type);
 123
 124   return type;
 125 }
 126
 127 /* Likewise, but only return types known to the Ada source.  */
 128 tree
 129 get_ada_base_type (tree type)
 130 {
 131   while (TREE_TYPE (type)
 132          && (TREE_CODE (type) == INTEGER_TYPE
 133              || TREE_CODE (type) == REAL_TYPE)
 134          && !TYPE_EXTRA_SUBTYPE_P (type))
 135     type = TREE_TYPE (type);
 136
 137   return type;
 138 }
 139 \f
 140 /* EXP is a GCC tree representing an address.  See if we can find how
 141    strictly the object at that address is aligned.   Return that alignment
 142    in bits.  If we don't know anything about the alignment, return 0.  */
 143
 144 unsigned int
 145 known_alignment (tree exp)
 146 {
 147   unsigned int this_alignment;
 148   unsigned int lhs, rhs;
 149   unsigned int type_alignment;
 150
 151   /* For pointer expressions, we know that the designated object is always at
 152      least as strictly aligned as the designated subtype, so we account for
 153      both type and expression information in this case.
 154
 155      Beware that we can still get a dummy designated subtype here (e.g. Taft
 156      Amendement types), in which the alignment information is meaningless and
 157      should be ignored.
 158
 159      We always compute a type_alignment value and return the MAX of it
 160      compared with what we get from the expression tree. Just set the
 161      type_alignment value to 0 when the type information is to be ignored.  */
 162   type_alignment
 163     = ((POINTER_TYPE_P (TREE_TYPE (exp))
 164         && !TYPE_IS_DUMMY_P (TREE_TYPE (TREE_TYPE (exp))))
 165        ? TYPE_ALIGN (TREE_TYPE (TREE_TYPE (exp))) : 0);
 166
 167   switch (TREE_CODE (exp))
 168     {
 169     case CONVERT_EXPR:
 170     case NOP_EXPR:
 171     case NON_LVALUE_EXPR:
 172       /* Conversions between pointers and integers don't change the alignment
 173          of the underlying object.  */
 174       this_alignment = known_alignment (TREE_OPERAND (exp, 0));
 175       break;
 176
 177     case PLUS_EXPR:
 178     case MINUS_EXPR:
 179       /* If two address are added, the alignment of the result is the
 180          minimum of the two alignments.  */
 181       lhs = known_alignment (TREE_OPERAND (exp, 0));
 182       rhs = known_alignment (TREE_OPERAND (exp, 1));
 183       this_alignment = MIN (lhs, rhs);
 184       break;
 185
 186     case INTEGER_CST:
 187       /* The first part of this represents the lowest bit in the constant,
 188          but is it in bytes, not bits.  */
 189       this_alignment
 190         = MIN (BITS_PER_UNIT
 191                   * (TREE_INT_CST_LOW (exp) & - TREE_INT_CST_LOW (exp)),
 192                   BIGGEST_ALIGNMENT);
 193       break;
 194
 195     case MULT_EXPR:
 196       /* If we know the alignment of just one side, use it.  Otherwise,
 197          use the product of the alignments.  */
 198       lhs = known_alignment (TREE_OPERAND (exp, 0));
 199       rhs = known_alignment (TREE_OPERAND (exp, 1));
 200
 201       if (lhs == 0 || rhs == 0)
 202         this_alignment = MIN (BIGGEST_ALIGNMENT, MAX (lhs, rhs));
 203       else
 204         this_alignment = MIN (BIGGEST_ALIGNMENT, lhs * rhs);
 205       break;
 206
 207     case ADDR_EXPR:
 208       this_alignment = expr_align (TREE_OPERAND (exp, 0));
 209       break;
 210
 211     default:
 212       this_alignment = 0;
 213       break;
 214     }
 215
 216   return MAX (type_alignment, this_alignment);
 217 }
 218 \f
 219 /* We have a comparison or assignment operation on two types, T1 and T2,
 220    which are both either array types or both record types.
 221    Return the type that both operands should be converted to, if any.
 222    Otherwise return zero.  */
 223
 224 static tree
 225 find_common_type (tree t1, tree t2)
 226 {
 227   /* If either type is non-BLKmode, use it.  Note that we know that we will
 228      not have any alignment problems since if we did the non-BLKmode
 229      type could not have been used.  */
 230   if (TYPE_MODE (t1) != BLKmode)
 231     return t1;
 232   else if (TYPE_MODE (t2) != BLKmode)
 233     return t2;
 234
 235   /* If both types have constant size, use the smaller one.  */
 236   if (TREE_CONSTANT (TYPE_SIZE (t1)) && TREE_CONSTANT (TYPE_SIZE (t2)))
 237     return tree_int_cst_lt (TYPE_SIZE (t1), TYPE_SIZE (t2)) ? t1 : t2;
 238
 239   /* Otherwise, if either type has a constant size, use it.  */
 240   else if (TREE_CONSTANT (TYPE_SIZE (t1)))
 241     return t1;
 242   else if (TREE_CONSTANT (TYPE_SIZE (t2)))
 243     return t2;
 244
 245   /* In this case, both types have variable size.  It's probably
 246      best to leave the "type mismatch" because changing it could
 247      case a bad self-referential reference.  */
 248   return 0;
 249 }
 250 \f
 251 /* See if EXP contains a SAVE_EXPR in a position where we would
 252    normally put it.
 253
 254    ??? This is a real kludge, but is probably the best approach short
 255    of some very general solution.  */
 256
 257 static bool
 258 contains_save_expr_p (tree exp)
 259 {
 260   switch (TREE_CODE (exp))
 261     {
 262     case SAVE_EXPR:
 263       return true;
 264
 265     case ADDR_EXPR:  case INDIRECT_REF:
 266     case COMPONENT_REF:
 267     case NOP_EXPR:  case CONVERT_EXPR: case VIEW_CONVERT_EXPR:
 268       return contains_save_expr_p (TREE_OPERAND (exp, 0));
 269
 270     case CONSTRUCTOR:
 271       {
 272         tree value;
 273         unsigned HOST_WIDE_INT ix;
 274
 275         FOR_EACH_CONSTRUCTOR_VALUE (CONSTRUCTOR_ELTS (exp), ix, value)
 276           if (contains_save_expr_p (value))
 277             return true;
 278         return false;
 279       }
 280
 281     default:
 282       return false;
 283     }
 284 }
 285 \f
 286 /* See if EXP contains a NULL_EXPR in an expression we use for sizes. Return
 287    it if so.  This is used to detect types whose sizes involve computations
 288    that are known to raise Constraint_Error.  */
 289
 290 static tree
 291 contains_null_expr (tree exp)
 292 {
 293   tree tem;
 294
 295   if (TREE_CODE (exp) == NULL_EXPR)
 296     return exp;
 297
 298   switch (TREE_CODE_CLASS (TREE_CODE (exp)))
 299     {
 300     case tcc_unary:
 301       return contains_null_expr (TREE_OPERAND (exp, 0));
 302
 303     case tcc_comparison:
 304     case tcc_binary:
 305       tem = contains_null_expr (TREE_OPERAND (exp, 0));
 306       if (tem)
 307         return tem;
 308
 309       return contains_null_expr (TREE_OPERAND (exp, 1));
 310
 311     case tcc_expression:
 312       switch (TREE_CODE (exp))
 313         {
 314         case SAVE_EXPR:
 315           return contains_null_expr (TREE_OPERAND (exp, 0));
 316
 317         case COND_EXPR:
 318           tem = contains_null_expr (TREE_OPERAND (exp, 0));
 319           if (tem)
 320             return tem;
 321
 322           tem = contains_null_expr (TREE_OPERAND (exp, 1));
 323           if (tem)
 324             return tem;
 325
 326           return contains_null_expr (TREE_OPERAND (exp, 2));
 327
 328         default:
 329           return 0;
 330         }
 331
 332     default:
 333       return 0;
 334     }
 335 }
 336 \f
 337 /* Return an expression tree representing an equality comparison of
 338    A1 and A2, two objects of ARRAY_TYPE.  The returned expression should
 339    be of type RESULT_TYPE
 340
 341    Two arrays are equal in one of two ways: (1) if both have zero length
 342    in some dimension (not necessarily the same dimension) or (2) if the
 343    lengths in each dimension are equal and the data is equal.  We perform the
 344    length tests in as efficient a manner as possible.  */
 345
 346 static tree
 347 compare_arrays (tree result_type, tree a1, tree a2)
 348 {
 349   tree t1 = TREE_TYPE (a1);
 350   tree t2 = TREE_TYPE (a2);
 351   tree result = convert (result_type, integer_one_node);
 352   tree a1_is_null = convert (result_type, integer_zero_node);
 353   tree a2_is_null = convert (result_type, integer_zero_node);
 354   bool length_zero_p = false;
 355
 356   /* Process each dimension separately and compare the lengths.  If any
 357      dimension has a size known to be zero, set SIZE_ZERO_P to 1 to
 358      suppress the comparison of the data.  */
 359   while (TREE_CODE (t1) == ARRAY_TYPE && TREE_CODE (t2) == ARRAY_TYPE)
 360     {
 361       tree lb1 = TYPE_MIN_VALUE (TYPE_DOMAIN (t1));
 362       tree ub1 = TYPE_MAX_VALUE (TYPE_DOMAIN (t1));
 363       tree lb2 = TYPE_MIN_VALUE (TYPE_DOMAIN (t2));
 364       tree ub2 = TYPE_MAX_VALUE (TYPE_DOMAIN (t2));
 365       tree bt = get_base_type (TREE_TYPE (lb1));
 366       tree length1 = fold (build2 (MINUS_EXPR, bt, ub1, lb1));
 367       tree length2 = fold (build2 (MINUS_EXPR, bt, ub2, lb2));
 368       tree nbt;
 369       tree tem;
 370       tree comparison, this_a1_is_null, this_a2_is_null;
 371
 372       /* If the length of the first array is a constant, swap our operands
 373          unless the length of the second array is the constant zero.
 374          Note that we have set the `length' values to the length - 1.  */
 375       if (TREE_CODE (length1) == INTEGER_CST
 376           && !integer_zerop (fold (build2 (PLUS_EXPR, bt, length2,
 377                                            convert (bt, integer_one_node)))))
 378         {
 379           tem = a1, a1 = a2, a2 = tem;
 380           tem = t1, t1 = t2, t2 = tem;
 381           tem = lb1, lb1 = lb2, lb2 = tem;
 382           tem = ub1, ub1 = ub2, ub2 = tem;
 383           tem = length1, length1 = length2, length2 = tem;
 384           tem = a1_is_null, a1_is_null = a2_is_null, a2_is_null = tem;
 385         }
 386
 387       /* If the length of this dimension in the second array is the constant
 388          zero, we can just go inside the original bounds for the first
 389          array and see if last < first.  */
 390       if (integer_zerop (fold (build2 (PLUS_EXPR, bt, length2,
 391                                        convert (bt, integer_one_node)))))
 392         {
 393           tree ub = TYPE_MAX_VALUE (TYPE_INDEX_TYPE (TYPE_DOMAIN (t1)));
 394           tree lb = TYPE_MIN_VALUE (TYPE_INDEX_TYPE (TYPE_DOMAIN (t1)));
 395
 396           comparison = build_binary_op (LT_EXPR, result_type, ub, lb);
 397           comparison = SUBSTITUTE_PLACEHOLDER_IN_EXPR (comparison, a1);
 398           length1 = SUBSTITUTE_PLACEHOLDER_IN_EXPR (length1, a1);
 399
 400           length_zero_p = true;
 401           this_a1_is_null = comparison;
 402           this_a2_is_null = convert (result_type, integer_one_node);
 403         }
 404
 405       /* If the length is some other constant value, we know that the
 406          this dimension in the first array cannot be superflat, so we
 407          can just use its length from the actual stored bounds.  */
 408       else if (TREE_CODE (length2) == INTEGER_CST)
 409         {
 410           ub1 = TYPE_MAX_VALUE (TYPE_INDEX_TYPE (TYPE_DOMAIN (t1)));
 411           lb1 = TYPE_MIN_VALUE (TYPE_INDEX_TYPE (TYPE_DOMAIN (t1)));
 412           ub2 = TYPE_MAX_VALUE (TYPE_INDEX_TYPE (TYPE_DOMAIN (t2)));
 413           lb2 = TYPE_MIN_VALUE (TYPE_INDEX_TYPE (TYPE_DOMAIN (t2)));
 414           nbt = get_base_type (TREE_TYPE (ub1));
 415
 416           comparison
 417             = build_binary_op (EQ_EXPR, result_type,
 418                                build_binary_op (MINUS_EXPR, nbt, ub1, lb1),
 419                                build_binary_op (MINUS_EXPR, nbt, ub2, lb2));
 420
 421           /* Note that we know that UB2 and LB2 are constant and hence
 422              cannot contain a PLACEHOLDER_EXPR.  */
 423
 424           comparison = SUBSTITUTE_PLACEHOLDER_IN_EXPR (comparison, a1);
 425           length1 = SUBSTITUTE_PLACEHOLDER_IN_EXPR (length1, a1);
 426
 427           this_a1_is_null = build_binary_op (LT_EXPR, result_type, ub1, lb1);
 428           this_a2_is_null = convert (result_type, integer_zero_node);
 429         }
 430
 431       /* Otherwise compare the computed lengths.  */
 432       else
 433         {
 434           length1 = SUBSTITUTE_PLACEHOLDER_IN_EXPR (length1, a1);
 435           length2 = SUBSTITUTE_PLACEHOLDER_IN_EXPR (length2, a2);
 436
 437           comparison
 438             = build_binary_op (EQ_EXPR, result_type, length1, length2);
 439
 440           this_a1_is_null
 441             = build_binary_op (LT_EXPR, result_type, length1,
 442                                convert (bt, integer_zero_node));
 443           this_a2_is_null
 444             = build_binary_op (LT_EXPR, result_type, length2,
 445                                convert (bt, integer_zero_node));
 446         }
 447
 448       result = build_binary_op (TRUTH_ANDIF_EXPR, result_type,
 449                                 result, comparison);
 450
 451       a1_is_null = build_binary_op (TRUTH_ORIF_EXPR, result_type,
 452                                     this_a1_is_null, a1_is_null);
 453       a2_is_null = build_binary_op (TRUTH_ORIF_EXPR, result_type,
 454                                     this_a2_is_null, a2_is_null);
 455
 456       t1 = TREE_TYPE (t1);
 457       t2 = TREE_TYPE (t2);
 458     }
 459
 460   /* Unless the size of some bound is known to be zero, compare the
 461      data in the array.  */
 462   if (!length_zero_p)
 463     {
 464       tree type = find_common_type (TREE_TYPE (a1), TREE_TYPE (a2));
 465
 466       if (type)
 467         a1 = convert (type, a1), a2 = convert (type, a2);
 468
 469       result = build_binary_op (TRUTH_ANDIF_EXPR, result_type, result,
 470                                 fold (build2 (EQ_EXPR, result_type, a1, a2)));
 471
 472     }
 473
 474   /* The result is also true if both sizes are zero.  */
 475   result = build_binary_op (TRUTH_ORIF_EXPR, result_type,
 476                             build_binary_op (TRUTH_ANDIF_EXPR, result_type,
 477                                              a1_is_null, a2_is_null),
 478                             result);
 479
 480   /* If either operand contains SAVE_EXPRs, they have to be evaluated before
 481      starting the comparison above since the place it would be otherwise
 482      evaluated would be wrong.  */
 483
 484   if (contains_save_expr_p (a1))
 485     result = build2 (COMPOUND_EXPR, result_type, a1, result);
 486
 487   if (contains_save_expr_p (a2))
 488     result = build2 (COMPOUND_EXPR, result_type, a2, result);
 489
 490   return result;
 491 }
 492 \f
 493 /* Compute the result of applying OP_CODE to LHS and RHS, where both are of
 494    type TYPE.  We know that TYPE is a modular type with a nonbinary
 495    modulus.  */
 496
 497 static tree
 498 nonbinary_modular_operation (enum tree_code op_code, tree type, tree lhs,
 499                              tree rhs)
 500 {
 501   tree modulus = TYPE_MODULUS (type);
 502   unsigned int needed_precision = tree_floor_log2 (modulus) + 1;
 503   unsigned int precision;
 504   bool unsignedp = true;
 505   tree op_type = type;
 506   tree result;
 507
 508   /* If this is an addition of a constant, convert it to a subtraction
 509      of a constant since we can do that faster.  */
 510   if (op_code == PLUS_EXPR && TREE_CODE (rhs) == INTEGER_CST)
 511     rhs = fold (build2 (MINUS_EXPR, type, modulus, rhs)), op_code = MINUS_EXPR;
 512
 513   /* For the logical operations, we only need PRECISION bits.  For
 514      addition and subtraction, we need one more and for multiplication we
 515      need twice as many.  But we never want to make a size smaller than
 516      our size. */
 517   if (op_code == PLUS_EXPR || op_code == MINUS_EXPR)
 518     needed_precision += 1;
 519   else if (op_code == MULT_EXPR)
 520     needed_precision *= 2;
 521
 522   precision = MAX (needed_precision, TYPE_PRECISION (op_type));
 523
 524   /* Unsigned will do for everything but subtraction.  */
 525   if (op_code == MINUS_EXPR)
 526     unsignedp = false;
 527
 528   /* If our type is the wrong signedness or isn't wide enough, make a new
 529      type and convert both our operands to it.  */
 530   if (TYPE_PRECISION (op_type) < precision
 531       || TYPE_UNSIGNED (op_type) != unsignedp)
 532     {
 533       /* Copy the node so we ensure it can be modified to make it modular.  */
 534       op_type = copy_node (gnat_type_for_size (precision, unsignedp));
 535       modulus = convert (op_type, modulus);
 536       SET_TYPE_MODULUS (op_type, modulus);
 537       TYPE_MODULAR_P (op_type) = 1;
 538       lhs = convert (op_type, lhs);
 539       rhs = convert (op_type, rhs);
 540     }
 541
 542   /* Do the operation, then we'll fix it up.  */
 543   result = fold (build2 (op_code, op_type, lhs, rhs));
 544
 545   /* For multiplication, we have no choice but to do a full modulus
 546      operation.  However, we want to do this in the narrowest
 547      possible size.  */
 548   if (op_code == MULT_EXPR)
 549     {
 550       tree div_type = copy_node (gnat_type_for_size (needed_precision, 1));
 551       modulus = convert (div_type, modulus);
 552       SET_TYPE_MODULUS (div_type, modulus);
 553       TYPE_MODULAR_P (div_type) = 1;
 554       result = convert (op_type,
 555                         fold (build2 (TRUNC_MOD_EXPR, div_type,
 556                                       convert (div_type, result), modulus)));
 557     }
 558
 559   /* For subtraction, add the modulus back if we are negative.  */
 560   else if (op_code == MINUS_EXPR)
 561     {
 562       result = save_expr (result);
 563       result = fold (build3 (COND_EXPR, op_type,
 564                              build2 (LT_EXPR, integer_type_node, result,
 565                                      convert (op_type, integer_zero_node)),
 566                              fold (build2 (PLUS_EXPR, op_type,
 567                                            result, modulus)),
 568                              result));
 569     }
 570
 571   /* For the other operations, subtract the modulus if we are >= it.  */
 572   else
 573     {
 574       result = save_expr (result);
 575       result = fold (build3 (COND_EXPR, op_type,
 576                              build2 (GE_EXPR, integer_type_node,
 577                                      result, modulus),
 578                              fold (build2 (MINUS_EXPR, op_type,
 579                                            result, modulus)),
 580                              result));
 581     }
 582
 583   return convert (type, result);
 584 }
 585 \f
 586 /* Make a binary operation of kind OP_CODE.  RESULT_TYPE is the type
 587    desired for the result.  Usually the operation is to be performed
 588    in that type.  For MODIFY_EXPR and ARRAY_REF, RESULT_TYPE may be 0
 589    in which case the type to be used will be derived from the operands.
 590
 591    This function is very much unlike the ones for C and C++ since we
 592    have already done any type conversion and matching required.  All we
 593    have to do here is validate the work done by SEM and handle subtypes.  */
 594
 595 tree
 596 build_binary_op (enum tree_code op_code, tree result_type,
 597                  tree left_operand, tree right_operand)
 598 {
 599   tree left_type  = TREE_TYPE (left_operand);
 600   tree right_type = TREE_TYPE (right_operand);
 601   tree left_base_type = get_base_type (left_type);
 602   tree right_base_type = get_base_type (right_type);
 603   tree operation_type = result_type;
 604   tree best_type = NULL_TREE;
 605   tree modulus;
 606   tree result;
 607   bool has_side_effects = false;
 608
 609   if (operation_type
 610       && TREE_CODE (operation_type) == RECORD_TYPE
 611       && TYPE_JUSTIFIED_MODULAR_P (operation_type))
 612     operation_type = TREE_TYPE (TYPE_FIELDS (operation_type));
 613
 614   if (operation_type
 615       && !AGGREGATE_TYPE_P (operation_type)
 616       && TYPE_EXTRA_SUBTYPE_P (operation_type))
 617     operation_type = get_base_type (operation_type);
 618
 619   modulus = (operation_type && TREE_CODE (operation_type) == INTEGER_TYPE
 620              && TYPE_MODULAR_P (operation_type)
 621              ? TYPE_MODULUS (operation_type) : 0);
 622
 623   switch (op_code)
 624     {
 625     case MODIFY_EXPR:
 626       /* If there were any integral or pointer conversions on LHS, remove
 627          them; we'll be putting them back below if needed.  Likewise for
 628          conversions between array and record types.  But don't do this if
 629          the right operand is not BLKmode (for packed arrays)
 630          unless we are not changing the mode.  */
 631       while ((TREE_CODE (left_operand) == CONVERT_EXPR
 632               || TREE_CODE (left_operand) == NOP_EXPR
 633               || TREE_CODE (left_operand) == VIEW_CONVERT_EXPR)
 634              && (((INTEGRAL_TYPE_P (left_type)
 635                    || POINTER_TYPE_P (left_type))
 636                   && (INTEGRAL_TYPE_P (TREE_TYPE
 637                                        (TREE_OPERAND (left_operand, 0)))
 638                       || POINTER_TYPE_P (TREE_TYPE
 639                                          (TREE_OPERAND (left_operand, 0)))))
 640                  || (((TREE_CODE (left_type) == RECORD_TYPE
 641                        /* Don't remove conversions to justified modular
 642                           types. */
 643                        && !TYPE_JUSTIFIED_MODULAR_P (left_type))
 644                       || TREE_CODE (left_type) == ARRAY_TYPE)
 645                      && ((TREE_CODE (TREE_TYPE
 646                                      (TREE_OPERAND (left_operand, 0)))
 647                           == RECORD_TYPE)
 648                          || (TREE_CODE (TREE_TYPE
 649                                         (TREE_OPERAND (left_operand, 0)))
 650                              == ARRAY_TYPE))
 651                      && (TYPE_MODE (right_type) == BLKmode
 652                          || (TYPE_MODE (left_type)
 653                              == TYPE_MODE (TREE_TYPE
 654                                            (TREE_OPERAND
 655                                             (left_operand, 0))))))))
 656         {
 657           left_operand = TREE_OPERAND (left_operand, 0);
 658           left_type = TREE_TYPE (left_operand);
 659         }
 660
 661       if (!operation_type)
 662         operation_type = left_type;
 663
 664       /* If we are copying one array or record to another, find the best type
 665          to use.  */
 666       if (((TREE_CODE (left_type) == ARRAY_TYPE
 667             && TREE_CODE (right_type) == ARRAY_TYPE)
 668            || (TREE_CODE (left_type) == RECORD_TYPE
 669                && TREE_CODE (right_type) == RECORD_TYPE))
 670           && (best_type = find_common_type (left_type, right_type)))
 671         operation_type = best_type;
 672
 673       /* If a class-wide type may be involved, force use of the RHS type.  */
 674       if ((TREE_CODE (right_type) == RECORD_TYPE
 675            || TREE_CODE (right_type) == UNION_TYPE)
 676           && TYPE_ALIGN_OK (right_type))
 677         operation_type = right_type;
 678
 679       /* Ensure everything on the LHS is valid.  If we have a field reference,
 680          strip anything that get_inner_reference can handle.  Then remove any
 681          conversions with type types having the same code and mode.  Mark
 682          VIEW_CONVERT_EXPRs with TREE_ADDRESSABLE.  When done, we must have
 683          either an INDIRECT_REF or a decl.  */
 684       result = left_operand;
 685       while (1)
 686         {
 687           tree restype = TREE_TYPE (result);
 688
 689           if (TREE_CODE (result) == COMPONENT_REF
 690               || TREE_CODE (result) == ARRAY_REF
 691               || TREE_CODE (result) == ARRAY_RANGE_REF)
 692             while (handled_component_p (result))
 693               result = TREE_OPERAND (result, 0);
 694           else if (TREE_CODE (result) == REALPART_EXPR
 695                    || TREE_CODE (result) == IMAGPART_EXPR
 696                    || ((TREE_CODE (result) == NOP_EXPR
 697                         || TREE_CODE (result) == CONVERT_EXPR)
 698                        && (((TREE_CODE (restype)
 699                              == TREE_CODE (TREE_TYPE
 700                                            (TREE_OPERAND (result, 0))))
 701                              && (TYPE_MODE (TREE_TYPE
 702                                             (TREE_OPERAND (result, 0)))
 703                                  == TYPE_MODE (restype)))
 704                            || TYPE_ALIGN_OK (restype))))
 705             result = TREE_OPERAND (result, 0);
 706           else if (TREE_CODE (result) == VIEW_CONVERT_EXPR)
 707             {
 708               TREE_ADDRESSABLE (result) = 1;
 709               result = TREE_OPERAND (result, 0);
 710             }
 711           else
 712             break;
 713         }
 714
 715       gcc_assert (TREE_CODE (result) == INDIRECT_REF
 716                   || TREE_CODE (result) == NULL_EXPR || DECL_P (result));
 717
 718       /* Convert the right operand to the operation type unless
 719          it is either already of the correct type or if the type
 720          involves a placeholder, since the RHS may not have the same
 721          record type.  */
 722       if (operation_type != right_type
 723           && (!CONTAINS_PLACEHOLDER_P (TYPE_SIZE (operation_type))))
 724         {
 725           right_operand = convert (operation_type, right_operand);
 726           right_type = operation_type;
 727         }
 728
 729       /* If the left operand is not the same type as the operation type,
 730          surround it in a VIEW_CONVERT_EXPR.  */
 731       if (left_type != operation_type)
 732         left_operand = unchecked_convert (operation_type, left_operand, false);
 733
 734       has_side_effects = true;
 735       modulus = NULL_TREE;
 736       break;
 737
 738     case ARRAY_REF:
 739       if (!operation_type)
 740         operation_type = TREE_TYPE (left_type);
 741
 742       /* ... fall through ... */
 743
 744     case ARRAY_RANGE_REF:
 745
 746       /* First convert the right operand to its base type.  This will
 747          prevent unneeded signedness conversions when sizetype is wider than
 748          integer.  */
 749       right_operand = convert (right_base_type, right_operand);
 750       right_operand = convert (TYPE_DOMAIN (left_type), right_operand);
 751
 752       if (!TREE_CONSTANT (right_operand)
 753           || !TREE_CONSTANT (TYPE_MIN_VALUE (right_type)))
 754         gnat_mark_addressable (left_operand);
 755
 756       modulus = NULL_TREE;
 757       break;
 758
 759     case GE_EXPR:
 760     case LE_EXPR:
 761     case GT_EXPR:
 762     case LT_EXPR:
 763       gcc_assert (!POINTER_TYPE_P (left_type));
 764
 765       /* ... fall through ... */
 766
 767     case EQ_EXPR:
 768     case NE_EXPR:
 769       /* If either operand is a NULL_EXPR, just return a new one.  */
 770       if (TREE_CODE (left_operand) == NULL_EXPR)
 771         return build2 (op_code, result_type,
 772                        build1 (NULL_EXPR, integer_type_node,
 773                                TREE_OPERAND (left_operand, 0)),
 774                        integer_zero_node);
 775
 776       else if (TREE_CODE (right_operand) == NULL_EXPR)
 777         return build2 (op_code, result_type,
 778                        build1 (NULL_EXPR, integer_type_node,
 779                                TREE_OPERAND (right_operand, 0)),
 780                        integer_zero_node);
 781
 782       /* If either object is a justified modular types, get the
 783          fields from within.  */
 784       if (TREE_CODE (left_type) == RECORD_TYPE
 785           && TYPE_JUSTIFIED_MODULAR_P (left_type))
 786         {
 787           left_operand = convert (TREE_TYPE (TYPE_FIELDS (left_type)),
 788                                   left_operand);
 789           left_type = TREE_TYPE (left_operand);
 790           left_base_type = get_base_type (left_type);
 791         }
 792
 793       if (TREE_CODE (right_type) == RECORD_TYPE
 794           && TYPE_JUSTIFIED_MODULAR_P (right_type))
 795         {
 796           right_operand = convert (TREE_TYPE (TYPE_FIELDS (right_type)),
 797                                   right_operand);
 798           right_type = TREE_TYPE (right_operand);
 799           right_base_type = get_base_type (right_type);
 800         }
 801
 802       /* If both objects are arrays, compare them specially.  */
 803       if ((TREE_CODE (left_type) == ARRAY_TYPE
 804            || (TREE_CODE (left_type) == INTEGER_TYPE
 805                && TYPE_HAS_ACTUAL_BOUNDS_P (left_type)))
 806           && (TREE_CODE (right_type) == ARRAY_TYPE
 807               || (TREE_CODE (right_type) == INTEGER_TYPE
 808                   && TYPE_HAS_ACTUAL_BOUNDS_P (right_type))))
 809         {
 810           result = compare_arrays (result_type, left_operand, right_operand);
 811
 812           if (op_code == NE_EXPR)
 813             result = invert_truthvalue (result);
 814           else
 815             gcc_assert (op_code == EQ_EXPR);
 816
 817           return result;
 818         }
 819
 820       /* Otherwise, the base types must be the same unless the objects are
 821          records.  If we have records, use the best type and convert both
 822          operands to that type.  */
 823       if (left_base_type != right_base_type)
 824         {
 825           if (TREE_CODE (left_base_type) == RECORD_TYPE
 826               && TREE_CODE (right_base_type) == RECORD_TYPE)
 827             {
 828               /* The only way these are permitted to be the same is if both
 829                  types have the same name.  In that case, one of them must
 830                  not be self-referential.  Use that one as the best type.
 831                  Even better is if one is of fixed size.  */
 832               best_type = NULL_TREE;
 833
 834               gcc_assert (TYPE_NAME (left_base_type)
 835                           && (TYPE_NAME (left_base_type)
 836                               == TYPE_NAME (right_base_type)));
 837
 838               if (TREE_CONSTANT (TYPE_SIZE (left_base_type)))
 839                 best_type = left_base_type;
 840               else if (TREE_CONSTANT (TYPE_SIZE (right_base_type)))
 841                 best_type = right_base_type;
 842               else if (!CONTAINS_PLACEHOLDER_P (TYPE_SIZE (left_base_type)))
 843                 best_type = left_base_type;
 844               else if (!CONTAINS_PLACEHOLDER_P (TYPE_SIZE (right_base_type)))
 845                 best_type = right_base_type;
 846               else
 847                 gcc_unreachable ();
 848
 849               left_operand = convert (best_type, left_operand);
 850               right_operand = convert (best_type, right_operand);
 851             }
 852           else
 853             gcc_unreachable ();
 854         }
 855
 856       /* If we are comparing a fat pointer against zero, we need to
 857          just compare the data pointer.  */
 858       else if (TYPE_FAT_POINTER_P (left_base_type)
 859                && TREE_CODE (right_operand) == CONSTRUCTOR
 860                && integer_zerop (VEC_index (constructor_elt,
 861                                             CONSTRUCTOR_ELTS (right_operand),
 862                                             0)
 863                                  ->value))
 864         {
 865           right_operand = build_component_ref (left_operand, NULL_TREE,
 866                                                TYPE_FIELDS (left_base_type),
 867                                                false);
 868           left_operand = convert (TREE_TYPE (right_operand),
 869                                   integer_zero_node);
 870         }
 871       else
 872         {
 873           left_operand = convert (left_base_type, left_operand);
 874           right_operand = convert (right_base_type, right_operand);
 875         }
 876
 877       modulus = NULL_TREE;
 878       break;
 879
 880     case PREINCREMENT_EXPR:
 881     case PREDECREMENT_EXPR:
 882     case POSTINCREMENT_EXPR:
 883     case POSTDECREMENT_EXPR:
 884       /* In these, the result type and the left operand type should be the
 885          same.  Do the operation in the base type of those and convert the
 886          right operand (which is an integer) to that type.
 887
 888          Note that these operations are only used in loop control where
 889          we guarantee that no overflow can occur.  So nothing special need
 890          be done for modular types.  */
 891
 892       gcc_assert (left_type == result_type);
 893       operation_type = get_base_type (result_type);
 894       left_operand = convert (operation_type, left_operand);
 895       right_operand = convert (operation_type, right_operand);
 896       has_side_effects = true;
 897       modulus = NULL_TREE;
 898       break;
 899
 900     case LSHIFT_EXPR:
 901     case RSHIFT_EXPR:
 902     case LROTATE_EXPR:
 903     case RROTATE_EXPR:
 904        /* The RHS of a shift can be any type.  Also, ignore any modulus
 905          (we used to abort, but this is needed for unchecked conversion
 906          to modular types).  Otherwise, processing is the same as normal.  */
 907       gcc_assert (operation_type == left_base_type);
 908       modulus = NULL_TREE;
 909       left_operand = convert (operation_type, left_operand);
 910       break;
 911
 912     case TRUTH_ANDIF_EXPR:
 913     case TRUTH_ORIF_EXPR:
 914     case TRUTH_AND_EXPR:
 915     case TRUTH_OR_EXPR:
 916     case TRUTH_XOR_EXPR:
 917       left_operand = gnat_truthvalue_conversion (left_operand);
 918       right_operand = gnat_truthvalue_conversion (right_operand);
 919       goto common;
 920
 921     case BIT_AND_EXPR:
 922     case BIT_IOR_EXPR:
 923     case BIT_XOR_EXPR:
 924       /* For binary modulus, if the inputs are in range, so are the
 925          outputs.  */
 926       if (modulus && integer_pow2p (modulus))
 927         modulus = NULL_TREE;
 928
 929       goto common;
 930
 931     case COMPLEX_EXPR:
 932       gcc_assert (TREE_TYPE (result_type) == left_base_type
 933                   && TREE_TYPE (result_type) == right_base_type);
 934       left_operand = convert (left_base_type, left_operand);
 935       right_operand = convert (right_base_type, right_operand);
 936       break;
 937
 938     case TRUNC_DIV_EXPR:   case TRUNC_MOD_EXPR:
 939     case CEIL_DIV_EXPR:    case CEIL_MOD_EXPR:
 940     case FLOOR_DIV_EXPR:   case FLOOR_MOD_EXPR:
 941     case ROUND_DIV_EXPR:   case ROUND_MOD_EXPR:
 942       /* These always produce results lower than either operand.  */
 943       modulus = NULL_TREE;
 944       goto common;
 945
 946     default:
 947     common:
 948       /* The result type should be the same as the base types of the
 949          both operands (and they should be the same).  Convert
 950          everything to the result type.  */
 951
 952       gcc_assert (operation_type == left_base_type
 953                   && left_base_type == right_base_type);
 954       left_operand = convert (operation_type, left_operand);
 955       right_operand = convert (operation_type, right_operand);
 956     }
 957
 958   if (modulus && !integer_pow2p (modulus))
 959     {
 960       result = nonbinary_modular_operation (op_code, operation_type,
 961                                             left_operand, right_operand);
 962       modulus = NULL_TREE;
 963     }
 964   /* If either operand is a NULL_EXPR, just return a new one.  */
 965   else if (TREE_CODE (left_operand) == NULL_EXPR)
 966     return build1 (NULL_EXPR, operation_type, TREE_OPERAND (left_operand, 0));
 967   else if (TREE_CODE (right_operand) == NULL_EXPR)
 968     return build1 (NULL_EXPR, operation_type, TREE_OPERAND (right_operand, 0));
 969   else if (op_code == ARRAY_REF || op_code == ARRAY_RANGE_REF)
 970     result = fold (build4 (op_code, operation_type, left_operand,
 971                            right_operand, NULL_TREE, NULL_TREE));
 972   else
 973     result
 974       = fold (build2 (op_code, operation_type, left_operand, right_operand));
 975
 976   TREE_SIDE_EFFECTS (result) |= has_side_effects;
 977   TREE_CONSTANT (result)
 978     |= (TREE_CONSTANT (left_operand) & TREE_CONSTANT (right_operand)
 979         && op_code != ARRAY_REF && op_code != ARRAY_RANGE_REF);
 980
 981   if ((op_code == ARRAY_REF || op_code == ARRAY_RANGE_REF)
 982       && TYPE_VOLATILE (operation_type))
 983     TREE_THIS_VOLATILE (result) = 1;
 984
 985   /* If we are working with modular types, perform the MOD operation
 986      if something above hasn't eliminated the need for it.  */
 987   if (modulus)
 988     result = fold (build2 (FLOOR_MOD_EXPR, operation_type, result,
 989                            convert (operation_type, modulus)));
 990
 991   if (result_type && result_type != operation_type)
 992     result = convert (result_type, result);
 993
 994   return result;
 995 }
 996 \f
 997 /* Similar, but for unary operations.  */
 998
 999 tree
1000 build_unary_op (enum tree_code op_code, tree result_type, tree operand)
1001 {
1002   tree type = TREE_TYPE (operand);
1003   tree base_type = get_base_type (type);
1004   tree operation_type = result_type;
1005   tree result;
1006   bool side_effects = false;
1007
1008   if (operation_type
1009       && TREE_CODE (operation_type) == RECORD_TYPE
1010       && TYPE_JUSTIFIED_MODULAR_P (operation_type))
1011     operation_type = TREE_TYPE (TYPE_FIELDS (operation_type));
1012
1013   if (operation_type
1014       && !AGGREGATE_TYPE_P (operation_type)
1015       && TYPE_EXTRA_SUBTYPE_P (operation_type))
1016     operation_type = get_base_type (operation_type);
1017
1018   switch (op_code)
1019     {
1020     case REALPART_EXPR:
1021     case IMAGPART_EXPR:
1022       if (!operation_type)
1023         result_type = operation_type = TREE_TYPE (type);
1024       else
1025         gcc_assert (result_type == TREE_TYPE (type));
1026
1027       result = fold (build1 (op_code, operation_type, operand));
1028       break;
1029
1030     case TRUTH_NOT_EXPR:
1031       gcc_assert (result_type == base_type);
1032       result = invert_truthvalue (gnat_truthvalue_conversion (operand));
1033       break;
1034
1035     case ATTR_ADDR_EXPR:
1036     case ADDR_EXPR:
1037       switch (TREE_CODE (operand))
1038         {
1039         case INDIRECT_REF:
1040         case UNCONSTRAINED_ARRAY_REF:
1041           result = TREE_OPERAND (operand, 0);
1042
1043           /* Make sure the type here is a pointer, not a reference.
1044              GCC wants pointer types for function addresses.  */
1045           if (!result_type)
1046             result_type = build_pointer_type (type);
1047           break;
1048
1049         case NULL_EXPR:
1050           result = operand;
1051           TREE_TYPE (result) = type = build_pointer_type (type);
1052           break;
1053
1054         case ARRAY_REF:
1055         case ARRAY_RANGE_REF:
1056         case COMPONENT_REF:
1057         case BIT_FIELD_REF:
1058             /* If this is for 'Address, find the address of the prefix and
1059                add the offset to the field.  Otherwise, do this the normal
1060                way.  */
1061           if (op_code == ATTR_ADDR_EXPR)
1062             {
1063               HOST_WIDE_INT bitsize;
1064               HOST_WIDE_INT bitpos;
1065               tree offset, inner;
1066               enum machine_mode mode;
1067               int unsignedp, volatilep;
1068
1069               inner = get_inner_reference (operand, &bitsize, &bitpos, &offset,
1070                                            &mode, &unsignedp, &volatilep,
1071                                            false);
1072
1073               /* If INNER is a padding type whose field has a self-referential
1074                  size, convert to that inner type.  We know the offset is zero
1075                  and we need to have that type visible.  */
1076               if (TREE_CODE (TREE_TYPE (inner)) == RECORD_TYPE
1077                   && TYPE_IS_PADDING_P (TREE_TYPE (inner))
1078                   && (CONTAINS_PLACEHOLDER_P
1079                       (TYPE_SIZE (TREE_TYPE (TYPE_FIELDS
1080                                              (TREE_TYPE (inner)))))))
1081                 inner = convert (TREE_TYPE (TYPE_FIELDS (TREE_TYPE (inner))),
1082                                  inner);
1083
1084               /* Compute the offset as a byte offset from INNER.  */
1085               if (!offset)
1086                 offset = size_zero_node;
1087
1088               if (bitpos % BITS_PER_UNIT != 0)
1089                 post_error
1090                   ("taking address of object not aligned on storage unit?",
1091                    error_gnat_node);
1092
1093               offset = size_binop (PLUS_EXPR, offset,
1094                                    size_int (bitpos / BITS_PER_UNIT));
1095
1096               /* Take the address of INNER, convert the offset to void *, and
1097                  add then.  It will later be converted to the desired result
1098                  type, if any.  */
1099               inner = build_unary_op (ADDR_EXPR, NULL_TREE, inner);
1100               inner = convert (ptr_void_type_node, inner);
1101               offset = convert (ptr_void_type_node, offset);
1102               result = build_binary_op (PLUS_EXPR, ptr_void_type_node,
1103                                         inner, offset);
1104               result = convert (build_pointer_type (TREE_TYPE (operand)),
1105                                 result);
1106               break;
1107             }
1108           goto common;
1109
1110         case CONSTRUCTOR:
1111           /* If this is just a constructor for a padded record, we can
1112              just take the address of the single field and convert it to
1113              a pointer to our type.  */
1114           if (TREE_CODE (type) == RECORD_TYPE && TYPE_IS_PADDING_P (type))
1115             {
1116               result = (VEC_index (constructor_elt,
1117                                    CONSTRUCTOR_ELTS (operand),
1118                                    0)
1119                         ->value);
1120
1121               result = convert (build_pointer_type (TREE_TYPE (operand)),
1122                                 build_unary_op (ADDR_EXPR, NULL_TREE, result));
1123               break;
1124             }
1125
1126           goto common;
1127
1128         case NOP_EXPR:
1129           if (AGGREGATE_TYPE_P (type)
1130               && AGGREGATE_TYPE_P (TREE_TYPE (TREE_OPERAND (operand, 0))))
1131             return build_unary_op (ADDR_EXPR, result_type,
1132                                    TREE_OPERAND (operand, 0));
1133
1134           /* ... fallthru ... */
1135
1136         case VIEW_CONVERT_EXPR:
1137           /* If this just a variant conversion or if the conversion doesn't
1138              change the mode, get the result type from this type and go down.
1139              This is needed for conversions of CONST_DECLs, to eventually get
1140              to the address of their CORRESPONDING_VARs.  */
1141           if ((TYPE_MAIN_VARIANT (type)
1142                == TYPE_MAIN_VARIANT (TREE_TYPE (TREE_OPERAND (operand, 0))))
1143               || (TYPE_MODE (type) != BLKmode
1144                   && (TYPE_MODE (type)
1145                       == TYPE_MODE (TREE_TYPE (TREE_OPERAND (operand, 0))))))
1146             return build_unary_op (ADDR_EXPR,
1147                                    (result_type ? result_type
1148                                     : build_pointer_type (type)),
1149                                    TREE_OPERAND (operand, 0));
1150           goto common;
1151
1152         case CONST_DECL:
1153           operand = DECL_CONST_CORRESPONDING_VAR (operand);
1154
1155           /* ... fall through ... */
1156
1157         default:
1158         common:
1159
1160           /* If we are taking the address of a padded record whose field is
1161              contains a template, take the address of the template.  */
1162           if (TREE_CODE (type) == RECORD_TYPE
1163               && TYPE_IS_PADDING_P (type)
1164               && TREE_CODE (TREE_TYPE (TYPE_FIELDS (type))) == RECORD_TYPE
1165               && TYPE_CONTAINS_TEMPLATE_P (TREE_TYPE (TYPE_FIELDS (type))))
1166             {
1167               type = TREE_TYPE (TYPE_FIELDS (type));
1168               operand = convert (type, operand);
1169             }
1170
1171           if (type != error_mark_node)
1172             operation_type = build_pointer_type (type);
1173
1174           gnat_mark_addressable (operand);
1175           result = fold (build1 (ADDR_EXPR, operation_type, operand));
1176         }
1177
1178       TREE_CONSTANT (result) = staticp (operand) || TREE_CONSTANT (operand);
1179       break;
1180
1181     case INDIRECT_REF:
1182       /* If we want to refer to an entire unconstrained array,
1183          make up an expression to do so.  This will never survive to
1184          the backend.  If TYPE is a thin pointer, first convert the
1185          operand to a fat pointer.  */
1186       if (TYPE_THIN_POINTER_P (type)
1187           && TYPE_UNCONSTRAINED_ARRAY (TREE_TYPE (type)))
1188         {
1189           operand
1190             = convert (TREE_TYPE (TYPE_UNCONSTRAINED_ARRAY (TREE_TYPE (type))),
1191                        operand);
1192           type = TREE_TYPE (operand);
1193         }
1194
1195       if (TYPE_FAT_POINTER_P (type))
1196         {
1197           result = build1 (UNCONSTRAINED_ARRAY_REF,
1198                            TYPE_UNCONSTRAINED_ARRAY (type), operand);
1199           TREE_READONLY (result) = TREE_STATIC (result)
1200             = TYPE_READONLY (TYPE_UNCONSTRAINED_ARRAY (type));
1201         }
1202       else if (TREE_CODE (operand) == ADDR_EXPR)
1203         result = TREE_OPERAND (operand, 0);
1204
1205       else
1206         {
1207           result = fold (build1 (op_code, TREE_TYPE (type), operand));
1208           TREE_READONLY (result) = TYPE_READONLY (TREE_TYPE (type));
1209         }
1210
1211       side_effects
1212         =  (!TYPE_FAT_POINTER_P (type) && TYPE_VOLATILE (TREE_TYPE (type)));
1213       break;
1214
1215     case NEGATE_EXPR:
1216     case BIT_NOT_EXPR:
1217       {
1218         tree modulus = ((operation_type
1219                          && TREE_CODE (operation_type) == INTEGER_TYPE
1220                          && TYPE_MODULAR_P (operation_type))
1221                         ? TYPE_MODULUS (operation_type) : 0);
1222         int mod_pow2 = modulus && integer_pow2p (modulus);
1223
1224         /* If this is a modular type, there are various possibilities
1225            depending on the operation and whether the modulus is a
1226            power of two or not.  */
1227
1228         if (modulus)
1229           {
1230             gcc_assert (operation_type == base_type);
1231             operand = convert (operation_type, operand);
1232
1233             /* The fastest in the negate case for binary modulus is
1234                the straightforward code; the TRUNC_MOD_EXPR below
1235                is an AND operation.  */
1236             if (op_code == NEGATE_EXPR && mod_pow2)
1237               result = fold (build2 (TRUNC_MOD_EXPR, operation_type,
1238                                      fold (build1 (NEGATE_EXPR, operation_type,
1239                                                    operand)),
1240                                      modulus));
1241
1242             /* For nonbinary negate case, return zero for zero operand,
1243                else return the modulus minus the operand.  If the modulus
1244                is a power of two minus one, we can do the subtraction
1245                as an XOR since it is equivalent and faster on most machines. */
1246             else if (op_code == NEGATE_EXPR && !mod_pow2)
1247               {
1248                 if (integer_pow2p (fold (build2 (PLUS_EXPR, operation_type,
1249                                                  modulus,
1250                                                  convert (operation_type,
1251                                                           integer_one_node)))))
1252                   result = fold (build2 (BIT_XOR_EXPR, operation_type,
1253                                          operand, modulus));
1254                 else
1255                   result = fold (build2 (MINUS_EXPR, operation_type,
1256                                         modulus, operand));
1257
1258                 result = fold (build3 (COND_EXPR, operation_type,
1259                                        fold (build2 (NE_EXPR,
1260                                                      integer_type_node,
1261                                                      operand,
1262                                                      convert
1263                                                      (operation_type,
1264                                                       integer_zero_node))),
1265                                        result, operand));
1266               }
1267             else
1268               {
1269                 /* For the NOT cases, we need a constant equal to
1270                    the modulus minus one.  For a binary modulus, we
1271                    XOR against the constant and subtract the operand from
1272                    that constant for nonbinary modulus.  */
1273
1274                 tree cnst = fold (build2 (MINUS_EXPR, operation_type, modulus,
1275                                           convert (operation_type,
1276                                                    integer_one_node)));
1277
1278                 if (mod_pow2)
1279                   result = fold (build2 (BIT_XOR_EXPR, operation_type,
1280                                          operand, cnst));
1281                 else
1282                   result = fold (build2 (MINUS_EXPR, operation_type,
1283                                          cnst, operand));
1284               }
1285
1286             break;
1287           }
1288       }
1289
1290       /* ... fall through ... */
1291
1292     default:
1293       gcc_assert (operation_type == base_type);
1294       result = fold (build1 (op_code, operation_type, convert (operation_type,
1295                                                                operand)));
1296     }
1297
1298   if (side_effects)
1299     {
1300       TREE_SIDE_EFFECTS (result) = 1;
1301       if (TREE_CODE (result) == INDIRECT_REF)
1302         TREE_THIS_VOLATILE (result) = TYPE_VOLATILE (TREE_TYPE (result));
1303     }
1304
1305   if (result_type && TREE_TYPE (result) != result_type)
1306     result = convert (result_type, result);
1307
1308   return result;
1309 }
1310 \f
1311 /* Similar, but for COND_EXPR.  */
1312
1313 tree
1314 build_cond_expr (tree result_type, tree condition_operand,
1315                  tree true_operand, tree false_operand)
1316 {
1317   tree result;
1318   bool addr_p = false;
1319
1320   /* The front-end verifies that result, true and false operands have same base
1321      type.  Convert everything to the result type.  */
1322
1323   true_operand  = convert (result_type, true_operand);
1324   false_operand = convert (result_type, false_operand);
1325
1326   /* If the result type is unconstrained, take the address of
1327      the operands and then dereference our result.  */
1328   if (TREE_CODE (result_type) == UNCONSTRAINED_ARRAY_TYPE
1329       || CONTAINS_PLACEHOLDER_P (TYPE_SIZE (result_type)))
1330     {
1331       addr_p = true;
1332       result_type = build_pointer_type (result_type);
1333       true_operand = build_unary_op (ADDR_EXPR, result_type, true_operand);
1334       false_operand = build_unary_op (ADDR_EXPR, result_type, false_operand);
1335     }
1336
1337   result = fold (build3 (COND_EXPR, result_type, condition_operand,
1338                          true_operand, false_operand));
1339
1340   /* If either operand is a SAVE_EXPR (possibly surrounded by
1341      arithmetic, make sure it gets done.  */
1342   true_operand  = skip_simple_arithmetic (true_operand);
1343   false_operand = skip_simple_arithmetic (false_operand);
1344
1345   if (TREE_CODE (true_operand) == SAVE_EXPR)
1346     result = build2 (COMPOUND_EXPR, result_type, true_operand, result);
1347
1348   if (TREE_CODE (false_operand) == SAVE_EXPR)
1349     result = build2 (COMPOUND_EXPR, result_type, false_operand, result);
1350
1351   /* ??? Seems the code above is wrong, as it may move ahead of the COND
1352      SAVE_EXPRs with side effects and not shared by both arms.  */
1353
1354  if (addr_p)
1355     result = build_unary_op (INDIRECT_REF, NULL_TREE, result);
1356
1357   return result;
1358 }
1359
1360 /* Similar, but for RETURN_EXPR.  If RESULT_DECL is non-zero, build
1361    a RETURN_EXPR around the assignment of RET_VAL to RESULT_DECL.
1362    If RESULT_DECL is zero, build a bare RETURN_EXPR.  */
1363
1364 tree
1365 build_return_expr (tree result_decl, tree ret_val)
1366 {
1367   tree result_expr;
1368
1369   if (result_decl)
1370     {
1371       /* The gimplifier explicitly enforces the following invariant:
1372
1373            RETURN_EXPR
1374                |
1375            MODIFY_EXPR
1376            /        \
1377           /          \
1378       RESULT_DECL    ...
1379
1380       As a consequence, type-homogeneity dictates that we use the type
1381       of the RESULT_DECL as the operation type.  */
1382
1383       tree operation_type = TREE_TYPE (result_decl);
1384
1385       /* Convert the right operand to the operation type.  Note that
1386          it's the same transformation as in the MODIFY_EXPR case of
1387          build_binary_op with the additional guarantee that the type
1388          cannot involve a placeholder, since otherwise the function
1389          would use the "target pointer" return mechanism.  */
1390
1391       if (operation_type != TREE_TYPE (ret_val))
1392         ret_val = convert (operation_type, ret_val);
1393
1394       result_expr
1395         = build2 (MODIFY_EXPR, operation_type, result_decl, ret_val);
1396     }
1397   else
1398     result_expr = NULL_TREE;
1399
1400   return build1 (RETURN_EXPR, void_type_node, result_expr);
1401 }
1402 \f
1403 /* Build a CALL_EXPR to call FUNDECL with one argument, ARG.  Return
1404    the CALL_EXPR.  */
1405
1406 tree
1407 build_call_1_expr (tree fundecl, tree arg)
1408 {
1409   tree call = build3 (CALL_EXPR, TREE_TYPE (TREE_TYPE (fundecl)),
1410                       build_unary_op (ADDR_EXPR, NULL_TREE, fundecl),
1411                       chainon (NULL_TREE, build_tree_list (NULL_TREE, arg)),
1412                       NULL_TREE);
1413
1414   TREE_SIDE_EFFECTS (call) = 1;
1415
1416   return call;
1417 }
1418
1419 /* Build a CALL_EXPR to call FUNDECL with two arguments, ARG1 & ARG2.  Return
1420    the CALL_EXPR.  */
1421
1422 tree
1423 build_call_2_expr (tree fundecl, tree arg1, tree arg2)
1424 {
1425   tree call = build3 (CALL_EXPR, TREE_TYPE (TREE_TYPE (fundecl)),
1426                       build_unary_op (ADDR_EXPR, NULL_TREE, fundecl),
1427                       chainon (chainon (NULL_TREE,
1428                                         build_tree_list (NULL_TREE, arg1)),
1429                                build_tree_list (NULL_TREE, arg2)),
1430                      NULL_TREE);
1431
1432   TREE_SIDE_EFFECTS (call) = 1;
1433
1434   return call;
1435 }
1436
1437 /* Likewise to call FUNDECL with no arguments.  */
1438
1439 tree
1440 build_call_0_expr (tree fundecl)
1441 {
1442   tree call = build3 (CALL_EXPR, TREE_TYPE (TREE_TYPE (fundecl)),
1443                       build_unary_op (ADDR_EXPR, NULL_TREE, fundecl),
1444                       NULL_TREE, NULL_TREE);
1445
1446   TREE_SIDE_EFFECTS (call) = 1;
1447
1448   return call;
1449 }
1450 \f
1451 /* Call a function that raises an exception and pass the line number and file
1452    name, if requested.  MSG says which exception function to call.
1453
1454    GNAT_NODE is the gnat node conveying the source location for which the
1455    error should be signaled, or Empty in which case the error is signaled on
1456    the current ref_file_name/input_line.  */
1457
1458 tree
1459 build_call_raise (int msg, Node_Id gnat_node)
1460 {
1461   tree fndecl = gnat_raise_decls[msg];
1462
1463   const char *str
1464     = (Debug_Flag_NN || Exception_Locations_Suppressed)
1465       ? ""
1466       : (gnat_node != Empty)
1467         ? IDENTIFIER_POINTER
1468           (get_identifier (Get_Name_String
1469                            (Debug_Source_Name
1470                             (Get_Source_File_Index (Sloc (gnat_node))))))
1471         : ref_filename;
1472
1473   int len = strlen (str) + 1;
1474   tree filename = build_string (len, str);
1475
1476   int line_number
1477     = (gnat_node != Empty)
1478       ? Get_Logical_Line_Number (Sloc(gnat_node)) : input_line;
1479
1480   TREE_TYPE (filename)
1481     = build_array_type (char_type_node,
1482                         build_index_type (build_int_cst (NULL_TREE, len)));
1483
1484   return
1485     build_call_2_expr (fndecl,
1486                        build1 (ADDR_EXPR, build_pointer_type (char_type_node),
1487                                filename),
1488                        build_int_cst (NULL_TREE, line_number));
1489 }
1490 \f
1491 /* qsort comparer for the bit positions of two constructor elements
1492    for record components.  */
1493
1494 static int
1495 compare_elmt_bitpos (const PTR rt1, const PTR rt2)
1496 {
1497   tree elmt1 = * (tree *) rt1;
1498   tree elmt2 = * (tree *) rt2;
1499
1500   tree pos_field1 = bit_position (TREE_PURPOSE (elmt1));
1501   tree pos_field2 = bit_position (TREE_PURPOSE (elmt2));
1502
1503   if (tree_int_cst_equal (pos_field1, pos_field2))
1504     return 0;
1505   else if (tree_int_cst_lt (pos_field1, pos_field2))
1506     return -1;
1507   else
1508     return 1;
1509 }
1510
1511 /* Return a CONSTRUCTOR of TYPE whose list is LIST.  */
1512
1513 tree
1514 gnat_build_constructor (tree type, tree list)
1515 {
1516   tree elmt;
1517   int n_elmts;
1518   bool allconstant = (TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST);
1519   bool side_effects = false;
1520   tree result;
1521
1522   /* Scan the elements to see if they are all constant or if any has side
1523      effects, to let us set global flags on the resulting constructor.  Count
1524      the elements along the way for possible sorting purposes below.  */
1525   for (n_elmts = 0, elmt = list; elmt; elmt = TREE_CHAIN (elmt), n_elmts ++)
1526     {
1527       if (!TREE_CONSTANT (TREE_VALUE (elmt))
1528           || (TREE_CODE (type) == RECORD_TYPE
1529               && DECL_BIT_FIELD (TREE_PURPOSE (elmt))
1530               && TREE_CODE (TREE_VALUE (elmt)) != INTEGER_CST)
1531           || !initializer_constant_valid_p (TREE_VALUE (elmt),
1532                                             TREE_TYPE (TREE_VALUE (elmt))))
1533         allconstant = false;
1534
1535       if (TREE_SIDE_EFFECTS (TREE_VALUE (elmt)))
1536         side_effects = true;
1537
1538       /* Propagate an NULL_EXPR from the size of the type.  We won't ever
1539          be executing the code we generate here in that case, but handle it
1540          specially to avoid the cmpiler blowing up.  */
1541       if (TREE_CODE (type) == RECORD_TYPE
1542           && (0 != (result
1543                     = contains_null_expr (DECL_SIZE (TREE_PURPOSE (elmt))))))
1544         return build1 (NULL_EXPR, type, TREE_OPERAND (result, 0));
1545     }
1546
1547   /* For record types with constant components only, sort field list
1548      by increasing bit position.  This is necessary to ensure the
1549      constructor can be output as static data, which the gimplifier
1550      might force in various circumstances. */
1551   if (allconstant && TREE_CODE (type) == RECORD_TYPE && n_elmts > 1)
1552     {
1553       /* Fill an array with an element tree per index, and ask qsort to order
1554          them according to what a bitpos comparison function says.  */
1555
1556       tree *gnu_arr = (tree *) alloca (sizeof (tree) * n_elmts);
1557       int i;
1558
1559       for (i = 0, elmt = list; elmt; elmt = TREE_CHAIN (elmt), i++)
1560         gnu_arr[i] = elmt;
1561
1562       qsort (gnu_arr, n_elmts, sizeof (tree), compare_elmt_bitpos);
1563
1564       /* Then reconstruct the list from the sorted array contents.  */
1565
1566       list = NULL_TREE;
1567       for (i = n_elmts - 1; i >= 0; i--)
1568         {
1569           TREE_CHAIN (gnu_arr[i]) = list;
1570           list = gnu_arr[i];
1571         }
1572     }
1573
1574   result = build_constructor_from_list (type, list);
1575   TREE_CONSTANT (result) = TREE_INVARIANT (result)
1576     = TREE_STATIC (result) = allconstant;
1577   TREE_SIDE_EFFECTS (result) = side_effects;
1578   TREE_READONLY (result) = TYPE_READONLY (type) || allconstant;
1579   return result;
1580 }
1581 \f
1582 /* Return a COMPONENT_REF to access a field that is given by COMPONENT,
1583    an IDENTIFIER_NODE giving the name of the field, or FIELD, a FIELD_DECL,
1584    for the field.  Don't fold the result if NO_FOLD_P is true.
1585
1586    We also handle the fact that we might have been passed a pointer to the
1587    actual record and know how to look for fields in variant parts.  */
1588
1589 static tree
1590 build_simple_component_ref (tree record_variable, tree component,
1591                             tree field, bool no_fold_p)
1592 {
1593   tree record_type = TYPE_MAIN_VARIANT (TREE_TYPE (record_variable));
1594   tree ref;
1595
1596   gcc_assert ((TREE_CODE (record_type) == RECORD_TYPE
1597                || TREE_CODE (record_type) == UNION_TYPE
1598                || TREE_CODE (record_type) == QUAL_UNION_TYPE)
1599               && TYPE_SIZE (record_type)
1600               && (component != 0) != (field != 0));
1601
1602   /* If no field was specified, look for a field with the specified name
1603      in the current record only.  */
1604   if (!field)
1605     for (field = TYPE_FIELDS (record_type); field;
1606          field = TREE_CHAIN (field))
1607       if (DECL_NAME (field) == component)
1608         break;
1609
1610   if (!field)
1611     return NULL_TREE;
1612
1613   /* If this field is not in the specified record, see if we can find
1614      something in the record whose original field is the same as this one. */
1615   if (DECL_CONTEXT (field) != record_type)
1616     /* Check if there is a field with name COMPONENT in the record.  */
1617     {
1618       tree new_field;
1619
1620       /* First loop thru normal components.  */
1621
1622       for (new_field = TYPE_FIELDS (record_type); new_field;
1623            new_field = TREE_CHAIN (new_field))
1624         if (field == new_field
1625             || DECL_ORIGINAL_FIELD (new_field) == field
1626             || new_field == DECL_ORIGINAL_FIELD (field)
1627             || (DECL_ORIGINAL_FIELD (field)
1628                 && (DECL_ORIGINAL_FIELD (field)
1629                     == DECL_ORIGINAL_FIELD (new_field))))
1630           break;
1631
1632       /* Next, loop thru DECL_INTERNAL_P components if we haven't found
1633          the component in the first search. Doing this search in 2 steps
1634          is required to avoiding hidden homonymous fields in the
1635          _Parent field.  */
1636
1637       if (!new_field)
1638         for (new_field = TYPE_FIELDS (record_type); new_field;
1639              new_field = TREE_CHAIN (new_field))
1640           if (DECL_INTERNAL_P (new_field))
1641             {
1642               tree field_ref
1643                 = build_simple_component_ref (record_variable,
1644                                               NULL_TREE, new_field, no_fold_p);
1645               ref = build_simple_component_ref (field_ref, NULL_TREE, field,
1646                                                 no_fold_p);
1647
1648               if (ref)
1649                 return ref;
1650             }
1651
1652       field = new_field;
1653     }
1654
1655   if (!field)
1656     return NULL_TREE;
1657
1658   /* If the field's offset has overflowed, do not attempt to access it
1659      as doing so may trigger sanity checks deeper in the back-end.
1660      Note that we don't need to warn since this will be done on trying
1661      to declare the object.  */
1662   if (TREE_CODE (DECL_FIELD_OFFSET (field)) == INTEGER_CST
1663       && TREE_CONSTANT_OVERFLOW (DECL_FIELD_OFFSET (field)))
1664     return NULL_TREE;
1665
1666   /* It would be nice to call "fold" here, but that can lose a type
1667      we need to tag a PLACEHOLDER_EXPR with, so we can't do it.  */
1668   ref = build3 (COMPONENT_REF, TREE_TYPE (field), record_variable, field,
1669                 NULL_TREE);
1670
1671   if (TREE_READONLY (record_variable) || TREE_READONLY (field))
1672     TREE_READONLY (ref) = 1;
1673   if (TREE_THIS_VOLATILE (record_variable) || TREE_THIS_VOLATILE (field)
1674       || TYPE_VOLATILE (record_type))
1675     TREE_THIS_VOLATILE (ref) = 1;
1676
1677   return no_fold_p ? ref : fold (ref);
1678 }
1679 \f
1680 /* Like build_simple_component_ref, except that we give an error if the
1681    reference could not be found.  */
1682
1683 tree
1684 build_component_ref (tree record_variable, tree component,
1685                      tree field, bool no_fold_p)
1686 {
1687   tree ref = build_simple_component_ref (record_variable, component, field,
1688                                          no_fold_p);
1689
1690   if (ref)
1691     return ref;
1692
1693   /* If FIELD was specified, assume this is an invalid user field so
1694      raise constraint error.  Otherwise, we can't find the type to return, so
1695      abort.  */
1696   gcc_assert (field);
1697   return build1 (NULL_EXPR, TREE_TYPE (field),
1698                  build_call_raise (CE_Discriminant_Check_Failed, Empty));
1699 }
1700 \f
1701 /* Build a GCC tree to call an allocation or deallocation function.
1702    If GNU_OBJ is nonzero, it is an object to deallocate.  Otherwise,
1703    generate an allocator.
1704
1705    GNU_SIZE is the size of the object in bytes and ALIGN is the alignment in
1706    bits.  GNAT_PROC, if present, is a procedure to call and GNAT_POOL is the
1707    storage pool to use.  If not preset, malloc and free will be used except
1708    if GNAT_PROC is the "fake" value of -1, in which case we allocate the
1709    object dynamically on the stack frame.  */
1710
1711 tree
1712 build_call_alloc_dealloc (tree gnu_obj, tree gnu_size, unsigned align,
1713                           Entity_Id gnat_proc, Entity_Id gnat_pool,
1714                           Node_Id gnat_node)
1715 {
1716   tree gnu_align = size_int (align / BITS_PER_UNIT);
1717
1718   gnu_size = SUBSTITUTE_PLACEHOLDER_IN_EXPR (gnu_size, gnu_obj);
1719
1720   if (Present (gnat_proc))
1721     {
1722       /* The storage pools are obviously always tagged types, but the
1723          secondary stack uses the same mechanism and is not tagged */
1724       if (Is_Tagged_Type (Etype (gnat_pool)))
1725         {
1726           /* The size is the third parameter; the alignment is the
1727              same type.  */
1728           Entity_Id gnat_size_type
1729             = Etype (Next_Formal (Next_Formal (First_Formal (gnat_proc))));
1730           tree gnu_size_type = gnat_to_gnu_type (gnat_size_type);
1731           tree gnu_proc = gnat_to_gnu (gnat_proc);
1732           tree gnu_proc_addr = build_unary_op (ADDR_EXPR, NULL_TREE, gnu_proc);
1733           tree gnu_pool = gnat_to_gnu (gnat_pool);
1734           tree gnu_pool_addr = build_unary_op (ADDR_EXPR, NULL_TREE, gnu_pool);
1735           tree gnu_args = NULL_TREE;
1736           tree gnu_call;
1737
1738           /* The first arg is always the address of the storage pool; next
1739              comes the address of the object, for a deallocator, then the
1740              size and alignment.  */
1741           gnu_args
1742             = chainon (gnu_args, build_tree_list (NULL_TREE, gnu_pool_addr));
1743
1744           if (gnu_obj)
1745             gnu_args
1746               = chainon (gnu_args, build_tree_list (NULL_TREE, gnu_obj));
1747
1748           gnu_args
1749             = chainon (gnu_args,
1750                        build_tree_list (NULL_TREE,
1751                                         convert (gnu_size_type, gnu_size)));
1752           gnu_args
1753             = chainon (gnu_args,
1754                        build_tree_list (NULL_TREE,
1755                                         convert (gnu_size_type, gnu_align)));
1756
1757           gnu_call = build3 (CALL_EXPR, TREE_TYPE (TREE_TYPE (gnu_proc)),
1758                              gnu_proc_addr, gnu_args, NULL_TREE);
1759           TREE_SIDE_EFFECTS (gnu_call) = 1;
1760           return gnu_call;
1761         }
1762
1763       /* Secondary stack case.  */
1764       else
1765         {
1766           /* The size is the second parameter */
1767           Entity_Id gnat_size_type
1768             = Etype (Next_Formal (First_Formal (gnat_proc)));
1769           tree gnu_size_type = gnat_to_gnu_type (gnat_size_type);
1770           tree gnu_proc = gnat_to_gnu (gnat_proc);
1771           tree gnu_proc_addr = build_unary_op (ADDR_EXPR, NULL_TREE, gnu_proc);
1772           tree gnu_args = NULL_TREE;
1773           tree gnu_call;
1774
1775           /* The first arg is the address of the object, for a
1776              deallocator, then the size */
1777           if (gnu_obj)
1778             gnu_args
1779               = chainon (gnu_args, build_tree_list (NULL_TREE, gnu_obj));
1780
1781           gnu_args
1782             = chainon (gnu_args,
1783                        build_tree_list (NULL_TREE,
1784                                         convert (gnu_size_type, gnu_size)));
1785
1786           gnu_call = build3 (CALL_EXPR, TREE_TYPE (TREE_TYPE (gnu_proc)),
1787                              gnu_proc_addr, gnu_args, NULL_TREE);
1788           TREE_SIDE_EFFECTS (gnu_call) = 1;
1789           return gnu_call;
1790         }
1791     }
1792
1793   else if (gnu_obj)
1794     return build_call_1_expr (free_decl, gnu_obj);
1795
1796   /* ??? For now, disable variable-sized allocators in the stack since
1797      we can't yet gimplify an ALLOCATE_EXPR.  */
1798   else if (gnat_pool == -1
1799            && TREE_CODE (gnu_size) == INTEGER_CST && !flag_stack_check)
1800     {
1801       /* If the size is a constant, we can put it in the fixed portion of
1802          the stack frame to avoid the need to adjust the stack pointer.  */
1803       if (TREE_CODE (gnu_size) == INTEGER_CST && !flag_stack_check)
1804         {
1805           tree gnu_range
1806             = build_range_type (NULL_TREE, size_one_node, gnu_size);
1807           tree gnu_array_type = build_array_type (char_type_node, gnu_range);
1808           tree gnu_decl
1809             = create_var_decl (get_identifier ("RETVAL"), NULL_TREE,
1810                                gnu_array_type, NULL_TREE, false, false, false,
1811                                false, NULL, gnat_node);
1812
1813           return convert (ptr_void_type_node,
1814                           build_unary_op (ADDR_EXPR, NULL_TREE, gnu_decl));
1815         }
1816       else
1817         gcc_unreachable ();
1818 #if 0
1819         return build2 (ALLOCATE_EXPR, ptr_void_type_node, gnu_size, gnu_align);
1820 #endif
1821     }
1822   else
1823     {
1824       if (Nkind (gnat_node) != N_Allocator || !Comes_From_Source (gnat_node))
1825         Check_No_Implicit_Heap_Alloc (gnat_node);
1826       return build_call_1_expr (malloc_decl, gnu_size);
1827     }
1828 }
1829 \f
1830 /* Build a GCC tree to correspond to allocating an object of TYPE whose
1831    initial value is INIT, if INIT is nonzero.  Convert the expression to
1832    RESULT_TYPE, which must be some type of pointer.  Return the tree.
1833    GNAT_PROC and GNAT_POOL optionally give the procedure to call and
1834    the storage pool to use.  GNAT_NODE is used to provide an error
1835    location for restriction violations messages.  If IGNORE_INIT_TYPE is
1836    true, ignore the type of INIT for the purpose of determining the size;
1837    this will cause the maximum size to be allocated if TYPE is of
1838    self-referential size.  */
1839
1840 tree
1841 build_allocator (tree type, tree init, tree result_type, Entity_Id gnat_proc,
1842                  Entity_Id gnat_pool, Node_Id gnat_node, bool ignore_init_type)
1843 {
1844   tree size = TYPE_SIZE_UNIT (type);
1845   tree result;
1846
1847   /* If the initializer, if present, is a NULL_EXPR, just return a new one.  */
1848   if (init && TREE_CODE (init) == NULL_EXPR)
1849     return build1 (NULL_EXPR, result_type, TREE_OPERAND (init, 0));
1850
1851   /* If RESULT_TYPE is a fat or thin pointer, set SIZE to be the sum of the
1852      sizes of the object and its template.  Allocate the whole thing and
1853      fill in the parts that are known.  */
1854   else if (TYPE_FAT_OR_THIN_POINTER_P (result_type))
1855     {
1856       tree storage_type
1857         = build_unc_object_type_from_ptr (result_type, type,
1858                                           get_identifier ("ALLOC"));
1859       tree template_type = TREE_TYPE (TYPE_FIELDS (storage_type));
1860       tree storage_ptr_type = build_pointer_type (storage_type);
1861       tree storage;
1862       tree template_cons = NULL_TREE;
1863
1864       size = SUBSTITUTE_PLACEHOLDER_IN_EXPR (TYPE_SIZE_UNIT (storage_type),
1865                                              init);
1866
1867       /* If the size overflows, pass -1 so the allocator will raise
1868          storage error.  */
1869       if (TREE_CODE (size) == INTEGER_CST && TREE_OVERFLOW (size))
1870         size = ssize_int (-1);
1871
1872       storage = build_call_alloc_dealloc (NULL_TREE, size,
1873                                           TYPE_ALIGN (storage_type),
1874                                           gnat_proc, gnat_pool, gnat_node);
1875       storage = convert (storage_ptr_type, protect_multiple_eval (storage));
1876
1877       if (TREE_CODE (type) == RECORD_TYPE && TYPE_IS_PADDING_P (type))
1878         {
1879           type = TREE_TYPE (TYPE_FIELDS (type));
1880
1881           if (init)
1882             init = convert (type, init);
1883         }
1884
1885       /* If there is an initializing expression, make a constructor for
1886          the entire object including the bounds and copy it into the
1887          object.  If there is no initializing expression, just set the
1888          bounds.  */
1889       if (init)
1890         {
1891           template_cons = tree_cons (TREE_CHAIN (TYPE_FIELDS (storage_type)),
1892                                      init, NULL_TREE);
1893           template_cons = tree_cons (TYPE_FIELDS (storage_type),
1894                                      build_template (template_type, type,
1895                                                      init),
1896                                      template_cons);
1897
1898           return convert
1899             (result_type,
1900              build2 (COMPOUND_EXPR, storage_ptr_type,
1901                      build_binary_op
1902                      (MODIFY_EXPR, storage_type,
1903                       build_unary_op (INDIRECT_REF, NULL_TREE,
1904                                       convert (storage_ptr_type, storage)),
1905                       gnat_build_constructor (storage_type, template_cons)),
1906                      convert (storage_ptr_type, storage)));
1907         }
1908       else
1909         return build2
1910           (COMPOUND_EXPR, result_type,
1911            build_binary_op
1912            (MODIFY_EXPR, template_type,
1913             build_component_ref
1914             (build_unary_op (INDIRECT_REF, NULL_TREE,
1915                              convert (storage_ptr_type, storage)),
1916              NULL_TREE, TYPE_FIELDS (storage_type), 0),
1917             build_template (template_type, type, NULL_TREE)),
1918            convert (result_type, convert (storage_ptr_type, storage)));
1919     }
1920
1921   /* If we have an initializing expression, see if its size is simpler
1922      than the size from the type.  */
1923   if (!ignore_init_type && init && TYPE_SIZE_UNIT (TREE_TYPE (init))
1924       && (TREE_CODE (TYPE_SIZE_UNIT (TREE_TYPE (init))) == INTEGER_CST
1925           || CONTAINS_PLACEHOLDER_P (size)))
1926     size = TYPE_SIZE_UNIT (TREE_TYPE (init));
1927
1928   /* If the size is still self-referential, reference the initializing
1929      expression, if it is present.  If not, this must have been a
1930      call to allocate a library-level object, in which case we use
1931      the maximum size.  */
1932   if (CONTAINS_PLACEHOLDER_P (size))
1933     {
1934       if (!ignore_init_type && init)
1935         size = substitute_placeholder_in_expr (size, init);
1936       else
1937         size = max_size (size, true);
1938     }
1939
1940   /* If the size overflows, pass -1 so the allocator will raise
1941      storage error.  */
1942   if (TREE_CODE (size) == INTEGER_CST && TREE_OVERFLOW (size))
1943     size = ssize_int (-1);
1944
1945   /* If this is a type whose alignment is larger than the
1946      biggest we support in normal alignment and this is in
1947      the default storage pool, make an "aligning type", allocate
1948      it, point to the field we need, and return that.  */
1949   if (TYPE_ALIGN (type) > BIGGEST_ALIGNMENT
1950       && No (gnat_proc))
1951     {
1952       tree new_type = make_aligning_type (type, TYPE_ALIGN (type), size);
1953
1954       result = build_call_alloc_dealloc (NULL_TREE, TYPE_SIZE_UNIT (new_type),
1955                                          BIGGEST_ALIGNMENT, Empty,
1956                                          Empty, gnat_node);
1957       result = save_expr (result);
1958       result = convert (build_pointer_type (new_type), result);
1959       result = build_unary_op (INDIRECT_REF, NULL_TREE, result);
1960       result = build_component_ref (result, NULL_TREE,
1961                                     TYPE_FIELDS (new_type), 0);
1962       result = convert (result_type,
1963                         build_unary_op (ADDR_EXPR, NULL_TREE, result));
1964     }
1965   else
1966     result = convert (result_type,
1967                       build_call_alloc_dealloc (NULL_TREE, size,
1968                                                 TYPE_ALIGN (type),
1969                                                 gnat_proc,
1970                                                 gnat_pool,
1971                                                 gnat_node));
1972
1973   /* If we have an initial value, put the new address into a SAVE_EXPR, assign
1974      the value, and return the address.  Do this with a COMPOUND_EXPR.  */
1975
1976   if (init)
1977     {
1978       result = save_expr (result);
1979       result
1980         = build2 (COMPOUND_EXPR, TREE_TYPE (result),
1981                   build_binary_op
1982                   (MODIFY_EXPR, NULL_TREE,
1983                    build_unary_op (INDIRECT_REF,
1984                                    TREE_TYPE (TREE_TYPE (result)), result),
1985                    init),
1986                   result);
1987     }
1988
1989   return convert (result_type, result);
1990 }
1991 \f
1992 /* Fill in a VMS descriptor for EXPR and return a constructor for it.
1993    GNAT_FORMAL is how we find the descriptor record.  */
1994
1995 tree
1996 fill_vms_descriptor (tree expr, Entity_Id gnat_formal)
1997 {
1998   tree record_type = TREE_TYPE (TREE_TYPE (get_gnu_tree (gnat_formal)));
1999   tree field;
2000   tree const_list = NULL_TREE;
2001
2002   expr = maybe_unconstrained_array (expr);
2003   gnat_mark_addressable (expr);
2004
2005   for (field = TYPE_FIELDS (record_type); field; field = TREE_CHAIN (field))
2006     const_list
2007       = tree_cons (field,
2008                    convert (TREE_TYPE (field),
2009                             SUBSTITUTE_PLACEHOLDER_IN_EXPR
2010                             (DECL_INITIAL (field), expr)),
2011                    const_list);
2012
2013   return gnat_build_constructor (record_type, nreverse (const_list));
2014 }
2015
2016 /* Indicate that we need to make the address of EXPR_NODE and it therefore
2017    should not be allocated in a register.  Returns true if successful.  */
2018
2019 bool
2020 gnat_mark_addressable (tree expr_node)
2021 {
2022   while (1)
2023     switch (TREE_CODE (expr_node))
2024       {
2025       case ADDR_EXPR:
2026       case COMPONENT_REF:
2027       case ARRAY_REF:
2028       case ARRAY_RANGE_REF:
2029       case REALPART_EXPR:
2030       case IMAGPART_EXPR:
2031       case VIEW_CONVERT_EXPR:
2032       case CONVERT_EXPR:
2033       case NON_LVALUE_EXPR:
2034       case NOP_EXPR:
2035         expr_node = TREE_OPERAND (expr_node, 0);
2036         break;
2037
2038       case CONSTRUCTOR:
2039         TREE_ADDRESSABLE (expr_node) = 1;
2040         return true;
2041
2042       case VAR_DECL:
2043       case PARM_DECL:
2044       case RESULT_DECL:
2045         TREE_ADDRESSABLE (expr_node) = 1;
2046         return true;
2047
2048       case FUNCTION_DECL:
2049         TREE_ADDRESSABLE (expr_node) = 1;
2050         return true;
2051
2052       case CONST_DECL:
2053         return (DECL_CONST_CORRESPONDING_VAR (expr_node)
2054                 && (gnat_mark_addressable
2055                     (DECL_CONST_CORRESPONDING_VAR (expr_node))));
2056       default:
2057         return true;
2058     }
2059 }