gcc/ada/gcc-interface/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) 1992-2010, Free Software Foundation, Inc.         *
  10  *                                                                          *
  11  * GNAT is free software;  you can  redistribute it  and/or modify it under *
  12  * terms of the  GNU General Public License as published  by the Free Soft- *
  13  * ware  Foundation;  either version 3,  or (at your option) any later ver- *
  14  * sion.  GNAT is distributed in the hope that it will be useful, but WITH- *
  15  * OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY *
  16  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License *
  17  * for  more details.  You should have received a copy of the GNU General   *
  18  * Public License along with GCC; see the file COPYING3.  If not see        *
  19  * <http://www.gnu.org/licenses/>.                                          *
  20  *                                                                          *
  21  * GNAT was originally developed  by the GNAT team at  New York University. *
  22  * Extensive contributions were provided by Ada Core Technologies Inc.      *
  23  *                                                                          *
  24  ****************************************************************************/
  25
  26 #include "config.h"
  27 #include "system.h"
  28 #include "coretypes.h"
  29 #include "tm.h"
  30 #include "tree.h"
  31 #include "ggc.h"
  32 #include "flags.h"
  33 #include "output.h"
  34 #include "tree-inline.h"
  35
  36 #include "ada.h"
  37 #include "types.h"
  38 #include "atree.h"
  39 #include "elists.h"
  40 #include "namet.h"
  41 #include "nlists.h"
  42 #include "snames.h"
  43 #include "stringt.h"
  44 #include "uintp.h"
  45 #include "fe.h"
  46 #include "sinfo.h"
  47 #include "einfo.h"
  48 #include "ada-tree.h"
  49 #include "gigi.h"
  50
  51 static tree find_common_type (tree, tree);
  52 static tree compare_arrays (tree, tree, tree);
  53 static tree nonbinary_modular_operation (enum tree_code, tree, tree, tree);
  54 static tree build_simple_component_ref (tree, tree, tree, bool);
  55 \f
  56 /* Return the base type of TYPE.  */
  57
  58 tree
  59 get_base_type (tree type)
  60 {
  61   if (TREE_CODE (type) == RECORD_TYPE
  62       && TYPE_JUSTIFIED_MODULAR_P (type))
  63     type = TREE_TYPE (TYPE_FIELDS (type));
  64
  65   while (TREE_TYPE (type)
  66          && (TREE_CODE (type) == INTEGER_TYPE
  67              || TREE_CODE (type) == REAL_TYPE))
  68     type = TREE_TYPE (type);
  69
  70   return type;
  71 }
  72 \f
  73 /* EXP is a GCC tree representing an address.  See if we can find how
  74    strictly the object at that address is aligned.   Return that alignment
  75    in bits.  If we don't know anything about the alignment, return 0.  */
  76
  77 unsigned int
  78 known_alignment (tree exp)
  79 {
  80   unsigned int this_alignment;
  81   unsigned int lhs, rhs;
  82
  83   switch (TREE_CODE (exp))
  84     {
  85     CASE_CONVERT:
  86     case VIEW_CONVERT_EXPR:
  87     case NON_LVALUE_EXPR:
  88       /* Conversions between pointers and integers don't change the alignment
  89          of the underlying object.  */
  90       this_alignment = known_alignment (TREE_OPERAND (exp, 0));
  91       break;
  92
  93     case COMPOUND_EXPR:
  94       /* The value of a COMPOUND_EXPR is that of it's second operand.  */
  95       this_alignment = known_alignment (TREE_OPERAND (exp, 1));
  96       break;
  97
  98     case PLUS_EXPR:
  99     case MINUS_EXPR:
 100       /* If two address are added, the alignment of the result is the
 101          minimum of the two alignments.  */
 102       lhs = known_alignment (TREE_OPERAND (exp, 0));
 103       rhs = known_alignment (TREE_OPERAND (exp, 1));
 104       this_alignment = MIN (lhs, rhs);
 105       break;
 106
 107     case POINTER_PLUS_EXPR:
 108       lhs = known_alignment (TREE_OPERAND (exp, 0));
 109       rhs = known_alignment (TREE_OPERAND (exp, 1));
 110       /* If we don't know the alignment of the offset, we assume that
 111          of the base.  */
 112       if (rhs == 0)
 113         this_alignment = lhs;
 114       else
 115         this_alignment = MIN (lhs, rhs);
 116       break;
 117
 118     case COND_EXPR:
 119       /* If there is a choice between two values, use the smallest one.  */
 120       lhs = known_alignment (TREE_OPERAND (exp, 1));
 121       rhs = known_alignment (TREE_OPERAND (exp, 2));
 122       this_alignment = MIN (lhs, rhs);
 123       break;
 124
 125     case INTEGER_CST:
 126       {
 127         unsigned HOST_WIDE_INT c = TREE_INT_CST_LOW (exp);
 128         /* The first part of this represents the lowest bit in the constant,
 129            but it is originally in bytes, not bits.  */
 130         this_alignment = MIN (BITS_PER_UNIT * (c & -c), BIGGEST_ALIGNMENT);
 131       }
 132       break;
 133
 134     case MULT_EXPR:
 135       /* If we know the alignment of just one side, use it.  Otherwise,
 136          use the product of the alignments.  */
 137       lhs = known_alignment (TREE_OPERAND (exp, 0));
 138       rhs = known_alignment (TREE_OPERAND (exp, 1));
 139
 140       if (lhs == 0)
 141         this_alignment = rhs;
 142       else if (rhs == 0)
 143         this_alignment = lhs;
 144       else
 145         this_alignment = MIN (lhs * rhs, BIGGEST_ALIGNMENT);
 146       break;
 147
 148     case BIT_AND_EXPR:
 149       /* A bit-and expression is as aligned as the maximum alignment of the
 150          operands.  We typically get here for a complex lhs and a constant
 151          negative power of two on the rhs to force an explicit alignment, so
 152          don't bother looking at the lhs.  */
 153       this_alignment = known_alignment (TREE_OPERAND (exp, 1));
 154       break;
 155
 156     case ADDR_EXPR:
 157       this_alignment = expr_align (TREE_OPERAND (exp, 0));
 158       break;
 159
 160     case CALL_EXPR:
 161       {
 162         tree t = maybe_inline_call_in_expr (exp);
 163         if (t)
 164           return known_alignment (t);
 165       }
 166
 167       /* Fall through... */
 168
 169     default:
 170       /* For other pointer expressions, we assume that the pointed-to object
 171          is at least as aligned as the pointed-to type.  Beware that we can
 172          have a dummy type here (e.g. a Taft Amendment type), for which the
 173          alignment is meaningless and should be ignored.  */
 174       if (POINTER_TYPE_P (TREE_TYPE (exp))
 175           && !TYPE_IS_DUMMY_P (TREE_TYPE (TREE_TYPE (exp))))
 176         this_alignment = TYPE_ALIGN (TREE_TYPE (TREE_TYPE (exp)));
 177       else
 178         this_alignment = 0;
 179       break;
 180     }
 181
 182   return this_alignment;
 183 }
 184 \f
 185 /* We have a comparison or assignment operation on two types, T1 and T2, which
 186    are either both array types or both record types.  T1 is assumed to be for
 187    the left hand side operand, and T2 for the right hand side.  Return the
 188    type that both operands should be converted to for the operation, if any.
 189    Otherwise return zero.  */
 190
 191 static tree
 192 find_common_type (tree t1, tree t2)
 193 {
 194   /* ??? As of today, various constructs lead here with types of different
 195      sizes even when both constants (e.g. tagged types, packable vs regular
 196      component types, padded vs unpadded types, ...).  While some of these
 197      would better be handled upstream (types should be made consistent before
 198      calling into build_binary_op), some others are really expected and we
 199      have to be careful.  */
 200
 201   /* We must prevent writing more than what the target may hold if this is for
 202      an assignment and the case of tagged types is handled in build_binary_op
 203      so use the lhs type if it is known to be smaller, or of constant size and
 204      the rhs type is not, whatever the modes.  We also force t1 in case of
 205      constant size equality to minimize occurrences of view conversions on the
 206      lhs of assignments.  */
 207   if (TREE_CONSTANT (TYPE_SIZE (t1))
 208       && (!TREE_CONSTANT (TYPE_SIZE (t2))
 209           || !tree_int_cst_lt (TYPE_SIZE (t2), TYPE_SIZE (t1))))
 210     return t1;
 211
 212   /* Otherwise, if the lhs type is non-BLKmode, use it.  Note that we know
 213      that we will not have any alignment problems since, if we did, the
 214      non-BLKmode type could not have been used.  */
 215   if (TYPE_MODE (t1) != BLKmode)
 216     return t1;
 217
 218   /* If the rhs type is of constant size, use it whatever the modes.  At
 219      this point it is known to be smaller, or of constant size and the
 220      lhs type is not.  */
 221   if (TREE_CONSTANT (TYPE_SIZE (t2)))
 222     return t2;
 223
 224   /* Otherwise, if the rhs type is non-BLKmode, use it.  */
 225   if (TYPE_MODE (t2) != BLKmode)
 226     return t2;
 227
 228   /* In this case, both types have variable size and BLKmode.  It's
 229      probably best to leave the "type mismatch" because changing it
 230      could cause a bad self-referential reference.  */
 231   return NULL_TREE;
 232 }
 233 \f
 234 /* Return an expression tree representing an equality comparison of A1 and A2,
 235    two objects of type ARRAY_TYPE.  The result should be of type RESULT_TYPE.
 236
 237    Two arrays are equal in one of two ways: (1) if both have zero length in
 238    some dimension (not necessarily the same dimension) or (2) if the lengths
 239    in each dimension are equal and the data is equal.  We perform the length
 240    tests in as efficient a manner as possible.  */
 241
 242 static tree
 243 compare_arrays (tree result_type, tree a1, tree a2)
 244 {
 245   tree result = convert (result_type, boolean_true_node);
 246   tree a1_is_null = convert (result_type, boolean_false_node);
 247   tree a2_is_null = convert (result_type, boolean_false_node);
 248   tree t1 = TREE_TYPE (a1);
 249   tree t2 = TREE_TYPE (a2);
 250   bool a1_side_effects_p = TREE_SIDE_EFFECTS (a1);
 251   bool a2_side_effects_p = TREE_SIDE_EFFECTS (a2);
 252   bool length_zero_p = false;
 253
 254   /* If either operand has side-effects, they have to be evaluated only once
 255      in spite of the multiple references to the operand in the comparison.  */
 256   if (a1_side_effects_p)
 257     a1 = gnat_protect_expr (a1);
 258
 259   if (a2_side_effects_p)
 260     a2 = gnat_protect_expr (a2);
 261
 262   /* Process each dimension separately and compare the lengths.  If any
 263      dimension has a length known to be zero, set LENGTH_ZERO_P to true
 264      in order to suppress the comparison of the data at the end.  */
 265   while (TREE_CODE (t1) == ARRAY_TYPE && TREE_CODE (t2) == ARRAY_TYPE)
 266     {
 267       tree lb1 = TYPE_MIN_VALUE (TYPE_DOMAIN (t1));
 268       tree ub1 = TYPE_MAX_VALUE (TYPE_DOMAIN (t1));
 269       tree lb2 = TYPE_MIN_VALUE (TYPE_DOMAIN (t2));
 270       tree ub2 = TYPE_MAX_VALUE (TYPE_DOMAIN (t2));
 271       tree length1 = size_binop (PLUS_EXPR, size_binop (MINUS_EXPR, ub1, lb1),
 272                                  size_one_node);
 273       tree length2 = size_binop (PLUS_EXPR, size_binop (MINUS_EXPR, ub2, lb2),
 274                                  size_one_node);
 275       tree comparison, this_a1_is_null, this_a2_is_null;
 276
 277       /* If the length of the first array is a constant, swap our operands
 278          unless the length of the second array is the constant zero.  */
 279       if (TREE_CODE (length1) == INTEGER_CST && !integer_zerop (length2))
 280         {
 281           tree tem;
 282           bool btem;
 283
 284           tem = a1, a1 = a2, a2 = tem;
 285           tem = t1, t1 = t2, t2 = tem;
 286           tem = lb1, lb1 = lb2, lb2 = tem;
 287           tem = ub1, ub1 = ub2, ub2 = tem;
 288           tem = length1, length1 = length2, length2 = tem;
 289           tem = a1_is_null, a1_is_null = a2_is_null, a2_is_null = tem;
 290           btem = a1_side_effects_p, a1_side_effects_p = a2_side_effects_p,
 291           a2_side_effects_p = btem;
 292         }
 293
 294       /* If the length of the second array is the constant zero, we can just
 295          use the original stored bounds for the first array and see whether
 296          last < first holds.  */
 297       if (integer_zerop (length2))
 298         {
 299           length_zero_p = true;
 300
 301           ub1 = TYPE_MAX_VALUE (TYPE_INDEX_TYPE (TYPE_DOMAIN (t1)));
 302           lb1 = TYPE_MIN_VALUE (TYPE_INDEX_TYPE (TYPE_DOMAIN (t1)));
 303
 304           comparison = build_binary_op (LT_EXPR, result_type, ub1, lb1);
 305           comparison = SUBSTITUTE_PLACEHOLDER_IN_EXPR (comparison, a1);
 306           if (EXPR_P (comparison))
 307             SET_EXPR_LOCATION (comparison, input_location);
 308
 309           this_a1_is_null = comparison;
 310           this_a2_is_null = convert (result_type, boolean_true_node);
 311         }
 312
 313       /* Otherwise, if the length is some other constant value, we know that
 314          this dimension in the second array cannot be superflat, so we can
 315          just use its length computed from the actual stored bounds.  */
 316       else if (TREE_CODE (length2) == INTEGER_CST)
 317         {
 318           tree bt;
 319
 320           ub1 = TYPE_MAX_VALUE (TYPE_INDEX_TYPE (TYPE_DOMAIN (t1)));
 321           lb1 = TYPE_MIN_VALUE (TYPE_INDEX_TYPE (TYPE_DOMAIN (t1)));
 322           /* Note that we know that UB2 and LB2 are constant and hence
 323              cannot contain a PLACEHOLDER_EXPR.  */
 324           ub2 = TYPE_MAX_VALUE (TYPE_INDEX_TYPE (TYPE_DOMAIN (t2)));
 325           lb2 = TYPE_MIN_VALUE (TYPE_INDEX_TYPE (TYPE_DOMAIN (t2)));
 326           bt = get_base_type (TREE_TYPE (ub1));
 327
 328           comparison
 329             = build_binary_op (EQ_EXPR, result_type,
 330                                build_binary_op (MINUS_EXPR, bt, ub1, lb1),
 331                                build_binary_op (MINUS_EXPR, bt, ub2, lb2));
 332           comparison = SUBSTITUTE_PLACEHOLDER_IN_EXPR (comparison, a1);
 333           if (EXPR_P (comparison))
 334             SET_EXPR_LOCATION (comparison, input_location);
 335
 336           this_a1_is_null = build_binary_op (LT_EXPR, result_type, ub1, lb1);
 337           if (EXPR_P (this_a1_is_null))
 338             SET_EXPR_LOCATION (this_a1_is_null, input_location);
 339
 340           this_a2_is_null = convert (result_type, boolean_false_node);
 341         }
 342
 343       /* Otherwise, compare the computed lengths.  */
 344       else
 345         {
 346           length1 = SUBSTITUTE_PLACEHOLDER_IN_EXPR (length1, a1);
 347           length2 = SUBSTITUTE_PLACEHOLDER_IN_EXPR (length2, a2);
 348
 349           comparison
 350             = build_binary_op (EQ_EXPR, result_type, length1, length2);
 351           if (EXPR_P (comparison))
 352             SET_EXPR_LOCATION (comparison, input_location);
 353
 354           /* If the length expression is of the form (cond ? val : 0), assume
 355              that cond is equivalent to (length != 0).  That's guaranteed by
 356              construction of the array types in gnat_to_gnu_entity.  */
 357           if (TREE_CODE (length1) == COND_EXPR
 358               && integer_zerop (TREE_OPERAND (length1, 2)))
 359             this_a1_is_null = invert_truthvalue (TREE_OPERAND (length1, 0));
 360           else
 361             this_a1_is_null = build_binary_op (EQ_EXPR, result_type, length1,
 362                                                size_zero_node);
 363           if (EXPR_P (this_a1_is_null))
 364             SET_EXPR_LOCATION (this_a1_is_null, input_location);
 365
 366           /* Likewise for the second array.  */
 367           if (TREE_CODE (length2) == COND_EXPR
 368               && integer_zerop (TREE_OPERAND (length2, 2)))
 369             this_a2_is_null = invert_truthvalue (TREE_OPERAND (length2, 0));
 370           else
 371             this_a2_is_null = build_binary_op (EQ_EXPR, result_type, length2,
 372                                                size_zero_node);
 373           if (EXPR_P (this_a2_is_null))
 374             SET_EXPR_LOCATION (this_a2_is_null, input_location);
 375         }
 376
 377       /* Append expressions for this dimension to the final expressions.  */
 378       result = build_binary_op (TRUTH_ANDIF_EXPR, result_type,
 379                                 result, comparison);
 380
 381       a1_is_null = build_binary_op (TRUTH_ORIF_EXPR, result_type,
 382                                     this_a1_is_null, a1_is_null);
 383
 384       a2_is_null = build_binary_op (TRUTH_ORIF_EXPR, result_type,
 385                                     this_a2_is_null, a2_is_null);
 386
 387       t1 = TREE_TYPE (t1);
 388       t2 = TREE_TYPE (t2);
 389     }
 390
 391   /* Unless the length of some dimension is known to be zero, compare the
 392      data in the array.  */
 393   if (!length_zero_p)
 394     {
 395       tree type = find_common_type (TREE_TYPE (a1), TREE_TYPE (a2));
 396       tree comparison;
 397
 398       if (type)
 399         {
 400           a1 = convert (type, a1),
 401           a2 = convert (type, a2);
 402         }
 403
 404       comparison = fold_build2 (EQ_EXPR, result_type, a1, a2);
 405       if (EXPR_P (comparison))
 406         SET_EXPR_LOCATION (comparison, input_location);
 407
 408       result
 409         = build_binary_op (TRUTH_ANDIF_EXPR, result_type, result, comparison);
 410     }
 411
 412   /* The result is also true if both sizes are zero.  */
 413   result = build_binary_op (TRUTH_ORIF_EXPR, result_type,
 414                             build_binary_op (TRUTH_ANDIF_EXPR, result_type,
 415                                              a1_is_null, a2_is_null),
 416                             result);
 417
 418   /* If either operand has side-effects, they have to be evaluated before
 419      starting the comparison above since the place they would be otherwise
 420      evaluated could be wrong.  */
 421   if (a1_side_effects_p)
 422     result = build2 (COMPOUND_EXPR, result_type, a1, result);
 423
 424   if (a2_side_effects_p)
 425     result = build2 (COMPOUND_EXPR, result_type, a2, result);
 426
 427   return result;
 428 }
 429 \f
 430 /* Compute the result of applying OP_CODE to LHS and RHS, where both are of
 431    type TYPE.  We know that TYPE is a modular type with a nonbinary
 432    modulus.  */
 433
 434 static tree
 435 nonbinary_modular_operation (enum tree_code op_code, tree type, tree lhs,
 436                              tree rhs)
 437 {
 438   tree modulus = TYPE_MODULUS (type);
 439   unsigned int needed_precision = tree_floor_log2 (modulus) + 1;
 440   unsigned int precision;
 441   bool unsignedp = true;
 442   tree op_type = type;
 443   tree result;
 444
 445   /* If this is an addition of a constant, convert it to a subtraction
 446      of a constant since we can do that faster.  */
 447   if (op_code == PLUS_EXPR && TREE_CODE (rhs) == INTEGER_CST)
 448     {
 449       rhs = fold_build2 (MINUS_EXPR, type, modulus, rhs);
 450       op_code = MINUS_EXPR;
 451     }
 452
 453   /* For the logical operations, we only need PRECISION bits.  For
 454      addition and subtraction, we need one more and for multiplication we
 455      need twice as many.  But we never want to make a size smaller than
 456      our size. */
 457   if (op_code == PLUS_EXPR || op_code == MINUS_EXPR)
 458     needed_precision += 1;
 459   else if (op_code == MULT_EXPR)
 460     needed_precision *= 2;
 461
 462   precision = MAX (needed_precision, TYPE_PRECISION (op_type));
 463
 464   /* Unsigned will do for everything but subtraction.  */
 465   if (op_code == MINUS_EXPR)
 466     unsignedp = false;
 467
 468   /* If our type is the wrong signedness or isn't wide enough, make a new
 469      type and convert both our operands to it.  */
 470   if (TYPE_PRECISION (op_type) < precision
 471       || TYPE_UNSIGNED (op_type) != unsignedp)
 472     {
 473       /* Copy the node so we ensure it can be modified to make it modular.  */
 474       op_type = copy_node (gnat_type_for_size (precision, unsignedp));
 475       modulus = convert (op_type, modulus);
 476       SET_TYPE_MODULUS (op_type, modulus);
 477       TYPE_MODULAR_P (op_type) = 1;
 478       lhs = convert (op_type, lhs);
 479       rhs = convert (op_type, rhs);
 480     }
 481
 482   /* Do the operation, then we'll fix it up.  */
 483   result = fold_build2 (op_code, op_type, lhs, rhs);
 484
 485   /* For multiplication, we have no choice but to do a full modulus
 486      operation.  However, we want to do this in the narrowest
 487      possible size.  */
 488   if (op_code == MULT_EXPR)
 489     {
 490       tree div_type = copy_node (gnat_type_for_size (needed_precision, 1));
 491       modulus = convert (div_type, modulus);
 492       SET_TYPE_MODULUS (div_type, modulus);
 493       TYPE_MODULAR_P (div_type) = 1;
 494       result = convert (op_type,
 495                         fold_build2 (TRUNC_MOD_EXPR, div_type,
 496                                      convert (div_type, result), modulus));
 497     }
 498
 499   /* For subtraction, add the modulus back if we are negative.  */
 500   else if (op_code == MINUS_EXPR)
 501     {
 502       result = gnat_protect_expr (result);
 503       result = fold_build3 (COND_EXPR, op_type,
 504                             fold_build2 (LT_EXPR, boolean_type_node, result,
 505                                          convert (op_type, integer_zero_node)),
 506                             fold_build2 (PLUS_EXPR, op_type, result, modulus),
 507                             result);
 508     }
 509
 510   /* For the other operations, subtract the modulus if we are >= it.  */
 511   else
 512     {
 513       result = gnat_protect_expr (result);
 514       result = fold_build3 (COND_EXPR, op_type,
 515                             fold_build2 (GE_EXPR, boolean_type_node,
 516                                          result, modulus),
 517                             fold_build2 (MINUS_EXPR, op_type,
 518                                          result, modulus),
 519                             result);
 520     }
 521
 522   return convert (type, result);
 523 }
 524 \f
 525 /* Make a binary operation of kind OP_CODE.  RESULT_TYPE is the type
 526    desired for the result.  Usually the operation is to be performed
 527    in that type.  For MODIFY_EXPR and ARRAY_REF, RESULT_TYPE may be 0
 528    in which case the type to be used will be derived from the operands.
 529
 530    This function is very much unlike the ones for C and C++ since we
 531    have already done any type conversion and matching required.  All we
 532    have to do here is validate the work done by SEM and handle subtypes.  */
 533
 534 tree
 535 build_binary_op (enum tree_code op_code, tree result_type,
 536                  tree left_operand, tree right_operand)
 537 {
 538   tree left_type  = TREE_TYPE (left_operand);
 539   tree right_type = TREE_TYPE (right_operand);
 540   tree left_base_type = get_base_type (left_type);
 541   tree right_base_type = get_base_type (right_type);
 542   tree operation_type = result_type;
 543   tree best_type = NULL_TREE;
 544   tree modulus, result;
 545   bool has_side_effects = false;
 546
 547   if (operation_type
 548       && TREE_CODE (operation_type) == RECORD_TYPE
 549       && TYPE_JUSTIFIED_MODULAR_P (operation_type))
 550     operation_type = TREE_TYPE (TYPE_FIELDS (operation_type));
 551
 552   if (operation_type
 553       && !AGGREGATE_TYPE_P (operation_type)
 554       && TYPE_EXTRA_SUBTYPE_P (operation_type))
 555     operation_type = get_base_type (operation_type);
 556
 557   modulus = (operation_type
 558              && TREE_CODE (operation_type) == INTEGER_TYPE
 559              && TYPE_MODULAR_P (operation_type)
 560              ? TYPE_MODULUS (operation_type) : NULL_TREE);
 561
 562   switch (op_code)
 563     {
 564     case INIT_EXPR:
 565     case MODIFY_EXPR:
 566       /* If there were integral or pointer conversions on the LHS, remove
 567          them; we'll be putting them back below if needed.  Likewise for
 568          conversions between array and record types, except for justified
 569          modular types.  But don't do this if the right operand is not
 570          BLKmode (for packed arrays) unless we are not changing the mode.  */
 571       while ((CONVERT_EXPR_P (left_operand)
 572               || TREE_CODE (left_operand) == VIEW_CONVERT_EXPR)
 573              && (((INTEGRAL_TYPE_P (left_type)
 574                    || POINTER_TYPE_P (left_type))
 575                   && (INTEGRAL_TYPE_P (TREE_TYPE
 576                                        (TREE_OPERAND (left_operand, 0)))
 577                       || POINTER_TYPE_P (TREE_TYPE
 578                                          (TREE_OPERAND (left_operand, 0)))))
 579                  || (((TREE_CODE (left_type) == RECORD_TYPE
 580                        && !TYPE_JUSTIFIED_MODULAR_P (left_type))
 581                       || TREE_CODE (left_type) == ARRAY_TYPE)
 582                      && ((TREE_CODE (TREE_TYPE
 583                                      (TREE_OPERAND (left_operand, 0)))
 584                           == RECORD_TYPE)
 585                          || (TREE_CODE (TREE_TYPE
 586                                         (TREE_OPERAND (left_operand, 0)))
 587                              == ARRAY_TYPE))
 588                      && (TYPE_MODE (right_type) == BLKmode
 589                          || (TYPE_MODE (left_type)
 590                              == TYPE_MODE (TREE_TYPE
 591                                            (TREE_OPERAND
 592                                             (left_operand, 0))))))))
 593         {
 594           left_operand = TREE_OPERAND (left_operand, 0);
 595           left_type = TREE_TYPE (left_operand);
 596         }
 597
 598       /* If a class-wide type may be involved, force use of the RHS type.  */
 599       if ((TREE_CODE (right_type) == RECORD_TYPE
 600            || TREE_CODE (right_type) == UNION_TYPE)
 601           && TYPE_ALIGN_OK (right_type))
 602         operation_type = right_type;
 603
 604       /* If we are copying between padded objects with compatible types, use
 605          the padded view of the objects, this is very likely more efficient.
 606          Likewise for a padded object that is assigned a constructor, if we
 607          can convert the constructor to the inner type, to avoid putting a
 608          VIEW_CONVERT_EXPR on the LHS.  But don't do so if we wouldn't have
 609          actually copied anything.  */
 610       else if (TYPE_IS_PADDING_P (left_type)
 611                && TREE_CONSTANT (TYPE_SIZE (left_type))
 612                && ((TREE_CODE (right_operand) == COMPONENT_REF
 613                     && TYPE_IS_PADDING_P
 614                        (TREE_TYPE (TREE_OPERAND (right_operand, 0)))
 615                     && gnat_types_compatible_p
 616                        (left_type,
 617                         TREE_TYPE (TREE_OPERAND (right_operand, 0))))
 618                    || (TREE_CODE (right_operand) == CONSTRUCTOR
 619                        && !CONTAINS_PLACEHOLDER_P
 620                            (DECL_SIZE (TYPE_FIELDS (left_type)))))
 621                && !integer_zerop (TYPE_SIZE (right_type)))
 622         operation_type = left_type;
 623
 624       /* Find the best type to use for copying between aggregate types.  */
 625       else if (((TREE_CODE (left_type) == ARRAY_TYPE
 626                  && TREE_CODE (right_type) == ARRAY_TYPE)
 627                 || (TREE_CODE (left_type) == RECORD_TYPE
 628                     && TREE_CODE (right_type) == RECORD_TYPE))
 629                && (best_type = find_common_type (left_type, right_type)))
 630         operation_type = best_type;
 631
 632       /* Otherwise use the LHS type.  */
 633       else if (!operation_type)
 634         operation_type = left_type;
 635
 636       /* Ensure everything on the LHS is valid.  If we have a field reference,
 637          strip anything that get_inner_reference can handle.  Then remove any
 638          conversions between types having the same code and mode.  And mark
 639          VIEW_CONVERT_EXPRs with TREE_ADDRESSABLE.  When done, we must have
 640          either an INDIRECT_REF, a NULL_EXPR or a DECL node.  */
 641       result = left_operand;
 642       while (true)
 643         {
 644           tree restype = TREE_TYPE (result);
 645
 646           if (TREE_CODE (result) == COMPONENT_REF
 647               || TREE_CODE (result) == ARRAY_REF
 648               || TREE_CODE (result) == ARRAY_RANGE_REF)
 649             while (handled_component_p (result))
 650               result = TREE_OPERAND (result, 0);
 651           else if (TREE_CODE (result) == REALPART_EXPR
 652                    || TREE_CODE (result) == IMAGPART_EXPR
 653                    || (CONVERT_EXPR_P (result)
 654                        && (((TREE_CODE (restype)
 655                              == TREE_CODE (TREE_TYPE
 656                                            (TREE_OPERAND (result, 0))))
 657                              && (TYPE_MODE (TREE_TYPE
 658                                             (TREE_OPERAND (result, 0)))
 659                                  == TYPE_MODE (restype)))
 660                            || TYPE_ALIGN_OK (restype))))
 661             result = TREE_OPERAND (result, 0);
 662           else if (TREE_CODE (result) == VIEW_CONVERT_EXPR)
 663             {
 664               TREE_ADDRESSABLE (result) = 1;
 665               result = TREE_OPERAND (result, 0);
 666             }
 667           else
 668             break;
 669         }
 670
 671       gcc_assert (TREE_CODE (result) == INDIRECT_REF
 672                   || TREE_CODE (result) == NULL_EXPR
 673                   || DECL_P (result));
 674
 675       /* Convert the right operand to the operation type unless it is
 676          either already of the correct type or if the type involves a
 677          placeholder, since the RHS may not have the same record type.  */
 678       if (operation_type != right_type
 679           && !CONTAINS_PLACEHOLDER_P (TYPE_SIZE (operation_type)))
 680         {
 681           right_operand = convert (operation_type, right_operand);
 682           right_type = operation_type;
 683         }
 684
 685       /* If the left operand is not of the same type as the operation
 686          type, wrap it up in a VIEW_CONVERT_EXPR.  */
 687       if (left_type != operation_type)
 688         left_operand = unchecked_convert (operation_type, left_operand, false);
 689
 690       has_side_effects = true;
 691       modulus = NULL_TREE;
 692       break;
 693
 694     case ARRAY_REF:
 695       if (!operation_type)
 696         operation_type = TREE_TYPE (left_type);
 697
 698       /* ... fall through ... */
 699
 700     case ARRAY_RANGE_REF:
 701       /* First look through conversion between type variants.  Note that
 702          this changes neither the operation type nor the type domain.  */
 703       if (TREE_CODE (left_operand) == VIEW_CONVERT_EXPR
 704           && TYPE_MAIN_VARIANT (TREE_TYPE (TREE_OPERAND (left_operand, 0)))
 705              == TYPE_MAIN_VARIANT (left_type))
 706         {
 707           left_operand = TREE_OPERAND (left_operand, 0);
 708           left_type = TREE_TYPE (left_operand);
 709         }
 710
 711       /* For a range, make sure the element type is consistent.  */
 712       if (op_code == ARRAY_RANGE_REF
 713           && TREE_TYPE (operation_type) != TREE_TYPE (left_type))
 714         operation_type = build_array_type (TREE_TYPE (left_type),
 715                                            TYPE_DOMAIN (operation_type));
 716
 717       /* Then convert the right operand to its base type.  This will prevent
 718          unneeded sign conversions when sizetype is wider than integer.  */
 719       right_operand = convert (right_base_type, right_operand);
 720       right_operand = convert (sizetype, right_operand);
 721
 722       if (!TREE_CONSTANT (right_operand)
 723           || !TREE_CONSTANT (TYPE_MIN_VALUE (right_type)))
 724         gnat_mark_addressable (left_operand);
 725
 726       modulus = NULL_TREE;
 727       break;
 728
 729     case TRUTH_ANDIF_EXPR:
 730     case TRUTH_ORIF_EXPR:
 731     case TRUTH_AND_EXPR:
 732     case TRUTH_OR_EXPR:
 733     case TRUTH_XOR_EXPR:
 734 #ifdef ENABLE_CHECKING
 735       gcc_assert (TREE_CODE (get_base_type (result_type)) == BOOLEAN_TYPE);
 736 #endif
 737       operation_type = left_base_type;
 738       left_operand = convert (operation_type, left_operand);
 739       right_operand = convert (operation_type, right_operand);
 740       break;
 741
 742     case GE_EXPR:
 743     case LE_EXPR:
 744     case GT_EXPR:
 745     case LT_EXPR:
 746     case EQ_EXPR:
 747     case NE_EXPR:
 748 #ifdef ENABLE_CHECKING
 749       gcc_assert (TREE_CODE (get_base_type (result_type)) == BOOLEAN_TYPE);
 750 #endif
 751       /* If either operand is a NULL_EXPR, just return a new one.  */
 752       if (TREE_CODE (left_operand) == NULL_EXPR)
 753         return build2 (op_code, result_type,
 754                        build1 (NULL_EXPR, integer_type_node,
 755                                TREE_OPERAND (left_operand, 0)),
 756                        integer_zero_node);
 757
 758       else if (TREE_CODE (right_operand) == NULL_EXPR)
 759         return build2 (op_code, result_type,
 760                        build1 (NULL_EXPR, integer_type_node,
 761                                TREE_OPERAND (right_operand, 0)),
 762                        integer_zero_node);
 763
 764       /* If either object is a justified modular types, get the
 765          fields from within.  */
 766       if (TREE_CODE (left_type) == RECORD_TYPE
 767           && TYPE_JUSTIFIED_MODULAR_P (left_type))
 768         {
 769           left_operand = convert (TREE_TYPE (TYPE_FIELDS (left_type)),
 770                                   left_operand);
 771           left_type = TREE_TYPE (left_operand);
 772           left_base_type = get_base_type (left_type);
 773         }
 774
 775       if (TREE_CODE (right_type) == RECORD_TYPE
 776           && TYPE_JUSTIFIED_MODULAR_P (right_type))
 777         {
 778           right_operand = convert (TREE_TYPE (TYPE_FIELDS (right_type)),
 779                                   right_operand);
 780           right_type = TREE_TYPE (right_operand);
 781           right_base_type = get_base_type (right_type);
 782         }
 783
 784       /* If both objects are arrays, compare them specially.  */
 785       if ((TREE_CODE (left_type) == ARRAY_TYPE
 786            || (TREE_CODE (left_type) == INTEGER_TYPE
 787                && TYPE_HAS_ACTUAL_BOUNDS_P (left_type)))
 788           && (TREE_CODE (right_type) == ARRAY_TYPE
 789               || (TREE_CODE (right_type) == INTEGER_TYPE
 790                   && TYPE_HAS_ACTUAL_BOUNDS_P (right_type))))
 791         {
 792           result = compare_arrays (result_type, left_operand, right_operand);
 793
 794           if (op_code == NE_EXPR)
 795             result = invert_truthvalue (result);
 796           else
 797             gcc_assert (op_code == EQ_EXPR);
 798
 799           return result;
 800         }
 801
 802       /* Otherwise, the base types must be the same, unless they are both fat
 803          pointer types or record types.  In the latter case, use the best type
 804          and convert both operands to that type.  */
 805       if (left_base_type != right_base_type)
 806         {
 807           if (TYPE_IS_FAT_POINTER_P (left_base_type)
 808               && TYPE_IS_FAT_POINTER_P (right_base_type))
 809             {
 810               gcc_assert (TYPE_MAIN_VARIANT (left_base_type)
 811                           == TYPE_MAIN_VARIANT (right_base_type));
 812               best_type = left_base_type;
 813             }
 814
 815           else if (TREE_CODE (left_base_type) == RECORD_TYPE
 816                    && TREE_CODE (right_base_type) == RECORD_TYPE)
 817             {
 818               /* The only way this is permitted is if both types have the same
 819                  name.  In that case, one of them must not be self-referential.
 820                  Use it as the best type.  Even better with a fixed size.  */
 821               gcc_assert (TYPE_NAME (left_base_type)
 822                           && TYPE_NAME (left_base_type)
 823                              == TYPE_NAME (right_base_type));
 824
 825               if (TREE_CONSTANT (TYPE_SIZE (left_base_type)))
 826                 best_type = left_base_type;
 827               else if (TREE_CONSTANT (TYPE_SIZE (right_base_type)))
 828                 best_type = right_base_type;
 829               else if (!CONTAINS_PLACEHOLDER_P (TYPE_SIZE (left_base_type)))
 830                 best_type = left_base_type;
 831               else if (!CONTAINS_PLACEHOLDER_P (TYPE_SIZE (right_base_type)))
 832                 best_type = right_base_type;
 833               else
 834                 gcc_unreachable ();
 835             }
 836
 837           else
 838             gcc_unreachable ();
 839
 840           left_operand = convert (best_type, left_operand);
 841           right_operand = convert (best_type, right_operand);
 842         }
 843       else
 844         {
 845           left_operand = convert (left_base_type, left_operand);
 846           right_operand = convert (right_base_type, right_operand);
 847         }
 848
 849       /* If we are comparing a fat pointer against zero, we just need to
 850          compare the data pointer.  */
 851       if (TYPE_IS_FAT_POINTER_P (left_base_type)
 852           && TREE_CODE (right_operand) == CONSTRUCTOR
 853           && integer_zerop (VEC_index (constructor_elt,
 854                                        CONSTRUCTOR_ELTS (right_operand),
 855                                        0)->value))
 856         {
 857           left_operand
 858             = build_component_ref (left_operand, NULL_TREE,
 859                                    TYPE_FIELDS (left_base_type), false);
 860           right_operand
 861             = convert (TREE_TYPE (left_operand), integer_zero_node);
 862         }
 863
 864       modulus = NULL_TREE;
 865       break;
 866
 867     case LSHIFT_EXPR:
 868     case RSHIFT_EXPR:
 869     case LROTATE_EXPR:
 870     case RROTATE_EXPR:
 871        /* The RHS of a shift can be any type.  Also, ignore any modulus
 872          (we used to abort, but this is needed for unchecked conversion
 873          to modular types).  Otherwise, processing is the same as normal.  */
 874       gcc_assert (operation_type == left_base_type);
 875       modulus = NULL_TREE;
 876       left_operand = convert (operation_type, left_operand);
 877       break;
 878
 879     case BIT_AND_EXPR:
 880     case BIT_IOR_EXPR:
 881     case BIT_XOR_EXPR:
 882       /* For binary modulus, if the inputs are in range, so are the
 883          outputs.  */
 884       if (modulus && integer_pow2p (modulus))
 885         modulus = NULL_TREE;
 886       goto common;
 887
 888     case COMPLEX_EXPR:
 889       gcc_assert (TREE_TYPE (result_type) == left_base_type
 890                   && TREE_TYPE (result_type) == right_base_type);
 891       left_operand = convert (left_base_type, left_operand);
 892       right_operand = convert (right_base_type, right_operand);
 893       break;
 894
 895     case TRUNC_DIV_EXPR:   case TRUNC_MOD_EXPR:
 896     case CEIL_DIV_EXPR:    case CEIL_MOD_EXPR:
 897     case FLOOR_DIV_EXPR:   case FLOOR_MOD_EXPR:
 898     case ROUND_DIV_EXPR:   case ROUND_MOD_EXPR:
 899       /* These always produce results lower than either operand.  */
 900       modulus = NULL_TREE;
 901       goto common;
 902
 903     case POINTER_PLUS_EXPR:
 904       gcc_assert (operation_type == left_base_type
 905                   && sizetype == right_base_type);
 906       left_operand = convert (operation_type, left_operand);
 907       right_operand = convert (sizetype, right_operand);
 908       break;
 909
 910     case PLUS_NOMOD_EXPR:
 911     case MINUS_NOMOD_EXPR:
 912       if (op_code == PLUS_NOMOD_EXPR)
 913         op_code = PLUS_EXPR;
 914       else
 915         op_code = MINUS_EXPR;
 916       modulus = NULL_TREE;
 917
 918       /* ... fall through ... */
 919
 920     case PLUS_EXPR:
 921     case MINUS_EXPR:
 922       /* Avoid doing arithmetics in ENUMERAL_TYPE or BOOLEAN_TYPE like the
 923          other compilers.  Contrary to C, Ada doesn't allow arithmetics in
 924          these types but can generate addition/subtraction for Succ/Pred.  */
 925       if (operation_type
 926           && (TREE_CODE (operation_type) == ENUMERAL_TYPE
 927               || TREE_CODE (operation_type) == BOOLEAN_TYPE))
 928         operation_type = left_base_type = right_base_type
 929           = gnat_type_for_mode (TYPE_MODE (operation_type),
 930                                 TYPE_UNSIGNED (operation_type));
 931
 932       /* ... fall through ... */
 933
 934     default:
 935     common:
 936       /* The result type should be the same as the base types of the
 937          both operands (and they should be the same).  Convert
 938          everything to the result type.  */
 939
 940       gcc_assert (operation_type == left_base_type
 941                   && left_base_type == right_base_type);
 942       left_operand = convert (operation_type, left_operand);
 943       right_operand = convert (operation_type, right_operand);
 944     }
 945
 946   if (modulus && !integer_pow2p (modulus))
 947     {
 948       result = nonbinary_modular_operation (op_code, operation_type,
 949                                             left_operand, right_operand);
 950       modulus = NULL_TREE;
 951     }
 952   /* If either operand is a NULL_EXPR, just return a new one.  */
 953   else if (TREE_CODE (left_operand) == NULL_EXPR)
 954     return build1 (NULL_EXPR, operation_type, TREE_OPERAND (left_operand, 0));
 955   else if (TREE_CODE (right_operand) == NULL_EXPR)
 956     return build1 (NULL_EXPR, operation_type, TREE_OPERAND (right_operand, 0));
 957   else if (op_code == ARRAY_REF || op_code == ARRAY_RANGE_REF)
 958     result = fold (build4 (op_code, operation_type, left_operand,
 959                            right_operand, NULL_TREE, NULL_TREE));
 960   else
 961     result
 962       = fold_build2 (op_code, operation_type, left_operand, right_operand);
 963
 964   TREE_SIDE_EFFECTS (result) |= has_side_effects;
 965   TREE_CONSTANT (result)
 966     |= (TREE_CONSTANT (left_operand) & TREE_CONSTANT (right_operand)
 967         && op_code != ARRAY_REF && op_code != ARRAY_RANGE_REF);
 968
 969   if ((op_code == ARRAY_REF || op_code == ARRAY_RANGE_REF)
 970       && TYPE_VOLATILE (operation_type))
 971     TREE_THIS_VOLATILE (result) = 1;
 972
 973   /* If we are working with modular types, perform the MOD operation
 974      if something above hasn't eliminated the need for it.  */
 975   if (modulus)
 976     result = fold_build2 (FLOOR_MOD_EXPR, operation_type, result,
 977                           convert (operation_type, modulus));
 978
 979   if (result_type && result_type != operation_type)
 980     result = convert (result_type, result);
 981
 982   return result;
 983 }
 984 \f
 985 /* Similar, but for unary operations.  */
 986
 987 tree
 988 build_unary_op (enum tree_code op_code, tree result_type, tree operand)
 989 {
 990   tree type = TREE_TYPE (operand);
 991   tree base_type = get_base_type (type);
 992   tree operation_type = result_type;
 993   tree result;
 994   bool side_effects = false;
 995
 996   if (operation_type
 997       && TREE_CODE (operation_type) == RECORD_TYPE
 998       && TYPE_JUSTIFIED_MODULAR_P (operation_type))
 999     operation_type = TREE_TYPE (TYPE_FIELDS (operation_type));
1000
1001   if (operation_type
1002       && !AGGREGATE_TYPE_P (operation_type)
1003       && TYPE_EXTRA_SUBTYPE_P (operation_type))
1004     operation_type = get_base_type (operation_type);
1005
1006   switch (op_code)
1007     {
1008     case REALPART_EXPR:
1009     case IMAGPART_EXPR:
1010       if (!operation_type)
1011         result_type = operation_type = TREE_TYPE (type);
1012       else
1013         gcc_assert (result_type == TREE_TYPE (type));
1014
1015       result = fold_build1 (op_code, operation_type, operand);
1016       break;
1017
1018     case TRUTH_NOT_EXPR:
1019 #ifdef ENABLE_CHECKING
1020       gcc_assert (TREE_CODE (get_base_type (result_type)) == BOOLEAN_TYPE);
1021 #endif
1022       result = invert_truthvalue (operand);
1023       break;
1024
1025     case ATTR_ADDR_EXPR:
1026     case ADDR_EXPR:
1027       switch (TREE_CODE (operand))
1028         {
1029         case INDIRECT_REF:
1030         case UNCONSTRAINED_ARRAY_REF:
1031           result = TREE_OPERAND (operand, 0);
1032
1033           /* Make sure the type here is a pointer, not a reference.
1034              GCC wants pointer types for function addresses.  */
1035           if (!result_type)
1036             result_type = build_pointer_type (type);
1037
1038           /* If the underlying object can alias everything, propagate the
1039              property since we are effectively retrieving the object.  */
1040           if (POINTER_TYPE_P (TREE_TYPE (result))
1041               && TYPE_REF_CAN_ALIAS_ALL (TREE_TYPE (result)))
1042             {
1043               if (TREE_CODE (result_type) == POINTER_TYPE
1044                   && !TYPE_REF_CAN_ALIAS_ALL (result_type))
1045                 result_type
1046                   = build_pointer_type_for_mode (TREE_TYPE (result_type),
1047                                                  TYPE_MODE (result_type),
1048                                                  true);
1049               else if (TREE_CODE (result_type) == REFERENCE_TYPE
1050                        && !TYPE_REF_CAN_ALIAS_ALL (result_type))
1051                 result_type
1052                   = build_reference_type_for_mode (TREE_TYPE (result_type),
1053                                                    TYPE_MODE (result_type),
1054                                                    true);
1055             }
1056           break;
1057
1058         case NULL_EXPR:
1059           result = operand;
1060           TREE_TYPE (result) = type = build_pointer_type (type);
1061           break;
1062
1063         case COMPOUND_EXPR:
1064           /* Fold a compound expression if it has unconstrained array type
1065              since the middle-end cannot handle it.  But we don't it in the
1066              general case because it may introduce aliasing issues if the
1067              first operand is an indirect assignment and the second operand
1068              the corresponding address, e.g. for an allocator.  */
1069           if (TREE_CODE (type) == UNCONSTRAINED_ARRAY_TYPE)
1070             {
1071               result = build_unary_op (ADDR_EXPR, result_type,
1072                                        TREE_OPERAND (operand, 1));
1073               result = build2 (COMPOUND_EXPR, TREE_TYPE (result),
1074                                TREE_OPERAND (operand, 0), result);
1075               break;
1076             }
1077           goto common;
1078
1079         case ARRAY_REF:
1080         case ARRAY_RANGE_REF:
1081         case COMPONENT_REF:
1082         case BIT_FIELD_REF:
1083             /* If this is for 'Address, find the address of the prefix and add
1084                the offset to the field.  Otherwise, do this the normal way.  */
1085           if (op_code == ATTR_ADDR_EXPR)
1086             {
1087               HOST_WIDE_INT bitsize;
1088               HOST_WIDE_INT bitpos;
1089               tree offset, inner;
1090               enum machine_mode mode;
1091               int unsignedp, volatilep;
1092
1093               inner = get_inner_reference (operand, &bitsize, &bitpos, &offset,
1094                                            &mode, &unsignedp, &volatilep,
1095                                            false);
1096
1097               /* If INNER is a padding type whose field has a self-referential
1098                  size, convert to that inner type.  We know the offset is zero
1099                  and we need to have that type visible.  */
1100               if (TYPE_IS_PADDING_P (TREE_TYPE (inner))
1101                   && CONTAINS_PLACEHOLDER_P
1102                      (TYPE_SIZE (TREE_TYPE (TYPE_FIELDS
1103                                             (TREE_TYPE (inner))))))
1104                 inner = convert (TREE_TYPE (TYPE_FIELDS (TREE_TYPE (inner))),
1105                                  inner);
1106
1107               /* Compute the offset as a byte offset from INNER.  */
1108               if (!offset)
1109                 offset = size_zero_node;
1110
1111               offset = size_binop (PLUS_EXPR, offset,
1112                                    size_int (bitpos / BITS_PER_UNIT));
1113
1114               /* Take the address of INNER, convert the offset to void *, and
1115                  add then.  It will later be converted to the desired result
1116                  type, if any.  */
1117               inner = build_unary_op (ADDR_EXPR, NULL_TREE, inner);
1118               inner = convert (ptr_void_type_node, inner);
1119               result = build_binary_op (POINTER_PLUS_EXPR, ptr_void_type_node,
1120                                         inner, offset);
1121               result = convert (build_pointer_type (TREE_TYPE (operand)),
1122                                 result);
1123               break;
1124             }
1125           goto common;
1126
1127         case CONSTRUCTOR:
1128           /* If this is just a constructor for a padded record, we can
1129              just take the address of the single field and convert it to
1130              a pointer to our type.  */
1131           if (TYPE_IS_PADDING_P (type))
1132             {
1133               result = VEC_index (constructor_elt,
1134                                   CONSTRUCTOR_ELTS (operand),
1135                                   0)->value;
1136               result = convert (build_pointer_type (TREE_TYPE (operand)),
1137                                 build_unary_op (ADDR_EXPR, NULL_TREE, result));
1138               break;
1139             }
1140
1141           goto common;
1142
1143         case NOP_EXPR:
1144           if (AGGREGATE_TYPE_P (type)
1145               && AGGREGATE_TYPE_P (TREE_TYPE (TREE_OPERAND (operand, 0))))
1146             return build_unary_op (ADDR_EXPR, result_type,
1147                                    TREE_OPERAND (operand, 0));
1148
1149           /* ... fallthru ... */
1150
1151         case VIEW_CONVERT_EXPR:
1152           /* If this just a variant conversion or if the conversion doesn't
1153              change the mode, get the result type from this type and go down.
1154              This is needed for conversions of CONST_DECLs, to eventually get
1155              to the address of their CORRESPONDING_VARs.  */
1156           if ((TYPE_MAIN_VARIANT (type)
1157                == TYPE_MAIN_VARIANT (TREE_TYPE (TREE_OPERAND (operand, 0))))
1158               || (TYPE_MODE (type) != BLKmode
1159                   && (TYPE_MODE (type)
1160                       == TYPE_MODE (TREE_TYPE (TREE_OPERAND (operand, 0))))))
1161             return build_unary_op (ADDR_EXPR,
1162                                    (result_type ? result_type
1163                                     : build_pointer_type (type)),
1164                                    TREE_OPERAND (operand, 0));
1165           goto common;
1166
1167         case CONST_DECL:
1168           operand = DECL_CONST_CORRESPONDING_VAR (operand);
1169
1170           /* ... fall through ... */
1171
1172         default:
1173         common:
1174
1175           /* If we are taking the address of a padded record whose field is
1176              contains a template, take the address of the template.  */
1177           if (TYPE_IS_PADDING_P (type)
1178               && TREE_CODE (TREE_TYPE (TYPE_FIELDS (type))) == RECORD_TYPE
1179               && TYPE_CONTAINS_TEMPLATE_P (TREE_TYPE (TYPE_FIELDS (type))))
1180             {
1181               type = TREE_TYPE (TYPE_FIELDS (type));
1182               operand = convert (type, operand);
1183             }
1184
1185           gnat_mark_addressable (operand);
1186           result = build_fold_addr_expr (operand);
1187         }
1188
1189       TREE_CONSTANT (result) = staticp (operand) || TREE_CONSTANT (operand);
1190       break;
1191
1192     case INDIRECT_REF:
1193       /* If we want to refer to an unconstrained array, use the appropriate
1194          expression to do so.  This will never survive down to the back-end.
1195          But if TYPE is a thin pointer, first convert to a fat pointer.  */
1196       if (TYPE_IS_THIN_POINTER_P (type)
1197           && TYPE_UNCONSTRAINED_ARRAY (TREE_TYPE (type)))
1198         {
1199           operand
1200             = convert (TREE_TYPE (TYPE_UNCONSTRAINED_ARRAY (TREE_TYPE (type))),
1201                        operand);
1202           type = TREE_TYPE (operand);
1203         }
1204
1205       if (TYPE_IS_FAT_POINTER_P (type))
1206         {
1207           result = build1 (UNCONSTRAINED_ARRAY_REF,
1208                            TYPE_UNCONSTRAINED_ARRAY (type), operand);
1209           TREE_READONLY (result)
1210             = TYPE_READONLY (TYPE_UNCONSTRAINED_ARRAY (type));
1211         }
1212
1213       /* If we are dereferencing an ADDR_EXPR, return its operand.  */
1214       else if (TREE_CODE (operand) == ADDR_EXPR)
1215         result = TREE_OPERAND (operand, 0);
1216
1217       /* Otherwise, build and fold the indirect reference.  */
1218       else
1219         {
1220           result = build_fold_indirect_ref (operand);
1221           TREE_READONLY (result) = TYPE_READONLY (TREE_TYPE (type));
1222         }
1223
1224       side_effects
1225         = (!TYPE_IS_FAT_POINTER_P (type) && TYPE_VOLATILE (TREE_TYPE (type)));
1226       break;
1227
1228     case NEGATE_EXPR:
1229     case BIT_NOT_EXPR:
1230       {
1231         tree modulus = ((operation_type
1232                          && TREE_CODE (operation_type) == INTEGER_TYPE
1233                          && TYPE_MODULAR_P (operation_type))
1234                         ? TYPE_MODULUS (operation_type) : NULL_TREE);
1235         int mod_pow2 = modulus && integer_pow2p (modulus);
1236
1237         /* If this is a modular type, there are various possibilities
1238            depending on the operation and whether the modulus is a
1239            power of two or not.  */
1240
1241         if (modulus)
1242           {
1243             gcc_assert (operation_type == base_type);
1244             operand = convert (operation_type, operand);
1245
1246             /* The fastest in the negate case for binary modulus is
1247                the straightforward code; the TRUNC_MOD_EXPR below
1248                is an AND operation.  */
1249             if (op_code == NEGATE_EXPR && mod_pow2)
1250               result = fold_build2 (TRUNC_MOD_EXPR, operation_type,
1251                                     fold_build1 (NEGATE_EXPR, operation_type,
1252                                                  operand),
1253                                     modulus);
1254
1255             /* For nonbinary negate case, return zero for zero operand,
1256                else return the modulus minus the operand.  If the modulus
1257                is a power of two minus one, we can do the subtraction
1258                as an XOR since it is equivalent and faster on most machines. */
1259             else if (op_code == NEGATE_EXPR && !mod_pow2)
1260               {
1261                 if (integer_pow2p (fold_build2 (PLUS_EXPR, operation_type,
1262                                                 modulus,
1263                                                 convert (operation_type,
1264                                                          integer_one_node))))
1265                   result = fold_build2 (BIT_XOR_EXPR, operation_type,
1266                                         operand, modulus);
1267                 else
1268                   result = fold_build2 (MINUS_EXPR, operation_type,
1269                                         modulus, operand);
1270
1271                 result = fold_build3 (COND_EXPR, operation_type,
1272                                       fold_build2 (NE_EXPR,
1273                                                    boolean_type_node,
1274                                                    operand,
1275                                                    convert
1276                                                      (operation_type,
1277                                                       integer_zero_node)),
1278                                       result, operand);
1279               }
1280             else
1281               {
1282                 /* For the NOT cases, we need a constant equal to
1283                    the modulus minus one.  For a binary modulus, we
1284                    XOR against the constant and subtract the operand from
1285                    that constant for nonbinary modulus.  */
1286
1287                 tree cnst = fold_build2 (MINUS_EXPR, operation_type, modulus,
1288                                          convert (operation_type,
1289                                                   integer_one_node));
1290
1291                 if (mod_pow2)
1292                   result = fold_build2 (BIT_XOR_EXPR, operation_type,
1293                                         operand, cnst);
1294                 else
1295                   result = fold_build2 (MINUS_EXPR, operation_type,
1296                                         cnst, operand);
1297               }
1298
1299             break;
1300           }
1301       }
1302
1303       /* ... fall through ... */
1304
1305     default:
1306       gcc_assert (operation_type == base_type);
1307       result = fold_build1 (op_code, operation_type,
1308                             convert (operation_type, operand));
1309     }
1310
1311   if (side_effects)
1312     {
1313       TREE_SIDE_EFFECTS (result) = 1;
1314       if (TREE_CODE (result) == INDIRECT_REF)
1315         TREE_THIS_VOLATILE (result) = TYPE_VOLATILE (TREE_TYPE (result));
1316     }
1317
1318   if (result_type && TREE_TYPE (result) != result_type)
1319     result = convert (result_type, result);
1320
1321   return result;
1322 }
1323 \f
1324 /* Similar, but for COND_EXPR.  */
1325
1326 tree
1327 build_cond_expr (tree result_type, tree condition_operand,
1328                  tree true_operand, tree false_operand)
1329 {
1330   bool addr_p = false;
1331   tree result;
1332
1333   /* The front-end verified that result, true and false operands have
1334      same base type.  Convert everything to the result type.  */
1335   true_operand = convert (result_type, true_operand);
1336   false_operand = convert (result_type, false_operand);
1337
1338   /* If the result type is unconstrained, take the address of the operands and
1339      then dereference the result.  Likewise if the result type is passed by
1340      reference, but this is natively handled in the gimplifier.  */
1341   if (TREE_CODE (result_type) == UNCONSTRAINED_ARRAY_TYPE
1342       || CONTAINS_PLACEHOLDER_P (TYPE_SIZE (result_type)))
1343     {
1344       result_type = build_pointer_type (result_type);
1345       true_operand = build_unary_op (ADDR_EXPR, result_type, true_operand);
1346       false_operand = build_unary_op (ADDR_EXPR, result_type, false_operand);
1347       addr_p = true;
1348     }
1349
1350   result = fold_build3 (COND_EXPR, result_type, condition_operand,
1351                         true_operand, false_operand);
1352
1353   /* If we have a common SAVE_EXPR (possibly surrounded by arithmetics)
1354      in both arms, make sure it gets evaluated by moving it ahead of the
1355      conditional expression.  This is necessary because it is evaluated
1356      in only one place at run time and would otherwise be uninitialized
1357      in one of the arms.  */
1358   true_operand = skip_simple_arithmetic (true_operand);
1359   false_operand = skip_simple_arithmetic (false_operand);
1360
1361   if (true_operand == false_operand && TREE_CODE (true_operand) == SAVE_EXPR)
1362     result = build2 (COMPOUND_EXPR, result_type, true_operand, result);
1363
1364   if (addr_p)
1365     result = build_unary_op (INDIRECT_REF, NULL_TREE, result);
1366
1367   return result;
1368 }
1369
1370 /* Similar, but for RETURN_EXPR.  If RET_VAL is non-null, build a RETURN_EXPR
1371    around the assignment of RET_VAL to RET_OBJ.  Otherwise just build a bare
1372    RETURN_EXPR around RESULT_OBJ, which may be null in this case.  */
1373
1374 tree
1375 build_return_expr (tree ret_obj, tree ret_val)
1376 {
1377   tree result_expr;
1378
1379   if (ret_val)
1380     {
1381       /* The gimplifier explicitly enforces the following invariant:
1382
1383               RETURN_EXPR
1384                   |
1385               MODIFY_EXPR
1386               /        \
1387              /          \
1388          RET_OBJ        ...
1389
1390          As a consequence, type consistency dictates that we use the type
1391          of the RET_OBJ as the operation type.  */
1392       tree operation_type = TREE_TYPE (ret_obj);
1393
1394       /* Convert the right operand to the operation type.  Note that it's the
1395          same transformation as in the MODIFY_EXPR case of build_binary_op,
1396          with the assumption that the type cannot involve a placeholder.  */
1397       if (operation_type != TREE_TYPE (ret_val))
1398         ret_val = convert (operation_type, ret_val);
1399
1400       result_expr = build2 (MODIFY_EXPR, operation_type, ret_obj, ret_val);
1401     }
1402   else
1403     result_expr = ret_obj;
1404
1405   return build1 (RETURN_EXPR, void_type_node, result_expr);
1406 }
1407 \f
1408 /* Build a CALL_EXPR to call FUNDECL with one argument, ARG.  Return
1409    the CALL_EXPR.  */
1410
1411 tree
1412 build_call_1_expr (tree fundecl, tree arg)
1413 {
1414   tree call = build_call_nary (TREE_TYPE (TREE_TYPE (fundecl)),
1415                                build_unary_op (ADDR_EXPR, NULL_TREE, fundecl),
1416                                1, arg);
1417   TREE_SIDE_EFFECTS (call) = 1;
1418   return call;
1419 }
1420
1421 /* Build a CALL_EXPR to call FUNDECL with two arguments, ARG1 & ARG2.  Return
1422    the CALL_EXPR.  */
1423
1424 tree
1425 build_call_2_expr (tree fundecl, tree arg1, tree arg2)
1426 {
1427   tree call = build_call_nary (TREE_TYPE (TREE_TYPE (fundecl)),
1428                                build_unary_op (ADDR_EXPR, NULL_TREE, fundecl),
1429                                2, arg1, arg2);
1430   TREE_SIDE_EFFECTS (call) = 1;
1431   return call;
1432 }
1433
1434 /* Likewise to call FUNDECL with no arguments.  */
1435
1436 tree
1437 build_call_0_expr (tree fundecl)
1438 {
1439   /* We rely on build_call_nary to compute TREE_SIDE_EFFECTS.  This makes
1440      it possible to propagate DECL_IS_PURE on parameterless functions.  */
1441   tree call = build_call_nary (TREE_TYPE (TREE_TYPE (fundecl)),
1442                                build_unary_op (ADDR_EXPR, NULL_TREE, fundecl),
1443                                0);
1444   return call;
1445 }
1446 \f
1447 /* Call a function that raises an exception and pass the line number and file
1448    name, if requested.  MSG says which exception function to call.
1449
1450    GNAT_NODE is the gnat node conveying the source location for which the
1451    error should be signaled, or Empty in which case the error is signaled on
1452    the current ref_file_name/input_line.
1453
1454    KIND says which kind of exception this is for
1455    (N_Raise_{Constraint,Storage,Program}_Error).  */
1456
1457 tree
1458 build_call_raise (int msg, Node_Id gnat_node, char kind)
1459 {
1460   tree fndecl = gnat_raise_decls[msg];
1461   tree label = get_exception_label (kind);
1462   tree filename;
1463   int line_number;
1464   const char *str;
1465   int len;
1466
1467   /* If this is to be done as a goto, handle that case.  */
1468   if (label)
1469     {
1470       Entity_Id local_raise = Get_Local_Raise_Call_Entity ();
1471       tree gnu_result = build1 (GOTO_EXPR, void_type_node, label);
1472
1473       /* If Local_Raise is present, generate
1474          Local_Raise (exception'Identity);  */
1475       if (Present (local_raise))
1476         {
1477           tree gnu_local_raise
1478             = gnat_to_gnu_entity (local_raise, NULL_TREE, 0);
1479           tree gnu_exception_entity
1480             = gnat_to_gnu_entity (Get_RT_Exception_Entity (msg), NULL_TREE, 0);
1481           tree gnu_call
1482             = build_call_1_expr (gnu_local_raise,
1483                                  build_unary_op (ADDR_EXPR, NULL_TREE,
1484                                                  gnu_exception_entity));
1485
1486           gnu_result = build2 (COMPOUND_EXPR, void_type_node,
1487                                gnu_call, gnu_result);}
1488
1489       return gnu_result;
1490     }
1491
1492   str
1493     = (Debug_Flag_NN || Exception_Locations_Suppressed)
1494       ? ""
1495       : (gnat_node != Empty && Sloc (gnat_node) != No_Location)
1496         ? IDENTIFIER_POINTER
1497           (get_identifier (Get_Name_String
1498                            (Debug_Source_Name
1499                             (Get_Source_File_Index (Sloc (gnat_node))))))
1500         : ref_filename;
1501
1502   len = strlen (str);
1503   filename = build_string (len, str);
1504   line_number
1505     = (gnat_node != Empty && Sloc (gnat_node) != No_Location)
1506       ? Get_Logical_Line_Number (Sloc(gnat_node)) : input_line;
1507
1508   TREE_TYPE (filename) = build_array_type (unsigned_char_type_node,
1509                                            build_index_type (size_int (len)));
1510
1511   return
1512     build_call_2_expr (fndecl,
1513                        build1 (ADDR_EXPR,
1514                                build_pointer_type (unsigned_char_type_node),
1515                                filename),
1516                        build_int_cst (NULL_TREE, line_number));
1517 }
1518 \f
1519 /* qsort comparer for the bit positions of two constructor elements
1520    for record components.  */
1521
1522 static int
1523 compare_elmt_bitpos (const PTR rt1, const PTR rt2)
1524 {
1525   const_tree const elmt1 = * (const_tree const *) rt1;
1526   const_tree const elmt2 = * (const_tree const *) rt2;
1527   const_tree const field1 = TREE_PURPOSE (elmt1);
1528   const_tree const field2 = TREE_PURPOSE (elmt2);
1529   const int ret
1530     = tree_int_cst_compare (bit_position (field1), bit_position (field2));
1531
1532   return ret ? ret : (int) (DECL_UID (field1) - DECL_UID (field2));
1533 }
1534
1535 /* Return a CONSTRUCTOR of TYPE whose list is LIST.  */
1536
1537 tree
1538 gnat_build_constructor (tree type, tree list)
1539 {
1540   bool allconstant = (TREE_CODE (TYPE_SIZE (type)) == INTEGER_CST);
1541   bool side_effects = false;
1542   tree elmt, result;
1543   int n_elmts;
1544
1545   /* Scan the elements to see if they are all constant or if any has side
1546      effects, to let us set global flags on the resulting constructor.  Count
1547      the elements along the way for possible sorting purposes below.  */
1548   for (n_elmts = 0, elmt = list; elmt; elmt = TREE_CHAIN (elmt), n_elmts ++)
1549     {
1550       tree obj = TREE_PURPOSE (elmt);
1551       tree val = TREE_VALUE (elmt);
1552
1553       /* The predicate must be in keeping with output_constructor.  */
1554       if (!TREE_CONSTANT (val)
1555           || (TREE_CODE (type) == RECORD_TYPE
1556               && CONSTRUCTOR_BITFIELD_P (obj)
1557               && !initializer_constant_valid_for_bitfield_p (val))
1558           || !initializer_constant_valid_p (val, TREE_TYPE (val)))
1559         allconstant = false;
1560
1561       if (TREE_SIDE_EFFECTS (val))
1562         side_effects = true;
1563     }
1564
1565   /* For record types with constant components only, sort field list
1566      by increasing bit position.  This is necessary to ensure the
1567      constructor can be output as static data.  */
1568   if (allconstant && TREE_CODE (type) == RECORD_TYPE && n_elmts > 1)
1569     {
1570       /* Fill an array with an element tree per index, and ask qsort to order
1571          them according to what a bitpos comparison function says.  */
1572       tree *gnu_arr = (tree *) alloca (sizeof (tree) * n_elmts);
1573       int i;
1574
1575       for (i = 0, elmt = list; elmt; elmt = TREE_CHAIN (elmt), i++)
1576         gnu_arr[i] = elmt;
1577
1578       qsort (gnu_arr, n_elmts, sizeof (tree), compare_elmt_bitpos);
1579
1580       /* Then reconstruct the list from the sorted array contents.  */
1581       list = NULL_TREE;
1582       for (i = n_elmts - 1; i >= 0; i--)
1583         {
1584           TREE_CHAIN (gnu_arr[i]) = list;
1585           list = gnu_arr[i];
1586         }
1587     }
1588
1589   result = build_constructor_from_list (type, list);
1590   TREE_CONSTANT (result) = TREE_STATIC (result) = allconstant;
1591   TREE_SIDE_EFFECTS (result) = side_effects;
1592   TREE_READONLY (result) = TYPE_READONLY (type) || allconstant;
1593   return result;
1594 }
1595 \f
1596 /* Return a COMPONENT_REF to access a field that is given by COMPONENT,
1597    an IDENTIFIER_NODE giving the name of the field, or FIELD, a FIELD_DECL,
1598    for the field.  Don't fold the result if NO_FOLD_P is true.
1599
1600    We also handle the fact that we might have been passed a pointer to the
1601    actual record and know how to look for fields in variant parts.  */
1602
1603 static tree
1604 build_simple_component_ref (tree record_variable, tree component,
1605                             tree field, bool no_fold_p)
1606 {
1607   tree record_type = TYPE_MAIN_VARIANT (TREE_TYPE (record_variable));
1608   tree ref, inner_variable;
1609
1610   gcc_assert ((TREE_CODE (record_type) == RECORD_TYPE
1611                || TREE_CODE (record_type) == UNION_TYPE
1612                || TREE_CODE (record_type) == QUAL_UNION_TYPE)
1613               && TYPE_SIZE (record_type)
1614               && (component != 0) != (field != 0));
1615
1616   /* If no field was specified, look for a field with the specified name
1617      in the current record only.  */
1618   if (!field)
1619     for (field = TYPE_FIELDS (record_type); field;
1620          field = TREE_CHAIN (field))
1621       if (DECL_NAME (field) == component)
1622         break;
1623
1624   if (!field)
1625     return NULL_TREE;
1626
1627   /* If this field is not in the specified record, see if we can find
1628      something in the record whose original field is the same as this one. */
1629   if (DECL_CONTEXT (field) != record_type)
1630     /* Check if there is a field with name COMPONENT in the record.  */
1631     {
1632       tree new_field;
1633
1634       /* First loop thru normal components.  */
1635       for (new_field = TYPE_FIELDS (record_type); new_field;
1636            new_field = TREE_CHAIN (new_field))
1637         if (SAME_FIELD_P (field, new_field))
1638           break;
1639
1640       /* Next, loop thru DECL_INTERNAL_P components if we haven't found
1641          the component in the first search. Doing this search in 2 steps
1642          is required to avoiding hidden homonymous fields in the
1643          _Parent field.  */
1644       if (!new_field)
1645         for (new_field = TYPE_FIELDS (record_type); new_field;
1646              new_field = TREE_CHAIN (new_field))
1647           if (DECL_INTERNAL_P (new_field))
1648             {
1649               tree field_ref
1650                 = build_simple_component_ref (record_variable,
1651                                               NULL_TREE, new_field, no_fold_p);
1652               ref = build_simple_component_ref (field_ref, NULL_TREE, field,
1653                                                 no_fold_p);
1654
1655               if (ref)
1656                 return ref;
1657             }
1658
1659       field = new_field;
1660     }
1661
1662   if (!field)
1663     return NULL_TREE;
1664
1665   /* If the field's offset has overflowed, do not attempt to access it
1666      as doing so may trigger sanity checks deeper in the back-end.
1667      Note that we don't need to warn since this will be done on trying
1668      to declare the object.  */
1669   if (TREE_CODE (DECL_FIELD_OFFSET (field)) == INTEGER_CST
1670       && TREE_OVERFLOW (DECL_FIELD_OFFSET (field)))
1671     return NULL_TREE;
1672
1673   /* Look through conversion between type variants.  Note that this
1674      is transparent as far as the field is concerned.  */
1675   if (TREE_CODE (record_variable) == VIEW_CONVERT_EXPR
1676       && TYPE_MAIN_VARIANT (TREE_TYPE (TREE_OPERAND (record_variable, 0)))
1677          == record_type)
1678     inner_variable = TREE_OPERAND (record_variable, 0);
1679   else
1680     inner_variable = record_variable;
1681
1682   ref = build3 (COMPONENT_REF, TREE_TYPE (field), inner_variable, field,
1683                 NULL_TREE);
1684
1685   if (TREE_READONLY (record_variable) || TREE_READONLY (field))
1686     TREE_READONLY (ref) = 1;
1687   if (TREE_THIS_VOLATILE (record_variable) || TREE_THIS_VOLATILE (field)
1688       || TYPE_VOLATILE (record_type))
1689     TREE_THIS_VOLATILE (ref) = 1;
1690
1691   if (no_fold_p)
1692     return ref;
1693
1694   /* The generic folder may punt in this case because the inner array type
1695      can be self-referential, but folding is in fact not problematic.  */
1696   else if (TREE_CODE (record_variable) == CONSTRUCTOR
1697            && TYPE_CONTAINS_TEMPLATE_P (TREE_TYPE (record_variable)))
1698     {
1699       VEC(constructor_elt,gc) *elts = CONSTRUCTOR_ELTS (record_variable);
1700       unsigned HOST_WIDE_INT idx;
1701       tree index, value;
1702       FOR_EACH_CONSTRUCTOR_ELT (elts, idx, index, value)
1703         if (index == field)
1704           return value;
1705       return ref;
1706     }
1707
1708   else
1709     return fold (ref);
1710 }
1711 \f
1712 /* Like build_simple_component_ref, except that we give an error if the
1713    reference could not be found.  */
1714
1715 tree
1716 build_component_ref (tree record_variable, tree component,
1717                      tree field, bool no_fold_p)
1718 {
1719   tree ref = build_simple_component_ref (record_variable, component, field,
1720                                          no_fold_p);
1721
1722   if (ref)
1723     return ref;
1724
1725   /* If FIELD was specified, assume this is an invalid user field so raise
1726      Constraint_Error.  Otherwise, we have no type to return so abort.  */
1727   gcc_assert (field);
1728   return build1 (NULL_EXPR, TREE_TYPE (field),
1729                  build_call_raise (CE_Discriminant_Check_Failed, Empty,
1730                                    N_Raise_Constraint_Error));
1731 }
1732 \f
1733 /* Helper for build_call_alloc_dealloc, with arguments to be interpreted
1734    identically.  Process the case where a GNAT_PROC to call is provided.  */
1735
1736 static inline tree
1737 build_call_alloc_dealloc_proc (tree gnu_obj, tree gnu_size, tree gnu_type,
1738                                Entity_Id gnat_proc, Entity_Id gnat_pool)
1739 {
1740   tree gnu_proc = gnat_to_gnu (gnat_proc);
1741   tree gnu_proc_addr = build_unary_op (ADDR_EXPR, NULL_TREE, gnu_proc);
1742   tree gnu_call;
1743
1744   /* The storage pools are obviously always tagged types, but the
1745      secondary stack uses the same mechanism and is not tagged.  */
1746   if (Is_Tagged_Type (Etype (gnat_pool)))
1747     {
1748       /* The size is the third parameter; the alignment is the
1749          same type.  */
1750       Entity_Id gnat_size_type
1751         = Etype (Next_Formal (Next_Formal (First_Formal (gnat_proc))));
1752       tree gnu_size_type = gnat_to_gnu_type (gnat_size_type);
1753
1754       tree gnu_pool = gnat_to_gnu (gnat_pool);
1755       tree gnu_pool_addr = build_unary_op (ADDR_EXPR, NULL_TREE, gnu_pool);
1756       tree gnu_align = size_int (TYPE_ALIGN (gnu_type) / BITS_PER_UNIT);
1757
1758       gnu_size = convert (gnu_size_type, gnu_size);
1759       gnu_align = convert (gnu_size_type, gnu_align);
1760
1761       /* The first arg is always the address of the storage pool; next
1762          comes the address of the object, for a deallocator, then the
1763          size and alignment.  */
1764       if (gnu_obj)
1765         gnu_call = build_call_nary (TREE_TYPE (TREE_TYPE (gnu_proc)),
1766                                     gnu_proc_addr, 4, gnu_pool_addr,
1767                                     gnu_obj, gnu_size, gnu_align);
1768       else
1769         gnu_call = build_call_nary (TREE_TYPE (TREE_TYPE (gnu_proc)),
1770                                     gnu_proc_addr, 3, gnu_pool_addr,
1771                                     gnu_size, gnu_align);
1772     }
1773
1774   /* Secondary stack case.  */
1775   else
1776     {
1777       /* The size is the second parameter.  */
1778       Entity_Id gnat_size_type
1779         = Etype (Next_Formal (First_Formal (gnat_proc)));
1780       tree gnu_size_type = gnat_to_gnu_type (gnat_size_type);
1781
1782       gnu_size = convert (gnu_size_type, gnu_size);
1783
1784       /* The first arg is the address of the object, for a deallocator,
1785          then the size.  */
1786       if (gnu_obj)
1787         gnu_call = build_call_nary (TREE_TYPE (TREE_TYPE (gnu_proc)),
1788                                     gnu_proc_addr, 2, gnu_obj, gnu_size);
1789       else
1790         gnu_call = build_call_nary (TREE_TYPE (TREE_TYPE (gnu_proc)),
1791                                     gnu_proc_addr, 1, gnu_size);
1792     }
1793
1794   TREE_SIDE_EFFECTS (gnu_call) = 1;
1795   return gnu_call;
1796 }
1797
1798 /* Helper for build_call_alloc_dealloc, to build and return an allocator for
1799    DATA_SIZE bytes aimed at containing a DATA_TYPE object, using the default
1800    __gnat_malloc allocator.  Honor DATA_TYPE alignments greater than what the
1801    latter offers.  */
1802
1803 static inline tree
1804 maybe_wrap_malloc (tree data_size, tree data_type, Node_Id gnat_node)
1805 {
1806   /* When the DATA_TYPE alignment is stricter than what malloc offers
1807      (super-aligned case), we allocate an "aligning" wrapper type and return
1808      the address of its single data field with the malloc's return value
1809      stored just in front.  */
1810
1811   unsigned int data_align = TYPE_ALIGN (data_type);
1812   unsigned int default_allocator_alignment
1813       = get_target_default_allocator_alignment () * BITS_PER_UNIT;
1814
1815   tree aligning_type
1816     = ((data_align > default_allocator_alignment)
1817        ? make_aligning_type (data_type, data_align, data_size,
1818                              default_allocator_alignment,
1819                              POINTER_SIZE / BITS_PER_UNIT)
1820        : NULL_TREE);
1821
1822   tree size_to_malloc
1823     = aligning_type ? TYPE_SIZE_UNIT (aligning_type) : data_size;
1824
1825   tree malloc_ptr;
1826
1827   /* On VMS, if 64-bit memory is disabled or pointers are 64-bit and the
1828      allocator size is 32-bit or Convention C, allocate 32-bit memory.  */
1829   if (TARGET_ABI_OPEN_VMS
1830       && (!TARGET_MALLOC64
1831           || (POINTER_SIZE == 64
1832               && (UI_To_Int (Esize (Etype (gnat_node))) == 32
1833                   || Convention (Etype (gnat_node)) == Convention_C))))
1834     malloc_ptr = build_call_1_expr (malloc32_decl, size_to_malloc);
1835   else
1836     malloc_ptr = build_call_1_expr (malloc_decl, size_to_malloc);
1837
1838   if (aligning_type)
1839     {
1840       /* Latch malloc's return value and get a pointer to the aligning field
1841          first.  */
1842       tree storage_ptr = gnat_protect_expr (malloc_ptr);
1843
1844       tree aligning_record_addr
1845         = convert (build_pointer_type (aligning_type), storage_ptr);
1846
1847       tree aligning_record
1848         = build_unary_op (INDIRECT_REF, NULL_TREE, aligning_record_addr);
1849
1850       tree aligning_field
1851         = build_component_ref (aligning_record, NULL_TREE,
1852                                TYPE_FIELDS (aligning_type), false);
1853
1854       tree aligning_field_addr
1855         = build_unary_op (ADDR_EXPR, NULL_TREE, aligning_field);
1856
1857       /* Then arrange to store the allocator's return value ahead
1858          and return.  */
1859       tree storage_ptr_slot_addr
1860         = build_binary_op (POINTER_PLUS_EXPR, ptr_void_type_node,
1861                            convert (ptr_void_type_node, aligning_field_addr),
1862                            size_int (-(HOST_WIDE_INT) POINTER_SIZE
1863                                      / BITS_PER_UNIT));
1864
1865       tree storage_ptr_slot
1866         = build_unary_op (INDIRECT_REF, NULL_TREE,
1867                           convert (build_pointer_type (ptr_void_type_node),
1868                                    storage_ptr_slot_addr));
1869
1870       return
1871         build2 (COMPOUND_EXPR, TREE_TYPE (aligning_field_addr),
1872                 build_binary_op (MODIFY_EXPR, NULL_TREE,
1873                                  storage_ptr_slot, storage_ptr),
1874                 aligning_field_addr);
1875     }
1876   else
1877     return malloc_ptr;
1878 }
1879
1880 /* Helper for build_call_alloc_dealloc, to release a DATA_TYPE object
1881    designated by DATA_PTR using the __gnat_free entry point.  */
1882
1883 static inline tree
1884 maybe_wrap_free (tree data_ptr, tree data_type)
1885 {
1886   /* In the regular alignment case, we pass the data pointer straight to free.
1887      In the superaligned case, we need to retrieve the initial allocator
1888      return value, stored in front of the data block at allocation time.  */
1889
1890   unsigned int data_align = TYPE_ALIGN (data_type);
1891   unsigned int default_allocator_alignment
1892       = get_target_default_allocator_alignment () * BITS_PER_UNIT;
1893
1894   tree free_ptr;
1895
1896   if (data_align > default_allocator_alignment)
1897     {
1898       /* DATA_FRONT_PTR (void *)
1899          = (void *)DATA_PTR - (void *)sizeof (void *))  */
1900       tree data_front_ptr
1901         = build_binary_op
1902           (POINTER_PLUS_EXPR, ptr_void_type_node,
1903            convert (ptr_void_type_node, data_ptr),
1904            size_int (-(HOST_WIDE_INT) POINTER_SIZE / BITS_PER_UNIT));
1905
1906       /* FREE_PTR (void *) = *(void **)DATA_FRONT_PTR  */
1907       free_ptr
1908         = build_unary_op
1909           (INDIRECT_REF, NULL_TREE,
1910            convert (build_pointer_type (ptr_void_type_node), data_front_ptr));
1911     }
1912   else
1913     free_ptr = data_ptr;
1914
1915   return build_call_1_expr (free_decl, free_ptr);
1916 }
1917
1918 /* Build a GCC tree to call an allocation or deallocation function.
1919    If GNU_OBJ is nonzero, it is an object to deallocate.  Otherwise,
1920    generate an allocator.
1921
1922    GNU_SIZE is the number of bytes to allocate and GNU_TYPE is the contained
1923    object type, used to determine the to-be-honored address alignment.
1924    GNAT_PROC, if present, is a procedure to call and GNAT_POOL is the storage
1925    pool to use.  If not present, malloc and free are used.  GNAT_NODE is used
1926    to provide an error location for restriction violation messages.  */
1927
1928 tree
1929 build_call_alloc_dealloc (tree gnu_obj, tree gnu_size, tree gnu_type,
1930                           Entity_Id gnat_proc, Entity_Id gnat_pool,
1931                           Node_Id gnat_node)
1932 {
1933   gnu_size = SUBSTITUTE_PLACEHOLDER_IN_EXPR (gnu_size, gnu_obj);
1934
1935   /* Explicit proc to call ?  This one is assumed to deal with the type
1936      alignment constraints.  */
1937   if (Present (gnat_proc))
1938     return build_call_alloc_dealloc_proc (gnu_obj, gnu_size, gnu_type,
1939                                           gnat_proc, gnat_pool);
1940
1941   /* Otherwise, object to "free" or "malloc" with possible special processing
1942      for alignments stricter than what the default allocator honors.  */
1943   else if (gnu_obj)
1944     return maybe_wrap_free (gnu_obj, gnu_type);
1945   else
1946     {
1947       /* Assert that we no longer can be called with this special pool.  */
1948       gcc_assert (gnat_pool != -1);
1949
1950       /* Check that we aren't violating the associated restriction.  */
1951       if (!(Nkind (gnat_node) == N_Allocator && Comes_From_Source (gnat_node)))
1952         Check_No_Implicit_Heap_Alloc (gnat_node);
1953
1954       return maybe_wrap_malloc (gnu_size, gnu_type, gnat_node);
1955     }
1956 }
1957 \f
1958 /* Build a GCC tree to correspond to allocating an object of TYPE whose
1959    initial value is INIT, if INIT is nonzero.  Convert the expression to
1960    RESULT_TYPE, which must be some type of pointer.  Return the tree.
1961
1962    GNAT_PROC and GNAT_POOL optionally give the procedure to call and
1963    the storage pool to use.  GNAT_NODE is used to provide an error
1964    location for restriction violation messages.  If IGNORE_INIT_TYPE is
1965    true, ignore the type of INIT for the purpose of determining the size;
1966    this will cause the maximum size to be allocated if TYPE is of
1967    self-referential size.  */
1968
1969 tree
1970 build_allocator (tree type, tree init, tree result_type, Entity_Id gnat_proc,
1971                  Entity_Id gnat_pool, Node_Id gnat_node, bool ignore_init_type)
1972 {
1973   tree size = TYPE_SIZE_UNIT (type);
1974   tree result;
1975
1976   /* If the initializer, if present, is a NULL_EXPR, just return a new one.  */
1977   if (init && TREE_CODE (init) == NULL_EXPR)
1978     return build1 (NULL_EXPR, result_type, TREE_OPERAND (init, 0));
1979
1980   /* If RESULT_TYPE is a fat or thin pointer, set SIZE to be the sum of the
1981      sizes of the object and its template.  Allocate the whole thing and
1982      fill in the parts that are known.  */
1983   else if (TYPE_IS_FAT_OR_THIN_POINTER_P (result_type))
1984     {
1985       tree storage_type
1986         = build_unc_object_type_from_ptr (result_type, type,
1987                                           get_identifier ("ALLOC"));
1988       tree template_type = TREE_TYPE (TYPE_FIELDS (storage_type));
1989       tree storage_ptr_type = build_pointer_type (storage_type);
1990       tree storage;
1991       tree template_cons = NULL_TREE;
1992
1993       size = SUBSTITUTE_PLACEHOLDER_IN_EXPR (TYPE_SIZE_UNIT (storage_type),
1994                                              init);
1995
1996       /* If the size overflows, pass -1 so the allocator will raise
1997          storage error.  */
1998       if (TREE_CODE (size) == INTEGER_CST && TREE_OVERFLOW (size))
1999         size = ssize_int (-1);
2000
2001       storage = build_call_alloc_dealloc (NULL_TREE, size, storage_type,
2002                                           gnat_proc, gnat_pool, gnat_node);
2003       storage = convert (storage_ptr_type, gnat_protect_expr (storage));
2004
2005       if (TYPE_IS_PADDING_P (type))
2006         {
2007           type = TREE_TYPE (TYPE_FIELDS (type));
2008           if (init)
2009             init = convert (type, init);
2010         }
2011
2012       /* If there is an initializing expression, make a constructor for
2013          the entire object including the bounds and copy it into the
2014          object.  If there is no initializing expression, just set the
2015          bounds.  */
2016       if (init)
2017         {
2018           template_cons = tree_cons (TREE_CHAIN (TYPE_FIELDS (storage_type)),
2019                                      init, NULL_TREE);
2020           template_cons = tree_cons (TYPE_FIELDS (storage_type),
2021                                      build_template (template_type, type,
2022                                                      init),
2023                                      template_cons);
2024
2025           return convert
2026             (result_type,
2027              build2 (COMPOUND_EXPR, storage_ptr_type,
2028                      build_binary_op
2029                      (MODIFY_EXPR, storage_type,
2030                       build_unary_op (INDIRECT_REF, NULL_TREE,
2031                                       convert (storage_ptr_type, storage)),
2032                       gnat_build_constructor (storage_type, template_cons)),
2033                      convert (storage_ptr_type, storage)));
2034         }
2035       else
2036         return build2
2037           (COMPOUND_EXPR, result_type,
2038            build_binary_op
2039            (MODIFY_EXPR, template_type,
2040             build_component_ref
2041             (build_unary_op (INDIRECT_REF, NULL_TREE,
2042                              convert (storage_ptr_type, storage)),
2043              NULL_TREE, TYPE_FIELDS (storage_type), false),
2044             build_template (template_type, type, NULL_TREE)),
2045            convert (result_type, convert (storage_ptr_type, storage)));
2046     }
2047
2048   /* If we have an initializing expression, see if its size is simpler
2049      than the size from the type.  */
2050   if (!ignore_init_type && init && TYPE_SIZE_UNIT (TREE_TYPE (init))
2051       && (TREE_CODE (TYPE_SIZE_UNIT (TREE_TYPE (init))) == INTEGER_CST
2052           || CONTAINS_PLACEHOLDER_P (size)))
2053     size = TYPE_SIZE_UNIT (TREE_TYPE (init));
2054
2055   /* If the size is still self-referential, reference the initializing
2056      expression, if it is present.  If not, this must have been a
2057      call to allocate a library-level object, in which case we use
2058      the maximum size.  */
2059   if (CONTAINS_PLACEHOLDER_P (size))
2060     {
2061       if (!ignore_init_type && init)
2062         size = substitute_placeholder_in_expr (size, init);
2063       else
2064         size = max_size (size, true);
2065     }
2066
2067   /* If the size overflows, pass -1 so the allocator will raise
2068      storage error.  */
2069   if (TREE_CODE (size) == INTEGER_CST && TREE_OVERFLOW (size))
2070     size = ssize_int (-1);
2071
2072   result = convert (result_type,
2073                     build_call_alloc_dealloc (NULL_TREE, size, type,
2074                                               gnat_proc, gnat_pool,
2075                                               gnat_node));
2076
2077   /* If we have an initial value, protect the new address, assign the value
2078      and return the address with a COMPOUND_EXPR.  */
2079   if (init)
2080     {
2081       result = gnat_protect_expr (result);
2082       result
2083         = build2 (COMPOUND_EXPR, TREE_TYPE (result),
2084                   build_binary_op
2085                   (MODIFY_EXPR, NULL_TREE,
2086                    build_unary_op (INDIRECT_REF,
2087                                    TREE_TYPE (TREE_TYPE (result)), result),
2088                    init),
2089                   result);
2090     }
2091
2092   return convert (result_type, result);
2093 }
2094 \f
2095 /* Fill in a VMS descriptor for EXPR and return a constructor for it.
2096    GNAT_FORMAL is how we find the descriptor record.  GNAT_ACTUAL is
2097    how we derive the source location to raise C_E on an out of range
2098    pointer. */
2099
2100 tree
2101 fill_vms_descriptor (tree expr, Entity_Id gnat_formal, Node_Id gnat_actual)
2102 {
2103   tree parm_decl = get_gnu_tree (gnat_formal);
2104   tree record_type = TREE_TYPE (TREE_TYPE (parm_decl));
2105   tree const_list = NULL_TREE, field;
2106   const bool do_range_check
2107     = strcmp ("MBO",
2108               IDENTIFIER_POINTER (DECL_NAME (TYPE_FIELDS (record_type))));
2109
2110   expr = maybe_unconstrained_array (expr);
2111   gnat_mark_addressable (expr);
2112
2113   for (field = TYPE_FIELDS (record_type); field; field = TREE_CHAIN (field))
2114     {
2115       tree conexpr = convert (TREE_TYPE (field),
2116                               SUBSTITUTE_PLACEHOLDER_IN_EXPR
2117                               (DECL_INITIAL (field), expr));
2118
2119       /* Check to ensure that only 32-bit pointers are passed in
2120          32-bit descriptors */
2121       if (do_range_check
2122           && strcmp (IDENTIFIER_POINTER (DECL_NAME (field)), "POINTER") == 0)
2123         {
2124           tree pointer64type
2125             = build_pointer_type_for_mode (void_type_node, DImode, false);
2126           tree addr64expr = build_unary_op (ADDR_EXPR, pointer64type, expr);
2127           tree malloc64low
2128             = build_int_cstu (long_integer_type_node, 0x80000000);
2129
2130           add_stmt (build3 (COND_EXPR, void_type_node,
2131                             build_binary_op (GE_EXPR, boolean_type_node,
2132                                              convert (long_integer_type_node,
2133                                                       addr64expr),
2134                                              malloc64low),
2135                             build_call_raise (CE_Range_Check_Failed,
2136                                               gnat_actual,
2137                                               N_Raise_Constraint_Error),
2138                             NULL_TREE));
2139         }
2140       const_list = tree_cons (field, conexpr, const_list);
2141     }
2142
2143   return gnat_build_constructor (record_type, nreverse (const_list));
2144 }
2145
2146 /* Indicate that we need to take the address of T and that it therefore
2147    should not be allocated in a register.  Returns true if successful.  */
2148
2149 bool
2150 gnat_mark_addressable (tree t)
2151 {
2152   while (true)
2153     switch (TREE_CODE (t))
2154       {
2155       case ADDR_EXPR:
2156       case COMPONENT_REF:
2157       case ARRAY_REF:
2158       case ARRAY_RANGE_REF:
2159       case REALPART_EXPR:
2160       case IMAGPART_EXPR:
2161       case VIEW_CONVERT_EXPR:
2162       case NON_LVALUE_EXPR:
2163       CASE_CONVERT:
2164         t = TREE_OPERAND (t, 0);
2165         break;
2166
2167       case COMPOUND_EXPR:
2168         t = TREE_OPERAND (t, 1);
2169         break;
2170
2171       case CONSTRUCTOR:
2172         TREE_ADDRESSABLE (t) = 1;
2173         return true;
2174
2175       case VAR_DECL:
2176       case PARM_DECL:
2177       case RESULT_DECL:
2178         TREE_ADDRESSABLE (t) = 1;
2179         return true;
2180
2181       case FUNCTION_DECL:
2182         TREE_ADDRESSABLE (t) = 1;
2183         return true;
2184
2185       case CONST_DECL:
2186         return DECL_CONST_CORRESPONDING_VAR (t)
2187                && gnat_mark_addressable (DECL_CONST_CORRESPONDING_VAR (t));
2188
2189       default:
2190         return true;
2191     }
2192 }
2193 \f
2194 /* Save EXP for later use or reuse.  This is equivalent to save_expr in tree.c
2195    but we know how to handle our own nodes.  */
2196
2197 tree
2198 gnat_save_expr (tree exp)
2199 {
2200   tree type = TREE_TYPE (exp);
2201   enum tree_code code = TREE_CODE (exp);
2202
2203   if (TREE_CONSTANT (exp) || code == SAVE_EXPR || code == NULL_EXPR)
2204     return exp;
2205
2206   if (code == UNCONSTRAINED_ARRAY_REF)
2207     {
2208       tree t = build1 (code, type, gnat_save_expr (TREE_OPERAND (exp, 0)));
2209       TREE_READONLY (t) = TYPE_READONLY (type);
2210       return t;
2211     }
2212
2213   /* If this is a COMPONENT_REF of a fat pointer, save the entire fat pointer.
2214      This may be more efficient, but will also allow us to more easily find
2215      the match for the PLACEHOLDER_EXPR.  */
2216   if (code == COMPONENT_REF
2217       && TYPE_IS_FAT_POINTER_P (TREE_TYPE (TREE_OPERAND (exp, 0))))
2218     return build3 (code, type, gnat_save_expr (TREE_OPERAND (exp, 0)),
2219                    TREE_OPERAND (exp, 1), TREE_OPERAND (exp, 2));
2220
2221   return save_expr (exp);
2222 }
2223
2224 /* Protect EXP for immediate reuse.  This is a variant of gnat_save_expr that
2225    is optimized under the assumption that EXP's value doesn't change before
2226    its subsequent reuse(s) except through its potential reevaluation.  */
2227
2228 tree
2229 gnat_protect_expr (tree exp)
2230 {
2231   tree type = TREE_TYPE (exp);
2232   enum tree_code code = TREE_CODE (exp);
2233
2234   if (TREE_CONSTANT (exp) || code == SAVE_EXPR || code == NULL_EXPR)
2235     return exp;
2236
2237   /* If EXP has no side effects, we theoritically don't need to do anything.
2238      However, we may be recursively passed more and more complex expressions
2239      involving checks which will be reused multiple times and eventually be
2240      unshared for gimplification; in order to avoid a complexity explosion
2241      at that point, we protect any expressions more complex than a simple
2242      arithmetic expression.  */
2243   if (!TREE_SIDE_EFFECTS (exp))
2244     {
2245       tree inner = skip_simple_arithmetic (exp);
2246       if (!EXPR_P (inner) || REFERENCE_CLASS_P (inner))
2247         return exp;
2248     }
2249
2250   /* If this is a conversion, protect what's inside the conversion.  */
2251   if (code == NON_LVALUE_EXPR
2252       || CONVERT_EXPR_CODE_P (code)
2253       || code == VIEW_CONVERT_EXPR)
2254   return build1 (code, type, gnat_protect_expr (TREE_OPERAND (exp, 0)));
2255
2256   /* If we're indirectly referencing something, we only need to protect the
2257      address since the data itself can't change in these situations.  */
2258   if (code == INDIRECT_REF || code == UNCONSTRAINED_ARRAY_REF)
2259     {
2260       tree t = build1 (code, type, gnat_protect_expr (TREE_OPERAND (exp, 0)));
2261       TREE_READONLY (t) = TYPE_READONLY (type);
2262       return t;
2263     }
2264
2265   /* If this is a COMPONENT_REF of a fat pointer, save the entire fat pointer.
2266      This may be more efficient, but will also allow us to more easily find
2267      the match for the PLACEHOLDER_EXPR.  */
2268   if (code == COMPONENT_REF
2269       && TYPE_IS_FAT_POINTER_P (TREE_TYPE (TREE_OPERAND (exp, 0))))
2270     return build3 (code, type, gnat_protect_expr (TREE_OPERAND (exp, 0)),
2271                    TREE_OPERAND (exp, 1), TREE_OPERAND (exp, 2));
2272
2273   /* If this is a fat pointer or something that can be placed in a register,
2274      just make a SAVE_EXPR.  Likewise for a CALL_EXPR as large objects are
2275      returned via invisible reference in most ABIs so the temporary will
2276      directly be filled by the callee.  */
2277   if (TYPE_IS_FAT_POINTER_P (type)
2278       || TYPE_MODE (type) != BLKmode
2279       || code == CALL_EXPR)
2280     return save_expr (exp);
2281
2282   /* Otherwise reference, protect the address and dereference.  */
2283   return
2284     build_unary_op (INDIRECT_REF, type,
2285                     save_expr (build_unary_op (ADDR_EXPR,
2286                                                build_reference_type (type),
2287                                                exp)));
2288 }
2289
2290 /* This is equivalent to stabilize_reference_1 in tree.c but we take an extra
2291    argument to force evaluation of everything.  */
2292
2293 static tree
2294 gnat_stabilize_reference_1 (tree e, bool force)
2295 {
2296   enum tree_code code = TREE_CODE (e);
2297   tree type = TREE_TYPE (e);
2298   tree result;
2299
2300   /* We cannot ignore const expressions because it might be a reference
2301      to a const array but whose index contains side-effects.  But we can
2302      ignore things that are actual constant or that already have been
2303      handled by this function.  */
2304   if (TREE_CONSTANT (e) || code == SAVE_EXPR)
2305     return e;
2306
2307   switch (TREE_CODE_CLASS (code))
2308     {
2309     case tcc_exceptional:
2310     case tcc_declaration:
2311     case tcc_comparison:
2312     case tcc_expression:
2313     case tcc_reference:
2314     case tcc_vl_exp:
2315       /* If this is a COMPONENT_REF of a fat pointer, save the entire
2316          fat pointer.  This may be more efficient, but will also allow
2317          us to more easily find the match for the PLACEHOLDER_EXPR.  */
2318       if (code == COMPONENT_REF
2319           && TYPE_IS_FAT_POINTER_P (TREE_TYPE (TREE_OPERAND (e, 0))))
2320         result
2321           = build3 (code, type,
2322                     gnat_stabilize_reference_1 (TREE_OPERAND (e, 0), force),
2323                     TREE_OPERAND (e, 1), TREE_OPERAND (e, 2));
2324       /* If the expression has side-effects, then encase it in a SAVE_EXPR
2325          so that it will only be evaluated once.  */
2326       /* The tcc_reference and tcc_comparison classes could be handled as
2327          below, but it is generally faster to only evaluate them once.  */
2328       else if (TREE_SIDE_EFFECTS (e) || force)
2329         return save_expr (e);
2330       else
2331         return e;
2332       break;
2333
2334     case tcc_binary:
2335       /* Recursively stabilize each operand.  */
2336       result
2337         = build2 (code, type,
2338                   gnat_stabilize_reference_1 (TREE_OPERAND (e, 0), force),
2339                   gnat_stabilize_reference_1 (TREE_OPERAND (e, 1), force));
2340       break;
2341
2342     case tcc_unary:
2343       /* Recursively stabilize each operand.  */
2344       result
2345         = build1 (code, type,
2346                   gnat_stabilize_reference_1 (TREE_OPERAND (e, 0), force));
2347       break;
2348
2349     default:
2350       gcc_unreachable ();
2351     }
2352
2353   /* See similar handling in gnat_stabilize_reference.  */
2354   TREE_READONLY (result) = TREE_READONLY (e);
2355   TREE_SIDE_EFFECTS (result) |= TREE_SIDE_EFFECTS (e);
2356   TREE_THIS_VOLATILE (result) = TREE_THIS_VOLATILE (e);
2357
2358   return result;
2359 }
2360
2361 /* This is equivalent to stabilize_reference in tree.c but we know how to
2362    handle our own nodes and we take extra arguments.  FORCE says whether to
2363    force evaluation of everything.  We set SUCCESS to true unless we walk
2364    through something we don't know how to stabilize.  */
2365
2366 tree
2367 gnat_stabilize_reference (tree ref, bool force, bool *success)
2368 {
2369   tree type = TREE_TYPE (ref);
2370   enum tree_code code = TREE_CODE (ref);
2371   tree result;
2372
2373   /* Assume we'll success unless proven otherwise.  */
2374   if (success)
2375     *success = true;
2376
2377   switch (code)
2378     {
2379     case CONST_DECL:
2380     case VAR_DECL:
2381     case PARM_DECL:
2382     case RESULT_DECL:
2383       /* No action is needed in this case.  */
2384       return ref;
2385
2386     case ADDR_EXPR:
2387     CASE_CONVERT:
2388     case FLOAT_EXPR:
2389     case FIX_TRUNC_EXPR:
2390     case VIEW_CONVERT_EXPR:
2391       result
2392         = build1 (code, type,
2393                   gnat_stabilize_reference (TREE_OPERAND (ref, 0), force,
2394                                             success));
2395       break;
2396
2397     case INDIRECT_REF:
2398     case UNCONSTRAINED_ARRAY_REF:
2399       result = build1 (code, type,
2400                        gnat_stabilize_reference_1 (TREE_OPERAND (ref, 0),
2401                                                    force));
2402       break;
2403
2404     case COMPONENT_REF:
2405      result = build3 (COMPONENT_REF, type,
2406                       gnat_stabilize_reference (TREE_OPERAND (ref, 0), force,
2407                                                 success),
2408                       TREE_OPERAND (ref, 1), NULL_TREE);
2409       break;
2410
2411     case BIT_FIELD_REF:
2412       result = build3 (BIT_FIELD_REF, type,
2413                        gnat_stabilize_reference (TREE_OPERAND (ref, 0), force,
2414                                                  success),
2415                        gnat_stabilize_reference_1 (TREE_OPERAND (ref, 1),
2416                                                    force),
2417                        gnat_stabilize_reference_1 (TREE_OPERAND (ref, 2),
2418                                                    force));
2419       break;
2420
2421     case ARRAY_REF:
2422     case ARRAY_RANGE_REF:
2423       result = build4 (code, type,
2424                        gnat_stabilize_reference (TREE_OPERAND (ref, 0), force,
2425                                                  success),
2426                        gnat_stabilize_reference_1 (TREE_OPERAND (ref, 1),
2427                                                    force),
2428                        NULL_TREE, NULL_TREE);
2429       break;
2430
2431     case CALL_EXPR:
2432       result = gnat_stabilize_reference_1 (ref, force);
2433       break;
2434
2435     case COMPOUND_EXPR:
2436       result = build2 (COMPOUND_EXPR, type,
2437                        gnat_stabilize_reference (TREE_OPERAND (ref, 0), force,
2438                                                  success),
2439                        gnat_stabilize_reference_1 (TREE_OPERAND (ref, 1),
2440                                                    force));
2441       break;
2442
2443     case CONSTRUCTOR:
2444       /* Constructors with 1 element are used extensively to formally
2445          convert objects to special wrapping types.  */
2446       if (TREE_CODE (type) == RECORD_TYPE
2447           && VEC_length (constructor_elt, CONSTRUCTOR_ELTS (ref)) == 1)
2448         {
2449           tree index
2450             = VEC_index (constructor_elt, CONSTRUCTOR_ELTS (ref), 0)->index;
2451           tree value
2452             = VEC_index (constructor_elt, CONSTRUCTOR_ELTS (ref), 0)->value;
2453           result
2454             = build_constructor_single (type, index,
2455                                         gnat_stabilize_reference_1 (value,
2456                                                                     force));
2457         }
2458       else
2459         {
2460           if (success)
2461             *success = false;
2462           return ref;
2463         }
2464       break;
2465
2466     case ERROR_MARK:
2467       ref = error_mark_node;
2468
2469       /* ...  fall through to failure ... */
2470
2471       /* If arg isn't a kind of lvalue we recognize, make no change.
2472          Caller should recognize the error for an invalid lvalue.  */
2473     default:
2474       if (success)
2475         *success = false;
2476       return ref;
2477     }
2478
2479   /* TREE_THIS_VOLATILE and TREE_SIDE_EFFECTS set on the initial expression
2480      may not be sustained across some paths, such as the way via build1 for
2481      INDIRECT_REF.  We reset those flags here in the general case, which is
2482      consistent with the GCC version of this routine.
2483
2484      Special care should be taken regarding TREE_SIDE_EFFECTS, because some
2485      paths introduce side-effects where there was none initially (e.g. if a
2486      SAVE_EXPR is built) and we also want to keep track of that.  */
2487   TREE_READONLY (result) = TREE_READONLY (ref);
2488   TREE_SIDE_EFFECTS (result) |= TREE_SIDE_EFFECTS (ref);
2489   TREE_THIS_VOLATILE (result) = TREE_THIS_VOLATILE (ref);
2490
2491   return result;
2492 }