gcc/tree-object-size.c

   1 /* __builtin_object_size (ptr, object_size_type) computation
   2    Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010
   3    Free Software Foundation, Inc.
   4    Contributed by Jakub Jelinek <jakub@redhat.com>
   5
   6 This file is part of GCC.
   7
   8 GCC is free software; you can redistribute it and/or modify
   9 it under the terms of the GNU General Public License as published by
  10 the Free Software Foundation; either version 3, or (at your option)
  11 any later version.
  12
  13 GCC is distributed in the hope that it will be useful,
  14 but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 GNU General Public License for more details.
  17
  18 You should have received a copy of the GNU General Public License
  19 along with GCC; see the file COPYING3.  If not see
  20 <http://www.gnu.org/licenses/>.  */
  21
  22 #include "config.h"
  23 #include "system.h"
  24 #include "coretypes.h"
  25 #include "tm.h"
  26 #include "tree.h"
  27 #include "diagnostic-core.h"
  28 #include "toplev.h"
  29 #include "tree-pretty-print.h"
  30 #include "gimple-pretty-print.h"
  31 #include "tree-flow.h"
  32 #include "tree-pass.h"
  33 #include "tree-ssa-propagate.h"
  34
  35 struct object_size_info
  36 {
  37   int object_size_type;
  38   bitmap visited, reexamine;
  39   int pass;
  40   bool changed;
  41   unsigned int *depths;
  42   unsigned int *stack, *tos;
  43 };
  44
  45 static unsigned HOST_WIDE_INT unknown[4] = { -1, -1, 0, 0 };
  46
  47 static tree compute_object_offset (const_tree, const_tree);
  48 static unsigned HOST_WIDE_INT addr_object_size (struct object_size_info *,
  49                                                 const_tree, int);
  50 static unsigned HOST_WIDE_INT alloc_object_size (const_gimple, int);
  51 static tree pass_through_call (const_gimple);
  52 static void collect_object_sizes_for (struct object_size_info *, tree);
  53 static void expr_object_size (struct object_size_info *, tree, tree);
  54 static bool merge_object_sizes (struct object_size_info *, tree, tree,
  55                                 unsigned HOST_WIDE_INT);
  56 static bool plus_stmt_object_size (struct object_size_info *, tree, gimple);
  57 static bool cond_expr_object_size (struct object_size_info *, tree, tree);
  58 static unsigned int compute_object_sizes (void);
  59 static void init_offset_limit (void);
  60 static void check_for_plus_in_loops (struct object_size_info *, tree);
  61 static void check_for_plus_in_loops_1 (struct object_size_info *, tree,
  62                                        unsigned int);
  63
  64 /* object_sizes[0] is upper bound for number of bytes till the end of
  65    the object.
  66    object_sizes[1] is upper bound for number of bytes till the end of
  67    the subobject (innermost array or field with address taken).
  68    object_sizes[2] is lower bound for number of bytes till the end of
  69    the object and object_sizes[3] lower bound for subobject.  */
  70 static unsigned HOST_WIDE_INT *object_sizes[4];
  71
  72 /* Bitmaps what object sizes have been computed already.  */
  73 static bitmap computed[4];
  74
  75 /* Maximum value of offset we consider to be addition.  */
  76 static unsigned HOST_WIDE_INT offset_limit;
  77
  78
  79 /* Initialize OFFSET_LIMIT variable.  */
  80 static void
  81 init_offset_limit (void)
  82 {
  83   if (host_integerp (TYPE_MAX_VALUE (sizetype), 1))
  84     offset_limit = tree_low_cst (TYPE_MAX_VALUE (sizetype), 1);
  85   else
  86     offset_limit = -1;
  87   offset_limit /= 2;
  88 }
  89
  90
  91 /* Compute offset of EXPR within VAR.  Return error_mark_node
  92    if unknown.  */
  93
  94 static tree
  95 compute_object_offset (const_tree expr, const_tree var)
  96 {
  97   enum tree_code code = PLUS_EXPR;
  98   tree base, off, t;
  99
 100   if (expr == var)
 101     return size_zero_node;
 102
 103   switch (TREE_CODE (expr))
 104     {
 105     case COMPONENT_REF:
 106       base = compute_object_offset (TREE_OPERAND (expr, 0), var);
 107       if (base == error_mark_node)
 108         return base;
 109
 110       t = TREE_OPERAND (expr, 1);
 111       off = size_binop (PLUS_EXPR, DECL_FIELD_OFFSET (t),
 112                         size_int (tree_low_cst (DECL_FIELD_BIT_OFFSET (t), 1)
 113                                   / BITS_PER_UNIT));
 114       break;
 115
 116     case REALPART_EXPR:
 117     CASE_CONVERT:
 118     case VIEW_CONVERT_EXPR:
 119     case NON_LVALUE_EXPR:
 120       return compute_object_offset (TREE_OPERAND (expr, 0), var);
 121
 122     case IMAGPART_EXPR:
 123       base = compute_object_offset (TREE_OPERAND (expr, 0), var);
 124       if (base == error_mark_node)
 125         return base;
 126
 127       off = TYPE_SIZE_UNIT (TREE_TYPE (expr));
 128       break;
 129
 130     case ARRAY_REF:
 131       base = compute_object_offset (TREE_OPERAND (expr, 0), var);
 132       if (base == error_mark_node)
 133         return base;
 134
 135       t = TREE_OPERAND (expr, 1);
 136       if (TREE_CODE (t) == INTEGER_CST && tree_int_cst_sgn (t) < 0)
 137         {
 138           code = MINUS_EXPR;
 139           t = fold_build1 (NEGATE_EXPR, TREE_TYPE (t), t);
 140         }
 141       t = fold_convert (sizetype, t);
 142       off = size_binop (MULT_EXPR, TYPE_SIZE_UNIT (TREE_TYPE (expr)), t);
 143       break;
 144
 145     case MEM_REF:
 146       gcc_assert (TREE_CODE (TREE_OPERAND (expr, 0)) == ADDR_EXPR);
 147       return TREE_OPERAND (expr, 1);
 148
 149     default:
 150       return error_mark_node;
 151     }
 152
 153   return size_binop (code, base, off);
 154 }
 155
 156
 157 /* Compute __builtin_object_size for PTR, which is a ADDR_EXPR.
 158    OBJECT_SIZE_TYPE is the second argument from __builtin_object_size.
 159    If unknown, return unknown[object_size_type].  */
 160
 161 static unsigned HOST_WIDE_INT
 162 addr_object_size (struct object_size_info *osi, const_tree ptr,
 163                   int object_size_type)
 164 {
 165   tree pt_var, pt_var_size = NULL_TREE, var_size, bytes;
 166
 167   gcc_assert (TREE_CODE (ptr) == ADDR_EXPR);
 168
 169   pt_var = TREE_OPERAND (ptr, 0);
 170   if (REFERENCE_CLASS_P (pt_var))
 171     pt_var = get_base_address (pt_var);
 172
 173   if (pt_var
 174       && TREE_CODE (pt_var) == MEM_REF
 175       && TREE_CODE (TREE_OPERAND (pt_var, 0)) == SSA_NAME
 176       && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (pt_var, 0))))
 177     {
 178       unsigned HOST_WIDE_INT sz;
 179
 180       if (!osi || (object_size_type & 1) != 0)
 181         {
 182           sz = compute_builtin_object_size (TREE_OPERAND (pt_var, 0),
 183                                             object_size_type & ~1);
 184           if (host_integerp (TREE_OPERAND (pt_var, 1), 0))
 185             sz -= TREE_INT_CST_LOW (TREE_OPERAND (pt_var, 1));
 186           else
 187             sz = offset_limit;
 188         }
 189       else
 190         {
 191           tree var = TREE_OPERAND (pt_var, 0);
 192           if (osi->pass == 0)
 193             collect_object_sizes_for (osi, var);
 194           if (bitmap_bit_p (computed[object_size_type],
 195                             SSA_NAME_VERSION (var)))
 196             sz = object_sizes[object_size_type][SSA_NAME_VERSION (var)];
 197           else
 198             sz = unknown[object_size_type];
 199           if (host_integerp (TREE_OPERAND (pt_var, 1), 0))
 200             sz -= TREE_INT_CST_LOW (TREE_OPERAND (pt_var, 1));
 201           else
 202             sz = offset_limit;
 203         }
 204
 205       if (sz != unknown[object_size_type] && sz < offset_limit)
 206         pt_var_size = size_int (sz);
 207     }
 208   else if (pt_var
 209            && (SSA_VAR_P (pt_var) || TREE_CODE (pt_var) == STRING_CST)
 210            && TYPE_SIZE_UNIT (TREE_TYPE (pt_var))
 211            && host_integerp (TYPE_SIZE_UNIT (TREE_TYPE (pt_var)), 1)
 212            && (unsigned HOST_WIDE_INT)
 213               tree_low_cst (TYPE_SIZE_UNIT (TREE_TYPE (pt_var)), 1)
 214               < offset_limit)
 215     pt_var_size = TYPE_SIZE_UNIT (TREE_TYPE (pt_var));
 216   else
 217     return unknown[object_size_type];
 218
 219   if (pt_var != TREE_OPERAND (ptr, 0))
 220     {
 221       tree var;
 222
 223       if (object_size_type & 1)
 224         {
 225           var = TREE_OPERAND (ptr, 0);
 226
 227           while (var != pt_var
 228                  && TREE_CODE (var) != BIT_FIELD_REF
 229                  && TREE_CODE (var) != COMPONENT_REF
 230                  && TREE_CODE (var) != ARRAY_REF
 231                  && TREE_CODE (var) != ARRAY_RANGE_REF
 232                  && TREE_CODE (var) != REALPART_EXPR
 233                  && TREE_CODE (var) != IMAGPART_EXPR)
 234             var = TREE_OPERAND (var, 0);
 235           if (var != pt_var && TREE_CODE (var) == ARRAY_REF)
 236             var = TREE_OPERAND (var, 0);
 237           if (! TYPE_SIZE_UNIT (TREE_TYPE (var))
 238               || ! host_integerp (TYPE_SIZE_UNIT (TREE_TYPE (var)), 1)
 239               || (pt_var_size
 240                   && tree_int_cst_lt (pt_var_size,
 241                                       TYPE_SIZE_UNIT (TREE_TYPE (var)))))
 242             var = pt_var;
 243           else if (var != pt_var && TREE_CODE (pt_var) == MEM_REF)
 244             {
 245               tree v = var;
 246               /* For &X->fld, compute object size only if fld isn't the last
 247                  field, as struct { int i; char c[1]; } is often used instead
 248                  of flexible array member.  */
 249               while (v && v != pt_var)
 250                 switch (TREE_CODE (v))
 251                   {
 252                   case ARRAY_REF:
 253                     if (TYPE_SIZE_UNIT (TREE_TYPE (TREE_OPERAND (v, 0)))
 254                         && TREE_CODE (TREE_OPERAND (v, 1)) == INTEGER_CST)
 255                       {
 256                         tree domain
 257                           = TYPE_DOMAIN (TREE_TYPE (TREE_OPERAND (v, 0)));
 258                         if (domain
 259                             && TYPE_MAX_VALUE (domain)
 260                             && TREE_CODE (TYPE_MAX_VALUE (domain))
 261                                == INTEGER_CST
 262                             && tree_int_cst_lt (TREE_OPERAND (v, 1),
 263                                                 TYPE_MAX_VALUE (domain)))
 264                           {
 265                             v = NULL_TREE;
 266                             break;
 267                           }
 268                       }
 269                     v = TREE_OPERAND (v, 0);
 270                     break;
 271                   case REALPART_EXPR:
 272                   case IMAGPART_EXPR:
 273                     v = NULL_TREE;
 274                     break;
 275                   case COMPONENT_REF:
 276                     if (TREE_CODE (TREE_TYPE (v)) != ARRAY_TYPE)
 277                       {
 278                         v = NULL_TREE;
 279                         break;
 280                       }
 281                     while (v != pt_var && TREE_CODE (v) == COMPONENT_REF)
 282                       if (TREE_CODE (TREE_TYPE (TREE_OPERAND (v, 0)))
 283                           != UNION_TYPE
 284                           && TREE_CODE (TREE_TYPE (TREE_OPERAND (v, 0)))
 285                           != QUAL_UNION_TYPE)
 286                         break;
 287                       else
 288                         v = TREE_OPERAND (v, 0);
 289                     if (TREE_CODE (v) == COMPONENT_REF
 290                         && TREE_CODE (TREE_TYPE (TREE_OPERAND (v, 0)))
 291                            == RECORD_TYPE)
 292                       {
 293                         tree fld_chain = DECL_CHAIN (TREE_OPERAND (v, 1));
 294                         for (; fld_chain; fld_chain = DECL_CHAIN (fld_chain))
 295                           if (TREE_CODE (fld_chain) == FIELD_DECL)
 296                             break;
 297
 298                         if (fld_chain)
 299                           {
 300                             v = NULL_TREE;
 301                             break;
 302                           }
 303                         v = TREE_OPERAND (v, 0);
 304                       }
 305                     while (v != pt_var && TREE_CODE (v) == COMPONENT_REF)
 306                       if (TREE_CODE (TREE_TYPE (TREE_OPERAND (v, 0)))
 307                           != UNION_TYPE
 308                           && TREE_CODE (TREE_TYPE (TREE_OPERAND (v, 0)))
 309                           != QUAL_UNION_TYPE)
 310                         break;
 311                       else
 312                         v = TREE_OPERAND (v, 0);
 313                     if (v != pt_var)
 314                       v = NULL_TREE;
 315                     else
 316                       v = pt_var;
 317                     break;
 318                   default:
 319                     v = pt_var;
 320                     break;
 321                   }
 322               if (v == pt_var)
 323                 var = pt_var;
 324             }
 325         }
 326       else
 327         var = pt_var;
 328
 329       if (var != pt_var)
 330         var_size = TYPE_SIZE_UNIT (TREE_TYPE (var));
 331       else if (!pt_var_size)
 332         return unknown[object_size_type];
 333       else
 334         var_size = pt_var_size;
 335       bytes = compute_object_offset (TREE_OPERAND (ptr, 0), var);
 336       if (bytes != error_mark_node)
 337         {
 338           if (TREE_CODE (bytes) == INTEGER_CST
 339               && tree_int_cst_lt (var_size, bytes))
 340             bytes = size_zero_node;
 341           else
 342             bytes = size_binop (MINUS_EXPR, var_size, bytes);
 343         }
 344       if (var != pt_var
 345           && pt_var_size
 346           && TREE_CODE (pt_var) == MEM_REF
 347           && bytes != error_mark_node)
 348         {
 349           tree bytes2 = compute_object_offset (TREE_OPERAND (ptr, 0), pt_var);
 350           if (bytes2 != error_mark_node)
 351             {
 352               bytes2 = size_binop (PLUS_EXPR, bytes2,
 353                                    TREE_OPERAND (pt_var, 1));
 354               if (TREE_CODE (bytes2) == INTEGER_CST
 355                   && tree_int_cst_lt (pt_var_size, bytes2))
 356                 bytes2 = size_zero_node;
 357               else
 358                 bytes2 = size_binop (MINUS_EXPR, pt_var_size, bytes2);
 359               bytes = size_binop (MIN_EXPR, bytes, bytes2);
 360             }
 361         }
 362     }
 363   else if (!pt_var_size)
 364     return unknown[object_size_type];
 365   else
 366     bytes = pt_var_size;
 367
 368   if (host_integerp (bytes, 1))
 369     return tree_low_cst (bytes, 1);
 370
 371   return unknown[object_size_type];
 372 }
 373
 374
 375 /* Compute __builtin_object_size for CALL, which is a GIMPLE_CALL.
 376    Handles various allocation calls.  OBJECT_SIZE_TYPE is the second
 377    argument from __builtin_object_size.  If unknown, return
 378    unknown[object_size_type].  */
 379
 380 static unsigned HOST_WIDE_INT
 381 alloc_object_size (const_gimple call, int object_size_type)
 382 {
 383   tree callee, bytes = NULL_TREE;
 384   tree alloc_size;
 385   int arg1 = -1, arg2 = -1;
 386
 387   gcc_assert (is_gimple_call (call));
 388
 389   callee = gimple_call_fndecl (call);
 390   if (!callee)
 391     return unknown[object_size_type];
 392
 393   alloc_size = lookup_attribute ("alloc_size", TYPE_ATTRIBUTES (TREE_TYPE(callee)));
 394   if (alloc_size && TREE_VALUE (alloc_size))
 395     {
 396       tree p = TREE_VALUE (alloc_size);
 397
 398       arg1 = TREE_INT_CST_LOW (TREE_VALUE (p))-1;
 399       if (TREE_CHAIN (p))
 400         arg2 = TREE_INT_CST_LOW (TREE_VALUE (TREE_CHAIN (p)))-1;
 401     }
 402
 403   if (DECL_BUILT_IN_CLASS (callee) == BUILT_IN_NORMAL)
 404     switch (DECL_FUNCTION_CODE (callee))
 405       {
 406       case BUILT_IN_CALLOC:
 407         arg2 = 1;
 408         /* fall through */
 409       case BUILT_IN_MALLOC:
 410       case BUILT_IN_ALLOCA:
 411         arg1 = 0;
 412       default:
 413         break;
 414       }
 415
 416   if (arg1 < 0 || arg1 >= (int)gimple_call_num_args (call)
 417       || TREE_CODE (gimple_call_arg (call, arg1)) != INTEGER_CST
 418       || (arg2 >= 0
 419           && (arg2 >= (int)gimple_call_num_args (call)
 420               || TREE_CODE (gimple_call_arg (call, arg2)) != INTEGER_CST)))
 421     return unknown[object_size_type];
 422
 423   if (arg2 >= 0)
 424     bytes = size_binop (MULT_EXPR,
 425         fold_convert (sizetype, gimple_call_arg (call, arg1)),
 426         fold_convert (sizetype, gimple_call_arg (call, arg2)));
 427   else if (arg1 >= 0)
 428     bytes = fold_convert (sizetype, gimple_call_arg (call, arg1));
 429
 430   if (bytes && host_integerp (bytes, 1))
 431     return tree_low_cst (bytes, 1);
 432
 433   return unknown[object_size_type];
 434 }
 435
 436
 437 /* If object size is propagated from one of function's arguments directly
 438    to its return value, return that argument for GIMPLE_CALL statement CALL.
 439    Otherwise return NULL.  */
 440
 441 static tree
 442 pass_through_call (const_gimple call)
 443 {
 444   tree callee = gimple_call_fndecl (call);
 445
 446   if (callee
 447       && DECL_BUILT_IN_CLASS (callee) == BUILT_IN_NORMAL)
 448     switch (DECL_FUNCTION_CODE (callee))
 449       {
 450       case BUILT_IN_MEMCPY:
 451       case BUILT_IN_MEMMOVE:
 452       case BUILT_IN_MEMSET:
 453       case BUILT_IN_STRCPY:
 454       case BUILT_IN_STRNCPY:
 455       case BUILT_IN_STRCAT:
 456       case BUILT_IN_STRNCAT:
 457       case BUILT_IN_MEMCPY_CHK:
 458       case BUILT_IN_MEMMOVE_CHK:
 459       case BUILT_IN_MEMSET_CHK:
 460       case BUILT_IN_STRCPY_CHK:
 461       case BUILT_IN_STRNCPY_CHK:
 462       case BUILT_IN_STRCAT_CHK:
 463       case BUILT_IN_STRNCAT_CHK:
 464         if (gimple_call_num_args (call) >= 1)
 465           return gimple_call_arg (call, 0);
 466         break;
 467       default:
 468         break;
 469       }
 470
 471   return NULL_TREE;
 472 }
 473
 474
 475 /* Compute __builtin_object_size value for PTR.  OBJECT_SIZE_TYPE is the
 476    second argument from __builtin_object_size.  */
 477
 478 unsigned HOST_WIDE_INT
 479 compute_builtin_object_size (tree ptr, int object_size_type)
 480 {
 481   gcc_assert (object_size_type >= 0 && object_size_type <= 3);
 482
 483   if (! offset_limit)
 484     init_offset_limit ();
 485
 486   if (TREE_CODE (ptr) == ADDR_EXPR)
 487     return addr_object_size (NULL, ptr, object_size_type);
 488
 489   if (TREE_CODE (ptr) == SSA_NAME
 490       && POINTER_TYPE_P (TREE_TYPE (ptr))
 491       && object_sizes[object_size_type] != NULL)
 492     {
 493       if (!bitmap_bit_p (computed[object_size_type], SSA_NAME_VERSION (ptr)))
 494         {
 495           struct object_size_info osi;
 496           bitmap_iterator bi;
 497           unsigned int i;
 498
 499           if (dump_file)
 500             {
 501               fprintf (dump_file, "Computing %s %sobject size for ",
 502                        (object_size_type & 2) ? "minimum" : "maximum",
 503                        (object_size_type & 1) ? "sub" : "");
 504               print_generic_expr (dump_file, ptr, dump_flags);
 505               fprintf (dump_file, ":\n");
 506             }
 507
 508           osi.visited = BITMAP_ALLOC (NULL);
 509           osi.reexamine = BITMAP_ALLOC (NULL);
 510           osi.object_size_type = object_size_type;
 511           osi.depths = NULL;
 512           osi.stack = NULL;
 513           osi.tos = NULL;
 514
 515           /* First pass: walk UD chains, compute object sizes that
 516              can be computed.  osi.reexamine bitmap at the end will
 517              contain what variables were found in dependency cycles
 518              and therefore need to be reexamined.  */
 519           osi.pass = 0;
 520           osi.changed = false;
 521           collect_object_sizes_for (&osi, ptr);
 522
 523           /* Second pass: keep recomputing object sizes of variables
 524              that need reexamination, until no object sizes are
 525              increased or all object sizes are computed.  */
 526           if (! bitmap_empty_p (osi.reexamine))
 527             {
 528               bitmap reexamine = BITMAP_ALLOC (NULL);
 529
 530               /* If looking for minimum instead of maximum object size,
 531                  detect cases where a pointer is increased in a loop.
 532                  Although even without this detection pass 2 would eventually
 533                  terminate, it could take a long time.  If a pointer is
 534                  increasing this way, we need to assume 0 object size.
 535                  E.g. p = &buf[0]; while (cond) p = p + 4;  */
 536               if (object_size_type & 2)
 537                 {
 538                   osi.depths = XCNEWVEC (unsigned int, num_ssa_names);
 539                   osi.stack = XNEWVEC (unsigned int, num_ssa_names);
 540                   osi.tos = osi.stack;
 541                   osi.pass = 1;
 542                   /* collect_object_sizes_for is changing
 543                      osi.reexamine bitmap, so iterate over a copy.  */
 544                   bitmap_copy (reexamine, osi.reexamine);
 545                   EXECUTE_IF_SET_IN_BITMAP (reexamine, 0, i, bi)
 546                     if (bitmap_bit_p (osi.reexamine, i))
 547                       check_for_plus_in_loops (&osi, ssa_name (i));
 548
 549                   free (osi.depths);
 550                   osi.depths = NULL;
 551                   free (osi.stack);
 552                   osi.stack = NULL;
 553                   osi.tos = NULL;
 554                 }
 555
 556               do
 557                 {
 558                   osi.pass = 2;
 559                   osi.changed = false;
 560                   /* collect_object_sizes_for is changing
 561                      osi.reexamine bitmap, so iterate over a copy.  */
 562                   bitmap_copy (reexamine, osi.reexamine);
 563                   EXECUTE_IF_SET_IN_BITMAP (reexamine, 0, i, bi)
 564                     if (bitmap_bit_p (osi.reexamine, i))
 565                       {
 566                         collect_object_sizes_for (&osi, ssa_name (i));
 567                         if (dump_file && (dump_flags & TDF_DETAILS))
 568                           {
 569                             fprintf (dump_file, "Reexamining ");
 570                             print_generic_expr (dump_file, ssa_name (i),
 571                                                 dump_flags);
 572                             fprintf (dump_file, "\n");
 573                           }
 574                       }
 575                 }
 576               while (osi.changed);
 577
 578               BITMAP_FREE (reexamine);
 579             }
 580           EXECUTE_IF_SET_IN_BITMAP (osi.reexamine, 0, i, bi)
 581             bitmap_set_bit (computed[object_size_type], i);
 582
 583           /* Debugging dumps.  */
 584           if (dump_file)
 585             {
 586               EXECUTE_IF_SET_IN_BITMAP (osi.visited, 0, i, bi)
 587                 if (object_sizes[object_size_type][i]
 588                     != unknown[object_size_type])
 589                   {
 590                     print_generic_expr (dump_file, ssa_name (i),
 591                                         dump_flags);
 592                     fprintf (dump_file,
 593                              ": %s %sobject size "
 594                              HOST_WIDE_INT_PRINT_UNSIGNED "\n",
 595                              (object_size_type & 2) ? "minimum" : "maximum",
 596                              (object_size_type & 1) ? "sub" : "",
 597                              object_sizes[object_size_type][i]);
 598                   }
 599             }
 600
 601           BITMAP_FREE (osi.reexamine);
 602           BITMAP_FREE (osi.visited);
 603         }
 604
 605       return object_sizes[object_size_type][SSA_NAME_VERSION (ptr)];
 606     }
 607
 608   return unknown[object_size_type];
 609 }
 610
 611 /* Compute object_sizes for PTR, defined to VALUE, which is not an SSA_NAME.  */
 612
 613 static void
 614 expr_object_size (struct object_size_info *osi, tree ptr, tree value)
 615 {
 616   int object_size_type = osi->object_size_type;
 617   unsigned int varno = SSA_NAME_VERSION (ptr);
 618   unsigned HOST_WIDE_INT bytes;
 619
 620   gcc_assert (object_sizes[object_size_type][varno]
 621               != unknown[object_size_type]);
 622   gcc_assert (osi->pass == 0);
 623
 624   if (TREE_CODE (value) == WITH_SIZE_EXPR)
 625     value = TREE_OPERAND (value, 0);
 626
 627   /* Pointer variables should have been handled by merge_object_sizes.  */
 628   gcc_assert (TREE_CODE (value) != SSA_NAME
 629               || !POINTER_TYPE_P (TREE_TYPE (value)));
 630
 631   if (TREE_CODE (value) == ADDR_EXPR)
 632     bytes = addr_object_size (osi, value, object_size_type);
 633   else
 634     bytes = unknown[object_size_type];
 635
 636   if ((object_size_type & 2) == 0)
 637     {
 638       if (object_sizes[object_size_type][varno] < bytes)
 639         object_sizes[object_size_type][varno] = bytes;
 640     }
 641   else
 642     {
 643       if (object_sizes[object_size_type][varno] > bytes)
 644         object_sizes[object_size_type][varno] = bytes;
 645     }
 646 }
 647
 648
 649 /* Compute object_sizes for PTR, defined to the result of a call.  */
 650
 651 static void
 652 call_object_size (struct object_size_info *osi, tree ptr, gimple call)
 653 {
 654   int object_size_type = osi->object_size_type;
 655   unsigned int varno = SSA_NAME_VERSION (ptr);
 656   unsigned HOST_WIDE_INT bytes;
 657
 658   gcc_assert (is_gimple_call (call));
 659
 660   gcc_assert (object_sizes[object_size_type][varno]
 661               != unknown[object_size_type]);
 662   gcc_assert (osi->pass == 0);
 663
 664   bytes = alloc_object_size (call, object_size_type);
 665
 666   if ((object_size_type & 2) == 0)
 667     {
 668       if (object_sizes[object_size_type][varno] < bytes)
 669         object_sizes[object_size_type][varno] = bytes;
 670     }
 671   else
 672     {
 673       if (object_sizes[object_size_type][varno] > bytes)
 674         object_sizes[object_size_type][varno] = bytes;
 675     }
 676 }
 677
 678
 679 /* Compute object_sizes for PTR, defined to an unknown value.  */
 680
 681 static void
 682 unknown_object_size (struct object_size_info *osi, tree ptr)
 683 {
 684   int object_size_type = osi->object_size_type;
 685   unsigned int varno = SSA_NAME_VERSION (ptr);
 686   unsigned HOST_WIDE_INT bytes;
 687
 688   gcc_assert (object_sizes[object_size_type][varno]
 689               != unknown[object_size_type]);
 690   gcc_assert (osi->pass == 0);
 691
 692   bytes = unknown[object_size_type];
 693
 694   if ((object_size_type & 2) == 0)
 695     {
 696       if (object_sizes[object_size_type][varno] < bytes)
 697         object_sizes[object_size_type][varno] = bytes;
 698     }
 699   else
 700     {
 701       if (object_sizes[object_size_type][varno] > bytes)
 702         object_sizes[object_size_type][varno] = bytes;
 703     }
 704 }
 705
 706
 707 /* Merge object sizes of ORIG + OFFSET into DEST.  Return true if
 708    the object size might need reexamination later.  */
 709
 710 static bool
 711 merge_object_sizes (struct object_size_info *osi, tree dest, tree orig,
 712                     unsigned HOST_WIDE_INT offset)
 713 {
 714   int object_size_type = osi->object_size_type;
 715   unsigned int varno = SSA_NAME_VERSION (dest);
 716   unsigned HOST_WIDE_INT orig_bytes;
 717
 718   if (object_sizes[object_size_type][varno] == unknown[object_size_type])
 719     return false;
 720   if (offset >= offset_limit)
 721     {
 722       object_sizes[object_size_type][varno] = unknown[object_size_type];
 723       return false;
 724     }
 725
 726   if (osi->pass == 0)
 727     collect_object_sizes_for (osi, orig);
 728
 729   orig_bytes = object_sizes[object_size_type][SSA_NAME_VERSION (orig)];
 730   if (orig_bytes != unknown[object_size_type])
 731     orig_bytes = (offset > orig_bytes)
 732                  ? (unsigned HOST_WIDE_INT) 0 : orig_bytes - offset;
 733
 734   if ((object_size_type & 2) == 0)
 735     {
 736       if (object_sizes[object_size_type][varno] < orig_bytes)
 737         {
 738           object_sizes[object_size_type][varno] = orig_bytes;
 739           osi->changed = true;
 740         }
 741     }
 742   else
 743     {
 744       if (object_sizes[object_size_type][varno] > orig_bytes)
 745         {
 746           object_sizes[object_size_type][varno] = orig_bytes;
 747           osi->changed = true;
 748         }
 749     }
 750   return bitmap_bit_p (osi->reexamine, SSA_NAME_VERSION (orig));
 751 }
 752
 753
 754 /* Compute object_sizes for VAR, defined to the result of an assignment
 755    with operator POINTER_PLUS_EXPR.  Return true if the object size might
 756    need reexamination  later.  */
 757
 758 static bool
 759 plus_stmt_object_size (struct object_size_info *osi, tree var, gimple stmt)
 760 {
 761   int object_size_type = osi->object_size_type;
 762   unsigned int varno = SSA_NAME_VERSION (var);
 763   unsigned HOST_WIDE_INT bytes;
 764   tree op0, op1;
 765
 766   if (gimple_assign_rhs_code (stmt) == POINTER_PLUS_EXPR)
 767     {
 768       op0 = gimple_assign_rhs1 (stmt);
 769       op1 = gimple_assign_rhs2 (stmt);
 770     }
 771   else if (gimple_assign_rhs_code (stmt) == ADDR_EXPR)
 772     {
 773       tree rhs = TREE_OPERAND (gimple_assign_rhs1 (stmt), 0);
 774       gcc_assert (TREE_CODE (rhs) == MEM_REF);
 775       op0 = TREE_OPERAND (rhs, 0);
 776       op1 = TREE_OPERAND (rhs, 1);
 777     }
 778   else
 779     gcc_unreachable ();
 780
 781   if (object_sizes[object_size_type][varno] == unknown[object_size_type])
 782     return false;
 783
 784   /* Handle PTR + OFFSET here.  */
 785   if (TREE_CODE (op1) == INTEGER_CST
 786       && (TREE_CODE (op0) == SSA_NAME
 787           || TREE_CODE (op0) == ADDR_EXPR))
 788     {
 789       if (! host_integerp (op1, 1))
 790         bytes = unknown[object_size_type];
 791       else if (TREE_CODE (op0) == SSA_NAME)
 792         return merge_object_sizes (osi, var, op0, tree_low_cst (op1, 1));
 793       else
 794         {
 795           unsigned HOST_WIDE_INT off = tree_low_cst (op1, 1);
 796
 797           /* op0 will be ADDR_EXPR here.  */
 798           bytes = addr_object_size (osi, op0, object_size_type);
 799           if (bytes == unknown[object_size_type])
 800             ;
 801           else if (off > offset_limit)
 802             bytes = unknown[object_size_type];
 803           else if (off > bytes)
 804             bytes = 0;
 805           else
 806             bytes -= off;
 807         }
 808     }
 809   else
 810     bytes = unknown[object_size_type];
 811
 812   if ((object_size_type & 2) == 0)
 813     {
 814       if (object_sizes[object_size_type][varno] < bytes)
 815         object_sizes[object_size_type][varno] = bytes;
 816     }
 817   else
 818     {
 819       if (object_sizes[object_size_type][varno] > bytes)
 820         object_sizes[object_size_type][varno] = bytes;
 821     }
 822   return false;
 823 }
 824
 825
 826 /* Compute object_sizes for VAR, defined to VALUE, which is
 827    a COND_EXPR.  Return true if the object size might need reexamination
 828    later.  */
 829
 830 static bool
 831 cond_expr_object_size (struct object_size_info *osi, tree var, tree value)
 832 {
 833   tree then_, else_;
 834   int object_size_type = osi->object_size_type;
 835   unsigned int varno = SSA_NAME_VERSION (var);
 836   bool reexamine = false;
 837
 838   gcc_assert (TREE_CODE (value) == COND_EXPR);
 839
 840   if (object_sizes[object_size_type][varno] == unknown[object_size_type])
 841     return false;
 842
 843   then_ = COND_EXPR_THEN (value);
 844   else_ = COND_EXPR_ELSE (value);
 845
 846   if (TREE_CODE (then_) == SSA_NAME)
 847     reexamine |= merge_object_sizes (osi, var, then_, 0);
 848   else
 849     expr_object_size (osi, var, then_);
 850
 851   if (TREE_CODE (else_) == SSA_NAME)
 852     reexamine |= merge_object_sizes (osi, var, else_, 0);
 853   else
 854     expr_object_size (osi, var, else_);
 855
 856   return reexamine;
 857 }
 858
 859 /* Compute object sizes for VAR.
 860    For ADDR_EXPR an object size is the number of remaining bytes
 861    to the end of the object (where what is considered an object depends on
 862    OSI->object_size_type).
 863    For allocation GIMPLE_CALL like malloc or calloc object size is the size
 864    of the allocation.
 865    For POINTER_PLUS_EXPR where second operand is a constant integer,
 866    object size is object size of the first operand minus the constant.
 867    If the constant is bigger than the number of remaining bytes until the
 868    end of the object, object size is 0, but if it is instead a pointer
 869    subtraction, object size is unknown[object_size_type].
 870    To differentiate addition from subtraction, ADDR_EXPR returns
 871    unknown[object_size_type] for all objects bigger than half of the address
 872    space, and constants less than half of the address space are considered
 873    addition, while bigger constants subtraction.
 874    For a memcpy like GIMPLE_CALL that always returns one of its arguments, the
 875    object size is object size of that argument.
 876    Otherwise, object size is the maximum of object sizes of variables
 877    that it might be set to.  */
 878
 879 static void
 880 collect_object_sizes_for (struct object_size_info *osi, tree var)
 881 {
 882   int object_size_type = osi->object_size_type;
 883   unsigned int varno = SSA_NAME_VERSION (var);
 884   gimple stmt;
 885   bool reexamine;
 886
 887   if (bitmap_bit_p (computed[object_size_type], varno))
 888     return;
 889
 890   if (osi->pass == 0)
 891     {
 892       if (bitmap_set_bit (osi->visited, varno))
 893         {
 894           object_sizes[object_size_type][varno]
 895             = (object_size_type & 2) ? -1 : 0;
 896         }
 897       else
 898         {
 899           /* Found a dependency loop.  Mark the variable for later
 900              re-examination.  */
 901           bitmap_set_bit (osi->reexamine, varno);
 902           if (dump_file && (dump_flags & TDF_DETAILS))
 903             {
 904               fprintf (dump_file, "Found a dependency loop at ");
 905               print_generic_expr (dump_file, var, dump_flags);
 906               fprintf (dump_file, "\n");
 907             }
 908           return;
 909         }
 910     }
 911
 912   if (dump_file && (dump_flags & TDF_DETAILS))
 913     {
 914       fprintf (dump_file, "Visiting use-def links for ");
 915       print_generic_expr (dump_file, var, dump_flags);
 916       fprintf (dump_file, "\n");
 917     }
 918
 919   stmt = SSA_NAME_DEF_STMT (var);
 920   reexamine = false;
 921
 922   switch (gimple_code (stmt))
 923     {
 924     case GIMPLE_ASSIGN:
 925       {
 926         tree rhs = gimple_assign_rhs1 (stmt);
 927         if (gimple_assign_rhs_code (stmt) == POINTER_PLUS_EXPR
 928             || (gimple_assign_rhs_code (stmt) == ADDR_EXPR
 929                 && TREE_CODE (TREE_OPERAND (rhs, 0)) == MEM_REF))
 930           reexamine = plus_stmt_object_size (osi, var, stmt);
 931         else if (gimple_assign_single_p (stmt)
 932                  || gimple_assign_unary_nop_p (stmt))
 933           {
 934             if (TREE_CODE (rhs) == SSA_NAME
 935                 && POINTER_TYPE_P (TREE_TYPE (rhs)))
 936               reexamine = merge_object_sizes (osi, var, rhs, 0);
 937             else if (TREE_CODE (rhs) == COND_EXPR)
 938               reexamine = cond_expr_object_size (osi, var, rhs);
 939             else
 940               expr_object_size (osi, var, rhs);
 941           }
 942         else
 943           unknown_object_size (osi, var);
 944         break;
 945       }
 946
 947     case GIMPLE_CALL:
 948       {
 949         tree arg = pass_through_call (stmt);
 950         if (arg)
 951           {
 952             if (TREE_CODE (arg) == SSA_NAME
 953                 && POINTER_TYPE_P (TREE_TYPE (arg)))
 954               reexamine = merge_object_sizes (osi, var, arg, 0);
 955             else if (TREE_CODE (arg) == COND_EXPR)
 956               reexamine = cond_expr_object_size (osi, var, arg);
 957             else
 958               expr_object_size (osi, var, arg);
 959           }
 960         else
 961           call_object_size (osi, var, stmt);
 962         break;
 963       }
 964
 965     case GIMPLE_ASM:
 966       /* Pointers defined by __asm__ statements can point anywhere.  */
 967       object_sizes[object_size_type][varno] = unknown[object_size_type];
 968       break;
 969
 970     case GIMPLE_NOP:
 971       {
 972         tree decl = SSA_NAME_VAR (var);
 973
 974         if (TREE_CODE (decl) != PARM_DECL && DECL_INITIAL (decl))
 975           expr_object_size (osi, var, DECL_INITIAL (decl));
 976         else
 977           expr_object_size (osi, var, decl);
 978       }
 979       break;
 980
 981     case GIMPLE_PHI:
 982       {
 983         unsigned i;
 984
 985         for (i = 0; i < gimple_phi_num_args (stmt); i++)
 986           {
 987             tree rhs = gimple_phi_arg (stmt, i)->def;
 988
 989             if (object_sizes[object_size_type][varno]
 990                 == unknown[object_size_type])
 991               break;
 992
 993             if (TREE_CODE (rhs) == SSA_NAME)
 994               reexamine |= merge_object_sizes (osi, var, rhs, 0);
 995             else if (osi->pass == 0)
 996               expr_object_size (osi, var, rhs);
 997           }
 998         break;
 999       }
1000
1001     default:
1002       gcc_unreachable ();
1003     }
1004
1005   if (! reexamine
1006       || object_sizes[object_size_type][varno] == unknown[object_size_type])
1007     {
1008       bitmap_set_bit (computed[object_size_type], varno);
1009       bitmap_clear_bit (osi->reexamine, varno);
1010     }
1011   else
1012     {
1013       bitmap_set_bit (osi->reexamine, varno);
1014       if (dump_file && (dump_flags & TDF_DETAILS))
1015         {
1016           fprintf (dump_file, "Need to reexamine ");
1017           print_generic_expr (dump_file, var, dump_flags);
1018           fprintf (dump_file, "\n");
1019         }
1020     }
1021 }
1022
1023
1024 /* Helper function for check_for_plus_in_loops.  Called recursively
1025    to detect loops.  */
1026
1027 static void
1028 check_for_plus_in_loops_1 (struct object_size_info *osi, tree var,
1029                            unsigned int depth)
1030 {
1031   gimple stmt = SSA_NAME_DEF_STMT (var);
1032   unsigned int varno = SSA_NAME_VERSION (var);
1033
1034   if (osi->depths[varno])
1035     {
1036       if (osi->depths[varno] != depth)
1037         {
1038           unsigned int *sp;
1039
1040           /* Found a loop involving pointer addition.  */
1041           for (sp = osi->tos; sp > osi->stack; )
1042             {
1043               --sp;
1044               bitmap_clear_bit (osi->reexamine, *sp);
1045               bitmap_set_bit (computed[osi->object_size_type], *sp);
1046               object_sizes[osi->object_size_type][*sp] = 0;
1047               if (*sp == varno)
1048                 break;
1049             }
1050         }
1051       return;
1052     }
1053   else if (! bitmap_bit_p (osi->reexamine, varno))
1054     return;
1055
1056   osi->depths[varno] = depth;
1057   *osi->tos++ = varno;
1058
1059   switch (gimple_code (stmt))
1060     {
1061
1062     case GIMPLE_ASSIGN:
1063       {
1064         if ((gimple_assign_single_p (stmt)
1065              || gimple_assign_unary_nop_p (stmt))
1066             && TREE_CODE (gimple_assign_rhs1 (stmt)) == SSA_NAME)
1067           {
1068             tree rhs = gimple_assign_rhs1 (stmt);
1069
1070             check_for_plus_in_loops_1 (osi, rhs, depth);
1071           }
1072         else if (gimple_assign_rhs_code (stmt) == POINTER_PLUS_EXPR)
1073           {
1074             tree basevar = gimple_assign_rhs1 (stmt);
1075             tree cst = gimple_assign_rhs2 (stmt);
1076
1077             gcc_assert (TREE_CODE (cst) == INTEGER_CST);
1078
1079             check_for_plus_in_loops_1 (osi, basevar,
1080                                        depth + !integer_zerop (cst));
1081           }
1082         else
1083           gcc_unreachable ();
1084         break;
1085       }
1086
1087     case GIMPLE_CALL:
1088       {
1089         tree arg = pass_through_call (stmt);
1090         if (arg)
1091           {
1092             if (TREE_CODE (arg) == SSA_NAME)
1093               check_for_plus_in_loops_1 (osi, arg, depth);
1094             else
1095               gcc_unreachable ();
1096           }
1097         break;
1098       }
1099
1100     case GIMPLE_PHI:
1101       {
1102         unsigned i;
1103
1104         for (i = 0; i < gimple_phi_num_args (stmt); i++)
1105           {
1106             tree rhs = gimple_phi_arg (stmt, i)->def;
1107
1108             if (TREE_CODE (rhs) == SSA_NAME)
1109               check_for_plus_in_loops_1 (osi, rhs, depth);
1110           }
1111         break;
1112       }
1113
1114     default:
1115       gcc_unreachable ();
1116     }
1117
1118   osi->depths[varno] = 0;
1119   osi->tos--;
1120 }
1121
1122
1123 /* Check if some pointer we are computing object size of is being increased
1124    within a loop.  If yes, assume all the SSA variables participating in
1125    that loop have minimum object sizes 0.  */
1126
1127 static void
1128 check_for_plus_in_loops (struct object_size_info *osi, tree var)
1129 {
1130   gimple stmt = SSA_NAME_DEF_STMT (var);
1131
1132   /* NOTE: In the pre-tuples code, we handled a CALL_EXPR here,
1133      and looked for a POINTER_PLUS_EXPR in the pass-through
1134      argument, if any.  In GIMPLE, however, such an expression
1135      is not a valid call operand.  */
1136
1137   if (is_gimple_assign (stmt)
1138       && gimple_assign_rhs_code (stmt) == POINTER_PLUS_EXPR)
1139     {
1140       tree basevar = gimple_assign_rhs1 (stmt);
1141       tree cst = gimple_assign_rhs2 (stmt);
1142
1143       gcc_assert (TREE_CODE (cst) == INTEGER_CST);
1144
1145       if (integer_zerop (cst))
1146         return;
1147
1148       osi->depths[SSA_NAME_VERSION (basevar)] = 1;
1149       *osi->tos++ = SSA_NAME_VERSION (basevar);
1150       check_for_plus_in_loops_1 (osi, var, 2);
1151       osi->depths[SSA_NAME_VERSION (basevar)] = 0;
1152       osi->tos--;
1153     }
1154 }
1155
1156
1157 /* Initialize data structures for the object size computation.  */
1158
1159 void
1160 init_object_sizes (void)
1161 {
1162   int object_size_type;
1163
1164   if (object_sizes[0])
1165     return;
1166
1167   for (object_size_type = 0; object_size_type <= 3; object_size_type++)
1168     {
1169       object_sizes[object_size_type] = XNEWVEC (unsigned HOST_WIDE_INT, num_ssa_names);
1170       computed[object_size_type] = BITMAP_ALLOC (NULL);
1171     }
1172
1173   init_offset_limit ();
1174 }
1175
1176
1177 /* Destroy data structures after the object size computation.  */
1178
1179 void
1180 fini_object_sizes (void)
1181 {
1182   int object_size_type;
1183
1184   for (object_size_type = 0; object_size_type <= 3; object_size_type++)
1185     {
1186       free (object_sizes[object_size_type]);
1187       BITMAP_FREE (computed[object_size_type]);
1188       object_sizes[object_size_type] = NULL;
1189     }
1190 }
1191
1192
1193 /* Simple pass to optimize all __builtin_object_size () builtins.  */
1194
1195 static unsigned int
1196 compute_object_sizes (void)
1197 {
1198   basic_block bb;
1199   FOR_EACH_BB (bb)
1200     {
1201       gimple_stmt_iterator i;
1202       for (i = gsi_start_bb (bb); !gsi_end_p (i); gsi_next (&i))
1203         {
1204           tree callee, result;
1205           gimple call = gsi_stmt (i);
1206
1207           if (gimple_code (call) != GIMPLE_CALL)
1208             continue;
1209
1210           callee = gimple_call_fndecl (call);
1211           if (!callee
1212               || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL
1213               || DECL_FUNCTION_CODE (callee) != BUILT_IN_OBJECT_SIZE)
1214             continue;
1215
1216           init_object_sizes ();
1217           result = fold_call_stmt (call, false);
1218           if (!result)
1219             {
1220               if (gimple_call_num_args (call) == 2
1221                   && POINTER_TYPE_P (TREE_TYPE (gimple_call_arg (call, 0))))
1222                 {
1223                   tree ost = gimple_call_arg (call, 1);
1224
1225                   if (host_integerp (ost, 1))
1226                     {
1227                       unsigned HOST_WIDE_INT object_size_type
1228                         = tree_low_cst (ost, 1);
1229
1230                       if (object_size_type < 2)
1231                         result = fold_convert (size_type_node,
1232                                                integer_minus_one_node);
1233                       else if (object_size_type < 4)
1234                         result = fold_convert (size_type_node,
1235                                                integer_zero_node);
1236                     }
1237                 }
1238
1239               if (!result)
1240                 continue;
1241             }
1242
1243           if (dump_file && (dump_flags & TDF_DETAILS))
1244             {
1245               fprintf (dump_file, "Simplified\n  ");
1246               print_gimple_stmt (dump_file, call, 0, dump_flags);
1247             }
1248
1249           if (!update_call_from_tree (&i, result))
1250             gcc_unreachable ();
1251
1252           /* NOTE: In the pre-tuples code, we called update_stmt here.  This is
1253              now handled by gsi_replace, called from update_call_from_tree.  */
1254
1255           if (dump_file && (dump_flags & TDF_DETAILS))
1256             {
1257               fprintf (dump_file, "to\n  ");
1258               print_gimple_stmt (dump_file, call, 0, dump_flags);
1259               fprintf (dump_file, "\n");
1260             }
1261         }
1262     }
1263
1264   fini_object_sizes ();
1265   return 0;
1266 }
1267
1268 struct gimple_opt_pass pass_object_sizes =
1269 {
1270  {
1271   GIMPLE_PASS,
1272   "objsz",                              /* name */
1273   NULL,                                 /* gate */
1274   compute_object_sizes,                 /* execute */
1275   NULL,                                 /* sub */
1276   NULL,                                 /* next */
1277   0,                                    /* static_pass_number */
1278   TV_NONE,                              /* tv_id */
1279   PROP_cfg | PROP_ssa,                  /* properties_required */
1280   0,                                    /* properties_provided */
1281   0,                                    /* properties_destroyed */
1282   0,                                    /* todo_flags_start */
1283   TODO_dump_func | TODO_verify_ssa      /* todo_flags_finish */
1284  }
1285 };