gcc/gimple-low.c

   1 /* Tree lowering pass.  Lowers GIMPLE into unstructured form.
   2
   3    Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify it under
   8 the terms of the GNU General Public License as published by the Free
   9 Software Foundation; either version 3, or (at your option) any later
  10 version.
  11
  12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15 for more details.
  16
  17 You should have received a copy of the GNU General Public License
  18 along with GCC; see the file COPYING3.  If not see
  19 <http://www.gnu.org/licenses/>.  */
  20
  21 #include "config.h"
  22 #include "system.h"
  23 #include "coretypes.h"
  24 #include "tm.h"
  25 #include "tree.h"
  26 #include "rtl.h"
  27 #include "varray.h"
  28 #include "tree-gimple.h"
  29 #include "tree-inline.h"
  30 #include "diagnostic.h"
  31 #include "langhooks.h"
  32 #include "langhooks-def.h"
  33 #include "tree-flow.h"
  34 #include "timevar.h"
  35 #include "except.h"
  36 #include "hashtab.h"
  37 #include "flags.h"
  38 #include "function.h"
  39 #include "expr.h"
  40 #include "toplev.h"
  41 #include "tree-pass.h"
  42
  43 struct lower_data
  44 {
  45   /* Block the current statement belongs to.  */
  46   tree block;
  47
  48   /* A TREE_LIST of label and return statements to be moved to the end
  49      of the function.  */
  50   tree return_statements;
  51
  52   /* True if the function calls __builtin_setjmp.  */
  53   bool calls_builtin_setjmp;
  54 };
  55
  56 static void lower_stmt (tree_stmt_iterator *, struct lower_data *);
  57 static void lower_bind_expr (tree_stmt_iterator *, struct lower_data *);
  58 static void lower_cond_expr (tree_stmt_iterator *, struct lower_data *);
  59 static void lower_return_expr (tree_stmt_iterator *, struct lower_data *);
  60 static void lower_builtin_setjmp (tree_stmt_iterator *);
  61
  62 /* Lower the body of current_function_decl.  */
  63
  64 static unsigned int
  65 lower_function_body (void)
  66 {
  67   struct lower_data data;
  68   tree *body_p = &DECL_SAVED_TREE (current_function_decl);
  69   tree bind = *body_p;
  70   tree_stmt_iterator i;
  71   tree t, x;
  72
  73   gcc_assert (TREE_CODE (bind) == BIND_EXPR);
  74
  75   memset (&data, 0, sizeof (data));
  76   data.block = DECL_INITIAL (current_function_decl);
  77   BLOCK_SUBBLOCKS (data.block) = NULL_TREE;
  78   BLOCK_CHAIN (data.block) = NULL_TREE;
  79   TREE_ASM_WRITTEN (data.block) = 1;
  80
  81   *body_p = alloc_stmt_list ();
  82   i = tsi_start (*body_p);
  83   tsi_link_after (&i, bind, TSI_NEW_STMT);
  84   lower_bind_expr (&i, &data);
  85
  86   i = tsi_last (*body_p);
  87
  88   /* If the function falls off the end, we need a null return statement.
  89      If we've already got one in the return_statements list, we don't
  90      need to do anything special.  Otherwise build one by hand.  */
  91   if (block_may_fallthru (*body_p)
  92       && (data.return_statements == NULL
  93           || TREE_OPERAND (TREE_VALUE (data.return_statements), 0) != NULL))
  94     {
  95       x = build1 (RETURN_EXPR, void_type_node, NULL);
  96       SET_EXPR_LOCATION (x, cfun->function_end_locus);
  97       tsi_link_after (&i, x, TSI_CONTINUE_LINKING);
  98     }
  99
 100   /* If we lowered any return statements, emit the representative
 101      at the end of the function.  */
 102   for (t = data.return_statements ; t ; t = TREE_CHAIN (t))
 103     {
 104       x = build1 (LABEL_EXPR, void_type_node, TREE_PURPOSE (t));
 105       tsi_link_after (&i, x, TSI_CONTINUE_LINKING);
 106
 107       /* Remove the line number from the representative return statement.
 108          It now fills in for many such returns.  Failure to remove this
 109          will result in incorrect results for coverage analysis.  */
 110       x = TREE_VALUE (t);
 111       SET_EXPR_LOCATION (x, UNKNOWN_LOCATION);
 112       tsi_link_after (&i, x, TSI_CONTINUE_LINKING);
 113     }
 114
 115   /* If the function calls __builtin_setjmp, we need to emit the computed
 116      goto that will serve as the unique dispatcher for all the receivers.  */
 117   if (data.calls_builtin_setjmp)
 118     {
 119       tree disp_label, disp_var, arg;
 120
 121       /* Build 'DISP_LABEL:' and insert.  */
 122       disp_label = create_artificial_label ();
 123       /* This mark will create forward edges from every call site.  */
 124       DECL_NONLOCAL (disp_label) = 1;
 125       cfun->has_nonlocal_label = 1;
 126       x = build1 (LABEL_EXPR, void_type_node, disp_label);
 127       tsi_link_after (&i, x, TSI_CONTINUE_LINKING);
 128
 129       /* Build 'DISP_VAR = __builtin_setjmp_dispatcher (DISP_LABEL);'
 130          and insert.  */
 131       disp_var = create_tmp_var (ptr_type_node, "setjmpvar");
 132       arg = build_addr (disp_label, current_function_decl);
 133       t = implicit_built_in_decls[BUILT_IN_SETJMP_DISPATCHER];
 134       t = build_call_expr (t, 1, arg);
 135       x = build_gimple_modify_stmt (disp_var, t);
 136
 137       /* Build 'goto DISP_VAR;' and insert.  */
 138       tsi_link_after (&i, x, TSI_CONTINUE_LINKING);
 139       x = build1 (GOTO_EXPR, void_type_node, disp_var);
 140       tsi_link_after (&i, x, TSI_CONTINUE_LINKING);
 141     }
 142
 143   gcc_assert (data.block == DECL_INITIAL (current_function_decl));
 144   BLOCK_SUBBLOCKS (data.block)
 145     = blocks_nreverse (BLOCK_SUBBLOCKS (data.block));
 146
 147   clear_block_marks (data.block);
 148   return 0;
 149 }
 150
 151 struct gimple_opt_pass pass_lower_cf =
 152 {
 153  {
 154   GIMPLE_PASS,
 155   "lower",                              /* name */
 156   NULL,                                 /* gate */
 157   lower_function_body,                  /* execute */
 158   NULL,                                 /* sub */
 159   NULL,                                 /* next */
 160   0,                                    /* static_pass_number */
 161   0,                                    /* tv_id */
 162   PROP_gimple_any,                      /* properties_required */
 163   PROP_gimple_lcf,                      /* properties_provided */
 164   0,                                    /* properties_destroyed */
 165   0,                                    /* todo_flags_start */
 166   TODO_dump_func                        /* todo_flags_finish */
 167  }
 168 };
 169
 170
 171 /* Lower the EXPR.  Unlike gimplification the statements are not relowered
 172    when they are changed -- if this has to be done, the lowering routine must
 173    do it explicitly.  DATA is passed through the recursion.  */
 174
 175 static void
 176 lower_stmt_body (tree expr, struct lower_data *data)
 177 {
 178   tree_stmt_iterator tsi;
 179
 180   for (tsi = tsi_start (expr); !tsi_end_p (tsi); )
 181     lower_stmt (&tsi, data);
 182 }
 183
 184
 185 /* Lower the OpenMP directive statement pointed by TSI.  DATA is
 186    passed through the recursion.  */
 187
 188 static void
 189 lower_omp_directive (tree_stmt_iterator *tsi, struct lower_data *data)
 190 {
 191   tree stmt;
 192
 193   stmt = tsi_stmt (*tsi);
 194
 195   lower_stmt_body (OMP_BODY (stmt), data);
 196   tsi_link_before (tsi, stmt, TSI_SAME_STMT);
 197   tsi_link_before (tsi, OMP_BODY (stmt), TSI_SAME_STMT);
 198   OMP_BODY (stmt) = NULL_TREE;
 199   tsi_delink (tsi);
 200 }
 201
 202
 203 /* Lower statement TSI.  DATA is passed through the recursion.  */
 204
 205 static void
 206 lower_stmt (tree_stmt_iterator *tsi, struct lower_data *data)
 207 {
 208   tree stmt = tsi_stmt (*tsi);
 209
 210   if (EXPR_HAS_LOCATION (stmt) && data)
 211     TREE_BLOCK (stmt) = data->block;
 212
 213   switch (TREE_CODE (stmt))
 214     {
 215     case BIND_EXPR:
 216       lower_bind_expr (tsi, data);
 217       return;
 218     case COND_EXPR:
 219       lower_cond_expr (tsi, data);
 220       return;
 221     case RETURN_EXPR:
 222       lower_return_expr (tsi, data);
 223       return;
 224
 225     case TRY_FINALLY_EXPR:
 226     case TRY_CATCH_EXPR:
 227       lower_stmt_body (TREE_OPERAND (stmt, 0), data);
 228       lower_stmt_body (TREE_OPERAND (stmt, 1), data);
 229       break;
 230     case CATCH_EXPR:
 231       lower_stmt_body (CATCH_BODY (stmt), data);
 232       break;
 233     case EH_FILTER_EXPR:
 234       lower_stmt_body (EH_FILTER_FAILURE (stmt), data);
 235       break;
 236
 237     case NOP_EXPR:
 238     case ASM_EXPR:
 239     case GOTO_EXPR:
 240     case PREDICT_EXPR:
 241     case LABEL_EXPR:
 242     case SWITCH_EXPR:
 243     case CHANGE_DYNAMIC_TYPE_EXPR:
 244     case OMP_FOR:
 245     case OMP_SECTIONS:
 246     case OMP_SECTIONS_SWITCH:
 247     case OMP_SECTION:
 248     case OMP_SINGLE:
 249     case OMP_MASTER:
 250     case OMP_ORDERED:
 251     case OMP_CRITICAL:
 252     case OMP_RETURN:
 253     case OMP_ATOMIC_LOAD:
 254     case OMP_ATOMIC_STORE:
 255     case OMP_CONTINUE:
 256       break;
 257
 258     case GIMPLE_MODIFY_STMT:
 259       if (TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1)) == CALL_EXPR)
 260         stmt = GIMPLE_STMT_OPERAND (stmt, 1);
 261       else
 262         break;
 263       /* FALLTHRU */
 264
 265     case CALL_EXPR:
 266       {
 267         tree decl = get_callee_fndecl (stmt);
 268         if (decl
 269             && DECL_BUILT_IN_CLASS (decl) == BUILT_IN_NORMAL
 270             && DECL_FUNCTION_CODE (decl) == BUILT_IN_SETJMP)
 271           {
 272             data->calls_builtin_setjmp = true;
 273             lower_builtin_setjmp (tsi);
 274             return;
 275           }
 276       }
 277       break;
 278
 279     case OMP_PARALLEL:
 280       lower_omp_directive (tsi, data);
 281       return;
 282
 283     default:
 284       gcc_unreachable ();
 285     }
 286
 287   tsi_next (tsi);
 288 }
 289
 290 /* Lower a bind_expr TSI.  DATA is passed through the recursion.  */
 291
 292 static void
 293 lower_bind_expr (tree_stmt_iterator *tsi, struct lower_data *data)
 294 {
 295   tree old_block = data->block;
 296   tree stmt = tsi_stmt (*tsi);
 297   tree new_block = BIND_EXPR_BLOCK (stmt);
 298
 299   if (new_block)
 300     {
 301       if (new_block == old_block)
 302         {
 303           /* The outermost block of the original function may not be the
 304              outermost statement chain of the gimplified function.  So we
 305              may see the outermost block just inside the function.  */
 306           gcc_assert (new_block == DECL_INITIAL (current_function_decl));
 307           new_block = NULL;
 308         }
 309       else
 310         {
 311           /* We do not expect to handle duplicate blocks.  */
 312           gcc_assert (!TREE_ASM_WRITTEN (new_block));
 313           TREE_ASM_WRITTEN (new_block) = 1;
 314
 315           /* Block tree may get clobbered by inlining.  Normally this would
 316              be fixed in rest_of_decl_compilation using block notes, but
 317              since we are not going to emit them, it is up to us.  */
 318           BLOCK_CHAIN (new_block) = BLOCK_SUBBLOCKS (old_block);
 319           BLOCK_SUBBLOCKS (old_block) = new_block;
 320           BLOCK_SUBBLOCKS (new_block) = NULL_TREE;
 321           BLOCK_SUPERCONTEXT (new_block) = old_block;
 322
 323           data->block = new_block;
 324         }
 325     }
 326
 327   record_vars (BIND_EXPR_VARS (stmt));
 328   lower_stmt_body (BIND_EXPR_BODY (stmt), data);
 329
 330   if (new_block)
 331     {
 332       gcc_assert (data->block == new_block);
 333
 334       BLOCK_SUBBLOCKS (new_block)
 335         = blocks_nreverse (BLOCK_SUBBLOCKS (new_block));
 336       data->block = old_block;
 337     }
 338
 339   /* The BIND_EXPR no longer carries any useful information -- kill it.  */
 340   tsi_link_before (tsi, BIND_EXPR_BODY (stmt), TSI_SAME_STMT);
 341   tsi_delink (tsi);
 342 }
 343
 344 /* Try to determine whether a TRY_CATCH expression can fall through.
 345    This is a subroutine of block_may_fallthru.  */
 346
 347 static bool
 348 try_catch_may_fallthru (const_tree stmt)
 349 {
 350   tree_stmt_iterator i;
 351
 352   /* If the TRY block can fall through, the whole TRY_CATCH can
 353      fall through.  */
 354   if (block_may_fallthru (TREE_OPERAND (stmt, 0)))
 355     return true;
 356
 357   i = tsi_start (TREE_OPERAND (stmt, 1));
 358   switch (TREE_CODE (tsi_stmt (i)))
 359     {
 360     case CATCH_EXPR:
 361       /* We expect to see a sequence of CATCH_EXPR trees, each with a
 362          catch expression and a body.  The whole TRY_CATCH may fall
 363          through iff any of the catch bodies falls through.  */
 364       for (; !tsi_end_p (i); tsi_next (&i))
 365         {
 366           if (block_may_fallthru (CATCH_BODY (tsi_stmt (i))))
 367             return true;
 368         }
 369       return false;
 370
 371     case EH_FILTER_EXPR:
 372       /* The exception filter expression only matters if there is an
 373          exception.  If the exception does not match EH_FILTER_TYPES,
 374          we will execute EH_FILTER_FAILURE, and we will fall through
 375          if that falls through.  If the exception does match
 376          EH_FILTER_TYPES, the stack unwinder will continue up the
 377          stack, so we will not fall through.  We don't know whether we
 378          will throw an exception which matches EH_FILTER_TYPES or not,
 379          so we just ignore EH_FILTER_TYPES and assume that we might
 380          throw an exception which doesn't match.  */
 381       return block_may_fallthru (EH_FILTER_FAILURE (tsi_stmt (i)));
 382
 383     default:
 384       /* This case represents statements to be executed when an
 385          exception occurs.  Those statements are implicitly followed
 386          by a RESX_EXPR to resume execution after the exception.  So
 387          in this case the TRY_CATCH never falls through.  */
 388       return false;
 389     }
 390 }
 391
 392 /* Try to determine if we can fall out of the bottom of BLOCK.  This guess
 393    need not be 100% accurate; simply be conservative and return true if we
 394    don't know.  This is used only to avoid stupidly generating extra code.
 395    If we're wrong, we'll just delete the extra code later.  */
 396
 397 bool
 398 block_may_fallthru (const_tree block)
 399 {
 400   /* This CONST_CAST is okay because expr_last returns it's argument
 401      unmodified and we assign it to a const_tree.  */
 402   const_tree stmt = expr_last (CONST_CAST_TREE(block));
 403
 404   switch (stmt ? TREE_CODE (stmt) : ERROR_MARK)
 405     {
 406     case GOTO_EXPR:
 407     case RETURN_EXPR:
 408     case RESX_EXPR:
 409       /* Easy cases.  If the last statement of the block implies
 410          control transfer, then we can't fall through.  */
 411       return false;
 412
 413     case SWITCH_EXPR:
 414       /* If SWITCH_LABELS is set, this is lowered, and represents a
 415          branch to a selected label and hence can not fall through.
 416          Otherwise SWITCH_BODY is set, and the switch can fall
 417          through.  */
 418       return SWITCH_LABELS (stmt) == NULL_TREE;
 419
 420     case COND_EXPR:
 421       if (block_may_fallthru (COND_EXPR_THEN (stmt)))
 422         return true;
 423       return block_may_fallthru (COND_EXPR_ELSE (stmt));
 424
 425     case BIND_EXPR:
 426       return block_may_fallthru (BIND_EXPR_BODY (stmt));
 427
 428     case TRY_CATCH_EXPR:
 429       return try_catch_may_fallthru (stmt);
 430
 431     case TRY_FINALLY_EXPR:
 432       /* The finally clause is always executed after the try clause,
 433          so if it does not fall through, then the try-finally will not
 434          fall through.  Otherwise, if the try clause does not fall
 435          through, then when the finally clause falls through it will
 436          resume execution wherever the try clause was going.  So the
 437          whole try-finally will only fall through if both the try
 438          clause and the finally clause fall through.  */
 439       return (block_may_fallthru (TREE_OPERAND (stmt, 0))
 440               && block_may_fallthru (TREE_OPERAND (stmt, 1)));
 441
 442     case GIMPLE_MODIFY_STMT:
 443       if (TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1)) == CALL_EXPR)
 444         stmt = GIMPLE_STMT_OPERAND (stmt, 1);
 445       else
 446         return true;
 447       /* FALLTHRU */
 448
 449     case CALL_EXPR:
 450       /* Functions that do not return do not fall through.  */
 451       return (call_expr_flags (stmt) & ECF_NORETURN) == 0;
 452
 453     case CLEANUP_POINT_EXPR:
 454       return block_may_fallthru (TREE_OPERAND (stmt, 0));
 455
 456     default:
 457       return true;
 458     }
 459 }
 460
 461 /* Lower a cond_expr TSI.  DATA is passed through the recursion.  */
 462
 463 static void
 464 lower_cond_expr (tree_stmt_iterator *tsi, struct lower_data *data)
 465 {
 466   tree stmt = tsi_stmt (*tsi);
 467   bool then_is_goto, else_is_goto;
 468   tree then_branch, else_branch;
 469   tree then_goto, else_goto;
 470
 471   then_branch = COND_EXPR_THEN (stmt);
 472   else_branch = COND_EXPR_ELSE (stmt);
 473
 474   lower_stmt_body (then_branch, data);
 475   lower_stmt_body (else_branch, data);
 476
 477   then_goto = expr_only (then_branch);
 478   then_is_goto = then_goto && simple_goto_p (then_goto);
 479
 480   else_goto = expr_only (else_branch);
 481   else_is_goto = else_goto && simple_goto_p (else_goto);
 482
 483   if (!then_is_goto || !else_is_goto)
 484     {
 485       tree then_label, else_label, end_label, t;
 486
 487       then_label = NULL_TREE;
 488       else_label = NULL_TREE;
 489       end_label = NULL_TREE;
 490
 491       /* Replace the cond_expr with explicit gotos.  */
 492       if (!then_is_goto)
 493         {
 494           t = build1 (LABEL_EXPR, void_type_node, NULL_TREE);
 495           if (TREE_SIDE_EFFECTS (then_branch))
 496             then_label = t;
 497           else
 498             end_label = t;
 499           then_goto = build_and_jump (&LABEL_EXPR_LABEL (t));
 500         }
 501
 502       if (!else_is_goto)
 503         {
 504           t = build1 (LABEL_EXPR, void_type_node, NULL_TREE);
 505           if (TREE_SIDE_EFFECTS (else_branch))
 506             else_label = t;
 507           else
 508             {
 509               /* Both THEN and ELSE can be no-ops if one or both contained an
 510                  empty BIND_EXPR that was associated with the toplevel block
 511                  of an inlined function.  In that case remove_useless_stmts
 512                  can't have cleaned things up for us; kill the whole
 513                  conditional now.  */
 514               if (end_label)
 515                 {
 516                   tsi_delink (tsi);
 517                   return;
 518                 }
 519               else
 520                 end_label = t;
 521             }
 522           else_goto = build_and_jump (&LABEL_EXPR_LABEL (t));
 523         }
 524
 525       if (then_label)
 526         {
 527           bool may_fallthru = block_may_fallthru (then_branch);
 528
 529           tsi_link_after (tsi, then_label, TSI_CONTINUE_LINKING);
 530           tsi_link_after (tsi, then_branch, TSI_CONTINUE_LINKING);
 531
 532           if (else_label && may_fallthru)
 533             {
 534               end_label = build1 (LABEL_EXPR, void_type_node, NULL_TREE);
 535               t = build_and_jump (&LABEL_EXPR_LABEL (end_label));
 536               tsi_link_after (tsi, t, TSI_CONTINUE_LINKING);
 537             }
 538         }
 539
 540       if (else_label)
 541         {
 542           tsi_link_after (tsi, else_label, TSI_CONTINUE_LINKING);
 543           tsi_link_after (tsi, else_branch, TSI_CONTINUE_LINKING);
 544         }
 545
 546       if (end_label)
 547         tsi_link_after (tsi, end_label, TSI_CONTINUE_LINKING);
 548     }
 549
 550   COND_EXPR_THEN (stmt) = then_goto;
 551   COND_EXPR_ELSE (stmt) = else_goto;
 552
 553   tsi_next (tsi);
 554 }
 555
 556 /* Lower a return_expr TSI.  DATA is passed through the recursion.  */
 557
 558 static void
 559 lower_return_expr (tree_stmt_iterator *tsi, struct lower_data *data)
 560 {
 561   tree stmt = tsi_stmt (*tsi);
 562   tree value, t, label;
 563
 564   /* Extract the value being returned.  */
 565   value = TREE_OPERAND (stmt, 0);
 566   if (value && TREE_CODE (value) == GIMPLE_MODIFY_STMT)
 567     value = GIMPLE_STMT_OPERAND (value, 1);
 568
 569   /* Match this up with an existing return statement that's been created.  */
 570   for (t = data->return_statements; t ; t = TREE_CHAIN (t))
 571     {
 572       tree tvalue = TREE_OPERAND (TREE_VALUE (t), 0);
 573       if (tvalue && TREE_CODE (tvalue) == GIMPLE_MODIFY_STMT)
 574         tvalue = GIMPLE_STMT_OPERAND (tvalue, 1);
 575
 576       if (value == tvalue)
 577         {
 578           label = TREE_PURPOSE (t);
 579           goto found;
 580         }
 581     }
 582
 583   /* Not found.  Create a new label and record the return statement.  */
 584   label = create_artificial_label ();
 585   data->return_statements = tree_cons (label, stmt, data->return_statements);
 586
 587   /* Generate a goto statement and remove the return statement.  */
 588  found:
 589   t = build1 (GOTO_EXPR, void_type_node, label);
 590   SET_EXPR_LOCUS (t, EXPR_LOCUS (stmt));
 591   tsi_link_before (tsi, t, TSI_SAME_STMT);
 592   tsi_delink (tsi);
 593 }
 594
 595 /* Lower a __builtin_setjmp TSI.
 596
 597    __builtin_setjmp is passed a pointer to an array of five words (not
 598    all will be used on all machines).  It operates similarly to the C
 599    library function of the same name, but is more efficient.
 600
 601    It is lowered into 3 other builtins, namely __builtin_setjmp_setup,
 602    __builtin_setjmp_dispatcher and __builtin_setjmp_receiver, but with
 603    __builtin_setjmp_dispatcher shared among all the instances; that's
 604    why it is only emitted at the end by lower_function_body.
 605
 606    After full lowering, the body of the function should look like:
 607
 608     {
 609       void * setjmpvar.0;
 610       int D.1844;
 611       int D.2844;
 612
 613       [...]
 614
 615       __builtin_setjmp_setup (&buf, &<D1847>);
 616       D.1844 = 0;
 617       goto <D1846>;
 618       <D1847>:;
 619       __builtin_setjmp_receiver (&<D1847>);
 620       D.1844 = 1;
 621       <D1846>:;
 622       if (D.1844 == 0) goto <D1848>; else goto <D1849>;
 623
 624       [...]
 625
 626       __builtin_setjmp_setup (&buf, &<D2847>);
 627       D.2844 = 0;
 628       goto <D2846>;
 629       <D2847>:;
 630       __builtin_setjmp_receiver (&<D2847>);
 631       D.2844 = 1;
 632       <D2846>:;
 633       if (D.2844 == 0) goto <D2848>; else goto <D2849>;
 634
 635       [...]
 636
 637       <D3850>:;
 638       return;
 639       <D3853>: [non-local];
 640       setjmpvar.0 = __builtin_setjmp_dispatcher (&<D3853>);
 641       goto setjmpvar.0;
 642     }
 643
 644    The dispatcher block will be both the unique destination of all the
 645    abnormal call edges and the unique source of all the abnormal edges
 646    to the receivers, thus keeping the complexity explosion localized.  */
 647
 648 static void
 649 lower_builtin_setjmp (tree_stmt_iterator *tsi)
 650 {
 651   tree stmt = tsi_stmt (*tsi);
 652   tree cont_label = create_artificial_label ();
 653   tree next_label = create_artificial_label ();
 654   tree dest, t, arg;
 655
 656   /* NEXT_LABEL is the label __builtin_longjmp will jump to.  Its address is
 657      passed to both __builtin_setjmp_setup and __builtin_setjmp_receiver.  */
 658   FORCED_LABEL (next_label) = 1;
 659
 660   if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT)
 661     {
 662       dest = GIMPLE_STMT_OPERAND (stmt, 0);
 663       stmt = GIMPLE_STMT_OPERAND (stmt, 1);
 664     }
 665   else
 666     dest = NULL_TREE;
 667
 668   /* Build '__builtin_setjmp_setup (BUF, NEXT_LABEL)' and insert.  */
 669   arg = build_addr (next_label, current_function_decl);
 670   t = implicit_built_in_decls[BUILT_IN_SETJMP_SETUP];
 671   t = build_call_expr (t, 2, CALL_EXPR_ARG (stmt, 0), arg);
 672   SET_EXPR_LOCUS (t, EXPR_LOCUS (stmt));
 673   tsi_link_before (tsi, t, TSI_SAME_STMT);
 674
 675   /* Build 'DEST = 0' and insert.  */
 676   if (dest)
 677     {
 678       t = build_gimple_modify_stmt (dest, fold_convert (TREE_TYPE (dest),
 679                                                         integer_zero_node));
 680       SET_EXPR_LOCUS (t, EXPR_LOCUS (stmt));
 681       tsi_link_before (tsi, t, TSI_SAME_STMT);
 682     }
 683
 684   /* Build 'goto CONT_LABEL' and insert.  */
 685   t = build1 (GOTO_EXPR, void_type_node, cont_label);
 686   tsi_link_before (tsi, t, TSI_SAME_STMT);
 687
 688   /* Build 'NEXT_LABEL:' and insert.  */
 689   t = build1 (LABEL_EXPR, void_type_node, next_label);
 690   tsi_link_before (tsi, t, TSI_SAME_STMT);
 691
 692   /* Build '__builtin_setjmp_receiver (NEXT_LABEL)' and insert.  */
 693   arg = build_addr (next_label, current_function_decl);
 694   t = implicit_built_in_decls[BUILT_IN_SETJMP_RECEIVER];
 695   t = build_call_expr (t, 1, arg);
 696   SET_EXPR_LOCUS (t, EXPR_LOCUS (stmt));
 697   tsi_link_before (tsi, t, TSI_SAME_STMT);
 698
 699   /* Build 'DEST = 1' and insert.  */
 700   if (dest)
 701     {
 702       t = build_gimple_modify_stmt (dest, fold_convert (TREE_TYPE (dest),
 703                                                         integer_one_node));
 704       SET_EXPR_LOCUS (t, EXPR_LOCUS (stmt));
 705       tsi_link_before (tsi, t, TSI_SAME_STMT);
 706     }
 707
 708   /* Build 'CONT_LABEL:' and insert.  */
 709   t = build1 (LABEL_EXPR, void_type_node, cont_label);
 710   tsi_link_before (tsi, t, TSI_SAME_STMT);
 711
 712   /* Remove the call to __builtin_setjmp.  */
 713   tsi_delink (tsi);
 714 }
 715 \f
 716
 717 /* Record the variables in VARS into function FN.  */
 718
 719 void
 720 record_vars_into (tree vars, tree fn)
 721 {
 722   if (fn != current_function_decl)
 723     push_cfun (DECL_STRUCT_FUNCTION (fn));
 724
 725   for (; vars; vars = TREE_CHAIN (vars))
 726     {
 727       tree var = vars;
 728
 729       /* BIND_EXPRs contains also function/type/constant declarations
 730          we don't need to care about.  */
 731       if (TREE_CODE (var) != VAR_DECL)
 732         continue;
 733
 734       /* Nothing to do in this case.  */
 735       if (DECL_EXTERNAL (var))
 736         continue;
 737
 738       /* Record the variable.  */
 739       cfun->local_decls = tree_cons (NULL_TREE, var,
 740                                              cfun->local_decls);
 741     }
 742
 743   if (fn != current_function_decl)
 744     pop_cfun ();
 745 }
 746
 747
 748 /* Record the variables in VARS into current_function_decl.  */
 749
 750 void
 751 record_vars (tree vars)
 752 {
 753   record_vars_into (vars, current_function_decl);
 754 }
 755
 756
 757 /* Mark BLOCK used if it has a used variable in it, then recurse over its
 758    subblocks.  */
 759
 760 static void
 761 mark_blocks_with_used_vars (tree block)
 762 {
 763   tree var;
 764   tree subblock;
 765
 766   if (!TREE_USED (block))
 767     {
 768       for (var = BLOCK_VARS (block);
 769            var;
 770            var = TREE_CHAIN (var))
 771         {
 772           if (TREE_USED (var))
 773             {
 774               TREE_USED (block) = true;
 775               break;
 776             }
 777         }
 778     }
 779   for (subblock = BLOCK_SUBBLOCKS (block);
 780        subblock;
 781        subblock = BLOCK_CHAIN (subblock))
 782     mark_blocks_with_used_vars (subblock);
 783 }
 784
 785 /* Mark the used attribute on blocks correctly.  */
 786
 787 static unsigned int
 788 mark_used_blocks (void)
 789 {
 790   mark_blocks_with_used_vars (DECL_INITIAL (current_function_decl));
 791   return 0;
 792 }
 793
 794
 795 struct gimple_opt_pass pass_mark_used_blocks =
 796 {
 797  {
 798   GIMPLE_PASS,
 799   "blocks",                             /* name */
 800   NULL,                                 /* gate */
 801   mark_used_blocks,                     /* execute */
 802   NULL,                                 /* sub */
 803   NULL,                                 /* next */
 804   0,                                    /* static_pass_number */
 805   0,                                    /* tv_id */
 806   0,                                    /* properties_required */
 807   0,                                    /* properties_provided */
 808   0,                                    /* properties_destroyed */
 809   0,                                    /* todo_flags_start */
 810   TODO_dump_func                        /* todo_flags_finish */
 811  }
 812 };