gcc/tree-stdarg.c

   1 /* Pass computing data for optimizing stdarg functions.
   2    Copyright (C) 2004, 2005, 2007, 2008, 2009, 2010, 2011
   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 "function.h"
  28 #include "langhooks.h"
  29 #include "gimple-pretty-print.h"
  30 #include "target.h"
  31 #include "tree-flow.h"
  32 #include "tree-pass.h"
  33 #include "tree-stdarg.h"
  34
  35 /* A simple pass that attempts to optimize stdarg functions on architectures
  36    that need to save register arguments to stack on entry to stdarg functions.
  37    If the function doesn't use any va_start macros, no registers need to
  38    be saved.  If va_start macros are used, the va_list variables don't escape
  39    the function, it is only necessary to save registers that will be used
  40    in va_arg macros.  E.g. if va_arg is only used with integral types
  41    in the function, floating point registers don't need to be saved, etc.  */
  42
  43
  44 /* Return true if basic block VA_ARG_BB is dominated by VA_START_BB and
  45    is executed at most as many times as VA_START_BB.  */
  46
  47 static bool
  48 reachable_at_most_once (basic_block va_arg_bb, basic_block va_start_bb)
  49 {
  50   vec<edge> stack = vec<edge>();
  51   edge e;
  52   edge_iterator ei;
  53   sbitmap visited;
  54   bool ret;
  55
  56   if (va_arg_bb == va_start_bb)
  57     return true;
  58
  59   if (! dominated_by_p (CDI_DOMINATORS, va_arg_bb, va_start_bb))
  60     return false;
  61
  62   visited = sbitmap_alloc (last_basic_block);
  63   bitmap_clear (visited);
  64   ret = true;
  65
  66   FOR_EACH_EDGE (e, ei, va_arg_bb->preds)
  67     stack.safe_push (e);
  68
  69   while (! stack.is_empty ())
  70     {
  71       basic_block src;
  72
  73       e = stack.pop ();
  74       src = e->src;
  75
  76       if (e->flags & EDGE_COMPLEX)
  77         {
  78           ret = false;
  79           break;
  80         }
  81
  82       if (src == va_start_bb)
  83         continue;
  84
  85       /* va_arg_bb can be executed more times than va_start_bb.  */
  86       if (src == va_arg_bb)
  87         {
  88           ret = false;
  89           break;
  90         }
  91
  92       gcc_assert (src != ENTRY_BLOCK_PTR);
  93
  94       if (! bitmap_bit_p (visited, src->index))
  95         {
  96           bitmap_set_bit (visited, src->index);
  97           FOR_EACH_EDGE (e, ei, src->preds)
  98             stack.safe_push (e);
  99         }
 100     }
 101
 102   stack.release ();
 103   sbitmap_free (visited);
 104   return ret;
 105 }
 106
 107
 108 /* For statement COUNTER = RHS, if RHS is COUNTER + constant,
 109    return constant, otherwise return (unsigned HOST_WIDE_INT) -1.
 110    GPR_P is true if this is GPR counter.  */
 111
 112 static unsigned HOST_WIDE_INT
 113 va_list_counter_bump (struct stdarg_info *si, tree counter, tree rhs,
 114                       bool gpr_p)
 115 {
 116   tree lhs, orig_lhs;
 117   gimple stmt;
 118   unsigned HOST_WIDE_INT ret = 0, val, counter_val;
 119   unsigned int max_size;
 120
 121   if (si->offsets == NULL)
 122     {
 123       unsigned int i;
 124
 125       si->offsets = XNEWVEC (int, num_ssa_names);
 126       for (i = 0; i < num_ssa_names; ++i)
 127         si->offsets[i] = -1;
 128     }
 129
 130   counter_val = gpr_p ? cfun->va_list_gpr_size : cfun->va_list_fpr_size;
 131   max_size = gpr_p ? VA_LIST_MAX_GPR_SIZE : VA_LIST_MAX_FPR_SIZE;
 132   orig_lhs = lhs = rhs;
 133   while (lhs)
 134     {
 135       enum tree_code rhs_code;
 136       tree rhs1;
 137
 138       if (si->offsets[SSA_NAME_VERSION (lhs)] != -1)
 139         {
 140           if (counter_val >= max_size)
 141             {
 142               ret = max_size;
 143               break;
 144             }
 145
 146           ret -= counter_val - si->offsets[SSA_NAME_VERSION (lhs)];
 147           break;
 148         }
 149
 150       stmt = SSA_NAME_DEF_STMT (lhs);
 151
 152       if (!is_gimple_assign (stmt) || gimple_assign_lhs (stmt) != lhs)
 153         return (unsigned HOST_WIDE_INT) -1;
 154
 155       rhs_code = gimple_assign_rhs_code (stmt);
 156       rhs1 = gimple_assign_rhs1 (stmt);
 157       if ((get_gimple_rhs_class (rhs_code) == GIMPLE_SINGLE_RHS
 158            || gimple_assign_cast_p (stmt))
 159           && TREE_CODE (rhs1) == SSA_NAME)
 160         {
 161           lhs = rhs1;
 162           continue;
 163         }
 164
 165       if ((rhs_code == POINTER_PLUS_EXPR
 166            || rhs_code == PLUS_EXPR)
 167           && TREE_CODE (rhs1) == SSA_NAME
 168           && host_integerp (gimple_assign_rhs2 (stmt), 1))
 169         {
 170           ret += tree_low_cst (gimple_assign_rhs2 (stmt), 1);
 171           lhs = rhs1;
 172           continue;
 173         }
 174
 175       if (rhs_code == ADDR_EXPR
 176           && TREE_CODE (TREE_OPERAND (rhs1, 0)) == MEM_REF
 177           && TREE_CODE (TREE_OPERAND (TREE_OPERAND (rhs1, 0), 0)) == SSA_NAME
 178           && host_integerp (TREE_OPERAND (TREE_OPERAND (rhs1, 0), 1), 1))
 179         {
 180           ret += tree_low_cst (TREE_OPERAND (TREE_OPERAND (rhs1, 0), 1), 1);
 181           lhs = TREE_OPERAND (TREE_OPERAND (rhs1, 0), 0);
 182           continue;
 183         }
 184
 185       if (get_gimple_rhs_class (rhs_code) != GIMPLE_SINGLE_RHS)
 186         return (unsigned HOST_WIDE_INT) -1;
 187
 188       rhs = gimple_assign_rhs1 (stmt);
 189       if (TREE_CODE (counter) != TREE_CODE (rhs))
 190         return (unsigned HOST_WIDE_INT) -1;
 191
 192       if (TREE_CODE (counter) == COMPONENT_REF)
 193         {
 194           if (get_base_address (counter) != get_base_address (rhs)
 195               || TREE_CODE (TREE_OPERAND (rhs, 1)) != FIELD_DECL
 196               || TREE_OPERAND (counter, 1) != TREE_OPERAND (rhs, 1))
 197             return (unsigned HOST_WIDE_INT) -1;
 198         }
 199       else if (counter != rhs)
 200         return (unsigned HOST_WIDE_INT) -1;
 201
 202       lhs = NULL;
 203     }
 204
 205   lhs = orig_lhs;
 206   val = ret + counter_val;
 207   while (lhs)
 208     {
 209       enum tree_code rhs_code;
 210       tree rhs1;
 211
 212       if (si->offsets[SSA_NAME_VERSION (lhs)] != -1)
 213         break;
 214
 215       if (val >= max_size)
 216         si->offsets[SSA_NAME_VERSION (lhs)] = max_size;
 217       else
 218         si->offsets[SSA_NAME_VERSION (lhs)] = val;
 219
 220       stmt = SSA_NAME_DEF_STMT (lhs);
 221
 222       rhs_code = gimple_assign_rhs_code (stmt);
 223       rhs1 = gimple_assign_rhs1 (stmt);
 224       if ((get_gimple_rhs_class (rhs_code) == GIMPLE_SINGLE_RHS
 225            || gimple_assign_cast_p (stmt))
 226           && TREE_CODE (rhs1) == SSA_NAME)
 227         {
 228           lhs = rhs1;
 229           continue;
 230         }
 231
 232       if ((rhs_code == POINTER_PLUS_EXPR
 233            || rhs_code == PLUS_EXPR)
 234           && TREE_CODE (rhs1) == SSA_NAME
 235           && host_integerp (gimple_assign_rhs2 (stmt), 1))
 236         {
 237           val -= tree_low_cst (gimple_assign_rhs2 (stmt), 1);
 238           lhs = rhs1;
 239           continue;
 240         }
 241
 242       if (rhs_code == ADDR_EXPR
 243           && TREE_CODE (TREE_OPERAND (rhs1, 0)) == MEM_REF
 244           && TREE_CODE (TREE_OPERAND (TREE_OPERAND (rhs1, 0), 0)) == SSA_NAME
 245           && host_integerp (TREE_OPERAND (TREE_OPERAND (rhs1, 0), 1), 1))
 246         {
 247           val -= tree_low_cst (TREE_OPERAND (TREE_OPERAND (rhs1, 0), 1), 1);
 248           lhs = TREE_OPERAND (TREE_OPERAND (rhs1, 0), 0);
 249           continue;
 250         }
 251
 252       lhs = NULL;
 253     }
 254
 255   return ret;
 256 }
 257
 258
 259 /* Called by walk_tree to look for references to va_list variables.  */
 260
 261 static tree
 262 find_va_list_reference (tree *tp, int *walk_subtrees ATTRIBUTE_UNUSED,
 263                         void *data)
 264 {
 265   bitmap va_list_vars = (bitmap) ((struct walk_stmt_info *) data)->info;
 266   tree var = *tp;
 267
 268   if (TREE_CODE (var) == SSA_NAME)
 269     {
 270       if (bitmap_bit_p (va_list_vars, SSA_NAME_VERSION (var)))
 271         return var;
 272     }
 273   else if (TREE_CODE (var) == VAR_DECL)
 274     {
 275       if (bitmap_bit_p (va_list_vars, DECL_UID (var) + num_ssa_names))
 276         return var;
 277     }
 278
 279   return NULL_TREE;
 280 }
 281
 282
 283 /* Helper function of va_list_counter_struct_op.  Compute
 284    cfun->va_list_{g,f}pr_size.  AP is a va_list GPR/FPR counter,
 285    if WRITE_P is true, seen in AP = VAR, otherwise seen in VAR = AP
 286    statement.  GPR_P is true if AP is a GPR counter, false if it is
 287    a FPR counter.  */
 288
 289 static void
 290 va_list_counter_op (struct stdarg_info *si, tree ap, tree var, bool gpr_p,
 291                     bool write_p)
 292 {
 293   unsigned HOST_WIDE_INT increment;
 294
 295   if (si->compute_sizes < 0)
 296     {
 297       si->compute_sizes = 0;
 298       if (si->va_start_count == 1
 299           && reachable_at_most_once (si->bb, si->va_start_bb))
 300         si->compute_sizes = 1;
 301
 302       if (dump_file && (dump_flags & TDF_DETAILS))
 303         fprintf (dump_file,
 304                  "bb%d will %sbe executed at most once for each va_start "
 305                  "in bb%d\n", si->bb->index, si->compute_sizes ? "" : "not ",
 306                  si->va_start_bb->index);
 307     }
 308
 309   if (write_p
 310       && si->compute_sizes
 311       && (increment = va_list_counter_bump (si, ap, var, gpr_p)) + 1 > 1)
 312     {
 313       if (gpr_p && cfun->va_list_gpr_size + increment < VA_LIST_MAX_GPR_SIZE)
 314         {
 315           cfun->va_list_gpr_size += increment;
 316           return;
 317         }
 318
 319       if (!gpr_p && cfun->va_list_fpr_size + increment < VA_LIST_MAX_FPR_SIZE)
 320         {
 321           cfun->va_list_fpr_size += increment;
 322           return;
 323         }
 324     }
 325
 326   if (write_p || !si->compute_sizes)
 327     {
 328       if (gpr_p)
 329         cfun->va_list_gpr_size = VA_LIST_MAX_GPR_SIZE;
 330       else
 331         cfun->va_list_fpr_size = VA_LIST_MAX_FPR_SIZE;
 332     }
 333 }
 334
 335
 336 /* If AP is a va_list GPR/FPR counter, compute cfun->va_list_{g,f}pr_size.
 337    If WRITE_P is true, AP has been seen in AP = VAR assignment, if WRITE_P
 338    is false, AP has been seen in VAR = AP assignment.
 339    Return true if the AP = VAR (resp. VAR = AP) statement is a recognized
 340    va_arg operation that doesn't cause the va_list variable to escape
 341    current function.  */
 342
 343 static bool
 344 va_list_counter_struct_op (struct stdarg_info *si, tree ap, tree var,
 345                            bool write_p)
 346 {
 347   tree base;
 348
 349   if (TREE_CODE (ap) != COMPONENT_REF
 350       || TREE_CODE (TREE_OPERAND (ap, 1)) != FIELD_DECL)
 351     return false;
 352
 353   if (TREE_CODE (var) != SSA_NAME
 354       || bitmap_bit_p (si->va_list_vars, SSA_NAME_VERSION (var)))
 355     return false;
 356
 357   base = get_base_address (ap);
 358   if (TREE_CODE (base) != VAR_DECL
 359       || !bitmap_bit_p (si->va_list_vars, DECL_UID (base) + num_ssa_names))
 360     return false;
 361
 362   if (TREE_OPERAND (ap, 1) == va_list_gpr_counter_field)
 363     va_list_counter_op (si, ap, var, true, write_p);
 364   else if (TREE_OPERAND (ap, 1) == va_list_fpr_counter_field)
 365     va_list_counter_op (si, ap, var, false, write_p);
 366
 367   return true;
 368 }
 369
 370
 371 /* Check for TEM = AP.  Return true if found and the caller shouldn't
 372    search for va_list references in the statement.  */
 373
 374 static bool
 375 va_list_ptr_read (struct stdarg_info *si, tree ap, tree tem)
 376 {
 377   if (TREE_CODE (ap) != VAR_DECL
 378       || !bitmap_bit_p (si->va_list_vars, DECL_UID (ap) + num_ssa_names))
 379     return false;
 380
 381   if (TREE_CODE (tem) != SSA_NAME
 382       || bitmap_bit_p (si->va_list_vars, SSA_NAME_VERSION (tem)))
 383     return false;
 384
 385   if (si->compute_sizes < 0)
 386     {
 387       si->compute_sizes = 0;
 388       if (si->va_start_count == 1
 389           && reachable_at_most_once (si->bb, si->va_start_bb))
 390         si->compute_sizes = 1;
 391
 392       if (dump_file && (dump_flags & TDF_DETAILS))
 393         fprintf (dump_file,
 394                  "bb%d will %sbe executed at most once for each va_start "
 395                  "in bb%d\n", si->bb->index, si->compute_sizes ? "" : "not ",
 396                  si->va_start_bb->index);
 397     }
 398
 399   /* For void * or char * va_list types, there is just one counter.
 400      If va_arg is used in a loop, we don't know how many registers need
 401      saving.  */
 402   if (! si->compute_sizes)
 403     return false;
 404
 405   if (va_list_counter_bump (si, ap, tem, true) == (unsigned HOST_WIDE_INT) -1)
 406     return false;
 407
 408   /* Note the temporary, as we need to track whether it doesn't escape
 409      the current function.  */
 410   bitmap_set_bit (si->va_list_escape_vars, SSA_NAME_VERSION (tem));
 411
 412   return true;
 413 }
 414
 415
 416 /* Check for:
 417      tem1 = AP;
 418      TEM2 = tem1 + CST;
 419      AP = TEM2;
 420    sequence and update cfun->va_list_gpr_size.  Return true if found.  */
 421
 422 static bool
 423 va_list_ptr_write (struct stdarg_info *si, tree ap, tree tem2)
 424 {
 425   unsigned HOST_WIDE_INT increment;
 426
 427   if (TREE_CODE (ap) != VAR_DECL
 428       || !bitmap_bit_p (si->va_list_vars, DECL_UID (ap) + num_ssa_names))
 429     return false;
 430
 431   if (TREE_CODE (tem2) != SSA_NAME
 432       || bitmap_bit_p (si->va_list_vars, SSA_NAME_VERSION (tem2)))
 433     return false;
 434
 435   if (si->compute_sizes <= 0)
 436     return false;
 437
 438   increment = va_list_counter_bump (si, ap, tem2, true);
 439   if (increment + 1 <= 1)
 440     return false;
 441
 442   if (cfun->va_list_gpr_size + increment < VA_LIST_MAX_GPR_SIZE)
 443     cfun->va_list_gpr_size += increment;
 444   else
 445     cfun->va_list_gpr_size = VA_LIST_MAX_GPR_SIZE;
 446
 447   return true;
 448 }
 449
 450
 451 /* If RHS is X, (some type *) X or X + CST for X a temporary variable
 452    containing value of some va_list variable plus optionally some constant,
 453    either set si->va_list_escapes or add LHS to si->va_list_escape_vars,
 454    depending whether LHS is a function local temporary.  */
 455
 456 static void
 457 check_va_list_escapes (struct stdarg_info *si, tree lhs, tree rhs)
 458 {
 459   if (! POINTER_TYPE_P (TREE_TYPE (rhs)))
 460     return;
 461
 462   if (TREE_CODE (rhs) == SSA_NAME)
 463     {
 464       if (! bitmap_bit_p (si->va_list_escape_vars, SSA_NAME_VERSION (rhs)))
 465         return;
 466     }
 467   else if (TREE_CODE (rhs) == ADDR_EXPR
 468            && TREE_CODE (TREE_OPERAND (rhs, 0)) == MEM_REF
 469            && TREE_CODE (TREE_OPERAND (TREE_OPERAND (rhs, 0), 0)) == SSA_NAME)
 470     {
 471       tree ptr = TREE_OPERAND (TREE_OPERAND (rhs, 0), 0);
 472       if (! bitmap_bit_p (si->va_list_escape_vars, SSA_NAME_VERSION (ptr)))
 473         return;
 474     }
 475   else
 476     return;
 477
 478   if (TREE_CODE (lhs) != SSA_NAME)
 479     {
 480       si->va_list_escapes = true;
 481       return;
 482     }
 483
 484   if (si->compute_sizes < 0)
 485     {
 486       si->compute_sizes = 0;
 487       if (si->va_start_count == 1
 488           && reachable_at_most_once (si->bb, si->va_start_bb))
 489         si->compute_sizes = 1;
 490
 491       if (dump_file && (dump_flags & TDF_DETAILS))
 492         fprintf (dump_file,
 493                  "bb%d will %sbe executed at most once for each va_start "
 494                  "in bb%d\n", si->bb->index, si->compute_sizes ? "" : "not ",
 495                  si->va_start_bb->index);
 496     }
 497
 498   /* For void * or char * va_list types, there is just one counter.
 499      If va_arg is used in a loop, we don't know how many registers need
 500      saving.  */
 501   if (! si->compute_sizes)
 502     {
 503       si->va_list_escapes = true;
 504       return;
 505     }
 506
 507   if (va_list_counter_bump (si, si->va_start_ap, lhs, true)
 508       == (unsigned HOST_WIDE_INT) -1)
 509     {
 510       si->va_list_escapes = true;
 511       return;
 512     }
 513
 514   bitmap_set_bit (si->va_list_escape_vars, SSA_NAME_VERSION (lhs));
 515 }
 516
 517
 518 /* Check all uses of temporaries from si->va_list_escape_vars bitmap.
 519    Return true if va_list might be escaping.  */
 520
 521 static bool
 522 check_all_va_list_escapes (struct stdarg_info *si)
 523 {
 524   basic_block bb;
 525
 526   FOR_EACH_BB (bb)
 527     {
 528       gimple_stmt_iterator i;
 529
 530       for (i = gsi_start_bb (bb); !gsi_end_p (i); gsi_next (&i))
 531         {
 532           gimple stmt = gsi_stmt (i);
 533           tree use;
 534           ssa_op_iter iter;
 535
 536           if (is_gimple_debug (stmt))
 537             continue;
 538
 539           FOR_EACH_SSA_TREE_OPERAND (use, stmt, iter, SSA_OP_ALL_USES)
 540             {
 541               if (! bitmap_bit_p (si->va_list_escape_vars,
 542                                   SSA_NAME_VERSION (use)))
 543                 continue;
 544
 545               if (is_gimple_assign (stmt))
 546                 {
 547                   tree rhs = gimple_assign_rhs1 (stmt);
 548                   enum tree_code rhs_code = gimple_assign_rhs_code (stmt);
 549
 550                   /* x = *ap_temp;  */
 551                   if (rhs_code == MEM_REF
 552                       && TREE_OPERAND (rhs, 0) == use
 553                       && TYPE_SIZE_UNIT (TREE_TYPE (rhs))
 554                       && host_integerp (TYPE_SIZE_UNIT (TREE_TYPE (rhs)), 1)
 555                       && si->offsets[SSA_NAME_VERSION (use)] != -1)
 556                     {
 557                       unsigned HOST_WIDE_INT gpr_size;
 558                       tree access_size = TYPE_SIZE_UNIT (TREE_TYPE (rhs));
 559
 560                       gpr_size = si->offsets[SSA_NAME_VERSION (use)]
 561                                  + tree_low_cst (TREE_OPERAND (rhs, 1), 0)
 562                                  + tree_low_cst (access_size, 1);
 563                       if (gpr_size >= VA_LIST_MAX_GPR_SIZE)
 564                         cfun->va_list_gpr_size = VA_LIST_MAX_GPR_SIZE;
 565                       else if (gpr_size > cfun->va_list_gpr_size)
 566                         cfun->va_list_gpr_size = gpr_size;
 567                       continue;
 568                     }
 569
 570                   /* va_arg sequences may contain
 571                      other_ap_temp = ap_temp;
 572                      other_ap_temp = ap_temp + constant;
 573                      other_ap_temp = (some_type *) ap_temp;
 574                      ap = ap_temp;
 575                      statements.  */
 576                   if (rhs == use
 577                       && ((rhs_code == POINTER_PLUS_EXPR
 578                            && (TREE_CODE (gimple_assign_rhs2 (stmt))
 579                                == INTEGER_CST))
 580                           || gimple_assign_cast_p (stmt)
 581                           || (get_gimple_rhs_class (rhs_code)
 582                               == GIMPLE_SINGLE_RHS)))
 583                     {
 584                       tree lhs = gimple_assign_lhs (stmt);
 585
 586                       if (TREE_CODE (lhs) == SSA_NAME
 587                           && bitmap_bit_p (si->va_list_escape_vars,
 588                                            SSA_NAME_VERSION (lhs)))
 589                         continue;
 590
 591                       if (TREE_CODE (lhs) == VAR_DECL
 592                           && bitmap_bit_p (si->va_list_vars,
 593                                            DECL_UID (lhs) + num_ssa_names))
 594                         continue;
 595                     }
 596                   else if (rhs_code == ADDR_EXPR
 597                            && TREE_CODE (TREE_OPERAND (rhs, 0)) == MEM_REF
 598                            && TREE_OPERAND (TREE_OPERAND (rhs, 0), 0) == use)
 599                     {
 600                       tree lhs = gimple_assign_lhs (stmt);
 601
 602                       if (bitmap_bit_p (si->va_list_escape_vars,
 603                                         SSA_NAME_VERSION (lhs)))
 604                         continue;
 605                     }
 606                 }
 607
 608               if (dump_file && (dump_flags & TDF_DETAILS))
 609                 {
 610                   fputs ("va_list escapes in ", dump_file);
 611                   print_gimple_stmt (dump_file, stmt, 0, dump_flags);
 612                   fputc ('\n', dump_file);
 613                 }
 614               return true;
 615             }
 616         }
 617     }
 618
 619   return false;
 620 }
 621
 622
 623 /* Return true if this optimization pass should be done.
 624    It makes only sense for stdarg functions.  */
 625
 626 static bool
 627 gate_optimize_stdarg (void)
 628 {
 629   /* This optimization is only for stdarg functions.  */
 630   return cfun->stdarg != 0;
 631 }
 632
 633
 634 /* Entry point to the stdarg optimization pass.  */
 635
 636 static unsigned int
 637 execute_optimize_stdarg (void)
 638 {
 639   basic_block bb;
 640   bool va_list_escapes = false;
 641   bool va_list_simple_ptr;
 642   struct stdarg_info si;
 643   struct walk_stmt_info wi;
 644   const char *funcname = NULL;
 645   tree cfun_va_list;
 646
 647   cfun->va_list_gpr_size = 0;
 648   cfun->va_list_fpr_size = 0;
 649   memset (&si, 0, sizeof (si));
 650   si.va_list_vars = BITMAP_ALLOC (NULL);
 651   si.va_list_escape_vars = BITMAP_ALLOC (NULL);
 652
 653   if (dump_file)
 654     funcname = lang_hooks.decl_printable_name (current_function_decl, 2);
 655
 656   cfun_va_list = targetm.fn_abi_va_list (cfun->decl);
 657   va_list_simple_ptr = POINTER_TYPE_P (cfun_va_list)
 658                        && (TREE_TYPE (cfun_va_list) == void_type_node
 659                            || TREE_TYPE (cfun_va_list) == char_type_node);
 660   gcc_assert (is_gimple_reg_type (cfun_va_list) == va_list_simple_ptr);
 661
 662   FOR_EACH_BB (bb)
 663     {
 664       gimple_stmt_iterator i;
 665
 666       for (i = gsi_start_bb (bb); !gsi_end_p (i); gsi_next (&i))
 667         {
 668           gimple stmt = gsi_stmt (i);
 669           tree callee, ap;
 670
 671           if (!is_gimple_call (stmt))
 672             continue;
 673
 674           callee = gimple_call_fndecl (stmt);
 675           if (!callee
 676               || DECL_BUILT_IN_CLASS (callee) != BUILT_IN_NORMAL)
 677             continue;
 678
 679           switch (DECL_FUNCTION_CODE (callee))
 680             {
 681             case BUILT_IN_VA_START:
 682               break;
 683               /* If old style builtins are used, don't optimize anything.  */
 684             case BUILT_IN_SAVEREGS:
 685             case BUILT_IN_NEXT_ARG:
 686               va_list_escapes = true;
 687               continue;
 688             default:
 689               continue;
 690             }
 691
 692           si.va_start_count++;
 693           ap = gimple_call_arg (stmt, 0);
 694
 695           if (TREE_CODE (ap) != ADDR_EXPR)
 696             {
 697               va_list_escapes = true;
 698               break;
 699             }
 700           ap = TREE_OPERAND (ap, 0);
 701           if (TREE_CODE (ap) == ARRAY_REF)
 702             {
 703               if (! integer_zerop (TREE_OPERAND (ap, 1)))
 704                 {
 705                   va_list_escapes = true;
 706                   break;
 707                 }
 708               ap = TREE_OPERAND (ap, 0);
 709             }
 710           if (TYPE_MAIN_VARIANT (TREE_TYPE (ap))
 711               != TYPE_MAIN_VARIANT (targetm.fn_abi_va_list (cfun->decl))
 712               || TREE_CODE (ap) != VAR_DECL)
 713             {
 714               va_list_escapes = true;
 715               break;
 716             }
 717
 718           if (is_global_var (ap))
 719             {
 720               va_list_escapes = true;
 721               break;
 722             }
 723
 724           bitmap_set_bit (si.va_list_vars, DECL_UID (ap) + num_ssa_names);
 725
 726           /* VA_START_BB and VA_START_AP will be only used if there is just
 727              one va_start in the function.  */
 728           si.va_start_bb = bb;
 729           si.va_start_ap = ap;
 730         }
 731
 732       if (va_list_escapes)
 733         break;
 734     }
 735
 736   /* If there were no va_start uses in the function, there is no need to
 737      save anything.  */
 738   if (si.va_start_count == 0)
 739     goto finish;
 740
 741   /* If some va_list arguments weren't local, we can't optimize.  */
 742   if (va_list_escapes)
 743     goto finish;
 744
 745   /* For void * or char * va_list, something useful can be done only
 746      if there is just one va_start.  */
 747   if (va_list_simple_ptr && si.va_start_count > 1)
 748     {
 749       va_list_escapes = true;
 750       goto finish;
 751     }
 752
 753   /* For struct * va_list, if the backend didn't tell us what the counter fields
 754      are, there is nothing more we can do.  */
 755   if (!va_list_simple_ptr
 756       && va_list_gpr_counter_field == NULL_TREE
 757       && va_list_fpr_counter_field == NULL_TREE)
 758     {
 759       va_list_escapes = true;
 760       goto finish;
 761     }
 762
 763   /* For void * or char * va_list there is just one counter
 764      (va_list itself).  Use VA_LIST_GPR_SIZE for it.  */
 765   if (va_list_simple_ptr)
 766     cfun->va_list_fpr_size = VA_LIST_MAX_FPR_SIZE;
 767
 768   calculate_dominance_info (CDI_DOMINATORS);
 769   memset (&wi, 0, sizeof (wi));
 770   wi.info = si.va_list_vars;
 771
 772   FOR_EACH_BB (bb)
 773     {
 774       gimple_stmt_iterator i;
 775
 776       si.compute_sizes = -1;
 777       si.bb = bb;
 778
 779       /* For va_list_simple_ptr, we have to check PHI nodes too.  We treat
 780          them as assignments for the purpose of escape analysis.  This is
 781          not needed for non-simple va_list because virtual phis don't perform
 782          any real data movement.  */
 783       if (va_list_simple_ptr)
 784         {
 785           tree lhs, rhs;
 786           use_operand_p uop;
 787           ssa_op_iter soi;
 788
 789           for (i = gsi_start_phis (bb); !gsi_end_p (i); gsi_next (&i))
 790             {
 791               gimple phi = gsi_stmt (i);
 792               lhs = PHI_RESULT (phi);
 793
 794               if (virtual_operand_p (lhs))
 795                 continue;
 796
 797               FOR_EACH_PHI_ARG (uop, phi, soi, SSA_OP_USE)
 798                 {
 799                   rhs = USE_FROM_PTR (uop);
 800                   if (va_list_ptr_read (&si, rhs, lhs))
 801                     continue;
 802                   else if (va_list_ptr_write (&si, lhs, rhs))
 803                     continue;
 804                   else
 805                     check_va_list_escapes (&si, lhs, rhs);
 806
 807                   if (si.va_list_escapes)
 808                     {
 809                       if (dump_file && (dump_flags & TDF_DETAILS))
 810                         {
 811                           fputs ("va_list escapes in ", dump_file);
 812                           print_gimple_stmt (dump_file, phi, 0, dump_flags);
 813                           fputc ('\n', dump_file);
 814                         }
 815                       va_list_escapes = true;
 816                     }
 817                 }
 818             }
 819         }
 820
 821       for (i = gsi_start_bb (bb);
 822            !gsi_end_p (i) && !va_list_escapes;
 823            gsi_next (&i))
 824         {
 825           gimple stmt = gsi_stmt (i);
 826
 827           /* Don't look at __builtin_va_{start,end}, they are ok.  */
 828           if (is_gimple_call (stmt))
 829             {
 830               tree callee = gimple_call_fndecl (stmt);
 831
 832               if (callee
 833                   && DECL_BUILT_IN_CLASS (callee) == BUILT_IN_NORMAL
 834                   && (DECL_FUNCTION_CODE (callee) == BUILT_IN_VA_START
 835                       || DECL_FUNCTION_CODE (callee) == BUILT_IN_VA_END))
 836                 continue;
 837             }
 838
 839           if (is_gimple_assign (stmt))
 840             {
 841               tree lhs = gimple_assign_lhs (stmt);
 842               tree rhs = gimple_assign_rhs1 (stmt);
 843
 844               if (va_list_simple_ptr)
 845                 {
 846                   if (get_gimple_rhs_class (gimple_assign_rhs_code (stmt))
 847                       == GIMPLE_SINGLE_RHS)
 848                     {
 849                       /* Check for ap ={v} {}.  */
 850                       if (TREE_CLOBBER_P (rhs))
 851                         continue;
 852
 853                       /* Check for tem = ap.  */
 854                       else if (va_list_ptr_read (&si, rhs, lhs))
 855                         continue;
 856
 857                       /* Check for the last insn in:
 858                          tem1 = ap;
 859                          tem2 = tem1 + CST;
 860                          ap = tem2;
 861                          sequence.  */
 862                       else if (va_list_ptr_write (&si, lhs, rhs))
 863                         continue;
 864                     }
 865
 866                   if ((gimple_assign_rhs_code (stmt) == POINTER_PLUS_EXPR
 867                        && TREE_CODE (gimple_assign_rhs2 (stmt)) == INTEGER_CST)
 868                       || CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (stmt))
 869                       || (get_gimple_rhs_class (gimple_assign_rhs_code (stmt))
 870                           == GIMPLE_SINGLE_RHS))
 871                     check_va_list_escapes (&si, lhs, rhs);
 872                 }
 873               else
 874                 {
 875                   if (get_gimple_rhs_class (gimple_assign_rhs_code (stmt))
 876                       == GIMPLE_SINGLE_RHS)
 877                     {
 878                       /* Check for ap ={v} {}.  */
 879                       if (TREE_CLOBBER_P (rhs))
 880                         continue;
 881
 882                       /* Check for ap[0].field = temp.  */
 883                       else if (va_list_counter_struct_op (&si, lhs, rhs, true))
 884                         continue;
 885
 886                       /* Check for temp = ap[0].field.  */
 887                       else if (va_list_counter_struct_op (&si, rhs, lhs,
 888                                                           false))
 889                         continue;
 890                     }
 891
 892                   /* Do any architecture specific checking.  */
 893                   if (targetm.stdarg_optimize_hook
 894                       && targetm.stdarg_optimize_hook (&si, stmt))
 895                     continue;
 896                 }
 897             }
 898           else if (is_gimple_debug (stmt))
 899             continue;
 900
 901           /* All other uses of va_list are either va_copy (that is not handled
 902              in this optimization), taking address of va_list variable or
 903              passing va_list to other functions (in that case va_list might
 904              escape the function and therefore va_start needs to set it up
 905              fully), or some unexpected use of va_list.  None of these should
 906              happen in a gimplified VA_ARG_EXPR.  */
 907           if (si.va_list_escapes
 908               || walk_gimple_op (stmt, find_va_list_reference, &wi))
 909             {
 910               if (dump_file && (dump_flags & TDF_DETAILS))
 911                 {
 912                   fputs ("va_list escapes in ", dump_file);
 913                   print_gimple_stmt (dump_file, stmt, 0, dump_flags);
 914                   fputc ('\n', dump_file);
 915                 }
 916               va_list_escapes = true;
 917             }
 918         }
 919
 920       if (va_list_escapes)
 921         break;
 922     }
 923
 924   if (! va_list_escapes
 925       && va_list_simple_ptr
 926       && ! bitmap_empty_p (si.va_list_escape_vars)
 927       && check_all_va_list_escapes (&si))
 928     va_list_escapes = true;
 929
 930 finish:
 931   if (va_list_escapes)
 932     {
 933       cfun->va_list_gpr_size = VA_LIST_MAX_GPR_SIZE;
 934       cfun->va_list_fpr_size = VA_LIST_MAX_FPR_SIZE;
 935     }
 936   BITMAP_FREE (si.va_list_vars);
 937   BITMAP_FREE (si.va_list_escape_vars);
 938   free (si.offsets);
 939   if (dump_file)
 940     {
 941       fprintf (dump_file, "%s: va_list escapes %d, needs to save ",
 942                funcname, (int) va_list_escapes);
 943       if (cfun->va_list_gpr_size >= VA_LIST_MAX_GPR_SIZE)
 944         fputs ("all", dump_file);
 945       else
 946         fprintf (dump_file, "%d", cfun->va_list_gpr_size);
 947       fputs (" GPR units and ", dump_file);
 948       if (cfun->va_list_fpr_size >= VA_LIST_MAX_FPR_SIZE)
 949         fputs ("all", dump_file);
 950       else
 951         fprintf (dump_file, "%d", cfun->va_list_fpr_size);
 952       fputs (" FPR units.\n", dump_file);
 953     }
 954   return 0;
 955 }
 956
 957
 958 struct gimple_opt_pass pass_stdarg =
 959 {
 960  {
 961   GIMPLE_PASS,
 962   "stdarg",                             /* name */
 963   OPTGROUP_NONE,                        /* optinfo_flags */
 964   gate_optimize_stdarg,                 /* gate */
 965   execute_optimize_stdarg,              /* execute */
 966   NULL,                                 /* sub */
 967   NULL,                                 /* next */
 968   0,                                    /* static_pass_number */
 969   TV_NONE,                              /* tv_id */
 970   PROP_cfg | PROP_ssa,                  /* properties_required */
 971   0,                                    /* properties_provided */
 972   0,                                    /* properties_destroyed */
 973   0,                                    /* todo_flags_start */
 974   0                                     /* todo_flags_finish */
 975  }
 976 };