gcc/cp/optimize.c

   1 /* Perform optimizations on tree structure.
   2    Copyright (C) 1998, 1999, 2000, 2001, 2002, 2004, 2005, 2007, 2008, 2009,
   3    2010 Free Software Foundation, Inc.
   4    Written by Mark Michell (mark@codesourcery.com).
   5
   6 This file is part of GCC.
   7
   8 GCC is free software; you can redistribute it and/or modify it
   9 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, but
  14 WITHOUT ANY WARRANTY; without even the implied warranty of
  15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16 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 "cp-tree.h"
  28 #include "input.h"
  29 #include "params.h"
  30 #include "hashtab.h"
  31 #include "target.h"
  32 #include "debug.h"
  33 #include "tree-inline.h"
  34 #include "flags.h"
  35 #include "langhooks.h"
  36 #include "diagnostic-core.h"
  37 #include "tree-dump.h"
  38 #include "gimple.h"
  39 #include "tree-iterator.h"
  40 #include "cgraph.h"
  41
  42 /* Prototypes.  */
  43
  44 static void update_cloned_parm (tree, tree, bool);
  45
  46 /* CLONED_PARM is a copy of CLONE, generated for a cloned constructor
  47    or destructor.  Update it to ensure that the source-position for
  48    the cloned parameter matches that for the original, and that the
  49    debugging generation code will be able to find the original PARM.  */
  50
  51 static void
  52 update_cloned_parm (tree parm, tree cloned_parm, bool first)
  53 {
  54   DECL_ABSTRACT_ORIGIN (cloned_parm) = parm;
  55
  56   /* We may have taken its address.  */
  57   TREE_ADDRESSABLE (cloned_parm) = TREE_ADDRESSABLE (parm);
  58
  59   /* The definition might have different constness.  */
  60   TREE_READONLY (cloned_parm) = TREE_READONLY (parm);
  61
  62   TREE_USED (cloned_parm) = !first || TREE_USED (parm);
  63
  64   /* The name may have changed from the declaration.  */
  65   DECL_NAME (cloned_parm) = DECL_NAME (parm);
  66   DECL_SOURCE_LOCATION (cloned_parm) = DECL_SOURCE_LOCATION (parm);
  67   TREE_TYPE (cloned_parm) = TREE_TYPE (parm);
  68
  69   DECL_GIMPLE_REG_P (cloned_parm) = DECL_GIMPLE_REG_P (parm);
  70 }
  71
  72
  73 /* FN is a function in High GIMPLE form that has a complete body and no
  74    CFG.  CLONE is a function whose body is to be set to a copy of FN,
  75    mapping argument declarations according to the ARG_MAP splay_tree.  */
  76
  77 static void
  78 clone_body (tree clone, tree fn, void *arg_map)
  79 {
  80   copy_body_data id;
  81   tree stmts;
  82
  83   /* Clone the body, as if we were making an inline call.  But, remap
  84      the parameters in the callee to the parameters of caller.  */
  85   memset (&id, 0, sizeof (id));
  86   id.src_fn = fn;
  87   id.dst_fn = clone;
  88   id.src_cfun = DECL_STRUCT_FUNCTION (fn);
  89   id.decl_map = (struct pointer_map_t *) arg_map;
  90
  91   id.copy_decl = copy_decl_no_change;
  92   id.transform_call_graph_edges = CB_CGE_DUPLICATE;
  93   id.transform_new_cfg = true;
  94   id.transform_return_to_modify = false;
  95   id.transform_lang_insert_block = NULL;
  96
  97   /* We're not inside any EH region.  */
  98   id.eh_lp_nr = 0;
  99
 100   stmts = DECL_SAVED_TREE (fn);
 101   walk_tree (&stmts, copy_tree_body_r, &id, NULL);
 102
 103   /* Also remap the initializer of any static variables so that they (in
 104      particular, any label addresses) correspond to the base variant rather
 105      than the abstract one.  */
 106   if (DECL_NAME (clone) == base_dtor_identifier
 107       || DECL_NAME (clone) == base_ctor_identifier)
 108     {
 109       unsigned ix;
 110       tree decl;
 111
 112       FOR_EACH_LOCAL_DECL (DECL_STRUCT_FUNCTION (fn), ix, decl)
 113         walk_tree (&DECL_INITIAL (decl), copy_tree_body_r, &id, NULL);
 114     }
 115
 116   append_to_statement_list_force (stmts, &DECL_SAVED_TREE (clone));
 117 }
 118
 119 /* DELETE_DTOR is a delete destructor whose body will be built.
 120    COMPLETE_DTOR is the corresponding complete destructor.  */
 121
 122 static void
 123 build_delete_destructor_body (tree delete_dtor, tree complete_dtor)
 124 {
 125   tree call_dtor, call_delete;
 126   tree parm = DECL_ARGUMENTS (delete_dtor);
 127   tree virtual_size = cxx_sizeof (current_class_type);
 128
 129   /* Call the corresponding complete destructor.  */
 130   gcc_assert (complete_dtor);
 131   call_dtor = build_cxx_call (complete_dtor, 1, &parm);
 132   add_stmt (call_dtor);
 133
 134   add_stmt (build_stmt (0, LABEL_EXPR, cdtor_label));
 135
 136   /* Call the delete function.  */
 137   call_delete = build_op_delete_call (DELETE_EXPR, current_class_ptr,
 138                                       virtual_size,
 139                                       /*global_p=*/false,
 140                                       /*placement=*/NULL_TREE,
 141                                       /*alloc_fn=*/NULL_TREE);
 142   add_stmt (call_delete);
 143
 144   /* Return the address of the object.  */
 145   if (targetm.cxx.cdtor_returns_this ())
 146     {
 147       tree val = DECL_ARGUMENTS (delete_dtor);
 148       val = build2 (MODIFY_EXPR, TREE_TYPE (val),
 149                     DECL_RESULT (delete_dtor), val);
 150       add_stmt (build_stmt (0, RETURN_EXPR, val));
 151     }
 152 }
 153
 154 /* Return name of comdat group for complete and base ctor (or dtor)
 155    that have the same body.  If dtor is virtual, deleting dtor goes
 156    into this comdat group as well.  */
 157
 158 static tree
 159 cdtor_comdat_group (tree complete, tree base)
 160 {
 161   tree complete_name = DECL_COMDAT_GROUP (complete);
 162   tree base_name = DECL_COMDAT_GROUP (base);
 163   char *grp_name;
 164   const char *p, *q;
 165   bool diff_seen = false;
 166   size_t idx;
 167   if (complete_name == NULL)
 168     complete_name = cxx_comdat_group (complete);
 169   if (base_name == NULL)
 170     base_name = cxx_comdat_group (base);
 171   gcc_assert (IDENTIFIER_LENGTH (complete_name)
 172               == IDENTIFIER_LENGTH (base_name));
 173   grp_name = XALLOCAVEC (char, IDENTIFIER_LENGTH (complete_name) + 1);
 174   p = IDENTIFIER_POINTER (complete_name);
 175   q = IDENTIFIER_POINTER (base_name);
 176   for (idx = 0; idx < IDENTIFIER_LENGTH (complete_name); idx++)
 177     if (p[idx] == q[idx])
 178       grp_name[idx] = p[idx];
 179     else
 180       {
 181         gcc_assert (!diff_seen
 182                     && idx > 0
 183                     && (p[idx - 1] == 'C' || p[idx - 1] == 'D')
 184                     && p[idx] == '1'
 185                     && q[idx] == '2');
 186         grp_name[idx] = '5';
 187         diff_seen = true;
 188       }
 189   grp_name[idx] = '\0';
 190   gcc_assert (diff_seen);
 191   return get_identifier (grp_name);
 192 }
 193
 194 /* FN is a function that has a complete body.  Clone the body as
 195    necessary.  Returns nonzero if there's no longer any need to
 196    process the main body.  */
 197
 198 bool
 199 maybe_clone_body (tree fn)
 200 {
 201   tree comdat_group = NULL_TREE;
 202   tree clone;
 203   tree fns[3];
 204   bool first = true;
 205   bool in_charge_parm_used;
 206   int idx;
 207   bool need_alias = false;
 208
 209   /* We only clone constructors and destructors.  */
 210   if (!DECL_MAYBE_IN_CHARGE_CONSTRUCTOR_P (fn)
 211       && !DECL_MAYBE_IN_CHARGE_DESTRUCTOR_P (fn))
 212     return 0;
 213
 214   /* Emit the DWARF1 abstract instance.  */
 215   (*debug_hooks->deferred_inline_function) (fn);
 216
 217   in_charge_parm_used = CLASSTYPE_VBASECLASSES (DECL_CONTEXT (fn)) != NULL;
 218   fns[0] = NULL_TREE;
 219   fns[1] = NULL_TREE;
 220   fns[2] = NULL_TREE;
 221
 222   /* Look for the complete destructor which may be used to build the
 223      delete destructor.  */
 224   FOR_EACH_CLONE (clone, fn)
 225     if (DECL_NAME (clone) == complete_dtor_identifier
 226         || DECL_NAME (clone) == complete_ctor_identifier)
 227       fns[1] = clone;
 228     else if (DECL_NAME (clone) == base_dtor_identifier
 229              || DECL_NAME (clone) == base_ctor_identifier)
 230       fns[0] = clone;
 231     else if (DECL_NAME (clone) == deleting_dtor_identifier)
 232       fns[2] = clone;
 233     else
 234       gcc_unreachable ();
 235
 236   /* Remember if we can't have multiple clones for some reason.  We need to
 237      check this before we remap local static initializers in clone_body.  */
 238   if (!tree_versionable_function_p (fn))
 239     need_alias = true;
 240
 241   /* We know that any clones immediately follow FN in the TYPE_METHODS
 242      list.  */
 243   push_to_top_level ();
 244   for (idx = 0; idx < 3; idx++)
 245     {
 246       tree parm;
 247       tree clone_parm;
 248       int parmno;
 249       bool alias = false;
 250       struct pointer_map_t *decl_map;
 251
 252       clone = fns[idx];
 253       if (!clone)
 254         continue;
 255
 256       /* Update CLONE's source position information to match FN's.  */
 257       DECL_SOURCE_LOCATION (clone) = DECL_SOURCE_LOCATION (fn);
 258       DECL_DECLARED_INLINE_P (clone) = DECL_DECLARED_INLINE_P (fn);
 259       DECL_DECLARED_CONSTEXPR_P (clone) = DECL_DECLARED_CONSTEXPR_P (fn);
 260       DECL_COMDAT (clone) = DECL_COMDAT (fn);
 261       DECL_WEAK (clone) = DECL_WEAK (fn);
 262
 263       /* We don't copy the comdat group from fn to clone because the assembler
 264          name of fn was corrupted by write_mangled_name by adding *INTERNAL*
 265          to it. By doing so, it also corrupted the comdat group. */
 266       if (DECL_ONE_ONLY (fn))
 267         DECL_COMDAT_GROUP (clone) = cxx_comdat_group (clone);
 268       DECL_SECTION_NAME (clone) = DECL_SECTION_NAME (fn);
 269       DECL_USE_TEMPLATE (clone) = DECL_USE_TEMPLATE (fn);
 270       DECL_EXTERNAL (clone) = DECL_EXTERNAL (fn);
 271       DECL_INTERFACE_KNOWN (clone) = DECL_INTERFACE_KNOWN (fn);
 272       DECL_NOT_REALLY_EXTERN (clone) = DECL_NOT_REALLY_EXTERN (fn);
 273       TREE_PUBLIC (clone) = TREE_PUBLIC (fn);
 274       DECL_VISIBILITY (clone) = DECL_VISIBILITY (fn);
 275       DECL_VISIBILITY_SPECIFIED (clone) = DECL_VISIBILITY_SPECIFIED (fn);
 276       DECL_DLLIMPORT_P (clone) = DECL_DLLIMPORT_P (fn);
 277       DECL_ATTRIBUTES (clone) = copy_list (DECL_ATTRIBUTES (fn));
 278       DECL_DISREGARD_INLINE_LIMITS (clone) = DECL_DISREGARD_INLINE_LIMITS (fn);
 279
 280       /* Adjust the parameter names and locations.  */
 281       parm = DECL_ARGUMENTS (fn);
 282       clone_parm = DECL_ARGUMENTS (clone);
 283       /* Update the `this' parameter, which is always first.  */
 284       update_cloned_parm (parm, clone_parm, first);
 285       parm = DECL_CHAIN (parm);
 286       clone_parm = DECL_CHAIN (clone_parm);
 287       if (DECL_HAS_IN_CHARGE_PARM_P (fn))
 288         parm = DECL_CHAIN (parm);
 289       if (DECL_HAS_VTT_PARM_P (fn))
 290         parm = DECL_CHAIN (parm);
 291       if (DECL_HAS_VTT_PARM_P (clone))
 292         clone_parm = DECL_CHAIN (clone_parm);
 293       for (; parm;
 294            parm = DECL_CHAIN (parm), clone_parm = DECL_CHAIN (clone_parm))
 295         /* Update this parameter.  */
 296         update_cloned_parm (parm, clone_parm, first);
 297
 298       /* Start processing the function.  */
 299       start_preparsed_function (clone, NULL_TREE, SF_PRE_PARSED);
 300
 301       /* Tell cgraph if both ctors or both dtors are known to have
 302          the same body.  */
 303       if (!in_charge_parm_used
 304           && fns[0]
 305           && idx == 1
 306           && !flag_use_repository
 307           && DECL_INTERFACE_KNOWN (fns[0])
 308           && (SUPPORTS_ONE_ONLY || !DECL_WEAK (fns[0]))
 309           && (!DECL_ONE_ONLY (fns[0])
 310               || (HAVE_COMDAT_GROUP
 311                   && DECL_WEAK (fns[0])))
 312           && !flag_syntax_only
 313           /* Set linkage flags appropriately before
 314              cgraph_create_function_alias looks at them.  */
 315           && expand_or_defer_fn_1 (clone)
 316           && cgraph_same_body_alias (cgraph_get_node (fns[0]),
 317                                      clone, fns[0]))
 318         {
 319           alias = true;
 320           if (DECL_ONE_ONLY (fns[0]))
 321             {
 322               /* For comdat base and complete cdtors put them
 323                  into the same, *[CD]5* comdat group instead of
 324                  *[CD][12]*.  */
 325               comdat_group = cdtor_comdat_group (fns[1], fns[0]);
 326               DECL_COMDAT_GROUP (fns[0]) = comdat_group;
 327               symtab_add_to_same_comdat_group (symtab_get_node (clone),
 328                                                symtab_get_node (fns[0]));
 329             }
 330         }
 331
 332       /* Build the delete destructor by calling complete destructor
 333          and delete function.  */
 334       if (idx == 2)
 335         {
 336           build_delete_destructor_body (clone, fns[1]);
 337           /* If *[CD][12]* dtors go into the *[CD]5* comdat group and dtor is
 338              virtual, it goes into the same comdat group as well.  */
 339           if (comdat_group)
 340             symtab_add_to_same_comdat_group
 341                ((symtab_node) cgraph_get_create_node (clone),
 342                 symtab_get_node (fns[0]));
 343         }
 344       else if (alias)
 345         /* No need to populate body.  */ ;
 346       else
 347         {
 348           /* If we can't have multiple copies of FN (say, because there's a
 349              static local initialized with the address of a label), we need
 350              to use an alias for the complete variant.  */
 351           if (idx == 1 && need_alias)
 352             {
 353               if (DECL_STRUCT_FUNCTION (fn)->cannot_be_copied_set)
 354                 sorry (DECL_STRUCT_FUNCTION (fn)->cannot_be_copied_reason, fn);
 355               else
 356                 sorry ("making multiple clones of %qD", fn);
 357             }
 358
 359           /* Remap the parameters.  */
 360           decl_map = pointer_map_create ();
 361           for (parmno = 0,
 362                 parm = DECL_ARGUMENTS (fn),
 363                 clone_parm = DECL_ARGUMENTS (clone);
 364               parm;
 365               ++parmno,
 366                 parm = DECL_CHAIN (parm))
 367             {
 368               /* Map the in-charge parameter to an appropriate constant.  */
 369               if (DECL_HAS_IN_CHARGE_PARM_P (fn) && parmno == 1)
 370                 {
 371                   tree in_charge;
 372                   in_charge = in_charge_arg_for_name (DECL_NAME (clone));
 373                   *pointer_map_insert (decl_map, parm) = in_charge;
 374                 }
 375               else if (DECL_ARTIFICIAL (parm)
 376                        && DECL_NAME (parm) == vtt_parm_identifier)
 377                 {
 378                   /* For a subobject constructor or destructor, the next
 379                      argument is the VTT parameter.  Remap the VTT_PARM
 380                      from the CLONE to this parameter.  */
 381                   if (DECL_HAS_VTT_PARM_P (clone))
 382                     {
 383                       DECL_ABSTRACT_ORIGIN (clone_parm) = parm;
 384                       *pointer_map_insert (decl_map, parm) = clone_parm;
 385                       clone_parm = DECL_CHAIN (clone_parm);
 386                     }
 387                   /* Otherwise, map the VTT parameter to `NULL'.  */
 388                   else
 389                     *pointer_map_insert (decl_map, parm)
 390                        = fold_convert (TREE_TYPE (parm), null_pointer_node);
 391                 }
 392               /* Map other parameters to their equivalents in the cloned
 393                  function.  */
 394               else
 395                 {
 396                   *pointer_map_insert (decl_map, parm) = clone_parm;
 397                   clone_parm = DECL_CHAIN (clone_parm);
 398                 }
 399             }
 400
 401           if (targetm.cxx.cdtor_returns_this ())
 402             {
 403               parm = DECL_RESULT (fn);
 404               clone_parm = DECL_RESULT (clone);
 405               *pointer_map_insert (decl_map, parm) = clone_parm;
 406             }
 407
 408           /* Clone the body.  */
 409           clone_body (clone, fn, decl_map);
 410
 411           /* Clean up.  */
 412           pointer_map_destroy (decl_map);
 413         }
 414
 415       /* The clone can throw iff the original function can throw.  */
 416       cp_function_chain->can_throw = !TREE_NOTHROW (fn);
 417
 418       /* Now, expand this function into RTL, if appropriate.  */
 419       finish_function (0);
 420       BLOCK_ABSTRACT_ORIGIN (DECL_INITIAL (clone)) = DECL_INITIAL (fn);
 421       if (alias)
 422         {
 423           if (expand_or_defer_fn_1 (clone))
 424             emit_associated_thunks (clone);
 425         }
 426       else
 427         expand_or_defer_fn (clone);
 428       first = false;
 429     }
 430   pop_from_top_level ();
 431
 432   /* We don't need to process the original function any further.  */
 433   return 1;
 434 }