gcc/cp/optimize.c

   1 /* Perform optimizations on tree structure.
   2    Copyright (C) 1998-2018 Free Software Foundation, Inc.
   3    Written by Mark Michell (mark@codesourcery.com).
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify it
   8 under the terms of the GNU General Public License as published by
   9 the Free Software Foundation; either version 3, or (at your option)
  10 any later version.
  11
  12 GCC is distributed in the hope that it will be useful, but
  13 WITHOUT ANY WARRANTY; without even the implied warranty of
  14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15 General Public License 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 "target.h"
  25 #include "cp-tree.h"
  26 #include "stringpool.h"
  27 #include "cgraph.h"
  28 #include "debug.h"
  29 #include "tree-inline.h"
  30 #include "tree-iterator.h"
  31
  32 /* Prototypes.  */
  33
  34 static void update_cloned_parm (tree, tree, bool);
  35
  36 /* CLONED_PARM is a copy of CLONE, generated for a cloned constructor
  37    or destructor.  Update it to ensure that the source-position for
  38    the cloned parameter matches that for the original, and that the
  39    debugging generation code will be able to find the original PARM.  */
  40
  41 static void
  42 update_cloned_parm (tree parm, tree cloned_parm, bool first)
  43 {
  44   DECL_ABSTRACT_ORIGIN (cloned_parm) = parm;
  45
  46   /* We may have taken its address.  */
  47   TREE_ADDRESSABLE (cloned_parm) = TREE_ADDRESSABLE (parm);
  48
  49   /* The definition might have different constness.  */
  50   TREE_READONLY (cloned_parm) = TREE_READONLY (parm);
  51
  52   TREE_USED (cloned_parm) = !first || TREE_USED (parm);
  53
  54   /* The name may have changed from the declaration.  */
  55   DECL_NAME (cloned_parm) = DECL_NAME (parm);
  56   DECL_SOURCE_LOCATION (cloned_parm) = DECL_SOURCE_LOCATION (parm);
  57   TREE_TYPE (cloned_parm) = TREE_TYPE (parm);
  58
  59   DECL_GIMPLE_REG_P (cloned_parm) = DECL_GIMPLE_REG_P (parm);
  60 }
  61
  62
  63 /* FN is a function in High GIMPLE form that has a complete body and no
  64    CFG.  CLONE is a function whose body is to be set to a copy of FN,
  65    mapping argument declarations according to the ARG_MAP splay_tree.  */
  66
  67 static void
  68 clone_body (tree clone, tree fn, void *arg_map)
  69 {
  70   copy_body_data id;
  71   tree stmts;
  72
  73   /* Clone the body, as if we were making an inline call.  But, remap
  74      the parameters in the callee to the parameters of caller.  */
  75   memset (&id, 0, sizeof (id));
  76   id.src_fn = fn;
  77   id.dst_fn = clone;
  78   id.src_cfun = DECL_STRUCT_FUNCTION (fn);
  79   id.decl_map = static_cast<hash_map<tree, tree> *> (arg_map);
  80
  81   id.copy_decl = copy_decl_no_change;
  82   id.transform_call_graph_edges = CB_CGE_DUPLICATE;
  83   id.transform_new_cfg = true;
  84   id.transform_return_to_modify = false;
  85   id.transform_lang_insert_block = NULL;
  86
  87   /* We're not inside any EH region.  */
  88   id.eh_lp_nr = 0;
  89
  90   stmts = DECL_SAVED_TREE (fn);
  91   walk_tree (&stmts, copy_tree_body_r, &id, NULL);
  92
  93   /* Also remap the initializer of any static variables so that they (in
  94      particular, any label addresses) correspond to the base variant rather
  95      than the abstract one.  */
  96   if (DECL_NAME (clone) == base_dtor_identifier
  97       || DECL_NAME (clone) == base_ctor_identifier)
  98     {
  99       unsigned ix;
 100       tree decl;
 101
 102       FOR_EACH_LOCAL_DECL (DECL_STRUCT_FUNCTION (fn), ix, decl)
 103         walk_tree (&DECL_INITIAL (decl), copy_tree_body_r, &id, NULL);
 104     }
 105
 106   append_to_statement_list_force (stmts, &DECL_SAVED_TREE (clone));
 107 }
 108
 109 /* DELETE_DTOR is a delete destructor whose body will be built.
 110    COMPLETE_DTOR is the corresponding complete destructor.  */
 111
 112 static void
 113 build_delete_destructor_body (tree delete_dtor, tree complete_dtor)
 114 {
 115   tree parm = DECL_ARGUMENTS (delete_dtor);
 116   tree virtual_size = cxx_sizeof (current_class_type);
 117
 118   /* Call the corresponding complete destructor.  */
 119   gcc_assert (complete_dtor);
 120   tree call_dtor = build_cxx_call (complete_dtor, 1, &parm,
 121                                    tf_warning_or_error);
 122
 123   /* Call the delete function.  */
 124   tree call_delete = build_op_delete_call (DELETE_EXPR, current_class_ptr,
 125                                            virtual_size,
 126                                            /*global_p=*/false,
 127                                            /*placement=*/NULL_TREE,
 128                                            /*alloc_fn=*/NULL_TREE,
 129                                            tf_warning_or_error);
 130
 131   /* Operator delete must be called, whether or not the dtor throws.  */
 132   add_stmt (build2 (TRY_FINALLY_EXPR, void_type_node, call_dtor, call_delete));
 133
 134   /* Return the address of the object.  */
 135   if (targetm.cxx.cdtor_returns_this ())
 136     {
 137       tree val = DECL_ARGUMENTS (delete_dtor);
 138       val = build2 (MODIFY_EXPR, TREE_TYPE (val),
 139                     DECL_RESULT (delete_dtor), val);
 140       add_stmt (build_stmt (0, RETURN_EXPR, val));
 141     }
 142 }
 143
 144 /* Return name of comdat group for complete and base ctor (or dtor)
 145    that have the same body.  If dtor is virtual, deleting dtor goes
 146    into this comdat group as well.  */
 147
 148 static tree
 149 cdtor_comdat_group (tree complete, tree base)
 150 {
 151   tree complete_name = DECL_ASSEMBLER_NAME (complete);
 152   tree base_name = DECL_ASSEMBLER_NAME (base);
 153   char *grp_name;
 154   const char *p, *q;
 155   bool diff_seen = false;
 156   size_t idx;
 157   gcc_assert (IDENTIFIER_LENGTH (complete_name)
 158               == IDENTIFIER_LENGTH (base_name));
 159   grp_name = XALLOCAVEC (char, IDENTIFIER_LENGTH (complete_name) + 1);
 160   p = IDENTIFIER_POINTER (complete_name);
 161   q = IDENTIFIER_POINTER (base_name);
 162   for (idx = 0; idx < IDENTIFIER_LENGTH (complete_name); idx++)
 163     if (p[idx] == q[idx])
 164       grp_name[idx] = p[idx];
 165     else
 166       {
 167         gcc_assert (!diff_seen
 168                     && idx > 0
 169                     && (p[idx - 1] == 'C' || p[idx - 1] == 'D'
 170                         || p[idx - 1] == 'I')
 171                     && p[idx] == '1'
 172                     && q[idx] == '2');
 173         grp_name[idx] = '5';
 174         diff_seen = true;
 175       }
 176   grp_name[idx] = '\0';
 177   gcc_assert (diff_seen);
 178   return get_identifier (grp_name);
 179 }
 180
 181 /* Returns true iff we can make the base and complete [cd]tor aliases of
 182    the same symbol rather than separate functions.  */
 183
 184 static bool
 185 can_alias_cdtor (tree fn)
 186 {
 187   /* If aliases aren't supported by the assembler, fail.  */
 188   if (!TARGET_SUPPORTS_ALIASES)
 189     return false;
 190
 191   /* We can't use an alias if there are virtual bases.  */
 192   if (CLASSTYPE_VBASECLASSES (DECL_CONTEXT (fn)))
 193     return false;
 194   /* ??? Why not use aliases with -frepo?  */
 195   if (flag_use_repository)
 196     return false;
 197   gcc_assert (DECL_MAYBE_IN_CHARGE_CONSTRUCTOR_P (fn)
 198               || DECL_MAYBE_IN_CHARGE_DESTRUCTOR_P (fn));
 199   /* Don't use aliases for weak/linkonce definitions unless we can put both
 200      symbols in the same COMDAT group.  */
 201   return (DECL_INTERFACE_KNOWN (fn)
 202           && (SUPPORTS_ONE_ONLY || !DECL_WEAK (fn))
 203           && (!DECL_ONE_ONLY (fn)
 204               || (HAVE_COMDAT_GROUP && DECL_WEAK (fn))));
 205 }
 206
 207 /* FN is a [cd]tor, fns is a pointer to an array of length 3.  Fill fns
 208    with pointers to the base, complete, and deleting variants.  */
 209
 210 static void
 211 populate_clone_array (tree fn, tree *fns)
 212 {
 213   tree clone;
 214
 215   fns[0] = NULL_TREE;
 216   fns[1] = NULL_TREE;
 217   fns[2] = NULL_TREE;
 218
 219   /* Look for the complete destructor which may be used to build the
 220      delete destructor.  */
 221   FOR_EACH_CLONE (clone, fn)
 222     if (DECL_NAME (clone) == complete_dtor_identifier
 223         || DECL_NAME (clone) == complete_ctor_identifier)
 224       fns[1] = clone;
 225     else if (DECL_NAME (clone) == base_dtor_identifier
 226              || DECL_NAME (clone) == base_ctor_identifier)
 227       fns[0] = clone;
 228     else if (DECL_NAME (clone) == deleting_dtor_identifier)
 229       fns[2] = clone;
 230     else
 231       gcc_unreachable ();
 232 }
 233
 234 /* FN is a constructor or destructor, and there are FUNCTION_DECLs
 235    cloned from it nearby.  Instead of cloning this body, leave it
 236    alone and create tiny one-call bodies for the cloned
 237    FUNCTION_DECLs.  These clones are sibcall candidates, and their
 238    resulting code will be very thunk-esque.  */
 239
 240 static bool
 241 maybe_thunk_body (tree fn, bool force)
 242 {
 243   tree bind, block, call, clone, clone_result, fn_parm, fn_parm_typelist;
 244   tree last_arg, modify, *args;
 245   int parmno, vtt_parmno, max_parms;
 246   tree fns[3];
 247
 248   if (!force && !flag_declone_ctor_dtor)
 249     return 0;
 250
 251   /* If function accepts variable arguments, give up.  */
 252   last_arg = tree_last (TYPE_ARG_TYPES (TREE_TYPE (fn)));
 253   if (last_arg != void_list_node)
 254     return 0;
 255
 256   /* If we got this far, we've decided to turn the clones into thunks.  */
 257
 258   /* We're going to generate code for fn, so it is no longer "abstract."
 259      Also make the unified ctor/dtor private to either the translation unit
 260      (for non-vague linkage ctors) or the COMDAT group (otherwise).  */
 261
 262   populate_clone_array (fn, fns);
 263
 264   /* Can happen during error recovery (c++/71464).  */
 265   if (!fns[0] || !fns[1])
 266     return 0;
 267
 268   /* Don't use thunks if the base clone omits inherited parameters.  */
 269   if (ctor_omit_inherited_parms (fns[0]))
 270     return 0;
 271
 272   DECL_ABSTRACT_P (fn) = false;
 273   if (!DECL_WEAK (fn))
 274     {
 275       TREE_PUBLIC (fn) = false;
 276       DECL_EXTERNAL (fn) = false;
 277       DECL_INTERFACE_KNOWN (fn) = true;
 278     }
 279   else if (HAVE_COMDAT_GROUP)
 280     {
 281       /* At eof, defer creation of mangling aliases temporarily.  */
 282       bool save_defer_mangling_aliases = defer_mangling_aliases;
 283       defer_mangling_aliases = true;
 284       tree comdat_group = cdtor_comdat_group (fns[1], fns[0]);
 285       defer_mangling_aliases = save_defer_mangling_aliases;
 286       cgraph_node::get_create (fns[0])->set_comdat_group (comdat_group);
 287       cgraph_node::get_create (fns[1])->add_to_same_comdat_group
 288         (cgraph_node::get_create (fns[0]));
 289       symtab_node::get (fn)->add_to_same_comdat_group
 290         (symtab_node::get (fns[0]));
 291       if (fns[2])
 292         /* If *[CD][12]* dtors go into the *[CD]5* comdat group and dtor is
 293            virtual, it goes into the same comdat group as well.  */
 294         cgraph_node::get_create (fns[2])->add_to_same_comdat_group
 295           (symtab_node::get (fns[0]));
 296       /* Emit them now that the thunks are same comdat group aliases.  */
 297       if (!save_defer_mangling_aliases)
 298         generate_mangling_aliases ();
 299       TREE_PUBLIC (fn) = false;
 300       DECL_EXTERNAL (fn) = false;
 301       DECL_INTERFACE_KNOWN (fn) = true;
 302       /* function_and_variable_visibility doesn't want !PUBLIC decls to
 303          have these flags set.  */
 304       DECL_WEAK (fn) = false;
 305       DECL_COMDAT (fn) = false;
 306     }
 307
 308   /* Find the vtt_parm, if present.  */
 309   for (vtt_parmno = -1, parmno = 0, fn_parm = DECL_ARGUMENTS (fn);
 310        fn_parm;
 311        ++parmno, fn_parm = TREE_CHAIN (fn_parm))
 312     {
 313       if (DECL_ARTIFICIAL (fn_parm)
 314           && DECL_NAME (fn_parm) == vtt_parm_identifier)
 315         {
 316           /* Compensate for removed in_charge parameter.  */
 317           vtt_parmno = parmno;
 318           break;
 319         }
 320     }
 321
 322   /* Allocate an argument buffer for build_cxx_call().
 323      Make sure it is large enough for any of the clones.  */
 324   max_parms = 0;
 325   FOR_EACH_CLONE (clone, fn)
 326     {
 327       int length = list_length (DECL_ARGUMENTS (fn));
 328       if (length > max_parms)
 329         max_parms = length;
 330     }
 331   args = XALLOCAVEC (tree, max_parms);
 332
 333   /* We know that any clones immediately follow FN in TYPE_FIELDS.  */
 334   FOR_EACH_CLONE (clone, fn)
 335     {
 336       tree clone_parm;
 337
 338       /* If we've already generated a body for this clone, avoid
 339          duplicating it.  (Is it possible for a clone-list to grow after we
 340          first see it?)  */
 341       if (DECL_SAVED_TREE (clone) || TREE_ASM_WRITTEN (clone))
 342         continue;
 343
 344       /* Start processing the function.  */
 345       start_preparsed_function (clone, NULL_TREE, SF_PRE_PARSED);
 346
 347       if (clone == fns[2])
 348         {
 349           for (clone_parm = DECL_ARGUMENTS (clone); clone_parm;
 350                clone_parm = TREE_CHAIN (clone_parm))
 351             DECL_ABSTRACT_ORIGIN (clone_parm) = NULL_TREE;
 352           /* Build the delete destructor by calling complete destructor and
 353              delete function.  */
 354           build_delete_destructor_body (clone, fns[1]);
 355         }
 356       else
 357         {
 358           /* Walk parameter lists together, creating parameter list for
 359              call to original function.  */
 360           for (parmno = 0,
 361                  fn_parm = DECL_ARGUMENTS (fn),
 362                  fn_parm_typelist = TYPE_ARG_TYPES (TREE_TYPE (fn)),
 363                  clone_parm = DECL_ARGUMENTS (clone);
 364                fn_parm;
 365                ++parmno,
 366                  fn_parm = TREE_CHAIN (fn_parm))
 367             {
 368               if (parmno == vtt_parmno && ! DECL_HAS_VTT_PARM_P (clone))
 369                 {
 370                   gcc_assert (fn_parm_typelist);
 371                   /* Clobber argument with formal parameter type.  */
 372                   args[parmno]
 373                     = convert (TREE_VALUE (fn_parm_typelist),
 374                                null_pointer_node);
 375                 }
 376               else if (parmno == 1 && DECL_HAS_IN_CHARGE_PARM_P (fn))
 377                 {
 378                   tree in_charge
 379                     = copy_node (in_charge_arg_for_name (DECL_NAME (clone)));
 380                   args[parmno] = in_charge;
 381                 }
 382               /* Map other parameters to their equivalents in the cloned
 383                  function.  */
 384               else
 385                 {
 386                   gcc_assert (clone_parm);
 387                   DECL_ABSTRACT_ORIGIN (clone_parm) = NULL;
 388                   args[parmno] = clone_parm;
 389                   clone_parm = TREE_CHAIN (clone_parm);
 390                 }
 391               if (fn_parm_typelist)
 392                 fn_parm_typelist = TREE_CHAIN (fn_parm_typelist);
 393             }
 394
 395           /* We built this list backwards; fix now.  */
 396           mark_used (fn);
 397           call = build_cxx_call (fn, parmno, args, tf_warning_or_error);
 398           /* Arguments passed to the thunk by invisible reference should
 399              be transmitted to the callee unchanged.  Do not create a
 400              temporary and invoke the copy constructor.  The thunking
 401              transformation must not introduce any constructor calls.  */
 402           CALL_FROM_THUNK_P (call) = 1;
 403           block = make_node (BLOCK);
 404           if (targetm.cxx.cdtor_returns_this ())
 405             {
 406               clone_result = DECL_RESULT (clone);
 407               modify = build2 (MODIFY_EXPR, TREE_TYPE (clone_result),
 408                                clone_result, call);
 409               modify = build1 (RETURN_EXPR, void_type_node, modify);
 410               add_stmt (modify);
 411             }
 412           else
 413             {
 414               add_stmt (call);
 415             }
 416           bind = c_build_bind_expr (DECL_SOURCE_LOCATION (clone),
 417                                     block, cur_stmt_list);
 418           DECL_SAVED_TREE (clone) = push_stmt_list ();
 419           add_stmt (bind);
 420         }
 421
 422       DECL_ABSTRACT_ORIGIN (clone) = NULL;
 423       expand_or_defer_fn (finish_function (/*inline_p=*/false));
 424     }
 425   return 1;
 426 }
 427
 428 /* FN is a function that has a complete body.  Clone the body as
 429    necessary.  Returns nonzero if there's no longer any need to
 430    process the main body.  */
 431
 432 bool
 433 maybe_clone_body (tree fn)
 434 {
 435   tree comdat_group = NULL_TREE;
 436   tree clone;
 437   tree fns[3];
 438   bool first = true;
 439   int idx;
 440   bool need_alias = false;
 441
 442   /* We only clone constructors and destructors.  */
 443   if (!DECL_MAYBE_IN_CHARGE_CONSTRUCTOR_P (fn)
 444       && !DECL_MAYBE_IN_CHARGE_DESTRUCTOR_P (fn))
 445     return 0;
 446
 447   populate_clone_array (fn, fns);
 448
 449   /* Remember if we can't have multiple clones for some reason.  We need to
 450      check this before we remap local static initializers in clone_body.  */
 451   if (!tree_versionable_function_p (fn))
 452     need_alias = true;
 453
 454   /* We know that any clones immediately follow FN in the TYPE_FIELDS
 455      list.  */
 456   push_to_top_level ();
 457   for (idx = 0; idx < 3; idx++)
 458     {
 459       tree parm;
 460       tree clone_parm;
 461
 462       clone = fns[idx];
 463       if (!clone)
 464         continue;
 465
 466       /* Update CLONE's source position information to match FN's.  */
 467       DECL_SOURCE_LOCATION (clone) = DECL_SOURCE_LOCATION (fn);
 468       DECL_DECLARED_INLINE_P (clone) = DECL_DECLARED_INLINE_P (fn);
 469       DECL_DECLARED_CONSTEXPR_P (clone) = DECL_DECLARED_CONSTEXPR_P (fn);
 470       DECL_COMDAT (clone) = DECL_COMDAT (fn);
 471       DECL_WEAK (clone) = DECL_WEAK (fn);
 472
 473       /* We don't copy the comdat group from fn to clone because the assembler
 474          name of fn was corrupted by write_mangled_name by adding *INTERNAL*
 475          to it. By doing so, it also corrupted the comdat group. */
 476       if (DECL_ONE_ONLY (fn))
 477         cgraph_node::get_create (clone)->set_comdat_group (cxx_comdat_group (clone));
 478       DECL_USE_TEMPLATE (clone) = DECL_USE_TEMPLATE (fn);
 479       DECL_EXTERNAL (clone) = DECL_EXTERNAL (fn);
 480       DECL_INTERFACE_KNOWN (clone) = DECL_INTERFACE_KNOWN (fn);
 481       DECL_NOT_REALLY_EXTERN (clone) = DECL_NOT_REALLY_EXTERN (fn);
 482       TREE_PUBLIC (clone) = TREE_PUBLIC (fn);
 483       DECL_VISIBILITY (clone) = DECL_VISIBILITY (fn);
 484       DECL_VISIBILITY_SPECIFIED (clone) = DECL_VISIBILITY_SPECIFIED (fn);
 485       DECL_DLLIMPORT_P (clone) = DECL_DLLIMPORT_P (fn);
 486       DECL_ATTRIBUTES (clone) = copy_list (DECL_ATTRIBUTES (fn));
 487       DECL_DISREGARD_INLINE_LIMITS (clone) = DECL_DISREGARD_INLINE_LIMITS (fn);
 488       set_decl_section_name (clone, DECL_SECTION_NAME (fn));
 489
 490       /* Adjust the parameter names and locations.  */
 491       parm = DECL_ARGUMENTS (fn);
 492       clone_parm = DECL_ARGUMENTS (clone);
 493       /* Update the `this' parameter, which is always first.  */
 494       update_cloned_parm (parm, clone_parm, first);
 495       parm = DECL_CHAIN (parm);
 496       clone_parm = DECL_CHAIN (clone_parm);
 497       if (DECL_HAS_IN_CHARGE_PARM_P (fn))
 498         parm = DECL_CHAIN (parm);
 499       if (DECL_HAS_VTT_PARM_P (fn))
 500         parm = DECL_CHAIN (parm);
 501       if (DECL_HAS_VTT_PARM_P (clone))
 502         clone_parm = DECL_CHAIN (clone_parm);
 503       for (; parm && clone_parm;
 504            parm = DECL_CHAIN (parm), clone_parm = DECL_CHAIN (clone_parm))
 505         /* Update this parameter.  */
 506         update_cloned_parm (parm, clone_parm, first);
 507     }
 508
 509   bool can_alias = can_alias_cdtor (fn);
 510
 511   /* If we decide to turn clones into thunks, they will branch to fn.
 512      Must have original function available to call.  */
 513   if (!can_alias && maybe_thunk_body (fn, need_alias))
 514     {
 515       pop_from_top_level ();
 516       /* We still need to emit the original function.  */
 517       return 0;
 518     }
 519
 520   /* Emit the DWARF1 abstract instance.  */
 521   (*debug_hooks->deferred_inline_function) (fn);
 522
 523   /* We know that any clones immediately follow FN in the TYPE_FIELDS. */
 524   for (idx = 0; idx < 3; idx++)
 525     {
 526       tree parm;
 527       tree clone_parm;
 528       int parmno;
 529       hash_map<tree, tree> *decl_map;
 530       bool alias = false;
 531
 532       clone = fns[idx];
 533       if (!clone)
 534         continue;
 535
 536       /* Start processing the function.  */
 537       start_preparsed_function (clone, NULL_TREE, SF_PRE_PARSED);
 538
 539       /* Tell cgraph if both ctors or both dtors are known to have
 540          the same body.  */
 541       if (can_alias
 542           && fns[0]
 543           && idx == 1
 544           && cgraph_node::get_create (fns[0])->create_same_body_alias
 545                (clone, fns[0]))
 546         {
 547           alias = true;
 548           if (DECL_ONE_ONLY (fns[0]))
 549             {
 550               /* For comdat base and complete cdtors put them
 551                  into the same, *[CD]5* comdat group instead of
 552                  *[CD][12]*.  */
 553               comdat_group = cdtor_comdat_group (fns[1], fns[0]);
 554               cgraph_node::get_create (fns[0])->set_comdat_group (comdat_group);
 555               if (symtab_node::get (clone)->same_comdat_group)
 556                 symtab_node::get (clone)->remove_from_same_comdat_group ();
 557               symtab_node::get (clone)->add_to_same_comdat_group
 558                 (symtab_node::get (fns[0]));
 559             }
 560         }
 561
 562       /* Build the delete destructor by calling complete destructor
 563          and delete function.  */
 564       if (idx == 2)
 565         {
 566           build_delete_destructor_body (clone, fns[1]);
 567           /* If *[CD][12]* dtors go into the *[CD]5* comdat group and dtor is
 568              virtual, it goes into the same comdat group as well.  */
 569           if (comdat_group)
 570             cgraph_node::get_create (clone)->add_to_same_comdat_group
 571               (symtab_node::get (fns[0]));
 572         }
 573       else if (alias)
 574         /* No need to populate body.  */ ;
 575       else
 576         {
 577           /* If we can't have multiple copies of FN (say, because there's a
 578              static local initialized with the address of a label), we need
 579              to use an alias for the complete variant.  */
 580           if (idx == 1 && need_alias)
 581             {
 582               if (DECL_STRUCT_FUNCTION (fn)->cannot_be_copied_set)
 583                 sorry (DECL_STRUCT_FUNCTION (fn)->cannot_be_copied_reason, fn);
 584               else
 585                 sorry ("making multiple clones of %qD", fn);
 586             }
 587
 588           /* Remap the parameters.  */
 589           decl_map = new hash_map<tree, tree>;
 590           for (parmno = 0,
 591                 parm = DECL_ARGUMENTS (fn),
 592                 clone_parm = DECL_ARGUMENTS (clone);
 593               parm;
 594               ++parmno,
 595                 parm = DECL_CHAIN (parm))
 596             {
 597               /* Map the in-charge parameter to an appropriate constant.  */
 598               if (DECL_HAS_IN_CHARGE_PARM_P (fn) && parmno == 1)
 599                 {
 600                   tree in_charge;
 601                   in_charge = in_charge_arg_for_name (DECL_NAME (clone));
 602                   decl_map->put (parm, in_charge);
 603                 }
 604               else if (DECL_ARTIFICIAL (parm)
 605                        && DECL_NAME (parm) == vtt_parm_identifier)
 606                 {
 607                   /* For a subobject constructor or destructor, the next
 608                      argument is the VTT parameter.  Remap the VTT_PARM
 609                      from the CLONE to this parameter.  */
 610                   if (DECL_HAS_VTT_PARM_P (clone))
 611                     {
 612                       DECL_ABSTRACT_ORIGIN (clone_parm) = parm;
 613                       decl_map->put (parm, clone_parm);
 614                       clone_parm = DECL_CHAIN (clone_parm);
 615                     }
 616                   /* Otherwise, map the VTT parameter to `NULL'.  */
 617                   else
 618                     {
 619                       tree t
 620                         = fold_convert (TREE_TYPE (parm), null_pointer_node);
 621                       decl_map->put (parm, t);
 622                     }
 623                 }
 624               /* Map other parameters to their equivalents in the cloned
 625                  function.  */
 626               else
 627                 {
 628                   tree replacement;
 629                   if (clone_parm)
 630                     {
 631                       replacement = clone_parm;
 632                       clone_parm = DECL_CHAIN (clone_parm);
 633                     }
 634                   else
 635                     {
 636                       /* Inheriting ctors can omit parameters from the base
 637                          clone.  Replace them with null lvalues.  */
 638                       tree reftype = build_reference_type (TREE_TYPE (parm));
 639                       replacement = fold_convert (reftype, null_pointer_node);
 640                       replacement = convert_from_reference (replacement);
 641                     }
 642                   decl_map->put (parm, replacement);
 643                 }
 644             }
 645
 646           if (targetm.cxx.cdtor_returns_this ())
 647             {
 648               parm = DECL_RESULT (fn);
 649               clone_parm = DECL_RESULT (clone);
 650               decl_map->put (parm, clone_parm);
 651             }
 652
 653           /* Clone the body.  */
 654           clone_body (clone, fn, decl_map);
 655
 656           /* Clean up.  */
 657           delete decl_map;
 658         }
 659
 660       /* The clone can throw iff the original function can throw.  */
 661       cp_function_chain->can_throw = !TREE_NOTHROW (fn);
 662
 663       /* Now, expand this function into RTL, if appropriate.  */
 664       finish_function (/*inline_p=*/false);
 665       BLOCK_ABSTRACT_ORIGIN (DECL_INITIAL (clone)) = DECL_INITIAL (fn);
 666       if (alias)
 667         {
 668           if (expand_or_defer_fn_1 (clone))
 669             emit_associated_thunks (clone);
 670           /* We didn't generate a body, so remove the empty one.  */
 671           DECL_SAVED_TREE (clone) = NULL_TREE;
 672         }
 673       else
 674         expand_or_defer_fn (clone);
 675       first = false;
 676     }
 677   pop_from_top_level ();
 678
 679   /* We don't need to process the original function any further.  */
 680   return 1;
 681 }