gcc/multiple_target.c

   1 /* Pass for parsing functions with multiple target attributes.
   2
   3    Contributed by Evgeny Stupachenko <evstupac@gmail.com>
   4
   5    Copyright (C) 2015-2019 Free Software Foundation, Inc.
   6
   7 This file is part of GCC.
   8
   9 GCC is free software; you can redistribute it and/or modify it under
  10 the terms of the GNU General Public License as published by the Free
  11 Software Foundation; either version 3, or (at your option) any later
  12 version.
  13
  14 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  15 WARRANTY; without even the implied warranty of MERCHANTABILITY or
  16 FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  17 for more details.
  18
  19 You should have received a copy of the GNU General Public License
  20 along with GCC; see the file COPYING3.  If not see
  21 <http://www.gnu.org/licenses/>.  */
  22
  23 #include "config.h"
  24 #include "system.h"
  25 #include "coretypes.h"
  26 #include "backend.h"
  27 #include "tree.h"
  28 #include "stringpool.h"
  29 #include "gimple.h"
  30 #include "diagnostic-core.h"
  31 #include "gimple-ssa.h"
  32 #include "cgraph.h"
  33 #include "tree-pass.h"
  34 #include "target.h"
  35 #include "attribs.h"
  36 #include "pretty-print.h"
  37 #include "gimple-iterator.h"
  38 #include "gimple-walk.h"
  39 #include "tree-inline.h"
  40 #include "intl.h"
  41
  42 /* Walker callback that replaces all FUNCTION_DECL of a function that's
  43    going to be versioned.  */
  44
  45 static tree
  46 replace_function_decl (tree *op, int *walk_subtrees, void *data)
  47 {
  48   struct walk_stmt_info *wi = (struct walk_stmt_info *) data;
  49   cgraph_function_version_info *info = (cgraph_function_version_info *)wi->info;
  50
  51   if (TREE_CODE (*op) == FUNCTION_DECL
  52       && info->this_node->decl == *op)
  53     {
  54       *op = info->dispatcher_resolver;
  55       *walk_subtrees = 0;
  56     }
  57
  58   return NULL;
  59 }
  60
  61 /* If the call in NODE has multiple target attribute with multiple fields,
  62    replace it with dispatcher call and create dispatcher (once).  */
  63
  64 static void
  65 create_dispatcher_calls (struct cgraph_node *node)
  66 {
  67   ipa_ref *ref;
  68
  69   if (!DECL_FUNCTION_VERSIONED (node->decl)
  70       || !is_function_default_version (node->decl))
  71     return;
  72
  73   if (!targetm.has_ifunc_p ())
  74     {
  75       error_at (DECL_SOURCE_LOCATION (node->decl),
  76                 "the call requires ifunc, which is not"
  77                 " supported by this target");
  78       return;
  79     }
  80   else if (!targetm.get_function_versions_dispatcher)
  81     {
  82       error_at (DECL_SOURCE_LOCATION (node->decl),
  83                 "target does not support function version dispatcher");
  84       return;
  85     }
  86
  87   tree idecl = targetm.get_function_versions_dispatcher (node->decl);
  88   if (!idecl)
  89     {
  90       error_at (DECL_SOURCE_LOCATION (node->decl),
  91                 "default %<target_clones%> attribute was not set");
  92       return;
  93     }
  94
  95   cgraph_node *inode = cgraph_node::get (idecl);
  96   gcc_assert (inode);
  97   tree resolver_decl = targetm.generate_version_dispatcher_body (inode);
  98
  99   /* Update aliases.  */
 100   inode->alias = true;
 101   inode->alias_target = resolver_decl;
 102   if (!inode->analyzed)
 103     inode->resolve_alias (cgraph_node::get (resolver_decl));
 104
 105   auto_vec<cgraph_edge *> edges_to_redirect;
 106   auto_vec<ipa_ref *> references_to_redirect;
 107
 108   for (unsigned i = 0; node->iterate_referring (i, ref); i++)
 109     references_to_redirect.safe_push (ref);
 110
 111   /* We need to remember NEXT_CALLER as it could be modified in the loop.  */
 112   for (cgraph_edge *e = node->callers; e ; e = e->next_caller)
 113     edges_to_redirect.safe_push (e);
 114
 115   if (!edges_to_redirect.is_empty () || !references_to_redirect.is_empty ())
 116     {
 117       /* Redirect edges.  */
 118       unsigned i;
 119       cgraph_edge *e;
 120       FOR_EACH_VEC_ELT (edges_to_redirect, i, e)
 121         {
 122           e->redirect_callee (inode);
 123           e->redirect_call_stmt_to_callee ();
 124         }
 125
 126       /* Redirect references.  */
 127       FOR_EACH_VEC_ELT (references_to_redirect, i, ref)
 128         {
 129           if (ref->use == IPA_REF_ADDR)
 130             {
 131               struct walk_stmt_info wi;
 132               memset (&wi, 0, sizeof (wi));
 133               wi.info = (void *)node->function_version ();
 134
 135               if (dyn_cast<varpool_node *> (ref->referring))
 136                 {
 137                   hash_set<tree> visited_nodes;
 138                   walk_tree (&DECL_INITIAL (ref->referring->decl),
 139                              replace_function_decl, &wi, &visited_nodes);
 140                 }
 141               else
 142                 {
 143                   gimple_stmt_iterator it = gsi_for_stmt (ref->stmt);
 144                   if (ref->referring->decl != resolver_decl)
 145                     walk_gimple_stmt (&it, NULL, replace_function_decl, &wi);
 146                 }
 147
 148               symtab_node *source = ref->referring;
 149               ref->remove_reference ();
 150               source->create_reference (inode, IPA_REF_ADDR);
 151             }
 152           else if (ref->use == IPA_REF_ALIAS)
 153             {
 154               symtab_node *source = ref->referring;
 155               ref->remove_reference ();
 156               source->create_reference (inode, IPA_REF_ALIAS);
 157               source->add_to_same_comdat_group (inode);
 158             }
 159           else
 160             gcc_unreachable ();
 161         }
 162     }
 163
 164   symtab->change_decl_assembler_name (node->decl,
 165                                       clone_function_name_numbered (
 166                                           node->decl, "default"));
 167
 168   /* FIXME: copy of cgraph_node::make_local that should be cleaned up
 169             in next stage1.  */
 170   node->make_decl_local ();
 171   node->set_section (NULL);
 172   node->set_comdat_group (NULL);
 173   node->externally_visible = false;
 174   node->forced_by_abi = false;
 175   node->set_section (NULL);
 176   node->unique_name = ((node->resolution == LDPR_PREVAILING_DEF_IRONLY
 177                         || node->resolution == LDPR_PREVAILING_DEF_IRONLY_EXP)
 178                        && !flag_incremental_link);
 179   node->resolution = LDPR_PREVAILING_DEF_IRONLY;
 180
 181   DECL_ARTIFICIAL (node->decl) = 1;
 182   node->force_output = true;
 183 }
 184
 185 /* Return length of attribute names string,
 186    if arglist chain > 1, -1 otherwise.  */
 187
 188 static int
 189 get_attr_len (tree arglist)
 190 {
 191   tree arg;
 192   int str_len_sum = 0;
 193   int argnum = 0;
 194
 195   for (arg = arglist; arg; arg = TREE_CHAIN (arg))
 196     {
 197       const char *str = TREE_STRING_POINTER (TREE_VALUE (arg));
 198       size_t len = strlen (str);
 199       str_len_sum += len + 1;
 200       for (const char *p = strchr (str, ','); p; p = strchr (p + 1, ','))
 201         argnum++;
 202       argnum++;
 203     }
 204   if (argnum <= 1)
 205     return -1;
 206   return str_len_sum;
 207 }
 208
 209 /* Create string with attributes separated by comma.
 210    Return number of attributes.  */
 211
 212 static int
 213 get_attr_str (tree arglist, char *attr_str)
 214 {
 215   tree arg;
 216   size_t str_len_sum = 0;
 217   int argnum = 0;
 218
 219   for (arg = arglist; arg; arg = TREE_CHAIN (arg))
 220     {
 221       const char *str = TREE_STRING_POINTER (TREE_VALUE (arg));
 222       size_t len = strlen (str);
 223       for (const char *p = strchr (str, ','); p; p = strchr (p + 1, ','))
 224         argnum++;
 225       memcpy (attr_str + str_len_sum, str, len);
 226       attr_str[str_len_sum + len] = TREE_CHAIN (arg) ? ',' : '\0';
 227       str_len_sum += len + 1;
 228       argnum++;
 229     }
 230   return argnum;
 231 }
 232
 233 /* Return number of attributes separated by comma and put them into ARGS.
 234    If there is no DEFAULT attribute return -1.  If there is an empty
 235    string in attribute return -2.  */
 236
 237 static int
 238 separate_attrs (char *attr_str, char **attrs, int attrnum)
 239 {
 240   int i = 0;
 241   int default_count = 0;
 242
 243   for (char *attr = strtok (attr_str, ",");
 244        attr != NULL; attr = strtok (NULL, ","))
 245     {
 246       if (strcmp (attr, "default") == 0)
 247         {
 248           default_count++;
 249           continue;
 250         }
 251       attrs[i++] = attr;
 252     }
 253   if (default_count == 0)
 254     return -1;
 255   else if (i + default_count < attrnum)
 256     return -2;
 257
 258   return i;
 259 }
 260
 261 /*  Return true if symbol is valid in assembler name.  */
 262
 263 static bool
 264 is_valid_asm_symbol (char c)
 265 {
 266   if ('a' <= c && c <= 'z')
 267     return true;
 268   if ('A' <= c && c <= 'Z')
 269     return true;
 270   if ('0' <= c && c <= '9')
 271     return true;
 272   if (c == '_')
 273     return true;
 274   return false;
 275 }
 276
 277 /*  Replace all not valid assembler symbols with '_'.  */
 278
 279 static void
 280 create_new_asm_name (char *old_asm_name, char *new_asm_name)
 281 {
 282   int i;
 283   int old_name_len = strlen (old_asm_name);
 284
 285   /* Replace all not valid assembler symbols with '_'.  */
 286   for (i = 0; i < old_name_len; i++)
 287     if (!is_valid_asm_symbol (old_asm_name[i]))
 288       new_asm_name[i] = '_';
 289     else
 290       new_asm_name[i] = old_asm_name[i];
 291   new_asm_name[old_name_len] = '\0';
 292 }
 293
 294 /*  Creates target clone of NODE.  */
 295
 296 static cgraph_node *
 297 create_target_clone (cgraph_node *node, bool definition, char *name,
 298                      tree attributes)
 299 {
 300   cgraph_node *new_node;
 301
 302   if (definition)
 303     {
 304       new_node = node->create_version_clone_with_body (vNULL, NULL,
 305                                                        NULL, false,
 306                                                        NULL, NULL,
 307                                                        name, attributes);
 308       if (new_node == NULL)
 309         return NULL;
 310       new_node->force_output = true;
 311     }
 312   else
 313     {
 314       tree new_decl = copy_node (node->decl);
 315       new_node = cgraph_node::get_create (new_decl);
 316       DECL_ATTRIBUTES (new_decl) = attributes;
 317       /* Generate a new name for the new version.  */
 318       symtab->change_decl_assembler_name (new_node->decl,
 319                                           clone_function_name_numbered (
 320                                               node->decl, name));
 321     }
 322   return new_node;
 323 }
 324
 325 /* If the function in NODE has multiple target attributes
 326    create the appropriate clone for each valid target attribute.  */
 327
 328 static bool
 329 expand_target_clones (struct cgraph_node *node, bool definition)
 330 {
 331   int i;
 332   /* Parsing target attributes separated by comma.  */
 333   tree attr_target = lookup_attribute ("target_clones",
 334                                        DECL_ATTRIBUTES (node->decl));
 335   /* No targets specified.  */
 336   if (!attr_target)
 337     return false;
 338
 339   tree arglist = TREE_VALUE (attr_target);
 340   int attr_len = get_attr_len (arglist);
 341
 342   /* No need to clone for 1 target attribute.  */
 343   if (attr_len == -1)
 344     {
 345       warning_at (DECL_SOURCE_LOCATION (node->decl),
 346                   0,
 347                   "single %<target_clones%> attribute is ignored");
 348       return false;
 349     }
 350
 351   if (node->definition
 352       && !tree_versionable_function_p (node->decl))
 353     {
 354       auto_diagnostic_group d;
 355       error_at (DECL_SOURCE_LOCATION (node->decl),
 356                 "clones for %<target_clones%> attribute cannot be created");
 357       const char *reason = NULL;
 358       if (lookup_attribute ("noclone", DECL_ATTRIBUTES (node->decl)))
 359         reason = G_("function %q+F can never be copied "
 360                     "because it has %<noclone%> attribute");
 361       else
 362         reason = copy_forbidden (DECL_STRUCT_FUNCTION (node->decl));
 363       if (reason)
 364         inform (DECL_SOURCE_LOCATION (node->decl), reason, node->decl);
 365       return false;
 366     }
 367
 368   char *attr_str = XNEWVEC (char, attr_len);
 369   int attrnum = get_attr_str (arglist, attr_str);
 370   char **attrs = XNEWVEC (char *, attrnum);
 371
 372   attrnum = separate_attrs (attr_str, attrs, attrnum);
 373   if (attrnum == -1)
 374     {
 375       error_at (DECL_SOURCE_LOCATION (node->decl),
 376                 "default target was not set");
 377       XDELETEVEC (attrs);
 378       XDELETEVEC (attr_str);
 379       return false;
 380     }
 381   else if (attrnum == -2)
 382     {
 383       error_at (DECL_SOURCE_LOCATION (node->decl),
 384                 "an empty string cannot be in %<target_clones%> attribute");
 385       XDELETEVEC (attrs);
 386       XDELETEVEC (attr_str);
 387       return false;
 388     }
 389
 390   cgraph_function_version_info *decl1_v = NULL;
 391   cgraph_function_version_info *decl2_v = NULL;
 392   cgraph_function_version_info *before = NULL;
 393   cgraph_function_version_info *after = NULL;
 394   decl1_v = node->function_version ();
 395   if (decl1_v == NULL)
 396     decl1_v = node->insert_new_function_version ();
 397   before = decl1_v;
 398   DECL_FUNCTION_VERSIONED (node->decl) = 1;
 399
 400   for (i = 0; i < attrnum; i++)
 401     {
 402       char *attr = attrs[i];
 403       char *suffix = XNEWVEC (char, strlen (attr) + 1);
 404
 405       create_new_asm_name (attr, suffix);
 406       /* Create new target clone.  */
 407       tree attributes = make_attribute ("target", attr,
 408                                         DECL_ATTRIBUTES (node->decl));
 409
 410       cgraph_node *new_node = create_target_clone (node, definition, suffix,
 411                                                    attributes);
 412       if (new_node == NULL)
 413         return false;
 414       new_node->local.local = false;
 415       XDELETEVEC (suffix);
 416
 417       decl2_v = new_node->function_version ();
 418       if (decl2_v != NULL)
 419         continue;
 420       decl2_v = new_node->insert_new_function_version ();
 421
 422       /* Chain decl2_v and decl1_v.  All semantically identical versions
 423          will be chained together.  */
 424       after = decl2_v;
 425       while (before->next != NULL)
 426         before = before->next;
 427       while (after->prev != NULL)
 428         after = after->prev;
 429
 430       before->next = after;
 431       after->prev = before;
 432       DECL_FUNCTION_VERSIONED (new_node->decl) = 1;
 433     }
 434
 435   XDELETEVEC (attrs);
 436   XDELETEVEC (attr_str);
 437
 438   /* Setting new attribute to initial function.  */
 439   tree attributes = make_attribute ("target", "default",
 440                                     DECL_ATTRIBUTES (node->decl));
 441   DECL_ATTRIBUTES (node->decl) = attributes;
 442   node->local.local = false;
 443   return true;
 444 }
 445
 446 /* When NODE is a target clone, consider all callees and redirect
 447    to a clone with equal target attributes.  That prevents multiple
 448    multi-versioning dispatches and a call-chain can be optimized.  */
 449
 450 static void
 451 redirect_to_specific_clone (cgraph_node *node)
 452 {
 453   cgraph_function_version_info *fv = node->function_version ();
 454   if (fv == NULL)
 455     return;
 456
 457   tree attr_target = lookup_attribute ("target", DECL_ATTRIBUTES (node->decl));
 458   if (attr_target == NULL_TREE)
 459     return;
 460
 461   /* We need to remember NEXT_CALLER as it could be modified in the loop.  */
 462   for (cgraph_edge *e = node->callees; e ; e = e->next_callee)
 463     {
 464       cgraph_function_version_info *fv2 = e->callee->function_version ();
 465       if (!fv2)
 466         continue;
 467
 468       tree attr_target2 = lookup_attribute ("target",
 469                                             DECL_ATTRIBUTES (e->callee->decl));
 470
 471       /* Function is not calling proper target clone.  */
 472       if (!attribute_list_equal (attr_target, attr_target2))
 473         {
 474           while (fv2->prev != NULL)
 475             fv2 = fv2->prev;
 476
 477           /* Try to find a clone with equal target attribute.  */
 478           for (; fv2 != NULL; fv2 = fv2->next)
 479             {
 480               cgraph_node *callee = fv2->this_node;
 481               attr_target2 = lookup_attribute ("target",
 482                                                DECL_ATTRIBUTES (callee->decl));
 483               if (attribute_list_equal (attr_target, attr_target2))
 484                 {
 485                   e->redirect_callee (callee);
 486                   e->redirect_call_stmt_to_callee ();
 487                   break;
 488                 }
 489             }
 490         }
 491     }
 492 }
 493
 494 static unsigned int
 495 ipa_target_clone (void)
 496 {
 497   struct cgraph_node *node;
 498   auto_vec<cgraph_node *> to_dispatch;
 499
 500   FOR_EACH_FUNCTION (node)
 501     if (expand_target_clones (node, node->definition))
 502       to_dispatch.safe_push (node);
 503
 504   for (unsigned i = 0; i < to_dispatch.length (); i++)
 505     create_dispatcher_calls (to_dispatch[i]);
 506
 507   FOR_EACH_FUNCTION (node)
 508     redirect_to_specific_clone (node);
 509
 510   return 0;
 511 }
 512
 513 namespace {
 514
 515 const pass_data pass_data_target_clone =
 516 {
 517   SIMPLE_IPA_PASS,              /* type */
 518   "targetclone",                /* name */
 519   OPTGROUP_NONE,                /* optinfo_flags */
 520   TV_NONE,                      /* tv_id */
 521   ( PROP_ssa | PROP_cfg ),      /* properties_required */
 522   0,                            /* properties_provided */
 523   0,                            /* properties_destroyed */
 524   0,                            /* todo_flags_start */
 525   TODO_update_ssa               /* todo_flags_finish */
 526 };
 527
 528 class pass_target_clone : public simple_ipa_opt_pass
 529 {
 530 public:
 531   pass_target_clone (gcc::context *ctxt)
 532     : simple_ipa_opt_pass (pass_data_target_clone, ctxt)
 533   {}
 534
 535   /* opt_pass methods: */
 536   virtual bool gate (function *);
 537   virtual unsigned int execute (function *) { return ipa_target_clone (); }
 538 };
 539
 540 bool
 541 pass_target_clone::gate (function *)
 542 {
 543   return true;
 544 }
 545
 546 } // anon namespace
 547
 548 simple_ipa_opt_pass *
 549 make_pass_target_clone (gcc::context *ctxt)
 550 {
 551   return new pass_target_clone (ctxt);
 552 }