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) 2015-2021 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   /* We need to capture the references by value rather than just pointers to them
 107      and remove them right away, as removing them later would invalidate what
 108      some other reference pointers point to.  */
 109   auto_vec<ipa_ref> references_to_redirect;
 110
 111   while (node->iterate_referring (0, ref))
 112     {
 113       references_to_redirect.safe_push (*ref);
 114       ref->remove_reference ();
 115     }
 116
 117   /* We need to remember NEXT_CALLER as it could be modified in the loop.  */
 118   for (cgraph_edge *e = node->callers; e ; e = e->next_caller)
 119     edges_to_redirect.safe_push (e);
 120
 121   if (!edges_to_redirect.is_empty () || !references_to_redirect.is_empty ())
 122     {
 123       /* Redirect edges.  */
 124       unsigned i;
 125       cgraph_edge *e;
 126       FOR_EACH_VEC_ELT (edges_to_redirect, i, e)
 127         {
 128           e->redirect_callee (inode);
 129           cgraph_edge::redirect_call_stmt_to_callee (e);
 130         }
 131
 132       /* Redirect references.  */
 133       FOR_EACH_VEC_ELT (references_to_redirect, i, ref)
 134         {
 135           if (ref->use == IPA_REF_ADDR)
 136             {
 137               struct walk_stmt_info wi;
 138               memset (&wi, 0, sizeof (wi));
 139               wi.info = (void *)node->function_version ();
 140
 141               if (dyn_cast<varpool_node *> (ref->referring))
 142                 {
 143                   hash_set<tree> visited_nodes;
 144                   walk_tree (&DECL_INITIAL (ref->referring->decl),
 145                              replace_function_decl, &wi, &visited_nodes);
 146                 }
 147               else
 148                 {
 149                   gimple_stmt_iterator it = gsi_for_stmt (ref->stmt);
 150                   if (ref->referring->decl != resolver_decl)
 151                     walk_gimple_stmt (&it, NULL, replace_function_decl, &wi);
 152                 }
 153
 154               symtab_node *source = ref->referring;
 155               source->create_reference (inode, IPA_REF_ADDR);
 156             }
 157           else if (ref->use == IPA_REF_ALIAS)
 158             {
 159               symtab_node *source = ref->referring;
 160               source->create_reference (inode, IPA_REF_ALIAS);
 161               if (inode->get_comdat_group ())
 162                 source->add_to_same_comdat_group (inode);
 163             }
 164           else
 165             gcc_unreachable ();
 166         }
 167     }
 168
 169   symtab->change_decl_assembler_name (node->decl,
 170                                       clone_function_name_numbered (
 171                                           node->decl, "default"));
 172
 173   /* FIXME: copy of cgraph_node::make_local that should be cleaned up
 174             in next stage1.  */
 175   node->make_decl_local ();
 176   node->set_section (NULL);
 177   node->set_comdat_group (NULL);
 178   node->externally_visible = false;
 179   node->forced_by_abi = false;
 180   node->set_section (NULL);
 181
 182   DECL_ARTIFICIAL (node->decl) = 1;
 183   node->force_output = true;
 184 }
 185
 186 /* Return length of attribute names string,
 187    if arglist chain > 1, -1 otherwise.  */
 188
 189 static int
 190 get_attr_len (tree arglist)
 191 {
 192   tree arg;
 193   int str_len_sum = 0;
 194   int argnum = 0;
 195
 196   for (arg = arglist; arg; arg = TREE_CHAIN (arg))
 197     {
 198       const char *str = TREE_STRING_POINTER (TREE_VALUE (arg));
 199       size_t len = strlen (str);
 200       str_len_sum += len + 1;
 201       for (const char *p = strchr (str, ','); p; p = strchr (p + 1, ','))
 202         argnum++;
 203       argnum++;
 204     }
 205   if (argnum <= 1)
 206     return -1;
 207   return str_len_sum;
 208 }
 209
 210 /* Create string with attributes separated by comma.
 211    Return number of attributes.  */
 212
 213 static int
 214 get_attr_str (tree arglist, char *attr_str)
 215 {
 216   tree arg;
 217   size_t str_len_sum = 0;
 218   int argnum = 0;
 219
 220   for (arg = arglist; arg; arg = TREE_CHAIN (arg))
 221     {
 222       const char *str = TREE_STRING_POINTER (TREE_VALUE (arg));
 223       size_t len = strlen (str);
 224       for (const char *p = strchr (str, ','); p; p = strchr (p + 1, ','))
 225         argnum++;
 226       memcpy (attr_str + str_len_sum, str, len);
 227       attr_str[str_len_sum + len] = TREE_CHAIN (arg) ? ',' : '\0';
 228       str_len_sum += len + 1;
 229       argnum++;
 230     }
 231   return argnum;
 232 }
 233
 234 /* Return number of attributes separated by comma and put them into ARGS.
 235    If there is no DEFAULT attribute return -1.
 236    If there is an empty string in attribute return -2.
 237    If there are multiple DEFAULT attributes return -3.
 238    */
 239
 240 static int
 241 separate_attrs (char *attr_str, char **attrs, int attrnum)
 242 {
 243   int i = 0;
 244   int default_count = 0;
 245
 246   for (char *attr = strtok (attr_str, ",");
 247        attr != NULL; attr = strtok (NULL, ","))
 248     {
 249       if (strcmp (attr, "default") == 0)
 250         {
 251           default_count++;
 252           continue;
 253         }
 254       attrs[i++] = attr;
 255     }
 256   if (default_count == 0)
 257     return -1;
 258   else if (default_count > 1)
 259     return -3;
 260   else if (i + default_count < attrnum)
 261     return -2;
 262
 263   return i;
 264 }
 265
 266 /*  Return true if symbol is valid in assembler name.  */
 267
 268 static bool
 269 is_valid_asm_symbol (char c)
 270 {
 271   if ('a' <= c && c <= 'z')
 272     return true;
 273   if ('A' <= c && c <= 'Z')
 274     return true;
 275   if ('0' <= c && c <= '9')
 276     return true;
 277   if (c == '_')
 278     return true;
 279   return false;
 280 }
 281
 282 /*  Replace all not valid assembler symbols with '_'.  */
 283
 284 static void
 285 create_new_asm_name (char *old_asm_name, char *new_asm_name)
 286 {
 287   int i;
 288   int old_name_len = strlen (old_asm_name);
 289
 290   /* Replace all not valid assembler symbols with '_'.  */
 291   for (i = 0; i < old_name_len; i++)
 292     if (!is_valid_asm_symbol (old_asm_name[i]))
 293       new_asm_name[i] = '_';
 294     else
 295       new_asm_name[i] = old_asm_name[i];
 296   new_asm_name[old_name_len] = '\0';
 297 }
 298
 299 /*  Creates target clone of NODE.  */
 300
 301 static cgraph_node *
 302 create_target_clone (cgraph_node *node, bool definition, char *name,
 303                      tree attributes)
 304 {
 305   cgraph_node *new_node;
 306
 307   if (definition)
 308     {
 309       new_node = node->create_version_clone_with_body (vNULL, NULL,
 310                                                        NULL, NULL,
 311                                                        NULL, name, attributes);
 312       if (new_node == NULL)
 313         return NULL;
 314       new_node->force_output = true;
 315     }
 316   else
 317     {
 318       tree new_decl = copy_node (node->decl);
 319       new_node = cgraph_node::get_create (new_decl);
 320       DECL_ATTRIBUTES (new_decl) = attributes;
 321       /* Generate a new name for the new version.  */
 322       symtab->change_decl_assembler_name (new_node->decl,
 323                                           clone_function_name_numbered (
 324                                               node->decl, name));
 325     }
 326   return new_node;
 327 }
 328
 329 /* If the function in NODE has multiple target attributes
 330    create the appropriate clone for each valid target attribute.  */
 331
 332 static bool
 333 expand_target_clones (struct cgraph_node *node, bool definition)
 334 {
 335   int i;
 336   /* Parsing target attributes separated by comma.  */
 337   tree attr_target = lookup_attribute ("target_clones",
 338                                        DECL_ATTRIBUTES (node->decl));
 339   /* No targets specified.  */
 340   if (!attr_target)
 341     return false;
 342
 343   tree arglist = TREE_VALUE (attr_target);
 344   int attr_len = get_attr_len (arglist);
 345
 346   /* No need to clone for 1 target attribute.  */
 347   if (attr_len == -1)
 348     {
 349       warning_at (DECL_SOURCE_LOCATION (node->decl),
 350                   0, "single %<target_clones%> attribute is ignored");
 351       return false;
 352     }
 353
 354   if (node->definition
 355       && (node->alias || !tree_versionable_function_p (node->decl)))
 356     {
 357       auto_diagnostic_group d;
 358       error_at (DECL_SOURCE_LOCATION (node->decl),
 359                 "clones for %<target_clones%> attribute cannot be created");
 360       const char *reason = NULL;
 361       if (lookup_attribute ("noclone", DECL_ATTRIBUTES (node->decl)))
 362         reason = G_("function %q+F can never be copied "
 363                     "because it has %<noclone%> attribute");
 364       else if (node->alias)
 365         reason
 366           = "%<target_clones%> cannot be combined with %<alias%> attribute";
 367       else
 368         reason = copy_forbidden (DECL_STRUCT_FUNCTION (node->decl));
 369       if (reason)
 370         inform (DECL_SOURCE_LOCATION (node->decl), reason, node->decl);
 371       return false;
 372     }
 373
 374   char *attr_str = XNEWVEC (char, attr_len);
 375   int attrnum = get_attr_str (arglist, attr_str);
 376   char **attrs = XNEWVEC (char *, attrnum);
 377
 378   attrnum = separate_attrs (attr_str, attrs, attrnum);
 379   switch (attrnum)
 380     {
 381     case -1:
 382       error_at (DECL_SOURCE_LOCATION (node->decl),
 383                 "%<default%> target was not set");
 384       break;
 385     case -2:
 386       error_at (DECL_SOURCE_LOCATION (node->decl),
 387                 "an empty string cannot be in %<target_clones%> attribute");
 388       break;
 389     case -3:
 390       error_at (DECL_SOURCE_LOCATION (node->decl),
 391                 "multiple %<default%> targets were set");
 392       break;
 393     default:
 394       break;
 395     }
 396
 397   if (attrnum < 0)
 398     {
 399       XDELETEVEC (attrs);
 400       XDELETEVEC (attr_str);
 401       return false;
 402     }
 403
 404   cgraph_function_version_info *decl1_v = NULL;
 405   cgraph_function_version_info *decl2_v = NULL;
 406   cgraph_function_version_info *before = NULL;
 407   cgraph_function_version_info *after = NULL;
 408   decl1_v = node->function_version ();
 409   if (decl1_v == NULL)
 410     decl1_v = node->insert_new_function_version ();
 411   before = decl1_v;
 412   DECL_FUNCTION_VERSIONED (node->decl) = 1;
 413
 414   for (i = 0; i < attrnum; i++)
 415     {
 416       char *attr = attrs[i];
 417       char *suffix = XNEWVEC (char, strlen (attr) + 1);
 418
 419       create_new_asm_name (attr, suffix);
 420       /* Create new target clone.  */
 421       tree attributes = make_attribute ("target", attr,
 422                                         DECL_ATTRIBUTES (node->decl));
 423
 424       cgraph_node *new_node = create_target_clone (node, definition, suffix,
 425                                                    attributes);
 426       if (new_node == NULL)
 427         return false;
 428       new_node->local = false;
 429       XDELETEVEC (suffix);
 430
 431       decl2_v = new_node->function_version ();
 432       if (decl2_v != NULL)
 433         continue;
 434       decl2_v = new_node->insert_new_function_version ();
 435
 436       /* Chain decl2_v and decl1_v.  All semantically identical versions
 437          will be chained together.  */
 438       after = decl2_v;
 439       while (before->next != NULL)
 440         before = before->next;
 441       while (after->prev != NULL)
 442         after = after->prev;
 443
 444       before->next = after;
 445       after->prev = before;
 446       DECL_FUNCTION_VERSIONED (new_node->decl) = 1;
 447     }
 448
 449   XDELETEVEC (attrs);
 450   XDELETEVEC (attr_str);
 451
 452   /* Setting new attribute to initial function.  */
 453   tree attributes = make_attribute ("target", "default",
 454                                     DECL_ATTRIBUTES (node->decl));
 455   DECL_ATTRIBUTES (node->decl) = attributes;
 456   node->local = false;
 457   return true;
 458 }
 459
 460 /* When NODE is a target clone, consider all callees and redirect
 461    to a clone with equal target attributes.  That prevents multiple
 462    multi-versioning dispatches and a call-chain can be optimized.  */
 463
 464 static void
 465 redirect_to_specific_clone (cgraph_node *node)
 466 {
 467   cgraph_function_version_info *fv = node->function_version ();
 468   if (fv == NULL)
 469     return;
 470
 471   tree attr_target = lookup_attribute ("target", DECL_ATTRIBUTES (node->decl));
 472   if (attr_target == NULL_TREE)
 473     return;
 474
 475   /* We need to remember NEXT_CALLER as it could be modified in the loop.  */
 476   for (cgraph_edge *e = node->callees; e ; e = e->next_callee)
 477     {
 478       cgraph_function_version_info *fv2 = e->callee->function_version ();
 479       if (!fv2)
 480         continue;
 481
 482       tree attr_target2 = lookup_attribute ("target",
 483                                             DECL_ATTRIBUTES (e->callee->decl));
 484
 485       /* Function is not calling proper target clone.  */
 486       if (attr_target2 == NULL_TREE
 487           || !attribute_value_equal (attr_target, attr_target2))
 488         {
 489           while (fv2->prev != NULL)
 490             fv2 = fv2->prev;
 491
 492           /* Try to find a clone with equal target attribute.  */
 493           for (; fv2 != NULL; fv2 = fv2->next)
 494             {
 495               cgraph_node *callee = fv2->this_node;
 496               attr_target2 = lookup_attribute ("target",
 497                                                DECL_ATTRIBUTES (callee->decl));
 498               if (attr_target2 != NULL_TREE
 499                   && attribute_value_equal (attr_target, attr_target2))
 500                 {
 501                   e->redirect_callee (callee);
 502                   cgraph_edge::redirect_call_stmt_to_callee (e);
 503                   break;
 504                 }
 505             }
 506         }
 507     }
 508 }
 509
 510 static unsigned int
 511 ipa_target_clone (void)
 512 {
 513   struct cgraph_node *node;
 514   auto_vec<cgraph_node *> to_dispatch;
 515
 516   FOR_EACH_FUNCTION (node)
 517     if (expand_target_clones (node, node->definition))
 518       to_dispatch.safe_push (node);
 519
 520   for (unsigned i = 0; i < to_dispatch.length (); i++)
 521     create_dispatcher_calls (to_dispatch[i]);
 522
 523   FOR_EACH_FUNCTION (node)
 524     redirect_to_specific_clone (node);
 525
 526   return 0;
 527 }
 528
 529 namespace {
 530
 531 const pass_data pass_data_target_clone =
 532 {
 533   SIMPLE_IPA_PASS,              /* type */
 534   "targetclone",                /* name */
 535   OPTGROUP_NONE,                /* optinfo_flags */
 536   TV_NONE,                      /* tv_id */
 537   ( PROP_ssa | PROP_cfg ),      /* properties_required */
 538   0,                            /* properties_provided */
 539   0,                            /* properties_destroyed */
 540   0,                            /* todo_flags_start */
 541   TODO_update_ssa               /* todo_flags_finish */
 542 };
 543
 544 class pass_target_clone : public simple_ipa_opt_pass
 545 {
 546 public:
 547   pass_target_clone (gcc::context *ctxt)
 548     : simple_ipa_opt_pass (pass_data_target_clone, ctxt)
 549   {}
 550
 551   /* opt_pass methods: */
 552   virtual bool gate (function *);
 553   virtual unsigned int execute (function *) { return ipa_target_clone (); }
 554 };
 555
 556 bool
 557 pass_target_clone::gate (function *)
 558 {
 559   return true;
 560 }
 561
 562 } // anon namespace
 563
 564 simple_ipa_opt_pass *
 565 make_pass_target_clone (gcc::context *ctxt)
 566 {
 567   return new pass_target_clone (ctxt);
 568 }