gcc/multiple_target.cc

   1 /* Pass for parsing functions with multiple target attributes.
   2
   3    Contributed by Evgeny Stupachenko <evstupac@gmail.com>
   4
   5    Copyright (C) 2015-2022 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   tree fname = clone_function_name (node->decl, "default");
 170   symtab->change_decl_assembler_name (node->decl, fname);
 171
 172   if (node->definition)
 173     {
 174       /* FIXME: copy of cgraph_node::make_local that should be cleaned up
 175                 in next stage1.  */
 176       node->make_decl_local ();
 177       node->set_section (NULL);
 178       node->set_comdat_group (NULL);
 179       node->externally_visible = false;
 180       node->forced_by_abi = false;
 181       node->set_section (NULL);
 182
 183       DECL_ARTIFICIAL (node->decl) = 1;
 184       node->force_output = true;
 185     }
 186 }
 187
 188 /* Create string with attributes separated by comma.
 189    Return number of attributes.  */
 190
 191 static int
 192 get_attr_str (tree arglist, char *attr_str)
 193 {
 194   tree arg;
 195   size_t str_len_sum = 0;
 196   int argnum = 0;
 197
 198   for (arg = arglist; arg; arg = TREE_CHAIN (arg))
 199     {
 200       const char *str = TREE_STRING_POINTER (TREE_VALUE (arg));
 201       size_t len = strlen (str);
 202       for (const char *p = strchr (str, ','); p; p = strchr (p + 1, ','))
 203         argnum++;
 204       memcpy (attr_str + str_len_sum, str, len);
 205       attr_str[str_len_sum + len] = TREE_CHAIN (arg) ? ',' : '\0';
 206       str_len_sum += len + 1;
 207       argnum++;
 208     }
 209   return argnum;
 210 }
 211
 212 /* Return number of attributes separated by comma and put them into ARGS.
 213    If there is no DEFAULT attribute return -1.
 214    If there is an empty string in attribute return -2.
 215    If there are multiple DEFAULT attributes return -3.
 216    */
 217
 218 static int
 219 separate_attrs (char *attr_str, char **attrs, int attrnum)
 220 {
 221   int i = 0;
 222   int default_count = 0;
 223
 224   for (char *attr = strtok (attr_str, ",");
 225        attr != NULL; attr = strtok (NULL, ","))
 226     {
 227       if (strcmp (attr, "default") == 0)
 228         {
 229           default_count++;
 230           continue;
 231         }
 232       attrs[i++] = attr;
 233     }
 234   if (default_count == 0)
 235     return -1;
 236   else if (default_count > 1)
 237     return -3;
 238   else if (i + default_count < attrnum)
 239     return -2;
 240
 241   return i;
 242 }
 243
 244 /*  Return true if symbol is valid in assembler name.  */
 245
 246 static bool
 247 is_valid_asm_symbol (char c)
 248 {
 249   if ('a' <= c && c <= 'z')
 250     return true;
 251   if ('A' <= c && c <= 'Z')
 252     return true;
 253   if ('0' <= c && c <= '9')
 254     return true;
 255   if (c == '_')
 256     return true;
 257   return false;
 258 }
 259
 260 /*  Replace all not valid assembler symbols with '_'.  */
 261
 262 static void
 263 create_new_asm_name (char *old_asm_name, char *new_asm_name)
 264 {
 265   int i;
 266   int old_name_len = strlen (old_asm_name);
 267
 268   /* Replace all not valid assembler symbols with '_'.  */
 269   for (i = 0; i < old_name_len; i++)
 270     if (!is_valid_asm_symbol (old_asm_name[i]))
 271       new_asm_name[i] = '_';
 272     else
 273       new_asm_name[i] = old_asm_name[i];
 274   new_asm_name[old_name_len] = '\0';
 275 }
 276
 277 /*  Creates target clone of NODE.  */
 278
 279 static cgraph_node *
 280 create_target_clone (cgraph_node *node, bool definition, char *name,
 281                      tree attributes)
 282 {
 283   cgraph_node *new_node;
 284
 285   if (definition)
 286     {
 287       new_node
 288         = node->create_version_clone_with_body (vNULL, NULL, NULL, NULL, NULL,
 289                                                 name, attributes, false);
 290       if (new_node == NULL)
 291         return NULL;
 292       new_node->force_output = true;
 293     }
 294   else
 295     {
 296       tree new_decl = copy_node (node->decl);
 297       new_node = cgraph_node::get_create (new_decl);
 298       DECL_ATTRIBUTES (new_decl) = attributes;
 299       /* Generate a new name for the new version.  */
 300       tree fname = clone_function_name (node->decl, name);
 301       symtab->change_decl_assembler_name (new_node->decl, fname);
 302     }
 303   return new_node;
 304 }
 305
 306 /* If the function in NODE has multiple target attributes
 307    create the appropriate clone for each valid target attribute.  */
 308
 309 static bool
 310 expand_target_clones (struct cgraph_node *node, bool definition)
 311 {
 312   int i;
 313   /* Parsing target attributes separated by comma.  */
 314   tree attr_target = lookup_attribute ("target_clones",
 315                                        DECL_ATTRIBUTES (node->decl));
 316   /* No targets specified.  */
 317   if (!attr_target)
 318     return false;
 319
 320   tree arglist = TREE_VALUE (attr_target);
 321   int attr_len = get_target_clone_attr_len (arglist);
 322
 323   /* No need to clone for 1 target attribute.  */
 324   if (attr_len == -1)
 325     {
 326       warning_at (DECL_SOURCE_LOCATION (node->decl),
 327                   0, "single %<target_clones%> attribute is ignored");
 328       return false;
 329     }
 330
 331   if (node->definition
 332       && (node->alias || !tree_versionable_function_p (node->decl)))
 333     {
 334       auto_diagnostic_group d;
 335       error_at (DECL_SOURCE_LOCATION (node->decl),
 336                 "clones for %<target_clones%> attribute cannot be created");
 337       const char *reason = NULL;
 338       if (lookup_attribute ("noclone", DECL_ATTRIBUTES (node->decl)))
 339         reason = G_("function %q+F can never be copied "
 340                     "because it has %<noclone%> attribute");
 341       else if (node->alias)
 342         reason
 343           = "%<target_clones%> cannot be combined with %<alias%> attribute";
 344       else
 345         reason = copy_forbidden (DECL_STRUCT_FUNCTION (node->decl));
 346       if (reason)
 347         inform (DECL_SOURCE_LOCATION (node->decl), reason, node->decl);
 348       return false;
 349     }
 350
 351   char *attr_str = XNEWVEC (char, attr_len);
 352   int attrnum = get_attr_str (arglist, attr_str);
 353   char **attrs = XNEWVEC (char *, attrnum);
 354
 355   attrnum = separate_attrs (attr_str, attrs, attrnum);
 356   switch (attrnum)
 357     {
 358     case -1:
 359       error_at (DECL_SOURCE_LOCATION (node->decl),
 360                 "%<default%> target was not set");
 361       break;
 362     case -2:
 363       error_at (DECL_SOURCE_LOCATION (node->decl),
 364                 "an empty string cannot be in %<target_clones%> attribute");
 365       break;
 366     case -3:
 367       error_at (DECL_SOURCE_LOCATION (node->decl),
 368                 "multiple %<default%> targets were set");
 369       break;
 370     default:
 371       break;
 372     }
 373
 374   if (attrnum < 0)
 375     {
 376       XDELETEVEC (attrs);
 377       XDELETEVEC (attr_str);
 378       return false;
 379     }
 380
 381   cgraph_function_version_info *decl1_v = NULL;
 382   cgraph_function_version_info *decl2_v = NULL;
 383   cgraph_function_version_info *before = NULL;
 384   cgraph_function_version_info *after = NULL;
 385   decl1_v = node->function_version ();
 386   if (decl1_v == NULL)
 387     decl1_v = node->insert_new_function_version ();
 388   before = decl1_v;
 389   DECL_FUNCTION_VERSIONED (node->decl) = 1;
 390
 391   for (i = 0; i < attrnum; i++)
 392     {
 393       char *attr = attrs[i];
 394       char *suffix = XNEWVEC (char, strlen (attr) + 1);
 395
 396       create_new_asm_name (attr, suffix);
 397       /* Create new target clone.  */
 398       tree attributes = make_attribute ("target", attr,
 399                                         DECL_ATTRIBUTES (node->decl));
 400
 401       cgraph_node *new_node = create_target_clone (node, definition, suffix,
 402                                                    attributes);
 403       if (new_node == NULL)
 404         return false;
 405       new_node->local = false;
 406       XDELETEVEC (suffix);
 407
 408       decl2_v = new_node->function_version ();
 409       if (decl2_v != NULL)
 410         continue;
 411       decl2_v = new_node->insert_new_function_version ();
 412
 413       /* Chain decl2_v and decl1_v.  All semantically identical versions
 414          will be chained together.  */
 415       after = decl2_v;
 416       while (before->next != NULL)
 417         before = before->next;
 418       while (after->prev != NULL)
 419         after = after->prev;
 420
 421       before->next = after;
 422       after->prev = before;
 423       DECL_FUNCTION_VERSIONED (new_node->decl) = 1;
 424     }
 425
 426   XDELETEVEC (attrs);
 427   XDELETEVEC (attr_str);
 428
 429   /* Setting new attribute to initial function.  */
 430   tree attributes = make_attribute ("target", "default",
 431                                     DECL_ATTRIBUTES (node->decl));
 432   DECL_ATTRIBUTES (node->decl) = attributes;
 433   node->local = false;
 434   return true;
 435 }
 436
 437 /* When NODE is a target clone, consider all callees and redirect
 438    to a clone with equal target attributes.  That prevents multiple
 439    multi-versioning dispatches and a call-chain can be optimized.  */
 440
 441 static void
 442 redirect_to_specific_clone (cgraph_node *node)
 443 {
 444   cgraph_function_version_info *fv = node->function_version ();
 445   if (fv == NULL)
 446     return;
 447
 448   tree attr_target = lookup_attribute ("target", DECL_ATTRIBUTES (node->decl));
 449   if (attr_target == NULL_TREE)
 450     return;
 451
 452   /* We need to remember NEXT_CALLER as it could be modified in the loop.  */
 453   for (cgraph_edge *e = node->callees; e ; e = e->next_callee)
 454     {
 455       cgraph_function_version_info *fv2 = e->callee->function_version ();
 456       if (!fv2)
 457         continue;
 458
 459       tree attr_target2 = lookup_attribute ("target",
 460                                             DECL_ATTRIBUTES (e->callee->decl));
 461
 462       /* Function is not calling proper target clone.  */
 463       if (attr_target2 == NULL_TREE
 464           || !attribute_value_equal (attr_target, attr_target2))
 465         {
 466           while (fv2->prev != NULL)
 467             fv2 = fv2->prev;
 468
 469           /* Try to find a clone with equal target attribute.  */
 470           for (; fv2 != NULL; fv2 = fv2->next)
 471             {
 472               cgraph_node *callee = fv2->this_node;
 473               attr_target2 = lookup_attribute ("target",
 474                                                DECL_ATTRIBUTES (callee->decl));
 475               if (attr_target2 != NULL_TREE
 476                   && attribute_value_equal (attr_target, attr_target2))
 477                 {
 478                   e->redirect_callee (callee);
 479                   cgraph_edge::redirect_call_stmt_to_callee (e);
 480                   break;
 481                 }
 482             }
 483         }
 484     }
 485 }
 486
 487 static unsigned int
 488 ipa_target_clone (void)
 489 {
 490   struct cgraph_node *node;
 491   auto_vec<cgraph_node *> to_dispatch;
 492
 493   FOR_EACH_FUNCTION (node)
 494     if (expand_target_clones (node, node->definition))
 495       to_dispatch.safe_push (node);
 496
 497   for (unsigned i = 0; i < to_dispatch.length (); i++)
 498     create_dispatcher_calls (to_dispatch[i]);
 499
 500   FOR_EACH_FUNCTION (node)
 501     redirect_to_specific_clone (node);
 502
 503   return 0;
 504 }
 505
 506 namespace {
 507
 508 const pass_data pass_data_target_clone =
 509 {
 510   SIMPLE_IPA_PASS,              /* type */
 511   "targetclone",                /* name */
 512   OPTGROUP_NONE,                /* optinfo_flags */
 513   TV_NONE,                      /* tv_id */
 514   ( PROP_ssa | PROP_cfg ),      /* properties_required */
 515   0,                            /* properties_provided */
 516   0,                            /* properties_destroyed */
 517   0,                            /* todo_flags_start */
 518   TODO_update_ssa               /* todo_flags_finish */
 519 };
 520
 521 class pass_target_clone : public simple_ipa_opt_pass
 522 {
 523 public:
 524   pass_target_clone (gcc::context *ctxt)
 525     : simple_ipa_opt_pass (pass_data_target_clone, ctxt)
 526   {}
 527
 528   /* opt_pass methods: */
 529   bool gate (function *) final override;
 530   unsigned int execute (function *) final override
 531   {
 532     return ipa_target_clone ();
 533   }
 534 };
 535
 536 bool
 537 pass_target_clone::gate (function *)
 538 {
 539   return true;
 540 }
 541
 542 } // anon namespace
 543
 544 simple_ipa_opt_pass *
 545 make_pass_target_clone (gcc::context *ctxt)
 546 {
 547   return new pass_target_clone (ctxt);
 548 }