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   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 /* Return length of attribute names string,
 189    if arglist chain > 1, -1 otherwise.  */
 190
 191 static int
 192 get_attr_len (tree arglist)
 193 {
 194   tree arg;
 195   int 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       str_len_sum += len + 1;
 203       for (const char *p = strchr (str, ','); p; p = strchr (p + 1, ','))
 204         argnum++;
 205       argnum++;
 206     }
 207   if (argnum <= 1)
 208     return -1;
 209   return str_len_sum;
 210 }
 211
 212 /* Create string with attributes separated by comma.
 213    Return number of attributes.  */
 214
 215 static int
 216 get_attr_str (tree arglist, char *attr_str)
 217 {
 218   tree arg;
 219   size_t str_len_sum = 0;
 220   int argnum = 0;
 221
 222   for (arg = arglist; arg; arg = TREE_CHAIN (arg))
 223     {
 224       const char *str = TREE_STRING_POINTER (TREE_VALUE (arg));
 225       size_t len = strlen (str);
 226       for (const char *p = strchr (str, ','); p; p = strchr (p + 1, ','))
 227         argnum++;
 228       memcpy (attr_str + str_len_sum, str, len);
 229       attr_str[str_len_sum + len] = TREE_CHAIN (arg) ? ',' : '\0';
 230       str_len_sum += len + 1;
 231       argnum++;
 232     }
 233   return argnum;
 234 }
 235
 236 /* Return number of attributes separated by comma and put them into ARGS.
 237    If there is no DEFAULT attribute return -1.
 238    If there is an empty string in attribute return -2.
 239    If there are multiple DEFAULT attributes return -3.
 240    */
 241
 242 static int
 243 separate_attrs (char *attr_str, char **attrs, int attrnum)
 244 {
 245   int i = 0;
 246   int default_count = 0;
 247
 248   for (char *attr = strtok (attr_str, ",");
 249        attr != NULL; attr = strtok (NULL, ","))
 250     {
 251       if (strcmp (attr, "default") == 0)
 252         {
 253           default_count++;
 254           continue;
 255         }
 256       attrs[i++] = attr;
 257     }
 258   if (default_count == 0)
 259     return -1;
 260   else if (default_count > 1)
 261     return -3;
 262   else if (i + default_count < attrnum)
 263     return -2;
 264
 265   return i;
 266 }
 267
 268 /*  Return true if symbol is valid in assembler name.  */
 269
 270 static bool
 271 is_valid_asm_symbol (char c)
 272 {
 273   if ('a' <= c && c <= 'z')
 274     return true;
 275   if ('A' <= c && c <= 'Z')
 276     return true;
 277   if ('0' <= c && c <= '9')
 278     return true;
 279   if (c == '_')
 280     return true;
 281   return false;
 282 }
 283
 284 /*  Replace all not valid assembler symbols with '_'.  */
 285
 286 static void
 287 create_new_asm_name (char *old_asm_name, char *new_asm_name)
 288 {
 289   int i;
 290   int old_name_len = strlen (old_asm_name);
 291
 292   /* Replace all not valid assembler symbols with '_'.  */
 293   for (i = 0; i < old_name_len; i++)
 294     if (!is_valid_asm_symbol (old_asm_name[i]))
 295       new_asm_name[i] = '_';
 296     else
 297       new_asm_name[i] = old_asm_name[i];
 298   new_asm_name[old_name_len] = '\0';
 299 }
 300
 301 /*  Creates target clone of NODE.  */
 302
 303 static cgraph_node *
 304 create_target_clone (cgraph_node *node, bool definition, char *name,
 305                      tree attributes)
 306 {
 307   cgraph_node *new_node;
 308
 309   if (definition)
 310     {
 311       new_node
 312         = node->create_version_clone_with_body (vNULL, NULL, NULL, NULL, NULL,
 313                                                 name, attributes, false);
 314       if (new_node == NULL)
 315         return NULL;
 316       new_node->force_output = true;
 317     }
 318   else
 319     {
 320       tree new_decl = copy_node (node->decl);
 321       new_node = cgraph_node::get_create (new_decl);
 322       DECL_ATTRIBUTES (new_decl) = attributes;
 323       /* Generate a new name for the new version.  */
 324       tree fname = clone_function_name (node->decl, name);
 325       symtab->change_decl_assembler_name (new_node->decl, fname);
 326     }
 327   return new_node;
 328 }
 329
 330 /* If the function in NODE has multiple target attributes
 331    create the appropriate clone for each valid target attribute.  */
 332
 333 static bool
 334 expand_target_clones (struct cgraph_node *node, bool definition)
 335 {
 336   int i;
 337   /* Parsing target attributes separated by comma.  */
 338   tree attr_target = lookup_attribute ("target_clones",
 339                                        DECL_ATTRIBUTES (node->decl));
 340   /* No targets specified.  */
 341   if (!attr_target)
 342     return false;
 343
 344   tree arglist = TREE_VALUE (attr_target);
 345   int attr_len = get_attr_len (arglist);
 346
 347   /* No need to clone for 1 target attribute.  */
 348   if (attr_len == -1)
 349     {
 350       warning_at (DECL_SOURCE_LOCATION (node->decl),
 351                   0, "single %<target_clones%> attribute is ignored");
 352       return false;
 353     }
 354
 355   if (node->definition
 356       && (node->alias || !tree_versionable_function_p (node->decl)))
 357     {
 358       auto_diagnostic_group d;
 359       error_at (DECL_SOURCE_LOCATION (node->decl),
 360                 "clones for %<target_clones%> attribute cannot be created");
 361       const char *reason = NULL;
 362       if (lookup_attribute ("noclone", DECL_ATTRIBUTES (node->decl)))
 363         reason = G_("function %q+F can never be copied "
 364                     "because it has %<noclone%> attribute");
 365       else if (node->alias)
 366         reason
 367           = "%<target_clones%> cannot be combined with %<alias%> attribute";
 368       else
 369         reason = copy_forbidden (DECL_STRUCT_FUNCTION (node->decl));
 370       if (reason)
 371         inform (DECL_SOURCE_LOCATION (node->decl), reason, node->decl);
 372       return false;
 373     }
 374
 375   char *attr_str = XNEWVEC (char, attr_len);
 376   int attrnum = get_attr_str (arglist, attr_str);
 377   char **attrs = XNEWVEC (char *, attrnum);
 378
 379   attrnum = separate_attrs (attr_str, attrs, attrnum);
 380   switch (attrnum)
 381     {
 382     case -1:
 383       error_at (DECL_SOURCE_LOCATION (node->decl),
 384                 "%<default%> target was not set");
 385       break;
 386     case -2:
 387       error_at (DECL_SOURCE_LOCATION (node->decl),
 388                 "an empty string cannot be in %<target_clones%> attribute");
 389       break;
 390     case -3:
 391       error_at (DECL_SOURCE_LOCATION (node->decl),
 392                 "multiple %<default%> targets were set");
 393       break;
 394     default:
 395       break;
 396     }
 397
 398   if (attrnum < 0)
 399     {
 400       XDELETEVEC (attrs);
 401       XDELETEVEC (attr_str);
 402       return false;
 403     }
 404
 405   cgraph_function_version_info *decl1_v = NULL;
 406   cgraph_function_version_info *decl2_v = NULL;
 407   cgraph_function_version_info *before = NULL;
 408   cgraph_function_version_info *after = NULL;
 409   decl1_v = node->function_version ();
 410   if (decl1_v == NULL)
 411     decl1_v = node->insert_new_function_version ();
 412   before = decl1_v;
 413   DECL_FUNCTION_VERSIONED (node->decl) = 1;
 414
 415   for (i = 0; i < attrnum; i++)
 416     {
 417       char *attr = attrs[i];
 418       char *suffix = XNEWVEC (char, strlen (attr) + 1);
 419
 420       create_new_asm_name (attr, suffix);
 421       /* Create new target clone.  */
 422       tree attributes = make_attribute ("target", attr,
 423                                         DECL_ATTRIBUTES (node->decl));
 424
 425       cgraph_node *new_node = create_target_clone (node, definition, suffix,
 426                                                    attributes);
 427       if (new_node == NULL)
 428         return false;
 429       new_node->local = false;
 430       XDELETEVEC (suffix);
 431
 432       decl2_v = new_node->function_version ();
 433       if (decl2_v != NULL)
 434         continue;
 435       decl2_v = new_node->insert_new_function_version ();
 436
 437       /* Chain decl2_v and decl1_v.  All semantically identical versions
 438          will be chained together.  */
 439       after = decl2_v;
 440       while (before->next != NULL)
 441         before = before->next;
 442       while (after->prev != NULL)
 443         after = after->prev;
 444
 445       before->next = after;
 446       after->prev = before;
 447       DECL_FUNCTION_VERSIONED (new_node->decl) = 1;
 448     }
 449
 450   XDELETEVEC (attrs);
 451   XDELETEVEC (attr_str);
 452
 453   /* Setting new attribute to initial function.  */
 454   tree attributes = make_attribute ("target", "default",
 455                                     DECL_ATTRIBUTES (node->decl));
 456   DECL_ATTRIBUTES (node->decl) = attributes;
 457   node->local = false;
 458   return true;
 459 }
 460
 461 /* When NODE is a target clone, consider all callees and redirect
 462    to a clone with equal target attributes.  That prevents multiple
 463    multi-versioning dispatches and a call-chain can be optimized.  */
 464
 465 static void
 466 redirect_to_specific_clone (cgraph_node *node)
 467 {
 468   cgraph_function_version_info *fv = node->function_version ();
 469   if (fv == NULL)
 470     return;
 471
 472   tree attr_target = lookup_attribute ("target", DECL_ATTRIBUTES (node->decl));
 473   if (attr_target == NULL_TREE)
 474     return;
 475
 476   /* We need to remember NEXT_CALLER as it could be modified in the loop.  */
 477   for (cgraph_edge *e = node->callees; e ; e = e->next_callee)
 478     {
 479       cgraph_function_version_info *fv2 = e->callee->function_version ();
 480       if (!fv2)
 481         continue;
 482
 483       tree attr_target2 = lookup_attribute ("target",
 484                                             DECL_ATTRIBUTES (e->callee->decl));
 485
 486       /* Function is not calling proper target clone.  */
 487       if (attr_target2 == NULL_TREE
 488           || !attribute_value_equal (attr_target, attr_target2))
 489         {
 490           while (fv2->prev != NULL)
 491             fv2 = fv2->prev;
 492
 493           /* Try to find a clone with equal target attribute.  */
 494           for (; fv2 != NULL; fv2 = fv2->next)
 495             {
 496               cgraph_node *callee = fv2->this_node;
 497               attr_target2 = lookup_attribute ("target",
 498                                                DECL_ATTRIBUTES (callee->decl));
 499               if (attr_target2 != NULL_TREE
 500                   && attribute_value_equal (attr_target, attr_target2))
 501                 {
 502                   e->redirect_callee (callee);
 503                   cgraph_edge::redirect_call_stmt_to_callee (e);
 504                   break;
 505                 }
 506             }
 507         }
 508     }
 509 }
 510
 511 static unsigned int
 512 ipa_target_clone (void)
 513 {
 514   struct cgraph_node *node;
 515   auto_vec<cgraph_node *> to_dispatch;
 516
 517   FOR_EACH_FUNCTION (node)
 518     if (expand_target_clones (node, node->definition))
 519       to_dispatch.safe_push (node);
 520
 521   for (unsigned i = 0; i < to_dispatch.length (); i++)
 522     create_dispatcher_calls (to_dispatch[i]);
 523
 524   FOR_EACH_FUNCTION (node)
 525     redirect_to_specific_clone (node);
 526
 527   return 0;
 528 }
 529
 530 namespace {
 531
 532 const pass_data pass_data_target_clone =
 533 {
 534   SIMPLE_IPA_PASS,              /* type */
 535   "targetclone",                /* name */
 536   OPTGROUP_NONE,                /* optinfo_flags */
 537   TV_NONE,                      /* tv_id */
 538   ( PROP_ssa | PROP_cfg ),      /* properties_required */
 539   0,                            /* properties_provided */
 540   0,                            /* properties_destroyed */
 541   0,                            /* todo_flags_start */
 542   TODO_update_ssa               /* todo_flags_finish */
 543 };
 544
 545 class pass_target_clone : public simple_ipa_opt_pass
 546 {
 547 public:
 548   pass_target_clone (gcc::context *ctxt)
 549     : simple_ipa_opt_pass (pass_data_target_clone, ctxt)
 550   {}
 551
 552   /* opt_pass methods: */
 553   virtual bool gate (function *);
 554   virtual unsigned int execute (function *) { return ipa_target_clone (); }
 555 };
 556
 557 bool
 558 pass_target_clone::gate (function *)
 559 {
 560   return true;
 561 }
 562
 563 } // anon namespace
 564
 565 simple_ipa_opt_pass *
 566 make_pass_target_clone (gcc::context *ctxt)
 567 {
 568   return new pass_target_clone (ctxt);
 569 }