gcc/gcc/multiple_target.c

/* Pass for parsing functions with multiple target attributes.

   Contributed by Evgeny Stupachenko <evstupac@gmail.com>

   Copyright (C) 2015-2019 Free Software Foundation, Inc.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "backend.h"
#include "tree.h"
#include "stringpool.h"
#include "gimple.h"
#include "diagnostic-core.h"
#include "gimple-ssa.h"
#include "cgraph.h"
#include "tree-pass.h"
#include "target.h"
#include "attribs.h"
#include "pretty-print.h"
#include "gimple-iterator.h"
#include "gimple-walk.h"
#include "tree-inline.h"
#include "intl.h"

/* Walker callback that replaces all FUNCTION_DECL of a function that's
   going to be versioned.  */

static tree
replace_function_decl (tree *op, int *walk_subtrees, void *data)
{
  struct walk_stmt_info *wi = (struct walk_stmt_info *) data;
  cgraph_function_version_info *info = (cgraph_function_version_info *)wi->info;

  if (TREE_CODE (*op) == FUNCTION_DECL
      && info->this_node->decl == *op)
    {
      *op = info->dispatcher_resolver;
      *walk_subtrees = 0;
    }

  return NULL;
}

/* If the call in NODE has multiple target attribute with multiple fields,
   replace it with dispatcher call and create dispatcher (once).  */

static void
create_dispatcher_calls (struct cgraph_node *node)
{
  ipa_ref *ref;

  if (!DECL_FUNCTION_VERSIONED (node->decl)
      || !is_function_default_version (node->decl))
    return;

  if (!targetm.has_ifunc_p ())
    {
      error_at (DECL_SOURCE_LOCATION (node->decl),
		"the call requires ifunc, which is not"
		" supported by this target");
      return;
    }
  else if (!targetm.get_function_versions_dispatcher)
    {
      error_at (DECL_SOURCE_LOCATION (node->decl),
		"target does not support function version dispatcher");
      return;
    }

  tree idecl = targetm.get_function_versions_dispatcher (node->decl);
  if (!idecl)
    {
      error_at (DECL_SOURCE_LOCATION (node->decl),
		"default %<target_clones%> attribute was not set");
      return;
    }

  cgraph_node *inode = cgraph_node::get (idecl);
  gcc_assert (inode);
  tree resolver_decl = targetm.generate_version_dispatcher_body (inode);

  /* Update aliases.  */
  inode->alias = true;
  inode->alias_target = resolver_decl;
  if (!inode->analyzed)
    inode->resolve_alias (cgraph_node::get (resolver_decl));

  auto_vec<cgraph_edge *> edges_to_redirect;
  auto_vec<ipa_ref *> references_to_redirect;

  for (unsigned i = 0; node->iterate_referring (i, ref); i++)
    references_to_redirect.safe_push (ref);

  /* We need to remember NEXT_CALLER as it could be modified in the loop.  */
  for (cgraph_edge *e = node->callers; e ; e = e->next_caller)
    edges_to_redirect.safe_push (e);

  if (!edges_to_redirect.is_empty () || !references_to_redirect.is_empty ())
    {
      /* Redirect edges.  */
      unsigned i;
      cgraph_edge *e;
      FOR_EACH_VEC_ELT (edges_to_redirect, i, e)
	{
	  e->redirect_callee (inode);
	  e->redirect_call_stmt_to_callee ();
	}

      /* Redirect references.  */
      FOR_EACH_VEC_ELT (references_to_redirect, i, ref)
	{
	  if (ref->use == IPA_REF_ADDR)
	    {
	      struct walk_stmt_info wi;
	      memset (&wi, 0, sizeof (wi));
	      wi.info = (void *)node->function_version ();

	      if (dyn_cast<varpool_node *> (ref->referring))
		{
		  hash_set<tree> visited_nodes;
		  walk_tree (&DECL_INITIAL (ref->referring->decl),
			     replace_function_decl, &wi, &visited_nodes);
		}
	      else
		{
		  gimple_stmt_iterator it = gsi_for_stmt (ref->stmt);
		  if (ref->referring->decl != resolver_decl)
		    walk_gimple_stmt (&it, NULL, replace_function_decl, &wi);
		}

	      symtab_node *source = ref->referring;
	      ref->remove_reference ();
	      source->create_reference (inode, IPA_REF_ADDR);
	    }
	  else if (ref->use == IPA_REF_ALIAS)
	    {
	      symtab_node *source = ref->referring;
	      ref->remove_reference ();
	      source->create_reference (inode, IPA_REF_ALIAS);
	      source->add_to_same_comdat_group (inode);
	    }
	  else
	    gcc_unreachable ();
	}
    }

  symtab->change_decl_assembler_name (node->decl,
				      clone_function_name_numbered (
					  node->decl, "default"));

  /* FIXME: copy of cgraph_node::make_local that should be cleaned up
	    in next stage1.  */
  node->make_decl_local ();
  node->set_section (NULL);
  node->set_comdat_group (NULL);
  node->externally_visible = false;
  node->forced_by_abi = false;
  node->set_section (NULL);
  node->unique_name = ((node->resolution == LDPR_PREVAILING_DEF_IRONLY
			|| node->resolution == LDPR_PREVAILING_DEF_IRONLY_EXP)
		       && !flag_incremental_link);
  node->resolution = LDPR_PREVAILING_DEF_IRONLY;

  DECL_ARTIFICIAL (node->decl) = 1;
  node->force_output = true;
}

/* Return length of attribute names string,
   if arglist chain > 1, -1 otherwise.  */

static int
get_attr_len (tree arglist)
{
  tree arg;
  int str_len_sum = 0;
  int argnum = 0;

  for (arg = arglist; arg; arg = TREE_CHAIN (arg))
    {
      const char *str = TREE_STRING_POINTER (TREE_VALUE (arg));
      size_t len = strlen (str);
      str_len_sum += len + 1;
      for (const char *p = strchr (str, ','); p; p = strchr (p + 1, ','))
	argnum++;
      argnum++;
    }
  if (argnum <= 1)
    return -1;
  return str_len_sum;
}

/* Create string with attributes separated by comma.
   Return number of attributes.  */

static int
get_attr_str (tree arglist, char *attr_str)
{
  tree arg;
  size_t str_len_sum = 0;
  int argnum = 0;

  for (arg = arglist; arg; arg = TREE_CHAIN (arg))
    {
      const char *str = TREE_STRING_POINTER (TREE_VALUE (arg));
      size_t len = strlen (str);
      for (const char *p = strchr (str, ','); p; p = strchr (p + 1, ','))
	argnum++;
      memcpy (attr_str + str_len_sum, str, len);
      attr_str[str_len_sum + len] = TREE_CHAIN (arg) ? ',' : '\0';
      str_len_sum += len + 1;
      argnum++;
    }
  return argnum;
}

/* Return number of attributes separated by comma and put them into ARGS.
   If there is no DEFAULT attribute return -1.  If there is an empty
   string in attribute return -2.  */

static int
separate_attrs (char *attr_str, char **attrs, int attrnum)
{
  int i = 0;
  int default_count = 0;

  for (char *attr = strtok (attr_str, ",");
       attr != NULL; attr = strtok (NULL, ","))
    {
      if (strcmp (attr, "default") == 0)
	{
	  default_count++;
	  continue;
	}
      attrs[i++] = attr;
    }
  if (default_count == 0)
    return -1;
  else if (i + default_count < attrnum)
    return -2;

  return i;
}

/*  Return true if symbol is valid in assembler name.  */

static bool
is_valid_asm_symbol (char c)
{
  if ('a' <= c && c <= 'z')
    return true;
  if ('A' <= c && c <= 'Z')
    return true;
  if ('0' <= c && c <= '9')
    return true;
  if (c == '_')
    return true;
  return false;
}

/*  Replace all not valid assembler symbols with '_'.  */

static void
create_new_asm_name (char *old_asm_name, char *new_asm_name)
{
  int i;
  int old_name_len = strlen (old_asm_name);

  /* Replace all not valid assembler symbols with '_'.  */
  for (i = 0; i < old_name_len; i++)
    if (!is_valid_asm_symbol (old_asm_name[i]))
      new_asm_name[i] = '_';
    else
      new_asm_name[i] = old_asm_name[i];
  new_asm_name[old_name_len] = '\0';
}

/*  Creates target clone of NODE.  */

static cgraph_node *
create_target_clone (cgraph_node *node, bool definition, char *name)
{
  cgraph_node *new_node;

  if (definition)
    {
      new_node = node->create_version_clone_with_body (vNULL, NULL,
    						       NULL, false,
						       NULL, NULL,
						       name);
      new_node->force_output = true;
    }
  else
    {
      tree new_decl = copy_node (node->decl);
      new_node = cgraph_node::get_create (new_decl);
      /* Generate a new name for the new version.  */
      symtab->change_decl_assembler_name (new_node->decl,
					  clone_function_name_numbered (
					      node->decl, name));
    }
  return new_node;
}

/* If the function in NODE has multiple target attributes
   create the appropriate clone for each valid target attribute.  */

static bool
expand_target_clones (struct cgraph_node *node, bool definition)
{
  int i;
  /* Parsing target attributes separated by comma.  */
  tree attr_target = lookup_attribute ("target_clones",
				       DECL_ATTRIBUTES (node->decl));
  /* No targets specified.  */
  if (!attr_target)
    return false;

  tree arglist = TREE_VALUE (attr_target);
  int attr_len = get_attr_len (arglist);

  /* No need to clone for 1 target attribute.  */
  if (attr_len == -1)
    {
      warning_at (DECL_SOURCE_LOCATION (node->decl),
		  0,
		  "single %<target_clones%> attribute is ignored");
      return false;
    }

  if (node->definition
      && !tree_versionable_function_p (node->decl))
    {
      auto_diagnostic_group d;
      error_at (DECL_SOURCE_LOCATION (node->decl),
		"clones for %<target_clones%> attribute cannot be created");
      const char *reason = NULL;
      if (lookup_attribute ("noclone", DECL_ATTRIBUTES (node->decl)))
	reason = G_("function %q+F can never be copied "
		    "because it has %<noclone%> attribute");
      else
	reason = copy_forbidden (DECL_STRUCT_FUNCTION (node->decl));
      if (reason)
	inform (DECL_SOURCE_LOCATION (node->decl), reason, node->decl);
      return false;
    }

  char *attr_str = XNEWVEC (char, attr_len);
  int attrnum = get_attr_str (arglist, attr_str);
  char **attrs = XNEWVEC (char *, attrnum);

  attrnum = separate_attrs (attr_str, attrs, attrnum);
  if (attrnum == -1)
    {
      error_at (DECL_SOURCE_LOCATION (node->decl),
		"default target was not set");
      XDELETEVEC (attrs);
      XDELETEVEC (attr_str);
      return false;
    }
  else if (attrnum == -2)
    {
      error_at (DECL_SOURCE_LOCATION (node->decl),
		"an empty string cannot be in %<target_clones%> attribute");
      XDELETEVEC (attrs);
      XDELETEVEC (attr_str);
      return false;
    }

  cgraph_function_version_info *decl1_v = NULL;
  cgraph_function_version_info *decl2_v = NULL;
  cgraph_function_version_info *before = NULL;
  cgraph_function_version_info *after = NULL;
  decl1_v = node->function_version ();
  if (decl1_v == NULL)
    decl1_v = node->insert_new_function_version ();
  before = decl1_v;
  DECL_FUNCTION_VERSIONED (node->decl) = 1;

  for (i = 0; i < attrnum; i++)
    {
      char *attr = attrs[i];
      char *suffix = XNEWVEC (char, strlen (attr) + 1);

      create_new_asm_name (attr, suffix);
      /* Create new target clone.  */
      cgraph_node *new_node = create_target_clone (node, definition, suffix);
      new_node->local.local = false;
      XDELETEVEC (suffix);

      /* Set new attribute for the clone.  */
      tree attributes = make_attribute ("target", attr,
					DECL_ATTRIBUTES (new_node->decl));
      DECL_ATTRIBUTES (new_node->decl) = attributes;
      location_t saved_loc = input_location;
      input_location = DECL_SOURCE_LOCATION (node->decl);
      if (!targetm.target_option.valid_attribute_p (new_node->decl, NULL,
						    TREE_VALUE (attributes),
						    0))
	return false;

      input_location = saved_loc;
      decl2_v = new_node->function_version ();
      if (decl2_v != NULL)
        continue;
      decl2_v = new_node->insert_new_function_version ();

      /* Chain decl2_v and decl1_v.  All semantically identical versions
	 will be chained together.  */
      after = decl2_v;
      while (before->next != NULL)
	before = before->next;
      while (after->prev != NULL)
	after = after->prev;

      before->next = after;
      after->prev = before;
      DECL_FUNCTION_VERSIONED (new_node->decl) = 1;
    }

  XDELETEVEC (attrs);
  XDELETEVEC (attr_str);

  /* Setting new attribute to initial function.  */
  tree attributes = make_attribute ("target", "default",
				    DECL_ATTRIBUTES (node->decl));
  DECL_ATTRIBUTES (node->decl) = attributes;
  node->local.local = false;
  location_t saved_loc = input_location;
  input_location = DECL_SOURCE_LOCATION (node->decl);
  bool ret
    = targetm.target_option.valid_attribute_p (node->decl, NULL,
					       TREE_VALUE (attributes), 0);
  input_location = saved_loc;
  return ret;
}

/* When NODE is a target clone, consider all callees and redirect
   to a clone with equal target attributes.  That prevents multiple
   multi-versioning dispatches and a call-chain can be optimized.  */

static void
redirect_to_specific_clone (cgraph_node *node)
{
  cgraph_function_version_info *fv = node->function_version ();
  if (fv == NULL)
    return;

  tree attr_target = lookup_attribute ("target", DECL_ATTRIBUTES (node->decl));
  if (attr_target == NULL_TREE)
    return;

  /* We need to remember NEXT_CALLER as it could be modified in the loop.  */
  for (cgraph_edge *e = node->callees; e ; e = e->next_callee)
    {
      cgraph_function_version_info *fv2 = e->callee->function_version ();
      if (!fv2)
	continue;

      tree attr_target2 = lookup_attribute ("target",
					    DECL_ATTRIBUTES (e->callee->decl));

      /* Function is not calling proper target clone.  */
      if (!attribute_list_equal (attr_target, attr_target2))
	{
	  while (fv2->prev != NULL)
	    fv2 = fv2->prev;

	  /* Try to find a clone with equal target attribute.  */
	  for (; fv2 != NULL; fv2 = fv2->next)
	    {
	      cgraph_node *callee = fv2->this_node;
	      attr_target2 = lookup_attribute ("target",
					       DECL_ATTRIBUTES (callee->decl));
	      if (attribute_list_equal (attr_target, attr_target2))
		{
		  e->redirect_callee (callee);
		  e->redirect_call_stmt_to_callee ();
		  break;
		}
	    }
	}
    }
}

static unsigned int
ipa_target_clone (void)
{
  struct cgraph_node *node;
  auto_vec<cgraph_node *> to_dispatch;

  FOR_EACH_FUNCTION (node)
    if (expand_target_clones (node, node->definition))
      to_dispatch.safe_push (node);

  for (unsigned i = 0; i < to_dispatch.length (); i++)
    create_dispatcher_calls (to_dispatch[i]);

  FOR_EACH_FUNCTION (node)
    redirect_to_specific_clone (node);

  return 0;
}

namespace {

const pass_data pass_data_target_clone =
{
  SIMPLE_IPA_PASS,		/* type */
  "targetclone",		/* name */
  OPTGROUP_NONE,		/* optinfo_flags */
  TV_NONE,			/* tv_id */
  ( PROP_ssa | PROP_cfg ),	/* properties_required */
  0,				/* properties_provided */
  0,				/* properties_destroyed */
  0,				/* todo_flags_start */
  TODO_update_ssa		/* todo_flags_finish */
};

class pass_target_clone : public simple_ipa_opt_pass
{
public:
  pass_target_clone (gcc::context *ctxt)
    : simple_ipa_opt_pass (pass_data_target_clone, ctxt)
  {}

  /* opt_pass methods: */
  virtual bool gate (function *);
  virtual unsigned int execute (function *) { return ipa_target_clone (); }
};

bool
pass_target_clone::gate (function *)
{
  return true;
}

} // anon namespace

simple_ipa_opt_pass *
make_pass_target_clone (gcc::context *ctxt)
{
  return new pass_target_clone (ctxt);
}