[39/77] Two changes to the get_best_mode interface

[official-gcc.git] / gcc / attribs.c

/* Functions dealing with attribute handling, used by most front ends.
   Copyright (C) 1992-2017 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 "target.h"
#include "tree.h"
#include "stringpool.h"
#include "diagnostic-core.h"
#include "attribs.h"
#include "stor-layout.h"
#include "langhooks.h"
#include "plugin.h"

/* Table of the tables of attributes (common, language, format, machine)
   searched.  */
static const struct attribute_spec *attribute_tables[4];

/* Substring representation.  */

struct substring
{
  const char *str;
  int length;
};

/* Simple hash function to avoid need to scan whole string.  */

static inline hashval_t
substring_hash (const char *str, int l)
{
  return str[0] + str[l - 1] * 256 + l * 65536;
}

/* Used for attribute_hash.  */

struct attribute_hasher : nofree_ptr_hash <attribute_spec>
{
  typedef substring *compare_type;
  static inline hashval_t hash (const attribute_spec *);
  static inline bool equal (const attribute_spec *, const substring *);
};

inline hashval_t
attribute_hasher::hash (const attribute_spec *spec)
{
  const int l = strlen (spec->name);
  return substring_hash (spec->name, l);
}

inline bool
attribute_hasher::equal (const attribute_spec *spec, const substring *str)
{
  return (strncmp (spec->name, str->str, str->length) == 0
          && !spec->name[str->length]);
}

/* Scoped attribute name representation.  */

struct scoped_attributes
{
  const char *ns;
  vec<attribute_spec> attributes;
  hash_table<attribute_hasher> *attribute_hash;
};

/* The table of scope attributes.  */
static vec<scoped_attributes> attributes_table;

static scoped_attributes* find_attribute_namespace (const char*);
static void register_scoped_attribute (const struct attribute_spec *,
                                       scoped_attributes *);

static bool attributes_initialized = false;

/* Default empty table of attributes.  */

static const struct attribute_spec empty_attribute_table[] =
{
  { NULL, 0, 0, false, false, false, NULL, false }
};

/* Return base name of the attribute.  Ie '__attr__' is turned into 'attr'.
   To avoid need for copying, we simply return length of the string.  */

static void
extract_attribute_substring (struct substring *str)
{
  if (str->length > 4 && str->str[0] == '_' && str->str[1] == '_'
      && str->str[str->length - 1] == '_' && str->str[str->length - 2] == '_')
    {
      str->length -= 4;
      str->str += 2;
    }
}

/* Insert an array of attributes ATTRIBUTES into a namespace.  This
   array must be NULL terminated.  NS is the name of attribute
   namespace.  The function returns the namespace into which the
   attributes have been registered.  */

scoped_attributes*
register_scoped_attributes (const struct attribute_spec * attributes,
                            const char* ns)
{
  scoped_attributes *result = NULL;

  /* See if we already have attributes in the namespace NS.  */
  result = find_attribute_namespace (ns);

  if (result == NULL)
    {
      /* We don't have any namespace NS yet.  Create one.  */
      scoped_attributes sa;

      if (attributes_table.is_empty ())
        attributes_table.create (64);

      memset (&sa, 0, sizeof (sa));
      sa.ns = ns;
      sa.attributes.create (64);
      result = attributes_table.safe_push (sa);
      result->attribute_hash = new hash_table<attribute_hasher> (200);
    }

  /* Really add the attributes to their namespace now.  */
  for (unsigned i = 0; attributes[i].name != NULL; ++i)
    {
      result->attributes.safe_push (attributes[i]);
      register_scoped_attribute (&attributes[i], result);
    }

  gcc_assert (result != NULL);

  return result;
}

/* Return the namespace which name is NS, NULL if none exist.  */

static scoped_attributes*
find_attribute_namespace (const char* ns)
{
  unsigned ix;
  scoped_attributes *iter;

  FOR_EACH_VEC_ELT (attributes_table, ix, iter)
    if (ns == iter->ns
        || (iter->ns != NULL
            && ns != NULL
            && !strcmp (iter->ns, ns)))
      return iter;
  return NULL;
}

/* Make some sanity checks on the attribute tables.  */

static void
check_attribute_tables (void)
{
  for (size_t i = 0; i < ARRAY_SIZE (attribute_tables); i++)
    for (size_t j = 0; attribute_tables[i][j].name != NULL; j++)
      {
        /* The name must not begin and end with __.  */
        const char *name = attribute_tables[i][j].name;
        int len = strlen (name);

        gcc_assert (!(name[0] == '_' && name[1] == '_'
                      && name[len - 1] == '_' && name[len - 2] == '_'));

        /* The minimum and maximum lengths must be consistent.  */
        gcc_assert (attribute_tables[i][j].min_length >= 0);

        gcc_assert (attribute_tables[i][j].max_length == -1
                    || (attribute_tables[i][j].max_length
                        >= attribute_tables[i][j].min_length));

        /* An attribute cannot require both a DECL and a TYPE.  */
        gcc_assert (!attribute_tables[i][j].decl_required
                    || !attribute_tables[i][j].type_required);

          /* If an attribute requires a function type, in particular
             it requires a type.  */
        gcc_assert (!attribute_tables[i][j].function_type_required
                    || attribute_tables[i][j].type_required);
      }

  /* Check that each name occurs just once in each table.  */
  for (size_t i = 0; i < ARRAY_SIZE (attribute_tables); i++)
    for (size_t j = 0; attribute_tables[i][j].name != NULL; j++)
      for (size_t k = j + 1; attribute_tables[i][k].name != NULL; k++)
        gcc_assert (strcmp (attribute_tables[i][j].name,
                            attribute_tables[i][k].name));

  /* Check that no name occurs in more than one table.  Names that
     begin with '*' are exempt, and may be overridden.  */
  for (size_t i = 0; i < ARRAY_SIZE (attribute_tables); i++)
    for (size_t j = i + 1; j < ARRAY_SIZE (attribute_tables); j++)
      for (size_t k = 0; attribute_tables[i][k].name != NULL; k++)
        for (size_t l = 0; attribute_tables[j][l].name != NULL; l++)
          gcc_assert (attribute_tables[i][k].name[0] == '*'
                      || strcmp (attribute_tables[i][k].name,
                                 attribute_tables[j][l].name));
}

/* Initialize attribute tables, and make some sanity checks if checking is
   enabled.  */

void
init_attributes (void)
{
  size_t i;

  if (attributes_initialized)
    return;

  attribute_tables[0] = lang_hooks.common_attribute_table;
  attribute_tables[1] = lang_hooks.attribute_table;
  attribute_tables[2] = lang_hooks.format_attribute_table;
  attribute_tables[3] = targetm.attribute_table;

  /* Translate NULL pointers to pointers to the empty table.  */
  for (i = 0; i < ARRAY_SIZE (attribute_tables); i++)
    if (attribute_tables[i] == NULL)
      attribute_tables[i] = empty_attribute_table;

  if (flag_checking)
    check_attribute_tables ();

  for (i = 0; i < ARRAY_SIZE (attribute_tables); ++i)
    /* Put all the GNU attributes into the "gnu" namespace.  */
    register_scoped_attributes (attribute_tables[i], "gnu");

  invoke_plugin_callbacks (PLUGIN_ATTRIBUTES, NULL);
  attributes_initialized = true;
}

/* Insert a single ATTR into the attribute table.  */

void
register_attribute (const struct attribute_spec *attr)
{
  register_scoped_attribute (attr, find_attribute_namespace ("gnu"));
}

/* Insert a single attribute ATTR into a namespace of attributes.  */

static void
register_scoped_attribute (const struct attribute_spec *attr,
                           scoped_attributes *name_space)
{
  struct substring str;
  attribute_spec **slot;

  gcc_assert (attr != NULL && name_space != NULL);

  gcc_assert (name_space->attribute_hash);

  str.str = attr->name;
  str.length = strlen (str.str);

  /* Attribute names in the table must be in the form 'text' and not
     in the form '__text__'.  */
  gcc_assert (str.length > 0 && str.str[0] != '_');

  slot = name_space->attribute_hash
         ->find_slot_with_hash (&str, substring_hash (str.str, str.length),
                                INSERT);
  gcc_assert (!*slot || attr->name[0] == '*');
  *slot = CONST_CAST (struct attribute_spec *, attr);
}

/* Return the spec for the scoped attribute with namespace NS and
   name NAME.   */

static const struct attribute_spec *
lookup_scoped_attribute_spec (const_tree ns, const_tree name)
{
  struct substring attr;
  scoped_attributes *attrs;

  const char *ns_str = (ns != NULL_TREE) ? IDENTIFIER_POINTER (ns): NULL;

  attrs = find_attribute_namespace (ns_str);

  if (attrs == NULL)
    return NULL;

  attr.str = IDENTIFIER_POINTER (name);
  attr.length = IDENTIFIER_LENGTH (name);
  extract_attribute_substring (&attr);
  return attrs->attribute_hash->find_with_hash (&attr,
                                                substring_hash (attr.str,
                                                                attr.length));
}

/* Return the spec for the attribute named NAME.  If NAME is a TREE_LIST,
   it also specifies the attribute namespace.  */

const struct attribute_spec *
lookup_attribute_spec (const_tree name)
{
  tree ns;
  if (TREE_CODE (name) == TREE_LIST)
    {
      ns = TREE_PURPOSE (name);
      name = TREE_VALUE (name);
    }
  else
    ns = get_identifier ("gnu");
  return lookup_scoped_attribute_spec (ns, name);
}


/* Return the namespace of the attribute ATTR.  This accessor works on
   GNU and C++11 (scoped) attributes.  On GNU attributes,
   it returns an identifier tree for the string "gnu".

   Please read the comments of cxx11_attribute_p to understand the
   format of attributes.  */

static tree
get_attribute_namespace (const_tree attr)
{
  if (cxx11_attribute_p (attr))
    return TREE_PURPOSE (TREE_PURPOSE (attr));
  return get_identifier ("gnu");
}


/* Process the attributes listed in ATTRIBUTES and install them in *NODE,
   which is either a DECL (including a TYPE_DECL) or a TYPE.  If a DECL,
   it should be modified in place; if a TYPE, a copy should be created
   unless ATTR_FLAG_TYPE_IN_PLACE is set in FLAGS.  FLAGS gives further
   information, in the form of a bitwise OR of flags in enum attribute_flags
   from tree.h.  Depending on these flags, some attributes may be
   returned to be applied at a later stage (for example, to apply
   a decl attribute to the declaration rather than to its type).  */

tree
decl_attributes (tree *node, tree attributes, int flags)
{
  tree a;
  tree returned_attrs = NULL_TREE;

  if (TREE_TYPE (*node) == error_mark_node || attributes == error_mark_node)
    return NULL_TREE;

  if (!attributes_initialized)
    init_attributes ();

  /* If this is a function and the user used #pragma GCC optimize, add the
     options to the attribute((optimize(...))) list.  */
  if (TREE_CODE (*node) == FUNCTION_DECL && current_optimize_pragma)
    {
      tree cur_attr = lookup_attribute ("optimize", attributes);
      tree opts = copy_list (current_optimize_pragma);

      if (! cur_attr)
        attributes
          = tree_cons (get_identifier ("optimize"), opts, attributes);
      else
        TREE_VALUE (cur_attr) = chainon (opts, TREE_VALUE (cur_attr));
    }

  if (TREE_CODE (*node) == FUNCTION_DECL
      && optimization_current_node != optimization_default_node
      && !DECL_FUNCTION_SPECIFIC_OPTIMIZATION (*node))
    DECL_FUNCTION_SPECIFIC_OPTIMIZATION (*node) = optimization_current_node;

  /* If this is a function and the user used #pragma GCC target, add the
     options to the attribute((target(...))) list.  */
  if (TREE_CODE (*node) == FUNCTION_DECL
      && current_target_pragma
      && targetm.target_option.valid_attribute_p (*node, NULL_TREE,
                                                  current_target_pragma, 0))
    {
      tree cur_attr = lookup_attribute ("target", attributes);
      tree opts = copy_list (current_target_pragma);

      if (! cur_attr)
        attributes = tree_cons (get_identifier ("target"), opts, attributes);
      else
        TREE_VALUE (cur_attr) = chainon (opts, TREE_VALUE (cur_attr));
    }

  /* A "naked" function attribute implies "noinline" and "noclone" for
     those targets that support it.  */
  if (TREE_CODE (*node) == FUNCTION_DECL
      && attributes
      && lookup_attribute ("naked", attributes) != NULL
      && lookup_attribute_spec (get_identifier ("naked")))
    {
      if (lookup_attribute ("noinline", attributes) == NULL)
        attributes = tree_cons (get_identifier ("noinline"), NULL, attributes);

      if (lookup_attribute ("noclone", attributes) == NULL)
        attributes = tree_cons (get_identifier ("noclone"),  NULL, attributes);
    }

  /* A "noipa" function attribute implies "noinline", "noclone" and "no_icf"
     for those targets that support it.  */
  if (TREE_CODE (*node) == FUNCTION_DECL
      && attributes
      && lookup_attribute ("noipa", attributes) != NULL
      && lookup_attribute_spec (get_identifier ("noipa")))
    {
      if (lookup_attribute ("noinline", attributes) == NULL)
        attributes = tree_cons (get_identifier ("noinline"), NULL, attributes);

      if (lookup_attribute ("noclone", attributes) == NULL)
        attributes = tree_cons (get_identifier ("noclone"),  NULL, attributes);

      if (lookup_attribute ("no_icf", attributes) == NULL)
        attributes = tree_cons (get_identifier ("no_icf"),  NULL, attributes);
    }

  targetm.insert_attributes (*node, &attributes);

  for (a = attributes; a; a = TREE_CHAIN (a))
    {
      tree ns = get_attribute_namespace (a);
      tree name = get_attribute_name (a);
      tree args = TREE_VALUE (a);
      tree *anode = node;
      const struct attribute_spec *spec =
        lookup_scoped_attribute_spec (ns, name);
      bool no_add_attrs = 0;
      int fn_ptr_quals = 0;
      tree fn_ptr_tmp = NULL_TREE;

      if (spec == NULL)
        {
          if (!(flags & (int) ATTR_FLAG_BUILT_IN))
            {
              if (ns == NULL_TREE || !cxx11_attribute_p (a))
                warning (OPT_Wattributes, "%qE attribute directive ignored",
                         name);
              else
                warning (OPT_Wattributes,
                         "%<%E::%E%> scoped attribute directive ignored",
                         ns, name);
            }
          continue;
        }
      else if (list_length (args) < spec->min_length
               || (spec->max_length >= 0
                   && list_length (args) > spec->max_length))
        {
          error ("wrong number of arguments specified for %qE attribute",
                 name);
          continue;
        }
      gcc_assert (is_attribute_p (spec->name, name));

      if (TYPE_P (*node)
          && cxx11_attribute_p (a)
          && !(flags & ATTR_FLAG_TYPE_IN_PLACE))
        {
          /* This is a c++11 attribute that appertains to a
             type-specifier, outside of the definition of, a class
             type.  Ignore it.  */
          if (warning (OPT_Wattributes, "attribute ignored"))
            inform (input_location,
                    "an attribute that appertains to a type-specifier "
                    "is ignored");
          continue;
        }

      if (spec->decl_required && !DECL_P (*anode))
        {
          if (flags & ((int) ATTR_FLAG_DECL_NEXT
                       | (int) ATTR_FLAG_FUNCTION_NEXT
                       | (int) ATTR_FLAG_ARRAY_NEXT))
            {
              /* Pass on this attribute to be tried again.  */
              returned_attrs = tree_cons (name, args, returned_attrs);
              continue;
            }
          else
            {
              warning (OPT_Wattributes, "%qE attribute does not apply to types",
                       name);
              continue;
            }
        }

      /* If we require a type, but were passed a decl, set up to make a
         new type and update the one in the decl.  ATTR_FLAG_TYPE_IN_PLACE
         would have applied if we'd been passed a type, but we cannot modify
         the decl's type in place here.  */
      if (spec->type_required && DECL_P (*anode))
        {
          anode = &TREE_TYPE (*anode);
          flags &= ~(int) ATTR_FLAG_TYPE_IN_PLACE;
        }

      if (spec->function_type_required && TREE_CODE (*anode) != FUNCTION_TYPE
          && TREE_CODE (*anode) != METHOD_TYPE)
        {
          if (TREE_CODE (*anode) == POINTER_TYPE
              && (TREE_CODE (TREE_TYPE (*anode)) == FUNCTION_TYPE
                  || TREE_CODE (TREE_TYPE (*anode)) == METHOD_TYPE))
            {
              /* OK, this is a bit convoluted.  We can't just make a copy
                 of the pointer type and modify its TREE_TYPE, because if
                 we change the attributes of the target type the pointer
                 type needs to have a different TYPE_MAIN_VARIANT.  So we
                 pull out the target type now, frob it as appropriate, and
                 rebuild the pointer type later.

                 This would all be simpler if attributes were part of the
                 declarator, grumble grumble.  */
              fn_ptr_tmp = TREE_TYPE (*anode);
              fn_ptr_quals = TYPE_QUALS (*anode);
              anode = &fn_ptr_tmp;
              flags &= ~(int) ATTR_FLAG_TYPE_IN_PLACE;
            }
          else if (flags & (int) ATTR_FLAG_FUNCTION_NEXT)
            {
              /* Pass on this attribute to be tried again.  */
              returned_attrs = tree_cons (name, args, returned_attrs);
              continue;
            }

          if (TREE_CODE (*anode) != FUNCTION_TYPE
              && TREE_CODE (*anode) != METHOD_TYPE)
            {
              warning (OPT_Wattributes,
                       "%qE attribute only applies to function types",
                       name);
              continue;
            }
        }

      if (TYPE_P (*anode)
          && (flags & (int) ATTR_FLAG_TYPE_IN_PLACE)
          && TYPE_SIZE (*anode) != NULL_TREE)
        {
          warning (OPT_Wattributes, "type attributes ignored after type is already defined");
          continue;
        }

      if (spec->handler != NULL)
        {
          int cxx11_flag =
            cxx11_attribute_p (a) ? ATTR_FLAG_CXX11 : 0;

          returned_attrs = chainon ((*spec->handler) (anode, name, args,
                                                      flags|cxx11_flag,
                                                      &no_add_attrs),
                                    returned_attrs);
        }

      /* Layout the decl in case anything changed.  */
      if (spec->type_required && DECL_P (*node)
          && (VAR_P (*node)
              || TREE_CODE (*node) == PARM_DECL
              || TREE_CODE (*node) == RESULT_DECL))
        relayout_decl (*node);

      if (!no_add_attrs)
        {
          tree old_attrs;
          tree a;

          if (DECL_P (*anode))
            old_attrs = DECL_ATTRIBUTES (*anode);
          else
            old_attrs = TYPE_ATTRIBUTES (*anode);

          for (a = lookup_attribute (spec->name, old_attrs);
               a != NULL_TREE;
               a = lookup_attribute (spec->name, TREE_CHAIN (a)))
            {
              if (simple_cst_equal (TREE_VALUE (a), args) == 1)
                break;
            }

          if (a == NULL_TREE)
            {
              /* This attribute isn't already in the list.  */
              if (DECL_P (*anode))
                DECL_ATTRIBUTES (*anode) = tree_cons (name, args, old_attrs);
              else if (flags & (int) ATTR_FLAG_TYPE_IN_PLACE)
                {
                  TYPE_ATTRIBUTES (*anode) = tree_cons (name, args, old_attrs);
                  /* If this is the main variant, also push the attributes
                     out to the other variants.  */
                  if (*anode == TYPE_MAIN_VARIANT (*anode))
                    {
                      tree variant;
                      for (variant = *anode; variant;
                           variant = TYPE_NEXT_VARIANT (variant))
                        {
                          if (TYPE_ATTRIBUTES (variant) == old_attrs)
                            TYPE_ATTRIBUTES (variant)
                              = TYPE_ATTRIBUTES (*anode);
                          else if (!lookup_attribute
                                   (spec->name, TYPE_ATTRIBUTES (variant)))
                            TYPE_ATTRIBUTES (variant) = tree_cons
                              (name, args, TYPE_ATTRIBUTES (variant));
                        }
                    }
                }
              else
                *anode = build_type_attribute_variant (*anode,
                                                       tree_cons (name, args,
                                                                  old_attrs));
            }
        }

      if (fn_ptr_tmp)
        {
          /* Rebuild the function pointer type and put it in the
             appropriate place.  */
          fn_ptr_tmp = build_pointer_type (fn_ptr_tmp);
          if (fn_ptr_quals)
            fn_ptr_tmp = build_qualified_type (fn_ptr_tmp, fn_ptr_quals);
          if (DECL_P (*node))
            TREE_TYPE (*node) = fn_ptr_tmp;
          else
            {
              gcc_assert (TREE_CODE (*node) == POINTER_TYPE);
              *node = fn_ptr_tmp;
            }
        }
    }

  return returned_attrs;
}

/* Return TRUE iff ATTR has been parsed by the front-end as a C++-11
   attribute.

   When G++ parses a C++11 attribute, it is represented as
   a TREE_LIST which TREE_PURPOSE is itself a TREE_LIST.  TREE_PURPOSE
   (TREE_PURPOSE (ATTR)) is the namespace of the attribute, and the
   TREE_VALUE (TREE_PURPOSE (ATTR)) is its non-qualified name.  Please
   use get_attribute_namespace and get_attribute_name to retrieve the
   namespace and name of the attribute, as these accessors work with
   GNU attributes as well.  */

bool
cxx11_attribute_p (const_tree attr)
{
  if (attr == NULL_TREE
      || TREE_CODE (attr) != TREE_LIST)
    return false;

  return (TREE_CODE (TREE_PURPOSE (attr)) == TREE_LIST);
}

/* Return the name of the attribute ATTR.  This accessor works on GNU
   and C++11 (scoped) attributes.

   Please read the comments of cxx11_attribute_p to understand the
   format of attributes.  */

tree
get_attribute_name (const_tree attr)
{
  if (cxx11_attribute_p (attr))
    return TREE_VALUE (TREE_PURPOSE (attr));
  return TREE_PURPOSE (attr);
}

/* Subroutine of set_method_tm_attributes.  Apply TM attribute ATTR
   to the method FNDECL.  */

void
apply_tm_attr (tree fndecl, tree attr)
{
  decl_attributes (&TREE_TYPE (fndecl), tree_cons (attr, NULL, NULL), 0);
}

/* Makes a function attribute of the form NAME(ARG_NAME) and chains
   it to CHAIN.  */

tree
make_attribute (const char *name, const char *arg_name, tree chain)
{
  tree attr_name;
  tree attr_arg_name;
  tree attr_args;
  tree attr;

  attr_name = get_identifier (name);
  attr_arg_name = build_string (strlen (arg_name), arg_name);
  attr_args = tree_cons (NULL_TREE, attr_arg_name, NULL_TREE);
  attr = tree_cons (attr_name, attr_args, chain);
  return attr;
}

\f
/* Common functions used for target clone support.  */

/* Comparator function to be used in qsort routine to sort attribute
   specification strings to "target".  */

static int
attr_strcmp (const void *v1, const void *v2)
{
  const char *c1 = *(char *const*)v1;
  const char *c2 = *(char *const*)v2;
  return strcmp (c1, c2);
}

/* ARGLIST is the argument to target attribute.  This function tokenizes
   the comma separated arguments, sorts them and returns a string which
   is a unique identifier for the comma separated arguments.   It also
   replaces non-identifier characters "=,-" with "_".  */

char *
sorted_attr_string (tree arglist)
{
  tree arg;
  size_t str_len_sum = 0;
  char **args = NULL;
  char *attr_str, *ret_str;
  char *attr = NULL;
  unsigned int argnum = 1;
  unsigned int i;

  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;
      if (arg != arglist)
        argnum++;
      for (i = 0; i < strlen (str); i++)
        if (str[i] == ',')
          argnum++;
    }

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

  /* Replace "=,-" with "_".  */
  for (i = 0; i < strlen (attr_str); i++)
    if (attr_str[i] == '=' || attr_str[i]== '-')
      attr_str[i] = '_';

  if (argnum == 1)
    return attr_str;

  args = XNEWVEC (char *, argnum);

  i = 0;
  attr = strtok (attr_str, ",");
  while (attr != NULL)
    {
      args[i] = attr;
      i++;
      attr = strtok (NULL, ",");
    }

  qsort (args, argnum, sizeof (char *), attr_strcmp);

  ret_str = XNEWVEC (char, str_len_sum);
  str_len_sum = 0;
  for (i = 0; i < argnum; i++)
    {
      size_t len = strlen (args[i]);
      memcpy (ret_str + str_len_sum, args[i], len);
      ret_str[str_len_sum + len] = i < argnum - 1 ? '_' : '\0';
      str_len_sum += len + 1;
    }

  XDELETEVEC (args);
  XDELETEVEC (attr_str);
  return ret_str;
}


/* This function returns true if FN1 and FN2 are versions of the same function,
   that is, the target strings of the function decls are different.  This assumes
   that FN1 and FN2 have the same signature.  */

bool
common_function_versions (tree fn1, tree fn2)
{
  tree attr1, attr2;
  char *target1, *target2;
  bool result;

  if (TREE_CODE (fn1) != FUNCTION_DECL
      || TREE_CODE (fn2) != FUNCTION_DECL)
    return false;

  attr1 = lookup_attribute ("target", DECL_ATTRIBUTES (fn1));
  attr2 = lookup_attribute ("target", DECL_ATTRIBUTES (fn2));

  /* At least one function decl should have the target attribute specified.  */
  if (attr1 == NULL_TREE && attr2 == NULL_TREE)
    return false;

  /* Diagnose missing target attribute if one of the decls is already
     multi-versioned.  */
  if (attr1 == NULL_TREE || attr2 == NULL_TREE)
    {
      if (DECL_FUNCTION_VERSIONED (fn1) || DECL_FUNCTION_VERSIONED (fn2))
        {
          if (attr2 != NULL_TREE)
            {
              std::swap (fn1, fn2);
              attr1 = attr2;
            }
          error_at (DECL_SOURCE_LOCATION (fn2),
                    "missing %<target%> attribute for multi-versioned %qD",
                    fn2);
          inform (DECL_SOURCE_LOCATION (fn1),
                  "previous declaration of %qD", fn1);
          /* Prevent diagnosing of the same error multiple times.  */
          DECL_ATTRIBUTES (fn2)
            = tree_cons (get_identifier ("target"),
                         copy_node (TREE_VALUE (attr1)),
                         DECL_ATTRIBUTES (fn2));
        }
      return false;
    }

  target1 = sorted_attr_string (TREE_VALUE (attr1));
  target2 = sorted_attr_string (TREE_VALUE (attr2));

  /* The sorted target strings must be different for fn1 and fn2
     to be versions.  */
  if (strcmp (target1, target2) == 0)
    result = false;
  else
    result = true;

  XDELETEVEC (target1);
  XDELETEVEC (target2);

  return result;
}

/* Return a new name by appending SUFFIX to the DECL name.  If make_unique
   is true, append the full path name of the source file.  */

char *
make_unique_name (tree decl, const char *suffix, bool make_unique)
{
  char *global_var_name;
  int name_len;
  const char *name;
  const char *unique_name = NULL;

  name = IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (decl));

  /* Get a unique name that can be used globally without any chances
     of collision at link time.  */
  if (make_unique)
    unique_name = IDENTIFIER_POINTER (get_file_function_name ("\0"));

  name_len = strlen (name) + strlen (suffix) + 2;

  if (make_unique)
    name_len += strlen (unique_name) + 1;
  global_var_name = XNEWVEC (char, name_len);

  /* Use '.' to concatenate names as it is demangler friendly.  */
  if (make_unique)
    snprintf (global_var_name, name_len, "%s.%s.%s", name, unique_name,
              suffix);
  else
    snprintf (global_var_name, name_len, "%s.%s", name, suffix);

  return global_var_name;
}

/* Make a dispatcher declaration for the multi-versioned function DECL.
   Calls to DECL function will be replaced with calls to the dispatcher
   by the front-end.  Return the decl created.  */

tree
make_dispatcher_decl (const tree decl)
{
  tree func_decl;
  char *func_name;
  tree fn_type, func_type;

  func_name = xstrdup (IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (decl)));

  fn_type = TREE_TYPE (decl);
  func_type = build_function_type (TREE_TYPE (fn_type),
                                   TYPE_ARG_TYPES (fn_type));
  
  func_decl = build_fn_decl (func_name, func_type);
  XDELETEVEC (func_name);
  TREE_USED (func_decl) = 1;
  DECL_CONTEXT (func_decl) = NULL_TREE;
  DECL_INITIAL (func_decl) = error_mark_node;
  DECL_ARTIFICIAL (func_decl) = 1;
  /* Mark this func as external, the resolver will flip it again if
     it gets generated.  */
  DECL_EXTERNAL (func_decl) = 1;
  /* This will be of type IFUNCs have to be externally visible.  */
  TREE_PUBLIC (func_decl) = 1;

  return func_decl;  
}

/* Returns true if decl is multi-versioned and DECL is the default function,
   that is it is not tagged with target specific optimization.  */

bool
is_function_default_version (const tree decl)
{
  if (TREE_CODE (decl) != FUNCTION_DECL
      || !DECL_FUNCTION_VERSIONED (decl))
    return false;
  tree attr = lookup_attribute ("target", DECL_ATTRIBUTES (decl));
  gcc_assert (attr);
  attr = TREE_VALUE (TREE_VALUE (attr));
  return (TREE_CODE (attr) == STRING_CST
          && strcmp (TREE_STRING_POINTER (attr), "default") == 0);
}

/* Return a declaration like DDECL except that its DECL_ATTRIBUTES
   is ATTRIBUTE.  */

tree
build_decl_attribute_variant (tree ddecl, tree attribute)
{
  DECL_ATTRIBUTES (ddecl) = attribute;
  return ddecl;
}

/* Return a type like TTYPE except that its TYPE_ATTRIBUTE
   is ATTRIBUTE and its qualifiers are QUALS.

   Record such modified types already made so we don't make duplicates.  */

tree
build_type_attribute_qual_variant (tree ttype, tree attribute, int quals)
{
  if (! attribute_list_equal (TYPE_ATTRIBUTES (ttype), attribute))
    {
      tree ntype;

      /* Building a distinct copy of a tagged type is inappropriate; it
         causes breakage in code that expects there to be a one-to-one
         relationship between a struct and its fields.
         build_duplicate_type is another solution (as used in
         handle_transparent_union_attribute), but that doesn't play well
         with the stronger C++ type identity model.  */
      if (TREE_CODE (ttype) == RECORD_TYPE
          || TREE_CODE (ttype) == UNION_TYPE
          || TREE_CODE (ttype) == QUAL_UNION_TYPE
          || TREE_CODE (ttype) == ENUMERAL_TYPE)
        {
          warning (OPT_Wattributes,
                   "ignoring attributes applied to %qT after definition",
                   TYPE_MAIN_VARIANT (ttype));
          return build_qualified_type (ttype, quals);
        }

      ttype = build_qualified_type (ttype, TYPE_UNQUALIFIED);
      ntype = build_distinct_type_copy (ttype);

      TYPE_ATTRIBUTES (ntype) = attribute;

      hashval_t hash = type_hash_canon_hash (ntype);
      ntype = type_hash_canon (hash, ntype);

      /* If the target-dependent attributes make NTYPE different from
         its canonical type, we will need to use structural equality
         checks for this type.  */
      if (TYPE_STRUCTURAL_EQUALITY_P (ttype)
          || !comp_type_attributes (ntype, ttype))
        SET_TYPE_STRUCTURAL_EQUALITY (ntype);
      else if (TYPE_CANONICAL (ntype) == ntype)
        TYPE_CANONICAL (ntype) = TYPE_CANONICAL (ttype);

      ttype = build_qualified_type (ntype, quals);
    }
  else if (TYPE_QUALS (ttype) != quals)
    ttype = build_qualified_type (ttype, quals);

  return ttype;
}

/* Compare two identifier nodes representing attributes.
   Return true if they are the same, false otherwise.  */

static bool
cmp_attrib_identifiers (const_tree attr1, const_tree attr2)
{
  /* Make sure we're dealing with IDENTIFIER_NODEs.  */
  gcc_checking_assert (TREE_CODE (attr1) == IDENTIFIER_NODE
                       && TREE_CODE (attr2) == IDENTIFIER_NODE);

  /* Identifiers can be compared directly for equality.  */
  if (attr1 == attr2)
    return true;

  return cmp_attribs (IDENTIFIER_POINTER (attr1), IDENTIFIER_LENGTH (attr1),
                      IDENTIFIER_POINTER (attr2), IDENTIFIER_LENGTH (attr2));
}

/* Compare two constructor-element-type constants.  Return 1 if the lists
   are known to be equal; otherwise return 0.  */

static bool
simple_cst_list_equal (const_tree l1, const_tree l2)
{
  while (l1 != NULL_TREE && l2 != NULL_TREE)
    {
      if (simple_cst_equal (TREE_VALUE (l1), TREE_VALUE (l2)) != 1)
        return false;

      l1 = TREE_CHAIN (l1);
      l2 = TREE_CHAIN (l2);
    }

  return l1 == l2;
}

/* Check if "omp declare simd" attribute arguments, CLAUSES1 and CLAUSES2, are
   the same.  */

static bool
omp_declare_simd_clauses_equal (tree clauses1, tree clauses2)
{
  tree cl1, cl2;
  for (cl1 = clauses1, cl2 = clauses2;
       cl1 && cl2;
       cl1 = OMP_CLAUSE_CHAIN (cl1), cl2 = OMP_CLAUSE_CHAIN (cl2))
    {
      if (OMP_CLAUSE_CODE (cl1) != OMP_CLAUSE_CODE (cl2))
        return false;
      if (OMP_CLAUSE_CODE (cl1) != OMP_CLAUSE_SIMDLEN)
        {
          if (simple_cst_equal (OMP_CLAUSE_DECL (cl1),
                                OMP_CLAUSE_DECL (cl2)) != 1)
            return false;
        }
      switch (OMP_CLAUSE_CODE (cl1))
        {
        case OMP_CLAUSE_ALIGNED:
          if (simple_cst_equal (OMP_CLAUSE_ALIGNED_ALIGNMENT (cl1),
                                OMP_CLAUSE_ALIGNED_ALIGNMENT (cl2)) != 1)
            return false;
          break;
        case OMP_CLAUSE_LINEAR:
          if (simple_cst_equal (OMP_CLAUSE_LINEAR_STEP (cl1),
                                OMP_CLAUSE_LINEAR_STEP (cl2)) != 1)
            return false;
          break;
        case OMP_CLAUSE_SIMDLEN:
          if (simple_cst_equal (OMP_CLAUSE_SIMDLEN_EXPR (cl1),
                                OMP_CLAUSE_SIMDLEN_EXPR (cl2)) != 1)
            return false;
        default:
          break;
        }
    }
  return true;
}


/* Compare two attributes for their value identity.  Return true if the
   attribute values are known to be equal; otherwise return false.  */

bool
attribute_value_equal (const_tree attr1, const_tree attr2)
{
  if (TREE_VALUE (attr1) == TREE_VALUE (attr2))
    return true;

  if (TREE_VALUE (attr1) != NULL_TREE
      && TREE_CODE (TREE_VALUE (attr1)) == TREE_LIST
      && TREE_VALUE (attr2) != NULL_TREE
      && TREE_CODE (TREE_VALUE (attr2)) == TREE_LIST)
    {
      /* Handle attribute format.  */
      if (is_attribute_p ("format", get_attribute_name (attr1)))
        {
          attr1 = TREE_VALUE (attr1);
          attr2 = TREE_VALUE (attr2);
          /* Compare the archetypes (printf/scanf/strftime/...).  */
          if (!cmp_attrib_identifiers (TREE_VALUE (attr1), TREE_VALUE (attr2)))
            return false;
          /* Archetypes are the same.  Compare the rest.  */
          return (simple_cst_list_equal (TREE_CHAIN (attr1),
                                         TREE_CHAIN (attr2)) == 1);
        }
      return (simple_cst_list_equal (TREE_VALUE (attr1),
                                     TREE_VALUE (attr2)) == 1);
    }

  if ((flag_openmp || flag_openmp_simd)
      && TREE_VALUE (attr1) && TREE_VALUE (attr2)
      && TREE_CODE (TREE_VALUE (attr1)) == OMP_CLAUSE
      && TREE_CODE (TREE_VALUE (attr2)) == OMP_CLAUSE)
    return omp_declare_simd_clauses_equal (TREE_VALUE (attr1),
                                           TREE_VALUE (attr2));

  return (simple_cst_equal (TREE_VALUE (attr1), TREE_VALUE (attr2)) == 1);
}

/* Return 0 if the attributes for two types are incompatible, 1 if they
   are compatible, and 2 if they are nearly compatible (which causes a
   warning to be generated).  */
int
comp_type_attributes (const_tree type1, const_tree type2)
{
  const_tree a1 = TYPE_ATTRIBUTES (type1);
  const_tree a2 = TYPE_ATTRIBUTES (type2);
  const_tree a;

  if (a1 == a2)
    return 1;
  for (a = a1; a != NULL_TREE; a = TREE_CHAIN (a))
    {
      const struct attribute_spec *as;
      const_tree attr;

      as = lookup_attribute_spec (get_attribute_name (a));
      if (!as || as->affects_type_identity == false)
        continue;

      attr = lookup_attribute (as->name, CONST_CAST_TREE (a2));
      if (!attr || !attribute_value_equal (a, attr))
        break;
    }
  if (!a)
    {
      for (a = a2; a != NULL_TREE; a = TREE_CHAIN (a))
        {
          const struct attribute_spec *as;

          as = lookup_attribute_spec (get_attribute_name (a));
          if (!as || as->affects_type_identity == false)
            continue;

          if (!lookup_attribute (as->name, CONST_CAST_TREE (a1)))
            break;
          /* We don't need to compare trees again, as we did this
             already in first loop.  */
        }
      /* All types - affecting identity - are equal, so
         there is no need to call target hook for comparison.  */
      if (!a)
        return 1;
    }
  if (lookup_attribute ("transaction_safe", CONST_CAST_TREE (a)))
    return 0;
  /* As some type combinations - like default calling-convention - might
     be compatible, we have to call the target hook to get the final result.  */
  return targetm.comp_type_attributes (type1, type2);
}

/* Return a type like TTYPE except that its TYPE_ATTRIBUTE
   is ATTRIBUTE.

   Record such modified types already made so we don't make duplicates.  */

tree
build_type_attribute_variant (tree ttype, tree attribute)
{
  return build_type_attribute_qual_variant (ttype, attribute,
                                            TYPE_QUALS (ttype));
}
\f
/* A variant of lookup_attribute() that can be used with an identifier
   as the first argument, and where the identifier can be either
   'text' or '__text__'.

   Given an attribute ATTR_IDENTIFIER, and a list of attributes LIST,
   return a pointer to the attribute's list element if the attribute
   is part of the list, or NULL_TREE if not found.  If the attribute
   appears more than once, this only returns the first occurrence; the
   TREE_CHAIN of the return value should be passed back in if further
   occurrences are wanted.  ATTR_IDENTIFIER must be an identifier but
   can be in the form 'text' or '__text__'.  */
static tree
lookup_ident_attribute (tree attr_identifier, tree list)
{
  gcc_checking_assert (TREE_CODE (attr_identifier) == IDENTIFIER_NODE);

  while (list)
    {
      gcc_checking_assert (TREE_CODE (get_attribute_name (list))
                           == IDENTIFIER_NODE);

      if (cmp_attrib_identifiers (attr_identifier,
                                  get_attribute_name (list)))
        /* Found it.  */
        break;
      list = TREE_CHAIN (list);
    }

  return list;
}

/* Remove any instances of attribute ATTR_NAME in LIST and return the
   modified list.  */

tree
remove_attribute (const char *attr_name, tree list)
{
  tree *p;
  gcc_checking_assert (attr_name[0] != '_');

  for (p = &list; *p;)
    {
      tree l = *p;

      tree attr = get_attribute_name (l);
      if (is_attribute_p (attr_name, attr))
        *p = TREE_CHAIN (l);
      else
        p = &TREE_CHAIN (l);
    }

  return list;
}

/* Return an attribute list that is the union of a1 and a2.  */

tree
merge_attributes (tree a1, tree a2)
{
  tree attributes;

  /* Either one unset?  Take the set one.  */

  if ((attributes = a1) == 0)
    attributes = a2;

  /* One that completely contains the other?  Take it.  */

  else if (a2 != 0 && ! attribute_list_contained (a1, a2))
    {
      if (attribute_list_contained (a2, a1))
        attributes = a2;
      else
        {
          /* Pick the longest list, and hang on the other list.  */

          if (list_length (a1) < list_length (a2))
            attributes = a2, a2 = a1;

          for (; a2 != 0; a2 = TREE_CHAIN (a2))
            {
              tree a;
              for (a = lookup_ident_attribute (get_attribute_name (a2),
                                               attributes);
                   a != NULL_TREE && !attribute_value_equal (a, a2);
                   a = lookup_ident_attribute (get_attribute_name (a2),
                                               TREE_CHAIN (a)))
                ;
              if (a == NULL_TREE)
                {
                  a1 = copy_node (a2);
                  TREE_CHAIN (a1) = attributes;
                  attributes = a1;
                }
            }
        }
    }
  return attributes;
}

/* Given types T1 and T2, merge their attributes and return
  the result.  */

tree
merge_type_attributes (tree t1, tree t2)
{
  return merge_attributes (TYPE_ATTRIBUTES (t1),
                           TYPE_ATTRIBUTES (t2));
}

/* Given decls OLDDECL and NEWDECL, merge their attributes and return
   the result.  */

tree
merge_decl_attributes (tree olddecl, tree newdecl)
{
  return merge_attributes (DECL_ATTRIBUTES (olddecl),
                           DECL_ATTRIBUTES (newdecl));
}

#if TARGET_DLLIMPORT_DECL_ATTRIBUTES

/* Specialization of merge_decl_attributes for various Windows targets.

   This handles the following situation:

     __declspec (dllimport) int foo;
     int foo;

   The second instance of `foo' nullifies the dllimport.  */

tree
merge_dllimport_decl_attributes (tree old, tree new_tree)
{
  tree a;
  int delete_dllimport_p = 1;

  /* What we need to do here is remove from `old' dllimport if it doesn't
     appear in `new'.  dllimport behaves like extern: if a declaration is
     marked dllimport and a definition appears later, then the object
     is not dllimport'd.  We also remove a `new' dllimport if the old list
     contains dllexport:  dllexport always overrides dllimport, regardless
     of the order of declaration.  */
  if (!VAR_OR_FUNCTION_DECL_P (new_tree))
    delete_dllimport_p = 0;
  else if (DECL_DLLIMPORT_P (new_tree)
           && lookup_attribute ("dllexport", DECL_ATTRIBUTES (old)))
    {
      DECL_DLLIMPORT_P (new_tree) = 0;
      warning (OPT_Wattributes, "%q+D already declared with dllexport "
               "attribute: dllimport ignored", new_tree);
    }
  else if (DECL_DLLIMPORT_P (old) && !DECL_DLLIMPORT_P (new_tree))
    {
      /* Warn about overriding a symbol that has already been used, e.g.:
           extern int __attribute__ ((dllimport)) foo;
           int* bar () {return &foo;}
           int foo;
      */
      if (TREE_USED (old))
        {
          warning (0, "%q+D redeclared without dllimport attribute "
                   "after being referenced with dll linkage", new_tree);
          /* If we have used a variable's address with dllimport linkage,
              keep the old DECL_DLLIMPORT_P flag: the ADDR_EXPR using the
              decl may already have had TREE_CONSTANT computed.
              We still remove the attribute so that assembler code refers
              to '&foo rather than '_imp__foo'.  */
          if (VAR_P (old) && TREE_ADDRESSABLE (old))
            DECL_DLLIMPORT_P (new_tree) = 1;
        }

      /* Let an inline definition silently override the external reference,
         but otherwise warn about attribute inconsistency.  */
      else if (VAR_P (new_tree) || !DECL_DECLARED_INLINE_P (new_tree))
        warning (OPT_Wattributes, "%q+D redeclared without dllimport "
                 "attribute: previous dllimport ignored", new_tree);
    }
  else
    delete_dllimport_p = 0;

  a = merge_attributes (DECL_ATTRIBUTES (old), DECL_ATTRIBUTES (new_tree));

  if (delete_dllimport_p)
    a = remove_attribute ("dllimport", a);

  return a;
}

/* Handle a "dllimport" or "dllexport" attribute; arguments as in
   struct attribute_spec.handler.  */

tree
handle_dll_attribute (tree * pnode, tree name, tree args, int flags,
                      bool *no_add_attrs)
{
  tree node = *pnode;
  bool is_dllimport;

  /* These attributes may apply to structure and union types being created,
     but otherwise should pass to the declaration involved.  */
  if (!DECL_P (node))
    {
      if (flags & ((int) ATTR_FLAG_DECL_NEXT | (int) ATTR_FLAG_FUNCTION_NEXT
                   | (int) ATTR_FLAG_ARRAY_NEXT))
        {
          *no_add_attrs = true;
          return tree_cons (name, args, NULL_TREE);
        }
      if (TREE_CODE (node) == RECORD_TYPE
          || TREE_CODE (node) == UNION_TYPE)
        {
          node = TYPE_NAME (node);
          if (!node)
            return NULL_TREE;
        }
      else
        {
          warning (OPT_Wattributes, "%qE attribute ignored",
                   name);
          *no_add_attrs = true;
          return NULL_TREE;
        }
    }

  if (!VAR_OR_FUNCTION_DECL_P (node) && TREE_CODE (node) != TYPE_DECL)
    {
      *no_add_attrs = true;
      warning (OPT_Wattributes, "%qE attribute ignored",
               name);
      return NULL_TREE;
    }

  if (TREE_CODE (node) == TYPE_DECL
      && TREE_CODE (TREE_TYPE (node)) != RECORD_TYPE
      && TREE_CODE (TREE_TYPE (node)) != UNION_TYPE)
    {
      *no_add_attrs = true;
      warning (OPT_Wattributes, "%qE attribute ignored",
               name);
      return NULL_TREE;
    }

  is_dllimport = is_attribute_p ("dllimport", name);

  /* Report error on dllimport ambiguities seen now before they cause
     any damage.  */
  if (is_dllimport)
    {
      /* Honor any target-specific overrides.  */
      if (!targetm.valid_dllimport_attribute_p (node))
        *no_add_attrs = true;

     else if (TREE_CODE (node) == FUNCTION_DECL
              && DECL_DECLARED_INLINE_P (node))
        {
          warning (OPT_Wattributes, "inline function %q+D declared as "
                  " dllimport: attribute ignored", node);
          *no_add_attrs = true;
        }
      /* Like MS, treat definition of dllimported variables and
         non-inlined functions on declaration as syntax errors.  */
     else if (TREE_CODE (node) == FUNCTION_DECL && DECL_INITIAL (node))
        {
          error ("function %q+D definition is marked dllimport", node);
          *no_add_attrs = true;
        }

     else if (VAR_P (node))
        {
          if (DECL_INITIAL (node))
            {
              error ("variable %q+D definition is marked dllimport",
                     node);
              *no_add_attrs = true;
            }

          /* `extern' needn't be specified with dllimport.
             Specify `extern' now and hope for the best.  Sigh.  */
          DECL_EXTERNAL (node) = 1;
          /* Also, implicitly give dllimport'd variables declared within
             a function global scope, unless declared static.  */
          if (current_function_decl != NULL_TREE && !TREE_STATIC (node))
            TREE_PUBLIC (node) = 1;
        }

      if (*no_add_attrs == false)
        DECL_DLLIMPORT_P (node) = 1;
    }
  else if (TREE_CODE (node) == FUNCTION_DECL
           && DECL_DECLARED_INLINE_P (node)
           && flag_keep_inline_dllexport)
    /* An exported function, even if inline, must be emitted.  */
    DECL_EXTERNAL (node) = 0;

  /*  Report error if symbol is not accessible at global scope.  */
  if (!TREE_PUBLIC (node) && VAR_OR_FUNCTION_DECL_P (node))
    {
      error ("external linkage required for symbol %q+D because of "
             "%qE attribute", node, name);
      *no_add_attrs = true;
    }

  /* A dllexport'd entity must have default visibility so that other
     program units (shared libraries or the main executable) can see
     it.  A dllimport'd entity must have default visibility so that
     the linker knows that undefined references within this program
     unit can be resolved by the dynamic linker.  */
  if (!*no_add_attrs)
    {
      if (DECL_VISIBILITY_SPECIFIED (node)
          && DECL_VISIBILITY (node) != VISIBILITY_DEFAULT)
        error ("%qE implies default visibility, but %qD has already "
               "been declared with a different visibility",
               name, node);
      DECL_VISIBILITY (node) = VISIBILITY_DEFAULT;
      DECL_VISIBILITY_SPECIFIED (node) = 1;
    }

  return NULL_TREE;
}

#endif /* TARGET_DLLIMPORT_DECL_ATTRIBUTES  */

/* Given two lists of attributes, return true if list l2 is
   equivalent to l1.  */

int
attribute_list_equal (const_tree l1, const_tree l2)
{
  if (l1 == l2)
    return 1;

  return attribute_list_contained (l1, l2)
         && attribute_list_contained (l2, l1);
}

/* Given two lists of attributes, return true if list L2 is
   completely contained within L1.  */
/* ??? This would be faster if attribute names were stored in a canonicalized
   form.  Otherwise, if L1 uses `foo' and L2 uses `__foo__', the long method
   must be used to show these elements are equivalent (which they are).  */
/* ??? It's not clear that attributes with arguments will always be handled
   correctly.  */

int
attribute_list_contained (const_tree l1, const_tree l2)
{
  const_tree t1, t2;

  /* First check the obvious, maybe the lists are identical.  */
  if (l1 == l2)
    return 1;

  /* Maybe the lists are similar.  */
  for (t1 = l1, t2 = l2;
       t1 != 0 && t2 != 0
       && get_attribute_name (t1) == get_attribute_name (t2)
       && TREE_VALUE (t1) == TREE_VALUE (t2);
       t1 = TREE_CHAIN (t1), t2 = TREE_CHAIN (t2))
    ;

  /* Maybe the lists are equal.  */
  if (t1 == 0 && t2 == 0)
    return 1;

  for (; t2 != 0; t2 = TREE_CHAIN (t2))
    {
      const_tree attr;
      /* This CONST_CAST is okay because lookup_attribute does not
         modify its argument and the return value is assigned to a
         const_tree.  */
      for (attr = lookup_ident_attribute (get_attribute_name (t2),
                                          CONST_CAST_TREE (l1));
           attr != NULL_TREE && !attribute_value_equal (t2, attr);
           attr = lookup_ident_attribute (get_attribute_name (t2),
                                          TREE_CHAIN (attr)))
        ;

      if (attr == NULL_TREE)
        return 0;
    }

  return 1;
}