re PR c++/66093 (g++ produces incorrect output on code with constexpr function initia...

[thirdparty/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_spec (get_identifier ("naked"))
      && lookup_attribute ("naked", attributes) != NULL)
    {
      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);
    }

  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;
  bool is_uniq = false;

  if (TREE_PUBLIC (decl) == 0)
    is_uniq = true;

  func_name = make_unique_name (decl, "ifunc", is_uniq);

  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);
}