Daily bump.

[thirdparty/gcc.git] / gcc / ipa-icf.c

/* Interprocedural Identical Code Folding pass
   Copyright (C) 2014-2015 Free Software Foundation, Inc.

   Contributed by Jan Hubicka <hubicka@ucw.cz> and Martin Liska <mliska@suse.cz>

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/>.  */

/* Interprocedural Identical Code Folding for functions and
   read-only variables.

   The goal of this transformation is to discover functions and read-only
   variables which do have exactly the same semantics.

   In case of functions,
   we could either create a virtual clone or do a simple function wrapper
   that will call equivalent function. If the function is just locally visible,
   all function calls can be redirected. For read-only variables, we create
   aliases if possible.

   Optimization pass arranges as follows:
   1) All functions and read-only variables are visited and internal
      data structure, either sem_function or sem_variables is created.
   2) For every symbol from the previous step, VAR_DECL and FUNCTION_DECL are
      saved and matched to corresponding sem_items.
   3) These declaration are ignored for equality check and are solved
      by Value Numbering algorithm published by Alpert, Zadeck in 1992.
   4) We compute hash value for each symbol.
   5) Congruence classes are created based on hash value. If hash value are
      equal, equals function is called and symbols are deeply compared.
      We must prove that all SSA names, declarations and other items
      correspond.
   6) Value Numbering is executed for these classes. At the end of the process
      all symbol members in remaining classes can be merged.
   7) Merge operation creates alias in case of read-only variables. For
      callgraph node, we must decide if we can redirect local calls,
      create an alias or a thunk.

*/

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "hash-set.h"
#include "machmode.h"
#include "vec.h"
#include "double-int.h"
#include "input.h"
#include "alias.h"
#include "symtab.h"
#include "options.h"
#include "wide-int.h"
#include "inchash.h"
#include "tree.h"
#include "fold-const.h"
#include "predict.h"
#include "tm.h"
#include "hard-reg-set.h"
#include "function.h"
#include "dominance.h"
#include "cfg.h"
#include "basic-block.h"
#include "tree-ssa-alias.h"
#include "internal-fn.h"
#include "gimple-expr.h"
#include "is-a.h"
#include "gimple.h"
#include "hashtab.h"
#include "rtl.h"
#include "flags.h"
#include "statistics.h"
#include "real.h"
#include "fixed-value.h"
#include "insn-config.h"
#include "expmed.h"
#include "dojump.h"
#include "explow.h"
#include "calls.h"
#include "emit-rtl.h"
#include "varasm.h"
#include "stmt.h"
#include "expr.h"
#include "gimple-iterator.h"
#include "gimple-ssa.h"
#include "tree-cfg.h"
#include "tree-phinodes.h"
#include "stringpool.h"
#include "tree-ssanames.h"
#include "tree-dfa.h"
#include "tree-pass.h"
#include "gimple-pretty-print.h"
#include "hash-map.h"
#include "plugin-api.h"
#include "ipa-ref.h"
#include "cgraph.h"
#include "alloc-pool.h"
#include "symbol-summary.h"
#include "ipa-prop.h"
#include "ipa-inline.h"
#include "cfgloop.h"
#include "except.h"
#include "hash-table.h"
#include "coverage.h"
#include "attribs.h"
#include "print-tree.h"
#include "lto-streamer.h"
#include "data-streamer.h"
#include "ipa-utils.h"
#include <list>
#include "ipa-icf-gimple.h"
#include "ipa-icf.h"

using namespace ipa_icf_gimple;

namespace ipa_icf {

/* Constructor.  */

symbol_compare_collection::symbol_compare_collection (symtab_node *node)
{
  m_references.create (0);
  m_interposables.create (0);

  ipa_ref *ref;

  if (is_a <varpool_node *> (node) && DECL_VIRTUAL_P (node->decl))
    return;

  for (unsigned i = 0; i < node->num_references (); i++)
    {
      ref = node->iterate_reference (i, ref);
      if (ref->address_matters_p ())
	m_references.safe_push (ref->referred);

      if (ref->referred->get_availability () <= AVAIL_INTERPOSABLE)
        {
	  if (ref->address_matters_p ())
	    m_references.safe_push (ref->referred);
	  else
	    m_interposables.safe_push (ref->referred);
	}
    }

  if (is_a <cgraph_node *> (node))
    {
      cgraph_node *cnode = dyn_cast <cgraph_node *> (node);

      for (cgraph_edge *e = cnode->callees; e; e = e->next_callee)
	if (e->callee->get_availability () <= AVAIL_INTERPOSABLE)
	  m_interposables.safe_push (e->callee);
    }
}

/* Constructor for key value pair, where _ITEM is key and _INDEX is a target.  */

sem_usage_pair::sem_usage_pair (sem_item *_item, unsigned int _index):
  item (_item), index (_index)
{
}

/* Semantic item constructor for a node of _TYPE, where STACK is used
   for bitmap memory allocation.  */

sem_item::sem_item (sem_item_type _type,
		    bitmap_obstack *stack): type(_type), hash(0)
{
  setup (stack);
}

/* Semantic item constructor for a node of _TYPE, where STACK is used
   for bitmap memory allocation. The item is based on symtab node _NODE
   with computed _HASH.  */

sem_item::sem_item (sem_item_type _type, symtab_node *_node,
		    hashval_t _hash, bitmap_obstack *stack): type(_type),
  node (_node), hash (_hash)
{
  decl = node->decl;
  setup (stack);
}

/* Add reference to a semantic TARGET.  */

void
sem_item::add_reference (sem_item *target)
{
  refs.safe_push (target);
  unsigned index = refs.length ();
  target->usages.safe_push (new sem_usage_pair(this, index));
  bitmap_set_bit (target->usage_index_bitmap, index);
  refs_set.add (target->node);
}

/* Initialize internal data structures. Bitmap STACK is used for
   bitmap memory allocation process.  */

void
sem_item::setup (bitmap_obstack *stack)
{
  gcc_checking_assert (node);

  refs.create (0);
  tree_refs.create (0);
  usages.create (0);
  usage_index_bitmap = BITMAP_ALLOC (stack);
}

sem_item::~sem_item ()
{
  for (unsigned i = 0; i < usages.length (); i++)
    delete usages[i];

  refs.release ();
  tree_refs.release ();
  usages.release ();

  BITMAP_FREE (usage_index_bitmap);
}

/* Dump function for debugging purpose.  */

DEBUG_FUNCTION void
sem_item::dump (void)
{
  if (dump_file)
    {
      fprintf (dump_file, "[%s] %s (%u) (tree:%p)\n", type == FUNC ? "func" : "var",
	       name(), node->order, (void *) node->decl);
      fprintf (dump_file, "  hash: %u\n", get_hash ());
      fprintf (dump_file, "  references: ");

      for (unsigned i = 0; i < refs.length (); i++)
	fprintf (dump_file, "%s%s ", refs[i]->name (),
		 i < refs.length() - 1 ? "," : "");

      fprintf (dump_file, "\n");
    }
}

/* Return true if target supports alias symbols.  */

bool
sem_item::target_supports_symbol_aliases_p (void)
{
#if !defined (ASM_OUTPUT_DEF) || (!defined(ASM_OUTPUT_WEAK_ALIAS) && !defined (ASM_WEAKEN_DECL))
  return false;
#else
  return true;
#endif
}

/* Semantic function constructor that uses STACK as bitmap memory stack.  */

sem_function::sem_function (bitmap_obstack *stack): sem_item (FUNC, stack),
  m_checker (NULL), m_compared_func (NULL)
{
  arg_types.create (0);
  bb_sizes.create (0);
  bb_sorted.create (0);
}

/*  Constructor based on callgraph node _NODE with computed hash _HASH.
    Bitmap STACK is used for memory allocation.  */
sem_function::sem_function (cgraph_node *node, hashval_t hash,
			    bitmap_obstack *stack):
  sem_item (FUNC, node, hash, stack),
  m_checker (NULL), m_compared_func (NULL)
{
  arg_types.create (0);
  bb_sizes.create (0);
  bb_sorted.create (0);
}

sem_function::~sem_function ()
{
  for (unsigned i = 0; i < bb_sorted.length (); i++)
    delete (bb_sorted[i]);

  arg_types.release ();
  bb_sizes.release ();
  bb_sorted.release ();
}

/* Calculates hash value based on a BASIC_BLOCK.  */

hashval_t
sem_function::get_bb_hash (const sem_bb *basic_block)
{
  inchash::hash hstate;

  hstate.add_int (basic_block->nondbg_stmt_count);
  hstate.add_int (basic_block->edge_count);

  return hstate.end ();
}

/* References independent hash function.  */

hashval_t
sem_function::get_hash (void)
{
  if(!hash)
    {
      inchash::hash hstate;
      hstate.add_int (177454); /* Random number for function type.  */

      hstate.add_int (arg_count);
      hstate.add_int (cfg_checksum);
      hstate.add_int (gcode_hash);

      for (unsigned i = 0; i < bb_sorted.length (); i++)
	hstate.merge_hash (get_bb_hash (bb_sorted[i]));

      for (unsigned i = 0; i < bb_sizes.length (); i++)
	hstate.add_int (bb_sizes[i]);

      hash = hstate.end ();
    }

  return hash;
}

/* For a given symbol table nodes N1 and N2, we check that FUNCTION_DECLs
   point to a same function. Comparison can be skipped if IGNORED_NODES
   contains these nodes.  ADDRESS indicate if address is taken.  */

bool
sem_function::compare_cgraph_references (
    hash_map <symtab_node *, sem_item *> &ignored_nodes,
    symtab_node *n1, symtab_node *n2, bool address)
{
  enum availability avail1, avail2;

  if (address && n1->equal_address_to (n2) == 1)
    return true;
  if (!address && n1->semantically_equivalent_p (n2))
    return true;

  n1 = n1->ultimate_alias_target (&avail1);
  n2 = n2->ultimate_alias_target (&avail2);

  if (avail1 >= AVAIL_INTERPOSABLE && ignored_nodes.get (n1)
      && avail2 >= AVAIL_INTERPOSABLE && ignored_nodes.get (n2))
    return true;

  return return_false_with_msg ("different references");
}

/* If cgraph edges E1 and E2 are indirect calls, verify that
   ECF flags are the same.  */

bool sem_function::compare_edge_flags (cgraph_edge *e1, cgraph_edge *e2)
{
  if (e1->indirect_info && e2->indirect_info)
    {
      int e1_flags = e1->indirect_info->ecf_flags;
      int e2_flags = e2->indirect_info->ecf_flags;

      if (e1_flags != e2_flags)
	return return_false_with_msg ("ICF flags are different");
    }
  else if (e1->indirect_info || e2->indirect_info)
    return false;

  return true;
}

/* Fast equality function based on knowledge known in WPA.  */

bool
sem_function::equals_wpa (sem_item *item,
			  hash_map <symtab_node *, sem_item *> &ignored_nodes)
{
  gcc_assert (item->type == FUNC);

  m_compared_func = static_cast<sem_function *> (item);

  if (arg_types.length () != m_compared_func->arg_types.length ())
    return return_false_with_msg ("different number of arguments");

  /* Checking types of arguments.  */
  for (unsigned i = 0; i < arg_types.length (); i++)
    {
      /* This guard is here for function pointer with attributes (pr59927.c).  */
      if (!arg_types[i] || !m_compared_func->arg_types[i])
	return return_false_with_msg ("NULL argument type");

      /* Polymorphic comparison is executed just for non-leaf functions.  */
      bool is_not_leaf = get_node ()->callees != NULL
			 || get_node ()->indirect_calls != NULL;

      if (!func_checker::compatible_types_p (arg_types[i],
					     m_compared_func->arg_types[i],
					     is_not_leaf, i == 0))
	return return_false_with_msg ("argument type is different");
    }

  /* Result type checking.  */
  if (!func_checker::compatible_types_p (result_type,
					 m_compared_func->result_type))
    return return_false_with_msg ("result types are different");

  if (node->num_references () != item->node->num_references ())
    return return_false_with_msg ("different number of references");

  ipa_ref *ref = NULL, *ref2 = NULL;
  for (unsigned i = 0; node->iterate_reference (i, ref); i++)
    {
      item->node->iterate_reference (i, ref2);

      if (!compare_cgraph_references (ignored_nodes, ref->referred,
				      ref2->referred,
				      ref->address_matters_p ()))
	return false;
    }

  cgraph_edge *e1 = dyn_cast <cgraph_node *> (node)->callees;
  cgraph_edge *e2 = dyn_cast <cgraph_node *> (item->node)->callees;

  while (e1 && e2)
    {
      if (!compare_cgraph_references (ignored_nodes, e1->callee,
				      e2->callee, false))
	return false;

      e1 = e1->next_callee;
      e2 = e2->next_callee;
    }

  if (e1 || e2)
    return return_false_with_msg ("different number of edges");

  return true;
}

/* Returns true if the item equals to ITEM given as argument.  */

bool
sem_function::equals (sem_item *item,
		      hash_map <symtab_node *, sem_item *> &ignored_nodes)
{
  gcc_assert (item->type == FUNC);
  bool eq = equals_private (item, ignored_nodes);

  if (m_checker != NULL)
    {
      delete m_checker;
      m_checker = NULL;
    }

  if (dump_file && (dump_flags & TDF_DETAILS))
    fprintf (dump_file,
	     "Equals called for:%s:%s (%u:%u) (%s:%s) with result: %s\n\n",
	     name(), item->name (), node->order, item->node->order, asm_name (),
	     item->asm_name (), eq ? "true" : "false");

  return eq;
}

/* Processes function equality comparison.  */

bool
sem_function::equals_private (sem_item *item,
			      hash_map <symtab_node *, sem_item *> &ignored_nodes)
{
  if (item->type != FUNC)
    return false;

  basic_block bb1, bb2;
  edge e1, e2;
  edge_iterator ei1, ei2;
  bool result = true;
  tree arg1, arg2;

  m_compared_func = static_cast<sem_function *> (item);

  gcc_assert (decl != item->decl);

  if (bb_sorted.length () != m_compared_func->bb_sorted.length ()
      || edge_count != m_compared_func->edge_count
      || cfg_checksum != m_compared_func->cfg_checksum)
    return return_false ();

  if (!equals_wpa (item, ignored_nodes))
    return false;

  /* Checking function TARGET and OPTIMIZATION flags.  */
  cl_target_option *tar1 = target_opts_for_fn (decl);
  cl_target_option *tar2 = target_opts_for_fn (m_compared_func->decl);

  if (tar1 != NULL && tar2 != NULL)
    {
      if (!cl_target_option_eq (tar1, tar2))
	{
	  if (dump_file && (dump_flags & TDF_DETAILS))
	    {
	      fprintf (dump_file, "target flags difference");
	      cl_target_option_print_diff (dump_file, 2, tar1, tar2);
	    }

	  return return_false_with_msg ("Target flags are different");
	}
    }
  else if (tar1 != NULL || tar2 != NULL)
    return return_false_with_msg ("Target flags are different");

  cl_optimization *opt1 = opts_for_fn (decl);
  cl_optimization *opt2 = opts_for_fn (m_compared_func->decl);

  if (opt1 != NULL && opt2 != NULL)
    {
      if (memcmp (opt1, opt2, sizeof(cl_optimization)))
	{
	  if (dump_file && (dump_flags & TDF_DETAILS))
	    {
	      fprintf (dump_file, "optimization flags difference");
	      cl_optimization_print_diff (dump_file, 2, opt1, opt2);
	    }

	  return return_false_with_msg ("optimization flags are different");
	}
    }
  else if (opt1 != NULL || opt2 != NULL)
    return return_false_with_msg ("optimization flags are different");

  /* Checking function arguments.  */
  tree decl1 = DECL_ATTRIBUTES (decl);
  tree decl2 = DECL_ATTRIBUTES (m_compared_func->decl);

  m_checker = new func_checker (decl, m_compared_func->decl,
				compare_polymorphic_p (),
				false,
				&refs_set,
				&m_compared_func->refs_set);
  while (decl1)
    {
      if (decl2 == NULL)
	return return_false ();

      if (get_attribute_name (decl1) != get_attribute_name (decl2))
	return return_false ();

      tree attr_value1 = TREE_VALUE (decl1);
      tree attr_value2 = TREE_VALUE (decl2);

      if (attr_value1 && attr_value2)
	{
	  bool ret = m_checker->compare_operand (TREE_VALUE (attr_value1),
						 TREE_VALUE (attr_value2));
	  if (!ret)
	    return return_false_with_msg ("attribute values are different");
	}
      else if (!attr_value1 && !attr_value2)
	{}
      else
	return return_false ();

      decl1 = TREE_CHAIN (decl1);
      decl2 = TREE_CHAIN (decl2);
    }

  if (decl1 != decl2)
    return return_false();


  for (arg1 = DECL_ARGUMENTS (decl),
       arg2 = DECL_ARGUMENTS (m_compared_func->decl);
       arg1; arg1 = DECL_CHAIN (arg1), arg2 = DECL_CHAIN (arg2))
    if (!m_checker->compare_decl (arg1, arg2))
      return return_false ();

  /* Fill-up label dictionary.  */
  for (unsigned i = 0; i < bb_sorted.length (); ++i)
    {
      m_checker->parse_labels (bb_sorted[i]);
      m_checker->parse_labels (m_compared_func->bb_sorted[i]);
    }

  /* Checking all basic blocks.  */
  for (unsigned i = 0; i < bb_sorted.length (); ++i)
    if(!m_checker->compare_bb (bb_sorted[i], m_compared_func->bb_sorted[i]))
      return return_false();

  dump_message ("All BBs are equal\n");

  auto_vec <int> bb_dict;

  /* Basic block edges check.  */
  for (unsigned i = 0; i < bb_sorted.length (); ++i)
    {
      bb1 = bb_sorted[i]->bb;
      bb2 = m_compared_func->bb_sorted[i]->bb;

      ei2 = ei_start (bb2->preds);

      for (ei1 = ei_start (bb1->preds); ei_cond (ei1, &e1); ei_next (&ei1))
	{
	  ei_cond (ei2, &e2);

	  if (e1->flags != e2->flags)
	    return return_false_with_msg ("flags comparison returns false");

	  if (!bb_dict_test (&bb_dict, e1->src->index, e2->src->index))
	    return return_false_with_msg ("edge comparison returns false");

	  if (!bb_dict_test (&bb_dict, e1->dest->index, e2->dest->index))
	    return return_false_with_msg ("BB comparison returns false");

	  if (!m_checker->compare_edge (e1, e2))
	    return return_false_with_msg ("edge comparison returns false");

	  ei_next (&ei2);
	}
    }

  /* Basic block PHI nodes comparison.  */
  for (unsigned i = 0; i < bb_sorted.length (); i++)
    if (!compare_phi_node (bb_sorted[i]->bb, m_compared_func->bb_sorted[i]->bb))
      return return_false_with_msg ("PHI node comparison returns false");

  /* Compare special function DECL attributes.  */
  if (DECL_FUNCTION_PERSONALITY (decl) != DECL_FUNCTION_PERSONALITY (item->decl))
    return return_false_with_msg ("function personalities are different");

  if (DECL_DISREGARD_INLINE_LIMITS (decl) != DECL_DISREGARD_INLINE_LIMITS (item->decl))
    return return_false_with_msg ("DECL_DISREGARD_INLINE_LIMITS are different");

  if (DECL_DECLARED_INLINE_P (decl) != DECL_DECLARED_INLINE_P (item->decl))
    return return_false_with_msg ("inline attributes are different");

  if (DECL_IS_OPERATOR_NEW (decl) != DECL_IS_OPERATOR_NEW (item->decl))
    return return_false_with_msg ("operator new flags are different");

  if (DECL_NO_INSTRUMENT_FUNCTION_ENTRY_EXIT (decl)
       != DECL_NO_INSTRUMENT_FUNCTION_ENTRY_EXIT (item->decl))
    return return_false_with_msg ("intrument function entry exit "
				  "attributes are different");

  if (DECL_NO_LIMIT_STACK (decl) != DECL_NO_LIMIT_STACK (item->decl))
    return return_false_with_msg ("no stack limit attributes are different");

  if (flags_from_decl_or_type (decl) != flags_from_decl_or_type (item->decl))
    return return_false_with_msg ("decl_or_type flags are different");

  return result;
}

/* Set LOCAL_P of NODE to true if DATA is non-NULL.
   Helper for call_for_symbol_thunks_and_aliases.  */

static bool
set_local (cgraph_node *node, void *data)
{
  node->local.local = data != NULL;
  return false;
}

/* TREE_ADDRESSABLE of NODE to true.
   Helper for call_for_symbol_thunks_and_aliases.  */

static bool
set_addressable (varpool_node *node, void *)
{
  TREE_ADDRESSABLE (node->decl) = 1;
  return false;
}

/* Clear DECL_RTL of NODE. 
   Helper for call_for_symbol_thunks_and_aliases.  */

static bool
clear_decl_rtl (symtab_node *node, void *)
{
  SET_DECL_RTL (node->decl, NULL);
  return false;
}

/* Redirect all callers of N and its aliases to TO.  Remove aliases if
   possible.  Return number of redirections made.  */

static int
redirect_all_callers (cgraph_node *n, cgraph_node *to)
{
  int nredirected = 0;
  ipa_ref *ref;

  while (n->callers)
    {
      cgraph_edge *e = n->callers;
      e->redirect_callee (to);
      nredirected++;
    }
  for (unsigned i = 0; n->iterate_direct_aliases (i, ref);)
    {
      bool removed = false;
      cgraph_node *n_alias = dyn_cast <cgraph_node *> (ref->referring);

      if ((DECL_COMDAT_GROUP (n->decl)
	   && (DECL_COMDAT_GROUP (n->decl)
	       == DECL_COMDAT_GROUP (n_alias->decl)))
	  || (n_alias->get_availability () > AVAIL_INTERPOSABLE
	      && n->get_availability () > AVAIL_INTERPOSABLE))
	{
	  nredirected += redirect_all_callers (n_alias, to);
	  if (n_alias->can_remove_if_no_direct_calls_p ()
	      && !n_alias->has_aliases_p ())
	    n_alias->remove ();
	}
      if (!removed)
	i++;
    }
  return nredirected;
}

/* Merges instance with an ALIAS_ITEM, where alias, thunk or redirection can
   be applied.  */

bool
sem_function::merge (sem_item *alias_item)
{
  gcc_assert (alias_item->type == FUNC);

  sem_function *alias_func = static_cast<sem_function *> (alias_item);

  cgraph_node *original = get_node ();
  cgraph_node *local_original = NULL;
  cgraph_node *alias = alias_func->get_node ();

  bool create_wrapper = false;
  bool create_alias = false;
  bool redirect_callers = false;
  bool remove = false;

  bool original_discardable = false;
  bool original_discarded = false;

  bool original_address_matters = original->address_matters_p ();
  bool alias_address_matters = alias->address_matters_p ();

  if (DECL_NO_INLINE_WARNING_P (original->decl)
      != DECL_NO_INLINE_WARNING_P (alias->decl))
    {
      if (dump_file)
	fprintf (dump_file,
		 "Not unifying; "
		 "DECL_NO_INLINE_WARNING mismatch.\n\n");
      return false;
    }

  /* Do not attempt to mix functions from different user sections;
     we do not know what user intends with those.  */
  if (((DECL_SECTION_NAME (original->decl) && !original->implicit_section)
       || (DECL_SECTION_NAME (alias->decl) && !alias->implicit_section))
      && DECL_SECTION_NAME (original->decl) != DECL_SECTION_NAME (alias->decl))
    {
      if (dump_file)
	fprintf (dump_file,
		 "Not unifying; "
		 "original and alias are in different sections.\n\n");
      return false;
    }

  /* See if original is in a section that can be discarded if the main
     symbol is not used.  */

  if (original->can_be_discarded_p ())
    original_discardable = true;
  /* Also consider case where we have resolution info and we know that
     original's definition is not going to be used.  In this case we can not
     create alias to original.  */
  if (node->resolution != LDPR_UNKNOWN
      && !decl_binds_to_current_def_p (node->decl))
    original_discardable = original_discarded = true;

  /* Creating a symtab alias is the optimal way to merge.
     It however can not be used in the following cases:

     1) if ORIGINAL and ALIAS may be possibly compared for address equality.
     2) if ORIGINAL is in a section that may be discarded by linker or if
	it is an external functions where we can not create an alias
	(ORIGINAL_DISCARDABLE)
     3) if target do not support symbol aliases.
     4) original and alias lie in different comdat groups.

     If we can not produce alias, we will turn ALIAS into WRAPPER of ORIGINAL
     and/or redirect all callers from ALIAS to ORIGINAL.  */
  if ((original_address_matters && alias_address_matters)
      || (original_discardable
	  && (!DECL_COMDAT_GROUP (alias->decl)
	      || (DECL_COMDAT_GROUP (alias->decl)
		  != DECL_COMDAT_GROUP (original->decl))))
      || original_discarded
      || !sem_item::target_supports_symbol_aliases_p ()
      || DECL_COMDAT_GROUP (alias->decl) != DECL_COMDAT_GROUP (original->decl))
    {
      /* First see if we can produce wrapper.  */

      /* Do not turn function in one comdat group into wrapper to another
	 comdat group. Other compiler producing the body of the
	 another comdat group may make opossite decision and with unfortunate
	 linker choices this may close a loop.  */
      if (DECL_COMDAT_GROUP (original->decl) && DECL_COMDAT_GROUP (alias->decl)
	  && (DECL_COMDAT_GROUP (alias->decl)
	      != DECL_COMDAT_GROUP (original->decl)))
	{
	  if (dump_file)
	    fprintf (dump_file,
		     "Wrapper cannot be created because of COMDAT\n");
	}
      else if (DECL_STATIC_CHAIN (alias->decl))
        {
	  if (dump_file)
	    fprintf (dump_file,
		     "Can not create wrapper of nested functions.\n");
        }
      /* TODO: We can also deal with variadic functions never calling
	 VA_START.  */
      else if (stdarg_p (TREE_TYPE (alias->decl)))
	{
	  if (dump_file)
	    fprintf (dump_file,
		     "can not create wrapper of stdarg function.\n");
	}
      else if (inline_summaries
	       && inline_summaries->get (alias)->self_size <= 2)
	{
	  if (dump_file)
	    fprintf (dump_file, "Wrapper creation is not "
		     "profitable (function is too small).\n");
	}
      /* If user paid attention to mark function noinline, assume it is
	 somewhat special and do not try to turn it into a wrapper that can
	 not be undone by inliner.  */
      else if (lookup_attribute ("noinline", DECL_ATTRIBUTES (alias->decl)))
	{
	  if (dump_file)
	    fprintf (dump_file, "Wrappers are not created for noinline.\n");
	}
      else
        create_wrapper = true;

      /* We can redirect local calls in the case both alias and orignal
	 are not interposable.  */
      redirect_callers
	= alias->get_availability () > AVAIL_INTERPOSABLE
	  && original->get_availability () > AVAIL_INTERPOSABLE
	  && !alias->instrumented_version;

      if (!redirect_callers && !create_wrapper)
	{
	  if (dump_file)
	    fprintf (dump_file, "Not unifying; can not redirect callers nor "
		     "produce wrapper\n\n");
	  return false;
	}

      /* Work out the symbol the wrapper should call.
	 If ORIGINAL is interposable, we need to call a local alias.
	 Also produce local alias (if possible) as an optimization.

	 Local aliases can not be created inside comdat groups because that
	 prevents inlining.  */
      if (!original_discardable && !original->get_comdat_group ())
	{
	  local_original
	    = dyn_cast <cgraph_node *> (original->noninterposable_alias ());
	  if (!local_original
	      && original->get_availability () > AVAIL_INTERPOSABLE)
	    local_original = original;
	}
      /* If we can not use local alias, fallback to the original
	 when possible.  */
      else if (original->get_availability () > AVAIL_INTERPOSABLE)
	local_original = original;

      /* If original is COMDAT local, we can not really redirect calls outside
	 of its comdat group to it.  */
      if (original->comdat_local_p ())
        redirect_callers = false;
      if (!local_original)
	{
	  if (dump_file)
	    fprintf (dump_file, "Not unifying; "
		     "can not produce local alias.\n\n");
	  return false;
	}

      if (!redirect_callers && !create_wrapper)
	{
	  if (dump_file)
	    fprintf (dump_file, "Not unifying; "
		     "can not redirect callers nor produce a wrapper\n\n");
	  return false;
	}
      if (!create_wrapper
	  && !alias->can_remove_if_no_direct_calls_p ())
	{
	  if (dump_file)
	    fprintf (dump_file, "Not unifying; can not make wrapper and "
		     "function has other uses than direct calls\n\n");
	  return false;
	}
    }
  else
    create_alias = true;

  if (redirect_callers)
    {
      int nredirected = redirect_all_callers (alias, local_original);

      if (nredirected)
	{
	  alias->icf_merged = true;
	  local_original->icf_merged = true;

	  if (dump_file && nredirected)
	    fprintf (dump_file, "%i local calls have been "
		     "redirected.\n", nredirected);
	}

      /* If all callers was redirected, do not produce wrapper.  */
      if (alias->can_remove_if_no_direct_calls_p ()
	  && !alias->has_aliases_p ())
	{
	  create_wrapper = false;
	  remove = true;
	}
      gcc_assert (!create_alias);
    }
  else if (create_alias)
    {
      alias->icf_merged = true;

      /* Remove the function's body.  */
      ipa_merge_profiles (original, alias);
      alias->release_body (true);
      alias->reset ();
      /* Notice global symbol possibly produced RTL.  */
      ((symtab_node *)alias)->call_for_symbol_and_aliases (clear_decl_rtl,
							   NULL, true);

      /* Create the alias.  */
      cgraph_node::create_alias (alias_func->decl, decl);
      alias->resolve_alias (original);

      original->call_for_symbol_thunks_and_aliases
	 (set_local, (void *)(size_t) original->local_p (), true);

      if (dump_file)
	fprintf (dump_file, "Unified; Function alias has been created.\n\n");
    }
  if (create_wrapper)
    {
      gcc_assert (!create_alias);
      alias->icf_merged = true;
      local_original->icf_merged = true;

      ipa_merge_profiles (local_original, alias, true);
      alias->create_wrapper (local_original);

      if (dump_file)
	fprintf (dump_file, "Unified; Wrapper has been created.\n\n");
    }
  gcc_assert (alias->icf_merged || remove);
  original->icf_merged = true;

  /* Inform the inliner about cross-module merging.  */
  if ((original->lto_file_data || alias->lto_file_data)
      && original->lto_file_data != alias->lto_file_data)
    local_original->merged = original->merged = true;

  if (remove)
    {
      ipa_merge_profiles (original, alias);
      alias->release_body ();
      alias->reset ();
      alias->body_removed = true;
      alias->icf_merged = true;
      if (dump_file)
	fprintf (dump_file, "Unified; Function body was removed.\n");
    }

  return true;
}

/* Semantic item initialization function.  */

void
sem_function::init (void)
{
  if (in_lto_p)
    get_node ()->get_untransformed_body ();

  tree fndecl = node->decl;
  function *func = DECL_STRUCT_FUNCTION (fndecl);

  gcc_assert (func);
  gcc_assert (SSANAMES (func));

  ssa_names_size = SSANAMES (func)->length ();
  node = node;

  decl = fndecl;
  region_tree = func->eh->region_tree;

  /* iterating all function arguments.  */
  arg_count = count_formal_params (fndecl);

  edge_count = n_edges_for_fn (func);
  cfg_checksum = coverage_compute_cfg_checksum (func);

  inchash::hash hstate;

  basic_block bb;
  FOR_EACH_BB_FN (bb, func)
  {
    unsigned nondbg_stmt_count = 0;

    edge e;
    for (edge_iterator ei = ei_start (bb->preds); ei_cond (ei, &e);
	 ei_next (&ei))
      cfg_checksum = iterative_hash_host_wide_int (e->flags,
		     cfg_checksum);

    for (gimple_stmt_iterator gsi = gsi_start_bb (bb); !gsi_end_p (gsi);
	 gsi_next (&gsi))
      {
	gimple stmt = gsi_stmt (gsi);

	if (gimple_code (stmt) != GIMPLE_DEBUG
	    && gimple_code (stmt) != GIMPLE_PREDICT)
	  {
	    hash_stmt (stmt, hstate);
	    nondbg_stmt_count++;
	  }
      }

    gcode_hash = hstate.end ();
    bb_sizes.safe_push (nondbg_stmt_count);

    /* Inserting basic block to hash table.  */
    sem_bb *semantic_bb = new sem_bb (bb, nondbg_stmt_count,
				      EDGE_COUNT (bb->preds)
				      + EDGE_COUNT (bb->succs));

    bb_sorted.safe_push (semantic_bb);
  }

  parse_tree_args ();
}

/* Accumulate to HSTATE a hash of expression EXP.
   Identical to inchash::add_expr, but guaranteed to be stable across LTO
   and DECL equality classes.  */

void
sem_item::add_expr (const_tree exp, inchash::hash &hstate)
{
  if (exp == NULL_TREE)
    {
      hstate.merge_hash (0);
      return;
    }

  /* Handled component can be matched in a cureful way proving equivalence
     even if they syntactically differ.  Just skip them.  */
  STRIP_NOPS (exp);
  while (handled_component_p (exp))
    exp = TREE_OPERAND (exp, 0);

  enum tree_code code = TREE_CODE (exp);
  hstate.add_int (code);

  switch (code)
    {
    /* Use inchash::add_expr for everything that is LTO stable.  */
    case VOID_CST:
    case INTEGER_CST:
    case REAL_CST:
    case FIXED_CST:
    case STRING_CST:
    case COMPLEX_CST:
    case VECTOR_CST:
      inchash::add_expr (exp, hstate);
      break;
    case CONSTRUCTOR:
      {
	unsigned HOST_WIDE_INT idx;
	tree value;

	hstate.add_wide_int (int_size_in_bytes (TREE_TYPE (exp)));

	FOR_EACH_CONSTRUCTOR_VALUE (CONSTRUCTOR_ELTS (exp), idx, value)
	  if (value)
	    add_expr (value, hstate);
	break;
      }
    case ADDR_EXPR:
    case FDESC_EXPR:
      add_expr (get_base_address (TREE_OPERAND (exp, 0)), hstate);
      break;
    case SSA_NAME:
    case VAR_DECL:
    case CONST_DECL:
    case PARM_DECL:
      hstate.add_wide_int (int_size_in_bytes (TREE_TYPE (exp)));
      break;
    case MEM_REF:
    case POINTER_PLUS_EXPR:
    case MINUS_EXPR:
    case RANGE_EXPR:
      add_expr (TREE_OPERAND (exp, 0), hstate);
      add_expr (TREE_OPERAND (exp, 1), hstate);
      break;
    case PLUS_EXPR:
      {
	inchash::hash one, two;
	add_expr (TREE_OPERAND (exp, 0), one);
	add_expr (TREE_OPERAND (exp, 1), two);
	hstate.add_commutative (one, two);
      }
      break;
    CASE_CONVERT:
      hstate.add_wide_int (int_size_in_bytes (TREE_TYPE (exp)));
      return add_expr (TREE_OPERAND (exp, 0), hstate);
    default:
      break;
    }
}

/* Improve accumulated hash for HSTATE based on a gimple statement STMT.  */

void
sem_function::hash_stmt (gimple stmt, inchash::hash &hstate)
{
  enum gimple_code code = gimple_code (stmt);

  hstate.add_int (code);

  switch (code)
    {
    case GIMPLE_ASSIGN:
      if (commutative_tree_code (gimple_assign_rhs_code (stmt))
	  || commutative_ternary_tree_code (gimple_assign_rhs_code (stmt)))
	{
	  inchash::hash one, two;

	  add_expr (gimple_assign_rhs1 (stmt), one);
	  add_expr (gimple_assign_rhs2 (stmt), two);
	  hstate.add_commutative (one, two);
	  add_expr (gimple_assign_lhs (stmt), hstate);
	  break;
	}
      /* ... fall through ... */
    case GIMPLE_CALL:
    case GIMPLE_ASM:
    case GIMPLE_COND:
    case GIMPLE_GOTO:
    case GIMPLE_RETURN:
      /* All these statements are equivalent if their operands are.  */
      for (unsigned i = 0; i < gimple_num_ops (stmt); ++i)
	add_expr (gimple_op (stmt, i), hstate);
    default:
      break;
    }
}


/* Return true if polymorphic comparison must be processed.  */

bool
sem_function::compare_polymorphic_p (void)
{
  return get_node ()->callees != NULL
	 || get_node ()->indirect_calls != NULL
	 || m_compared_func->get_node ()->callees != NULL
	 || m_compared_func->get_node ()->indirect_calls != NULL;
}

/* For a given call graph NODE, the function constructs new
   semantic function item.  */

sem_function *
sem_function::parse (cgraph_node *node, bitmap_obstack *stack)
{
  tree fndecl = node->decl;
  function *func = DECL_STRUCT_FUNCTION (fndecl);

  /* TODO: add support for thunks.  */

  if (!func || !node->has_gimple_body_p ())
    return NULL;

  if (lookup_attribute_by_prefix ("omp ", DECL_ATTRIBUTES (node->decl)) != NULL)
    return NULL;

  sem_function *f = new sem_function (node, 0, stack);

  f->init ();

  return f;
}

/* Parses function arguments and result type.  */

void
sem_function::parse_tree_args (void)
{
  tree result;

  if (arg_types.exists ())
    arg_types.release ();

  arg_types.create (4);
  tree fnargs = DECL_ARGUMENTS (decl);

  for (tree parm = fnargs; parm; parm = DECL_CHAIN (parm))
    arg_types.safe_push (DECL_ARG_TYPE (parm));

  /* Function result type.  */
  result = DECL_RESULT (decl);
  result_type = result ? TREE_TYPE (result) : NULL;

  /* During WPA, we can get arguments by following method.  */
  if (!fnargs)
    {
      tree type = TYPE_ARG_TYPES (TREE_TYPE (decl));
      for (tree parm = type; parm; parm = TREE_CHAIN (parm))
	arg_types.safe_push (TYPE_CANONICAL (TREE_VALUE (parm)));

      result_type = TREE_TYPE (TREE_TYPE (decl));
    }
}

/* For given basic blocks BB1 and BB2 (from functions FUNC1 and FUNC),
   return true if phi nodes are semantically equivalent in these blocks .  */

bool
sem_function::compare_phi_node (basic_block bb1, basic_block bb2)
{
  gphi_iterator si1, si2;
  gphi *phi1, *phi2;
  unsigned size1, size2, i;
  tree t1, t2;
  edge e1, e2;

  gcc_assert (bb1 != NULL);
  gcc_assert (bb2 != NULL);

  si2 = gsi_start_phis (bb2);
  for (si1 = gsi_start_phis (bb1); !gsi_end_p (si1);
       gsi_next (&si1))
    {
      gsi_next_nonvirtual_phi (&si1);
      gsi_next_nonvirtual_phi (&si2);

      if (gsi_end_p (si1) && gsi_end_p (si2))
	break;

      if (gsi_end_p (si1) || gsi_end_p (si2))
	return return_false();

      phi1 = si1.phi ();
      phi2 = si2.phi ();

      tree phi_result1 = gimple_phi_result (phi1);
      tree phi_result2 = gimple_phi_result (phi2);

      if (!m_checker->compare_operand (phi_result1, phi_result2))
	return return_false_with_msg ("PHI results are different");

      size1 = gimple_phi_num_args (phi1);
      size2 = gimple_phi_num_args (phi2);

      if (size1 != size2)
	return return_false ();

      for (i = 0; i < size1; ++i)
	{
	  t1 = gimple_phi_arg (phi1, i)->def;
	  t2 = gimple_phi_arg (phi2, i)->def;

	  if (!m_checker->compare_operand (t1, t2))
	    return return_false ();

	  e1 = gimple_phi_arg_edge (phi1, i);
	  e2 = gimple_phi_arg_edge (phi2, i);

	  if (!m_checker->compare_edge (e1, e2))
	    return return_false ();
	}

      gsi_next (&si2);
    }

  return true;
}

/* Returns true if tree T can be compared as a handled component.  */

bool
sem_function::icf_handled_component_p (tree t)
{
  tree_code tc = TREE_CODE (t);

  return ((handled_component_p (t))
	  || tc == ADDR_EXPR || tc == MEM_REF || tc == REALPART_EXPR
	  || tc == IMAGPART_EXPR || tc == OBJ_TYPE_REF);
}

/* Basic blocks dictionary BB_DICT returns true if SOURCE index BB
   corresponds to TARGET.  */

bool
sem_function::bb_dict_test (vec<int> *bb_dict, int source, int target)
{
  source++;
  target++;

  if (bb_dict->length () <= (unsigned)source)
    bb_dict->safe_grow_cleared (source + 1);

  if ((*bb_dict)[source] == 0)
    {
      (*bb_dict)[source] = target;
      return true;
    }
  else
    return (*bb_dict)[source] == target;
}

/* Iterates all tree types in T1 and T2 and returns true if all types
   are compatible. If COMPARE_POLYMORPHIC is set to true,
   more strict comparison is executed.  */

bool
sem_function::compare_type_list (tree t1, tree t2, bool compare_polymorphic)
{
  tree tv1, tv2;
  tree_code tc1, tc2;

  if (!t1 && !t2)
    return true;

  while (t1 != NULL && t2 != NULL)
    {
      tv1 = TREE_VALUE (t1);
      tv2 = TREE_VALUE (t2);

      tc1 = TREE_CODE (tv1);
      tc2 = TREE_CODE (tv2);

      if (tc1 == NOP_EXPR && tc2 == NOP_EXPR)
	{}
      else if (tc1 == NOP_EXPR || tc2 == NOP_EXPR)
	return false;
      else if (!func_checker::compatible_types_p (tv1, tv2, compare_polymorphic))
	return false;

      t1 = TREE_CHAIN (t1);
      t2 = TREE_CHAIN (t2);
    }

  return !(t1 || t2);
}


/* Semantic variable constructor that uses STACK as bitmap memory stack.  */

sem_variable::sem_variable (bitmap_obstack *stack): sem_item (VAR, stack)
{
}

/*  Constructor based on varpool node _NODE with computed hash _HASH.
    Bitmap STACK is used for memory allocation.  */

sem_variable::sem_variable (varpool_node *node, hashval_t _hash,
			    bitmap_obstack *stack): sem_item(VAR,
				  node, _hash, stack)
{
  gcc_checking_assert (node);
  gcc_checking_assert (get_node ());
}

/* Returns true if the item equals to ITEM given as argument.  */

bool
sem_variable::equals (sem_item *item,
		      hash_map <symtab_node *, sem_item *> & ARG_UNUSED (ignored_nodes))
{
  gcc_assert (item->type == VAR);

  sem_variable *v = static_cast<sem_variable *>(item);

  if (!ctor || !v->ctor)
    return return_false_with_msg ("ctor is missing for semantic variable");

  if (DECL_IN_CONSTANT_POOL (decl)
      && (DECL_IN_CONSTANT_POOL (item->decl)
	  || item->node->address_matters_p ()))
    return return_false_with_msg ("constant pool");

  if (DECL_IN_TEXT_SECTION (decl) != DECL_IN_TEXT_SECTION (item->decl))
    return return_false_with_msg ("text section");

  if (DECL_TLS_MODEL (decl) || DECL_TLS_MODEL (item->decl))
    return return_false_with_msg ("TLS model");

  return sem_variable::equals (ctor, v->ctor);
}

/* Compares trees T1 and T2 for semantic equality.  */

bool
sem_variable::equals (tree t1, tree t2)
{
  tree_code tc1 = TREE_CODE (t1);
  tree_code tc2 = TREE_CODE (t2);

  if (tc1 != tc2)
    return false;

  switch (tc1)
    {
    case CONSTRUCTOR:
      {
	unsigned len1 = vec_safe_length (CONSTRUCTOR_ELTS (t1));
	unsigned len2 = vec_safe_length (CONSTRUCTOR_ELTS (t2));

	if (len1 != len2)
	  return false;

	for (unsigned i = 0; i < len1; i++)
	  if (!sem_variable::equals (CONSTRUCTOR_ELT (t1, i)->value,
				     CONSTRUCTOR_ELT (t2, i)->value)
	      || CONSTRUCTOR_ELT (t1, i)->index != CONSTRUCTOR_ELT (t2, i)->index)
	    return false;

	return true;
      }
    case MEM_REF:
      {
	tree x1 = TREE_OPERAND (t1, 0);
	tree x2 = TREE_OPERAND (t2, 0);
	tree y1 = TREE_OPERAND (t1, 1);
	tree y2 = TREE_OPERAND (t2, 1);

	if (!func_checker::compatible_types_p (TREE_TYPE (x1), TREE_TYPE (x2),
					       true))
	  return return_false ();

	/* Type of the offset on MEM_REF does not matter.  */
	return sem_variable::equals (x1, x2)
	       && wi::to_offset  (y1) == wi::to_offset  (y2);
      }
    case NOP_EXPR:
    case ADDR_EXPR:
      {
	tree op1 = TREE_OPERAND (t1, 0);
	tree op2 = TREE_OPERAND (t2, 0);
	return sem_variable::equals (op1, op2);
      }
    case FUNCTION_DECL:
    case VAR_DECL:
    case FIELD_DECL:
    case LABEL_DECL:
      return t1 == t2;
    case INTEGER_CST:
      return func_checker::compatible_types_p (TREE_TYPE (t1), TREE_TYPE (t2),
	     true)
	     && wi::to_offset (t1) == wi::to_offset (t2);
    case STRING_CST:
    case REAL_CST:
    case COMPLEX_CST:
      return operand_equal_p (t1, t2, OEP_ONLY_CONST);
    case COMPONENT_REF:
    case ARRAY_REF:
    case POINTER_PLUS_EXPR:
      {
	tree x1 = TREE_OPERAND (t1, 0);
	tree x2 = TREE_OPERAND (t2, 0);
	tree y1 = TREE_OPERAND (t1, 1);
	tree y2 = TREE_OPERAND (t2, 1);

	return sem_variable::equals (x1, x2) && sem_variable::equals (y1, y2);
      }
    case ERROR_MARK:
      return return_false_with_msg ("ERROR_MARK");
    default:
      return return_false_with_msg ("Unknown TREE code reached");
    }
}

/* Parser function that visits a varpool NODE.  */

sem_variable *
sem_variable::parse (varpool_node *node, bitmap_obstack *stack)
{
  tree decl = node->decl;

  if (node->alias)
    return NULL;

  bool readonly = TYPE_P (decl) ? TYPE_READONLY (decl) : TREE_READONLY (decl);
  if (!readonly)
    return NULL;

  bool can_handle = DECL_VIRTUAL_P (decl)
		    || flag_merge_constants >= 2
		    || (!TREE_ADDRESSABLE (decl) && !node->externally_visible);

  if (!can_handle || DECL_EXTERNAL (decl))
    return NULL;

  tree ctor = ctor_for_folding (decl);
  if (!ctor)
    return NULL;

  sem_variable *v = new sem_variable (node, 0, stack);

  v->init ();

  return v;
}

/* References independent hash function.  */

hashval_t
sem_variable::get_hash (void)
{
  if (hash)
    return hash;

  /* All WPA streamed in symbols should have their hashes computed at compile
     time.  At this point, the constructor may not be in memory at all.
     DECL_INITIAL (decl) would be error_mark_node in that case.  */
  gcc_assert (!node->lto_file_data);
  tree ctor = DECL_INITIAL (decl);
  inchash::hash hstate;

  hstate.add_int (456346417);
  if (DECL_SIZE (decl) && tree_fits_shwi_p (DECL_SIZE (decl)))
    hstate.add_wide_int (tree_to_shwi (DECL_SIZE (decl)));
  add_expr (ctor, hstate);
  hash = hstate.end ();

  return hash;
}

/* Merges instance with an ALIAS_ITEM, where alias, thunk or redirection can
   be applied.  */

bool
sem_variable::merge (sem_item *alias_item)
{
  gcc_assert (alias_item->type == VAR);

  if (!sem_item::target_supports_symbol_aliases_p ())
    {
      if (dump_file)
	fprintf (dump_file, "Not unifying; "
		 "Symbol aliases are not supported by target\n\n");
      return false;
    }

  sem_variable *alias_var = static_cast<sem_variable *> (alias_item);

  varpool_node *original = get_node ();
  varpool_node *alias = alias_var->get_node ();
  bool original_discardable = false;

  bool original_address_matters = original->address_matters_p ();
  bool alias_address_matters = alias->address_matters_p ();

  /* See if original is in a section that can be discarded if the main
     symbol is not used.
     Also consider case where we have resolution info and we know that
     original's definition is not going to be used.  In this case we can not
     create alias to original.  */
  if (original->can_be_discarded_p ()
      || (node->resolution != LDPR_UNKNOWN
	  && !decl_binds_to_current_def_p (node->decl)))
    original_discardable = true;

  gcc_assert (!TREE_ASM_WRITTEN (alias->decl));

  /* Constant pool machinery is not quite ready for aliases.
     TODO: varasm code contains logic for merging DECL_IN_CONSTANT_POOL.
     For LTO merging does not happen that is an important missing feature.
     We can enable merging with LTO if the DECL_IN_CONSTANT_POOL
     flag is dropped and non-local symbol name is assigned.  */
  if (DECL_IN_CONSTANT_POOL (alias->decl)
      || DECL_IN_CONSTANT_POOL (original->decl))
    {
      if (dump_file)
	fprintf (dump_file,
		 "Not unifying; constant pool variables.\n\n");
      return false;
    }

  /* Do not attempt to mix functions from different user sections;
     we do not know what user intends with those.  */
  if (((DECL_SECTION_NAME (original->decl) && !original->implicit_section)
       || (DECL_SECTION_NAME (alias->decl) && !alias->implicit_section))
      && DECL_SECTION_NAME (original->decl) != DECL_SECTION_NAME (alias->decl))
    {
      if (dump_file)
	fprintf (dump_file,
		 "Not unifying; "
		 "original and alias are in different sections.\n\n");
      return false;
    }

  /* We can not merge if address comparsion metters.  */
  if (original_address_matters && alias_address_matters
      && flag_merge_constants < 2)
    {
      if (dump_file)
	fprintf (dump_file,
		 "Not unifying; "
		 "adress of original and alias may be compared.\n\n");
      return false;
    }
  if (DECL_COMDAT_GROUP (original->decl) != DECL_COMDAT_GROUP (alias->decl))
    {
      if (dump_file)
	fprintf (dump_file, "Not unifying; alias cannot be created; "
		 "across comdat group boundary\n\n");

      return false;
    }

  if (original_discardable)
    {
      if (dump_file)
	fprintf (dump_file, "Not unifying; alias cannot be created; "
		 "target is discardable\n\n");

      return false;
    }
  else
    {
      gcc_assert (!original->alias);
      gcc_assert (!alias->alias);

      alias->analyzed = false;

      DECL_INITIAL (alias->decl) = NULL;
      ((symtab_node *)alias)->call_for_symbol_and_aliases (clear_decl_rtl,
							   NULL, true);
      alias->need_bounds_init = false;
      alias->remove_all_references ();
      if (TREE_ADDRESSABLE (alias->decl))
        original->call_for_symbol_and_aliases (set_addressable, NULL, true);

      varpool_node::create_alias (alias_var->decl, decl);
      alias->resolve_alias (original);

      if (dump_file)
	fprintf (dump_file, "Unified; Variable alias has been created.\n\n");

      return true;
    }
}

/* Dump symbol to FILE.  */

void
sem_variable::dump_to_file (FILE *file)
{
  gcc_assert (file);

  print_node (file, "", decl, 0);
  fprintf (file, "\n\n");
}

/* Iterates though a constructor and identifies tree references
   we are interested in semantic function equality.  */

void
sem_variable::parse_tree_refs (tree t)
{
  switch (TREE_CODE (t))
    {
    case CONSTRUCTOR:
      {
	unsigned length = vec_safe_length (CONSTRUCTOR_ELTS (t));

	for (unsigned i = 0; i < length; i++)
	  parse_tree_refs(CONSTRUCTOR_ELT (t, i)->value);

	break;
      }
    case NOP_EXPR:
    case ADDR_EXPR:
      {
	tree op = TREE_OPERAND (t, 0);
	parse_tree_refs (op);
	break;
      }
    case FUNCTION_DECL:
      {
	tree_refs.safe_push (t);
	break;
      }
    default:
      break;
    }
}

unsigned int sem_item_optimizer::class_id = 0;

sem_item_optimizer::sem_item_optimizer (): worklist (0), m_classes (0),
  m_classes_count (0), m_cgraph_node_hooks (NULL), m_varpool_node_hooks (NULL)
{
  m_items.create (0);
  bitmap_obstack_initialize (&m_bmstack);
}

sem_item_optimizer::~sem_item_optimizer ()
{
  for (unsigned int i = 0; i < m_items.length (); i++)
    delete m_items[i];

  for (hash_table<congruence_class_group_hash>::iterator it = m_classes.begin ();
       it != m_classes.end (); ++it)
    {
      for (unsigned int i = 0; i < (*it)->classes.length (); i++)
	delete (*it)->classes[i];

      (*it)->classes.release ();
      free (*it);
    }

  m_items.release ();

  bitmap_obstack_release (&m_bmstack);
}

/* Write IPA ICF summary for symbols.  */

void
sem_item_optimizer::write_summary (void)
{
  unsigned int count = 0;

  output_block *ob = create_output_block (LTO_section_ipa_icf);
  lto_symtab_encoder_t encoder = ob->decl_state->symtab_node_encoder;
  ob->symbol = NULL;

  /* Calculate number of symbols to be serialized.  */
  for (lto_symtab_encoder_iterator lsei = lsei_start_in_partition (encoder);
       !lsei_end_p (lsei);
       lsei_next_in_partition (&lsei))
    {
      symtab_node *node = lsei_node (lsei);

      if (m_symtab_node_map.get (node))
	count++;
    }

  streamer_write_uhwi (ob, count);

  /* Process all of the symbols.  */
  for (lto_symtab_encoder_iterator lsei = lsei_start_in_partition (encoder);
       !lsei_end_p (lsei);
       lsei_next_in_partition (&lsei))
    {
      symtab_node *node = lsei_node (lsei);

      sem_item **item = m_symtab_node_map.get (node);

      if (item && *item)
	{
	  int node_ref = lto_symtab_encoder_encode (encoder, node);
	  streamer_write_uhwi_stream (ob->main_stream, node_ref);

	  streamer_write_uhwi (ob, (*item)->get_hash ());
	}
    }

  streamer_write_char_stream (ob->main_stream, 0);
  produce_asm (ob, NULL);
  destroy_output_block (ob);
}

/* Reads a section from LTO stream file FILE_DATA. Input block for DATA
   contains LEN bytes.  */

void
sem_item_optimizer::read_section (lto_file_decl_data *file_data,
				  const char *data, size_t len)
{
  const lto_function_header *header =
    (const lto_function_header *) data;
  const int cfg_offset = sizeof (lto_function_header);
  const int main_offset = cfg_offset + header->cfg_size;
  const int string_offset = main_offset + header->main_size;
  data_in *data_in;
  unsigned int i;
  unsigned int count;

  lto_input_block ib_main ((const char *) data + main_offset, 0,
			   header->main_size, file_data->mode_table);

  data_in =
    lto_data_in_create (file_data, (const char *) data + string_offset,
			header->string_size, vNULL);

  count = streamer_read_uhwi (&ib_main);

  for (i = 0; i < count; i++)
    {
      unsigned int index;
      symtab_node *node;
      lto_symtab_encoder_t encoder;

      index = streamer_read_uhwi (&ib_main);
      encoder = file_data->symtab_node_encoder;
      node = lto_symtab_encoder_deref (encoder, index);

      hashval_t hash = streamer_read_uhwi (&ib_main);

      gcc_assert (node->definition);

      if (dump_file)
	fprintf (dump_file, "Symbol added:%s (tree: %p, uid:%u)\n", node->asm_name (),
		 (void *) node->decl, node->order);

      if (is_a<cgraph_node *> (node))
	{
	  cgraph_node *cnode = dyn_cast <cgraph_node *> (node);

	  m_items.safe_push (new sem_function (cnode, hash, &m_bmstack));
	}
      else
	{
	  varpool_node *vnode = dyn_cast <varpool_node *> (node);

	  m_items.safe_push (new sem_variable (vnode, hash, &m_bmstack));
	}
    }

  lto_free_section_data (file_data, LTO_section_ipa_icf, NULL, data,
			 len);
  lto_data_in_delete (data_in);
}

/* Read IPA IPA ICF summary for symbols.  */

void
sem_item_optimizer::read_summary (void)
{
  lto_file_decl_data **file_data_vec = lto_get_file_decl_data ();
  lto_file_decl_data *file_data;
  unsigned int j = 0;

  while ((file_data = file_data_vec[j++]))
    {
      size_t len;
      const char *data = lto_get_section_data (file_data,
			 LTO_section_ipa_icf, NULL, &len);

      if (data)
	read_section (file_data, data, len);
    }
}

/* Register callgraph and varpool hooks.  */

void
sem_item_optimizer::register_hooks (void)
{
  if (!m_cgraph_node_hooks)
    m_cgraph_node_hooks = symtab->add_cgraph_removal_hook
			  (&sem_item_optimizer::cgraph_removal_hook, this);

  if (!m_varpool_node_hooks)
    m_varpool_node_hooks = symtab->add_varpool_removal_hook
			   (&sem_item_optimizer::varpool_removal_hook, this);
}

/* Unregister callgraph and varpool hooks.  */

void
sem_item_optimizer::unregister_hooks (void)
{
  if (m_cgraph_node_hooks)
    symtab->remove_cgraph_removal_hook (m_cgraph_node_hooks);

  if (m_varpool_node_hooks)
    symtab->remove_varpool_removal_hook (m_varpool_node_hooks);
}

/* Adds a CLS to hashtable associated by hash value.  */

void
sem_item_optimizer::add_class (congruence_class *cls)
{
  gcc_assert (cls->members.length ());

  congruence_class_group *group = get_group_by_hash (
				    cls->members[0]->get_hash (),
				    cls->members[0]->type);
  group->classes.safe_push (cls);
}

/* Gets a congruence class group based on given HASH value and TYPE.  */

congruence_class_group *
sem_item_optimizer::get_group_by_hash (hashval_t hash, sem_item_type type)
{
  congruence_class_group *item = XNEW (congruence_class_group);
  item->hash = hash;
  item->type = type;

  congruence_class_group **slot = m_classes.find_slot (item, INSERT);

  if (*slot)
    free (item);
  else
    {
      item->classes.create (1);
      *slot = item;
    }

  return *slot;
}

/* Callgraph removal hook called for a NODE with a custom DATA.  */

void
sem_item_optimizer::cgraph_removal_hook (cgraph_node *node, void *data)
{
  sem_item_optimizer *optimizer = (sem_item_optimizer *) data;
  optimizer->remove_symtab_node (node);
}

/* Varpool removal hook called for a NODE with a custom DATA.  */

void
sem_item_optimizer::varpool_removal_hook (varpool_node *node, void *data)
{
  sem_item_optimizer *optimizer = (sem_item_optimizer *) data;
  optimizer->remove_symtab_node (node);
}

/* Remove symtab NODE triggered by symtab removal hooks.  */

void
sem_item_optimizer::remove_symtab_node (symtab_node *node)
{
  gcc_assert (!m_classes.elements());

  m_removed_items_set.add (node);
}

void
sem_item_optimizer::remove_item (sem_item *item)
{
  if (m_symtab_node_map.get (item->node))
    m_symtab_node_map.remove (item->node);
  delete item;
}

/* Removes all callgraph and varpool nodes that are marked by symtab
   as deleted.  */

void
sem_item_optimizer::filter_removed_items (void)
{
  auto_vec <sem_item *> filtered;

  for (unsigned int i = 0; i < m_items.length(); i++)
    {
      sem_item *item = m_items[i];

      if (m_removed_items_set.contains (item->node))
        {
	  remove_item (item);
	  continue;
        }

      if (item->type == FUNC)
        {
	  cgraph_node *cnode = static_cast <sem_function *>(item)->get_node ();

	  bool no_body_function = in_lto_p && (cnode->alias || cnode->body_removed);
	  if (no_body_function || !opt_for_fn (item->decl, flag_ipa_icf_functions)
	      || DECL_CXX_CONSTRUCTOR_P (item->decl)
	      || DECL_CXX_DESTRUCTOR_P (item->decl))
	    remove_item (item);
	  else
	    filtered.safe_push (item);
        }
      else /* VAR.  */
        {
	  if (!flag_ipa_icf_variables)
	    remove_item (item);
	  else
	    filtered.safe_push (item);
        }
    }

  /* Clean-up of released semantic items.  */

  m_items.release ();
  for (unsigned int i = 0; i < filtered.length(); i++)
    m_items.safe_push (filtered[i]);
}

/* Optimizer entry point.  */

void
sem_item_optimizer::execute (void)
{
  filter_removed_items ();
  unregister_hooks ();

  build_hash_based_classes ();

  if (dump_file)
    fprintf (dump_file, "Dump after hash based groups\n");
  dump_cong_classes ();

  for (unsigned int i = 0; i < m_items.length(); i++)
    m_items[i]->init_wpa ();

  build_graph ();

  subdivide_classes_by_equality (true);

  if (dump_file)
    fprintf (dump_file, "Dump after WPA based types groups\n");

  dump_cong_classes ();

  process_cong_reduction ();
  verify_classes ();

  if (dump_file)
    fprintf (dump_file, "Dump after callgraph-based congruence reduction\n");

  dump_cong_classes ();

  parse_nonsingleton_classes ();
  subdivide_classes_by_equality ();

  if (dump_file)
    fprintf (dump_file, "Dump after full equality comparison of groups\n");

  dump_cong_classes ();

  unsigned int prev_class_count = m_classes_count;

  process_cong_reduction ();
  dump_cong_classes ();
  verify_classes ();
  merge_classes (prev_class_count);

  if (dump_file && (dump_flags & TDF_DETAILS))
    symtab_node::dump_table (dump_file);
}

/* Function responsible for visiting all potential functions and
   read-only variables that can be merged.  */

void
sem_item_optimizer::parse_funcs_and_vars (void)
{
  cgraph_node *cnode;

  if (flag_ipa_icf_functions)
    FOR_EACH_DEFINED_FUNCTION (cnode)
    {
      sem_function *f = sem_function::parse (cnode, &m_bmstack);
      if (f)
	{
	  m_items.safe_push (f);
	  m_symtab_node_map.put (cnode, f);

	  if (dump_file)
	    fprintf (dump_file, "Parsed function:%s\n", f->asm_name ());

	  if (dump_file && (dump_flags & TDF_DETAILS))
	    f->dump_to_file (dump_file);
	}
      else if (dump_file)
	fprintf (dump_file, "Not parsed function:%s\n", cnode->asm_name ());
    }

  varpool_node *vnode;

  if (flag_ipa_icf_variables)
    FOR_EACH_DEFINED_VARIABLE (vnode)
    {
      sem_variable *v = sem_variable::parse (vnode, &m_bmstack);

      if (v)
	{
	  m_items.safe_push (v);
	  m_symtab_node_map.put (vnode, v);
	}
    }
}

/* Makes pairing between a congruence class CLS and semantic ITEM.  */

void
sem_item_optimizer::add_item_to_class (congruence_class *cls, sem_item *item)
{
  item->index_in_class = cls->members.length ();
  cls->members.safe_push (item);
  item->cls = cls;
}

/* Congruence classes are built by hash value.  */

void
sem_item_optimizer::build_hash_based_classes (void)
{
  for (unsigned i = 0; i < m_items.length (); i++)
    {
      sem_item *item = m_items[i];

      congruence_class_group *group = get_group_by_hash (item->get_hash (),
				      item->type);

      if (!group->classes.length ())
	{
	  m_classes_count++;
	  group->classes.safe_push (new congruence_class (class_id++));
	}

      add_item_to_class (group->classes[0], item);
    }
}

/* Build references according to call graph.  */

void
sem_item_optimizer::build_graph (void)
{
  for (unsigned i = 0; i < m_items.length (); i++)
    {
      sem_item *item = m_items[i];
      m_symtab_node_map.put (item->node, item);
    }

  for (unsigned i = 0; i < m_items.length (); i++)
    {
      sem_item *item = m_items[i];

      if (item->type == FUNC)
	{
	  cgraph_node *cnode = dyn_cast <cgraph_node *> (item->node);

	  cgraph_edge *e = cnode->callees;
	  while (e)
	    {
	      sem_item **slot = m_symtab_node_map.get
		(e->callee->ultimate_alias_target ());
	      if (slot)
		item->add_reference (*slot);

	      e = e->next_callee;
	    }
	}

      ipa_ref *ref = NULL;
      for (unsigned i = 0; item->node->iterate_reference (i, ref); i++)
	{
	  sem_item **slot = m_symtab_node_map.get
	    (ref->referred->ultimate_alias_target ());
	  if (slot)
	    item->add_reference (*slot);
	}
    }
}

/* Semantic items in classes having more than one element and initialized.
   In case of WPA, we load function body.  */

void
sem_item_optimizer::parse_nonsingleton_classes (void)
{
  unsigned int init_called_count = 0;

  for (unsigned i = 0; i < m_items.length (); i++)
    if (m_items[i]->cls->members.length () > 1)
      {
	m_items[i]->init ();
	init_called_count++;
      }

  if (dump_file)
    fprintf (dump_file, "Init called for %u items (%.2f%%).\n", init_called_count,
	     m_items.length () ? 100.0f * init_called_count / m_items.length (): 0.0f);
}

/* Equality function for semantic items is used to subdivide existing
   classes. If IN_WPA, fast equality function is invoked.  */

void
sem_item_optimizer::subdivide_classes_by_equality (bool in_wpa)
{
  for (hash_table <congruence_class_group_hash>::iterator it = m_classes.begin ();
       it != m_classes.end (); ++it)
    {
      unsigned int class_count = (*it)->classes.length ();

      for (unsigned i = 0; i < class_count; i++)
	{
	  congruence_class *c = (*it)->classes [i];

	  if (c->members.length() > 1)
	    {
	      auto_vec <sem_item *> new_vector;

	      sem_item *first = c->members[0];
	      new_vector.safe_push (first);

	      unsigned class_split_first = (*it)->classes.length ();

	      for (unsigned j = 1; j < c->members.length (); j++)
		{
		  sem_item *item = c->members[j];

		  bool equals = in_wpa ? first->equals_wpa (item,
				m_symtab_node_map) : first->equals (item, m_symtab_node_map);

		  if (equals)
		    new_vector.safe_push (item);
		  else
		    {
		      bool integrated = false;

		      for (unsigned k = class_split_first; k < (*it)->classes.length (); k++)
			{
			  sem_item *x = (*it)->classes[k]->members[0];
			  bool equals = in_wpa ? x->equals_wpa (item,
								m_symtab_node_map) : x->equals (item, m_symtab_node_map);

			  if (equals)
			    {
			      integrated = true;
			      add_item_to_class ((*it)->classes[k], item);

			      break;
			    }
			}

		      if (!integrated)
			{
			  congruence_class *c = new congruence_class (class_id++);
			  m_classes_count++;
			  add_item_to_class (c, item);

			  (*it)->classes.safe_push (c);
			}
		    }
		}

	      // we replace newly created new_vector for the class we've just splitted
	      c->members.release ();
	      c->members.create (new_vector.length ());

	      for (unsigned int j = 0; j < new_vector.length (); j++)
		add_item_to_class (c, new_vector[j]);
	    }
	}
    }

  verify_classes ();
}

/* Subdivide classes by address references that members of the class
   reference. Example can be a pair of functions that have an address
   taken from a function. If these addresses are different the class
   is split.  */

unsigned
sem_item_optimizer::subdivide_classes_by_sensitive_refs ()
{
  unsigned newly_created_classes = 0;

  for (hash_table <congruence_class_group_hash>::iterator it = m_classes.begin ();
       it != m_classes.end (); ++it)
    {
      unsigned int class_count = (*it)->classes.length ();
      auto_vec<congruence_class *> new_classes;

      for (unsigned i = 0; i < class_count; i++)
	{
	  congruence_class *c = (*it)->classes [i];

	  if (c->members.length() > 1)
	    {
	      hash_map <symbol_compare_collection *, vec <sem_item *>,
		symbol_compare_hashmap_traits> split_map;

	      for (unsigned j = 0; j < c->members.length (); j++)
	        {
		  sem_item *source_node = c->members[j];

		  symbol_compare_collection *collection = new symbol_compare_collection (source_node->node);

		  vec <sem_item *> *slot = &split_map.get_or_insert (collection);
		  gcc_checking_assert (slot);

		  slot->safe_push (source_node);
	        }

	       /* If the map contains more than one key, we have to split the map
		  appropriately.  */
	      if (split_map.elements () != 1)
	        {
		  bool first_class = true;

		  hash_map <symbol_compare_collection *, vec <sem_item *>,
		  symbol_compare_hashmap_traits>::iterator it2 = split_map.begin ();
		  for (; it2 != split_map.end (); ++it2)
		    {
		      congruence_class *new_cls;
		      new_cls = new congruence_class (class_id++);

		      for (unsigned k = 0; k < (*it2).second.length (); k++)
			add_item_to_class (new_cls, (*it2).second[k]);

		      worklist_push (new_cls);
		      newly_created_classes++;

		      if (first_class)
		        {
			  (*it)->classes[i] = new_cls;
			  first_class = false;
			}
		      else
		        {
		          new_classes.safe_push (new_cls);
			  m_classes_count++;
		        }
		    }
		}
	    }
	  }

	for (unsigned i = 0; i < new_classes.length (); i++)
	  (*it)->classes.safe_push (new_classes[i]);
    }

  return newly_created_classes;
}

/* Verify congruence classes if checking is enabled.  */

void
sem_item_optimizer::verify_classes (void)
{
#if ENABLE_CHECKING
  for (hash_table <congruence_class_group_hash>::iterator it = m_classes.begin ();
       it != m_classes.end (); ++it)
    {
      for (unsigned int i = 0; i < (*it)->classes.length (); i++)
	{
	  congruence_class *cls = (*it)->classes[i];

	  gcc_checking_assert (cls);
	  gcc_checking_assert (cls->members.length () > 0);

	  for (unsigned int j = 0; j < cls->members.length (); j++)
	    {
	      sem_item *item = cls->members[j];

	      gcc_checking_assert (item);
	      gcc_checking_assert (item->cls == cls);

	      for (unsigned k = 0; k < item->usages.length (); k++)
		{
		  sem_usage_pair *usage = item->usages[k];
		  gcc_checking_assert (usage->item->index_in_class <
				       usage->item->cls->members.length ());
		}
	    }
	}
    }
#endif
}

/* Disposes split map traverse function. CLS_PTR is pointer to congruence
   class, BSLOT is bitmap slot we want to release. DATA is mandatory,
   but unused argument.  */

bool
sem_item_optimizer::release_split_map (congruence_class * const &,
				       bitmap const &b, traverse_split_pair *)
{
  bitmap bmp = b;

  BITMAP_FREE (bmp);

  return true;
}

/* Process split operation for a class given as pointer CLS_PTR,
   where bitmap B splits congruence class members. DATA is used
   as argument of split pair.  */

bool
sem_item_optimizer::traverse_congruence_split (congruence_class * const &cls,
    bitmap const &b, traverse_split_pair *pair)
{
  sem_item_optimizer *optimizer = pair->optimizer;
  const congruence_class *splitter_cls = pair->cls;

  /* If counted bits are greater than zero and less than the number of members
     a group will be splitted.  */
  unsigned popcount = bitmap_count_bits (b);

  if (popcount > 0 && popcount < cls->members.length ())
    {
      congruence_class* newclasses[2] = { new congruence_class (class_id++), new congruence_class (class_id++) };

      for (unsigned int i = 0; i < cls->members.length (); i++)
	{
	  int target = bitmap_bit_p (b, i);
	  congruence_class *tc = newclasses[target];

	  add_item_to_class (tc, cls->members[i]);
	}

#ifdef ENABLE_CHECKING
      for (unsigned int i = 0; i < 2; i++)
	gcc_checking_assert (newclasses[i]->members.length ());
#endif

      if (splitter_cls == cls)
	optimizer->splitter_class_removed = true;

      /* Remove old class from worklist if presented.  */
      bool in_worklist = cls->in_worklist;

      if (in_worklist)
	cls->in_worklist = false;

      congruence_class_group g;
      g.hash = cls->members[0]->get_hash ();
      g.type = cls->members[0]->type;

      congruence_class_group *slot = optimizer->m_classes.find(&g);

      for (unsigned int i = 0; i < slot->classes.length (); i++)
	if (slot->classes[i] == cls)
	  {
	    slot->classes.ordered_remove (i);
	    break;
	  }

      /* New class will be inserted and integrated to work list.  */
      for (unsigned int i = 0; i < 2; i++)
	optimizer->add_class (newclasses[i]);

      /* Two classes replace one, so that increment just by one.  */
      optimizer->m_classes_count++;

      /* If OLD class was presented in the worklist, we remove the class
         and replace it will both newly created classes.  */
      if (in_worklist)
	for (unsigned int i = 0; i < 2; i++)
	  optimizer->worklist_push (newclasses[i]);
      else /* Just smaller class is inserted.  */
	{
	  unsigned int smaller_index = newclasses[0]->members.length () <
				       newclasses[1]->members.length () ?
				       0 : 1;
	  optimizer->worklist_push (newclasses[smaller_index]);
	}

      if (dump_file && (dump_flags & TDF_DETAILS))
	{
	  fprintf (dump_file, "  congruence class splitted:\n");
	  cls->dump (dump_file, 4);

	  fprintf (dump_file, "  newly created groups:\n");
	  for (unsigned int i = 0; i < 2; i++)
	    newclasses[i]->dump (dump_file, 4);
	}

      /* Release class if not presented in work list.  */
      if (!in_worklist)
	delete cls;
    }


  return true;
}

/* Tests if a class CLS used as INDEXth splits any congruence classes.
   Bitmap stack BMSTACK is used for bitmap allocation.  */

void
sem_item_optimizer::do_congruence_step_for_index (congruence_class *cls,
    unsigned int index)
{
  hash_map <congruence_class *, bitmap> split_map;

  for (unsigned int i = 0; i < cls->members.length (); i++)
    {
      sem_item *item = cls->members[i];

      /* Iterate all usages that have INDEX as usage of the item.  */
      for (unsigned int j = 0; j < item->usages.length (); j++)
	{
	  sem_usage_pair *usage = item->usages[j];

	  if (usage->index != index)
	    continue;

	  bitmap *slot = split_map.get (usage->item->cls);
	  bitmap b;

	  if(!slot)
	    {
	      b = BITMAP_ALLOC (&m_bmstack);
	      split_map.put (usage->item->cls, b);
	    }
	  else
	    b = *slot;

#if ENABLE_CHECKING
	  gcc_checking_assert (usage->item->cls);
	  gcc_checking_assert (usage->item->index_in_class <
			       usage->item->cls->members.length ());
#endif

	  bitmap_set_bit (b, usage->item->index_in_class);
	}
    }

  traverse_split_pair pair;
  pair.optimizer = this;
  pair.cls = cls;

  splitter_class_removed = false;
  split_map.traverse
  <traverse_split_pair *, sem_item_optimizer::traverse_congruence_split> (&pair);

  /* Bitmap clean-up.  */
  split_map.traverse
  <traverse_split_pair *, sem_item_optimizer::release_split_map> (NULL);
}

/* Every usage of a congruence class CLS is a candidate that can split the
   collection of classes. Bitmap stack BMSTACK is used for bitmap
   allocation.  */

void
sem_item_optimizer::do_congruence_step (congruence_class *cls)
{
  bitmap_iterator bi;
  unsigned int i;

  bitmap usage = BITMAP_ALLOC (&m_bmstack);

  for (unsigned int i = 0; i < cls->members.length (); i++)
    bitmap_ior_into (usage, cls->members[i]->usage_index_bitmap);

  EXECUTE_IF_SET_IN_BITMAP (usage, 0, i, bi)
  {
    if (dump_file && (dump_flags & TDF_DETAILS))
      fprintf (dump_file, "  processing congruece step for class: %u, index: %u\n",
	       cls->id, i);

    do_congruence_step_for_index (cls, i);

    if (splitter_class_removed)
      break;
  }

  BITMAP_FREE (usage);
}

/* Adds a newly created congruence class CLS to worklist.  */

void
sem_item_optimizer::worklist_push (congruence_class *cls)
{
  /* Return if the class CLS is already presented in work list.  */
  if (cls->in_worklist)
    return;

  cls->in_worklist = true;
  worklist.push_back (cls);
}

/* Pops a class from worklist. */

congruence_class *
sem_item_optimizer::worklist_pop (void)
{
  congruence_class *cls;

  while (!worklist.empty ())
    {
      cls = worklist.front ();
      worklist.pop_front ();
      if (cls->in_worklist)
	{
	  cls->in_worklist = false;

	  return cls;
	}
      else
	{
	  /* Work list item was already intended to be removed.
	     The only reason for doing it is to split a class.
	     Thus, the class CLS is deleted.  */
	  delete cls;
	}
    }

  return NULL;
}

/* Iterative congruence reduction function.  */

void
sem_item_optimizer::process_cong_reduction (void)
{
  for (hash_table<congruence_class_group_hash>::iterator it = m_classes.begin ();
       it != m_classes.end (); ++it)
    for (unsigned i = 0; i < (*it)->classes.length (); i++)
      if ((*it)->classes[i]->is_class_used ())
	worklist_push ((*it)->classes[i]);

  if (dump_file)
    fprintf (dump_file, "Worklist has been filled with: %lu\n",
	     (unsigned long) worklist.size ());

  if (dump_file && (dump_flags & TDF_DETAILS))
    fprintf (dump_file, "Congruence class reduction\n");

  congruence_class *cls;

  /* Process complete congruence reduction.  */
  while ((cls = worklist_pop ()) != NULL)
    do_congruence_step (cls);

  /* Subdivide newly created classes according to references.  */
  unsigned new_classes = subdivide_classes_by_sensitive_refs ();

  if (dump_file)
    fprintf (dump_file, "Address reference subdivision created: %u "
	     "new classes.\n", new_classes);
}

/* Debug function prints all informations about congruence classes.  */

void
sem_item_optimizer::dump_cong_classes (void)
{
  if (!dump_file)
    return;

  fprintf (dump_file,
	   "Congruence classes: %u (unique hash values: %lu), with total: %u items\n",
	   m_classes_count, (unsigned long) m_classes.elements(), m_items.length ());

  /* Histogram calculation.  */
  unsigned int max_index = 0;
  unsigned int* histogram = XCNEWVEC (unsigned int, m_items.length () + 1);

  for (hash_table<congruence_class_group_hash>::iterator it = m_classes.begin ();
       it != m_classes.end (); ++it)

    for (unsigned i = 0; i < (*it)->classes.length (); i++)
      {
	unsigned int c = (*it)->classes[i]->members.length ();
	histogram[c]++;

	if (c > max_index)
	  max_index = c;
      }

  fprintf (dump_file,
	   "Class size histogram [num of members]: number of classe number of classess\n");

  for (unsigned int i = 0; i <= max_index; i++)
    if (histogram[i])
      fprintf (dump_file, "[%u]: %u classes\n", i, histogram[i]);

  fprintf (dump_file, "\n\n");


  if (dump_flags & TDF_DETAILS)
    for (hash_table<congruence_class_group_hash>::iterator it = m_classes.begin ();
	 it != m_classes.end (); ++it)
      {
	fprintf (dump_file, "  group: with %u classes:\n", (*it)->classes.length ());

	for (unsigned i = 0; i < (*it)->classes.length (); i++)
	  {
	    (*it)->classes[i]->dump (dump_file, 4);

	    if(i < (*it)->classes.length () - 1)
	      fprintf (dump_file, " ");
	  }
      }

  free (histogram);
}

/* After reduction is done, we can declare all items in a group
   to be equal. PREV_CLASS_COUNT is start number of classes
   before reduction.  */

void
sem_item_optimizer::merge_classes (unsigned int prev_class_count)
{
  unsigned int item_count = m_items.length ();
  unsigned int class_count = m_classes_count;
  unsigned int equal_items = item_count - class_count;

  unsigned int non_singular_classes_count = 0;
  unsigned int non_singular_classes_sum = 0;

  for (hash_table<congruence_class_group_hash>::iterator it = m_classes.begin ();
       it != m_classes.end (); ++it)
    for (unsigned int i = 0; i < (*it)->classes.length (); i++)
      {
	congruence_class *c = (*it)->classes[i];
	if (c->members.length () > 1)
	  {
	    non_singular_classes_count++;
	    non_singular_classes_sum += c->members.length ();
	  }
      }

  if (dump_file)
    {
      fprintf (dump_file, "\nItem count: %u\n", item_count);
      fprintf (dump_file, "Congruent classes before: %u, after: %u\n",
	       prev_class_count, class_count);
      fprintf (dump_file, "Average class size before: %.2f, after: %.2f\n",
	       prev_class_count ? 1.0f * item_count / prev_class_count : 0.0f,
	       class_count ? 1.0f * item_count / class_count : 0.0f);
      fprintf (dump_file, "Average non-singular class size: %.2f, count: %u\n",
	       non_singular_classes_count ? 1.0f * non_singular_classes_sum /
	       non_singular_classes_count : 0.0f,
	       non_singular_classes_count);
      fprintf (dump_file, "Equal symbols: %u\n", equal_items);
      fprintf (dump_file, "Fraction of visited symbols: %.2f%%\n\n",
	       item_count ? 100.0f * equal_items / item_count : 0.0f);
    }

  for (hash_table<congruence_class_group_hash>::iterator it = m_classes.begin ();
       it != m_classes.end (); ++it)
    for (unsigned int i = 0; i < (*it)->classes.length (); i++)
      {
	congruence_class *c = (*it)->classes[i];

	if (c->members.length () == 1)
	  continue;

	gcc_assert (c->members.length ());

	sem_item *source = c->members[0];

	for (unsigned int j = 1; j < c->members.length (); j++)
	  {
	    sem_item *alias = c->members[j];

	    if (dump_file)
	      {
		fprintf (dump_file, "Semantic equality hit:%s->%s\n",
			 source->name (), alias->name ());
		fprintf (dump_file, "Assembler symbol names:%s->%s\n",
			 source->asm_name (), alias->asm_name ());
	      }

	    if (lookup_attribute ("no_icf", DECL_ATTRIBUTES (alias->decl)))
	      {
	        if (dump_file)
		  fprintf (dump_file,
			   "Merge operation is skipped due to no_icf "
			   "attribute.\n\n");

		continue;
	      }

	    if (dump_file && (dump_flags & TDF_DETAILS))
	      {
		source->dump_to_file (dump_file);
		alias->dump_to_file (dump_file);
	      }

	    source->merge (alias);
	  }
      }
}

/* Dump function prints all class members to a FILE with an INDENT.  */

void
congruence_class::dump (FILE *file, unsigned int indent) const
{
  FPRINTF_SPACES (file, indent, "class with id: %u, hash: %u, items: %u\n",
		  id, members[0]->get_hash (), members.length ());

  FPUTS_SPACES (file, indent + 2, "");
  for (unsigned i = 0; i < members.length (); i++)
    fprintf (file, "%s(%p/%u) ", members[i]->asm_name (), (void *) members[i]->decl,
	     members[i]->node->order);

  fprintf (file, "\n");
}

/* Returns true if there's a member that is used from another group.  */

bool
congruence_class::is_class_used (void)
{
  for (unsigned int i = 0; i < members.length (); i++)
    if (members[i]->usages.length ())
      return true;

  return false;
}

/* Initialization and computation of symtab node hash, there data
   are propagated later on.  */

static sem_item_optimizer *optimizer = NULL;

/* Generate pass summary for IPA ICF pass.  */

static void
ipa_icf_generate_summary (void)
{
  if (!optimizer)
    optimizer = new sem_item_optimizer ();

  optimizer->register_hooks ();
  optimizer->parse_funcs_and_vars ();
}

/* Write pass summary for IPA ICF pass.  */

static void
ipa_icf_write_summary (void)
{
  gcc_assert (optimizer);

  optimizer->write_summary ();
}

/* Read pass summary for IPA ICF pass.  */

static void
ipa_icf_read_summary (void)
{
  if (!optimizer)
    optimizer = new sem_item_optimizer ();

  optimizer->read_summary ();
  optimizer->register_hooks ();
}

/* Semantic equality exection function.  */

static unsigned int
ipa_icf_driver (void)
{
  gcc_assert (optimizer);

  optimizer->execute ();

  delete optimizer;
  optimizer = NULL;

  return 0;
}

const pass_data pass_data_ipa_icf =
{
  IPA_PASS,		    /* type */
  "icf",		    /* name */
  OPTGROUP_IPA,             /* optinfo_flags */
  TV_IPA_ICF,		    /* tv_id */
  0,                        /* properties_required */
  0,                        /* properties_provided */
  0,                        /* properties_destroyed */
  0,                        /* todo_flags_start */
  0,                        /* todo_flags_finish */
};

class pass_ipa_icf : public ipa_opt_pass_d
{
public:
  pass_ipa_icf (gcc::context *ctxt)
    : ipa_opt_pass_d (pass_data_ipa_icf, ctxt,
		      ipa_icf_generate_summary, /* generate_summary */
		      ipa_icf_write_summary, /* write_summary */
		      ipa_icf_read_summary, /* read_summary */
		      NULL, /*
		      write_optimization_summary */
		      NULL, /*
		      read_optimization_summary */
		      NULL, /* stmt_fixup */
		      0, /* function_transform_todo_flags_start */
		      NULL, /* function_transform */
		      NULL) /* variable_transform */
  {}

  /* opt_pass methods: */
  virtual bool gate (function *)
  {
    return in_lto_p || flag_ipa_icf_variables || flag_ipa_icf_functions;
  }

  virtual unsigned int execute (function *)
  {
    return ipa_icf_driver();
  }
}; // class pass_ipa_icf

} // ipa_icf namespace

ipa_opt_pass_d *
make_pass_ipa_icf (gcc::context *ctxt)
{
  return new ipa_icf::pass_ipa_icf (ctxt);
}