[pf3gnuchains/gcc-fork.git] / gcc / lto / lto.c

/* Top-level LTO routines.
   Copyright 2009 Free Software Foundation, Inc.
   Contributed by CodeSourcery, 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 "opts.h"
#include "toplev.h"
#include "tree.h"
#include "diagnostic.h"
#include "tm.h"
#include "libiberty.h"
#include "cgraph.h"
#include "ggc.h"
#include "tree-ssa-operands.h"
#include "tree-pass.h"
#include "langhooks.h"
#include "vec.h"
#include "bitmap.h"
#include "pointer-set.h"
#include "ipa-prop.h"
#include "common.h"
#include "timevar.h"
#include "gimple.h"
#include "lto.h"
#include "lto-tree.h"
#include "lto-streamer.h"

/* This needs to be included after config.h.  Otherwise, _GNU_SOURCE will not
   be defined in time to set __USE_GNU in the system headers, and strsignal
   will not be declared.  */
#include <sys/mman.h>

DEF_VEC_P(bitmap);
DEF_VEC_ALLOC_P(bitmap,heap);

/* Read the constructors and inits.  */

static void
lto_materialize_constructors_and_inits (struct lto_file_decl_data * file_data)
{
  size_t len;
  const char *data = lto_get_section_data (file_data, 
                                           LTO_section_static_initializer,
                                           NULL, &len);
  lto_input_constructors_and_inits (file_data, data);
  lto_free_section_data (file_data, LTO_section_static_initializer, NULL,
                         data, len);
}

/* Read the function body for the function associated with NODE if possible.  */

static void
lto_materialize_function (struct cgraph_node *node)
{
  tree decl;
  struct lto_file_decl_data *file_data;
  const char *data, *name;
  size_t len;
  tree step;

  /* Ignore clone nodes.  Read the body only from the original one.
     We may find clone nodes during LTRANS after WPA has made inlining
     decisions.  */
  if (node->clone_of)
    return;

  decl = node->decl;
  file_data = node->local.lto_file_data;
  name = IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (decl)); 

  /* We may have renamed the declaration, e.g., a static function.  */
  name = lto_get_decl_name_mapping (file_data, name);

  data = lto_get_section_data (file_data, LTO_section_function_body,
                               name, &len);
  if (data)
    {
      struct function *fn;

      gcc_assert (!DECL_IS_BUILTIN (decl));

      /* This function has a definition.  */
      TREE_STATIC (decl) = 1;

      gcc_assert (DECL_STRUCT_FUNCTION (decl) == NULL);
      allocate_struct_function (decl, false);

      /* Load the function body only if not operating in WPA mode.  In
         WPA mode, the body of the function is not needed.  */
      if (!flag_wpa)
        {
          lto_input_function_body (file_data, decl, data);
          lto_stats.num_function_bodies++;
        }

      fn = DECL_STRUCT_FUNCTION (decl);
      lto_free_section_data (file_data, LTO_section_function_body, name,
                             data, len);

      /* Look for initializers of constant variables and private
         statics.  */
      for (step = fn->local_decls; step; step = TREE_CHAIN (step))
        {
          tree decl = TREE_VALUE (step);
          if (TREE_CODE (decl) == VAR_DECL
              && (TREE_STATIC (decl) && !DECL_EXTERNAL (decl))
              && flag_unit_at_a_time)
            varpool_finalize_decl (decl);
        }
    }
  else
    DECL_EXTERNAL (decl) = 1;

  /* Let the middle end know about the function.  */
  rest_of_decl_compilation (decl, 1, 0);
  if (cgraph_node (decl)->needed)
    cgraph_mark_reachable_node (cgraph_node (decl));
}


/* Decode the content of memory pointed to by DATA in the the
   in decl state object STATE. DATA_IN points to a data_in structure for
   decoding. Return the address after the decoded object in the input.  */

static const uint32_t *
lto_read_in_decl_state (struct data_in *data_in, const uint32_t *data,
                        struct lto_in_decl_state *state)
{
  uint32_t ix;
  tree decl;
  uint32_t i, j;
  
  ix = *data++;
  decl = lto_streamer_cache_get (data_in->reader_cache, (int) ix);
  if (TREE_CODE (decl) != FUNCTION_DECL)
    {
      gcc_assert (decl == void_type_node);
      decl = NULL_TREE;
    }
  state->fn_decl = decl;

  for (i = 0; i < LTO_N_DECL_STREAMS; i++)
    {
      uint32_t size = *data++;
      tree *decls = (tree *) xcalloc (size, sizeof (tree));

      for (j = 0; j < size; j++)
        {
          decls[j] = lto_streamer_cache_get (data_in->reader_cache, data[j]);

          /* Register every type in the global type table.  If the
             type existed already, use the existing type.  */
          if (TYPE_P (decls[j]))
            decls[j] = gimple_register_type (decls[j]);
        }

      state->streams[i].size = size;
      state->streams[i].trees = decls;
      data += size;
    }

  return data;
}


/* Read all the symbols from buffer DATA, using descriptors in DECL_DATA.
   RESOLUTIONS is the set of symbols picked by the linker (read from the
   resolution file when the linker plugin is being used).  */

static void
lto_read_decls (struct lto_file_decl_data *decl_data, const void *data,
                VEC(ld_plugin_symbol_resolution_t,heap) *resolutions)
{
  const struct lto_decl_header *header = (const struct lto_decl_header *) data;
  const int32_t decl_offset = sizeof (struct lto_decl_header);
  const int32_t main_offset = decl_offset + header->decl_state_size;
  const int32_t string_offset = main_offset + header->main_size;
  struct lto_input_block ib_main;
  struct data_in *data_in;
  unsigned int i;
  const uint32_t *data_ptr, *data_end;
  uint32_t num_decl_states;

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

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

  /* Read the global declarations and types.  */
  while (ib_main.p < ib_main.len)
    {
      tree t = lto_input_tree (&ib_main, data_in);
      gcc_assert (t && ib_main.p <= ib_main.len);
    }

  /* Read in lto_in_decl_state objects.  */
  data_ptr = (const uint32_t *) ((const char*) data + decl_offset); 
  data_end =
     (const uint32_t *) ((const char*) data_ptr + header->decl_state_size);
  num_decl_states = *data_ptr++;
  
  gcc_assert (num_decl_states > 0);
  decl_data->global_decl_state = lto_new_in_decl_state ();
  data_ptr = lto_read_in_decl_state (data_in, data_ptr,
                                     decl_data->global_decl_state);

  /* Read in per-function decl states and enter them in hash table.  */
  decl_data->function_decl_states =
    htab_create (37, lto_hash_in_decl_state, lto_eq_in_decl_state, free);

  for (i = 1; i < num_decl_states; i++)
    {
      struct lto_in_decl_state *state = lto_new_in_decl_state ();
      void **slot;

      data_ptr = lto_read_in_decl_state (data_in, data_ptr, state);
      slot = htab_find_slot (decl_data->function_decl_states, state, INSERT);
      gcc_assert (*slot == NULL);
      *slot = state;
    }

  if (data_ptr != data_end)
    internal_error ("bytecode stream: garbage at the end of symbols section");
  
  /* Set the current decl state to be the global state. */
  decl_data->current_decl_state = decl_data->global_decl_state;

  /* After each CU is read register and possibly merge global
     symbols and their types.  */
  lto_register_deferred_decls_in_symtab (data_in);

  lto_data_in_delete (data_in);
}

/* Read resolution for file named FILE_NAME. The resolution is read from
   RESOLUTION. An array with the symbol resolution is returned. The array
   size is written to SIZE. */

static VEC(ld_plugin_symbol_resolution_t,heap) *
lto_resolution_read (FILE *resolution, const char *file_name)
{
  /* We require that objects in the resolution file are in the same
     order as the lto1 command line. */
  unsigned int name_len;
  char *obj_name;
  unsigned int num_symbols;
  unsigned int i;
  VEC(ld_plugin_symbol_resolution_t,heap) *ret = NULL;
  unsigned max_index = 0;

  if (!resolution)
    return NULL;

  name_len = strlen (file_name);
  obj_name = XNEWVEC (char, name_len + 1);
  fscanf (resolution, " ");   /* Read white space. */

  fread (obj_name, sizeof (char), name_len, resolution);
  obj_name[name_len] = '\0';
  if (strcmp (obj_name, file_name) != 0)
    internal_error ("unexpected file name %s in linker resolution file. "
                    "Expected %s", obj_name, file_name);

  free (obj_name);

  fscanf (resolution, "%u", &num_symbols);

  for (i = 0; i < num_symbols; i++)
    {
      unsigned index;
      char r_str[27];
      enum ld_plugin_symbol_resolution r;
      unsigned int j;
      unsigned int lto_resolution_str_len =
        sizeof (lto_resolution_str) / sizeof (char *);

      fscanf (resolution, "%u %26s", &index, r_str);
      if (index > max_index)
        max_index = index;

      for (j = 0; j < lto_resolution_str_len; j++)
        {
          if (strcmp (lto_resolution_str[j], r_str) == 0)
            {
              r = (enum ld_plugin_symbol_resolution) j;
              break;
            }
        }
      if (j >= lto_resolution_str_len)
        internal_error ("tried to read past the end of the linker resolution "
                        "file");

      VEC_safe_grow_cleared (ld_plugin_symbol_resolution_t, heap, ret,
                             index + 1);
      VEC_replace (ld_plugin_symbol_resolution_t, ret, index, r);
    }

  return ret;
}

/* Generate a TREE representation for all types and external decls
   entities in FILE.  

   Read all of the globals out of the file.  Then read the cgraph
   and process the .o index into the cgraph nodes so that it can open
   the .o file to load the functions and ipa information.   */

static struct lto_file_decl_data *
lto_file_read (lto_file *file, FILE *resolution_file)
{
  struct lto_file_decl_data *file_data;
  const char *data;
  size_t len;
  VEC(ld_plugin_symbol_resolution_t,heap) *resolutions;
  
  resolutions = lto_resolution_read (resolution_file, file->filename);

  file_data = XCNEW (struct lto_file_decl_data);
  file_data->file_name = file->filename;
  file_data->fd = -1;
  file_data->section_hash_table = lto_elf_build_section_table (file);
  file_data->renaming_hash_table = lto_create_renaming_table ();

  data = lto_get_section_data (file_data, LTO_section_decls, NULL, &len);
  lto_read_decls (file_data, data, resolutions);
  lto_free_section_data (file_data, LTO_section_decls, NULL, data, len);

  return file_data;
}

#if HAVE_MMAP_FILE && HAVE_SYSCONF && defined _SC_PAGE_SIZE
#define LTO_MMAP_IO 1
#endif

#if LTO_MMAP_IO
/* Page size of machine is used for mmap and munmap calls.  */
static size_t page_mask;
#endif

/* Get the section data of length LEN from FILENAME starting at
   OFFSET.  The data segment must be freed by the caller when the
   caller is finished.  Returns NULL if all was not well.  */

static char *
lto_read_section_data (struct lto_file_decl_data *file_data,
                       intptr_t offset, size_t len)
{
  char *result;
#if LTO_MMAP_IO
  intptr_t computed_len;
  intptr_t computed_offset;
  intptr_t diff;
#endif

  if (file_data->fd == -1)
    file_data->fd = open (file_data->file_name, O_RDONLY);

  if (file_data->fd == -1)
    return NULL;

#if LTO_MMAP_IO
  if (!page_mask)
    {
      size_t page_size = sysconf (_SC_PAGE_SIZE);
      page_mask = ~(page_size - 1);
    }

  computed_offset = offset & page_mask;
  diff = offset - computed_offset;
  computed_len = len + diff;

  result = (char *) mmap (NULL, computed_len, PROT_READ, MAP_PRIVATE,
                          file_data->fd, computed_offset);
  if (result == MAP_FAILED)
    {
      close (file_data->fd);
      return NULL;
    }

  return result + diff;
#else
  result = (char *) xmalloc (len);
  if (result == NULL)
    {
      close (file_data->fd);
      return NULL;
    }
  if (lseek (file_data->fd, offset, SEEK_SET) != offset
      || read (file_data->fd, result, len) != (ssize_t) len)
    {
      free (result);
      close (file_data->fd);
      return NULL;
    }

  return result;
#endif
}    


/* Get the section data from FILE_DATA of SECTION_TYPE with NAME.
   NAME will be NULL unless the section type is for a function
   body.  */

static const char *
get_section_data (struct lto_file_decl_data *file_data,
                      enum lto_section_type section_type,
                      const char *name,
                      size_t *len)
{
  htab_t section_hash_table = file_data->section_hash_table;
  struct lto_section_slot *f_slot;
  struct lto_section_slot s_slot;
  const char *section_name = lto_get_section_name (section_type, name);
  char *data = NULL;

  *len = 0;
  s_slot.name = section_name;
  f_slot = (struct lto_section_slot *) htab_find (section_hash_table, &s_slot);
  if (f_slot)
    {
      data = lto_read_section_data (file_data, f_slot->start, f_slot->len);
      *len = f_slot->len;
    }

  free (CONST_CAST (char *, section_name));
  return data;
}


/* Free the section data from FILE_DATA of SECTION_TYPE with NAME that
   starts at OFFSET and has LEN bytes.  */

static void
free_section_data (struct lto_file_decl_data *file_data,
                   enum lto_section_type section_type ATTRIBUTE_UNUSED,
                   const char *name ATTRIBUTE_UNUSED,
                   const char *offset, size_t len ATTRIBUTE_UNUSED)
{
#if LTO_MMAP_IO
  intptr_t computed_len;
  intptr_t computed_offset;
  intptr_t diff;
#endif

  if (file_data->fd == -1)
    return;

#if LTO_MMAP_IO
  computed_offset = ((intptr_t) offset) & page_mask;
  diff = (intptr_t) offset - computed_offset;
  computed_len = len + diff;

  munmap ((caddr_t) computed_offset, computed_len);
#else
  free (CONST_CAST(char *, offset));
#endif
}

/* Vector of all cgraph node sets. */
static GTY (()) VEC(cgraph_node_set, gc) *lto_cgraph_node_sets;


/* Group cgrah nodes by input files.  This is used mainly for testing
   right now.  */

static void
lto_1_to_1_map (void)
{
  struct cgraph_node *node;
  struct lto_file_decl_data *file_data;
  struct pointer_map_t *pmap;
  cgraph_node_set set;
  void **slot;

  timevar_push (TV_WHOPR_WPA);

  lto_cgraph_node_sets = VEC_alloc (cgraph_node_set, gc, 1);

  /* If the cgraph is empty, create one cgraph node set so that there is still
     an output file for any variables that need to be exported in a DSO.  */
  if (!cgraph_nodes)
    {
      set = cgraph_node_set_new ();
      VEC_safe_push (cgraph_node_set, gc, lto_cgraph_node_sets, set);
      goto finish;
    }

  pmap = pointer_map_create ();

  for (node = cgraph_nodes; node; node = node->next)
    {
      /* We only need to partition the nodes that we read from the
         gimple bytecode files.  */
      file_data = node->local.lto_file_data;
      if (file_data == NULL)
        continue;

      slot = pointer_map_contains (pmap, file_data);
      if (slot)
        set = (cgraph_node_set) *slot;
      else
        {
          set = cgraph_node_set_new ();
          slot = pointer_map_insert (pmap, file_data);
          *slot = set;
          VEC_safe_push (cgraph_node_set, gc, lto_cgraph_node_sets, set);
        }

      cgraph_node_set_add (set, node);
    }

  pointer_map_destroy (pmap);

finish:
  timevar_pop (TV_WHOPR_WPA);

  lto_stats.num_cgraph_partitions += VEC_length (cgraph_node_set, 
                                                 lto_cgraph_node_sets);
}


/* Add inlined clone NODE and its master clone to SET, if NODE itself has
   inlined callees, recursively add the callees.  */

static void
lto_add_inline_clones (cgraph_node_set set, struct cgraph_node *node,
                       bitmap original_decls, bitmap inlined_decls)
{
   struct cgraph_node *callee;
   struct cgraph_edge *edge;

   cgraph_node_set_add (set, node);

   if (!bitmap_bit_p (original_decls, DECL_UID (node->decl)))
     bitmap_set_bit (inlined_decls, DECL_UID (node->decl));

   /* Check to see if NODE has any inlined callee.  */
   for (edge = node->callees; edge != NULL; edge = edge->next_callee)
     {
        callee = edge->callee;
        if (callee->global.inlined_to != NULL)
          lto_add_inline_clones (set, callee, original_decls, inlined_decls);
     }
}

/* Compute the transitive closure of inlining of SET based on the
   information in the callgraph.  Returns a bitmap of decls that have
   been inlined into SET indexed by UID.  */

static bitmap
lto_add_all_inlinees (cgraph_node_set set)
{
  cgraph_node_set_iterator csi;
  struct cgraph_node *node;
  bitmap original_nodes = lto_bitmap_alloc ();
  bitmap original_decls = lto_bitmap_alloc ();
  bitmap inlined_decls = lto_bitmap_alloc ();
  bool changed;

  /* We are going to iterate SET while adding to it, mark all original
     nodes so that we only add node inlined to original nodes.  */
  for (csi = csi_start (set); !csi_end_p (csi); csi_next (&csi))
    {
      bitmap_set_bit (original_nodes, csi_node (csi)->uid);
      bitmap_set_bit (original_decls, DECL_UID (csi_node (csi)->decl));
    }

  /* Some of the original nodes might not be needed anymore.  
     Remove them.  */
  do
    {
      changed = false;
      for (csi = csi_start (set); !csi_end_p (csi); csi_next (&csi))
        {
          struct cgraph_node *inlined_to;
          node = csi_node (csi);

          /* NODE was not inlined.  We still need it.  */
          if (!node->global.inlined_to)
            continue;

          inlined_to = node->global.inlined_to;

          /* NODE should have only one caller.  */
          gcc_assert (!node->callers->next_caller);

          if (!bitmap_bit_p (original_nodes, inlined_to->uid))
            {
              bitmap_clear_bit (original_nodes, node->uid);
              cgraph_node_set_remove (set, node);
              changed = true;
            }
        }
    }
  while (changed);

  /* Transitively add to SET all the inline clones for every node that
     has been inlined.  */
  for (csi = csi_start (set); !csi_end_p (csi); csi_next (&csi))
    {
      node = csi_node (csi);
      if (bitmap_bit_p (original_nodes, node->uid))
        lto_add_inline_clones (set, node, original_decls, inlined_decls);
    }

  lto_bitmap_free (original_nodes);
  lto_bitmap_free (original_decls);

  return inlined_decls;
}

/* Owing to inlining, we may need to promote a file-scope variable
   to a global variable.  Consider this case:

   a.c:
   static int var;

   void
   foo (void)
   {
     var++;
   }

   b.c:

   extern void foo (void);

   void
   bar (void)
   {
     foo ();
   }

   If WPA inlines FOO inside BAR, then the static variable VAR needs to
   be promoted to global because BAR and VAR may be in different LTRANS
   files. */

/* This struct keeps track of states used in globalization.  */

typedef struct
{
  /* Current cgraph node set.  */  
  cgraph_node_set set;

  /* Function DECLs of cgraph nodes seen.  */
  bitmap seen_node_decls;

  /* Use in walk_tree to avoid multiple visits of a node.  */
  struct pointer_set_t *visited;

  /* static vars in this set.  */
  bitmap static_vars_in_set;

  /* static vars in all previous set.  */
  bitmap all_static_vars;

  /* all vars in all previous set.  */
  bitmap all_vars;
} globalize_context_t;

/* Callback for walk_tree.  Examine the tree pointer to by TP and see if
   if its a file-scope static variable of function that need to be turned
   into a global.  */

static tree
globalize_cross_file_statics (tree *tp, int *walk_subtrees ATTRIBUTE_UNUSED,
                              void *data)
{
  globalize_context_t *context = (globalize_context_t *) data;
  tree t = *tp;

  if (t == NULL_TREE)
    return NULL;

  /* The logic for globalization of VAR_DECLs and FUNCTION_DECLs are
     different.  For functions, we can simply look at the cgraph node sets
     to tell if there are references to static functions outside the set.
     The cgraph node sets do not keep track of vars, we need to traverse
     the trees to determine what vars need to be globalized.  */
  if (TREE_CODE (t) == VAR_DECL)
    {
      if (!TREE_PUBLIC (t))
        {
          /* This file-scope static variable is reachable from more
             that one set.  Make it global but with hidden visibility
             so that we do not export it in dynamic linking.  */
          if (bitmap_bit_p (context->all_static_vars, DECL_UID (t)))
            {
              TREE_PUBLIC (t) = 1;
              DECL_VISIBILITY (t) = VISIBILITY_HIDDEN;
            }
          bitmap_set_bit (context->static_vars_in_set, DECL_UID (t));
        }
      bitmap_set_bit (context->all_vars, DECL_UID (t));
      walk_tree (&DECL_INITIAL (t), globalize_cross_file_statics, context,
                 context->visited);
    }
  else if (TREE_CODE (t) == FUNCTION_DECL && !TREE_PUBLIC (t))
    {
      if (!cgraph_node_in_set_p (cgraph_node (t), context->set))
        {
          /* This file-scope static function is reachable from a set
             which does not contain the function DECL.  Make it global
             but with hidden visibility.  */
          TREE_PUBLIC (t) = 1;
          DECL_VISIBILITY (t) = VISIBILITY_HIDDEN;
        }
    }

  return NULL; 
}

/* Helper of lto_scan_statics_in_cgraph_node below.  Scan TABLE for
   static decls that may be used in more than one LTRANS file.
   CONTEXT is a globalize_context_t for storing scanning states.  */

static void
lto_scan_statics_in_ref_table (struct lto_tree_ref_table *table,
                               globalize_context_t *context)
{
  unsigned i;

  for (i = 0; i < table->size; i++)
    walk_tree (&table->trees[i], globalize_cross_file_statics, context,
               context->visited);
}

/* Promote file-scope decl reachable from NODE if necessary to global.
   CONTEXT is a globalize_context_t storing scanning states.  */

static void
lto_scan_statics_in_cgraph_node (struct cgraph_node *node,
                                 globalize_context_t *context)
{
  struct lto_in_decl_state *state;
  
  /* Do nothing if NODE has no function body.  */
  if (!node->analyzed)
    return;
  
  /* Return if the DECL of nodes has been visited before.  */
  if (bitmap_bit_p (context->seen_node_decls, DECL_UID (node->decl)))
    return;

  bitmap_set_bit (context->seen_node_decls, DECL_UID (node->decl));

  state = lto_get_function_in_decl_state (node->local.lto_file_data,
                                          node->decl);
  gcc_assert (state);

  lto_scan_statics_in_ref_table (&state->streams[LTO_DECL_STREAM_VAR_DECL],
                                 context);
  lto_scan_statics_in_ref_table (&state->streams[LTO_DECL_STREAM_FN_DECL],
                                 context);
}

/* Scan all global variables that we have not yet seen so far.  CONTEXT
   is a globalize_context_t storing scanning states.  */

static void
lto_scan_statics_in_remaining_global_vars (globalize_context_t *context)
{
  tree var, var_context;
  struct varpool_node *vnode;

  FOR_EACH_STATIC_VARIABLE (vnode)
    {
      var = vnode->decl;
      var_context = DECL_CONTEXT (var);
      if (TREE_STATIC (var)
          && TREE_PUBLIC (var)
          && (!var_context || TREE_CODE (var_context) != FUNCTION_DECL)
          && !bitmap_bit_p (context->all_vars, DECL_UID (var)))
        walk_tree (&var, globalize_cross_file_statics, context,
                   context->visited);
    }
}

/* Find out all static decls that need to be promoted to global because
   of cross file sharing.  This function must be run in the WPA mode after
   all inlinees are added.  */

static void
lto_promote_cross_file_statics (void)
{
  unsigned i, n_sets;
  cgraph_node_set set;
  cgraph_node_set_iterator csi;
  globalize_context_t context;

  memset (&context, 0, sizeof (context));
  context.all_vars = lto_bitmap_alloc ();
  context.all_static_vars = lto_bitmap_alloc ();

  n_sets = VEC_length (cgraph_node_set, lto_cgraph_node_sets);
  for (i = 0; i < n_sets; i++)
    {
      set = VEC_index (cgraph_node_set, lto_cgraph_node_sets, i);
      context.set = set;
      context.visited = pointer_set_create ();
      context.static_vars_in_set = lto_bitmap_alloc ();
      context.seen_node_decls = lto_bitmap_alloc ();

      for (csi = csi_start (set); !csi_end_p (csi); csi_next (&csi))
        lto_scan_statics_in_cgraph_node (csi_node (csi), &context);

      if (i == n_sets - 1)
        lto_scan_statics_in_remaining_global_vars (&context);

      bitmap_ior_into (context.all_static_vars, context.static_vars_in_set);

      pointer_set_destroy (context.visited);
      lto_bitmap_free (context.static_vars_in_set);
      lto_bitmap_free (context.seen_node_decls);
    }

  lto_bitmap_free (context.all_vars);
  lto_bitmap_free (context.all_static_vars);
}


/* Given a file name FNAME, return a string with FNAME prefixed with '*'.  */

static char *
prefix_name_with_star (const char *fname)
{
  char *star_fname;
  size_t len;
  
  len = strlen (fname) + 1 + 1;
  star_fname = XNEWVEC (char, len);
  snprintf (star_fname, len, "*%s", fname);

  return star_fname;
}


/* Return a copy of FNAME without the .o extension.  */

static char *
strip_extension (const char *fname)
{
  char *s = XNEWVEC (char, strlen (fname) - 2 + 1);
  gcc_assert (strstr (fname, ".o"));
  snprintf (s, strlen (fname) - 2 + 1, "%s", fname);

  return s;
}


/* Return a file name associated with cgraph node set SET.  This may
   be a new temporary file name if SET needs to be processed by
   LTRANS, or the original file name if all the nodes in SET belong to
   the same input file.  */

static char *
get_filename_for_set (cgraph_node_set set)
{
  char *fname = NULL;
  static const size_t max_fname_len = 100;

  if (cgraph_node_set_needs_ltrans_p (set))
    {
      /* Create a new temporary file to store SET.  To facilitate
         debugging, use file names from SET as part of the new
         temporary file name.  */
      cgraph_node_set_iterator si;
      struct pointer_set_t *pset = pointer_set_create ();
      for (si = csi_start (set); !csi_end_p (si); csi_next (&si))
        {
          struct cgraph_node *n = csi_node (si);
          const char *node_fname;
          char *f;

          /* Don't use the same file name more than once.  */
          if (pointer_set_insert (pset, n->local.lto_file_data))
            continue;

          /* The first file name found in SET determines the output
             directory.  For the remaining files, we use their
             base names.  */
          node_fname = n->local.lto_file_data->file_name;
          if (fname == NULL)
            {
              fname = strip_extension (node_fname);
              continue;
            }

          f = strip_extension (lbasename (node_fname));

          /* If the new name causes an excessively long file name,
             make the last component "___" to indicate overflow.  */
          if (strlen (fname) + strlen (f) > max_fname_len - 3)
            {
              fname = reconcat (fname, fname, "___", NULL);
              break;
            }
          else
            {
              fname = reconcat (fname, fname, "_", f, NULL);
              free (f);
            }
        }

      pointer_set_destroy (pset);

      /* Add the extension .wpa.o to indicate that this file has been
         produced by WPA.  */
      fname = reconcat (fname, fname, ".wpa.o", NULL);
      gcc_assert (fname);
    }
  else
    {
      /* Since SET does not need to be processed by LTRANS, use
         the original file name and mark it with a '*' prefix so that
         lto_execute_ltrans knows not to process it.  */
      cgraph_node_set_iterator si = csi_start (set);
      struct cgraph_node *first = csi_node (si);
      fname = prefix_name_with_star (first->local.lto_file_data->file_name);
    }

  return fname;
}

static lto_file *current_lto_file;


/* Write all output files in WPA mode.  Returns a NULL-terminated array of
   output file names.  */

static char **
lto_wpa_write_files (void)
{
  char **output_files;
  unsigned i, n_sets, last_out_file_ix, num_out_files;
  lto_file *file;
  cgraph_node_set set;
  bitmap decls;
  VEC(bitmap,heap) *inlined_decls = NULL;

  timevar_push (TV_WHOPR_WPA);

  /* Include all inlined functions and determine what sets need to be
     compiled by LTRANS.  After this loop, only those sets that
     contain callgraph nodes from more than one file will need to be
     compiled by LTRANS.  */
  for (i = 0; VEC_iterate (cgraph_node_set, lto_cgraph_node_sets, i, set); i++)
    {
      decls = lto_add_all_inlinees (set);
      VEC_safe_push (bitmap, heap, inlined_decls, decls);
      lto_stats.num_output_cgraph_nodes += VEC_length (cgraph_node_ptr,
                                                       set->nodes);
    }

  /* After adding all inlinees, find out statics that need to be promoted
     to globals because of cross-file inlining.  */
  lto_promote_cross_file_statics ();

  timevar_pop (TV_WHOPR_WPA);

  timevar_push (TV_WHOPR_WPA_IO);

  /* The number of output files depends on the number of input files
     and how many callgraph node sets we create.  Reserve enough space
     for the maximum of these two.  */
  num_out_files = MAX (VEC_length (cgraph_node_set, lto_cgraph_node_sets),
                       num_in_fnames);
  output_files = XNEWVEC (char *, num_out_files + 1);

  n_sets = VEC_length (cgraph_node_set, lto_cgraph_node_sets);
  for (i = 0; i < n_sets; i++)
    {
      char *temp_filename;

      set = VEC_index (cgraph_node_set, lto_cgraph_node_sets, i);
      temp_filename = get_filename_for_set (set);
      output_files[i] = temp_filename;

      if (cgraph_node_set_needs_ltrans_p (set))
        {
          /* Write all the nodes in SET to TEMP_FILENAME.  */
          file = lto_elf_file_open (temp_filename, true);
          if (!file)
            fatal_error ("lto_elf_file_open() failed");

          lto_set_current_out_file (file);
          lto_new_extern_inline_states ();

          decls = VEC_index (bitmap, inlined_decls, i);
          lto_force_functions_extern_inline (decls);

          ipa_write_summaries_of_cgraph_node_set (set);
          lto_delete_extern_inline_states ();

          lto_set_current_out_file (NULL);
          lto_elf_file_close (file);
        }
    }

  last_out_file_ix = n_sets;

  lto_stats.num_output_files += n_sets;

  output_files[last_out_file_ix] = NULL;

  for (i = 0; VEC_iterate (bitmap, inlined_decls, i, decls); i++)
    lto_bitmap_free (decls);
  VEC_free (bitmap, heap, inlined_decls);

  timevar_pop (TV_WHOPR_WPA_IO);

  return output_files;
}


/* Perform local transformations (LTRANS) on the files in the NULL-terminated
   FILES array.  These should have been written previously by
   lto_wpa_write_files ().  Transformations are performed via executing
   COLLECT_GCC for reach file.  */

static void
lto_execute_ltrans (char *const *files)
{
  struct pex_obj *pex;
  const char *collect_gcc_options, *collect_gcc;
  struct obstack env_obstack;
  const char **argv;
  const char **argv_ptr;
  const char *errmsg;
  size_t i, j;
  int err;
  int status;
  FILE *ltrans_output_list_stream = NULL;

  timevar_push (TV_WHOPR_WPA_LTRANS_EXEC);

  /* Get the driver and options.  */
  collect_gcc = getenv ("COLLECT_GCC");
  if (!collect_gcc)
    fatal_error ("environment variable COLLECT_GCC must be set");

  /* Set the CFLAGS environment variable.  */
  collect_gcc_options = getenv ("COLLECT_GCC_OPTIONS");
  if (!collect_gcc_options)
    fatal_error ("environment variable COLLECT_GCC_OPTIONS must be set");

  /* Count arguments.  */
  i = 0;
  for (j = 0; collect_gcc_options[j] != '\0'; ++j)
    if (collect_gcc_options[j] == '\'')
      ++i;

  if (i % 2 != 0)
    fatal_error ("malformed COLLECT_GCC_OPTIONS");

  /* Initalize the arguments for the LTRANS driver.  */
  argv = XNEWVEC (const char *, 8 + i / 2);
  argv_ptr = argv;
  *argv_ptr++ = collect_gcc;
  *argv_ptr++ = "-xlto";
  for (j = 0; collect_gcc_options[j] != '\0'; ++j)
    if (collect_gcc_options[j] == '\'')
      {
        char *option;

        ++j;
        i = j;
        while (collect_gcc_options[j] != '\'')
          ++j;
        obstack_init (&env_obstack);
        obstack_grow (&env_obstack, &collect_gcc_options[i], j - i);
        obstack_1grow (&env_obstack, 0);
        option = XOBFINISH (&env_obstack, char *);

        /* LTRANS does not need -fwpa nor -fltrans-*.  */
        if (strncmp (option, "-fwpa", 5) != 0
            && strncmp (option, "-fltrans-", 9) != 0)
          *argv_ptr++ = option;
      }
  *argv_ptr++ = "-fltrans";

  /* Open the LTRANS output list.  */
  if (ltrans_output_list)
    {
      ltrans_output_list_stream = fopen (ltrans_output_list, "w");
      if (ltrans_output_list_stream == NULL)
        error ("opening LTRANS output list %s: %m", ltrans_output_list);
    }

  for (i = 0; files[i]; ++i)
    {
      size_t len;

      /* If the file is prefixed with a '*', it means that we do not
         need to re-compile it with LTRANS because it has not been
         modified by WPA.  Skip it from the command line to
         lto_execute_ltrans, but add it to ltrans_output_list_stream
         so it is linked after we are done.  */
      if (files[i][0] == '*')
        {
          size_t len = strlen (files[i]) - 1;
          if (ltrans_output_list_stream)
            if (fwrite (&files[i][1], 1, len, ltrans_output_list_stream) < len
                || fwrite ("\n", 1, 1, ltrans_output_list_stream) < 1)
              error ("writing to LTRANS output list %s: %m",
                     ltrans_output_list);
        }
      else
        {
          char *output_name;

          /* Otherwise, add FILES[I] to lto_execute_ltrans command line
             and add the resulting file to LTRANS output list.  */

          /* Replace the .o suffix with a .ltrans.o suffix and write
             the resulting name to the LTRANS output list.  */
          obstack_init (&env_obstack);
          obstack_grow (&env_obstack, files[i], strlen (files[i]) - 2);
          obstack_grow (&env_obstack, ".ltrans.o", sizeof (".ltrans.o"));
          output_name = XOBFINISH (&env_obstack, char *);
          if (ltrans_output_list_stream)
            {
              len = strlen (output_name);

              if (fwrite (output_name, 1, len, ltrans_output_list_stream) < len
                  || fwrite ("\n", 1, 1, ltrans_output_list_stream) < 1)
                error ("writing to LTRANS output list %s: %m",
                       ltrans_output_list);
            }

          argv_ptr[0] = "-o";
          argv_ptr[1] = output_name;
          argv_ptr[2] = files[i];
          argv_ptr[3] = NULL;

          /* Execute the driver.  */
          pex = pex_init (0, "lto1", NULL);
          if (pex == NULL)
            fatal_error ("pex_init failed: %s", xstrerror (errno));

          errmsg = pex_run (pex, PEX_LAST | PEX_SEARCH, argv[0],
                            CONST_CAST (char **, argv), NULL, NULL, &err);
          if (errmsg)
            fatal_error ("%s: %s", errmsg, xstrerror (err));

          if (!pex_get_status (pex, 1, &status))
            fatal_error ("can't get program status: %s", xstrerror (errno));

          if (status)
            {
              if (WIFSIGNALED (status))
                {
                  int sig = WTERMSIG (status);
                  fatal_error ("%s terminated with signal %d [%s]%s",
                               argv[0], sig, strsignal (sig),
                               WCOREDUMP (status) ? ", core dumped" : "");
                }
              else
                fatal_error ("%s terminated with status %d", argv[0], status);
            }

          pex_free (pex);
        }
    }

  /* Close the LTRANS output list.  */
  if (ltrans_output_list_stream && fclose (ltrans_output_list_stream))
    error ("closing LTRANS output list %s: %m", ltrans_output_list);

  obstack_free (&env_obstack, NULL);
  free (argv);

  timevar_pop (TV_WHOPR_WPA_LTRANS_EXEC);
}


typedef struct {
  struct pointer_set_t *free_list;
  struct pointer_set_t *seen;
} lto_fixup_data_t;

#define LTO_FIXUP_SUBTREE(t) \
  do \
    walk_tree (&(t), lto_fixup_tree, data, NULL); \
  while (0)

#define LTO_REGISTER_TYPE_AND_FIXUP_SUBTREE(t) \
  do \
    { \
      if (t) \
        (t) = gimple_register_type (t); \
      walk_tree (&(t), lto_fixup_tree, data, NULL); \
    } \
  while (0)

static tree lto_fixup_tree (tree *, int *, void *);

/* Return true if T does not need to be fixed up recursively.  */

static inline bool
no_fixup_p (tree t)
{
  return (t == NULL
          || CONSTANT_CLASS_P (t)
          || TREE_CODE (t) == IDENTIFIER_NODE);
}

/* Fix up fields of a tree_common T.  DATA points to fix-up states.  */

static void
lto_fixup_common (tree t, void *data)
{
  /* The following re-creates the TYPE_REFERENCE_TO and TYPE_POINTER_TO
     lists.  We do not stream TYPE_REFERENCE_TO, TYPE_POINTER_TO or
     TYPE_NEXT_PTR_TO and TYPE_NEXT_REF_TO.
     First remove us from any pointer list we are on.  */
  if (TREE_CODE (t) == POINTER_TYPE)
    {
      if (TYPE_POINTER_TO (TREE_TYPE (t)) == t)
        TYPE_POINTER_TO (TREE_TYPE (t)) = TYPE_NEXT_PTR_TO (t);
      else
        {
          tree tem = TYPE_POINTER_TO (TREE_TYPE (t));
          while (tem && TYPE_NEXT_PTR_TO (tem) != t)
            tem = TYPE_NEXT_PTR_TO (tem);
          if (tem)
            TYPE_NEXT_PTR_TO (tem) = TYPE_NEXT_PTR_TO (t);
        }
      TYPE_NEXT_PTR_TO (t) = NULL_TREE;
    }
  else if (TREE_CODE (t) == REFERENCE_TYPE)
    {
      if (TYPE_REFERENCE_TO (TREE_TYPE (t)) == t)
        TYPE_REFERENCE_TO (TREE_TYPE (t)) = TYPE_NEXT_REF_TO (t);
      else
        {
          tree tem = TYPE_REFERENCE_TO (TREE_TYPE (t));
          while (tem && TYPE_NEXT_REF_TO (tem) != t)
            tem = TYPE_NEXT_REF_TO (tem);
          if (tem)
            TYPE_NEXT_REF_TO (tem) = TYPE_NEXT_REF_TO (t);
        }
      TYPE_NEXT_REF_TO (t) = NULL_TREE;
    }

  /* Fixup our type.  */
  LTO_REGISTER_TYPE_AND_FIXUP_SUBTREE (TREE_TYPE (t));

  /* Second put us on the list of pointers of the new pointed-to type
     if we are a main variant.  This is done in lto_fixup_type after
     fixing up our main variant.  */

  /* This is not very efficient because we cannot do tail-recursion with
     a long chain of trees. */
  LTO_FIXUP_SUBTREE (TREE_CHAIN (t));
}

/* Fix up fields of a decl_minimal T.  DATA points to fix-up states.  */

static void
lto_fixup_decl_minimal (tree t, void *data)
{
  lto_fixup_common (t, data);
  LTO_FIXUP_SUBTREE (DECL_NAME (t));
  LTO_FIXUP_SUBTREE (DECL_CONTEXT (t));
}

/* Fix up fields of a decl_common T.  DATA points to fix-up states.  */

static void
lto_fixup_decl_common (tree t, void *data)
{
  lto_fixup_decl_minimal (t, data);
  LTO_FIXUP_SUBTREE (DECL_SIZE (t));
  LTO_FIXUP_SUBTREE (DECL_SIZE_UNIT (t));
  LTO_FIXUP_SUBTREE (DECL_INITIAL (t));
  LTO_FIXUP_SUBTREE (DECL_ATTRIBUTES (t));
  LTO_FIXUP_SUBTREE (DECL_ABSTRACT_ORIGIN (t));
}

/* Fix up fields of a decl_with_vis T.  DATA points to fix-up states.  */

static void
lto_fixup_decl_with_vis (tree t, void *data)
{
  lto_fixup_decl_common (t, data);

  /* Accessor macro has side-effects, use field-name here. */
  LTO_FIXUP_SUBTREE (t->decl_with_vis.assembler_name);

  gcc_assert (no_fixup_p (DECL_SECTION_NAME (t)));
}

/* Fix up fields of a decl_non_common T.  DATA points to fix-up states.  */

static void
lto_fixup_decl_non_common (tree t, void *data)
{
  lto_fixup_decl_with_vis (t, data);
  LTO_FIXUP_SUBTREE (DECL_ARGUMENT_FLD (t));
  LTO_FIXUP_SUBTREE (DECL_RESULT_FLD (t));
  LTO_FIXUP_SUBTREE (DECL_VINDEX (t));

  /* SAVED_TREE should not cleared by now.  Also no accessor for base type. */
  gcc_assert (no_fixup_p (t->decl_non_common.saved_tree));
}

/* Fix up fields of a decl_non_common T.  DATA points to fix-up states.  */

static void
lto_fixup_function (tree t, void *data)
{
  lto_fixup_decl_non_common (t, data);
  LTO_FIXUP_SUBTREE (DECL_FUNCTION_PERSONALITY (t));
}

/* Fix up fields of a field_decl T.  DATA points to fix-up states.  */

static void
lto_fixup_field_decl (tree t, void *data)
{
  lto_fixup_decl_common (t, data);
  gcc_assert (no_fixup_p (DECL_FIELD_OFFSET (t)));
  LTO_FIXUP_SUBTREE (DECL_BIT_FIELD_TYPE (t));
  LTO_FIXUP_SUBTREE (DECL_QUALIFIER (t));
  gcc_assert (no_fixup_p (DECL_FIELD_BIT_OFFSET (t)));
  LTO_FIXUP_SUBTREE (DECL_FCONTEXT (t));
}

/* Fix up fields of a type T.  DATA points to fix-up states.  */

static void
lto_fixup_type (tree t, void *data)
{
  tree tem, mv;

  lto_fixup_common (t, data);
  LTO_FIXUP_SUBTREE (TYPE_CACHED_VALUES (t));
  LTO_FIXUP_SUBTREE (TYPE_SIZE (t));
  LTO_FIXUP_SUBTREE (TYPE_SIZE_UNIT (t));
  LTO_FIXUP_SUBTREE (TYPE_ATTRIBUTES (t));
  LTO_FIXUP_SUBTREE (TYPE_NAME (t));

  /* Accessors are for derived node types only. */
  if (!POINTER_TYPE_P (t))
    LTO_FIXUP_SUBTREE (t->type.minval);
  LTO_FIXUP_SUBTREE (t->type.maxval);

  /* Accessor is for derived node types only. */
  LTO_FIXUP_SUBTREE (t->type.binfo);

  LTO_REGISTER_TYPE_AND_FIXUP_SUBTREE (TYPE_CONTEXT (t));
  LTO_REGISTER_TYPE_AND_FIXUP_SUBTREE (TYPE_CANONICAL (t));

  /* The following re-creates proper variant lists while fixing up
     the variant leaders.  We do not stream TYPE_NEXT_VARIANT so the
     variant list state before fixup is broken.  */

  /* Remove us from our main variant list if we are not the variant leader.  */
  if (TYPE_MAIN_VARIANT (t) != t)
    {
      tem = TYPE_MAIN_VARIANT (t);
      while (tem && TYPE_NEXT_VARIANT (tem) != t)
        tem = TYPE_NEXT_VARIANT (tem);
      if (tem)
        TYPE_NEXT_VARIANT (tem) = TYPE_NEXT_VARIANT (t);
      TYPE_NEXT_VARIANT (t) = NULL_TREE;
    }

  /* Query our new main variant.  */
  mv = gimple_register_type (TYPE_MAIN_VARIANT (t));

  /* If we were the variant leader and we get replaced ourselves drop
     all variants from our list.  */
  if (TYPE_MAIN_VARIANT (t) == t
      && mv != t)
    {
      tem = t;
      while (tem)
        {
          tree tem2 = TYPE_NEXT_VARIANT (tem);
          TYPE_NEXT_VARIANT (tem) = NULL_TREE;
          tem = tem2;
        }
    }

  /* If we are not our own variant leader link us into our new leaders
     variant list.  */
  if (mv != t)
    {
      TYPE_NEXT_VARIANT (t) = TYPE_NEXT_VARIANT (mv);
      TYPE_NEXT_VARIANT (mv) = t;
    }

  /* Finally adjust our main variant and fix it up.  */
  TYPE_MAIN_VARIANT (t) = mv;
  LTO_FIXUP_SUBTREE (TYPE_MAIN_VARIANT (t));

  /* As the second step of reconstructing the pointer chains put us
     on the list of pointers of the new pointed-to type
     if we are a main variant.  See lto_fixup_common for the first step.  */
  if (TREE_CODE (t) == POINTER_TYPE
      && TYPE_MAIN_VARIANT (t) == t)
    {
      TYPE_NEXT_PTR_TO (t) = TYPE_POINTER_TO (TREE_TYPE (t));
      TYPE_POINTER_TO (TREE_TYPE (t)) = t;
    }
  else if (TREE_CODE (t) == REFERENCE_TYPE
           && TYPE_MAIN_VARIANT (t) == t)
    {
      TYPE_NEXT_REF_TO (t) = TYPE_REFERENCE_TO (TREE_TYPE (t));
      TYPE_REFERENCE_TO (TREE_TYPE (t)) = t;
    }
}

/* Fix up fields of a BINFO T.  DATA points to fix-up states.  */

static void
lto_fixup_binfo (tree t, void *data)
{
  unsigned HOST_WIDE_INT i, n;
  tree base, saved_base;

  lto_fixup_common (t, data);
  gcc_assert (no_fixup_p (BINFO_OFFSET (t)));
  LTO_FIXUP_SUBTREE (BINFO_VTABLE (t));
  LTO_FIXUP_SUBTREE (BINFO_VIRTUALS (t));
  LTO_FIXUP_SUBTREE (BINFO_VPTR_FIELD (t));
  n = VEC_length (tree, BINFO_BASE_ACCESSES (t));
  for (i = 0; i < n; i++)
    {
      saved_base = base = BINFO_BASE_ACCESS (t, i);
      LTO_FIXUP_SUBTREE (base);
      if (base != saved_base)
        VEC_replace (tree, BINFO_BASE_ACCESSES (t), i, base);
    }
  LTO_FIXUP_SUBTREE (BINFO_INHERITANCE_CHAIN (t));
  LTO_FIXUP_SUBTREE (BINFO_SUBVTT_INDEX (t));
  LTO_FIXUP_SUBTREE (BINFO_VPTR_INDEX (t));
  n = BINFO_N_BASE_BINFOS (t);
  for (i = 0; i < n; i++)
    {
      saved_base = base = BINFO_BASE_BINFO (t, i);
      LTO_FIXUP_SUBTREE (base);
      if (base != saved_base)
        VEC_replace (tree, BINFO_BASE_BINFOS (t), i, base);
    }
}

/* Fix up fields of a CONSTRUCTOR T.  DATA points to fix-up states.  */

static void
lto_fixup_constructor (tree t, void *data)
{
  unsigned HOST_WIDE_INT idx;
  constructor_elt *ce;

  LTO_REGISTER_TYPE_AND_FIXUP_SUBTREE (TREE_TYPE (t));

  for (idx = 0;
       VEC_iterate(constructor_elt, CONSTRUCTOR_ELTS (t), idx, ce);
       idx++)
    {
      LTO_FIXUP_SUBTREE (ce->index);
      LTO_FIXUP_SUBTREE (ce->value);
    }
}

/* A walk_tree callback used by lto_fixup_state. TP is the pointer to the
   current tree. WALK_SUBTREES indicates if the subtrees will be walked.
   DATA is a pointer set to record visited nodes. */

static tree
lto_fixup_tree (tree *tp, int *walk_subtrees, void *data)
{
  tree t;
  lto_fixup_data_t *fixup_data = (lto_fixup_data_t *) data;
  tree prevailing;

  t = *tp;
  *walk_subtrees = 0;
  if (pointer_set_contains (fixup_data->seen, t))
    return NULL;

  if (TREE_CODE (t) == VAR_DECL || TREE_CODE (t) == FUNCTION_DECL)
    {
      prevailing = lto_symtab_prevailing_decl (t);

      if (t != prevailing)
        {
          if (TREE_CODE (t) == FUNCTION_DECL
              && TREE_NOTHROW (prevailing) != TREE_NOTHROW (t))
            {
              /* If the prevailing definition does not throw but the
                 declaration (T) was considered throwing, then we
                 simply add PREVAILING to the list of throwing
                 functions.  However, if the opposite is true, then
                 the call to PREVAILING was generated assuming that
                 the function didn't throw, which means that CFG
                 cleanup may have removed surrounding try/catch
                 regions.

                 Note that we currently accept these cases even when
                 they occur within a single file.  It's certainly a
                 user error, but we silently allow the compiler to
                 remove surrounding try/catch regions.  Perhaps we
                 could emit a warning here, instead of silently
                 accepting the conflicting declaration.  */
              if (TREE_NOTHROW (prevailing))
                lto_mark_nothrow_fndecl (prevailing);
            }

          pointer_set_insert (fixup_data->free_list, t);

           /* Also replace t with prevailing defintion.  We don't want to
              insert the other defintion in the seen set as we want to
              replace all instances of it.  */
          *tp = prevailing;
          t = prevailing;
        }
    }
  else if (TYPE_P (t))
    {
      /* Replace t with the prevailing type.  We don't want to insert the
         other type in the seen set as we want to replace all instances of it.  */
      t = gimple_register_type (t);
      *tp = t;
    }

  if (pointer_set_insert (fixup_data->seen, t))
    return NULL;

  /* walk_tree does not visit all reachable nodes that need to be fixed up.
     Hence we do special processing here for those kind of nodes. */
  switch (TREE_CODE (t))
    {
    case FIELD_DECL:
      lto_fixup_field_decl (t, data);
      break;

    case LABEL_DECL:
    case CONST_DECL:
    case PARM_DECL:
    case RESULT_DECL:
    case IMPORTED_DECL:
      lto_fixup_decl_common (t, data);
      break;

    case VAR_DECL:
      lto_fixup_decl_with_vis (t, data);
      break;    

    case TYPE_DECL:
      lto_fixup_decl_non_common (t, data);
      break;

    case FUNCTION_DECL:
      lto_fixup_function (t, data);
      break;

    case TREE_BINFO:
      lto_fixup_binfo (t, data);
      break;

    default:
      if (TYPE_P (t))
        lto_fixup_type (t, data);
      else if (TREE_CODE (t) == CONSTRUCTOR)
        lto_fixup_constructor (t, data);
      else if (CONSTANT_CLASS_P (t))
        LTO_REGISTER_TYPE_AND_FIXUP_SUBTREE (TREE_TYPE (t));
      else if (EXPR_P (t))
        {
          /* walk_tree only handles TREE_OPERANDs. Do the rest here.  */
          lto_fixup_common (t, data);
          LTO_FIXUP_SUBTREE (t->exp.block);
          *walk_subtrees = 1;
        }
      else
        {
          /* Let walk_tree handle sub-trees.  */
          *walk_subtrees = 1;
        }
    }

  return NULL;
}

/* Helper function of lto_fixup_decls. Walks the var and fn streams in STATE,
   replaces var and function decls with the corresponding prevailing def and
   records the old decl in the free-list in DATA. We also record visted nodes
   in the seen-set in DATA to avoid multiple visit for nodes that need not
   to be replaced.  */

static void
lto_fixup_state (struct lto_in_decl_state *state, lto_fixup_data_t *data)
{
  unsigned i, si;
  struct lto_tree_ref_table *table;

  /* Although we only want to replace FUNCTION_DECLs and VAR_DECLs,
     we still need to walk from all DECLs to find the reachable
     FUNCTION_DECLs and VAR_DECLs.  */
  for (si = 0; si < LTO_N_DECL_STREAMS; si++)
    {
      table = &state->streams[si];
      for (i = 0; i < table->size; i++)
        walk_tree (table->trees + i, lto_fixup_tree, data, NULL);
    }
}

/* A callback of htab_traverse. Just extract a state from SLOT and the
   lto_fixup_data_t object from AUX and calls lto_fixup_state. */

static int
lto_fixup_state_aux (void **slot, void *aux)
{
  struct lto_in_decl_state *state = (struct lto_in_decl_state *) *slot;
  lto_fixup_state (state, (lto_fixup_data_t *) aux);
  return 1;
}

/* A callback to pointer_set_traverse. Frees the tree pointed by p. Removes
   from it from the UID -> DECL mapping. */

static bool
free_decl (const void *p, void *data ATTRIBUTE_UNUSED)
{
  const_tree ct = (const_tree) p;
  tree t = CONST_CAST_TREE (ct);

  lto_symtab_clear_resolution (t);

  return true;
}

/* Fix the decls from all FILES. Replaces each decl with the corresponding
   prevailing one.  */

static void
lto_fixup_decls (struct lto_file_decl_data **files)
{
  unsigned int i;
  tree decl;
  struct pointer_set_t *free_list = pointer_set_create ();
  struct pointer_set_t *seen = pointer_set_create ();
  lto_fixup_data_t data;

  data.free_list = free_list;
  data.seen = seen;
  for (i = 0; files[i]; i++)
    {
      struct lto_file_decl_data *file = files[i];
      struct lto_in_decl_state *state = file->global_decl_state;
      lto_fixup_state (state, &data);

      htab_traverse (file->function_decl_states, lto_fixup_state_aux, &data);
    }

  for (i = 0; VEC_iterate (tree, lto_global_var_decls, i, decl); i++)
    {
      tree saved_decl = decl;
      walk_tree (&decl, lto_fixup_tree, &data, NULL);
      if (decl != saved_decl)
        VEC_replace (tree, lto_global_var_decls, i, decl);
    }

  pointer_set_traverse (free_list, free_decl, NULL);
  pointer_set_destroy (free_list);
  pointer_set_destroy (seen);
}

/* Unlink a temporary LTRANS file unless requested otherwise.  */

static void
lto_maybe_unlink (const char *file)
{
  if (!getenv ("WPA_SAVE_LTRANS"))
    {
      if (unlink_if_ordinary (file))
        error ("deleting LTRANS input file %s: %m", file);
    }
  else
    fprintf (stderr, "[Leaving LTRANS input file %s]\n", file);
}

/* Read the options saved from each file in the command line.  Called
   from lang_hooks.post_options which is called by process_options
   right before all the options are used to initialize the compiler.
   This assumes that decode_options has already run, so the
   num_in_fnames and in_fnames are properly set.

   Note that this assumes that all the files had been compiled with
   the same options, which is not a good assumption.  In general,
   options ought to be read from all the files in the set and merged.
   However, it is still unclear what the merge rules should be.  */

void
lto_read_all_file_options (void)
{
  size_t i;

  /* Clear any file options currently saved.  */
  lto_clear_file_options ();

  /* Set the hooks to read ELF sections.  */
  lto_set_in_hooks (NULL, get_section_data, free_section_data);

  for (i = 0; i < num_in_fnames; i++)
    {
      struct lto_file_decl_data *file_data;
      lto_file *file = lto_elf_file_open (in_fnames[i], false);
      if (!file)
        break;

      file_data = XCNEW (struct lto_file_decl_data);
      file_data->file_name = file->filename;
      file_data->fd = -1;
      file_data->section_hash_table = lto_elf_build_section_table (file);

      lto_read_file_options (file_data);

      lto_elf_file_close (file);
      htab_delete (file_data->section_hash_table);
      if (file_data->fd != -1)
        close (file_data->fd);
      free (file_data);
    }

  /* Apply globally the options read from all the files.  */
  lto_reissue_options ();
}


/* Read all the symbols from the input files FNAMES.  NFILES is the
   number of files requested in the command line.  Instantiate a
   global call graph by aggregating all the sub-graphs found in each
   file.  */

static void
read_cgraph_and_symbols (unsigned nfiles, const char **fnames)
{
  unsigned int i, last_file_ix;
  struct lto_file_decl_data **all_file_decl_data;
  FILE *resolution;

  lto_stats.num_input_files = nfiles;

  timevar_push (TV_IPA_LTO_DECL_IO);

  /* Set the hooks so that all of the ipa passes can read in their data.  */
  all_file_decl_data = XNEWVEC (struct lto_file_decl_data *, nfiles + 1);
  lto_set_in_hooks (all_file_decl_data, get_section_data, free_section_data);

  /* Read the resolution file.  */
  resolution = NULL;
  if (resolution_file_name)
    {
      int t;
      unsigned num_objects;

      resolution = fopen (resolution_file_name, "r");
      gcc_assert (resolution != NULL);
      t = fscanf (resolution, "%u", &num_objects);
      gcc_assert (t == 1);

      /* True, since the plugin splits the archives.  */
      gcc_assert (num_objects == nfiles);
    }

  /* Read all of the object files specified on the command line.  */
  for (i = 0, last_file_ix = 0; i < nfiles; ++i)
    {
      struct lto_file_decl_data *file_data = NULL;

      current_lto_file = lto_elf_file_open (fnames[i], false);
      if (!current_lto_file)
        break;

      file_data = lto_file_read (current_lto_file, resolution);
      if (!file_data)
        break;

      all_file_decl_data[last_file_ix++] = file_data;

      lto_elf_file_close (current_lto_file);
      current_lto_file = NULL;
    }

  if (resolution_file_name)
    fclose (resolution);

  all_file_decl_data[last_file_ix] = NULL;

  /* Set the hooks so that all of the ipa passes can read in their data.  */
  lto_set_in_hooks (all_file_decl_data, get_section_data, free_section_data);

  /* Each pass will set the appropriate timer.  */
  timevar_pop (TV_IPA_LTO_DECL_IO);

  /* Read the callgraph.  */
  input_cgraph ();

  ipa_read_summaries ();

  timevar_push (TV_IPA_LTO_DECL_IO);

  lto_fixup_decls (all_file_decl_data);

  /* See if we have multiple decls for a symbol and choose the largest
     one to generate the common.  */
  for (i = 0; i < VEC_length (tree, lto_global_var_decls); ++i)
    {
      tree decl = VEC_index (tree, lto_global_var_decls, i);
      tree prev_decl = NULL_TREE;
      tree size;

      if (TREE_CODE (decl) != VAR_DECL
          || !DECL_LANG_SPECIFIC (decl))
        continue;

      /* Find the preceeding decl of the largest one.  */
      size = DECL_SIZE (decl);
      do
        {
          tree next = (tree) DECL_LANG_SPECIFIC (decl);
          if (tree_int_cst_lt (size, DECL_SIZE (next)))
            {
              size = DECL_SIZE (next);
              prev_decl = decl;
            }
          decl = next;
        }
      while (DECL_LANG_SPECIFIC (decl));

      /* If necessary move the largest decl to the front of the
         chain.  */
      if (prev_decl != NULL_TREE)
        {
          decl = (tree) DECL_LANG_SPECIFIC (prev_decl);
          DECL_LANG_SPECIFIC (prev_decl) = DECL_LANG_SPECIFIC (decl);
          DECL_LANG_SPECIFIC (decl)
            = (struct lang_decl *) VEC_index (tree, lto_global_var_decls, i);
          VEC_replace (tree, lto_global_var_decls, i, decl);
        }

      /* Mark everything apart from the first var as written out and
         unlink the chain.  */
      decl = VEC_index (tree, lto_global_var_decls, i);
      while (DECL_LANG_SPECIFIC (decl))
        {
          tree next = (tree) DECL_LANG_SPECIFIC (decl);
          DECL_LANG_SPECIFIC (decl) = NULL;
          decl = next;
          TREE_ASM_WRITTEN (decl) = true;
        }
    }

  /* FIXME lto. This loop needs to be changed to use the pass manager to
     call the ipa passes directly.  */
  if (!errorcount)
    for (i = 0; i < last_file_ix; i++)
      {
        struct lto_file_decl_data *file_data = all_file_decl_data [i];
        lto_materialize_constructors_and_inits (file_data);
      }

  /* Indicate that the cgraph is built and ready.  */
  cgraph_function_flags_ready = true;

  timevar_pop (TV_IPA_LTO_DECL_IO);
}


/* Materialize all the bodies for all the nodes in the callgraph.  */

static void
materialize_cgraph (void)
{
  tree decl;
  struct cgraph_node *node; 
  unsigned i;
  timevar_id_t lto_timer;

  /* Now that we have input the cgraph, we need to clear all of the aux
     nodes and read the functions if we are not running in WPA mode.  */
  timevar_push (TV_IPA_LTO_GIMPLE_IO);

  for (node = cgraph_nodes; node; node = node->next)
    {
      /* Some cgraph nodes get created on the fly, and they don't need
         to be materialized.  For instance, nodes for nested functions
         where the parent function was not streamed out or builtin
         functions.  Additionally, builtin functions should not be
         materialized and may, in fact, cause confusion because there
         may be a regular function in the file whose assembler name
         matches that of the function.
         See gcc.c-torture/execute/20030125-1.c and
         gcc.c-torture/execute/921215-1.c.  */
      if (node->local.lto_file_data
          && !DECL_IS_BUILTIN (node->decl))
        {
          lto_materialize_function (node);
          lto_stats.num_input_cgraph_nodes++;
        }
    }

  timevar_pop (TV_IPA_LTO_GIMPLE_IO);

  /* Start the appropriate timer depending on the mode that we are
     operating in.  */
  lto_timer = (flag_wpa) ? TV_WHOPR_WPA
              : (flag_ltrans) ? TV_WHOPR_LTRANS
              : TV_LTO;
  timevar_push (lto_timer);

  current_function_decl = NULL;
  set_cfun (NULL);

  /* Inform the middle end about the global variables we have seen.  */
  for (i = 0; VEC_iterate (tree, lto_global_var_decls, i, decl); i++)
    rest_of_decl_compilation (decl, 1, 0);

  /* Fix up any calls to DECLs that have become not exception throwing.  */
  lto_fixup_nothrow_decls ();

  timevar_pop (lto_timer);
}


/* Perform whole program analysis (WPA) on the callgraph and write out the
   optimization plan.  */

static void
do_whole_program_analysis (void)
{
  char **output_files;
  size_t i;
  struct cgraph_node *node; 

  lto_1_to_1_map ();

  /* Note that since we are in WPA mode, materialize_cgraph will not
     actually read in all the function bodies.  It only materializes
     the decls and cgraph nodes so that analysis can be performed.  */
  materialize_cgraph ();

  /* Reading in the cgraph uses different timers, start timing WPA now.  */
  timevar_push (TV_WHOPR_WPA);

  /* FIXME lto. Hack. We should use the IPA passes.  There are a
     number of issues with this now. 1. There is no convenient way to
     do this. 2. Some passes may depend on properties that requires
     the function bodies to compute.  */
  cgraph_function_flags_ready = true;
  bitmap_obstack_initialize (NULL);
  ipa_register_cgraph_hooks ();

  /* Reset inlining information before running IPA inliner.  */
  for (node = cgraph_nodes; node; node = node->next)
    reset_inline_failed (node);

  /* FIXME lto.  We should not call this function directly. */
  pass_ipa_inline.pass.execute ();

  verify_cgraph ();
  bitmap_obstack_release (NULL);

  /* We are about to launch the final LTRANS phase, stop the WPA timer.  */
  timevar_pop (TV_WHOPR_WPA);

  output_files = lto_wpa_write_files ();

  /* Show the LTO report before launching LTRANS.  */
  if (flag_lto_report)
    print_lto_report ();

  lto_execute_ltrans (output_files);

  for (i = 0; output_files[i]; ++i)
    {
      if (output_files[i][0] != '*')
        lto_maybe_unlink (output_files[i]);

      free (output_files[i]);
    }

  XDELETEVEC (output_files);
}


/* Main entry point for the GIMPLE front end.  This front end has
   three main personalities:

   - LTO (-flto).  All the object files on the command line are
     loaded in memory and processed as a single translation unit.
     This is the traditional link-time optimization behavior.

   - WPA (-fwpa).  Only the callgraph and summary information for
     files in the command file are loaded.  A single callgraph
     (without function bodies) is instantiated for the whole set of
     files.  IPA passes are only allowed to analyze the call graph
     and make transformation decisions.  The callgraph is
     partitioned, each partition is written to a new object file
     together with the transformation decisions.

   - LTRANS (-fltrans).  Similar to -flto but it prevents the IPA
     summary files from running again.  Since WPA computed summary
     information and decided what transformations to apply, LTRANS
     simply applies them.  */

void
lto_main (int debug_p ATTRIBUTE_UNUSED)
{
  lto_init_reader ();

  /* Read all the symbols and call graph from all the files in the
     command line.  */
  read_cgraph_and_symbols (num_in_fnames, in_fnames);

  if (!errorcount)
    {
      /* If WPA is enabled analyze the whole call graph and create an
         optimization plan.  Otherwise, read in all the function
         bodies and continue with optimization.  */
      if (flag_wpa)
        do_whole_program_analysis ();
      else
        {
          materialize_cgraph ();

          /* Let the middle end know that we have read and merged all of
             the input files.  */ 
          cgraph_optimize ();

          /* FIXME lto, if the processes spawned by WPA fail, we miss
             the chance to print WPA's report, so WPA will call
             print_lto_report before launching LTRANS.  If LTRANS was
             launched directly by the driver we would not need to do
             this.  */
          if (flag_lto_report)
            print_lto_report ();
        }
    }
}

#include "gt-lto-lto.h"