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/* Callgraph handling code.

   Copyright (C) 2003, 2004, 2005, 2007 Free Software Foundation, Inc.

   Contributed by Jan Hubicka

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/>.  */

/*  This file contains basic routines manipulating call graph and variable pool

The callgraph:

    The call-graph is data structure designed for intra-procedural optimization

    but it is also used in non-unit-at-a-time compilation to allow easier code

    sharing.

    The call-graph consist of nodes and edges represented via linked lists.

    Each function (external or not) corresponds to the unique node (in

    contrast to tree DECL nodes where we can have multiple nodes for each

    function).

    The mapping from declarations to call-graph nodes is done using hash table

    based on DECL_ASSEMBLER_NAME, so it is essential for assembler name to

    not change once the declaration is inserted into the call-graph.

    The call-graph nodes are created lazily using cgraph_node function when

    called for unknown declaration.

    When built, there is one edge for each direct call.  It is possible that

    the reference will be later optimized out.  The call-graph is built

    conservatively in order to make conservative data flow analysis possible.

    The callgraph at the moment does not represent indirect calls or calls

    from other compilation unit.  Flag NEEDED is set for each node that may

    be accessed in such an invisible way and it shall be considered an

    entry point to the callgraph.

    Interprocedural information:

      Callgraph is place to store data needed for interprocedural optimization.

      All data structures are divided into three components: local_info that

      is produced while analyzing the function, global_info that is result

      of global walking of the callgraph on the end of compilation and

      rtl_info used by RTL backend to propagate data from already compiled

      functions to their callers.

    Inlining plans:

      The function inlining information is decided in advance and maintained

      in the callgraph as so called inline plan.

      For each inlined call, the callee's node is cloned to represent the

      new function copy produced by inliner.

      Each inlined call gets a unique corresponding clone node of the callee

      and the data structure is updated while inlining is performed, so

      the clones are eliminated and their callee edges redirected to the

      caller.

      Each edge has "inline_failed" field.  When the field is set to NULL,

      the call will be inlined.  When it is non-NULL it contains a reason

      why inlining wasn't performed.

The varpool data structure:

    Varpool is used to maintain variables in similar manner as call-graph

    is used for functions.  Most of the API is symmetric replacing cgraph

    function prefix by cgraph_varpool  */

#include "config.h"

#include "system.h"

#include "coretypes.h"

#include "tm.h"

#include "tree.h"

#include "tree-inline.h"

#include "langhooks.h"

#include "hashtab.h"

#include "toplev.h"

#include "flags.h"

#include "ggc.h"

#include "debug.h"

#include "target.h"

#include "basic-block.h"

#include "cgraph.h"

#include "varray.h"

#include "output.h"

#include "intl.h"

#include "tree-gimple.h"

#include "tree-dump.h"

static void cgraph_node_remove_callers (struct cgraph_node *node);

static inline void cgraph_edge_remove_caller (struct cgraph_edge *e);

static inline void cgraph_edge_remove_callee (struct cgraph_edge *e);

/* Hash table used to convert declarations into nodes.  */

static GTY((param_is (struct cgraph_node))) htab_t cgraph_hash;

/* The linked list of cgraph nodes.  */

struct cgraph_node *cgraph_nodes;

/* Queue of cgraph nodes scheduled to be lowered.  */

struct cgraph_node *cgraph_nodes_queue;

/* Queue of cgraph nodes scheduled to be expanded.  This is a

   secondary queue used during optimization to accommodate passes that

   may generate new functions that need to be optimized and expanded.  */

struct cgraph_node *cgraph_expand_queue;

/* Number of nodes in existence.  */

int cgraph_n_nodes;

/* Maximal uid used in cgraph nodes.  */

int cgraph_max_uid;

/* Set when whole unit has been analyzed so we can access global info.  */

bool cgraph_global_info_ready = false;

/* Set when the cgraph is fully build and the basic flags are computed.  */

bool cgraph_function_flags_ready = false;

/* Hash table used to convert declarations into nodes.  */

static GTY((param_is (struct cgraph_varpool_node))) htab_t cgraph_varpool_hash;

/* Queue of cgraph nodes scheduled to be lowered and output.  */

struct cgraph_varpool_node *cgraph_varpool_nodes_queue, *cgraph_varpool_first_unanalyzed_node;

/* The linked list of cgraph varpool nodes.  */

struct cgraph_varpool_node *cgraph_varpool_nodes;

/* End of the varpool queue.  */

struct cgraph_varpool_node *cgraph_varpool_last_needed_node;

/* Linked list of cgraph asm nodes.  */

struct cgraph_asm_node *cgraph_asm_nodes;

/* Last node in cgraph_asm_nodes.  */

static GTY(()) struct cgraph_asm_node *cgraph_asm_last_node;

/* The order index of the next cgraph node to be created.  This is

   used so that we can sort the cgraph nodes in order by when we saw

   them, to support -fno-toplevel-reorder.  */

int cgraph_order;

static hashval_t hash_node (const void *);

static int eq_node (const void *, const void *);

/* Returns a hash code for P.  */

static hashval_t

hash_node (const void *p)

{

  const struct cgraph_node *n = (const struct cgraph_node *) p;

  return (hashval_t) DECL_UID (n->decl);

}

/* Returns nonzero if P1 and P2 are equal.  */

static int

eq_node (const void *p1, const void *p2)

{

  const struct cgraph_node *n1 = (const struct cgraph_node *) p1;

  const struct cgraph_node *n2 = (const struct cgraph_node *) p2;

  return DECL_UID (n1->decl) == DECL_UID (n2->decl);

}

/* Allocate new callgraph node and insert it into basic data structures.  */

static struct cgraph_node *

cgraph_create_node (void)

{

  struct cgraph_node *node;

  node = GGC_CNEW (struct cgraph_node);

  node->next = cgraph_nodes;

  node->uid = cgraph_max_uid++;

  node->order = cgraph_order++;

  if (cgraph_nodes)

    cgraph_nodes->previous = node;

  node->previous = NULL;

  node->global.estimated_growth = INT_MIN;

  cgraph_nodes = node;

  cgraph_n_nodes++;

  return node;

}

/* Return cgraph node assigned to DECL.  Create new one when needed.  */

struct cgraph_node *

cgraph_node (tree decl)

{

  struct cgraph_node key, *node, **slot;

  gcc_assert (TREE_CODE (decl) == FUNCTION_DECL);

  if (!cgraph_hash)

    cgraph_hash = htab_create_ggc (10, hash_node, eq_node, NULL);

  key.decl = decl;

  slot = (struct cgraph_node **) htab_find_slot (cgraph_hash, &key, INSERT);

  if (*slot)

    {

      node = *slot;

      if (!node->master_clone)

        node->master_clone = node;

      return node;

    }

  node = cgraph_create_node ();

  node->decl = decl;

  *slot = node;

  if (DECL_CONTEXT (decl) && TREE_CODE (DECL_CONTEXT (decl)) == FUNCTION_DECL)

    {

      node->origin = cgraph_node (DECL_CONTEXT (decl));

      node->next_nested = node->origin->nested;

      node->origin->nested = node;

      node->master_clone = node;

    }

  return node;

}

/* Insert already constructed node into hashtable.  */

void

cgraph_insert_node_to_hashtable (struct cgraph_node *node)

{

  struct cgraph_node **slot;

  slot = (struct cgraph_node **) htab_find_slot (cgraph_hash, node, INSERT);

  gcc_assert (!*slot);

  *slot = node;

}

/* Compare ASMNAME with the DECL_ASSEMBLER_NAME of DECL.  */

static bool

decl_assembler_name_equal (tree decl, tree asmname)

{

  tree decl_asmname = DECL_ASSEMBLER_NAME (decl);

  if (decl_asmname == asmname)

    return true;

  /* If the target assembler name was set by the user, things are trickier.

     We have a leading '*' to begin with.  After that, it's arguable what

     is the correct thing to do with -fleading-underscore.  Arguably, we've

     historically been doing the wrong thing in assemble_alias by always

     printing the leading underscore.  Since we're not changing that, make

     sure user_label_prefix follows the '*' before matching.  */

  if (IDENTIFIER_POINTER (decl_asmname)[0] == '*')

    {

      const char *decl_str = IDENTIFIER_POINTER (decl_asmname) + 1;

      size_t ulp_len = strlen (user_label_prefix);

      if (ulp_len == 0)

        ;

      else if (strncmp (decl_str, user_label_prefix, ulp_len) == 0)

        decl_str += ulp_len;

      else

        return false;

      return strcmp (decl_str, IDENTIFIER_POINTER (asmname)) == 0;

    }

  return false;

}

/* Return the cgraph node that has ASMNAME for its DECL_ASSEMBLER_NAME.

   Return NULL if there's no such node.  */

struct cgraph_node *

cgraph_node_for_asm (tree asmname)

{

  struct cgraph_node *node;

  for (node = cgraph_nodes; node ; node = node->next)

    if (decl_assembler_name_equal (node->decl, asmname))

      return node;

  return NULL;

}

/* Returns a hash value for X (which really is a die_struct).  */

static hashval_t

edge_hash (const void *x)

{

  return htab_hash_pointer (((struct cgraph_edge *) x)->call_stmt);

}

/* Return nonzero if decl_id of die_struct X is the same as UID of decl *Y.  */

static int

edge_eq (const void *x, const void *y)

{

  return ((struct cgraph_edge *) x)->call_stmt == y;

}

/* Return callgraph edge representing CALL_EXPR statement.  */

struct cgraph_edge *

cgraph_edge (struct cgraph_node *node, tree call_stmt)

{

  struct cgraph_edge *e, *e2;

  int n = 0;

  if (node->call_site_hash)

    return htab_find_with_hash (node->call_site_hash, call_stmt,

                                htab_hash_pointer (call_stmt));

  /* This loop may turn out to be performance problem.  In such case adding

     hashtables into call nodes with very many edges is probably best

     solution.  It is not good idea to add pointer into CALL_EXPR itself

     because we want to make possible having multiple cgraph nodes representing

     different clones of the same body before the body is actually cloned.  */

  for (e = node->callees; e; e= e->next_callee)

    {

      if (e->call_stmt == call_stmt)

        break;

      n++;

    }

  if (n > 100)

    {

      node->call_site_hash = htab_create_ggc (120, edge_hash, edge_eq, NULL);

      for (e2 = node->callees; e2; e2 = e2->next_callee)

        {

          void **slot;

          slot = htab_find_slot_with_hash (node->call_site_hash,

                                           e2->call_stmt,

                                           htab_hash_pointer (e2->call_stmt),

                                           INSERT);

          gcc_assert (!*slot);

          *slot = e2;

        }

    }

  return e;

}

/* Change call_smtt of edge E to NEW_STMT.  */

void

cgraph_set_call_stmt (struct cgraph_edge *e, tree new_stmt)

{

  if (e->caller->call_site_hash)

    {

      htab_remove_elt_with_hash (e->caller->call_site_hash,

                                 e->call_stmt,

                                 htab_hash_pointer (e->call_stmt));

    }

  e->call_stmt = new_stmt;

  if (e->caller->call_site_hash)

    {

      void **slot;

      slot = htab_find_slot_with_hash (e->caller->call_site_hash,

                                       e->call_stmt,

                                       htab_hash_pointer

                                       (e->call_stmt), INSERT);

      gcc_assert (!*slot);

      *slot = e;

    }

}

/* Create edge from CALLER to CALLEE in the cgraph.  */

struct cgraph_edge *

cgraph_create_edge (struct cgraph_node *caller, struct cgraph_node *callee,

                    tree call_stmt, gcov_type count, int nest)

{

  struct cgraph_edge *edge = GGC_NEW (struct cgraph_edge);

#ifdef ENABLE_CHECKING

  struct cgraph_edge *e;

  for (e = caller->callees; e; e = e->next_callee)

    gcc_assert (e->call_stmt != call_stmt);

#endif

  gcc_assert (get_call_expr_in (call_stmt));

  if (!DECL_SAVED_TREE (callee->decl))

    edge->inline_failed = N_("function body not available");

  else if (callee->local.redefined_extern_inline)

    edge->inline_failed = N_("redefined extern inline functions are not "

                             "considered for inlining");

  else if (callee->local.inlinable)

    edge->inline_failed = N_("function not considered for inlining");

  else

    edge->inline_failed = N_("function not inlinable");

  edge->aux = NULL;

  edge->caller = caller;

  edge->callee = callee;

  edge->call_stmt = call_stmt;

  edge->prev_caller = NULL;

  edge->next_caller = callee->callers;

  if (callee->callers)

    callee->callers->prev_caller = edge;

  edge->prev_callee = NULL;

  edge->next_callee = caller->callees;

  if (caller->callees)

    caller->callees->prev_callee = edge;

  caller->callees = edge;

  callee->callers = edge;

  edge->count = count;

  edge->loop_nest = nest;

  if (caller->call_site_hash)

    {

      void **slot;

      slot = htab_find_slot_with_hash (caller->call_site_hash,

                                       edge->call_stmt,

                                       htab_hash_pointer

                                         (edge->call_stmt),

                                       INSERT);

      gcc_assert (!*slot);

      *slot = edge;

    }

  return edge;

}

/* Remove the edge E from the list of the callers of the callee.  */

static inline void

cgraph_edge_remove_callee (struct cgraph_edge *e)

{

  if (e->prev_caller)

    e->prev_caller->next_caller = e->next_caller;

  if (e->next_caller)

    e->next_caller->prev_caller = e->prev_caller;

  if (!e->prev_caller)

    e->callee->callers = e->next_caller;

}

/* Remove the edge E from the list of the callees of the caller.  */

static inline void

cgraph_edge_remove_caller (struct cgraph_edge *e)

{

  if (e->prev_callee)

    e->prev_callee->next_callee = e->next_callee;

  if (e->next_callee)

    e->next_callee->prev_callee = e->prev_callee;

  if (!e->prev_callee)

    e->caller->callees = e->next_callee;

  if (e->caller->call_site_hash)

    htab_remove_elt_with_hash (e->caller->call_site_hash,

                               e->call_stmt,

                               htab_hash_pointer (e->call_stmt));

}

/* Remove the edge E in the cgraph.  */

void

cgraph_remove_edge (struct cgraph_edge *e)

{

  /* Remove from callers list of the callee.  */

  cgraph_edge_remove_callee (e);

  /* Remove from callees list of the callers.  */

  cgraph_edge_remove_caller (e);

}

/* Redirect callee of E to N.  The function does not update underlying

   call expression.  */

void

cgraph_redirect_edge_callee (struct cgraph_edge *e, struct cgraph_node *n)

{

  /* Remove from callers list of the current callee.  */

  cgraph_edge_remove_callee (e);

  /* Insert to callers list of the new callee.  */

  e->prev_caller = NULL;

  if (n->callers)

    n->callers->prev_caller = e;

  e->next_caller = n->callers;

  n->callers = e;

  e->callee = n;

}

/* Remove all callees from the node.  */

void

cgraph_node_remove_callees (struct cgraph_node *node)

{

  struct cgraph_edge *e;

  /* It is sufficient to remove the edges from the lists of callers of

     the callees.  The callee list of the node can be zapped with one

     assignment.  */

  for (e = node->callees; e; e = e->next_callee)

    cgraph_edge_remove_callee (e);

  node->callees = NULL;

  if (node->call_site_hash)

    {

      htab_delete (node->call_site_hash);

      node->call_site_hash = NULL;

    }

}

/* Remove all callers from the node.  */

static void

cgraph_node_remove_callers (struct cgraph_node *node)

{

  struct cgraph_edge *e;

  /* It is sufficient to remove the edges from the lists of callees of

     the callers.  The caller list of the node can be zapped with one

     assignment.  */

  for (e = node->callers; e; e = e->next_caller)

    cgraph_edge_remove_caller (e);

  node->callers = NULL;

}

/* Remove the node from cgraph.  */

void

cgraph_remove_node (struct cgraph_node *node)

{

  void **slot;

  bool kill_body = false;

  cgraph_node_remove_callers (node);

  cgraph_node_remove_callees (node);

  /* Incremental inlining access removed nodes stored in the postorder list.

     */

  node->needed = node->reachable = false;

  while (node->nested)

    cgraph_remove_node (node->nested);

  if (node->origin)

    {

      struct cgraph_node **node2 = &node->origin->nested;

      while (*node2 != node)

        node2 = &(*node2)->next_nested;

      *node2 = node->next_nested;

    }

  if (node->previous)

    node->previous->next = node->next;

  else

    cgraph_nodes = node->next;

  if (node->next)

    node->next->previous = node->previous;

  node->next = NULL;

  node->previous = NULL;

  slot = htab_find_slot (cgraph_hash, node, NO_INSERT);

  if (*slot == node)

    {

      if (node->next_clone)

      {

        struct cgraph_node *new_node = node->next_clone;

        struct cgraph_node *n;

        /* Make the next clone be the master clone */

        for (n = new_node; n; n = n->next_clone)

          n->master_clone = new_node;

        *slot = new_node;

        node->next_clone->prev_clone = NULL;

      }

      else

        {

          htab_clear_slot (cgraph_hash, slot);

          kill_body = true;

        }

    }

  else

    {

      node->prev_clone->next_clone = node->next_clone;

      if (node->next_clone)

        node->next_clone->prev_clone = node->prev_clone;

    }

  /* While all the clones are removed after being proceeded, the function

     itself is kept in the cgraph even after it is compiled.  Check whether

     we are done with this body and reclaim it proactively if this is the case.

     */

  if (!kill_body && *slot)

    {

      struct cgraph_node *n = (struct cgraph_node *) *slot;

      if (!n->next_clone && !n->global.inlined_to

          && (cgraph_global_info_ready

              && (TREE_ASM_WRITTEN (n->decl) || DECL_EXTERNAL (n->decl))))

        kill_body = true;

    }

  if (kill_body && flag_unit_at_a_time)

    {

      DECL_SAVED_TREE (node->decl) = NULL;

      DECL_STRUCT_FUNCTION (node->decl) = NULL;

      DECL_INITIAL (node->decl) = error_mark_node;

    }

  node->decl = NULL;

  if (node->call_site_hash)

    {

      htab_delete (node->call_site_hash);

      node->call_site_hash = NULL;

    }

  cgraph_n_nodes--;

  /* Do not free the structure itself so the walk over chain can continue.  */

}

/* Notify finalize_compilation_unit that given node is reachable.  */

void

cgraph_mark_reachable_node (struct cgraph_node *node)

{

  if (!node->reachable && node->local.finalized)

    {

      notice_global_symbol (node->decl);

      node->reachable = 1;

      gcc_assert (!cgraph_global_info_ready);

      node->next_needed = cgraph_nodes_queue;

      cgraph_nodes_queue = node;

    }

}

/* Likewise indicate that a node is needed, i.e. reachable via some

   external means.  */

void

cgraph_mark_needed_node (struct cgraph_node *node)

{

  node->needed = 1;

  cgraph_mark_reachable_node (node);

}

/* Return local info for the compiled function.  */

struct cgraph_local_info *

cgraph_local_info (tree decl)

{

  struct cgraph_node *node;

  gcc_assert (TREE_CODE (decl) == FUNCTION_DECL);

  node = cgraph_node (decl);

  return &node->local;

}

/* Return local info for the compiled function.  */

struct cgraph_global_info *

cgraph_global_info (tree decl)

{

  struct cgraph_node *node;

  gcc_assert (TREE_CODE (decl) == FUNCTION_DECL && cgraph_global_info_ready);

  node = cgraph_node (decl);

  return &node->global;

}

/* Return local info for the compiled function.  */

struct cgraph_rtl_info *

cgraph_rtl_info (tree decl)

{

  struct cgraph_node *node;

  gcc_assert (TREE_CODE (decl) == FUNCTION_DECL);

  node = cgraph_node (decl);

  if (decl != current_function_decl

      && !TREE_ASM_WRITTEN (node->decl))

    return NULL;

  return &node->rtl;

}

/* Return name of the node used in debug output.  */

const char *

cgraph_node_name (struct cgraph_node *node)

{

  return lang_hooks.decl_printable_name (node->decl, 2);

}

/* Return name of the node used in debug output.  */

static const char *

cgraph_varpool_node_name (struct cgraph_varpool_node *node)

{

  return lang_hooks.decl_printable_name (node->decl, 2);

}

/* Names used to print out the availability enum.  */

static const char * const availability_names[] =

  {"unset", "not_available", "overwrittable", "available", "local"};

/* Dump given cgraph node.  */

void

dump_cgraph_node (FILE *f, struct cgraph_node *node)

{

  struct cgraph_edge *edge;

  fprintf (f, "%s/%i:", cgraph_node_name (node), node->uid);

  if (node->global.inlined_to)

    fprintf (f, " (inline copy in %s/%i)",

             cgraph_node_name (node->global.inlined_to),

             node->global.inlined_to->uid);

  if (cgraph_function_flags_ready)

    fprintf (f, " availability:%s",

             availability_names [cgraph_function_body_availability (node)]);

  if (node->master_clone && node->master_clone->uid != node->uid)