cgana.c

/*
 * Project:     libFIRM
 * File name:   ir/ana/cgana.c
 * Purpose:     Intraprozedural analyses to estimate the call graph.
 * Author:      Hubert Schmid
 * Modified by:
 * Created:     09.06.2002
 * CVS-ID:      $Id$
 * Copyright:   (c) 1999-2003 Universitt Karlsruhe
 * Licence:     This file protected by GPL -  GNU GENERAL PUBLIC LICENSE.
 */

/** @file cgana.c
 *
 * Interprocedural analysis to estimate the calling relation.
 *
 * This analysis computes all entities representing methods that
 * can be called at a Call node.  Further it computes a set of
 * methods that are 'free', i.e., their adress is handled by
 * the program directly, or they are visible external.
 */

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#ifdef HAVE_STRING_H
# include <string.h>
#endif

#include "cgana.h"
#include "rta.h"

#include "xmalloc.h"
#include "irnode_t.h"
#include "irmode_t.h"
#include "irprog_t.h"
#include "irgwalk.h"
#include "ircons.h"
#include "irgmod.h"
#include "iropt.h"

#include "irflag_t.h"
#include "dbginfo_t.h"
#include "iropt_dbg.h"

#include "eset.h"
#include "pmap.h"
#include "array.h"

#include "irdump.h"

#include "irhooks.h"



/* unambiguous address used as a mark. */
static void *MARK = &MARK;

static eset *entities = NULL;

/*--------------------------------------------------------------------------*/
/* The analysis                                                             */
/*--------------------------------------------------------------------------*/


/*--------------------------------------------------------------------------*/
/* Initialize datastructures, remove unwanted constructs, optimize          */
/* call target computations.                                                */
/*--------------------------------------------------------------------------*/

/** Returns the entity that contains the implementation of the inherited
 *  entity if available, else returns the entity passed. */
static entity *get_inherited_methods_implementation(entity *inh_meth) {
  assert(get_atomic_ent_value(inh_meth) && "constant entity without value");
  assert((get_irn_op(get_atomic_ent_value(inh_meth)) == op_SymConst) &&
         (get_SymConst_kind(get_atomic_ent_value(inh_meth)) == symconst_addr_ent) &&
         "Complex constant values not supported -- address of method should be straight constant!");

  return get_SymConst_entity(get_atomic_ent_value(inh_meth));
}

/** Collect the entity representing the implementation of this
 *  method (not the same if inherited) and all entities for overwriting
 *  implementations in "set".
 *  If the implementation of the method is not included in the
 *  compilation unit "open" is set to true.
 *  A recursive descend in the overwritten relation.
 *  Cycle-free, therefore must terminate.
 *
 * @param method
 * @param set      A set of entities.
 * @param size     Number of entities in set.
 * @param open
 */
static void collect_impls(entity *method, eset *set, int *size, int *open) {
  int i;
  entity *impl;

  /* Add the implementation to the set if it contains an irg, else
     remember that there are more methods called. */
  impl = method;
  if (get_entity_peculiarity(method) == peculiarity_inherited)
    impl = get_inherited_methods_implementation(method);

  if (get_entity_peculiarity(method) != peculiarity_description) {
    eset_insert(set, impl);
    ++(*size);
  }

  /*- recursive descent -*/
  for (i = get_entity_n_overwrittenby(method) - 1; i >= 0; --i)
    collect_impls(get_entity_overwrittenby(method, i), set, size, open);
}

/** Alle Methoden bestimmen, die die bergebene Methode berschreiben
 *  (und implementieren). In der zurckgegebenen Reihung kommt jede
 *  Methode nur einmal vor. Der Wert 'NULL' steht fr unbekannte
 *  (externe) Methoden. Die zurckgegebene Reihung mu vom Aufrufer
 *  wieder freigegeben werden (siehe "DEL_ARR_F"). Gibt es berhaupt
 *  keine Methoden, die "method" berschreiben, so gibt die Methode
 *  "NULL" zurck.
 *
 *  @param method
 */
static entity ** get_impl_methods(entity * method) {
  eset * set = eset_create();
  int size = 0;
  entity ** arr;
  int open = 0;

  /* Collect all method entities that can be called here */
  collect_impls(method, set, &size, &open);

  /* Vorgaenger einfuegen. */
  if (size == 0 && !open) {
    /* keine implementierte berschriebene Methode */
    arr = NULL;
  } else if (open) {
    entity * ent;
    arr = NEW_ARR_F(entity *, size + 1);
    arr[0] = NULL;  /* Represents open method */
    for (ent = eset_first(set); size > 0; ent = eset_next(set), --size)
      arr[size] = ent;
  } else {
    entity * ent;
    arr = NEW_ARR_F(entity *, size);
    for (size -= 1, ent = eset_first(set); size >= 0; ent = eset_next(set), --size)
      arr[size] = ent;
  }
  eset_destroy(set);
  return arr;
}

/** Analyze address computations.
 *
 *  Compute for all Sel nodes the set of methods that can be selected.
 *  For each entity we store the set of subentities in the link field.
 *
 *  Further do some optimizations:
 *  - Call standard optimizations for Sel nodes: this removes polymorphic
 *    calls.
 *  - If the node is a SymConst(name) replace it by SymConst(ent) if possible.
 *    For this we precomputed a map name->entity.  Nowadays, we no more support
 *    this and assert.
 *  - If the node is a Sel:
 *    If we found only a single method that can be called, replace the Sel
 *    by a SymConst.  This is more powerful than the analysis in opt_polymorphy,
 *    as here we walk the type graph.  In opt_polymorphy we only apply a local
 *    pattern.
 *
 *  @param node The node to analyze
 *  @param env  A map that maps names of entities to the entities.
 */
static void sel_methods_walker(ir_node * node, void *env) {
  pmap *ldname_map = env;
  entity **arr;

  /* Call standard optimizations */
  if (is_Sel(node)) {
    ir_node *new_node = optimize_in_place(node);
    if (node != new_node)
      exchange(node, new_node);
  }

  /* replace SymConst(name)-operations by SymConst(ent) */
  if (get_irn_op(node) == op_SymConst) {
    if (get_SymConst_kind(node) == symconst_addr_name) {
      pmap_entry * entry = pmap_find(ldname_map, (void *) get_SymConst_name(node));
      if (entry != NULL) { /* Method is declared in the compiled code */
        assert(0 && "There should not be a SymConst[addr_name] addressing a method with an implementation"
                    "in this compilation unit.  Use a SymConst[addr_ent].");
      }
    }
  }
  else if (get_irn_op(node) == op_Sel &&
           is_Method_type(get_entity_type(get_Sel_entity(node)))) {
    entity * ent = get_SymConst_entity(get_atomic_ent_value(get_Sel_entity(node)));
    assert(get_entity_peculiarity(ent) != peculiarity_inherited);

    if (!eset_contains(entities, ent)) {
      /* Entity not yet handled. Find all (internal or external)
       * implemented methods that overwrites this entity.
       * This set is stored in the entity link. */
      set_entity_link(ent, get_impl_methods(ent));
      eset_insert(entities, ent);
    }

    /* -- As an add on we get an optimization that removes polymorphic calls.
       This optimization is more powerful than that in transform_node_Sel().  -- */
    arr = get_entity_link(ent);
    if (arr == NULL) {
      /*
       * The Sel node never returns a pointer to a usable method.
       * We could not call it, but it may be description:
       * We call a method in a dead part of the program.
       */
      assert (get_entity_peculiarity(ent) == peculiarity_description);
    }
    else if (get_opt_optimize() && get_opt_closed_world() && get_opt_dyn_meth_dispatch() &&
        (ARR_LEN(arr) == 1 && arr[0] != NULL)) {
      ir_node *new_node;

      /*
       * The Sel node returns only one possible method.
       * So we could replace the Sel node by a SymConst.
       * This method must exists.
       */
      set_irg_current_block(current_ir_graph, get_nodes_block(node));
      assert(get_entity_peculiarity(get_SymConst_entity(get_atomic_ent_value(arr[0]))) ==
             peculiarity_existent);
      new_node = copy_const_value(get_irn_dbg_info(node), get_atomic_ent_value(arr[0]));
      DBG_OPT_POLY(node, new_node);
      exchange(node, new_node);
    }
  }
}

/** Initialize auxiliary data structures.
 *
 *  Computes a set of entities that overwrite an entity and contain
 *  an implementation. The set is stored in the entity's link field.
 *
 *  Further replaces Sel nodes where this set contains exactly one
 *  method by SymConst nodes.
 *  Finally asserts if there is a SymConst(name) if there could be a
 *  SymConst(ent). */
static void sel_methods_init(void) {
  int i;
  pmap * ldname_map = pmap_create();   /* Map entity names to entities: to replace
                                          SymConst(name) by SymConst(ent). */
  assert(entities == NULL);
  entities = eset_create();
  for (i = get_irp_n_irgs() - 1; i >= 0; --i) {
    entity * ent = get_irg_entity(get_irp_irg(i));
    /* only external visible methods are allowed to call by a SymConst_ptr_name */
    if (get_entity_visibility(ent) != visibility_local) {
      pmap_insert(ldname_map, (void *) get_entity_ld_ident(ent), ent);
    }
  }

  all_irg_walk(sel_methods_walker, NULL, ldname_map);
  pmap_destroy(ldname_map);
}

/*--------------------------------------------------------------------------*/
/* Find free methods.
 *
 * We expect that each entity has an array with all implementations in its
 * link field.                                                              */
/*--------------------------------------------------------------------------*/

/**
 * Returns an array of all methods that could be called at a Sel node.
 * This array contains every entry only once.
 *
 * @param sel  the Sel node
 */
static entity ** get_Sel_arr(ir_node * sel) {
  static entity ** NULL_ARRAY = NULL;
  entity * ent;
  entity ** arr;

  assert(is_Sel(sel));
  ent = get_Sel_entity(sel);
  ent = get_inherited_methods_implementation(ent);

  assert(is_Method_type(get_entity_type(ent))); /* what else? */
  arr = get_entity_link(ent);
  if (arr) {
    return arr;
  } else {
    /* "NULL" zeigt an, dass keine Implementierung existiert. Dies
     * kann fr polymorphe (abstrakte) Methoden passieren. */
    if (!NULL_ARRAY) {
      NULL_ARRAY = NEW_ARR_F(entity *, 0);
    }
    return NULL_ARRAY;
  }
}

/**
 * Returns the number of possible called methods at a Sel node.
 *
 * @param sel  the Sel node
 */
static int get_Sel_n_methods(ir_node * sel) {
  return ARR_LEN(get_Sel_arr(sel));
}

/**
 * Returns the ith possible called method entity at a Sel node.
 */
static entity * get_Sel_method(ir_node * sel, int pos) {
  entity ** arr = get_Sel_arr(sel);
  assert(pos >= 0 && pos < ARR_LEN(arr));
  return arr[pos];
}

static void free_mark(ir_node * node, eset * set);

static void free_mark_proj(ir_node * node, long n, eset * set) {
  assert(get_irn_mode(node) == mode_T);
  if (get_irn_link(node) == MARK) {
    /* already visited */
    return;
  }
  set_irn_link(node, MARK);
  switch (get_irn_opcode(node)) {
  case iro_Proj: {
    /* proj_proj: in einem "sinnvollen" Graphen kommt jetzt ein
     * op_Tuple oder ein Knoten, der in "free_ana_walker" behandelt
     * wird. */
    ir_node * pred = get_Proj_pred(node);
    if (get_irn_link(pred) != MARK && get_irn_op(pred) == op_Tuple) {
      free_mark_proj(get_Tuple_pred(pred, get_Proj_proj(node)), n, set);
    } else {
      /* nothing: da in "free_ana_walker" behandelt. */
    }
    break;
  }

  case iro_Tuple:
    free_mark(get_Tuple_pred(node, n), set);
    break;

  case iro_Id:
    free_mark_proj(get_Id_pred(node), n, set);
    break;

  case iro_Start:
  case iro_Alloc:
  case iro_Load:
    /* nothing: Die Operationen werden in free_ana_walker() selbst
     * behandelt. */
    break;

  default:
    assert(0 && "unexpected opcode or opcode not implemented");
    break;
  }
  set_irn_link(node, NULL);
}

/**
 * Called for predecessors nodes of "interesting" ones.
 * Interesting ones include all nodes that can somehow make
 * a method visible.
 *
 * If a method (or a set of methods in case of polymorph calls) gets visible,
 * add it to the set of 'free' methods
 *
 * @param node  the current visited node
 * @param set   the set of all free methods
 */
static void free_mark(ir_node *node, eset * set) {
  int i;

  if (get_irn_link(node) == MARK)
    return; /* already visited */

  set_irn_link(node, MARK);

  switch (get_irn_opcode(node)) {
  case iro_Sel: {
    entity * ent = get_Sel_entity(node);
    if (is_Method_type(get_entity_type(ent))) {
      for (i = get_Sel_n_methods(node) - 1; i >= 0; --i) {
        eset_insert(set, get_Sel_method(node, i));
      }
    }
    break;
  }
  case iro_SymConst:
    if (get_SymConst_kind(node) == symconst_addr_ent) {
      entity * ent = get_SymConst_entity(node);
      if (is_Method_type(get_entity_type(ent))) {
        eset_insert(set, ent);
      }
    } else {
      assert(get_SymConst_kind(node) == symconst_addr_name);
      /* nothing: SymConst points to extern method */
    }
    break;

  case iro_Phi:
    for (i = get_Phi_n_preds(node) - 1; i >= 0; --i) {
      free_mark(get_Phi_pred(node, i), set);
    }
    break;
  case iro_Id:
    free_mark(get_Id_pred(node), set);
    break;
  case iro_Proj:
    free_mark_proj(get_Proj_pred(node), get_Proj_proj(node), set);
    break;
  default:
    /* nothing: Wird unten behandelt! */
    break;
  }
  set_irn_link(node, NULL);
}

/**
 * post-walker. Find method addresses.
 */
static void free_ana_walker(ir_node *node, void *env) {
  eset *set = env;
  int i;

  if (get_irn_link(node) == MARK) {
    /* already visited */
    return;
  }
  switch (get_irn_opcode(node)) {
  /* special nodes */
  case iro_Sel:
  case iro_SymConst:
  case iro_Const:
  case iro_Phi:
  case iro_Id:
  case iro_Proj:
  case iro_Tuple:
    /* nothing */
    break;
  /* Sonderbehandlung, da der Funktionszeigereingang natrlich kein
   * Verrter ist. */
  case iro_Call:
    set_irn_link(node, MARK);
    for (i = get_Call_n_params(node) - 1; i >= 0; --i) {
      ir_node *pred = get_Call_param(node, i);
      if (mode_is_reference(get_irn_mode(pred))) {
        free_mark(pred, set);
      }
    }
    break;
  /* other nodes: Alle anderen Knoten nehmen wir als Verrter an, bis
   * jemand das Gegenteil implementiert. */
  default:
    set_irn_link(node, MARK);
    for (i = get_irn_arity(node) - 1; i >= 0; --i) {
      ir_node * pred = get_irn_n(node, i);
      if (mode_is_reference(get_irn_mode(pred))) {
        free_mark(pred, set);
      }
    }
    break;
  }
  set_irn_link(node, NULL);
}

/**
 * Add all method addresses in global initializers to the set.
 *
 * @note
 * We do NOT check the type here, just it it's an entity address.
 * The reason for this is code like:
 *
 * void *p = function;
 *
 * which is sometimes used to anchor functions.
 */
static void add_method_address(entity *ent, eset *set)
{
  ir_node *n;
  ir_type *tp;
  int i;

  /* do not check uninitialized values */
  if (get_entity_variability(ent) == variability_uninitialized)
    return;

  if (is_atomic_entity(ent)) {
    tp = get_entity_type(ent);

    /* ignore methods: these of course reference it's address */
    if (is_Method_type(tp))
      return;

    /* let's check if it's the address of a function */
    n = get_atomic_ent_value(ent);
    if (get_irn_op(n) == op_SymConst) {
      if (get_SymConst_kind(n) == symconst_addr_ent) {
        ent = get_SymConst_entity(n);

        if (is_Method_type(get_entity_type(ent)))
          eset_insert(set, ent);
      }
    }
  }
  else {
    for (i = get_compound_ent_n_values(ent) - 1; i >= 0; --i) {
      n = get_compound_ent_value(ent, i);

      /* let's check if it's the address of a function */
      if (get_irn_op(n) == op_SymConst) {
        if (get_SymConst_kind(n) == symconst_addr_ent) {
          entity *ent = get_SymConst_entity(n);

          if (is_Method_type(get_entity_type(ent)))
            eset_insert(set, ent);
        }
      }
    }
  }
}

/**
 * returns a list of 'free' methods, i.e., the methods that can be called
 * from external or via function pointers.
 *
 * Die Datenstrukturen fr sel-Methoden (sel_methods) mu vor dem
 * Aufruf von "get_free_methods" aufgebaut sein. Die (internen)
 * SymConst(name)-Operationen mssen in passende SymConst(ent)-Operationen
 * umgewandelt worden sein, d.h. SymConst-Operationen verweisen immer
 * auf eine echt externe Methode.
 */
static entity ** get_free_methods(void)
{
  eset *free_set = eset_create();
  int i;
  entity **arr = NEW_ARR_F(entity *, 0);
  entity *ent;
  ir_graph *irg;
  ir_type *glob;

  for (i = get_irp_n_irgs() - 1; i >= 0; --i) {
    irg = get_irp_irg(i);
    ent = get_irg_entity(irg);
    /* insert "external visible" methods. */
    if (get_entity_visibility(ent) != visibility_local) {
      eset_insert(free_set, ent);
    }
    /* Finde alle Methoden die in dieser Methode extern sichtbar werden,
       z.B. da die Adresse einer Methode abgespeichert wird. */
    irg_walk_graph(irg, NULL, free_ana_walker, free_set);
  }

  /* insert sticky methods, too */
  for (i = get_irp_n_irgs() - 1; i >= 0; --i) {
    ent = get_irg_entity(get_irp_irg(i));
    /* insert "sticky" methods. */
    if (get_entity_stickyness (ent) == stickyness_sticky) {
      eset_insert(free_set, ent);
    }
  }

  /* insert all methods the initializes global variables */
  glob = get_glob_type();
  for (i = get_class_n_members(glob) - 1; i >= 0; --i) {
    ent = get_class_member(glob, i);

    add_method_address(ent, free_set);
  }

  /* the main program is even then "free", if it's not external visible. */
  irg = get_irp_main_irg();
  if (irg)
    eset_insert(free_set, get_irg_entity(irg));

  /* Finally, transform the set into an array. */
  for (ent = eset_first(free_set); ent; ent = eset_next(free_set)) {
    ARR_APP1(entity *, arr, ent);
  }
  eset_destroy(free_set);

  return arr;
}

/*--------------------------------------------------------------------------*/
/* Callee analysis.                                                         */
/*--------------------------------------------------------------------------*/

static void callee_ana_node(ir_node * node, eset * methods);

static void callee_ana_proj(ir_node * node, long n, eset * methods) {
  assert(get_irn_mode(node) == mode_T);
  if (get_irn_link(node) == MARK) {
    /* already visited */
    return;
  }
  set_irn_link(node, MARK);

  switch (get_irn_opcode(node)) {
  case iro_Proj: {
    /* proj_proj: in einem "sinnvollen" Graphen kommt jetzt ein
     * op_Tuple oder ein Knoten, der eine "freie Methode"
     * zurckgibt. */
    ir_node * pred = get_Proj_pred(node);
    if (get_irn_link(pred) != MARK) {
      if (get_irn_op(pred) == op_Tuple) {
        callee_ana_proj(get_Tuple_pred(pred, get_Proj_proj(node)), n, methods);
      } else {
        eset_insert(methods, MARK); /* free method -> unknown */
      }
    }
    break;
  }

  case iro_Tuple:
    callee_ana_node(get_Tuple_pred(node, n), methods);
    break;

  case iro_Id:
    callee_ana_proj(get_Id_pred(node), n, methods);
    break;

  default:
    eset_insert(methods, MARK); /* free method -> unknown */
    break;
  }

  set_irn_link(node, NULL);
}

/**
 * Analyse a Call address.
 *
 * @param node     the node representing the call address
 * @param methods  after call contains the set of all possibly called entities
 */
static void callee_ana_node(ir_node *node, eset *methods) {
  int i;

  assert(mode_is_reference(get_irn_mode(node)) || is_Bad(node));
  /* Beware of recursion */
  if (get_irn_link(node) == MARK) {
    /* already visited */
    return;
  }
  set_irn_link(node, MARK);

  switch (get_irn_opcode(node)) {
  case iro_Const:
    /* A direct address call. We tread this as an external
       call and ignore it completely. */
    eset_insert(methods, MARK); /* free method -> unknown */
    break;
  case iro_SymConst:
    if (get_SymConst_kind(node) == symconst_addr_ent) {
      entity *ent = get_SymConst_entity(node);
      assert(ent && is_Method_type(get_entity_type(ent)));
      eset_insert(methods, ent);
    } else {
      assert(get_SymConst_kind(node) == symconst_addr_name);
      /* externe Methode (wegen fix_symconst!) */
      eset_insert(methods, MARK); /* free method -> unknown */
    }
    break;
  case iro_Sel:
    /* polymorphe Methode */
    for (i = get_Sel_n_methods(node) - 1; i >= 0; --i) {
      entity * ent = get_Sel_method(node, i);
      if (ent) {
        eset_insert(methods, ent);
      } else {
        eset_insert(methods, MARK);
      }
    }
    break;

  case iro_Bad:
    /* nothing */
    break;

  case iro_Phi:
    for (i = get_Phi_n_preds(node) - 1; i >= 0; --i) {
      callee_ana_node(get_Phi_pred(node, i), methods);
    }
    break;

  case iro_Mux:
    callee_ana_node(get_Mux_false(node), methods);
    callee_ana_node(get_Mux_true(node), methods);
    break;

  case iro_Psi:
    for (i = get_Psi_n_conds(node) - 1; i >= 0; --i) {
      callee_ana_node(get_Psi_val(node, i), methods);
    }
    callee_ana_node(get_Psi_default(node), methods);
    break;

  case iro_Id:
    callee_ana_node(get_Id_pred(node), methods);
    break;

  case iro_Proj:
    callee_ana_proj(get_Proj_pred(node), get_Proj_proj(node), methods);
    break;

  case iro_Add:
  case iro_Sub:
  case iro_Conv:
    /* extern */
    eset_insert(methods, MARK); /* free method -> unknown */
    break;

  default:
    assert(0 && "invalid opcode or opcode not implemented");
    break;
  }

  set_irn_link(node, NULL);
}

/**
 * Walker: Analyses every call node and calculates an array of possible
 * callees for that call.
 */
static void callee_walker(ir_node * call, void * env) {
  if (is_Call(call)) {
    eset * methods = eset_create();
    entity * ent;
    entity ** arr = NEW_ARR_F(entity *, 0);
    assert(get_irn_op(get_Call_ptr(call)) != op_Id);
    callee_ana_node(get_Call_ptr(call), methods);
    if (eset_contains(methods, MARK)) { /* unknown method */
      ARR_APP1(entity *, arr, unknown_entity);
    }
    for (ent = eset_first(methods); ent; ent = eset_next(methods)) {
      if (ent != MARK) {
        ARR_APP1(entity *, arr, ent);
      }
    }
#if 0  /* This generates Bad nodes when we don't want it.
          Call it with a check for valid cgana information in local_optimize. */
    if (ARR_LEN(arr) == 0 && get_opt_optimize() && get_opt_closed_world() && get_opt_dyn_meth_dispatch()) {
      /* Kann vorkommen, wenn der Vorgnger beispielsweise eine
       * Sel-Operation war, die keine Methoden zurckgeben
       * konnte. Wir ersetzen die Call-Operation ebenfalls durch
       * eine Bad-Operation. Die Verlinkung muss wiederhergestellt
       * werden! */
      ir_node *mem = get_Call_mem(call);
      turn_into_tuple (call, 5 /* pn_Call_max */);
      set_Tuple_pred(call, pn_Call_M_regular       , mem);
      set_Tuple_pred(call, pn_Call_T_result        , new_Bad());
      set_Tuple_pred(call, pn_Call_P_value_res_base, new_Bad());
      set_Tuple_pred(call, pn_Call_X_except        , new_Bad());  /* new_Jmp() ?? new_Raise() ?? */
      set_Tuple_pred(call, pn_Call_M_except        , new_Bad());

    } else
#endif
    {
      set_Call_callee_arr(call, ARR_LEN(arr), arr);
    }
    DEL_ARR_F(arr);
    eset_destroy(methods);
  }
}

/**
 * Walker: Removes all tuple.
 */
static void remove_Tuples(ir_node *proj, void *env) {
  ir_node *nn;
  if (! is_Proj(proj)) return;

  nn = skip_Tuple(proj);
  if (nn != proj) exchange(proj, nn);
}


/* Bestimmt fr jede Call-Operation die Menge der aufrufbaren Methode
 * und speichert das Ergebnis in der Call-Operation. (siehe
 * "set_Call_callee"). "sel_methods" wird fr den Aufbau bentigt und
 * muss bereits aufgebaut sein. */
static void callee_ana(void) {
  int i;
  /* Alle Graphen analysieren. */
  for (i = get_irp_n_irgs() - 1; i >= 0; --i) {
    ir_graph *irg = get_irp_irg(i);
    irg_walk_graph(irg, callee_walker, remove_Tuples, NULL);
    set_irg_callee_info_state(irg, irg_callee_info_consistent);
  }
  set_irp_callee_info_state(irg_callee_info_consistent);
}

/*--------------------------------------------------------------------------*/
/* Cleanup after analyses.                                                  */
/*--------------------------------------------------------------------------*/

/** Frees intermediate data structures. */
static void sel_methods_dispose(void) {
  entity * ent;
  assert(entities);
  for (ent = eset_first(entities); ent; ent = eset_next(entities)) {
    entity ** arr = get_entity_link(ent);
    if (arr) {
      DEL_ARR_F(arr);
    }
    set_entity_link(ent, NULL);
  }
  eset_destroy(entities);
  entities = NULL;
}

/*--------------------------------------------------------------------------*/
/* Freeing the callee arrays.                                               */
/*--------------------------------------------------------------------------*/

static void destruct_walker(ir_node * node, void * env) {
  if (is_Call(node)) {
    remove_Call_callee_arr(node);
  }
}

/*--------------------------------------------------------------------------*/
/* Main drivers.                                                            */
/*--------------------------------------------------------------------------*/

void cgana(int *length, entity ***free_methods) {
  entity ** free_meths, **p;

  /* Optimize Sel/SymConst nodes and compute all methods that implement an entity. */
  sel_methods_init();
  free_meths = get_free_methods();
  callee_ana();
  sel_methods_dispose();

  /* Convert the flexible array to an array that can be handled
     by standard C. */
  p = xmalloc(sizeof(*p) * ARR_LEN(free_meths));
  memcpy(p, free_meths, ARR_LEN(free_meths) * sizeof(*p));

  *length       = ARR_LEN(free_meths);
  *free_methods = p;

  DEL_ARR_F(free_meths);
}

void free_callee_info(ir_graph *irg) {
  irg_walk_graph(irg, destruct_walker, NULL, NULL);
  set_irg_callee_info_state(irg, irg_callee_info_none);
}

void free_irp_callee_info(void) {
  int i;
  for (i = get_irp_n_irgs() - 1; i >= 0; --i) {
    free_callee_info(get_irp_irg(i));
  }
}

/* Optimize the address expressions passed to call nodes.
 *
 * This optimization performs the following transformations for
 * all ir graphs:
 * - All SymConst operations that refer to intern methods are replaced
 *   by Const operations referring to the corresponding entity.
 * - Sel nodes, that select entities that are not overwritten are
 *   replaced by Const nodes referring to the selected entity.
 * - Sel nodes, for which no method exists at all are replaced by Bad
 *   nodes.
 * - Sel nodes with a pointer input that is an Alloc node are replaced
 *   by Const nodes referring to the entity that implements the method in
 *   the type given by the Alloc node.
 */
void opt_call_addrs(void) {
  sel_methods_init();
  sel_methods_dispose();
}