[pf3gnuchains/gcc-fork.git] / gcc / tree-ssa-structalias.c

/* Tree based points-to analysis
   Copyright (C) 2005, 2006, 2007 Free Software Foundation, Inc.
   Contributed by Daniel Berlin <dberlin@dberlin.org>

   This file is part of GCC.

   GCC is free software; you can redistribute it and/or modify
   under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, 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 "tm.h"
#include "ggc.h"
#include "obstack.h"
#include "bitmap.h"
#include "flags.h"
#include "rtl.h"
#include "tm_p.h"
#include "hard-reg-set.h"
#include "basic-block.h"
#include "output.h"
#include "errors.h"
#include "diagnostic.h"
#include "tree.h"
#include "c-common.h"
#include "tree-flow.h"
#include "tree-inline.h"
#include "varray.h"
#include "c-tree.h"
#include "tree-gimple.h"
#include "hashtab.h"
#include "function.h"
#include "cgraph.h"
#include "tree-pass.h"
#include "timevar.h"
#include "alloc-pool.h"
#include "splay-tree.h"
#include "params.h"
#include "tree-ssa-structalias.h"
#include "cgraph.h"
#include "alias.h"
#include "pointer-set.h"

/* The idea behind this analyzer is to generate set constraints from the
   program, then solve the resulting constraints in order to generate the
   points-to sets.

   Set constraints are a way of modeling program analysis problems that
   involve sets.  They consist of an inclusion constraint language,
   describing the variables (each variable is a set) and operations that
   are involved on the variables, and a set of rules that derive facts
   from these operations.  To solve a system of set constraints, you derive
   all possible facts under the rules, which gives you the correct sets
   as a consequence.

   See  "Efficient Field-sensitive pointer analysis for C" by "David
   J. Pearce and Paul H. J. Kelly and Chris Hankin, at
   http://citeseer.ist.psu.edu/pearce04efficient.html

   Also see "Ultra-fast Aliasing Analysis using CLA: A Million Lines
   of C Code in a Second" by ""Nevin Heintze and Olivier Tardieu" at
   http://citeseer.ist.psu.edu/heintze01ultrafast.html

   There are three types of real constraint expressions, DEREF,
   ADDRESSOF, and SCALAR.  Each constraint expression consists
   of a constraint type, a variable, and an offset.

   SCALAR is a constraint expression type used to represent x, whether
   it appears on the LHS or the RHS of a statement.
   DEREF is a constraint expression type used to represent *x, whether
   it appears on the LHS or the RHS of a statement.
   ADDRESSOF is a constraint expression used to represent &x, whether
   it appears on the LHS or the RHS of a statement.

   Each pointer variable in the program is assigned an integer id, and
   each field of a structure variable is assigned an integer id as well.

   Structure variables are linked to their list of fields through a "next
   field" in each variable that points to the next field in offset
   order.
   Each variable for a structure field has

   1. "size", that tells the size in bits of that field.
   2. "fullsize, that tells the size in bits of the entire structure.
   3. "offset", that tells the offset in bits from the beginning of the
   structure to this field.

   Thus,
   struct f
   {
     int a;
     int b;
   } foo;
   int *bar;

   looks like

   foo.a -> id 1, size 32, offset 0, fullsize 64, next foo.b
   foo.b -> id 2, size 32, offset 32, fullsize 64, next NULL
   bar -> id 3, size 32, offset 0, fullsize 32, next NULL


  In order to solve the system of set constraints, the following is
  done:

  1. Each constraint variable x has a solution set associated with it,
  Sol(x).

  2. Constraints are separated into direct, copy, and complex.
  Direct constraints are ADDRESSOF constraints that require no extra
  processing, such as P = &Q
  Copy constraints are those of the form P = Q.
  Complex constraints are all the constraints involving dereferences
  and offsets (including offsetted copies).

  3. All direct constraints of the form P = &Q are processed, such
  that Q is added to Sol(P)

  4. All complex constraints for a given constraint variable are stored in a
  linked list attached to that variable's node.

  5. A directed graph is built out of the copy constraints. Each
  constraint variable is a node in the graph, and an edge from
  Q to P is added for each copy constraint of the form P = Q

  6. The graph is then walked, and solution sets are
  propagated along the copy edges, such that an edge from Q to P
  causes Sol(P) <- Sol(P) union Sol(Q).

  7.  As we visit each node, all complex constraints associated with
  that node are processed by adding appropriate copy edges to the graph, or the
  appropriate variables to the solution set.

  8. The process of walking the graph is iterated until no solution
  sets change.

  Prior to walking the graph in steps 6 and 7, We perform static
  cycle elimination on the constraint graph, as well
  as off-line variable substitution.

  TODO: Adding offsets to pointer-to-structures can be handled (IE not punted
  on and turned into anything), but isn't.  You can just see what offset
  inside the pointed-to struct it's going to access.

  TODO: Constant bounded arrays can be handled as if they were structs of the
  same number of elements.

  TODO: Modeling heap and incoming pointers becomes much better if we
  add fields to them as we discover them, which we could do.

  TODO: We could handle unions, but to be honest, it's probably not
  worth the pain or slowdown.  */

static GTY ((if_marked ("tree_map_marked_p"), param_is (struct tree_map)))
htab_t heapvar_for_stmt;

static bool use_field_sensitive = true;
static int in_ipa_mode = 0;

/* Used for predecessor bitmaps. */
static bitmap_obstack predbitmap_obstack;

/* Used for points-to sets.  */
static bitmap_obstack pta_obstack;

/* Used for oldsolution members of variables. */
static bitmap_obstack oldpta_obstack;

/* Used for per-solver-iteration bitmaps.  */
static bitmap_obstack iteration_obstack;

static unsigned int create_variable_info_for (tree, const char *);
typedef struct constraint_graph *constraint_graph_t;
static void unify_nodes (constraint_graph_t, unsigned int, unsigned int, bool);

DEF_VEC_P(constraint_t);
DEF_VEC_ALLOC_P(constraint_t,heap);

#define EXECUTE_IF_IN_NONNULL_BITMAP(a, b, c, d)        \
  if (a)                                                \
    EXECUTE_IF_SET_IN_BITMAP (a, b, c, d)

static struct constraint_stats
{
  unsigned int total_vars;
  unsigned int nonpointer_vars;
  unsigned int unified_vars_static;
  unsigned int unified_vars_dynamic;
  unsigned int iterations;
  unsigned int num_edges;
  unsigned int num_implicit_edges;
  unsigned int points_to_sets_created;
} stats;

struct variable_info
{
  /* ID of this variable  */
  unsigned int id;

  /* Name of this variable */
  const char *name;

  /* Tree that this variable is associated with.  */
  tree decl;

  /* Offset of this variable, in bits, from the base variable  */
  unsigned HOST_WIDE_INT offset;

  /* Size of the variable, in bits.  */
  unsigned HOST_WIDE_INT size;

  /* Full size of the base variable, in bits.  */
  unsigned HOST_WIDE_INT fullsize;

  /* A link to the variable for the next field in this structure.  */
  struct variable_info *next;

  /* True if the variable is directly the target of a dereference.
     This is used to track which variables are *actually* dereferenced
     so we can prune their points to listed. */
  unsigned int directly_dereferenced:1;

  /* True if this is a variable created by the constraint analysis, such as
     heap variables and constraints we had to break up.  */
  unsigned int is_artificial_var:1;

  /* True if this is a special variable whose solution set should not be
     changed.  */
  unsigned int is_special_var:1;

  /* True for variables whose size is not known or variable.  */
  unsigned int is_unknown_size_var:1;

  /* True for variables that have unions somewhere in them.  */
  unsigned int has_union:1;

  /* True if this is a heap variable.  */
  unsigned int is_heap_var:1;

  /* True if we may not use TBAA to prune references to this
     variable.  This is used for C++ placement new.  */
  unsigned int no_tbaa_pruning : 1;

  /* True if this variable is inside a structure nested in the
     structure for the base variable.  For instance, in 
     struct X { int a; struct Y { int b; int c; } }, the variables for
     fields 'b' and 'c' are inside a nested structure.  We are not
     interested in tracking how many levels of nesting, just whether
     there is nesting at all.  This is later used to adjust offsets
     for pointers pointing into sub-structures.  */
  unsigned int in_nested_struct : 1;

  /* Points-to set for this variable.  */
  bitmap solution;

  /* Old points-to set for this variable.  */
  bitmap oldsolution;

  /* Variable id this was collapsed to due to type unsafety.  This
     should be unused completely after build_succ_graph, or something
     is broken.  */
  struct variable_info *collapsed_to;
};
typedef struct variable_info *varinfo_t;

static varinfo_t first_vi_for_offset (varinfo_t, unsigned HOST_WIDE_INT);

/* Pool of variable info structures.  */
static alloc_pool variable_info_pool;

DEF_VEC_P(varinfo_t);

DEF_VEC_ALLOC_P(varinfo_t, heap);

/* Table of variable info structures for constraint variables.
   Indexed directly by variable info id.  */
static VEC(varinfo_t,heap) *varmap;

/* Return the varmap element N */

static inline varinfo_t
get_varinfo (unsigned int n)
{
  return VEC_index (varinfo_t, varmap, n);
}

/* Return the varmap element N, following the collapsed_to link.  */

static inline varinfo_t
get_varinfo_fc (unsigned int n)
{
  varinfo_t v = VEC_index (varinfo_t, varmap, n);

  if (v->collapsed_to)
    return v->collapsed_to;
  return v;
}

/* Variable that represents the unknown pointer.  */
static varinfo_t var_anything;
static tree anything_tree;
static unsigned int anything_id;

/* Variable that represents the NULL pointer.  */
static varinfo_t var_nothing;
static tree nothing_tree;
static unsigned int nothing_id;

/* Variable that represents read only memory.  */
static varinfo_t var_readonly;
static tree readonly_tree;
static unsigned int readonly_id;

/* Variable that represents integers.  This is used for when people do things
   like &0->a.b.  */
static varinfo_t var_integer;
static tree integer_tree;
static unsigned int integer_id;

/* Lookup a heap var for FROM, and return it if we find one.  */

static tree
heapvar_lookup (tree from)
{
  struct tree_map *h, in;
  in.base.from = from;

  h = (struct tree_map *) htab_find_with_hash (heapvar_for_stmt, &in,
                                               htab_hash_pointer (from));
  if (h)
    return h->to;
  return NULL_TREE;
}

/* Insert a mapping FROM->TO in the heap var for statement
   hashtable.  */

static void
heapvar_insert (tree from, tree to)
{
  struct tree_map *h;
  void **loc;

  h = GGC_NEW (struct tree_map);
  h->hash = htab_hash_pointer (from);
  h->base.from = from;
  h->to = to;
  loc = htab_find_slot_with_hash (heapvar_for_stmt, h, h->hash, INSERT);
  *(struct tree_map **) loc = h;
}

/* Return a new variable info structure consisting for a variable
   named NAME, and using constraint graph node NODE.  */

static varinfo_t
new_var_info (tree t, unsigned int id, const char *name)
{
  varinfo_t ret = (varinfo_t) pool_alloc (variable_info_pool);
  tree var;

  ret->id = id;
  ret->name = name;
  ret->decl = t;
  ret->directly_dereferenced = false;
  ret->is_artificial_var = false;
  ret->is_heap_var = false;
  ret->is_special_var = false;
  ret->is_unknown_size_var = false;
  ret->has_union = false;
  var = t;
  if (TREE_CODE (var) == SSA_NAME)
    var = SSA_NAME_VAR (var);
  ret->no_tbaa_pruning = (DECL_P (var)
                          && POINTER_TYPE_P (TREE_TYPE (var))
                          && DECL_NO_TBAA_P (var));
  ret->solution = BITMAP_ALLOC (&pta_obstack);
  ret->oldsolution = BITMAP_ALLOC (&oldpta_obstack);
  ret->next = NULL;
  ret->collapsed_to = NULL;
  return ret;
}

typedef enum {SCALAR, DEREF, ADDRESSOF} constraint_expr_type;

/* An expression that appears in a constraint.  */

struct constraint_expr
{
  /* Constraint type.  */
  constraint_expr_type type;

  /* Variable we are referring to in the constraint.  */
  unsigned int var;

  /* Offset, in bits, of this constraint from the beginning of
     variables it ends up referring to.

     IOW, in a deref constraint, we would deref, get the result set,
     then add OFFSET to each member.   */
  unsigned HOST_WIDE_INT offset;
};

typedef struct constraint_expr ce_s;
DEF_VEC_O(ce_s);
DEF_VEC_ALLOC_O(ce_s, heap);
static void get_constraint_for (tree, VEC(ce_s, heap) **);
static void do_deref (VEC (ce_s, heap) **);

/* Our set constraints are made up of two constraint expressions, one
   LHS, and one RHS.

   As described in the introduction, our set constraints each represent an
   operation between set valued variables.
*/
struct constraint
{
  struct constraint_expr lhs;
  struct constraint_expr rhs;
};

/* List of constraints that we use to build the constraint graph from.  */

static VEC(constraint_t,heap) *constraints;
static alloc_pool constraint_pool;


DEF_VEC_I(int);
DEF_VEC_ALLOC_I(int, heap);

/* The constraint graph is represented as an array of bitmaps
   containing successor nodes.  */

struct constraint_graph
{
  /* Size of this graph, which may be different than the number of
     nodes in the variable map.  */
  unsigned int size;

  /* Explicit successors of each node. */
  bitmap *succs;

  /* Implicit predecessors of each node (Used for variable
     substitution). */
  bitmap *implicit_preds;

  /* Explicit predecessors of each node (Used for variable substitution).  */
  bitmap *preds;

  /* Indirect cycle representatives, or -1 if the node has no indirect
     cycles.  */
  int *indirect_cycles;

  /* Representative node for a node.  rep[a] == a unless the node has
     been unified. */
  unsigned int *rep;

  /* Equivalence class representative for a label.  This is used for
     variable substitution.  */
  int *eq_rep;

  /* Pointer equivalence label for a node.  All nodes with the same
     pointer equivalence label can be unified together at some point
     (either during constraint optimization or after the constraint
     graph is built).  */
  unsigned int *pe;

  /* Pointer equivalence representative for a label.  This is used to
     handle nodes that are pointer equivalent but not location
     equivalent.  We can unite these once the addressof constraints
     are transformed into initial points-to sets.  */
  int *pe_rep;

  /* Pointer equivalence label for each node, used during variable
     substitution.  */
  unsigned int *pointer_label;

  /* Location equivalence label for each node, used during location
     equivalence finding.  */
  unsigned int *loc_label;

  /* Pointed-by set for each node, used during location equivalence
     finding.  This is pointed-by rather than pointed-to, because it
     is constructed using the predecessor graph.  */
  bitmap *pointed_by;

  /* Points to sets for pointer equivalence.  This is *not* the actual
     points-to sets for nodes.  */
  bitmap *points_to;

  /* Bitmap of nodes where the bit is set if the node is a direct
     node.  Used for variable substitution.  */
  sbitmap direct_nodes;

  /* Bitmap of nodes where the bit is set if the node is address
     taken.  Used for variable substitution.  */
  bitmap address_taken;

  /* True if points_to bitmap for this node is stored in the hash
     table.  */
  sbitmap pt_used;

  /* Number of incoming edges remaining to be processed by pointer
     equivalence.
     Used for variable substitution.  */
  unsigned int *number_incoming;


  /* Vector of complex constraints for each graph node.  Complex
     constraints are those involving dereferences or offsets that are
     not 0.  */
  VEC(constraint_t,heap) **complex;
};

static constraint_graph_t graph;

/* During variable substitution and the offline version of indirect
   cycle finding, we create nodes to represent dereferences and
   address taken constraints.  These represent where these start and
   end.  */
#define FIRST_REF_NODE (VEC_length (varinfo_t, varmap))
#define LAST_REF_NODE (FIRST_REF_NODE + (FIRST_REF_NODE - 1))

/* Return the representative node for NODE, if NODE has been unioned
   with another NODE.
   This function performs path compression along the way to finding
   the representative.  */

static unsigned int
find (unsigned int node)
{
  gcc_assert (node < graph->size);
  if (graph->rep[node] != node)
    return graph->rep[node] = find (graph->rep[node]);
  return node;
}

/* Union the TO and FROM nodes to the TO nodes.
   Note that at some point in the future, we may want to do
   union-by-rank, in which case we are going to have to return the
   node we unified to.  */

static bool
unite (unsigned int to, unsigned int from)
{
  gcc_assert (to < graph->size && from < graph->size);
  if (to != from && graph->rep[from] != to)
    {
      graph->rep[from] = to;
      return true;
    }
  return false;
}

/* Create a new constraint consisting of LHS and RHS expressions.  */

static constraint_t
new_constraint (const struct constraint_expr lhs,
                const struct constraint_expr rhs)
{
  constraint_t ret = (constraint_t) pool_alloc (constraint_pool);
  ret->lhs = lhs;
  ret->rhs = rhs;
  return ret;
}

/* Print out constraint C to FILE.  */

void
dump_constraint (FILE *file, constraint_t c)
{
  if (c->lhs.type == ADDRESSOF)
    fprintf (file, "&");
  else if (c->lhs.type == DEREF)
    fprintf (file, "*");
  fprintf (file, "%s", get_varinfo_fc (c->lhs.var)->name);
  if (c->lhs.offset != 0)
    fprintf (file, " + " HOST_WIDE_INT_PRINT_DEC, c->lhs.offset);
  fprintf (file, " = ");
  if (c->rhs.type == ADDRESSOF)
    fprintf (file, "&");
  else if (c->rhs.type == DEREF)
    fprintf (file, "*");
  fprintf (file, "%s", get_varinfo_fc (c->rhs.var)->name);
  if (c->rhs.offset != 0)
    fprintf (file, " + " HOST_WIDE_INT_PRINT_DEC, c->rhs.offset);
  fprintf (file, "\n");
}

/* Print out constraint C to stderr.  */

void
debug_constraint (constraint_t c)
{
  dump_constraint (stderr, c);
}

/* Print out all constraints to FILE */

void
dump_constraints (FILE *file)
{
  int i;
  constraint_t c;
  for (i = 0; VEC_iterate (constraint_t, constraints, i, c); i++)
    dump_constraint (file, c);
}

/* Print out all constraints to stderr.  */

void
debug_constraints (void)
{
  dump_constraints (stderr);
}

/* SOLVER FUNCTIONS

   The solver is a simple worklist solver, that works on the following
   algorithm:

   sbitmap changed_nodes = all zeroes;
   changed_count = 0;
   For each node that is not already collapsed:
       changed_count++;
       set bit in changed nodes

   while (changed_count > 0)
   {
     compute topological ordering for constraint graph

     find and collapse cycles in the constraint graph (updating
     changed if necessary)

     for each node (n) in the graph in topological order:
       changed_count--;

       Process each complex constraint associated with the node,
       updating changed if necessary.

       For each outgoing edge from n, propagate the solution from n to
       the destination of the edge, updating changed as necessary.

   }  */

/* Return true if two constraint expressions A and B are equal.  */

static bool
constraint_expr_equal (struct constraint_expr a, struct constraint_expr b)
{
  return a.type == b.type && a.var == b.var && a.offset == b.offset;
}

/* Return true if constraint expression A is less than constraint expression
   B.  This is just arbitrary, but consistent, in order to give them an
   ordering.  */

static bool
constraint_expr_less (struct constraint_expr a, struct constraint_expr b)
{
  if (a.type == b.type)
    {
      if (a.var == b.var)
        return a.offset < b.offset;
      else
        return a.var < b.var;
    }
  else
    return a.type < b.type;
}

/* Return true if constraint A is less than constraint B.  This is just
   arbitrary, but consistent, in order to give them an ordering.  */

static bool
constraint_less (const constraint_t a, const constraint_t b)
{
  if (constraint_expr_less (a->lhs, b->lhs))
    return true;
  else if (constraint_expr_less (b->lhs, a->lhs))
    return false;
  else
    return constraint_expr_less (a->rhs, b->rhs);
}

/* Return true if two constraints A and B are equal.  */

static bool
constraint_equal (struct constraint a, struct constraint b)
{
  return constraint_expr_equal (a.lhs, b.lhs)
    && constraint_expr_equal (a.rhs, b.rhs);
}


/* Find a constraint LOOKFOR in the sorted constraint vector VEC */

static constraint_t
constraint_vec_find (VEC(constraint_t,heap) *vec,
                     struct constraint lookfor)
{
  unsigned int place;
  constraint_t found;

  if (vec == NULL)
    return NULL;

  place = VEC_lower_bound (constraint_t, vec, &lookfor, constraint_less);
  if (place >= VEC_length (constraint_t, vec))
    return NULL;
  found = VEC_index (constraint_t, vec, place);
  if (!constraint_equal (*found, lookfor))
    return NULL;
  return found;
}

/* Union two constraint vectors, TO and FROM.  Put the result in TO.  */

static void
constraint_set_union (VEC(constraint_t,heap) **to,
                      VEC(constraint_t,heap) **from)
{
  int i;
  constraint_t c;

  for (i = 0; VEC_iterate (constraint_t, *from, i, c); i++)
    {
      if (constraint_vec_find (*to, *c) == NULL)
        {
          unsigned int place = VEC_lower_bound (constraint_t, *to, c,
                                                constraint_less);
          VEC_safe_insert (constraint_t, heap, *to, place, c);
        }
    }
}

/* Take a solution set SET, add OFFSET to each member of the set, and
   overwrite SET with the result when done.  */

static void
solution_set_add (bitmap set, unsigned HOST_WIDE_INT offset)
{
  bitmap result = BITMAP_ALLOC (&iteration_obstack);
  unsigned int i;
  bitmap_iterator bi;

  EXECUTE_IF_SET_IN_BITMAP (set, 0, i, bi)
    {
      /* If this is a properly sized variable, only add offset if it's
         less than end.  Otherwise, it is globbed to a single
         variable.  */

      if ((get_varinfo (i)->offset + offset) < get_varinfo (i)->fullsize)
        {
          unsigned HOST_WIDE_INT fieldoffset = get_varinfo (i)->offset + offset;
          varinfo_t v = first_vi_for_offset (get_varinfo (i), fieldoffset);
          if (!v)
            continue;
          bitmap_set_bit (result, v->id);
        }
      else if (get_varinfo (i)->is_artificial_var
               || get_varinfo (i)->has_union
               || get_varinfo (i)->is_unknown_size_var)
        {
          bitmap_set_bit (result, i);
        }
    }

  bitmap_copy (set, result);
  BITMAP_FREE (result);
}

/* Union solution sets TO and FROM, and add INC to each member of FROM in the
   process.  */

static bool
set_union_with_increment  (bitmap to, bitmap from, unsigned HOST_WIDE_INT inc)
{
  if (inc == 0)
    return bitmap_ior_into (to, from);
  else
    {
      bitmap tmp;
      bool res;

      tmp = BITMAP_ALLOC (&iteration_obstack);
      bitmap_copy (tmp, from);
      solution_set_add (tmp, inc);
      res = bitmap_ior_into (to, tmp);
      BITMAP_FREE (tmp);
      return res;
    }
}

/* Insert constraint C into the list of complex constraints for graph
   node VAR.  */

static void
insert_into_complex (constraint_graph_t graph,
                     unsigned int var, constraint_t c)
{
  VEC (constraint_t, heap) *complex = graph->complex[var];
  unsigned int place = VEC_lower_bound (constraint_t, complex, c,
                                        constraint_less);

  /* Only insert constraints that do not already exist.  */
  if (place >= VEC_length (constraint_t, complex)
      || !constraint_equal (*c, *VEC_index (constraint_t, complex, place)))
    VEC_safe_insert (constraint_t, heap, graph->complex[var], place, c);
}


/* Condense two variable nodes into a single variable node, by moving
   all associated info from SRC to TO.  */

static void
merge_node_constraints (constraint_graph_t graph, unsigned int to,
                        unsigned int from)
{
  unsigned int i;
  constraint_t c;

  gcc_assert (find (from) == to);

  /* Move all complex constraints from src node into to node  */
  for (i = 0; VEC_iterate (constraint_t, graph->complex[from], i, c); i++)
    {
      /* In complex constraints for node src, we may have either
         a = *src, and *src = a, or an offseted constraint which are
         always added to the rhs node's constraints.  */

      if (c->rhs.type == DEREF)
        c->rhs.var = to;
      else if (c->lhs.type == DEREF)
        c->lhs.var = to;
      else
        c->rhs.var = to;
    }
  constraint_set_union (&graph->complex[to], &graph->complex[from]);
  VEC_free (constraint_t, heap, graph->complex[from]);
  graph->complex[from] = NULL;
}


/* Remove edges involving NODE from GRAPH.  */

static void
clear_edges_for_node (constraint_graph_t graph, unsigned int node)
{
  if (graph->succs[node])
    BITMAP_FREE (graph->succs[node]);
}

/* Merge GRAPH nodes FROM and TO into node TO.  */

static void
merge_graph_nodes (constraint_graph_t graph, unsigned int to,
                   unsigned int from)
{
  if (graph->indirect_cycles[from] != -1)
    {
      /* If we have indirect cycles with the from node, and we have
         none on the to node, the to node has indirect cycles from the
         from node now that they are unified.
         If indirect cycles exist on both, unify the nodes that they
         are in a cycle with, since we know they are in a cycle with
         each other.  */
      if (graph->indirect_cycles[to] == -1)
        graph->indirect_cycles[to] = graph->indirect_cycles[from];
    }

  /* Merge all the successor edges.  */
  if (graph->succs[from])
    {
      if (!graph->succs[to])
        graph->succs[to] = BITMAP_ALLOC (&pta_obstack);
      bitmap_ior_into (graph->succs[to],
                       graph->succs[from]);
    }

  clear_edges_for_node (graph, from);
}


/* Add an indirect graph edge to GRAPH, going from TO to FROM if
   it doesn't exist in the graph already.  */

static void
add_implicit_graph_edge (constraint_graph_t graph, unsigned int to,
                         unsigned int from)
{
  if (to == from)
    return;

  if (!graph->implicit_preds[to])
    graph->implicit_preds[to] = BITMAP_ALLOC (&predbitmap_obstack);

  if (!bitmap_bit_p (graph->implicit_preds[to], from))
    {
      stats.num_implicit_edges++;
      bitmap_set_bit (graph->implicit_preds[to], from);
    }
}

/* Add a predecessor graph edge to GRAPH, going from TO to FROM if
   it doesn't exist in the graph already.
   Return false if the edge already existed, true otherwise.  */

static void
add_pred_graph_edge (constraint_graph_t graph, unsigned int to,
                     unsigned int from)
{
  if (!graph->preds[to])
    graph->preds[to] = BITMAP_ALLOC (&predbitmap_obstack);
  if (!bitmap_bit_p (graph->preds[to], from))
    bitmap_set_bit (graph->preds[to], from);
}

/* Add a graph edge to GRAPH, going from FROM to TO if
   it doesn't exist in the graph already.
   Return false if the edge already existed, true otherwise.  */

static bool
add_graph_edge (constraint_graph_t graph, unsigned int to,
                unsigned int from)
{
  if (to == from)
    {
      return false;
    }
  else
    {
      bool r = false;

      if (!graph->succs[from])
        graph->succs[from] = BITMAP_ALLOC (&pta_obstack);
      if (!bitmap_bit_p (graph->succs[from], to))
        {
          r = true;
          if (to < FIRST_REF_NODE && from < FIRST_REF_NODE)
            stats.num_edges++;
          bitmap_set_bit (graph->succs[from], to);
        }
      return r;
    }
}


/* Return true if {DEST.SRC} is an existing graph edge in GRAPH.  */

static bool
valid_graph_edge (constraint_graph_t graph, unsigned int src,
                  unsigned int dest)
{
  return (graph->succs[dest]
          && bitmap_bit_p (graph->succs[dest], src));
}

/* Initialize the constraint graph structure to contain SIZE nodes.  */

static void
init_graph (unsigned int size)
{
  unsigned int j;

  graph = XCNEW (struct constraint_graph);
  graph->size = size;
  graph->succs = XCNEWVEC (bitmap, graph->size);
  graph->indirect_cycles = XNEWVEC (int, graph->size);
  graph->rep = XNEWVEC (unsigned int, graph->size);
  graph->complex = XCNEWVEC (VEC(constraint_t, heap) *, size);
  graph->pe = XCNEWVEC (unsigned int, graph->size);
  graph->pe_rep = XNEWVEC (int, graph->size);

  for (j = 0; j < graph->size; j++)
    {
      graph->rep[j] = j;
      graph->pe_rep[j] = -1;
      graph->indirect_cycles[j] = -1;
    }
}

/* Build the constraint graph, adding only predecessor edges right now.  */

static void
build_pred_graph (void)
{
  int i;
  constraint_t c;
  unsigned int j;

  graph->implicit_preds = XCNEWVEC (bitmap, graph->size);
  graph->preds = XCNEWVEC (bitmap, graph->size);
  graph->pointer_label = XCNEWVEC (unsigned int, graph->size);
  graph->loc_label = XCNEWVEC (unsigned int, graph->size);
  graph->pointed_by = XCNEWVEC (bitmap, graph->size);
  graph->points_to = XCNEWVEC (bitmap, graph->size);
  graph->eq_rep = XNEWVEC (int, graph->size);
  graph->direct_nodes = sbitmap_alloc (graph->size);
  graph->pt_used = sbitmap_alloc (graph->size);
  graph->address_taken = BITMAP_ALLOC (&predbitmap_obstack);
  graph->number_incoming = XCNEWVEC (unsigned int, graph->size);
  sbitmap_zero (graph->direct_nodes);
  sbitmap_zero (graph->pt_used);

  for (j = 0; j < FIRST_REF_NODE; j++)
    {
      if (!get_varinfo (j)->is_special_var)
        SET_BIT (graph->direct_nodes, j);
    }

  for (j = 0; j < graph->size; j++)
    graph->eq_rep[j] = -1;

  for (j = 0; j < VEC_length (varinfo_t, varmap); j++)
    graph->indirect_cycles[j] = -1;

  for (i = 0; VEC_iterate (constraint_t, constraints, i, c); i++)
    {
      struct constraint_expr lhs = c->lhs;
      struct constraint_expr rhs = c->rhs;
      unsigned int lhsvar = get_varinfo_fc (lhs.var)->id;
      unsigned int rhsvar = get_varinfo_fc (rhs.var)->id;

      if (lhs.type == DEREF)
        {
          /* *x = y.  */
          if (rhs.offset == 0 && lhs.offset == 0 && rhs.type == SCALAR)
            add_pred_graph_edge (graph, FIRST_REF_NODE + lhsvar, rhsvar);
        }
      else if (rhs.type == DEREF)
        {
          /* x = *y */
          if (rhs.offset == 0 && lhs.offset == 0 && lhs.type == SCALAR)
            add_pred_graph_edge (graph, lhsvar, FIRST_REF_NODE + rhsvar);
          else
            RESET_BIT (graph->direct_nodes, lhsvar);
        }
      else if (rhs.type == ADDRESSOF)
        {
          /* x = &y */
          if (graph->points_to[lhsvar] == NULL)
            graph->points_to[lhsvar] = BITMAP_ALLOC (&predbitmap_obstack);
          bitmap_set_bit (graph->points_to[lhsvar], rhsvar);

          if (graph->pointed_by[rhsvar] == NULL)
            graph->pointed_by[rhsvar] = BITMAP_ALLOC (&predbitmap_obstack);
          bitmap_set_bit (graph->pointed_by[rhsvar], lhsvar);

          /* Implicitly, *x = y */
          add_implicit_graph_edge (graph, FIRST_REF_NODE + lhsvar, rhsvar);

          RESET_BIT (graph->direct_nodes, rhsvar);
          bitmap_set_bit (graph->address_taken, rhsvar);
        }
      else if (lhsvar > anything_id
               && lhsvar != rhsvar && lhs.offset == 0 && rhs.offset == 0)
        {
          /* x = y */
          add_pred_graph_edge (graph, lhsvar, rhsvar);
          /* Implicitly, *x = *y */
          add_implicit_graph_edge (graph, FIRST_REF_NODE + lhsvar,
                                   FIRST_REF_NODE + rhsvar);
        }
      else if (lhs.offset != 0 || rhs.offset != 0)
        {
          if (rhs.offset != 0)
            RESET_BIT (graph->direct_nodes, lhs.var);
          else if (lhs.offset != 0)
            RESET_BIT (graph->direct_nodes, rhs.var);
        }
    }
}

/* Build the constraint graph, adding successor edges.  */

static void
build_succ_graph (void)
{
  int i;
  constraint_t c;

  for (i = 0; VEC_iterate (constraint_t, constraints, i, c); i++)
    {
      struct constraint_expr lhs;
      struct constraint_expr rhs;
      unsigned int lhsvar;
      unsigned int rhsvar;

      if (!c)
        continue;

      lhs = c->lhs;
      rhs = c->rhs;
      lhsvar = find (get_varinfo_fc (lhs.var)->id);
      rhsvar = find (get_varinfo_fc (rhs.var)->id);

      if (lhs.type == DEREF)
        {
          if (rhs.offset == 0 && lhs.offset == 0 && rhs.type == SCALAR)
            add_graph_edge (graph, FIRST_REF_NODE + lhsvar, rhsvar);
        }
      else if (rhs.type == DEREF)
        {
          if (rhs.offset == 0 && lhs.offset == 0 && lhs.type == SCALAR)
            add_graph_edge (graph, lhsvar, FIRST_REF_NODE + rhsvar);
        }
      else if (rhs.type == ADDRESSOF)
        {
          /* x = &y */
          gcc_assert (find (get_varinfo_fc (rhs.var)->id)
                      == get_varinfo_fc (rhs.var)->id);
          bitmap_set_bit (get_varinfo (lhsvar)->solution, rhsvar);
        }
      else if (lhsvar > anything_id
               && lhsvar != rhsvar && lhs.offset == 0 && rhs.offset == 0)
        {
          add_graph_edge (graph, lhsvar, rhsvar);
        }
    }
}


/* Changed variables on the last iteration.  */
static unsigned int changed_count;
static sbitmap changed;

DEF_VEC_I(unsigned);
DEF_VEC_ALLOC_I(unsigned,heap);


/* Strongly Connected Component visitation info.  */

struct scc_info
{
  sbitmap visited;
  sbitmap deleted;
  unsigned int *dfs;
  unsigned int *node_mapping;
  int current_index;
  VEC(unsigned,heap) *scc_stack;
};


/* Recursive routine to find strongly connected components in GRAPH.
   SI is the SCC info to store the information in, and N is the id of current
   graph node we are processing.

   This is Tarjan's strongly connected component finding algorithm, as
   modified by Nuutila to keep only non-root nodes on the stack.
   The algorithm can be found in "On finding the strongly connected
   connected components in a directed graph" by Esko Nuutila and Eljas
   Soisalon-Soininen, in Information Processing Letters volume 49,
   number 1, pages 9-14.  */

static void
scc_visit (constraint_graph_t graph, struct scc_info *si, unsigned int n)
{
  unsigned int i;
  bitmap_iterator bi;
  unsigned int my_dfs;

  SET_BIT (si->visited, n);
  si->dfs[n] = si->current_index ++;
  my_dfs = si->dfs[n];

  /* Visit all the successors.  */
  EXECUTE_IF_IN_NONNULL_BITMAP (graph->succs[n], 0, i, bi)
    {
      unsigned int w;

      if (i > LAST_REF_NODE)
        break;

      w = find (i);
      if (TEST_BIT (si->deleted, w))
        continue;

      if (!TEST_BIT (si->visited, w))
        scc_visit (graph, si, w);
      {
        unsigned int t = find (w);
        unsigned int nnode = find (n);
        gcc_assert (nnode == n);

        if (si->dfs[t] < si->dfs[nnode])
          si->dfs[n] = si->dfs[t];
      }
    }

  /* See if any components have been identified.  */
  if (si->dfs[n] == my_dfs)
    {
      if (VEC_length (unsigned, si->scc_stack) > 0
          && si->dfs[VEC_last (unsigned, si->scc_stack)] >= my_dfs)
        {
          bitmap scc = BITMAP_ALLOC (NULL);
          bool have_ref_node = n >= FIRST_REF_NODE;
          unsigned int lowest_node;
          bitmap_iterator bi;

          bitmap_set_bit (scc, n);

          while (VEC_length (unsigned, si->scc_stack) != 0
                 && si->dfs[VEC_last (unsigned, si->scc_stack)] >= my_dfs)
            {
              unsigned int w = VEC_pop (unsigned, si->scc_stack);

              bitmap_set_bit (scc, w);
              if (w >= FIRST_REF_NODE)
                have_ref_node = true;
            }

          lowest_node = bitmap_first_set_bit (scc);
          gcc_assert (lowest_node < FIRST_REF_NODE);

          /* Collapse the SCC nodes into a single node, and mark the
             indirect cycles.  */
          EXECUTE_IF_SET_IN_BITMAP (scc, 0, i, bi)
            {
              if (i < FIRST_REF_NODE)
                {
                  if (unite (lowest_node, i))
                    unify_nodes (graph, lowest_node, i, false);
                }
              else
                {
                  unite (lowest_node, i);
                  graph->indirect_cycles[i - FIRST_REF_NODE] = lowest_node;
                }
            }
        }
      SET_BIT (si->deleted, n);
    }
  else
    VEC_safe_push (unsigned, heap, si->scc_stack, n);
}

/* Unify node FROM into node TO, updating the changed count if
   necessary when UPDATE_CHANGED is true.  */

static void
unify_nodes (constraint_graph_t graph, unsigned int to, unsigned int from,
             bool update_changed)
{

  gcc_assert (to != from && find (to) == to);
  if (dump_file && (dump_flags & TDF_DETAILS))
    fprintf (dump_file, "Unifying %s to %s\n",
             get_varinfo (from)->name,
             get_varinfo (to)->name);

  if (update_changed)
    stats.unified_vars_dynamic++;
  else
    stats.unified_vars_static++;

  merge_graph_nodes (graph, to, from);
  merge_node_constraints (graph, to, from);

  if (get_varinfo (from)->no_tbaa_pruning)
    get_varinfo (to)->no_tbaa_pruning = true;

  /* Mark TO as changed if FROM was changed. If TO was already marked
     as changed, decrease the changed count.  */

  if (update_changed && TEST_BIT (changed, from))
    {
      RESET_BIT (changed, from);
      if (!TEST_BIT (changed, to))
        SET_BIT (changed, to);
      else
        {
          gcc_assert (changed_count > 0);
          changed_count--;
        }
    }
  if (get_varinfo (from)->solution)
    {
      /* If the solution changes because of the merging, we need to mark
         the variable as changed.  */
      if (bitmap_ior_into (get_varinfo (to)->solution,
                           get_varinfo (from)->solution))
        {
          if (update_changed && !TEST_BIT (changed, to))
            {
              SET_BIT (changed, to);
              changed_count++;
            }
        }
      
      BITMAP_FREE (get_varinfo (from)->solution);
      BITMAP_FREE (get_varinfo (from)->oldsolution);
      
      if (stats.iterations > 0)
        {
          BITMAP_FREE (get_varinfo (to)->oldsolution);
          get_varinfo (to)->oldsolution = BITMAP_ALLOC (&oldpta_obstack);
        }
    }
  if (valid_graph_edge (graph, to, to))
    {
      if (graph->succs[to])
        bitmap_clear_bit (graph->succs[to], to);
    }
}

/* Information needed to compute the topological ordering of a graph.  */

struct topo_info
{
  /* sbitmap of visited nodes.  */
  sbitmap visited;
  /* Array that stores the topological order of the graph, *in
     reverse*.  */
  VEC(unsigned,heap) *topo_order;
};


/* Initialize and return a topological info structure.  */

static struct topo_info *
init_topo_info (void)
{
  size_t size = graph->size;
  struct topo_info *ti = XNEW (struct topo_info);
  ti->visited = sbitmap_alloc (size);
  sbitmap_zero (ti->visited);
  ti->topo_order = VEC_alloc (unsigned, heap, 1);
  return ti;
}


/* Free the topological sort info pointed to by TI.  */

static void
free_topo_info (struct topo_info *ti)
{
  sbitmap_free (ti->visited);
  VEC_free (unsigned, heap, ti->topo_order);
  free (ti);
}

/* Visit the graph in topological order, and store the order in the
   topo_info structure.  */

static void
topo_visit (constraint_graph_t graph, struct topo_info *ti,
            unsigned int n)
{
  bitmap_iterator bi;
  unsigned int j;

  SET_BIT (ti->visited, n);

  if (graph->succs[n])
    EXECUTE_IF_SET_IN_BITMAP (graph->succs[n], 0, j, bi)
      {
        if (!TEST_BIT (ti->visited, j))
          topo_visit (graph, ti, j);
      }

  VEC_safe_push (unsigned, heap, ti->topo_order, n);
}

/* Return true if variable N + OFFSET is a legal field of N.  */

static bool
type_safe (unsigned int n, unsigned HOST_WIDE_INT *offset)
{
  varinfo_t ninfo = get_varinfo (n);

  /* For things we've globbed to single variables, any offset into the
     variable acts like the entire variable, so that it becomes offset
     0.  */
  if (ninfo->is_special_var
      || ninfo->is_artificial_var
      || ninfo->is_unknown_size_var)
    {
      *offset = 0;
      return true;
    }
  return (get_varinfo (n)->offset + *offset) < get_varinfo (n)->fullsize;
}

/* Process a constraint C that represents x = *y, using DELTA as the
   starting solution.  */

static void
do_sd_constraint (constraint_graph_t graph, constraint_t c,
                  bitmap delta)
{
  unsigned int lhs = c->lhs.var;
  bool flag = false;
  bitmap sol = get_varinfo (lhs)->solution;
  unsigned int j;
  bitmap_iterator bi;

 if (bitmap_bit_p (delta, anything_id))
   {
     flag = !bitmap_bit_p (sol, anything_id);
     if (flag)
       bitmap_set_bit (sol, anything_id);
     goto done;
   }
  /* For each variable j in delta (Sol(y)), add
     an edge in the graph from j to x, and union Sol(j) into Sol(x).  */
  EXECUTE_IF_SET_IN_BITMAP (delta, 0, j, bi)
    {
      unsigned HOST_WIDE_INT roffset = c->rhs.offset;
      if (type_safe (j, &roffset))
        {
          varinfo_t v;
          unsigned HOST_WIDE_INT fieldoffset = get_varinfo (j)->offset + roffset;
          unsigned int t;

          v = first_vi_for_offset (get_varinfo (j), fieldoffset);
          if (!v)
            continue;
          t = find (v->id);

          /* Adding edges from the special vars is pointless.
             They don't have sets that can change.  */
          if (get_varinfo (t) ->is_special_var)
            flag |= bitmap_ior_into (sol, get_varinfo (t)->solution);
          else if (add_graph_edge (graph, lhs, t))
            flag |= bitmap_ior_into (sol, get_varinfo (t)->solution);
        }
      else if (0 && dump_file && !(get_varinfo (j)->is_special_var))
        fprintf (dump_file, "Untypesafe usage in do_sd_constraint\n");

    }

done:
  /* If the LHS solution changed, mark the var as changed.  */
  if (flag)
    {
      get_varinfo (lhs)->solution = sol;
      if (!TEST_BIT (changed, lhs))
        {
          SET_BIT (changed, lhs);
          changed_count++;
        }
    }
}

/* Process a constraint C that represents *x = y.  */

static void
do_ds_constraint (constraint_t c, bitmap delta)
{
  unsigned int rhs = c->rhs.var;
  bitmap sol = get_varinfo (rhs)->solution;
  unsigned int j;
  bitmap_iterator bi;

 if (bitmap_bit_p (sol, anything_id))
   {
     EXECUTE_IF_SET_IN_BITMAP (delta, 0, j, bi)
       {
         varinfo_t jvi = get_varinfo (j);
         unsigned int t;
         unsigned int loff = c->lhs.offset;
         unsigned HOST_WIDE_INT fieldoffset = jvi->offset + loff;
         varinfo_t v;

         v = first_vi_for_offset (get_varinfo (j), fieldoffset);
         if (!v)
           continue;
         t = find (v->id);

         if (!bitmap_bit_p (get_varinfo (t)->solution, anything_id))
           {
             bitmap_set_bit (get_varinfo (t)->solution, anything_id);
             if (!TEST_BIT (changed, t))
               {
                 SET_BIT (changed, t);
                 changed_count++;
               }
           }
       }
     return;
   }

  /* For each member j of delta (Sol(x)), add an edge from y to j and
     union Sol(y) into Sol(j) */
  EXECUTE_IF_SET_IN_BITMAP (delta, 0, j, bi)
    {
      unsigned HOST_WIDE_INT loff = c->lhs.offset;
      if (type_safe (j, &loff) && !(get_varinfo (j)->is_special_var))
        {
          varinfo_t v;
          unsigned int t;
          unsigned HOST_WIDE_INT fieldoffset = get_varinfo (j)->offset + loff;
          bitmap tmp;

          v = first_vi_for_offset (get_varinfo (j), fieldoffset);
          if (!v)
            continue;
          t = find (v->id);
          tmp = get_varinfo (t)->solution;

          if (set_union_with_increment (tmp, sol, 0))
            {
              get_varinfo (t)->solution = tmp;
              if (t == rhs)
                sol = get_varinfo (rhs)->solution;
              if (!TEST_BIT (changed, t))
                {
                  SET_BIT (changed, t);
                  changed_count++;
                }
            }
        }
      else if (0 && dump_file && !(get_varinfo (j)->is_special_var))
        fprintf (dump_file, "Untypesafe usage in do_ds_constraint\n");
    }
}

/* Handle a non-simple (simple meaning requires no iteration),
   constraint (IE *x = &y, x = *y, *x = y, and x = y with offsets involved).  */

static void
do_complex_constraint (constraint_graph_t graph, constraint_t c, bitmap delta)
{
  if (c->lhs.type == DEREF)
    {
      if (c->rhs.type == ADDRESSOF)
        {
          gcc_unreachable();
        }
      else
        {
          /* *x = y */
          do_ds_constraint (c, delta);
        }
    }
  else if (c->rhs.type == DEREF)
    {
      /* x = *y */
      if (!(get_varinfo (c->lhs.var)->is_special_var))
        do_sd_constraint (graph, c, delta);
    }
  else
    {
      bitmap tmp;
      bitmap solution;
      bool flag = false;

      gcc_assert (c->rhs.type == SCALAR && c->lhs.type == SCALAR);
      solution = get_varinfo (c->rhs.var)->solution;
      tmp = get_varinfo (c->lhs.var)->solution;

      flag = set_union_with_increment (tmp, solution, c->rhs.offset);

      if (flag)
        {
          get_varinfo (c->lhs.var)->solution = tmp;
          if (!TEST_BIT (changed, c->lhs.var))
            {
              SET_BIT (changed, c->lhs.var);
              changed_count++;
            }
        }
    }
}

/* Initialize and return a new SCC info structure.  */

static struct scc_info *
init_scc_info (size_t size)
{
  struct scc_info *si = XNEW (struct scc_info);
  size_t i;

  si->current_index = 0;
  si->visited = sbitmap_alloc (size);
  sbitmap_zero (si->visited);
  si->deleted = sbitmap_alloc (size);
  sbitmap_zero (si->deleted);
  si->node_mapping = XNEWVEC (unsigned int, size);
  si->dfs = XCNEWVEC (unsigned int, size);

  for (i = 0; i < size; i++)
    si->node_mapping[i] = i;

  si->scc_stack = VEC_alloc (unsigned, heap, 1);
  return si;
}

/* Free an SCC info structure pointed to by SI */

static void
free_scc_info (struct scc_info *si)
{
  sbitmap_free (si->visited);
  sbitmap_free (si->deleted);
  free (si->node_mapping);
  free (si->dfs);
  VEC_free (unsigned, heap, si->scc_stack);
  free (si);
}


/* Find indirect cycles in GRAPH that occur, using strongly connected
   components, and note them in the indirect cycles map.

   This technique comes from Ben Hardekopf and Calvin Lin,
   "It Pays to be Lazy: Fast and Accurate Pointer Analysis for Millions of
   Lines of Code", submitted to PLDI 2007.  */

static void
find_indirect_cycles (constraint_graph_t graph)
{
  unsigned int i;
  unsigned int size = graph->size;
  struct scc_info *si = init_scc_info (size);

  for (i = 0; i < MIN (LAST_REF_NODE, size); i ++ )
    if (!TEST_BIT (si->visited, i) && find (i) == i)
      scc_visit (graph, si, i);

  free_scc_info (si);
}

/* Compute a topological ordering for GRAPH, and store the result in the
   topo_info structure TI.  */

static void
compute_topo_order (constraint_graph_t graph,
                    struct topo_info *ti)
{
  unsigned int i;
  unsigned int size = graph->size;

  for (i = 0; i != size; ++i)
    if (!TEST_BIT (ti->visited, i) && find (i) == i)
      topo_visit (graph, ti, i);
}

/* Structure used to for hash value numbering of pointer equivalence
   classes.  */

typedef struct equiv_class_label
{
  unsigned int equivalence_class;
  bitmap labels;
  hashval_t hashcode;
} *equiv_class_label_t;
typedef const struct equiv_class_label *const_equiv_class_label_t;

/* A hashtable for mapping a bitmap of labels->pointer equivalence
   classes.  */
static htab_t pointer_equiv_class_table;

/* A hashtable for mapping a bitmap of labels->location equivalence
   classes.  */
static htab_t location_equiv_class_table;

/* Hash function for a equiv_class_label_t */

static hashval_t
equiv_class_label_hash (const void *p)
{
  const_equiv_class_label_t const ecl = (const_equiv_class_label_t) p;
  return ecl->hashcode;
}

/* Equality function for two equiv_class_label_t's.  */

static int
equiv_class_label_eq (const void *p1, const void *p2)
{
  const_equiv_class_label_t const eql1 = (const_equiv_class_label_t) p1;
  const_equiv_class_label_t const eql2 = (const_equiv_class_label_t) p2;
  return bitmap_equal_p (eql1->labels, eql2->labels);
}

/* Lookup a equivalence class in TABLE by the bitmap of LABELS it
   contains.  */

static unsigned int
equiv_class_lookup (htab_t table, bitmap labels)
{
  void **slot;
  struct equiv_class_label ecl;

  ecl.labels = labels;
  ecl.hashcode = bitmap_hash (labels);

  slot = htab_find_slot_with_hash (table, &ecl,
                                   ecl.hashcode, NO_INSERT);
  if (!slot)
    return 0;
  else
    return ((equiv_class_label_t) *slot)->equivalence_class;
}


/* Add an equivalence class named EQUIVALENCE_CLASS with labels LABELS
   to TABLE.  */

static void
equiv_class_add (htab_t table, unsigned int equivalence_class,
                 bitmap labels)
{
  void **slot;
  equiv_class_label_t ecl = XNEW (struct equiv_class_label);

  ecl->labels = labels;
  ecl->equivalence_class = equivalence_class;
  ecl->hashcode = bitmap_hash (labels);

  slot = htab_find_slot_with_hash (table, ecl,
                                   ecl->hashcode, INSERT);
  gcc_assert (!*slot);
  *slot = (void *) ecl;
}

/* Perform offline variable substitution.

   This is a worst case quadratic time way of identifying variables
   that must have equivalent points-to sets, including those caused by
   static cycles, and single entry subgraphs, in the constraint graph.

   The technique is described in "Exploiting Pointer and Location
   Equivalence to Optimize Pointer Analysis. In the 14th International
   Static Analysis Symposium (SAS), August 2007."  It is known as the
   "HU" algorithm, and is equivalent to value numbering the collapsed
   constraint graph including evaluating unions.

   The general method of finding equivalence classes is as follows:
   Add fake nodes (REF nodes) and edges for *a = b and a = *b constraints.
   Initialize all non-REF nodes to be direct nodes.
   For each constraint a = a U {b}, we set pts(a) = pts(a) u {fresh
   variable}
   For each constraint containing the dereference, we also do the same
   thing.

   We then compute SCC's in the graph and unify nodes in the same SCC,
   including pts sets.

   For each non-collapsed node x:
    Visit all unvisited explicit incoming edges.
    Ignoring all non-pointers, set pts(x) = Union of pts(a) for y
    where y->x.
    Lookup the equivalence class for pts(x).
     If we found one, equivalence_class(x) = found class.
     Otherwise, equivalence_class(x) = new class, and new_class is
    added to the lookup table.

   All direct nodes with the same equivalence class can be replaced
   with a single representative node.
   All unlabeled nodes (label == 0) are not pointers and all edges
   involving them can be eliminated.
   We perform these optimizations during rewrite_constraints

   In addition to pointer equivalence class finding, we also perform
   location equivalence class finding.  This is the set of variables
   that always appear together in points-to sets.  We use this to
   compress the size of the points-to sets.  */

/* Current maximum pointer equivalence class id.  */
static int pointer_equiv_class;

/* Current maximum location equivalence class id.  */
static int location_equiv_class;

/* Recursive routine to find strongly connected components in GRAPH,
   and label it's nodes with DFS numbers.  */

static void
condense_visit (constraint_graph_t graph, struct scc_info *si, unsigned int n)
{
  unsigned int i;
  bitmap_iterator bi;
  unsigned int my_dfs;

  gcc_assert (si->node_mapping[n] == n);
  SET_BIT (si->visited, n);
  si->dfs[n] = si->current_index ++;
  my_dfs = si->dfs[n];

  /* Visit all the successors.  */
  EXECUTE_IF_IN_NONNULL_BITMAP (graph->preds[n], 0, i, bi)
    {
      unsigned int w = si->node_mapping[i];

      if (TEST_BIT (si->deleted, w))
        continue;

      if (!TEST_BIT (si->visited, w))
        condense_visit (graph, si, w);
      {
        unsigned int t = si->node_mapping[w];
        unsigned int nnode = si->node_mapping[n];
        gcc_assert (nnode == n);

        if (si->dfs[t] < si->dfs[nnode])
          si->dfs[n] = si->dfs[t];
      }
    }

  /* Visit all the implicit predecessors.  */
  EXECUTE_IF_IN_NONNULL_BITMAP (graph->implicit_preds[n], 0, i, bi)
    {
      unsigned int w = si->node_mapping[i];

      if (TEST_BIT (si->deleted, w))
        continue;

      if (!TEST_BIT (si->visited, w))
        condense_visit (graph, si, w);
      {
        unsigned int t = si->node_mapping[w];
        unsigned int nnode = si->node_mapping[n];
        gcc_assert (nnode == n);

        if (si->dfs[t] < si->dfs[nnode])
          si->dfs[n] = si->dfs[t];
      }
    }

  /* See if any components have been identified.  */
  if (si->dfs[n] == my_dfs)
    {
      while (VEC_length (unsigned, si->scc_stack) != 0
             && si->dfs[VEC_last (unsigned, si->scc_stack)] >= my_dfs)
        {
          unsigned int w = VEC_pop (unsigned, si->scc_stack);
          si->node_mapping[w] = n;

          if (!TEST_BIT (graph->direct_nodes, w))
            RESET_BIT (graph->direct_nodes, n);

          /* Unify our nodes.  */
          if (graph->preds[w])
            {
              if (!graph->preds[n])
                graph->preds[n] = BITMAP_ALLOC (&predbitmap_obstack);
              bitmap_ior_into (graph->preds[n], graph->preds[w]);
            }
          if (graph->implicit_preds[w])
            {
              if (!graph->implicit_preds[n])
                graph->implicit_preds[n] = BITMAP_ALLOC (&predbitmap_obstack);
              bitmap_ior_into (graph->implicit_preds[n],
                               graph->implicit_preds[w]);
            }
          if (graph->points_to[w])
            {
              if (!graph->points_to[n])
                graph->points_to[n] = BITMAP_ALLOC (&predbitmap_obstack);
              bitmap_ior_into (graph->points_to[n],
                               graph->points_to[w]);
            }
          EXECUTE_IF_IN_NONNULL_BITMAP (graph->preds[n], 0, i, bi)
            {
              unsigned int rep = si->node_mapping[i];
              graph->number_incoming[rep]++;
            }
        }
      SET_BIT (si->deleted, n);
    }
  else
    VEC_safe_push (unsigned, heap, si->scc_stack, n);
}

/* Label pointer equivalences.  */

static void
label_visit (constraint_graph_t graph, struct scc_info *si, unsigned int n)
{
  unsigned int i;
  bitmap_iterator bi;
  SET_BIT (si->visited, n);

  if (!graph->points_to[n])
    graph->points_to[n] = BITMAP_ALLOC (&predbitmap_obstack);

  /* Label and union our incoming edges's points to sets.  */
  EXECUTE_IF_IN_NONNULL_BITMAP (graph->preds[n], 0, i, bi)
    {
      unsigned int w = si->node_mapping[i];
      if (!TEST_BIT (si->visited, w))
        label_visit (graph, si, w);

      /* Skip unused edges  */
      if (w == n || graph->pointer_label[w] == 0)
        {
          graph->number_incoming[w]--;
          continue;
        }
      if (graph->points_to[w])
        bitmap_ior_into(graph->points_to[n], graph->points_to[w]);

      /* If all incoming edges to w have been processed and
         graph->points_to[w] was not stored in the hash table, we can
         free it.  */
      graph->number_incoming[w]--;
      if (!graph->number_incoming[w] && !TEST_BIT (graph->pt_used, w))
        {
          BITMAP_FREE (graph->points_to[w]);
        }
    }
  /* Indirect nodes get fresh variables.  */
  if (!TEST_BIT (graph->direct_nodes, n))
    bitmap_set_bit (graph->points_to[n], FIRST_REF_NODE + n);

  if (!bitmap_empty_p (graph->points_to[n]))
    {
      unsigned int label = equiv_class_lookup (pointer_equiv_class_table,
                                               graph->points_to[n]);
      if (!label)
        {
          SET_BIT (graph->pt_used, n);
          label = pointer_equiv_class++;
          equiv_class_add (pointer_equiv_class_table,
                           label, graph->points_to[n]);
        }
      graph->pointer_label[n] = label;
    }
}

/* Perform offline variable substitution, discovering equivalence
   classes, and eliminating non-pointer variables.  */

static struct scc_info *
perform_var_substitution (constraint_graph_t graph)
{
  unsigned int i;
  unsigned int size = graph->size;
  struct scc_info *si = init_scc_info (size);

  bitmap_obstack_initialize (&iteration_obstack);
  pointer_equiv_class_table = htab_create (511, equiv_class_label_hash,
                                           equiv_class_label_eq, free);
  location_equiv_class_table = htab_create (511, equiv_class_label_hash,
                                            equiv_class_label_eq, free);
  pointer_equiv_class = 1;
  location_equiv_class = 1;

  /* Condense the nodes, which means to find SCC's, count incoming
     predecessors, and unite nodes in SCC's.  */
  for (i = 0; i < FIRST_REF_NODE; i++)
    if (!TEST_BIT (si->visited, si->node_mapping[i]))
      condense_visit (graph, si, si->node_mapping[i]);

  sbitmap_zero (si->visited);
  /* Actually the label the nodes for pointer equivalences  */
  for (i = 0; i < FIRST_REF_NODE; i++)
    if (!TEST_BIT (si->visited, si->node_mapping[i]))
      label_visit (graph, si, si->node_mapping[i]);

  /* Calculate location equivalence labels.  */
  for (i = 0; i < FIRST_REF_NODE; i++)
    {
      bitmap pointed_by;
      bitmap_iterator bi;
      unsigned int j;
      unsigned int label;

      if (!graph->pointed_by[i])
        continue;
      pointed_by = BITMAP_ALLOC (&iteration_obstack);

      /* Translate the pointed-by mapping for pointer equivalence
         labels.  */
      EXECUTE_IF_SET_IN_BITMAP (graph->pointed_by[i], 0, j, bi)
        {
          bitmap_set_bit (pointed_by,
                          graph->pointer_label[si->node_mapping[j]]);
        }
      /* The original pointed_by is now dead.  */
      BITMAP_FREE (graph->pointed_by[i]);

      /* Look up the location equivalence label if one exists, or make
         one otherwise.  */
      label = equiv_class_lookup (location_equiv_class_table,
                                  pointed_by);
      if (label == 0)
        {
          label = location_equiv_class++;
          equiv_class_add (location_equiv_class_table,
                           label, pointed_by);
        }
      else
        {
          if (dump_file && (dump_flags & TDF_DETAILS))
            fprintf (dump_file, "Found location equivalence for node %s\n",
                     get_varinfo (i)->name);
          BITMAP_FREE (pointed_by);
        }
      graph->loc_label[i] = label;

    }

  if (dump_file && (dump_flags & TDF_DETAILS))
    for (i = 0; i < FIRST_REF_NODE; i++)
      {
        bool direct_node = TEST_BIT (graph->direct_nodes, i);
        fprintf (dump_file,
                 "Equivalence classes for %s node id %d:%s are pointer: %d"
                 ", location:%d\n",
                 direct_node ? "Direct node" : "Indirect node", i,
                 get_varinfo (i)->name,
                 graph->pointer_label[si->node_mapping[i]],
                 graph->loc_label[si->node_mapping[i]]);
      }

  /* Quickly eliminate our non-pointer variables.  */

  for (i = 0; i < FIRST_REF_NODE; i++)
    {
      unsigned int node = si->node_mapping[i];

      if (graph->pointer_label[node] == 0)
        {
          if (dump_file && (dump_flags & TDF_DETAILS))
            fprintf (dump_file,
                     "%s is a non-pointer variable, eliminating edges.\n",
                     get_varinfo (node)->name);
          stats.nonpointer_vars++;
          clear_edges_for_node (graph, node);
        }
    }

  return si;
}

/* Free information that was only necessary for variable
   substitution.  */

static void
free_var_substitution_info (struct scc_info *si)
{
  free_scc_info (si);
  free (graph->pointer_label);
  free (graph->loc_label);
  free (graph->pointed_by);
  free (graph->points_to);
  free (graph->number_incoming);
  free (graph->eq_rep);
  sbitmap_free (graph->direct_nodes);
  sbitmap_free (graph->pt_used);
  htab_delete (pointer_equiv_class_table);
  htab_delete (location_equiv_class_table);
  bitmap_obstack_release (&iteration_obstack);
}

/* Return an existing node that is equivalent to NODE, which has
   equivalence class LABEL, if one exists.  Return NODE otherwise.  */

static unsigned int
find_equivalent_node (constraint_graph_t graph,
                      unsigned int node, unsigned int label)
{
  /* If the address version of this variable is unused, we can
     substitute it for anything else with the same label.
     Otherwise, we know the pointers are equivalent, but not the
     locations, and we can unite them later.  */

  if (!bitmap_bit_p (graph->address_taken, node))
    {
      gcc_assert (label < graph->size);

      if (graph->eq_rep[label] != -1)
        {
          /* Unify the two variables since we know they are equivalent.  */
          if (unite (graph->eq_rep[label], node))
            unify_nodes (graph, graph->eq_rep[label], node, false);
          return graph->eq_rep[label];
        }
      else
        {
          graph->eq_rep[label] = node;
          graph->pe_rep[label] = node;
        }
    }
  else
    {
      gcc_assert (label < graph->size);
      graph->pe[node] = label;
      if (graph->pe_rep[label] == -1)
        graph->pe_rep[label] = node;
    }

  return node;
}

/* Unite pointer equivalent but not location equivalent nodes in
   GRAPH.  This may only be performed once variable substitution is
   finished.  */

static void
unite_pointer_equivalences (constraint_graph_t graph)
{
  unsigned int i;

  /* Go through the pointer equivalences and unite them to their
     representative, if they aren't already.  */
  for (i = 0; i < FIRST_REF_NODE; i++)
    {
      unsigned int label = graph->pe[i];
      if (label)
        {
          int label_rep = graph->pe_rep[label];
          
          if (label_rep == -1)
            continue;
          
          label_rep = find (label_rep);
          if (label_rep >= 0 && unite (label_rep, find (i)))
            unify_nodes (graph, label_rep, i, false);
        }
    }
}

/* Move complex constraints to the GRAPH nodes they belong to.  */

static void
move_complex_constraints (constraint_graph_t graph)
{
  int i;
  constraint_t c;

  for (i = 0; VEC_iterate (constraint_t, constraints, i, c); i++)
    {
      if (c)
        {
          struct constraint_expr lhs = c->lhs;
          struct constraint_expr rhs = c->rhs;

          if (lhs.type == DEREF)
            {
              insert_into_complex (graph, lhs.var, c);
            }
          else if (rhs.type == DEREF)
            {
              if (!(get_varinfo (lhs.var)->is_special_var))
                insert_into_complex (graph, rhs.var, c);
            }
          else if (rhs.type != ADDRESSOF && lhs.var > anything_id
                   && (lhs.offset != 0 || rhs.offset != 0))
            {
              insert_into_complex (graph, rhs.var, c);
            }
        }
    }
}


/* Optimize and rewrite complex constraints while performing
   collapsing of equivalent nodes.  SI is the SCC_INFO that is the
   result of perform_variable_substitution.  */

static void
rewrite_constraints (constraint_graph_t graph,
                     struct scc_info *si)
{
  int i;
  unsigned int j;
  constraint_t c;

  for (j = 0; j < graph->size; j++)
    gcc_assert (find (j) == j);

  for (i = 0; VEC_iterate (constraint_t, constraints, i, c); i++)
    {
      struct constraint_expr lhs = c->lhs;
      struct constraint_expr rhs = c->rhs;
      unsigned int lhsvar = find (get_varinfo_fc (lhs.var)->id);
      unsigned int rhsvar = find (get_varinfo_fc (rhs.var)->id);
      unsigned int lhsnode, rhsnode;
      unsigned int lhslabel, rhslabel;

      lhsnode = si->node_mapping[lhsvar];
      rhsnode = si->node_mapping[rhsvar];
      lhslabel = graph->pointer_label[lhsnode];
      rhslabel = graph->pointer_label[rhsnode];

      /* See if it is really a non-pointer variable, and if so, ignore
         the constraint.  */
      if (lhslabel == 0)
        {
          if (dump_file && (dump_flags & TDF_DETAILS))
            {
              
              fprintf (dump_file, "%s is a non-pointer variable,"
                       "ignoring constraint:",
                       get_varinfo (lhs.var)->name);
              dump_constraint (dump_file, c);
            }
          VEC_replace (constraint_t, constraints, i, NULL);
          continue;
        }

      if (rhslabel == 0)
        {
          if (dump_file && (dump_flags & TDF_DETAILS))
            {
              
              fprintf (dump_file, "%s is a non-pointer variable,"
                       "ignoring constraint:",
                       get_varinfo (rhs.var)->name);
              dump_constraint (dump_file, c);
            }
          VEC_replace (constraint_t, constraints, i, NULL);
          continue;
        }

      lhsvar = find_equivalent_node (graph, lhsvar, lhslabel);
      rhsvar = find_equivalent_node (graph, rhsvar, rhslabel);
      c->lhs.var = lhsvar;
      c->rhs.var = rhsvar;

    }
}

/* Eliminate indirect cycles involving NODE.  Return true if NODE was
   part of an SCC, false otherwise.  */

static bool
eliminate_indirect_cycles (unsigned int node)
{
  if (graph->indirect_cycles[node] != -1
      && !bitmap_empty_p (get_varinfo (node)->solution))
    {
      unsigned int i;
      VEC(unsigned,heap) *queue = NULL;
      int queuepos;
      unsigned int to = find (graph->indirect_cycles[node]);
      bitmap_iterator bi;

      /* We can't touch the solution set and call unify_nodes
         at the same time, because unify_nodes is going to do
         bitmap unions into it. */

      EXECUTE_IF_SET_IN_BITMAP (get_varinfo (node)->solution, 0, i, bi)
        {
          if (find (i) == i && i != to)
            {
              if (unite (to, i))
                VEC_safe_push (unsigned, heap, queue, i);
            }
        }

      for (queuepos = 0;
           VEC_iterate (unsigned, queue, queuepos, i);
           queuepos++)
        {
          unify_nodes (graph, to, i, true);
        }
      VEC_free (unsigned, heap, queue);
      return true;
    }
  return false;
}

/* Solve the constraint graph GRAPH using our worklist solver.
   This is based on the PW* family of solvers from the "Efficient Field
   Sensitive Pointer Analysis for C" paper.
   It works by iterating over all the graph nodes, processing the complex
   constraints and propagating the copy constraints, until everything stops
   changed.  This corresponds to steps 6-8 in the solving list given above.  */

static void
solve_graph (constraint_graph_t graph)
{
  unsigned int size = graph->size;
  unsigned int i;
  bitmap pts;

  changed_count = 0;
  changed = sbitmap_alloc (size);
  sbitmap_zero (changed);

  /* Mark all initial non-collapsed nodes as changed.  */
  for (i = 0; i < size; i++)
    {
      varinfo_t ivi = get_varinfo (i);
      if (find (i) == i && !bitmap_empty_p (ivi->solution)
          && ((graph->succs[i] && !bitmap_empty_p (graph->succs[i]))
              || VEC_length (constraint_t, graph->complex[i]) > 0))
        {
          SET_BIT (changed, i);
          changed_count++;
        }
    }

  /* Allocate a bitmap to be used to store the changed bits.  */
  pts = BITMAP_ALLOC (&pta_obstack);

  while (changed_count > 0)
    {
      unsigned int i;
      struct topo_info *ti = init_topo_info ();
      stats.iterations++;

      bitmap_obstack_initialize (&iteration_obstack);

      compute_topo_order (graph, ti);

      while (VEC_length (unsigned, ti->topo_order) != 0)
        {

          i = VEC_pop (unsigned, ti->topo_order);

          /* If this variable is not a representative, skip it.  */
          if (find (i) != i)
            continue;

          /* In certain indirect cycle cases, we may merge this
             variable to another.  */
          if (eliminate_indirect_cycles (i) && find (i) != i)
            continue;

          /* If the node has changed, we need to process the
             complex constraints and outgoing edges again.  */
          if (TEST_BIT (changed, i))
            {
              unsigned int j;
              constraint_t c;
              bitmap solution;
              VEC(constraint_t,heap) *complex = graph->complex[i];
              bool solution_empty;

              RESET_BIT (changed, i);
              changed_count--;

              /* Compute the changed set of solution bits.  */
              bitmap_and_compl (pts, get_varinfo (i)->solution,
                                get_varinfo (i)->oldsolution);

              if (bitmap_empty_p (pts))
                continue;

              bitmap_ior_into (get_varinfo (i)->oldsolution, pts);

              solution = get_varinfo (i)->solution;
              solution_empty = bitmap_empty_p (solution);

              /* Process the complex constraints */
              for (j = 0; VEC_iterate (constraint_t, complex, j, c); j++)
                {
                  /* XXX: This is going to unsort the constraints in
                     some cases, which will occasionally add duplicate
                     constraints during unification.  This does not
                     affect correctness.  */
                  c->lhs.var = find (c->lhs.var);
                  c->rhs.var = find (c->rhs.var);

                  /* The only complex constraint that can change our
                     solution to non-empty, given an empty solution,
                     is a constraint where the lhs side is receiving
                     some set from elsewhere.  */
                  if (!solution_empty || c->lhs.type != DEREF)
                    do_complex_constraint (graph, c, pts);
                }

              solution_empty = bitmap_empty_p (solution);

              if (!solution_empty)
                {
                  bitmap_iterator bi;

                  /* Propagate solution to all successors.  */
                  EXECUTE_IF_IN_NONNULL_BITMAP (graph->succs[i],
                                                0, j, bi)
                    {
                      bitmap tmp;
                      bool flag;

                      unsigned int to = find (j);
                      tmp = get_varinfo (to)->solution;
                      flag = false;

                      /* Don't try to propagate to ourselves.  */
                      if (to == i)
                        continue;

                      flag = set_union_with_increment (tmp, pts, 0);

                      if (flag)
                        {
                          get_varinfo (to)->solution = tmp;
                          if (!TEST_BIT (changed, to))
                            {
                              SET_BIT (changed, to);
                              changed_count++;
                            }
                        }
                    }
                }
            }
        }
      free_topo_info (ti);
      bitmap_obstack_release (&iteration_obstack);
    }

  BITMAP_FREE (pts);
  sbitmap_free (changed);
  bitmap_obstack_release (&oldpta_obstack);
}

/* Map from trees to variable infos.  */
static struct pointer_map_t *vi_for_tree;


/* Insert ID as the variable id for tree T in the vi_for_tree map.  */

static void
insert_vi_for_tree (tree t, varinfo_t vi)
{
  void **slot = pointer_map_insert (vi_for_tree, t);
  gcc_assert (vi);
  gcc_assert (*slot == NULL);
  *slot = vi;
}

/* Find the variable info for tree T in VI_FOR_TREE.  If T does not
   exist in the map, return NULL, otherwise, return the varinfo we found.  */

static varinfo_t
lookup_vi_for_tree (tree t)
{
  void **slot = pointer_map_contains (vi_for_tree, t);
  if (slot == NULL)
    return NULL;

  return (varinfo_t) *slot;
}

/* Return a printable name for DECL  */

static const char *
alias_get_name (tree decl)
{
  const char *res = get_name (decl);
  char *temp;
  int num_printed = 0;

  if (res != NULL)
    return res;

  res = "NULL";
  if (!dump_file)
    return res;

  if (TREE_CODE (decl) == SSA_NAME)
    {
      num_printed = asprintf (&temp, "%s_%u",
                              alias_get_name (SSA_NAME_VAR (decl)),
                              SSA_NAME_VERSION (decl));
    }
  else if (DECL_P (decl))
    {
      num_printed = asprintf (&temp, "D.%u", DECL_UID (decl));
    }
  if (num_printed > 0)
    {
      res = ggc_strdup (temp);
      free (temp);
    }
  return res;
}

/* Find the variable id for tree T in the map.
   If T doesn't exist in the map, create an entry for it and return it.  */

static varinfo_t
get_vi_for_tree (tree t)
{
  void **slot = pointer_map_contains (vi_for_tree, t);
  if (slot == NULL)
    return get_varinfo (create_variable_info_for (t, alias_get_name (t)));

  return (varinfo_t) *slot;
}

/* Get a constraint expression from an SSA_VAR_P node.  */

static struct constraint_expr
get_constraint_exp_from_ssa_var (tree t)
{
  struct constraint_expr cexpr;

  gcc_assert (SSA_VAR_P (t) || DECL_P (t));

  /* For parameters, get at the points-to set for the actual parm
     decl.  */
  if (TREE_CODE (t) == SSA_NAME
      && TREE_CODE (SSA_NAME_VAR (t)) == PARM_DECL
      && SSA_NAME_IS_DEFAULT_DEF (t))
    return get_constraint_exp_from_ssa_var (SSA_NAME_VAR (t));

  cexpr.type = SCALAR;

  cexpr.var = get_vi_for_tree (t)->id;
  /* If we determine the result is "anything", and we know this is readonly,
     say it points to readonly memory instead.  */
  if (cexpr.var == anything_id && TREE_READONLY (t))
    {
      cexpr.type = ADDRESSOF;
      cexpr.var = readonly_id;
    }

  cexpr.offset = 0;
  return cexpr;
}

/* Process a completed constraint T, and add it to the constraint
   list.  FROM_CALL is true if this is a constraint coming from a
   call, which means any DEREFs we see are "may-deref's", not
   "must-deref"'s.  */

static void
process_constraint_1 (constraint_t t, bool from_call)
{
  struct constraint_expr rhs = t->rhs;
  struct constraint_expr lhs = t->lhs;

  gcc_assert (rhs.var < VEC_length (varinfo_t, varmap));
  gcc_assert (lhs.var < VEC_length (varinfo_t, varmap));

  if (!from_call)
    {
      if (lhs.type == DEREF)
        get_varinfo (lhs.var)->directly_dereferenced = true;
      if (rhs.type == DEREF)
        get_varinfo (rhs.var)->directly_dereferenced = true;
    }

  if (!use_field_sensitive)
    {
      t->rhs.offset = 0;
      t->lhs.offset = 0;
    }

  /* ANYTHING == ANYTHING is pointless.  */
  if (lhs.var == anything_id && rhs.var == anything_id)
    return;

  /* If we have &ANYTHING = something, convert to SOMETHING = &ANYTHING) */
  else if (lhs.var == anything_id && lhs.type == ADDRESSOF)
    {
      rhs = t->lhs;
      t->lhs = t->rhs;
      t->rhs = rhs;
      process_constraint_1 (t, from_call);
    }
  /* This can happen in our IR with things like n->a = *p */
  else if (rhs.type == DEREF && lhs.type == DEREF && rhs.var != anything_id)
    {
      /* Split into tmp = *rhs, *lhs = tmp */
      tree rhsdecl = get_varinfo (rhs.var)->decl;
      tree pointertype = TREE_TYPE (rhsdecl);
      tree pointedtotype = TREE_TYPE (pointertype);
      tree tmpvar = create_tmp_var_raw (pointedtotype, "doubledereftmp");
      struct constraint_expr tmplhs = get_constraint_exp_from_ssa_var (tmpvar);

      /* If this is an aggregate of known size, we should have passed
         this off to do_structure_copy, and it should have broken it
         up.  */
      gcc_assert (!AGGREGATE_TYPE_P (pointedtotype)
                  || get_varinfo (rhs.var)->is_unknown_size_var);

      process_constraint_1 (new_constraint (tmplhs, rhs), from_call);
      process_constraint_1 (new_constraint (lhs, tmplhs), from_call);
    }
  else if (rhs.type == ADDRESSOF && lhs.type == DEREF)
    {
      /* Split into tmp = &rhs, *lhs = tmp */
      tree rhsdecl = get_varinfo (rhs.var)->decl;
      tree pointertype = TREE_TYPE (rhsdecl);
      tree tmpvar = create_tmp_var_raw (pointertype, "derefaddrtmp");
      struct constraint_expr tmplhs = get_constraint_exp_from_ssa_var (tmpvar);

      process_constraint_1 (new_constraint (tmplhs, rhs), from_call);
      process_constraint_1 (new_constraint (lhs, tmplhs), from_call);
    }
  else
    {
      gcc_assert (rhs.type != ADDRESSOF || rhs.offset == 0);
      VEC_safe_push (constraint_t, heap, constraints, t);
    }
}


/* Process constraint T, performing various simplifications and then
   adding it to our list of overall constraints.  */

static void
process_constraint (constraint_t t)
{
  process_constraint_1 (t, false);
}

/* Return true if T is a variable of a type that could contain
   pointers.  */

static bool
could_have_pointers (tree t)
{
  tree type = TREE_TYPE (t);

  if (POINTER_TYPE_P (type)
      || AGGREGATE_TYPE_P (type)
      || TREE_CODE (type) == COMPLEX_TYPE)
    return true;

  return false;
}

/* Return the position, in bits, of FIELD_DECL from the beginning of its
   structure.  */

static unsigned HOST_WIDE_INT
bitpos_of_field (const tree fdecl)
{

  if (TREE_CODE (DECL_FIELD_OFFSET (fdecl)) != INTEGER_CST
      || TREE_CODE (DECL_FIELD_BIT_OFFSET (fdecl)) != INTEGER_CST)
    return -1;

  return (tree_low_cst (DECL_FIELD_OFFSET (fdecl), 1) * 8)
         + tree_low_cst (DECL_FIELD_BIT_OFFSET (fdecl), 1);
}


/* Return true if an access to [ACCESSPOS, ACCESSSIZE]
   overlaps with a field at [FIELDPOS, FIELDSIZE] */

static bool
offset_overlaps_with_access (const unsigned HOST_WIDE_INT fieldpos,
                             const unsigned HOST_WIDE_INT fieldsize,
                             const unsigned HOST_WIDE_INT accesspos,
                             const unsigned HOST_WIDE_INT accesssize)
{
  if (fieldpos == accesspos && fieldsize == accesssize)
    return true;
  if (accesspos >= fieldpos && accesspos < (fieldpos + fieldsize))
    return true;
  if (accesspos < fieldpos && (accesspos + accesssize > fieldpos))
    return true;

  return false;
}

/* Given a COMPONENT_REF T, return the constraint_expr for it.  */

static void
get_constraint_for_component_ref (tree t, VEC(ce_s, heap) **results)
{
  tree orig_t = t;
  HOST_WIDE_INT bitsize = -1;
  HOST_WIDE_INT bitmaxsize = -1;
  HOST_WIDE_INT bitpos;
  tree forzero;
  struct constraint_expr *result;
  unsigned int beforelength = VEC_length (ce_s, *results);

  /* Some people like to do cute things like take the address of
     &0->a.b */
  forzero = t;
  while (!SSA_VAR_P (forzero) && !CONSTANT_CLASS_P (forzero))
    forzero = TREE_OPERAND (forzero, 0);

  if (CONSTANT_CLASS_P (forzero) && integer_zerop (forzero))
    {
      struct constraint_expr temp;

      temp.offset = 0;
      temp.var = integer_id;
      temp.type = SCALAR;
      VEC_safe_push (ce_s, heap, *results, &temp);
      return;
    }

  t = get_ref_base_and_extent (t, &bitpos, &bitsize, &bitmaxsize);

  /* String constants are readonly, so there is nothing to really do
     here.  */
  if (TREE_CODE (t) == STRING_CST)
    return;

  get_constraint_for (t, results);
  result = VEC_last (ce_s, *results);
  result->offset = bitpos;

  gcc_assert (beforelength + 1 == VEC_length (ce_s, *results));

  /* This can also happen due to weird offsetof type macros.  */
  if (TREE_CODE (t) != ADDR_EXPR && result->type == ADDRESSOF)
    result->type = SCALAR;

  if (result->type == SCALAR)
    {
      /* In languages like C, you can access one past the end of an
         array.  You aren't allowed to dereference it, so we can
         ignore this constraint. When we handle pointer subtraction,
         we may have to do something cute here.  */

      if (result->offset < get_varinfo (result->var)->fullsize
          && bitmaxsize != 0)
        {
          /* It's also not true that the constraint will actually start at the
             right offset, it may start in some padding.  We only care about
             setting the constraint to the first actual field it touches, so
             walk to find it.  */
          varinfo_t curr;
          for (curr = get_varinfo (result->var); curr; curr = curr->next)
            {
              if (offset_overlaps_with_access (curr->offset, curr->size,
                                               result->offset, bitmaxsize))
                {
                  result->var = curr->id;
                  break;
                }
            }
          /* assert that we found *some* field there. The user couldn't be
             accessing *only* padding.  */
          /* Still the user could access one past the end of an array
             embedded in a struct resulting in accessing *only* padding.  */
          gcc_assert (curr || ref_contains_array_ref (orig_t));
        }
      else if (bitmaxsize == 0)
        {
          if (dump_file && (dump_flags & TDF_DETAILS))
            fprintf (dump_file, "Access to zero-sized part of variable,"
                     "ignoring\n");
        }
      else
        if (dump_file && (dump_flags & TDF_DETAILS))
          fprintf (dump_file, "Access to past the end of variable, ignoring\n");

      result->offset = 0;
    }
  else if (bitmaxsize == -1)
    {
      /* We can't handle DEREF constraints with unknown size, we'll
         get the wrong answer.  Punt and return anything.  */
      result->var = anything_id;
      result->offset = 0;
    }
}


/* Dereference the constraint expression CONS, and return the result.
   DEREF (ADDRESSOF) = SCALAR
   DEREF (SCALAR) = DEREF
   DEREF (DEREF) = (temp = DEREF1; result = DEREF(temp))
   This is needed so that we can handle dereferencing DEREF constraints.  */

static void
do_deref (VEC (ce_s, heap) **constraints)
{
  struct constraint_expr *c;
  unsigned int i = 0;

  for (i = 0; VEC_iterate (ce_s, *constraints, i, c); i++)
    {
      if (c->type == SCALAR)
        c->type = DEREF;
      else if (c->type == ADDRESSOF)
        c->type = SCALAR;
      else if (c->type == DEREF)
        {
          tree tmpvar = create_tmp_var_raw (ptr_type_node, "dereftmp");
          struct constraint_expr tmplhs = get_constraint_exp_from_ssa_var (tmpvar);
          process_constraint (new_constraint (tmplhs, *c));
          c->var = tmplhs.var;
        }
      else
        gcc_unreachable ();
    }
}

/* Given a tree T, return the constraint expression for it.  */

static void
get_constraint_for (tree t, VEC (ce_s, heap) **results)
{
  struct constraint_expr temp;

  /* x = integer is all glommed to a single variable, which doesn't
     point to anything by itself.  That is, of course, unless it is an
     integer constant being treated as a pointer, in which case, we
     will return that this is really the addressof anything.  This
     happens below, since it will fall into the default case. The only
     case we know something about an integer treated like a pointer is
     when it is the NULL pointer, and then we just say it points to
     NULL.  */
  if (TREE_CODE (t) == INTEGER_CST
      && integer_zerop (t))
    {
      temp.var = nothing_id;
      temp.type = ADDRESSOF;
      temp.offset = 0;
      VEC_safe_push (ce_s, heap, *results, &temp);
      return;
    }

  switch (TREE_CODE_CLASS (TREE_CODE (t)))
    {
    case tcc_expression:
    case tcc_vl_exp:
      {
        switch (TREE_CODE (t))
          {
          case ADDR_EXPR:
            {
              struct constraint_expr *c;
              unsigned int i;
              tree exp = TREE_OPERAND (t, 0);
              tree pttype = TREE_TYPE (TREE_TYPE (t));

              get_constraint_for (exp, results);


              /* Complex types are special. Taking the address of one
                 allows you to access either part of it through that
                 pointer.  */
              if (VEC_length (ce_s, *results) == 1 &&
                  TREE_CODE (pttype) == COMPLEX_TYPE)
                {
                  struct constraint_expr *origrhs;
                  varinfo_t origvar;
                  struct constraint_expr tmp;

                  gcc_assert (VEC_length (ce_s, *results) == 1);
                  origrhs = VEC_last (ce_s, *results);
                  tmp = *origrhs;
                  VEC_pop (ce_s, *results);
                  origvar = get_varinfo (origrhs->var);
                  for (; origvar; origvar = origvar->next)
                    {
                      tmp.var = origvar->id;
                      VEC_safe_push (ce_s, heap, *results, &tmp);
                    }
                }

              for (i = 0; VEC_iterate (ce_s, *results, i, c); i++)
                {
                  if (c->type == DEREF)
                    c->type = SCALAR;
                  else
                    c->type = ADDRESSOF;
                }
              return;
            }
            break;
          case CALL_EXPR:
            /* XXX: In interprocedural mode, if we didn't have the
               body, we would need to do *each pointer argument =
               &ANYTHING added.  */
            if (call_expr_flags (t) & (ECF_MALLOC | ECF_MAY_BE_ALLOCA))
              {
                varinfo_t vi;
                tree heapvar = heapvar_lookup (t);

                if (heapvar == NULL)
                  {
                    heapvar = create_tmp_var_raw (ptr_type_node, "HEAP");
                    DECL_EXTERNAL (heapvar) = 1;
                    get_var_ann (heapvar)->is_heapvar = 1;
                    if (gimple_referenced_vars (cfun))
                      add_referenced_var (heapvar);
                    heapvar_insert (t, heapvar);
                  }

                temp.var = create_variable_info_for (heapvar,
                                                     alias_get_name (heapvar));

                vi = get_varinfo (temp.var);
                vi->is_artificial_var = 1;
                vi->is_heap_var = 1;
                temp.type = ADDRESSOF;
                temp.offset = 0;
                VEC_safe_push (ce_s, heap, *results, &temp);
                return;
              }
            else
              {
                temp.var = anything_id;
                temp.type = SCALAR;
                temp.offset = 0;
                VEC_safe_push (ce_s, heap, *results, &temp);
                return;
              }
            break;
          default:
            {
              temp.type = ADDRESSOF;
              temp.var = anything_id;
              temp.offset = 0;
              VEC_safe_push (ce_s, heap, *results, &temp);
              return;
            }
          }
      }
    case tcc_reference:
      {
        switch (TREE_CODE (t))
          {
          case INDIRECT_REF:
            {
              get_constraint_for (TREE_OPERAND (t, 0), results);
              do_deref (results);
              return;
            }
          case ARRAY_REF:
          case ARRAY_RANGE_REF:
          case COMPONENT_REF:
            get_constraint_for_component_ref (t, results);
            return;
          default:
            {
              temp.type = ADDRESSOF;
              temp.var = anything_id;
              temp.offset = 0;
              VEC_safe_push (ce_s, heap, *results, &temp);
              return;
            }
          }
      }
    case tcc_unary:
      {
        switch (TREE_CODE (t))
          {
          case NOP_EXPR:
          case CONVERT_EXPR:
          case NON_LVALUE_EXPR:
            {
              tree op = TREE_OPERAND (t, 0);

              /* Cast from non-pointer to pointers are bad news for us.
                 Anything else, we see through */
              if (!(POINTER_TYPE_P (TREE_TYPE (t))
                    && ! POINTER_TYPE_P (TREE_TYPE (op))))
                {
                  get_constraint_for (op, results);
                  return;
                }

              /* FALLTHRU  */
            }
          default:
            {
              temp.type = ADDRESSOF;
              temp.var = anything_id;
              temp.offset = 0;
              VEC_safe_push (ce_s, heap, *results, &temp);
              return;
            }
          }
      }
    case tcc_exceptional:
      {
        switch (TREE_CODE (t))
          {
          case PHI_NODE:
            {
              get_constraint_for (PHI_RESULT (t), results);
              return;
            }
            break;
          case SSA_NAME:
            {
              struct constraint_expr temp;
              temp = get_constraint_exp_from_ssa_var (t);
              VEC_safe_push (ce_s, heap, *results, &temp);
              return;
            }
            break;
          default:
            {
              temp.type = ADDRESSOF;
              temp.var = anything_id;
              temp.offset = 0;
              VEC_safe_push (ce_s, heap, *results, &temp);
              return;
            }
          }
      }
    case tcc_declaration:
      {
        struct constraint_expr temp;
        temp = get_constraint_exp_from_ssa_var (t);
        VEC_safe_push (ce_s, heap, *results, &temp);
        return;
      }
    default:
      {
        temp.type = ADDRESSOF;
        temp.var = anything_id;
        temp.offset = 0;
        VEC_safe_push (ce_s, heap, *results, &temp);
        return;
      }
    }
}


/* Handle the structure copy case where we have a simple structure copy
   between LHS and RHS that is of SIZE (in bits)

   For each field of the lhs variable (lhsfield)
     For each field of the rhs variable at lhsfield.offset (rhsfield)
       add the constraint lhsfield = rhsfield

   If we fail due to some kind of type unsafety or other thing we
   can't handle, return false.  We expect the caller to collapse the
   variable in that case.  */

static bool
do_simple_structure_copy (const struct constraint_expr lhs,
                          const struct constraint_expr rhs,
                          const unsigned HOST_WIDE_INT size)
{
  varinfo_t p = get_varinfo (lhs.var);
  unsigned HOST_WIDE_INT pstart, last;
  pstart = p->offset;
  last = p->offset + size;
  for (; p && p->offset < last; p = p->next)
    {
      varinfo_t q;
      struct constraint_expr templhs = lhs;
      struct constraint_expr temprhs = rhs;
      unsigned HOST_WIDE_INT fieldoffset;

      templhs.var = p->id;
      q = get_varinfo (temprhs.var);
      fieldoffset = p->offset - pstart;
      q = first_vi_for_offset (q, q->offset + fieldoffset);
      if (!q)
        return false;
      temprhs.var = q->id;
      process_constraint (new_constraint (templhs, temprhs));
    }
  return true;
}


/* Handle the structure copy case where we have a  structure copy between a
   aggregate on the LHS and a dereference of a pointer on the RHS
   that is of SIZE (in bits)

   For each field of the lhs variable (lhsfield)
       rhs.offset = lhsfield->offset
       add the constraint lhsfield = rhs
*/

static void
do_rhs_deref_structure_copy (const struct constraint_expr lhs,
                             const struct constraint_expr rhs,
                             const unsigned HOST_WIDE_INT size)
{
  varinfo_t p = get_varinfo (lhs.var);
  unsigned HOST_WIDE_INT pstart,last;
  pstart = p->offset;
  last = p->offset + size;

  for (; p && p->offset < last; p = p->next)
    {
      varinfo_t q;
      struct constraint_expr templhs = lhs;
      struct constraint_expr temprhs = rhs;
      unsigned HOST_WIDE_INT fieldoffset;


      if (templhs.type == SCALAR)
        templhs.var = p->id;
      else
        templhs.offset = p->offset;

      q = get_varinfo (temprhs.var);
      fieldoffset = p->offset - pstart;
      temprhs.offset += fieldoffset;
      process_constraint (new_constraint (templhs, temprhs));
    }
}

/* Handle the structure copy case where we have a structure copy
   between an aggregate on the RHS and a dereference of a pointer on
   the LHS that is of SIZE (in bits)

   For each field of the rhs variable (rhsfield)
       lhs.offset = rhsfield->offset
       add the constraint lhs = rhsfield
*/

static void
do_lhs_deref_structure_copy (const struct constraint_expr lhs,
                             const struct constraint_expr rhs,
                             const unsigned HOST_WIDE_INT size)
{
  varinfo_t p = get_varinfo (rhs.var);
  unsigned HOST_WIDE_INT pstart,last;
  pstart = p->offset;
  last = p->offset + size;

  for (; p && p->offset < last; p = p->next)
    {
      varinfo_t q;
      struct constraint_expr templhs = lhs;
      struct constraint_expr temprhs = rhs;
      unsigned HOST_WIDE_INT fieldoffset;


      if (temprhs.type == SCALAR)
        temprhs.var = p->id;
      else
        temprhs.offset = p->offset;

      q = get_varinfo (templhs.var);
      fieldoffset = p->offset - pstart;
      templhs.offset += fieldoffset;
      process_constraint (new_constraint (templhs, temprhs));
    }
}

/* Sometimes, frontends like to give us bad type information.  This
   function will collapse all the fields from VAR to the end of VAR,
   into VAR, so that we treat those fields as a single variable.
   We return the variable they were collapsed into.  */

static unsigned int
collapse_rest_of_var (unsigned int var)
{
  varinfo_t currvar = get_varinfo (var);
  varinfo_t field;

  for (field = currvar->next; field; field = field->next)
    {
      if (dump_file)
        fprintf (dump_file, "Type safety: Collapsing var %s into %s\n",
                 field->name, currvar->name);

      gcc_assert (!field->collapsed_to);
      field->collapsed_to = currvar;
    }

  currvar->next = NULL;
  currvar->size = currvar->fullsize - currvar->offset;

  return currvar->id;
}

/* Handle aggregate copies by expanding into copies of the respective
   fields of the structures.  */

static void
do_structure_copy (tree lhsop, tree rhsop)
{
  struct constraint_expr lhs, rhs, tmp;
  VEC (ce_s, heap) *lhsc = NULL, *rhsc = NULL;
  varinfo_t p;
  unsigned HOST_WIDE_INT lhssize;
  unsigned HOST_WIDE_INT rhssize;

  get_constraint_for (lhsop, &lhsc);
  get_constraint_for (rhsop, &rhsc);
  gcc_assert (VEC_length (ce_s, lhsc) == 1);
  gcc_assert (VEC_length (ce_s, rhsc) == 1);
  lhs = *(VEC_last (ce_s, lhsc));
  rhs = *(VEC_last (ce_s, rhsc));

  VEC_free (ce_s, heap, lhsc);
  VEC_free (ce_s, heap, rhsc);

  /* If we have special var = x, swap it around.  */
  if (lhs.var <= integer_id && !(get_varinfo (rhs.var)->is_special_var))
    {
      tmp = lhs;
      lhs = rhs;
      rhs = tmp;
    }

  /*  This is fairly conservative for the RHS == ADDRESSOF case, in that it's
      possible it's something we could handle.  However, most cases falling
      into this are dealing with transparent unions, which are slightly
      weird. */
  if (rhs.type == ADDRESSOF && !(get_varinfo (rhs.var)->is_special_var))
    {
      rhs.type = ADDRESSOF;
      rhs.var = anything_id;
    }

  /* If the RHS is a special var, or an addressof, set all the LHS fields to
     that special var.  */
  if (rhs.var <= integer_id)
    {
      for (p = get_varinfo (lhs.var); p; p = p->next)
        {
          struct constraint_expr templhs = lhs;
          struct constraint_expr temprhs = rhs;

          if (templhs.type == SCALAR )
            templhs.var = p->id;
          else
            templhs.offset += p->offset;
          process_constraint (new_constraint (templhs, temprhs));
        }
    }
  else
    {
      tree rhstype = TREE_TYPE (rhsop);
      tree lhstype = TREE_TYPE (lhsop);
      tree rhstypesize;
      tree lhstypesize;

      lhstypesize = DECL_P (lhsop) ? DECL_SIZE (lhsop) : TYPE_SIZE (lhstype);
      rhstypesize = DECL_P (rhsop) ? DECL_SIZE (rhsop) : TYPE_SIZE (rhstype);

      /* If we have a variably sized types on the rhs or lhs, and a deref
         constraint, add the constraint, lhsconstraint = &ANYTHING.
         This is conservatively correct because either the lhs is an unknown
         sized var (if the constraint is SCALAR), or the lhs is a DEREF
         constraint, and every variable it can point to must be unknown sized
         anyway, so we don't need to worry about fields at all.  */
      if ((rhs.type == DEREF && TREE_CODE (rhstypesize) != INTEGER_CST)
          || (lhs.type == DEREF && TREE_CODE (lhstypesize) != INTEGER_CST))
        {
          rhs.var = anything_id;
          rhs.type = ADDRESSOF;
          rhs.offset = 0;
          process_constraint (new_constraint (lhs, rhs));
          return;
        }

      /* The size only really matters insofar as we don't set more or less of
         the variable.  If we hit an unknown size var, the size should be the
         whole darn thing.  */
      if (get_varinfo (rhs.var)->is_unknown_size_var)
        rhssize = ~0;
      else
        rhssize = TREE_INT_CST_LOW (rhstypesize);

      if (get_varinfo (lhs.var)->is_unknown_size_var)
        lhssize = ~0;
      else
        lhssize = TREE_INT_CST_LOW (lhstypesize);


      if (rhs.type == SCALAR && lhs.type == SCALAR)
        {
          if (!do_simple_structure_copy (lhs, rhs, MIN (lhssize, rhssize)))
            {
              lhs.var = collapse_rest_of_var (lhs.var);
              rhs.var = collapse_rest_of_var (rhs.var);
              lhs.offset = 0;
              rhs.offset = 0;
              lhs.type = SCALAR;
              rhs.type = SCALAR;
              process_constraint (new_constraint (lhs, rhs));
            }
        }
      else if (lhs.type != DEREF && rhs.type == DEREF)
        do_rhs_deref_structure_copy (lhs, rhs, MIN (lhssize, rhssize));
      else if (lhs.type == DEREF && rhs.type != DEREF)
        do_lhs_deref_structure_copy (lhs, rhs, MIN (lhssize, rhssize));
      else
        {
          tree pointedtotype = lhstype;
          tree tmpvar;

          gcc_assert (rhs.type == DEREF && lhs.type == DEREF);
          tmpvar = create_tmp_var_raw (pointedtotype, "structcopydereftmp");
          do_structure_copy (tmpvar, rhsop);
          do_structure_copy (lhsop, tmpvar);
        }
    }
}


/* Update related alias information kept in AI.  This is used when
   building name tags, alias sets and deciding grouping heuristics.
   STMT is the statement to process.  This function also updates
   ADDRESSABLE_VARS.  */

static void
update_alias_info (tree stmt, struct alias_info *ai)
{
  bitmap addr_taken;
  use_operand_p use_p;
  ssa_op_iter iter;
  bool stmt_dereferences_ptr_p;
  enum escape_type stmt_escape_type = is_escape_site (stmt);
  struct mem_ref_stats_d *mem_ref_stats = gimple_mem_ref_stats (cfun);

  stmt_dereferences_ptr_p = false;

  if (stmt_escape_type == ESCAPE_TO_CALL
      || stmt_escape_type == ESCAPE_TO_PURE_CONST)
    {
      mem_ref_stats->num_call_sites++;
      if (stmt_escape_type == ESCAPE_TO_PURE_CONST)
        mem_ref_stats->num_pure_const_call_sites++;
    }
  else if (stmt_escape_type == ESCAPE_TO_ASM)
    mem_ref_stats->num_asm_sites++;

  /* Mark all the variables whose address are taken by the statement.  */
  addr_taken = addresses_taken (stmt);
  if (addr_taken)
    {
      bitmap_ior_into (gimple_addressable_vars (cfun), addr_taken);

      /* If STMT is an escape point, all the addresses taken by it are
         call-clobbered.  */
      if (stmt_escape_type != NO_ESCAPE)
        {
          bitmap_iterator bi;
          unsigned i;

          EXECUTE_IF_SET_IN_BITMAP (addr_taken, 0, i, bi)
            {
              tree rvar = referenced_var (i);
              if (!unmodifiable_var_p (rvar))
                mark_call_clobbered (rvar, stmt_escape_type);
            }
        }
    }

  /* Process each operand use.  For pointers, determine whether they
     are dereferenced by the statement, or whether their value
     escapes, etc.  */
  FOR_EACH_PHI_OR_STMT_USE (use_p, stmt, iter, SSA_OP_USE)
    {
      tree op, var;
      var_ann_t v_ann;
      struct ptr_info_def *pi;
      unsigned num_uses, num_loads, num_stores;

      op = USE_FROM_PTR (use_p);

      /* If STMT is a PHI node, OP may be an ADDR_EXPR.  If so, add it
         to the set of addressable variables.  */
      if (TREE_CODE (op) == ADDR_EXPR)
        {
          bitmap addressable_vars = gimple_addressable_vars (cfun);

          gcc_assert (TREE_CODE (stmt) == PHI_NODE);
          gcc_assert (addressable_vars);

          /* PHI nodes don't have annotations for pinning the set
             of addresses taken, so we collect them here.

             FIXME, should we allow PHI nodes to have annotations
             so that they can be treated like regular statements?
             Currently, they are treated as second-class
             statements.  */
          add_to_addressable_set (TREE_OPERAND (op, 0), &addressable_vars);
          continue;
        }

      /* Ignore constants (they may occur in PHI node arguments).  */
      if (TREE_CODE (op) != SSA_NAME)
        continue;

      var = SSA_NAME_VAR (op);
      v_ann = var_ann (var);

      /* The base variable of an SSA name must be a GIMPLE register, and thus
         it cannot be aliased.  */
      gcc_assert (!may_be_aliased (var));

      /* We are only interested in pointers.  */
      if (!POINTER_TYPE_P (TREE_TYPE (op)))
        continue;

      pi = get_ptr_info (op);

      /* Add OP to AI->PROCESSED_PTRS, if it's not there already.  */
      if (!TEST_BIT (ai->ssa_names_visited, SSA_NAME_VERSION (op)))
        {
          SET_BIT (ai->ssa_names_visited, SSA_NAME_VERSION (op));
          VEC_safe_push (tree, heap, ai->processed_ptrs, op);
        }

      /* If STMT is a PHI node, then it will not have pointer
         dereferences and it will not be an escape point.  */
      if (TREE_CODE (stmt) == PHI_NODE)
        continue;

      /* Determine whether OP is a dereferenced pointer, and if STMT
         is an escape point, whether OP escapes.  */
      count_uses_and_derefs (op, stmt, &num_uses, &num_loads, &num_stores);

      /* Handle a corner case involving address expressions of the
         form '&PTR->FLD'.  The problem with these expressions is that
         they do not represent a dereference of PTR.  However, if some
         other transformation propagates them into an INDIRECT_REF
         expression, we end up with '*(&PTR->FLD)' which is folded
         into 'PTR->FLD'.

         So, if the original code had no other dereferences of PTR,
         the aliaser will not create memory tags for it, and when
         &PTR->FLD gets propagated to INDIRECT_REF expressions, the
         memory operations will receive no VDEF/VUSE operands.

         One solution would be to have count_uses_and_derefs consider
         &PTR->FLD a dereference of PTR.  But that is wrong, since it
         is not really a dereference but an offset calculation.

         What we do here is to recognize these special ADDR_EXPR
         nodes.  Since these expressions are never GIMPLE values (they
         are not GIMPLE invariants), they can only appear on the RHS
         of an assignment and their base address is always an
         INDIRECT_REF expression.  */
      if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT
          && TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1)) == ADDR_EXPR
          && !is_gimple_val (GIMPLE_STMT_OPERAND (stmt, 1)))
        {
          /* If the RHS if of the form &PTR->FLD and PTR == OP, then
             this represents a potential dereference of PTR.  */
          tree rhs = GIMPLE_STMT_OPERAND (stmt, 1);
          tree base = get_base_address (TREE_OPERAND (rhs, 0));
          if (TREE_CODE (base) == INDIRECT_REF
              && TREE_OPERAND (base, 0) == op)
            num_loads++;
        }

      if (num_loads + num_stores > 0)
        {
          /* Mark OP as dereferenced.  In a subsequent pass,
             dereferenced pointers that point to a set of
             variables will be assigned a name tag to alias
             all the variables OP points to.  */
          pi->is_dereferenced = 1;

          /* If this is a store operation, mark OP as being
             dereferenced to store, otherwise mark it as being
             dereferenced to load.  */
          if (num_stores > 0)
            pointer_set_insert (ai->dereferenced_ptrs_store, var);
          else
            pointer_set_insert (ai->dereferenced_ptrs_load, var);

          /* Update the frequency estimate for all the dereferences of
             pointer OP.  */
          update_mem_sym_stats_from_stmt (op, stmt, num_loads, num_stores);

          /* Indicate that STMT contains pointer dereferences.  */
          stmt_dereferences_ptr_p = true;
        }

      if (stmt_escape_type != NO_ESCAPE && num_loads + num_stores < num_uses)
        {
          /* If STMT is an escape point and STMT contains at
             least one direct use of OP, then the value of OP
             escapes and so the pointed-to variables need to
             be marked call-clobbered.  */
          pi->value_escapes_p = 1;
          pi->escape_mask |= stmt_escape_type;

          /* If the statement makes a function call, assume
             that pointer OP will be dereferenced in a store
             operation inside the called function.  */
          if (get_call_expr_in (stmt)
              || stmt_escape_type == ESCAPE_STORED_IN_GLOBAL)
            {
              pointer_set_insert (ai->dereferenced_ptrs_store, var);
              pi->is_dereferenced = 1;
            }
        }
    }

  if (TREE_CODE (stmt) == PHI_NODE)
    return;

  /* Mark stored variables in STMT as being written to and update the
     memory reference stats for all memory symbols referenced by STMT.  */
  if (stmt_references_memory_p (stmt))
    {
      unsigned i;
      bitmap_iterator bi;

      mem_ref_stats->num_mem_stmts++;

      /* Notice that we only update memory reference stats for symbols
         loaded and stored by the statement if the statement does not
         contain pointer dereferences and it is not a call/asm site.
         This is to avoid double accounting problems when creating
         memory partitions.  After computing points-to information,
         pointer dereference statistics are used to update the
         reference stats of the pointed-to variables, so here we
         should only update direct references to symbols.

         Indirect references are not updated here for two reasons: (1)
         The first time we compute alias information, the sets
         LOADED/STORED are empty for pointer dereferences, (2) After
         partitioning, LOADED/STORED may have references to
         partitions, not the original pointed-to variables.  So, if we
         always counted LOADED/STORED here and during partitioning, we
         would count many symbols more than once.

         This does cause some imprecision when a statement has a
         combination of direct symbol references and pointer
         dereferences (e.g., MEMORY_VAR = *PTR) or if a call site has
         memory symbols in its argument list, but these cases do not
         occur so frequently as to constitute a serious problem.  */
      if (STORED_SYMS (stmt))
        EXECUTE_IF_SET_IN_BITMAP (STORED_SYMS (stmt), 0, i, bi)
          {
            tree sym = referenced_var (i);
            pointer_set_insert (ai->written_vars, sym);
            if (!stmt_dereferences_ptr_p
                && stmt_escape_type != ESCAPE_TO_CALL
                && stmt_escape_type != ESCAPE_TO_PURE_CONST
                && stmt_escape_type != ESCAPE_TO_ASM)
              update_mem_sym_stats_from_stmt (sym, stmt, 0, 1);
          }

      if (!stmt_dereferences_ptr_p
          && LOADED_SYMS (stmt)
          && stmt_escape_type != ESCAPE_TO_CALL
          && stmt_escape_type != ESCAPE_TO_PURE_CONST
          && stmt_escape_type != ESCAPE_TO_ASM)
        EXECUTE_IF_SET_IN_BITMAP (LOADED_SYMS (stmt), 0, i, bi)
          update_mem_sym_stats_from_stmt (referenced_var (i), stmt, 1, 0);
    }
}


/* Handle pointer arithmetic EXPR when creating aliasing constraints.
   Expressions of the type PTR + CST can be handled in two ways:

   1- If the constraint for PTR is ADDRESSOF for a non-structure
      variable, then we can use it directly because adding or
      subtracting a constant may not alter the original ADDRESSOF
      constraint (i.e., pointer arithmetic may not legally go outside
      an object's boundaries).

   2- If the constraint for PTR is ADDRESSOF for a structure variable,
      then if CST is a compile-time constant that can be used as an
      offset, we can determine which sub-variable will be pointed-to
      by the expression.

   Return true if the expression is handled.  For any other kind of
   expression, return false so that each operand can be added as a
   separate constraint by the caller.  */

static bool
handle_ptr_arith (VEC (ce_s, heap) *lhsc, tree expr)
{
  tree op0, op1;
  struct constraint_expr *c, *c2;
  unsigned int i = 0;
  unsigned int j = 0;
  VEC (ce_s, heap) *temp = NULL;
  unsigned int rhsoffset = 0;
  bool unknown_addend = false;

  if (TREE_CODE (expr) != POINTER_PLUS_EXPR)
    return false;

  op0 = TREE_OPERAND (expr, 0);
  op1 = TREE_OPERAND (expr, 1);
  gcc_assert (POINTER_TYPE_P (TREE_TYPE (op0)));

  get_constraint_for (op0, &temp);

  /* Handle non-constants by making constraints from integer.  */
  if (TREE_CODE (op1) == INTEGER_CST)
    rhsoffset = TREE_INT_CST_LOW (op1) * BITS_PER_UNIT;
  else
    unknown_addend = true;

  for (i = 0; VEC_iterate (ce_s, lhsc, i, c); i++)
    for (j = 0; VEC_iterate (ce_s, temp, j, c2); j++)
      {
        if (c2->type == ADDRESSOF && rhsoffset != 0)
          {
            varinfo_t temp = get_varinfo (c2->var);

            /* An access one after the end of an array is valid,
               so simply punt on accesses we cannot resolve.  */
            temp = first_vi_for_offset (temp, rhsoffset);
            if (temp == NULL)
              continue;
            c2->var = temp->id;
            c2->offset = 0;
          }
        else if (unknown_addend)
          {
            /* Can't handle *a + integer where integer is unknown.  */
            if (c2->type != SCALAR)
              {
                struct constraint_expr intc;
                intc.var = integer_id;
                intc.offset = 0;
                intc.type = SCALAR;
                process_constraint (new_constraint (*c, intc));
              }
            else
              {
                /* We known it lives somewhere within c2->var.  */
                varinfo_t tmp = get_varinfo (c2->var);
                for (; tmp; tmp = tmp->next)
                  {
                    struct constraint_expr tmpc = *c2;
                    c2->var = tmp->id;
                    c2->offset = 0;
                    process_constraint (new_constraint (*c, tmpc));
                  }
              }
          }
        else
          c2->offset = rhsoffset;
        process_constraint (new_constraint (*c, *c2));
      }

  VEC_free (ce_s, heap, temp);

  return true;
}

/* For non-IPA mode, generate constraints necessary for a call on the
   RHS.  */

static void
handle_rhs_call  (tree rhs)
{
  tree arg;
  call_expr_arg_iterator iter;
  struct constraint_expr rhsc;

  rhsc.var = anything_id;
  rhsc.offset = 0;
  rhsc.type = ADDRESSOF;

  FOR_EACH_CALL_EXPR_ARG (arg, iter, rhs)
    {
      VEC(ce_s, heap) *lhsc = NULL;

      /* Find those pointers being passed, and make sure they end up
         pointing to anything.  */
      if (POINTER_TYPE_P (TREE_TYPE (arg)))
        {
          unsigned int j;
          struct constraint_expr *lhsp;

          get_constraint_for (arg, &lhsc);
          do_deref (&lhsc);
          for (j = 0; VEC_iterate (ce_s, lhsc, j, lhsp); j++)
            process_constraint_1 (new_constraint (*lhsp, rhsc), true);
          VEC_free (ce_s, heap, lhsc);
        }
    }
}

/* For non-IPA mode, generate constraints necessary for a call
   that returns a pointer and assigns it to LHS.  This simply makes
   the LHS point to anything.  */

static void
handle_lhs_call (tree lhs)
{
  VEC(ce_s, heap) *lhsc = NULL;
  struct constraint_expr rhsc;
  unsigned int j;
  struct constraint_expr *lhsp;

  rhsc.var = anything_id;
  rhsc.offset = 0;
  rhsc.type = ADDRESSOF;
  get_constraint_for (lhs, &lhsc);
  for (j = 0; VEC_iterate (ce_s, lhsc, j, lhsp); j++)
    process_constraint_1 (new_constraint (*lhsp, rhsc), true);
  VEC_free (ce_s, heap, lhsc);
}

/* Walk statement T setting up aliasing constraints according to the
   references found in T.  This function is the main part of the
   constraint builder.  AI points to auxiliary alias information used
   when building alias sets and computing alias grouping heuristics.  */

static void
find_func_aliases (tree origt)
{
  tree t = origt;
  VEC(ce_s, heap) *lhsc = NULL;
  VEC(ce_s, heap) *rhsc = NULL;
  struct constraint_expr *c;

  if (TREE_CODE (t) == RETURN_EXPR && TREE_OPERAND (t, 0))
    t = TREE_OPERAND (t, 0);

  /* Now build constraints expressions.  */
  if (TREE_CODE (t) == PHI_NODE)
    {
      gcc_assert (!AGGREGATE_TYPE_P (TREE_TYPE (PHI_RESULT (t))));

      /* Only care about pointers and structures containing
         pointers.  */
      if (could_have_pointers (PHI_RESULT (t)))
        {
          int i;
          unsigned int j;

          /* For a phi node, assign all the arguments to
             the result.  */
          get_constraint_for (PHI_RESULT (t), &lhsc);
          for (i = 0; i < PHI_NUM_ARGS (t); i++)
            {
              tree rhstype;
              tree strippedrhs = PHI_ARG_DEF (t, i);

              STRIP_NOPS (strippedrhs);
              rhstype = TREE_TYPE (strippedrhs);
              get_constraint_for (PHI_ARG_DEF (t, i), &rhsc);

              for (j = 0; VEC_iterate (ce_s, lhsc, j, c); j++)
                {
                  struct constraint_expr *c2;
                  while (VEC_length (ce_s, rhsc) > 0)
                    {
                      c2 = VEC_last (ce_s, rhsc);
                      process_constraint (new_constraint (*c, *c2));
                      VEC_pop (ce_s, rhsc);
                    }
                }
            }
        }
    }
  /* In IPA mode, we need to generate constraints to pass call
     arguments through their calls.   There are two cases, either a
     GIMPLE_MODIFY_STMT when we are returning a value, or just a plain
     CALL_EXPR when we are not.

     In non-ipa mode, we need to generate constraints for each
     pointer passed by address.  */
  else if (((TREE_CODE (t) == GIMPLE_MODIFY_STMT
             && TREE_CODE (GIMPLE_STMT_OPERAND (t, 1)) == CALL_EXPR
             && !(call_expr_flags (GIMPLE_STMT_OPERAND (t, 1))
                  & (ECF_MALLOC | ECF_MAY_BE_ALLOCA)))
            || (TREE_CODE (t) == CALL_EXPR
                && !(call_expr_flags (t)
                     & (ECF_MALLOC | ECF_MAY_BE_ALLOCA)))))
    {
      if (!in_ipa_mode)
        {
          if (TREE_CODE (t) == GIMPLE_MODIFY_STMT)
            {
              handle_rhs_call (GIMPLE_STMT_OPERAND (t, 1));
              if (POINTER_TYPE_P (TREE_TYPE (GIMPLE_STMT_OPERAND (t, 1))))
                handle_lhs_call (GIMPLE_STMT_OPERAND (t, 0));
            }
          else
            handle_rhs_call (t);
        }
      else
        {
          tree lhsop;
          tree rhsop;
          tree arg;
          call_expr_arg_iterator iter;
          varinfo_t fi;
          int i = 1;
          tree decl;
          if (TREE_CODE (t) == GIMPLE_MODIFY_STMT)
            {
              lhsop = GIMPLE_STMT_OPERAND (t, 0);
              rhsop = GIMPLE_STMT_OPERAND (t, 1);
            }
          else
            {
              lhsop = NULL;
              rhsop = t;
            }
          decl = get_callee_fndecl (rhsop);

          /* If we can directly resolve the function being called, do so.
             Otherwise, it must be some sort of indirect expression that
             we should still be able to handle.  */
          if (decl)
            {
              fi = get_vi_for_tree (decl);
            }
          else
            {
              decl = CALL_EXPR_FN (rhsop);
              fi = get_vi_for_tree (decl);
            }

          /* Assign all the passed arguments to the appropriate incoming
             parameters of the function.  */

          FOR_EACH_CALL_EXPR_ARG (arg, iter, rhsop)
            {
              struct constraint_expr lhs ;
              struct constraint_expr *rhsp;

              get_constraint_for (arg, &rhsc);
              if (TREE_CODE (decl) != FUNCTION_DECL)
                {
                  lhs.type = DEREF;
                  lhs.var = fi->id;
                  lhs.offset = i;
                }
              else
                {
                  lhs.type = SCALAR;
                  lhs.var = first_vi_for_offset (fi, i)->id;
                  lhs.offset = 0;
                }
              while (VEC_length (ce_s, rhsc) != 0)
                {
                  rhsp = VEC_last (ce_s, rhsc);
                  process_constraint (new_constraint (lhs, *rhsp));
                  VEC_pop (ce_s, rhsc);
                }
              i++;
            }

          /* If we are returning a value, assign it to the result.  */
          if (lhsop)
            {
              struct constraint_expr rhs;
              struct constraint_expr *lhsp;
              unsigned int j = 0;

              get_constraint_for (lhsop, &lhsc);
              if (TREE_CODE (decl) != FUNCTION_DECL)
                {
                  rhs.type = DEREF;
                  rhs.var = fi->id;
                  rhs.offset = i;
                }
              else
                {
                  rhs.type = SCALAR;
                  rhs.var = first_vi_for_offset (fi, i)->id;
                  rhs.offset = 0;
                }
              for (j = 0; VEC_iterate (ce_s, lhsc, j, lhsp); j++)
                process_constraint (new_constraint (*lhsp, rhs));
            }
        }
    }
  /* Otherwise, just a regular assignment statement.  */
  else if (TREE_CODE (t) == GIMPLE_MODIFY_STMT)
    {
      tree lhsop = GIMPLE_STMT_OPERAND (t, 0);
      tree rhsop = GIMPLE_STMT_OPERAND (t, 1);
      int i;

      if ((AGGREGATE_TYPE_P (TREE_TYPE (lhsop))
           || TREE_CODE (TREE_TYPE (lhsop)) == COMPLEX_TYPE)
          && (AGGREGATE_TYPE_P (TREE_TYPE (rhsop))
              || TREE_CODE (TREE_TYPE (lhsop)) == COMPLEX_TYPE))
        {
          do_structure_copy (lhsop, rhsop);
        }
      else
        {
          /* Only care about operations with pointers, structures
             containing pointers, dereferences, and call expressions.  */
          if (could_have_pointers (lhsop)
              || TREE_CODE (rhsop) == CALL_EXPR)
            {
              get_constraint_for (lhsop, &lhsc);
              switch (TREE_CODE_CLASS (TREE_CODE (rhsop)))
                {
                  /* RHS that consist of unary operations,
                     exceptional types, or bare decls/constants, get
                     handled directly by get_constraint_for.  */
                  case tcc_reference:
                  case tcc_declaration:
                  case tcc_constant:
                  case tcc_exceptional:
                  case tcc_expression:
                  case tcc_vl_exp:
                  case tcc_unary:
                      {
                        unsigned int j;

                        get_constraint_for (rhsop, &rhsc);
                        for (j = 0; VEC_iterate (ce_s, lhsc, j, c); j++)
                          {
                            struct constraint_expr *c2;
                            unsigned int k;

                            for (k = 0; VEC_iterate (ce_s, rhsc, k, c2); k++)
                              process_constraint (new_constraint (*c, *c2));
                          }

                      }
                    break;

                  case tcc_binary:
                      {
                        /* For pointer arithmetic of the form
                           PTR + CST, we can simply use PTR's
                           constraint because pointer arithmetic is
                           not allowed to go out of bounds.  */
                        if (handle_ptr_arith (lhsc, rhsop))
                          break;
                      }
                    /* FALLTHRU  */

                  /* Otherwise, walk each operand.  Notice that we
                     can't use the operand interface because we need
                     to process expressions other than simple operands
                     (e.g. INDIRECT_REF, ADDR_EXPR, CALL_EXPR).  */
                  default:
                    for (i = 0; i < TREE_OPERAND_LENGTH (rhsop); i++)
                      {
                        tree op = TREE_OPERAND (rhsop, i);
                        unsigned int j;

                        gcc_assert (VEC_length (ce_s, rhsc) == 0);
                        get_constraint_for (op, &rhsc);
                        for (j = 0; VEC_iterate (ce_s, lhsc, j, c); j++)
                          {
                            struct constraint_expr *c2;
                            while (VEC_length (ce_s, rhsc) > 0)
                              {
                                c2 = VEC_last (ce_s, rhsc);
                                process_constraint (new_constraint (*c, *c2));
                                VEC_pop (ce_s, rhsc);
                              }
                          }
                      }
                }
            }
        }
    }
  else if (TREE_CODE (t) == CHANGE_DYNAMIC_TYPE_EXPR)
    {
      unsigned int j;

      get_constraint_for (CHANGE_DYNAMIC_TYPE_LOCATION (t), &lhsc);
      for (j = 0; VEC_iterate (ce_s, lhsc, j, c); ++j)
        get_varinfo (c->var)->no_tbaa_pruning = true;
    }

  /* After promoting variables and computing aliasing we will
     need to re-scan most statements.  FIXME: Try to minimize the
     number of statements re-scanned.  It's not really necessary to
     re-scan *all* statements.  */
  mark_stmt_modified (origt);
  VEC_free (ce_s, heap, rhsc);
  VEC_free (ce_s, heap, lhsc);
}


/* Find the first varinfo in the same variable as START that overlaps with
   OFFSET.
   Effectively, walk the chain of fields for the variable START to find the
   first field that overlaps with OFFSET.
   Return NULL if we can't find one.  */

static varinfo_t
first_vi_for_offset (varinfo_t start, unsigned HOST_WIDE_INT offset)
{
  varinfo_t curr = start;
  while (curr)
    {
      /* We may not find a variable in the field list with the actual
         offset when when we have glommed a structure to a variable.
         In that case, however, offset should still be within the size
         of the variable. */
      if (offset >= curr->offset && offset < (curr->offset +  curr->size))
        return curr;
      curr = curr->next;
    }
  return NULL;
}


/* Insert the varinfo FIELD into the field list for BASE, at the front
   of the list.  */

static void
insert_into_field_list (varinfo_t base, varinfo_t field)
{
  varinfo_t prev = base;
  varinfo_t curr = base->next;

  field->next = curr;
  prev->next = field;
}

/* Insert the varinfo FIELD into the field list for BASE, ordered by
   offset.  */

static void
insert_into_field_list_sorted (varinfo_t base, varinfo_t field)
{
  varinfo_t prev = base;
  varinfo_t curr = base->next;

  if (curr == NULL)
    {
      prev->next = field;
      field->next = NULL;
    }
  else
    {
      while (curr)
        {
          if (field->offset <= curr->offset)
            break;
          prev = curr;
          curr = curr->next;
        }
      field->next = prev->next;
      prev->next = field;<