2010-04-30 Richard Guenther <rguenther@suse.de>

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

/* Tree based points-to analysis
   Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010
   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 "tree.h"
#include "tree-flow.h"
#include "tree-inline.h"
#include "diagnostic.h"
#include "toplev.h"
#include "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 "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.  */

/* IPA-PTA optimizations possible.

   When the indirect function called is ANYTHING we can add disambiguation
   based on the function signatures (or simply the parameter count which
   is the varinfo size).  We also do not need to consider functions that
   do not have their address taken.

   The is_global_var bit which marks escape points is overly conservative
   in IPA mode.  Split it to is_escape_point and is_global_var - only
   externally visible globals are escape points in IPA mode.  This is
   also needed to fix the pt_solution_includes_global predicate
   (and thus ptr_deref_may_alias_global_p).

   The way we introduce DECL_PT_UID to avoid fixing up all points-to
   sets in the translation unit when we copy a DECL during inlining
   pessimizes precision.  The advantage is that the DECL_PT_UID keeps
   compile-time and memory usage overhead low - the points-to sets
   do not grow or get unshared as they would during a fixup phase.
   An alternative solution is to delay IPA PTA until after all
   inlining transformations have been applied.

   The way we propagate clobber/use information isn't optimized.
   It should use a new complex constraint that properly filters
   out local variables of the callee (though that would make
   the sets invalid after inlining).  OTOH we might as well
   admit defeat to WHOPR and simply do all the clobber/use analysis
   and propagation after PTA finished but before we threw away
   points-to information for memory variables.  WHOPR and PTA
   do not play along well anyway - the whole constraint solving
   would need to be done in WPA phase and it will be very interesting
   to apply the results to local SSA names during LTRANS phase.

   We probably should compute a per-function unit-ESCAPE solution
   propagating it simply like the clobber / uses solutions.  The
   solution can go alongside the non-IPA espaced solution and be
   used to query which vars escape the unit through a function.

   We never put function decls in points-to sets so we do not
   keep the set of called functions for indirect calls.

   And probably more.  */

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);

struct constraint;
typedef struct constraint *constraint_t;

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;

  /* 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 (sub-)fields that represent a whole variable.  */
  unsigned int is_full_var : 1;

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

  /* True if this is a variable tracking a restrict pointer source.  */
  unsigned int is_restrict_var : 1;

  /* True if this field may contain pointers.  */
  unsigned int may_have_pointers : 1;

  /* True if this field has only restrict qualified pointers.  */
  unsigned int only_restrict_pointers : 1;

  /* True if this represents a global variable.  */
  unsigned int is_global_var : 1;

  /* True if this represents a IPA function info.  */
  unsigned int is_fn_info : 1;

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

  /* 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;

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

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

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

  /* Old points-to set for this variable.  */
  bitmap oldsolution;
};
typedef struct variable_info *varinfo_t;

static varinfo_t first_vi_for_offset (varinfo_t, unsigned HOST_WIDE_INT);
static varinfo_t first_or_preceding_vi_for_offset (varinfo_t,
                                                   unsigned HOST_WIDE_INT);
static varinfo_t lookup_vi_for_tree (tree);

/* 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);
}

/* Static IDs for the special variables.  */
enum { nothing_id = 0, anything_id = 1, readonly_id = 2,
       escaped_id = 3, nonlocal_id = 4,
       storedanything_id = 5, integer_id = 6 };

struct GTY(()) heapvar_map {
  struct tree_map map;
  unsigned HOST_WIDE_INT offset;
};

static int
heapvar_map_eq (const void *p1, const void *p2)
{
  const struct heapvar_map *h1 = (const struct heapvar_map *)p1;
  const struct heapvar_map *h2 = (const struct heapvar_map *)p2;
  return (h1->map.base.from == h2->map.base.from
          && h1->offset == h2->offset);
}

static unsigned int
heapvar_map_hash (struct heapvar_map *h)
{
  return iterative_hash_host_wide_int (h->offset,
                                       htab_hash_pointer (h->map.base.from));
}

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

static tree
heapvar_lookup (tree from, unsigned HOST_WIDE_INT offset)
{
  struct heapvar_map *h, in;
  in.map.base.from = from;
  in.offset = offset;
  h = (struct heapvar_map *) htab_find_with_hash (heapvar_for_stmt, &in,
                                                  heapvar_map_hash (&in));
  if (h)
    return h->map.to;
  return NULL_TREE;
}

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

static void
heapvar_insert (tree from, unsigned HOST_WIDE_INT offset, tree to)
{
  struct heapvar_map *h;
  void **loc;

  h = GGC_NEW (struct heapvar_map);
  h->map.base.from = from;
  h->offset = offset;
  h->map.hash = heapvar_map_hash (h);
  h->map.to = to;
  loc = htab_find_slot_with_hash (heapvar_for_stmt, h, h->map.hash, INSERT);
  gcc_assert (*loc == NULL);
  *(struct heapvar_map **) loc = h;
}

/* Return a new variable info structure consisting for a variable
   named NAME, and using constraint graph node NODE.  Append it
   to the vector of variable info structures.  */

static varinfo_t
new_var_info (tree t, const char *name)
{
  unsigned index = VEC_length (varinfo_t, varmap);
  varinfo_t ret = (varinfo_t) pool_alloc (variable_info_pool);

  ret->id = index;
  ret->name = name;
  ret->decl = t;
  /* Vars without decl are artificial and do not have sub-variables.  */
  ret->is_artificial_var = (t == NULL_TREE);
  ret->is_special_var = false;
  ret->is_unknown_size_var = false;
  ret->is_full_var = (t == NULL_TREE);
  ret->is_heap_var = false;
  ret->is_restrict_var = false;
  ret->may_have_pointers = true;
  ret->only_restrict_pointers = false;
  ret->is_global_var = (t == NULL_TREE);
  ret->is_fn_info = false;
  if (t && DECL_P (t))
    ret->is_global_var = is_global_var (t);
  ret->solution = BITMAP_ALLOC (&pta_obstack);
  ret->oldsolution = BITMAP_ALLOC (&oldpta_obstack);
  ret->next = NULL;

  stats.total_vars++;

  VEC_safe_push (varinfo_t, heap, varmap, ret);

  return ret;
}


/* A map mapping call statements to per-stmt variables for uses
   and clobbers specific to the call.  */
struct pointer_map_t *call_stmt_vars;

/* Lookup or create the variable for the call statement CALL.  */

static varinfo_t
get_call_vi (gimple call)
{
  void **slot_p;
  varinfo_t vi, vi2;

  slot_p = pointer_map_insert (call_stmt_vars, call);
  if (*slot_p)
    return (varinfo_t) *slot_p;

  vi = new_var_info (NULL_TREE, "CALLUSED");
  vi->offset = 0;
  vi->size = 1;
  vi->fullsize = 2;
  vi->is_full_var = true;

  vi->next = vi2 = new_var_info (NULL_TREE, "CALLCLOBBERED");
  vi2->offset = 1;
  vi2->size = 1;
  vi2->fullsize = 2;
  vi2->is_full_var = true;

  *slot_p = (void *) vi;
  return vi;
}

/* Lookup the variable for the call statement CALL representing
   the uses.  Returns NULL if there is nothing special about this call.  */

static varinfo_t
lookup_call_use_vi (gimple call)
{
  void **slot_p;

  slot_p = pointer_map_contains (call_stmt_vars, call);
  if (slot_p)
    return (varinfo_t) *slot_p;

  return NULL;
}

/* Lookup the variable for the call statement CALL representing
   the clobbers.  Returns NULL if there is nothing special about this call.  */

static varinfo_t
lookup_call_clobber_vi (gimple call)
{
  varinfo_t uses = lookup_call_use_vi (call);
  if (!uses)
    return NULL;

  return uses->next;
}

/* Lookup or create the variable for the call statement CALL representing
   the uses.  */

static varinfo_t
get_call_use_vi (gimple call)
{
  return get_call_vi (call);
}

/* Lookup or create the variable for the call statement CALL representing
   the clobbers.  */

static varinfo_t ATTRIBUTE_UNUSED
get_call_clobber_vi (gimple call)
{
  return get_call_vi (call)->next;
}


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.   */
  HOST_WIDE_INT offset;
};

/* Use 0x8000... as special unknown offset.  */
#define UNKNOWN_OFFSET ((HOST_WIDE_INT)-1 << (HOST_BITS_PER_WIDE_INT-1))

typedef struct constraint_expr ce_s;
DEF_VEC_O(ce_s);
DEF_VEC_ALLOC_O(ce_s, heap);
static void get_constraint_for_1 (tree, VEC(ce_s, heap) **, bool);
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;

/* 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;

  /* 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.  */

static 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 (c->lhs.var)->name);
  if (c->lhs.offset == UNKNOWN_OFFSET)
    fprintf (file, " + UNKNOWN");
  else 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 (c->rhs.var)->name);
  if (c->rhs.offset == UNKNOWN_OFFSET)
    fprintf (file, " + UNKNOWN");
  else if (c->rhs.offset != 0)
    fprintf (file, " + " HOST_WIDE_INT_PRINT_DEC, c->rhs.offset);
  fprintf (file, "\n");
}


void debug_constraint (constraint_t);
void debug_constraints (void);
void debug_constraint_graph (void);
void debug_solution_for_var (unsigned int);
void debug_sa_points_to_info (void);

/* Print out constraint C to stderr.  */

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

/* Print out all constraints to FILE */

static void
dump_constraints (FILE *file, int from)
{
  int i;
  constraint_t c;
  for (i = from; 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, 0);
}

/* Print out to FILE the edge in the constraint graph that is created by
   constraint c. The edge may have a label, depending on the type of
   constraint that it represents. If complex1, e.g: a = *b, then the label
   is "=*", if complex2, e.g: *a = b, then the label is "*=", if
   complex with an offset, e.g: a = b + 8, then the label is "+".
   Otherwise the edge has no label.  */

static void
dump_constraint_edge (FILE *file, constraint_t c)
{
  if (c->rhs.type != ADDRESSOF)
    {
      const char *src = get_varinfo (c->rhs.var)->name;
      const char *dst = get_varinfo (c->lhs.var)->name;
      fprintf (file, "  \"%s\" -> \"%s\" ", src, dst);
      /* Due to preprocessing of constraints, instructions like *a = *b are
         illegal; thus, we do not have to handle such cases.  */
      if (c->lhs.type == DEREF)
        fprintf (file, " [ label=\"*=\" ] ;\n");
      else if (c->rhs.type == DEREF)
        fprintf (file, " [ label=\"=*\" ] ;\n");
      else
        {
          /* We must check the case where the constraint is an offset.
             In this case, it is treated as a complex constraint.  */
          if (c->rhs.offset != c->lhs.offset)
            fprintf (file, " [ label=\"+\" ] ;\n");
          else
            fprintf (file, " ;\n");
        }
    }
}

/* Print the constraint graph in dot format.  */

static void
dump_constraint_graph (FILE *file)
{
  unsigned int i=0, size;
  constraint_t c;

  /* Only print the graph if it has already been initialized:  */
  if (!graph)
    return;

  /* Print the constraints used to produce the constraint graph. The
     constraints will be printed as comments in the dot file:  */
  fprintf (file, "\n\n/* Constraints used in the constraint graph:\n");
  dump_constraints (file, 0);
  fprintf (file, "*/\n");

  /* Prints the header of the dot file:  */
  fprintf (file, "\n\n// The constraint graph in dot format:\n");
  fprintf (file, "strict digraph {\n");
  fprintf (file, "  node [\n    shape = box\n  ]\n");
  fprintf (file, "  edge [\n    fontsize = \"12\"\n  ]\n");
  fprintf (file, "\n  // List of nodes in the constraint graph:\n");

  /* The next lines print the nodes in the graph. In order to get the
     number of nodes in the graph, we must choose the minimum between the
     vector VEC (varinfo_t, varmap) and graph->size. If the graph has not
     yet been initialized, then graph->size == 0, otherwise we must only
     read nodes that have an entry in VEC (varinfo_t, varmap).  */
  size = VEC_length (varinfo_t, varmap);
  size = size < graph->size ? size : graph->size;
  for (i = 0; i < size; i++)
    {
      const char *name = get_varinfo (graph->rep[i])->name;
      fprintf (file, "  \"%s\" ;\n", name);
    }

  /* Go over the list of constraints printing the edges in the constraint
     graph.  */
  fprintf (file, "\n  // The constraint edges:\n");
  for (i = 0; VEC_iterate (constraint_t, constraints, i, c); i++)
    if (c)
      dump_constraint_edge (file, c);

  /* Prints the tail of the dot file. By now, only the closing bracket.  */
  fprintf (file, "}\n\n\n");
}

/* Print out the constraint graph to stderr.  */

void
debug_constraint_graph (void)
{
  dump_constraint_graph (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);
        }
    }
}

/* Expands the solution in SET to all sub-fields of variables included.
   Union the expanded result into RESULT.  */

static void
solution_set_expand (bitmap result, bitmap set)
{
  bitmap_iterator bi;
  bitmap vars = NULL;
  unsigned j;

  /* In a first pass record all variables we need to add all
     sub-fields off.  This avoids quadratic behavior.  */
  EXECUTE_IF_SET_IN_BITMAP (set, 0, j, bi)
    {
      varinfo_t v = get_varinfo (j);
      if (v->is_artificial_var
          || v->is_full_var)
        continue;
      v = lookup_vi_for_tree (v->decl);
      if (vars == NULL)
        vars = BITMAP_ALLOC (NULL);
      bitmap_set_bit (vars, v->id);
    }

  /* In the second pass now do the addition to the solution and
     to speed up solving add it to the delta as well.  */
  if (vars != NULL)
    {
      EXECUTE_IF_SET_IN_BITMAP (vars, 0, j, bi)
        {
          varinfo_t v = get_varinfo (j);
          for (; v != NULL; v = v->next)
            bitmap_set_bit (result, v->id);
        }
      BITMAP_FREE (vars);
    }
}

/* 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, HOST_WIDE_INT offset)
{
  bitmap result = BITMAP_ALLOC (&iteration_obstack);
  unsigned int i;
  bitmap_iterator bi;

  /* If the offset is unknown we have to expand the solution to
     all subfields.  */
  if (offset == UNKNOWN_OFFSET)
    {
      solution_set_expand (set, set);
      return;
    }

  EXECUTE_IF_SET_IN_BITMAP (set, 0, i, bi)
    {
      varinfo_t vi = get_varinfo (i);

      /* If this is a variable with just one field just set its bit
         in the result.  */
      if (vi->is_artificial_var
          || vi->is_unknown_size_var
          || vi->is_full_var)
        bitmap_set_bit (result, i);
      else
        {
          unsigned HOST_WIDE_INT fieldoffset = vi->offset + offset;

          /* If the offset makes the pointer point to before the
             variable use offset zero for the field lookup.  */
          if (offset < 0
              && fieldoffset > vi->offset)
            fieldoffset = 0;

          if (offset != 0)
            vi = first_or_preceding_vi_for_offset (vi, fieldoffset);

          bitmap_set_bit (result, vi->id);
          /* If the result is not exactly at fieldoffset include the next
             field as well.  See get_constraint_for_ptr_offset for more
             rationale.  */
          if (vi->offset != fieldoffset
              && vi->next != NULL)
            bitmap_set_bit (result, vi->next->id);
        }
    }

  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, 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_set_bit (graph->implicit_preds[to], from))
    stats.num_implicit_edges++;
}

/* 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);
  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_set_bit (graph->succs[from], to))
        {
          r = true;
          if (to < FIRST_REF_NODE && from < FIRST_REF_NODE)
            stats.num_edges++;
        }
      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->address_taken = BITMAP_ALLOC (&predbitmap_obstack);
  sbitmap_zero (graph->direct_nodes);

  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 = lhs.var;
      unsigned int rhsvar = rhs.var;

      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)
        {
          varinfo_t v;

          /* 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);

          /* All related variables are no longer direct nodes.  */
          RESET_BIT (graph->direct_nodes, rhsvar);
          v = get_varinfo (rhsvar);
          if (!v->is_full_var)
            {
              v = lookup_vi_for_tree (v->decl);
              do
                {
                  RESET_BIT (graph->direct_nodes, v->id);
                  v = v->next;
                }
              while (v != NULL);
            }
          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)
{
  unsigned i, t;
  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 (lhs.var);
      rhsvar = find (rhs.var);

      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 (rhs.var) == rhs.var);
          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);
        }
    }

  /* Add edges from STOREDANYTHING to all non-direct nodes that can
     receive pointers.  */
  t = find (storedanything_id);
  for (i = integer_id + 1; i < FIRST_REF_NODE; ++i)
    {
      if (!TEST_BIT (graph->direct_nodes, i)
          && get_varinfo (i)->may_have_pointers)
        add_graph_edge (graph, find (i), t);
    }

  /* Everything stored to ANYTHING also potentially escapes.  */
  add_graph_edge (graph, find (escaped_id), t);
}


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

/* 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);
          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);
            }

          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);

  /* 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);
}

/* Process a constraint C that represents x = *(y + off), using DELTA as the
   starting solution for y.  */

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;
  HOST_WIDE_INT roffset = c->rhs.offset;

  /* Our IL does not allow this.  */
  gcc_assert (c->lhs.offset == 0);

  /* If the solution of Y contains anything it is good enough to transfer
     this to the LHS.  */
  if (bitmap_bit_p (delta, anything_id))
    {
      flag |= bitmap_set_bit (sol, anything_id);
      goto done;
    }

  /* If we do not know at with offset the rhs is dereferenced compute
     the reachability set of DELTA, conservatively assuming it is
     dereferenced at all valid offsets.  */
  if (roffset == UNKNOWN_OFFSET)
    {
      solution_set_expand (delta, delta);
      /* No further offset processing is necessary.  */
      roffset = 0;
    }

  /* 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)
    {
      varinfo_t v = get_varinfo (j);
      HOST_WIDE_INT fieldoffset = v->offset + roffset;
      unsigned int t;

      if (v->is_full_var)
        fieldoffset = v->offset;
      else if (roffset != 0)
        v = first_vi_for_offset (v, fieldoffset);
      /* If the access is outside of the variable we can ignore it.  */
      if (!v)
        continue;

      do
        {
          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);
          /* Merging the solution from ESCAPED needlessly increases
             the set.  Use ESCAPED as representative instead.  */
          else if (v->id == escaped_id)
            flag |= bitmap_set_bit (sol, escaped_id);
          else if (v->may_have_pointers
                   && add_graph_edge (graph, lhs, t))
            flag |= bitmap_ior_into (sol, get_varinfo (t)->solution);

          /* If the variable is not exactly at the requested offset
             we have to include the next one.  */
          if (v->offset == (unsigned HOST_WIDE_INT)fieldoffset
              || v->next == NULL)
            break;

          v = v->next;
          fieldoffset = v->offset;
        }
      while (1);
    }

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 + off) = y using DELTA
   as the starting solution for x.  */

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;
  HOST_WIDE_INT loff = c->lhs.offset;
  bool escaped_p = false;

  /* Our IL does not allow this.  */
  gcc_assert (c->rhs.offset == 0);

  /* If the solution of y contains ANYTHING simply use the ANYTHING
     solution.  This avoids needlessly increasing the points-to sets.  */
  if (bitmap_bit_p (sol, anything_id))
    sol = get_varinfo (find (anything_id))->solution;

  /* If the solution for x contains ANYTHING we have to merge the
     solution of y into all pointer variables which we do via
     STOREDANYTHING.  */
  if (bitmap_bit_p (delta, anything_id))
    {
      unsigned t = find (storedanything_id);
      if (add_graph_edge (graph, t, rhs))
        {
          if (bitmap_ior_into (get_varinfo (t)->solution, sol))
            {
              if (!TEST_BIT (changed, t))
                {
                  SET_BIT (changed, t);
                  changed_count++;
                }
            }
        }
      return;
    }

  /* If we do not know at with offset the rhs is dereferenced compute
     the reachability set of DELTA, conservatively assuming it is
     dereferenced at all valid offsets.  */
  if (loff == UNKNOWN_OFFSET)
    {
      solution_set_expand (delta, delta);
      loff = 0;
    }

  /* 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)
    {
      varinfo_t v = get_varinfo (j);
      unsigned int t;
      HOST_WIDE_INT fieldoffset = v->offset + loff;

      if (v->is_full_var)
        fieldoffset = v->offset;
      else if (loff != 0)
        v = first_vi_for_offset (v, fieldoffset);
      /* If the access is outside of the variable we can ignore it.  */
      if (!v)
        continue;

      do
        {
          if (v->may_have_pointers)
            {
              /* If v is a global variable then this is an escape point.  */
              if (v->is_global_var
                  && !escaped_p)
                {
                  t = find (escaped_id);
                  if (add_graph_edge (graph, t, rhs)
                      && bitmap_ior_into (get_varinfo (t)->solution, sol)
                      && !TEST_BIT (changed, t))
                    {
                      SET_BIT (changed, t);
                      changed_count++;
                    }
                  /* Enough to let rhs escape once.  */
                  escaped_p = true;
                }

              if (v->is_special_var)
                break;

              t = find (v->id);
              if (add_graph_edge (graph, t, rhs)
                  && bitmap_ior_into (get_varinfo (t)->solution, sol)
                  && !TEST_BIT (changed, t))
                {
                  SET_BIT (changed, t);
                  changed_count++;
                }
            }

          /* If the variable is not exactly at the requested offset
             we have to include the next one.  */
          if (v->offset == (unsigned HOST_WIDE_INT)fieldoffset
              || v->next == NULL)
            break;

          v = v->next;
          fieldoffset = v->offset;
        }
      while (1);
    }
}

/* 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
{
  hashval_t hashcode;
  unsigned int equivalence_class;
  bitmap labels;
} *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 (eql1->hashcode == eql2->hashcode
          && 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]);
            }
        }
      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)
        continue;

      if (graph->points_to[w])
        bitmap_ior_into(graph->points_to[n], 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)
        {
          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->eq_rep);
  sbitmap_free (graph->direct_nodes);
  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 (lhs.var);
      unsigned int rhsvar = find (rhs.var);
      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;
                  unsigned eff_escaped_id = find (escaped_id);

                  /* 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;

                      /* If we propagate from ESCAPED use ESCAPED as
                         placeholder.  */
                      if (i == eff_escaped_id)
                        flag = bitmap_set_bit (tmp, escaped_id);
                      else
                        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 scalar constraint expression for a new temporary variable.  */

static struct constraint_expr
new_scalar_tmp_constraint_exp (const char *name)
{
  struct constraint_expr tmp;
  varinfo_t vi;

  vi = new_var_info (NULL_TREE, name);
  vi->offset = 0;
  vi->size = -1;
  vi->fullsize = -1;
  vi->is_full_var = 1;

  tmp.var = vi->id;
  tmp.type = SCALAR;
  tmp.offset = 0;

  return tmp;
}

/* Get a constraint expression vector from an SSA_VAR_P node.
   If address_p is true, the result will be taken its address of.  */

static void
get_constraint_for_ssa_var (tree t, VEC(ce_s, heap) **results, bool address_p)
{
  struct constraint_expr cexpr;
  varinfo_t vi;

  /* We allow FUNCTION_DECLs here even though it doesn't make much sense.  */
  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))
    {
      get_constraint_for_ssa_var (SSA_NAME_VAR (t), results, address_p);
      return;
    }

  vi = get_vi_for_tree (t);
  cexpr.var = vi->id;
  cexpr.type = SCALAR;
  cexpr.offset = 0;
  /* 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))
    {
      gcc_unreachable ();
      cexpr.type = ADDRESSOF;
      cexpr.var = readonly_id;
    }

  /* If we are not taking the address of the constraint expr, add all
     sub-fiels of the variable as well.  */
  if (!address_p
      && !vi->is_full_var)
    {
      for (; vi; vi = vi->next)
        {
          cexpr.var = vi->id;
          VEC_safe_push (ce_s, heap, *results, &cexpr);
        }
      return;
    }

  VEC_safe_push (ce_s, heap, *results, &cexpr);
}

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

static void
process_constraint (constraint_t t)
{
  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 we didn't get any useful constraint from the lhs we get
     &ANYTHING as fallback from get_constraint_for.  Deal with
     it here by turning it into *ANYTHING.  */
  if (lhs.type == ADDRESSOF
      && lhs.var == anything_id)
    lhs.type = DEREF;

  /* ADDRESSOF on the lhs is invalid.  */
  gcc_assert (lhs.type != ADDRESSOF);

  /* We shouldn't add constraints from things that cannot have pointers.
     It's not completely trivial to avoid in the callers, so do it here.  */
  if (rhs.type != ADDRESSOF
      && !get_varinfo (rhs.var)->may_have_pointers)
    return;

  /* Likewise adding to the solution of a non-pointer var isn't useful.  */
  if (!get_varinfo (lhs.var)->may_have_pointers)
    return;

  /* This can happen in our IR with things like n->a = *p */
  if (rhs.type == DEREF && lhs.type == DEREF && rhs.var != anything_id)
    {
      /* Split into tmp = *rhs, *lhs = tmp */
      struct constraint_expr tmplhs;
      tmplhs = new_scalar_tmp_constraint_exp ("doubledereftmp");
      process_constraint (new_constraint (tmplhs, rhs));
      process_constraint (new_constraint (lhs, tmplhs));
    }
  else if (rhs.type == ADDRESSOF && lhs.type == DEREF)
    {
      /* Split into tmp = &rhs, *lhs = tmp */
      struct constraint_expr tmplhs;
      tmplhs = new_scalar_tmp_constraint_exp ("derefaddrtmp");
      process_constraint (new_constraint (tmplhs, rhs));
      process_constraint (new_constraint (lhs, tmplhs));
    }
  else
    {
      gcc_assert (rhs.type != ADDRESSOF || rhs.offset == 0);
      VEC_safe_push (constraint_t, heap, constraints, t);
    }
}

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

static bool
type_could_have_pointers (tree type)
{
  if (POINTER_TYPE_P (type))
    return true;

  if (TREE_CODE (type) == ARRAY_TYPE)
    return type_could_have_pointers (TREE_TYPE (type));

  return AGGREGATE_TYPE_P (type);
}

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

static bool
could_have_pointers (tree t)
{
  return type_could_have_pointers (TREE_TYPE (t));
}

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

static HOST_WIDE_INT
bitpos_of_field (const tree fdecl)
{

  if (!host_integerp (DECL_FIELD_OFFSET (fdecl), 0)
      || !host_integerp (DECL_FIELD_BIT_OFFSET (fdecl), 0))
    return -1;

  return (TREE_INT_CST_LOW (DECL_FIELD_OFFSET (fdecl)) * 8
          + TREE_INT_CST_LOW (DECL_FIELD_BIT_OFFSET (fdecl)));
}


/* Get constraint expressions for offsetting PTR by OFFSET.  Stores the
   resulting constraint expressions in *RESULTS.  */

static void
get_constraint_for_ptr_offset (tree ptr, tree offset,
                               VEC (ce_s, heap) **results)
{
  struct constraint_expr c;
  unsigned int j, n;
  HOST_WIDE_INT rhsunitoffset, rhsoffset;

  /* If we do not do field-sensitive PTA adding offsets to pointers
     does not change the points-to solution.  */
  if (!use_field_sensitive)
    {
      get_constraint_for (ptr, results);
      return;
    }

  /* If the offset is not a non-negative integer constant that fits
     in a HOST_WIDE_INT, we have to fall back to a conservative
     solution which includes all sub-fields of all pointed-to
     variables of ptr.  */
  if (offset == NULL_TREE
      || !host_integerp (offset, 0))
    rhsoffset = UNKNOWN_OFFSET;
  else
    {
      /* Make sure the bit-offset also fits.  */
      rhsunitoffset = TREE_INT_CST_LOW (offset);
      rhsoffset = rhsunitoffset * BITS_PER_UNIT;
      if (rhsunitoffset != rhsoffset / BITS_PER_UNIT)
        rhsoffset = UNKNOWN_OFFSET;
    }

  get_constraint_for (ptr, results);
  if (rhsoffset == 0)
    return;

  /* As we are eventually appending to the solution do not use
     VEC_iterate here.  */
  n = VEC_length (ce_s, *results);
  for (j = 0; j < n; j++)
    {
      varinfo_t curr;
      c = *VEC_index (ce_s, *results, j);
      curr = get_varinfo (c.var);

      if (c.type == ADDRESSOF
          /* If this varinfo represents a full variable just use it.  */
          && curr->is_full_var)
        c.offset = 0;
      else if (c.type == ADDRESSOF
               /* If we do not know the offset add all subfields.  */
               && rhsoffset == UNKNOWN_OFFSET)
        {
          varinfo_t temp = lookup_vi_for_tree (curr->decl);
          do
            {
              struct constraint_expr c2;
              c2.var = temp->id;
              c2.type = ADDRESSOF;
              c2.offset = 0;
              if (c2.var != c.var)
                VEC_safe_push (ce_s, heap, *results, &c2);
              temp = temp->next;
            }
          while (temp);
        }
      else if (c.type == ADDRESSOF)
        {
          varinfo_t temp;
          unsigned HOST_WIDE_INT offset = curr->offset + rhsoffset;

          /* Search the sub-field which overlaps with the
             pointed-to offset.  If the result is outside of the variable
             we have to provide a conservative result, as the variable is
             still reachable from the resulting pointer (even though it
             technically cannot point to anything).  The last and first
             sub-fields are such conservative results.
             ???  If we always had a sub-field for &object + 1 then
             we could represent this in a more precise way.  */
          if (rhsoffset < 0
              && curr->offset < offset)
            offset = 0;
          temp = first_or_preceding_vi_for_offset (curr, offset);

          /* If the found variable is not exactly at the pointed to
             result, we have to include the next variable in the
             solution as well.  Otherwise two increments by offset / 2
             do not result in the same or a conservative superset
             solution.  */
          if (temp->offset != offset
              && temp->next != NULL)
            {
              struct constraint_expr c2;
              c2.var = temp->next->id;
              c2.type = ADDRESSOF;
              c2.offset = 0;
              VEC_safe_push (ce_s, heap, *results, &c2);
            }
          c.var = temp->id;
          c.offset = 0;
        }
      else
        c.offset = rhsoffset;

      VEC_replace (ce_s, *results, j, &c);
    }
}


/* Given a COMPONENT_REF T, return the constraint_expr vector for it.
   If address_p is true the result will be taken its address of.  */

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

  /* Some people like to do cute things like take the address of
     &0->a.b */
  forzero = t;
  while (handled_component_p (forzero)
         || INDIRECT_REF_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);

  /* Pretend to take the address of the base, we'll take care of
     adding the required subset of sub-fields below.  */
  get_constraint_for_1 (t, results, true);
  gcc_assert (VEC_length (ce_s, *results) == 1);
  result = VEC_last (ce_s, *results);

  if (result->type == SCALAR
      && get_varinfo (result->var)->is_full_var)
    /* For single-field vars do not bother about the offset.  */
    result->offset = 0;
  else 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 ((unsigned HOST_WIDE_INT)bitpos < 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.  */
          struct constraint_expr cexpr = *result;
          varinfo_t curr;
          VEC_pop (ce_s, *results);
          cexpr.offset = 0;
          for (curr = get_varinfo (cexpr.var); curr; curr = curr->next)
            {
              if (ranges_overlap_p (curr->offset, curr->size,
                                    bitpos, bitmaxsize))
                {
                  cexpr.var = curr->id;
                  VEC_safe_push (ce_s, heap, *results, &cexpr);
                  if (address_p)
                    break;
                }
            }
          /* If we are going to take the address of this field then
             to be able to compute reachability correctly add at least
             the last field of the variable.  */
          if (address_p
              && VEC_length (ce_s, *results) == 0)
            {
              curr = get_varinfo (cexpr.var);
              while (curr->next != NULL)
                curr = curr->next;
              cexpr.var = curr->id;
              VEC_safe_push (ce_s, heap, *results, &cexpr);
            }
          else
            /* 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 (VEC_length (ce_s, *results) >= 1
                        || 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");
    }
  else if (result->type == DEREF)
    {
      /* If we do not know exactly where the access goes say so.  Note
         that only for non-structure accesses we know that we access
         at most one subfiled of any variable.  */
      if (bitpos == -1
          || bitsize != bitmaxsize
          || AGGREGATE_TYPE_P (TREE_TYPE (orig_t)))
        result->offset = UNKNOWN_OFFSET;
      else
        result->offset = bitpos;
    }
  else if (result->type == ADDRESSOF)
    {
      /* We can end up here for component references on a
         VIEW_CONVERT_EXPR <>(&foobar).  */
      result->type = SCALAR;
      result->var = anything_id;
      result->offset = 0;
    }
  else
    gcc_unreachable ();
}


/* 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)
        {
          struct constraint_expr tmplhs;
          tmplhs = new_scalar_tmp_constraint_exp ("dereftmp");
          process_constraint (new_constraint (tmplhs, *c));
          c->var = tmplhs.var;
        }
      else
        gcc_unreachable ();
    }
}

static void get_constraint_for_1 (tree, VEC (ce_s, heap) **, bool);

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

static void
get_constraint_for_address_of (tree t, VEC (ce_s, heap) **results)
{
  struct constraint_expr *c;
  unsigned int i;

  get_constraint_for_1 (t, results, true);

  for (i = 0; VEC_iterate (ce_s, *results, i, c); i++)
    {
      if (c->type == DEREF)
        c->type = SCALAR;
      else
        c->type = ADDRESSOF;
    }
}

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

static void
get_constraint_for_1 (tree t, VEC (ce_s, heap) **results, bool address_p)
{
  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.

     Do not do that if -fno-delete-null-pointer-checks though, because
     in that case *NULL does not fail, so it _should_ alias *anything.
     It is not worth adding a new option or renaming the existing one,
     since this case is relatively obscure.  */
  if (flag_delete_null_pointer_checks
      && ((TREE_CODE (t) == INTEGER_CST
           && integer_zerop (t))
          /* The only valid CONSTRUCTORs in gimple with pointer typed
             elements are zero-initializer.  But in IPA mode we also
             process global initializers, so verify at least.  */
          || (TREE_CODE (t) == CONSTRUCTOR
              && CONSTRUCTOR_NELTS (t) == 0)))
    {
      temp.var = nothing_id;
      temp.type = ADDRESSOF;
      temp.offset = 0;
      VEC_safe_push (ce_s, heap, *results, &temp);
      return;
    }

  /* String constants are read-only.  */
  if (TREE_CODE (t) == STRING_CST)
    {
      temp.var = readonly_id;
      temp.type = SCALAR;
      temp.offset = 0;
      VEC_safe_push (ce_s, heap, *results, &temp);
      return;
    }

  switch (TREE_CODE_CLASS (TREE_CODE (t)))
    {
    case tcc_expression:
      {
        switch (TREE_CODE (t))
          {
          case ADDR_EXPR:
            get_constraint_for_address_of (TREE_OPERAND (t, 0), results);
            return;
          default:;
          }
        break;
      }
    case tcc_reference:
      {
        switch (TREE_CODE (t))
          {
          case INDIRECT_REF:
            {
              get_constraint_for_1 (TREE_OPERAND (t, 0), results, address_p);
              do_deref (results);
              return;
            }
          case ARRAY_REF:
          case ARRAY_RANGE_REF:
          case COMPONENT_REF:
            get_constraint_for_component_ref (t, results, address_p);
            return;
          case VIEW_CONVERT_EXPR:
            get_constraint_for_1 (TREE_OPERAND (t, 0), results, address_p);
            return;
          /* We are missing handling for TARGET_MEM_REF here.  */
          default:;
          }
        break;
      }
    case tcc_exceptional:
      {
        switch (TREE_CODE (t))
          {
          case SSA_NAME:
            {
              get_constraint_for_ssa_var (t, results, address_p);
              return;
            }
          case CONSTRUCTOR:
            {
              unsigned int i;
              tree val;
              VEC (ce_s, heap) *tmp = NULL;
              FOR_EACH_CONSTRUCTOR_VALUE (CONSTRUCTOR_ELTS (t), i, val)
                {
                  struct constraint_expr *rhsp;
                  unsigned j;
                  get_constraint_for_1 (val, &tmp, address_p);
                  for (j = 0; VEC_iterate (ce_s, tmp, j, rhsp); ++j)
                    VEC_safe_push (ce_s, heap, *results, rhsp);
                  VEC_truncate (ce_s, tmp, 0);
                }
              VEC_free (ce_s, heap, tmp);
              /* We do not know whether the constructor was complete,
                 so technically we have to add &NOTHING or &ANYTHING
                 like we do for an empty constructor as well.  */
              return;
            }
          default:;
          }
        break;
      }
    case tcc_declaration:
      {
        get_constraint_for_ssa_var (t, results, address_p);
        return;
      }
    default:;
    }

  /* The default fallback is a constraint from anything.  */
  temp.type = ADDRESSOF;
  temp.var = anything_id;
  temp.offset = 0;
  VEC_safe_push (ce_s, heap, *results, &temp);
}

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

static void
get_constraint_for (tree t, VEC (ce_s, heap) **results)
{
  gcc_assert (VEC_length (ce_s, *results) == 0);

  get_constraint_for_1 (t, results, false);
}


/* Efficiently generates constraints from all entries in *RHSC to all
   entries in *LHSC.  */

static void
process_all_all_constraints (VEC (ce_s, heap) *lhsc, VEC (ce_s, heap) *rhsc)
{
  struct constraint_expr *lhsp, *rhsp;
  unsigned i, j;

  if (VEC_length (ce_s, lhsc) <= 1
      || VEC_length (ce_s, rhsc) <= 1)
    {
      for (i = 0; VEC_iterate (ce_s, lhsc, i, lhsp); ++i)
        for (j = 0; VEC_iterate (ce_s, rhsc, j, rhsp); ++j)
          process_constraint (new_constraint (*lhsp, *rhsp));
    }
  else
    {
      struct constraint_expr tmp;
      tmp = new_scalar_tmp_constraint_exp ("allalltmp");
      for (i = 0; VEC_iterate (ce_s, rhsc, i, rhsp); ++i)
        process_constraint (new_constraint (tmp, *rhsp));
      for (i = 0; VEC_iterate (ce_s, lhsc, i, lhsp); ++i)
        process_constraint (new_constraint (*lhsp, tmp));
    }
}

/* 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 *lhsp, *rhsp;
  VEC (ce_s, heap) *lhsc = NULL, *rhsc = NULL;
  unsigned j;

  get_constraint_for (lhsop, &lhsc);
  get_constraint_for (rhsop, &rhsc);
  lhsp = VEC_index (ce_s, lhsc, 0);
  rhsp = VEC_index (ce_s, rhsc, 0);
  if (lhsp->type == DEREF
      || (lhsp->type == ADDRESSOF && lhsp->var == anything_id)
      || rhsp->type == DEREF)
    {
      if (lhsp->type == DEREF)
        {
          gcc_assert (VEC_length (ce_s, lhsc) == 1);
          lhsp->offset = UNKNOWN_OFFSET;
        }
      if (rhsp->type == DEREF)
        {
          gcc_assert (VEC_length (ce_s, rhsc) == 1);
          rhsp->offset = UNKNOWN_OFFSET;
        }
      process_all_all_constraints (lhsc, rhsc);
    }
  else if (lhsp->type == SCALAR
           && (rhsp->type == SCALAR
               || rhsp->type == ADDRESSOF))
    {
      HOST_WIDE_INT lhssize, lhsmaxsize, lhsoffset;
      HOST_WIDE_INT rhssize, rhsmaxsize, rhsoffset;
      unsigned k = 0;
      get_ref_base_and_extent (lhsop, &lhsoffset, &lhssize, &lhsmaxsize);
      get_ref_base_and_extent (rhsop, &rhsoffset, &rhssize, &rhsmaxsize);
      for (j = 0; VEC_iterate (ce_s, lhsc, j, lhsp);)
        {
          varinfo_t lhsv, rhsv;
          rhsp = VEC_index (ce_s, rhsc, k);
          lhsv = get_varinfo (lhsp->var);
          rhsv = get_varinfo (rhsp->var);
          if (lhsv->may_have_pointers
              && ranges_overlap_p (lhsv->offset + rhsoffset, lhsv->size,
                                   rhsv->offset + lhsoffset, rhsv->size))
            process_constraint (new_constraint (*lhsp, *rhsp));
          if (lhsv->offset + rhsoffset + lhsv->size
              > rhsv->offset + lhsoffset + rhsv->size)
            {
              ++k;
              if (k >= VEC_length (ce_s, rhsc))
                break;
            }
          else