Merge from the pain train

[official-gcc.git] / gcc / tree-ssa-structalias.c

  /* Tree based points-to analysis
   Copyright (C) 2002, 2003, 2004 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 2 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; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "ggc.h"
#include "obstack.h"
#include "bitmap.h"
#include "tree-ssa-structalias.h"
#include "flags.h"
#include "rtl.h"
#include "tm_p.h"
#include "hard-reg-set.h"
#include "basic-block.h"
#include "output.h"
#include "errors.h"
#include "expr.h"
#include "diagnostic.h"
#include "tree.h"
#include "c-common.h"
#include "tree-flow.h"
#include "tree-inline.h"
#include "varray.h"
#include "c-tree.h"
#include "tree-gimple.h"
#include "hashtab.h"
#include "function.h"
#include "cgraph.h"
#include "tree-pass.h"
#include "timevar.h"
#include "alloc-pool.h"
#include "splay-tree.h"

/* 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. 
   There are three types of constraint expressions, DEREF, ADDRESSOF, and
   SCALAR.  Each constraint expression consists of a 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 apepars on the LHS or the RHS of a statement.
   
   Each variable in the program is assigned an integer id, and each field of a
   variable is assigned an integer id as well.   
   Variables are linked to their fields and vice versa.
   Each variable with subfields has a next pointer, that points to the next
   field (ordered by offset, then size).  Each subfield is it's own variable
   as well, and has a pointer back to the ultimate containing variable,
   through the base pointer.
   The size field tells the size in bits of each portion of a multi-field
   variable 
   (for scalars, size is the size of the entire variable as well), and the
   fullsize field tells us the size in bits of the entire variable.
   The offset field contains the offset, in bits, from the base.

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

   looks like

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

   
   After constructing constraints, we put them into a constraint graph, where
   the edges of the graph represent copy constraints (SCALAR-> SCALAR
   constraints).
   We then perform static cycle elimination on the constraint graph, as well
   as off-line variable substitution.
   Finally, we solve the constraint graph, producing our points-to solutions.
   
   TODO: For extra speed in iterations, we should sort types so that types
   with their address taken come first.

   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 field
   number 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 can add
   fields to them at solve time.  We could do this with some work.
   This may significantly slow the solver, however.
   We'll have to investigate.

   TODO: Use malloc vectors and a bitmap obstack, not ggc_alloc'd things.
   Also, we allocate a lot of bitmaps we don't need.  */
static unsigned int create_variable_info_for (tree, const char *);
static struct constraint_expr get_constraint_for (tree);
static void build_constraint_graph (void);

DEF_VEC_GC_P(constraint_t);
static struct constraint_stats
{
  unsigned int total_vars;
  unsigned int collapsed_vars;
  unsigned int unified_vars_static;
  unsigned int unified_vars_dynamic;
  unsigned int iterations;
} stats;

struct variable_info
{
  /* ID of this variable  */
  unsigned int id;
  /* Name of this variable */
  const char *name;
  /* Tree that this variable is associated with.  */
  tree decl;
  struct variable_info *base;
  /* Offset of this variable, in bits, from the base variable  */
  unsigned HOST_WIDE_INT offset;  
  /* Size of the variable, in bits.  */
  unsigned HOST_WIDE_INT size;
  /* Full size of the base variable, in bits.  */
  unsigned HOST_WIDE_INT fullsize;
  /* A link to the variable for the next field in this structure.  */
  struct variable_info *next;
  /* Node in the graph that represents the constraints and points-to
     solution for the variable.  */
  unsigned int node;
  /* True if the address of this variable is taken.  Needed for
     rountev-chandra.  */
  unsigned int address_taken:1;
  /* True if this variable is the target of a dereference.  Needed for
     rountev-chandra.  */
  unsigned int indirect_target:1;
  /* True if this is a variable created by the constraint analysis, such as
     heap variables and constraints we had to break up.  */
  unsigned int is_artificial_var:1;
  /* Because we punt on union vars right now, we have to identify them so that
     we can mark them as not type safe. */
  unsigned int is_unknown_size_var:1;  
  /* Points-to set for this variable.  */
  bitmap solution;
  /* Variable ids represented by this variable node.  */
  bitmap variables;
  /* Vector of complex constraints for this node.  Complex
     constraints are those involving dereferences.  */
  VEC(constraint_t) *complicated;
};
typedef struct variable_info *varinfo_t;

static varinfo_t first_vi_for_offset (varinfo_t, unsigned HOST_WIDE_INT);
static varinfo_t next_vi_for_offset (varinfo_t, unsigned HOST_WIDE_INT);

/* Pool of variable info structures.  */
static alloc_pool variable_info_pool;
DEF_VEC_GC_P (varinfo_t);
static VEC(varinfo_t) *varmap;
#define get_varinfo(n) VEC_index(varinfo_t, varmap, n)

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

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

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

/* Variable that represents integers.  */
static varinfo_t var_integer;
static tree integer_tree;
static unsigned int integer_id;

/* Return a new variable info structure consisting for a variable
   named NAME, ending at id END, and using constraint graph node
   NODE.  */
static varinfo_t
new_var_info (tree t, unsigned int id, const char *name, unsigned int node)
{
  varinfo_t ret = pool_alloc (variable_info_pool);
  ret->id = id;
  ret->name = name;
  ret->decl = t;
  ret->node = node;
  ret->address_taken = false;
  ret->indirect_target = false;
  ret->is_artificial_var = false;
  ret->is_unknown_size_var = false;
  ret->solution = BITMAP_GGC_ALLOC ();
  bitmap_clear (ret->solution);
  ret->variables = BITMAP_GGC_ALLOC ();
  bitmap_clear (ret->variables);
  ret->complicated = NULL;
  ret->next = NULL;
  return ret;
}

typedef enum {SCALAR, DEREF, ADDRESSOF} constraint_expr_type;

/* An expression that appears in a constraint.  */
struct constraint_expr 
{
  /* Constraint type.  */
  constraint_expr_type type;
  /* Variable we are referring to in the constraint.  */
  unsigned int var;
  /* Offset is in bits */
  unsigned HOST_WIDE_INT offset;
};

static struct constraint_expr do_deref (struct constraint_expr);

/* Constraints are made up of two constraint expressions, one LHS, and one
   RHS.  */
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) *constraints;
static alloc_pool constraint_pool;

/* An edge in the constraint graph.  We technically have no use for
   the src, since it will always be the same node that we are indexing
   into the pred/succ arrays with, but it's nice for checking
   purposes. 
   The edges are weighted, with a bit set in weights if we have an edge with
   that weight.  */
struct constraint_edge
{
  unsigned int src;
  unsigned int dest;
  bitmap weights;
};

typedef struct constraint_edge *constraint_edge_t;
static alloc_pool constraint_edge_pool;

/* Return a new constraint edge from SRC to DEST.  */
static constraint_edge_t
new_constraint_edge (unsigned int src, unsigned int dest)
{
  constraint_edge_t ret = pool_alloc (constraint_edge_pool);
  ret->src = src;
  ret->dest = dest;
  ret->weights = NULL;
  return ret;
}

DEF_VEC_GC_P (constraint_edge_t);

/* The constraint graph is simply a set of adjacency vectors, one per
   variable. succs[x] is the vector of successors for variable x, and preds[x]
   is the vector of predecessors for variable x.  */
struct constraint_graph
{
  VEC(constraint_edge_t) **succs;
  VEC(constraint_edge_t) **preds;
};

typedef struct constraint_graph *constraint_graph_t;

static constraint_graph_t graph;

/* 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 = pool_alloc (constraint_pool);
  ret->lhs = lhs;
  ret->rhs = rhs;
  return ret;
}

/* Print out constraint C to FILE.  */

void
print_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 != 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 != 0)
    fprintf (file, "+ " HOST_WIDE_INT_PRINT_DEC, c->rhs.offset);
  fprintf (file, "\n");
}
void
debug_constraint (constraint_t c)
{
  print_constraint (stdout, c);
}

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

void
debug_constraints (void)
{
  print_constraints (stdout);
}

/* Map from trees to variable ids.  */    
static htab_t id_for_tree;

typedef struct tree_id
{
  tree t;
  unsigned int id;
} *tree_id_t;

static hashval_t 
tree_id_hash (const void *p)
{
  const tree_id_t ta = (tree_id_t) p;
  return htab_hash_pointer (ta->t);
}

static int
tree_id_eq (const void *p1, const void *p2)
{
  const tree_id_t ta1 = (tree_id_t) p1;
  const tree_id_t ta2 = (tree_id_t) p2;
  return ta1->t == ta2->t;
}

/* Insert ID as the variable id for tree T in the hashtable.  */
static void 
insert_id_for_tree (tree t, int id)
{
  void **slot;
  struct tree_id finder;
  tree_id_t new_pair;
  
  finder.t = t;
  slot = htab_find_slot (id_for_tree, &finder, INSERT);
  gcc_assert (*slot == NULL);
  new_pair = xmalloc (sizeof (struct tree_id));
  new_pair->t = t;
  new_pair->id = id;
  *slot = (void *)new_pair;
}

#if 0
/* Find the variable ID for tree T in the hashtable.  */
static unsigned int
lookup_id_for_tree (tree t)
{
  tree_id_t pair;
  struct tree_id finder;
  finder.t = t;
  pair = htab_find (id_for_tree,  &finder);
  gcc_assert (pair != NULL);
  return pair->id;
}
#endif

/* Find the variable ID for tree T in the hashtable.  */
static unsigned int
get_id_for_tree (tree t)
{
  tree_id_t pair;
  struct tree_id finder;
  finder.t = t;
  pair = htab_find (id_for_tree,  &finder);
  if (pair == NULL)
    return create_variable_info_for (t, alias_get_name (t));
  
  return pair->id;
}

/* Get a constraint expression from an SSA_VAR_P node.  */
static struct constraint_expr
get_constraint_exp_from_ssa_var (tree t)
{
  struct constraint_expr cexpr;

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

  if (TREE_CODE (t) == SSA_NAME 
      && TREE_CODE (SSA_NAME_VAR (t)) == PARM_DECL 
      && default_def (SSA_NAME_VAR (t)) == t
      /*&& POINTER_TYPE_P (TREE_TYPE (t))*/)
    return get_constraint_exp_from_ssa_var (SSA_NAME_VAR (t));

  cexpr.type = SCALAR;

  if (DECL_P (t) 
      && is_global_var (t)
      && !TREE_READONLY (t))
    {
      cexpr.type = ADDRESSOF;
      cexpr.var = anything_id;
    }
  else if (TREE_READONLY (t))
    {
      cexpr.type = ADDRESSOF;
      cexpr.var = readonly_id;
    }
  else
    cexpr.var = get_id_for_tree (t);    
    
  cexpr.offset = 0;
  return cexpr;
}

/* Process a completed constraint T, and add it to the constraint
   list.  NEEDEXPAND is true if we need to expand this into the constraints
   for all fields with this offset. */

static void
process_constraint (constraint_t t, bool needexpand)
{
  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));

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

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

      /* Unless this is an unknown size var, we should have passed this off
         to do_structure_copy, and it should have broken it up.  */
      gcc_assert (!AGGREGATE_TYPE_P (pointedtotype) 
                  || get_varinfo (rhs.var)->is_unknown_size_var);
      
      process_constraint (new_constraint (tmplhs, rhs), needexpand);
      process_constraint (new_constraint (lhs, tmplhs), needexpand);
    }
  else if (rhs.type == ADDRESSOF)
    {
      varinfo_t vi;
      gcc_assert (rhs.offset == 0);
      
      for (vi = get_varinfo (rhs.var); vi != NULL; vi = vi->next)
        vi->address_taken = true;

      VEC_safe_push (constraint_t, constraints, t);
    }
  else
    {
      if (lhs.type != DEREF && rhs.type == DEREF)
        get_varinfo (lhs.var)->indirect_target = true;
      VEC_safe_push (constraint_t, constraints, t);
    }
}


/* Return the position, in bits, of FIELD_DECL from the beginning of it's
   structure.  */

static unsigned HOST_WIDE_INT
bitpos_of_field (const tree fdecl)
{
  return (tree_low_cst (DECL_FIELD_OFFSET (fdecl), 1) * 8) 
    + tree_low_cst (DECL_FIELD_BIT_OFFSET (fdecl), 1);
}

/* Given a component ref, return the constraint_expr for it.  */

static struct constraint_expr
get_constraint_for_component_ref (tree t)
{
  struct constraint_expr result;
  HOST_WIDE_INT bitsize;
  HOST_WIDE_INT bitpos;
  tree offset;
  enum machine_mode mode;
  int unsignedp;
  int volatilep;
  tree forzero;
  
  result.offset = 0;
  result.type = SCALAR;
  result.var = 0;
  forzero = t;
  while (!SSA_VAR_P (forzero) && !CONSTANT_CLASS_P (forzero))
    {
      forzero = TREE_OPERAND (forzero, 0);
    }

  if (CONSTANT_CLASS_P (forzero) && integer_zerop (forzero)) 
    {
      result.offset = 0;
      result.var = integer_id;
      result.type = SCALAR;
      return result;
    }
  t = get_inner_reference (t, &bitsize, &bitpos, &offset, &mode,
                           &unsignedp, &volatilep, false);
  result = get_constraint_for (t);

  /* Errf. No point in doing something weird here.  */
  if (TREE_CODE (t) != ADDR_EXPR && result.type == ADDRESSOF)
    result.type = SCALAR;
  
  if (offset == NULL && bitsize != -1)
    {
      result.offset = bitpos;
    }   
  else
    {
      /* MAY NEED TO CHANGE THIS TO PROCESS A CONSTRAINT FROM RESULT.VAR TO
         ANYTHING.  */
      result.var = anything_id;
      result.offset = 0;      
    }

  if (result.type == SCALAR)
    {
      result.var = first_vi_for_offset (get_varinfo (result.var), 
                                        result.offset)->id;
      result.offset= 0;
    }
  
  return result;
}

/* 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 struct constraint_expr
do_deref (struct constraint_expr cons)
{
  if (cons.type == SCALAR)
    {
      cons.type = DEREF;
      return cons;
    }
  else if (cons.type == ADDRESSOF)
    {
      cons.type = SCALAR;
      return cons;
    }
  else if (cons.type == DEREF)
    {
      tree tmpvar = create_tmp_var_raw (ptr_type_node, "derefmp");
      struct constraint_expr tmplhs = get_constraint_exp_from_ssa_var (tmpvar);
      process_constraint (new_constraint (tmplhs, cons), true);
      cons.var = tmplhs.var;
      return cons;
    }
  gcc_unreachable ();
}

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

static struct constraint_expr
get_constraint_for (tree t)
{
  struct constraint_expr temp;

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

  switch (TREE_CODE_CLASS (TREE_CODE (t)))
    {
    case tcc_expression:
      {
        switch (TREE_CODE (t))
          {
          case ADDR_EXPR:
            {
              temp = get_constraint_for (TREE_OPERAND (t, 0));
               if (temp.type == DEREF)
                 temp.type = SCALAR;
               else
                 temp.type = ADDRESSOF;
              return temp;
            }
          case CALL_EXPR:
            
            /* FIXME: Pointers directly passed to calls need to have *pointer =
               &ANYTHING added, things with their address taken need to have x
               = &ANYTHING added.
               At least until we do interprocedural analysis
            */

            if (call_expr_flags (t) & (ECF_MALLOC | ECF_MAY_BE_ALLOCA))
              {
                tree heapvar = create_tmp_var_raw (ptr_type_node, "HEAP");
                temp.var = create_variable_info_for (heapvar,
                                                     alias_get_name (heapvar));
                
                get_varinfo (temp.var)->is_artificial_var = 1;
                temp.type = ADDRESSOF;
                temp.offset = 0;
                return temp;
              }
          default:
            {
              temp.type = ADDRESSOF;
              temp.var = anything_id;
              temp.offset = 0;
              return temp;
            }
          }
      }
    case tcc_reference:
      {
        switch (TREE_CODE (t))
          {
          case INDIRECT_REF:
            {
              temp = get_constraint_for (TREE_OPERAND (t, 0));
              temp = do_deref (temp);
              return temp;
            }
          case ARRAY_REF:
          case COMPONENT_REF:
            temp = get_constraint_for_component_ref (t);
            return temp;
            /*      return get_constraint_for (get_base_address (t));*/
          default:
            {
              temp.type = ADDRESSOF;
              temp.var = anything_id;
              temp.offset = 0;
              return temp;
            }
          }
      }
    case tcc_unary:
      {
        switch (TREE_CODE (t))
          {
          case NOP_EXPR:
          case CONVERT_EXPR:
          case NON_LVALUE_EXPR:
            {
              tree op = TREE_OPERAND (t, 0);
              
              /* Cast from non-pointer to pointers are bad news for us.
                 Anything else, we see through */
              if (!(POINTER_TYPE_P (TREE_TYPE (t))  &&
                    ! POINTER_TYPE_P (TREE_TYPE (op))))
                return get_constraint_for (op);
            }
          default:
            {
              temp.type = ADDRESSOF;
              temp.var = anything_id;
              temp.offset = 0;
              return temp;
            }
          }
      }
    case tcc_exceptional:
      {
        switch (TREE_CODE (t))
          {
          case PHI_NODE:           
            return get_constraint_for (PHI_RESULT (t));
          case SSA_NAME:
              return get_constraint_exp_from_ssa_var (t);
          default:
            {
              temp.type = ADDRESSOF;
              temp.var = anything_id;
              temp.offset = 0;
              return temp;
            }
          }
      }
    case tcc_declaration:
      return get_constraint_exp_from_ssa_var (t);
    default:
      {
        temp.type = ADDRESSOF;
        temp.var = anything_id;
        temp.offset = 0;
        return temp;
      }
    }
}


/* Handle the structure copy case where we have a simple structure copy
   between LHS and RHS that is of SIZE (in bits) 
  
   For each field of the lhs variable (lhsfield)
     For each field of the rhs variable at lhsfield.offset (rhsfield)
       add the constraint lhsfield = rhsfield
*/

static void
do_simple_structure_copy (const struct constraint_expr lhs,
                          const struct constraint_expr rhs,
                          const unsigned HOST_WIDE_INT size)
{
  varinfo_t p = get_varinfo (lhs.var);
  unsigned HOST_WIDE_INT pstart,last;
  pstart = p->offset;
  last = p->offset + size;
  /* Grrr. O(n^2) for now */
  for (; p && p->offset < last; p = p->next)
    {
      varinfo_t q;
      struct constraint_expr templhs = lhs;
      struct constraint_expr temprhs = rhs;
      unsigned HOST_WIDE_INT fieldoffset;
      templhs.var = p->id;      
      
      q = get_varinfo (temprhs.var);
      fieldoffset = p->offset - pstart;
      
      for (q = first_vi_for_offset (q, fieldoffset);
           q != NULL; 
           q = next_vi_for_offset (q, fieldoffset))
        {
          temprhs.var = q->id;
          process_constraint (new_constraint (templhs, temprhs), false);
        }
    }
}


/* Handle the structure copy case where we have a  structure copy between a
   aggregate on the LHS and a dereference of a pointer on the RHS
   that is of SIZE (in bits) 
  
   For each field of the lhs variable (lhsfield)
       rhs.offset = lhsfield->offset
       add the constraint lhsfield = rhs
*/
static void
do_rhs_deref_structure_copy (const struct constraint_expr lhs,
                             const struct constraint_expr rhs,
                             const unsigned HOST_WIDE_INT size)
{
  varinfo_t p = get_varinfo (lhs.var);
  unsigned HOST_WIDE_INT pstart,last;
  pstart = p->offset;
  last = p->offset + size;

  for (; p && p->offset < last; p = p->next)
    {
      varinfo_t q;
      struct constraint_expr templhs = lhs;
      struct constraint_expr temprhs = rhs;
      unsigned HOST_WIDE_INT fieldoffset;
      if (templhs.type == SCALAR)
        templhs.var = p->id;      
      else
        templhs.offset = p->offset;
      
      q = get_varinfo (temprhs.var);
      fieldoffset = p->offset - pstart;      
      temprhs.offset += fieldoffset;
      process_constraint (new_constraint (templhs, temprhs), false);
    }
}

/* Handle the structure copy case where we have a  structure copy between a
   aggregate on the RHS and a dereference of a pointer on the LHS
   that is of SIZE (in bits) 
  
   For each field of the rhs variable (rhsfield)
       lhs.offset = rhsfield->offset
       add the constraint lhs = rhsfield
*/
static void
do_lhs_deref_structure_copy (const struct constraint_expr lhs,
                             const struct constraint_expr rhs,
                             const unsigned HOST_WIDE_INT size)
{
  varinfo_t p = get_varinfo (rhs.var);
  unsigned HOST_WIDE_INT pstart,last;
  pstart = p->offset;
  last = p->offset + size;

  for (; p && p->offset < last; p = p->next)
    {
      varinfo_t q;
      struct constraint_expr templhs = lhs;
      struct constraint_expr temprhs = rhs;
      unsigned HOST_WIDE_INT fieldoffset;
      if (temprhs.type == SCALAR)
        temprhs.var = p->id;      
      else
        temprhs.offset = p->offset;
      
      q = get_varinfo (templhs.var);
      fieldoffset = p->offset - pstart;      
      templhs.offset += fieldoffset;
      process_constraint (new_constraint (templhs, temprhs), false);
    }
}

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

static void
do_structure_copy (tree lhsop, tree rhsop)
{
  struct constraint_expr lhs, rhs, tmp;
  varinfo_t p;
  unsigned HOST_WIDE_INT lhssize;
  unsigned HOST_WIDE_INT rhssize;

  lhssize = TREE_INT_CST_LOW (TYPE_SIZE (TREE_TYPE (lhsop)));
  rhssize = TREE_INT_CST_LOW (TYPE_SIZE (TREE_TYPE (rhsop)));
  lhs = get_constraint_for (lhsop);  
  rhs = get_constraint_for (rhsop);
  
  /* If we have special var = x, swap it around.  */
  if (lhs.var <= integer_id && rhs.var > integer_id)
    {
      tmp = lhs;
      lhs = rhs;
      rhs = tmp;
    }
  
  /* If the RHS is a special var, set all the LHS fields to that special var*/
  if (rhs.var <= integer_id)
    {
      for (p = get_varinfo (lhs.var); p; p = p->next)
        {
          struct constraint_expr templhs = lhs;
          struct constraint_expr temprhs = rhs;
          if (templhs.type == SCALAR )
            templhs.var = p->id;
          else
            templhs.offset += p->offset;
          process_constraint (new_constraint (templhs, temprhs), false);
        }
    }
  else
    {
      
      if (rhs.type == SCALAR && lhs.type == SCALAR)  
        do_simple_structure_copy (lhs, rhs, MIN (lhssize, rhssize));
      else if (lhs.type != DEREF && rhs.type == DEREF)
        do_rhs_deref_structure_copy (lhs, rhs, MIN (lhssize, rhssize));
      else if (lhs.type == DEREF && rhs.type != DEREF)
        do_lhs_deref_structure_copy (lhs, rhs, MIN (lhssize, rhssize));
      else
        {
          tree rhsdecl = get_varinfo (rhs.var)->decl;
          tree pointertype = TREE_TYPE (rhsdecl);
          tree pointedtotype = TREE_TYPE (pointertype);
          tree tmpvar;
          gcc_assert (rhs.type == DEREF && lhs.type == DEREF);
          tmpvar = create_tmp_var_raw (pointedtotype, "structcopydereftmp");

          lhs = get_constraint_for (tmpvar);
          do_rhs_deref_structure_copy (lhs, rhs, MIN (lhssize, rhssize));
          rhs = lhs;
          lhs = get_constraint_for (lhsop);
          do_lhs_deref_structure_copy (lhs, rhs, MIN (lhssize, rhssize));
        }
    }
}

/*  Tree walker that is the heart of the aliasing infrastructure.
    TP is a pointer to the current tree.
    WALK_SUBTREES specifies whether to continue traversing subtrees or
    not.
    Returns NULL_TREE when we should stop.
    
    This function is the main part of the aliasing infrastructure. It
    walks the trees, calling the appropriate alias analyzer functions to process
    various statements.  */

static void
find_func_aliases (tree t)
{
  struct constraint_expr lhs, rhs;
  switch (TREE_CODE (t))
    {      
    case PHI_NODE:
      {
        int i;
        lhs = get_constraint_for (PHI_RESULT (t));
        for (i = 0; i < PHI_NUM_ARGS (t); i++)
          {
            rhs = get_constraint_for (PHI_ARG_DEF (t, i));
            process_constraint (new_constraint (lhs, rhs), true);
          }
      }
      break;
    case MODIFY_EXPR:
      {
        tree lhsop = TREE_OPERAND (t, 0);
        tree rhsop = TREE_OPERAND (t, 1);
        int i;  
        if (AGGREGATE_TYPE_P (TREE_TYPE (lhsop)) 
            && AGGREGATE_TYPE_P (TREE_TYPE (rhsop)))
          {
            do_structure_copy (lhsop, rhsop);
          }
        else
          {
            lhs = get_constraint_for (lhsop);
            switch (TREE_CODE_CLASS (TREE_CODE (rhsop)))
              {
                /* RHS that consist of unary operations, exceptional types, or
                   bare decls/constants, get handled directly by
                   get_constraint_for.  */ 
              case tcc_reference:
              case tcc_declaration:
              case tcc_constant:
              case tcc_exceptional:
              case tcc_expression:
              case tcc_unary:
                {
                  rhs = get_constraint_for (rhsop);
                  process_constraint (new_constraint (lhs, rhs), true);
                }
                break;
                /* other classes, we walk each operator */
              default:
                for (i = 0; i < TREE_CODE_LENGTH (TREE_CODE (rhsop)); i++)
                  {
                    tree op = TREE_OPERAND (rhsop, i);
                    rhs = get_constraint_for (op);
                    process_constraint (new_constraint (lhs, rhs), true);
                  }
              }      
          }
      }
      break;
    default:
      break;
    }
}

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

static varinfo_t 
first_vi_for_offset (varinfo_t start, unsigned HOST_WIDE_INT offset)
{
  varinfo_t curr = start->base;
  while (curr)
    {
      if (offset >= curr->offset && offset < (curr->offset + curr->size))
        return curr;
      curr = curr->next;
    }
  gcc_unreachable ();
}

/* Starting from the variable START, find the *next* variable info in the *same*
   variable that overlaps with OFFSET.
   Effectively, walk the chain of fields starting at START to find the next
   field with that offset.  
   Return NULL if we cannot find one.  */

static varinfo_t
next_vi_for_offset (varinfo_t start, unsigned HOST_WIDE_INT offset)
{
  varinfo_t curr = start->next;
  while (curr)
    {
      if (offset >= curr->offset && offset < (curr->offset + curr->size))
        return curr;
      curr = curr->next;
    }
  return curr;
}

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

   FIXME: We uh, need to do the size comparison, and don't right now.
*/

static void
insert_into_field_list (varinfo_t base, varinfo_t field)
{
  varinfo_t prev = base;
  varinfo_t curr = base->next;
  
  if (curr == NULL)
    {
      prev->next = field;
      field->next = NULL;
    }
  else
    {
      while (curr)
        {
          if (field->offset < (curr->offset + curr->size))
            break;
          prev = curr;
          curr = curr->next;
        }
      field->next = prev->next;
      prev->next = field;
    }
}

/* This structure is simply used during pushing fields onto the fieldstack
   to track the offset of the field, since bitpos_of_field gives it relative
   to it's immediate containing type, and we want it relative to the ultimate
   containing object.  */
typedef struct fieldoff
{
  tree field;
  unsigned HOST_WIDE_INT offset;
} *fieldoff_t;

DEF_VEC_MALLOC_P(fieldoff_t);

static void
push_fields_onto_fieldstack (tree type, VEC (fieldoff_t) **fieldstack, 
                             unsigned HOST_WIDE_INT offset)
{
  fieldoff_t pair;
  tree field = TYPE_FIELDS (type);
  
  if (AGGREGATE_TYPE_P (TREE_TYPE (field)) 
      && TREE_CODE (TREE_TYPE (field)) != ARRAY_TYPE
      && TREE_CODE (field) == FIELD_DECL)
    {
      size_t before = VEC_length (fieldoff_t, *fieldstack);
      /* Empty structures may have actual size, like in C++. So see if we
         actually end up pushing a field, and if not, if the size is non-zero,
         push the field onto the stack */
      push_fields_onto_fieldstack (TREE_TYPE (field), fieldstack, offset);
      if (before == VEC_length (fieldoff_t, *fieldstack)
          && DECL_SIZE (field)
          && !integer_zerop (DECL_SIZE (field)))
        {
          pair = xmalloc (sizeof (struct fieldoff));
          pair->field = field;
          pair->offset = offset;
          VEC_safe_push (fieldoff_t, *fieldstack, pair);
        }
    }
  if (TREE_CODE (field) == FIELD_DECL)
    {
      pair = xmalloc (sizeof (struct fieldoff));
      pair->field = field;
      pair->offset = offset;
      VEC_safe_push (fieldoff_t, *fieldstack, pair);
    }
  for (field = TREE_CHAIN (field); field; field = TREE_CHAIN (field))
    {
      if (TREE_CODE (field) != FIELD_DECL)
        continue;
      if (AGGREGATE_TYPE_P (TREE_TYPE (field)) 
          && TREE_CODE (TREE_TYPE (field)) != ARRAY_TYPE)
        {
          push_fields_onto_fieldstack (TREE_TYPE (field), fieldstack, 
                                       offset + bitpos_of_field (field));
        }
      else
        {
          pair = xmalloc (sizeof (struct fieldoff));
          pair->field = field;
          pair->offset = offset + bitpos_of_field (field);
          VEC_safe_push (fieldoff_t, *fieldstack, pair);
        }
    }
}

/* Free the pairs still on the FIELDSTACK, and then free the FIELDSTACK.  */

static void
cleanup_fieldstack (VEC (fieldoff_t) *fieldstack)
{
  while (VEC_length (fieldoff_t, fieldstack) != 0)
    {
      fieldoff_t pair = VEC_pop (fieldoff_t, fieldstack);
      free (pair);
    }
  VEC_free (fieldoff_t, fieldstack);
}

/* Create a varinfo structure for NAME and DECL, and add it to the varmap.
   This will also create any variable infos necessary for fields of DECL.  */

static unsigned int
create_variable_info_for (tree decl, const char *name)
{
  unsigned int index = VEC_length (varinfo_t, varmap);
  varinfo_t vi;
  tree decltype = TREE_TYPE (decl);
  vi = new_var_info (decl, index, name, index);
  vi->decl = decl;
  vi->base = vi;
  vi->offset = 0;
  if (!TYPE_SIZE (decltype) 
      || TREE_CODE (TYPE_SIZE  (decltype)) != INTEGER_CST
      || TREE_CODE (decltype) == ARRAY_TYPE)
    {
      vi->is_unknown_size_var = true;
      vi->fullsize = ~0;
      vi->size = ~0;
    }
  else
    {
      vi->fullsize = TREE_INT_CST_LOW (TYPE_SIZE (decltype));
      vi->size = vi->fullsize;
    }
  
  insert_id_for_tree (vi->decl, index);  
  VEC_safe_push (varinfo_t, varmap, vi);

  stats.total_vars++;
  if (!vi->is_unknown_size_var && AGGREGATE_TYPE_P (decltype))
    {
      unsigned int newindex = VEC_length (varinfo_t, varmap);
      fieldoff_t pair;
      tree field;
      VEC (fieldoff_t) *fieldstack = NULL;

      push_fields_onto_fieldstack (decltype, &fieldstack, 0);
      /* FIXME: We really want to find the field that would normally go first in
         the list here, not just the "first" field.  That way, the sorting
         always comes out right.  */
      pair = VEC_index (fieldoff_t, fieldstack, 0);
      VEC_replace (fieldoff_t, fieldstack, 0, NULL);
      if (pair == NULL)
        {
          vi->is_unknown_size_var = 1;
          vi->fullsize = ~0;
          vi->size = ~0;
          cleanup_fieldstack (fieldstack);
          return index;
        }
            
      field = pair->field;
      gcc_assert (bitpos_of_field (field) == 0);
      vi->size = TREE_INT_CST_LOW (DECL_SIZE (field));
      while (VEC_length (fieldoff_t, fieldstack) != 0)
        {
          varinfo_t newvi;
          char *newname;
          pair = VEC_pop (fieldoff_t, fieldstack);
          if (pair == NULL)
            continue;
          field = pair->field;
          newindex = VEC_length (varinfo_t, varmap);
          newname = xcalloc (1, strlen (vi->name) + 2
                             + strlen (alias_get_name (field)));
          /*      sprintf (newname, "%s#" HOST_WIDE_INT_PRINT_DEC, name, 
            pair->offset); */
          sprintf (newname, "%s.%s", vi->name, alias_get_name (field));
          newvi = new_var_info (decl, newindex, newname, newindex);
          newvi->base = vi;
          newvi->offset = pair->offset;
          newvi->size = TREE_INT_CST_LOW (DECL_SIZE (field));
          newvi->fullsize = vi->fullsize;
          insert_into_field_list (vi, newvi);
          VEC_safe_push (varinfo_t, varmap, newvi);
          free (pair);
          stats.total_vars++;     
        }
      VEC_free (fieldoff_t, fieldstack);
    }
  return index;
}

/* Print out the points-to solution for VAR to FILE.  */

void
print_solution_for_var (FILE *file, unsigned int var)
{
  varinfo_t vi = get_varinfo (var);
  unsigned int i;
  bitmap_iterator bi; 
  
  fprintf (file, "%s = {", vi->name);
  EXECUTE_IF_SET_IN_BITMAP (get_varinfo (vi->node)->solution, 0, i, bi)
    {
      fprintf (file, "%s,", get_varinfo (i)->name);
    }
  fprintf (file, "}\n");
}

/* Print the points-to solution for VAR to stdout.  */

void
debug_solution_for_var (unsigned int var)
{
  print_solution_for_var (stdout, var);
}

/* Create varinfo structures for all of the variables in the
   function.  */

static void
create_variable_infos (void)
{
  tree t;
#if 0
  tree tmpvar;
  
  tmpvar = create_tmp_var_raw (ptr_type_node, "OUTSIDEOFFUNC");
  i = create_variable_info_for (tmpvar, "OUTSIDEOFFUNC");
  get_varinfo (i)->is_artificial_var = 1;
#endif
  for (t = DECL_ARGUMENTS (current_function_decl);
       t;
       t = TREE_CHAIN (t))
    {
      struct constraint_expr lhs;
      struct constraint_expr rhs;
      size_t lhsvar;
      varinfo_t p;
      
      lhs.offset = 0;
      lhs.type = SCALAR;
      lhs.var  = create_variable_info_for (t, alias_get_name (t));
      
      get_varinfo (lhs.var)->is_artificial_var = true;
#if 0
      rhs.var = lookup_id_for_tree (tmpvar);
#else
      rhs.var = anything_id;
#endif
      rhs.type = ADDRESSOF;
      rhs.offset = 0;
      lhsvar = lhs.var;

      for (p = get_varinfo (lhsvar)->next; p; p = p->next)
        {
          struct constraint_expr temp = lhs;
          temp.var = p->id;
          process_constraint (new_constraint (temp, rhs), false);
        }
    }   

}

/* Return true if two constraint expressions 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 e 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 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) *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) **to,
                      VEC(constraint_t) **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, *to, place, c);
        }
    }
}

/* Take a solution set SET, add OFFSET to each member of the set, 
   and return the result.  */

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

  EXECUTE_IF_SET_IN_BITMAP (set, 0, i, bi)
    {
      /* If this is a properly sized variable, only add offset if it's less than
         end.  Otherwise, it is globbed to a single variable.  */
      
      if ((get_varinfo (i)->offset + offset) < get_varinfo (i)->fullsize)
        {
          unsigned HOST_WIDE_INT fieldoffset = get_varinfo (i)->offset + offset;
          varinfo_t v;
          for (v = first_vi_for_offset (get_varinfo (i), fieldoffset);
               v;
               v = next_vi_for_offset (v, fieldoffset))
            {         
              bitmap_set_bit (result, v->id);
            }
        }
      else if (get_varinfo (i)->is_artificial_var 
               || get_varinfo (i)->is_unknown_size_var)
        {
          bitmap_set_bit (result, i);
        }
    }
  
  bitmap_copy (set, result);  
  BITMAP_FREE (result);
}

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

static bool
set_union_with_increment  (bitmap to, bitmap from, unsigned HOST_WIDE_INT inc)
{
  if (inc == 0)
    return bitmap_ior_into (to, from);
  else
    {
      bitmap tmp;
      bool res;
      tmp = BITMAP_ALLOC (NULL);
      bitmap_copy (tmp, from);
      solution_set_add (tmp, inc);
      res = bitmap_ior_into (to, tmp);
      BITMAP_FREE (tmp);
      return res;
    }
}

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

static void
insert_into_complicated (unsigned int var, constraint_t c)
{
  varinfo_t vi = get_varinfo (var);
  unsigned int place = VEC_lower_bound (constraint_t, vi->complicated, c,
                                        constraint_less);
  VEC_safe_insert (constraint_t, vi->complicated, place, c);
}


/* Compare two constraint edges, return true if they are equal.  */

static bool
constraint_edge_equal (struct constraint_edge a, struct constraint_edge b)
{
  return a.src == b.src && a.dest == b.dest;
}

/* Compare two constraint edges, return true if A is less than B */

static bool
constraint_edge_less (const constraint_edge_t a, const constraint_edge_t b)
{
  if (a->dest < b->dest)
    return true;
  else if (a->dest == b->dest)
    return a->src < b->src;
  else
    return false;
}

/* Find the constraint edge that matches LOOKFOR, in VEC.
   Return the edge, if found, NULL otherwise.  */

static constraint_edge_t 
constraint_edge_vec_find (VEC(constraint_edge_t) *vec, 
                          struct constraint_edge lookfor)
{
  unsigned int place;  
  constraint_edge_t edge;
  place = VEC_lower_bound (constraint_edge_t, vec, &lookfor, 
                           constraint_edge_less);
  edge = VEC_index (constraint_edge_t, vec, place);
  if (!constraint_edge_equal (*edge, lookfor))
    return NULL;
  return edge;
}

/* Condense two variable nodes into a single variable node */

static void 
condense_varmap_nodes (unsigned int to, unsigned int src)
{
  varinfo_t tovi = get_varinfo (to);
  varinfo_t srcvi = get_varinfo (src);
  unsigned int i;
  constraint_t c;
  bitmap_iterator bi;
  
  /* the src node, and all it's variables, are now the to node.  */
  srcvi->node = to;
  EXECUTE_IF_SET_IN_BITMAP (srcvi->variables, 0, i, bi)
    {
      get_varinfo (i)->node = to;
    }
  
  /* Merge the src node variables and the to node variables.  */
  bitmap_set_bit (tovi->variables, src);
  bitmap_ior_into (tovi->variables, srcvi->variables);
  bitmap_clear (srcvi->variables);
  
  /* Move all complex constraints to the to node  */
  for (i = 0; VEC_iterate (constraint_t, srcvi->complicated, i, c); i++)
    {
      if (c->rhs.type == DEREF)
        {
          c->rhs.var = to;
        }
      else
        {
          c->lhs.var = to;
        }
    }
  constraint_set_union (&tovi->complicated, &srcvi->complicated);
  srcvi->complicated = NULL;
}

/* Erase EDGE from the graph.  */

static void
erase_graph_edge (constraint_graph_t graph, struct constraint_edge edge)
{
  VEC(constraint_edge_t) *predvec = graph->preds[edge.src];
  VEC(constraint_edge_t) *succvec = graph->succs[edge.dest];
  struct constraint_edge succe;
  unsigned int place;

  /* The successor will have the edges reversed.  */
  succe.dest = edge.src;
  succe.src = edge.dest;
  /* Remove from the successors.  */
  place = VEC_lower_bound (constraint_edge_t, succvec, &succe, 
                           constraint_edge_less);
  VEC_ordered_remove (constraint_edge_t, succvec, place);
  /* Remove from the predecessors.  */
  place = VEC_lower_bound (constraint_edge_t, predvec, &edge,
                           constraint_edge_less);
  VEC_ordered_remove (constraint_edge_t, predvec, place);
}

/* Remove edges involving node from graph.  */

static void
clear_edges_for_node (constraint_graph_t graph, unsigned int node)
{
  VEC(constraint_edge_t) *succvec = graph->succs[node];
  VEC(constraint_edge_t) *predvec = graph->preds[node];
  constraint_edge_t c;
  int i;
  
  /* Walk the successors, erase the associated preds.  */
  for (i = 0; VEC_iterate (constraint_edge_t, succvec, i, c); i++)
    if (c->dest != node)
      {
        unsigned int place;
        struct constraint_edge lookfor;
        lookfor.src = c->dest;
        lookfor.dest = node;
        place = VEC_lower_bound (constraint_edge_t, graph->preds[c->dest], 
                                 &lookfor, constraint_edge_less);
        VEC_ordered_remove (constraint_edge_t, graph->preds[c->dest], place);
      }
  /* Walk the preds, erase the associated succs.  */
  for (i =0; VEC_iterate (constraint_edge_t, predvec, i, c); i++)
    if (c->dest != node)
      {
        unsigned int place;
        struct constraint_edge lookfor;
        lookfor.src = c->dest;
        lookfor.dest = node;
        place = VEC_lower_bound (constraint_edge_t, graph->succs[c->dest],
                                 &lookfor, constraint_edge_less);
        VEC_ordered_remove (constraint_edge_t, graph->succs[c->dest], place);
      }    
  
  graph->preds[node] = NULL;
  graph->succs[node] = NULL;
}
static bool int_add_graph_edge (constraint_graph_t, unsigned int, 
                                unsigned int, unsigned HOST_WIDE_INT);
static bool add_graph_edge (constraint_graph_t, struct constraint_edge);
static bitmap get_graph_weights (constraint_graph_t, struct constraint_edge);


/* Merge graph nodes w and n into node n.  */

static void
merge_graph_nodes (constraint_graph_t graph, unsigned int n, unsigned int w)
{
  VEC(constraint_edge_t) *succvec = graph->succs[w];
  VEC(constraint_edge_t) *predvec = graph->preds[w];
  int i;
  constraint_edge_t c;
  
  for (i = 0; VEC_iterate (constraint_edge_t, predvec, i, c); i++)
    {
      unsigned int d = c->dest;
      struct constraint_edge olde;
      struct constraint_edge newe;
      bitmap temp;
      bitmap weights;
      if (c->dest == w)
        d = n;
      newe.src = n;
      newe.dest = d;
      add_graph_edge (graph, newe);
      olde.src = w;
      olde.dest = c->dest;
      temp = get_graph_weights (graph, olde);
      weights = get_graph_weights (graph, newe);
      bitmap_ior_into (weights, temp);
    }
  
  for (i = 0; VEC_iterate (constraint_edge_t, succvec, i, c); i++)
    {
      unsigned int d = c->dest;
      struct constraint_edge olde;
      struct constraint_edge newe;
      bitmap temp;
      bitmap weights;
      if (c->dest == w)
        d = n;
      newe.src = d;
      newe.dest = n;
      add_graph_edge (graph, newe);
      olde.src = c->dest;
      olde.dest = w;
      temp = get_graph_weights (graph, olde);
      weights = get_graph_weights (graph, newe);
      bitmap_ior_into (weights, temp);
    }
  clear_edges_for_node (graph, w);
}

/* Add a graph edge going from TO to FROM, with WEIGHT.  */

static bool
int_add_graph_edge (constraint_graph_t graph, unsigned int to, 
                    unsigned int from, unsigned HOST_WIDE_INT weight)
{
  if (to == from && weight == 0)
    {
      return false;
    }
  else
    {
      bool r;
      struct constraint_edge edge;
      edge.src = to;
      edge.dest = from;
      r = add_graph_edge (graph, edge);
      r |= !bitmap_bit_p (get_graph_weights (graph, edge), weight);
      bitmap_set_bit (get_graph_weights (graph, edge), weight);
      return r;
    }
}

  
/* Add edge NEWE to the graph.  */

static bool
add_graph_edge (constraint_graph_t graph, struct constraint_edge newe)
{
  unsigned int place;
  unsigned int src = newe.src;
  unsigned int dest = newe.dest;
  VEC(constraint_edge_t) *vec;
  vec = graph->preds[src];
  place = VEC_lower_bound (constraint_edge_t, vec, &newe, 
                           constraint_edge_less);
  if (place == VEC_length (constraint_edge_t, vec)
      || VEC_index (constraint_edge_t, vec, place)->dest != dest)
    {
      constraint_edge_t edge = new_constraint_edge (src, dest);
      bitmap weightbitmap;
      weightbitmap = BITMAP_GGC_ALLOC ();
      edge->weights = weightbitmap;
      VEC_safe_insert (constraint_edge_t, graph->preds[edge->src], place, edge);
      edge = new_constraint_edge (dest, src);
      edge->weights = weightbitmap;
      place = VEC_lower_bound (constraint_edge_t, graph->succs[edge->src],
                               edge, constraint_edge_less);
      VEC_safe_insert (constraint_edge_t, graph->succs[edge->src], place, edge);
      return true;
    }
  else
    return false;
}

/* Return true if LOOKFOR is an existing graph edge.  */

static bool
valid_graph_edge (constraint_graph_t graph, struct constraint_edge lookfor)
{
  return constraint_edge_vec_find (graph->preds[lookfor.src], lookfor) != NULL;
}


/* Return the bitmap representing the weights of edge LOOKFOR */

static bitmap
get_graph_weights (constraint_graph_t graph, struct constraint_edge lookfor)
{
  constraint_edge_t edge;
  unsigned int src = lookfor.src;
  VEC(constraint_edge_t) *vec;
  vec = graph->preds[src];
  edge = constraint_edge_vec_find (vec, lookfor);
  gcc_assert (edge != NULL);
  return edge->weights;
}

/* Build the constraint graph.  */

static void
build_constraint_graph (void)
{
  int i = 0;
  constraint_t c;
  graph = ggc_alloc (sizeof (struct constraint_graph));
  graph->succs = ggc_alloc_cleared (VEC_length (varinfo_t, varmap) * sizeof (*graph->succs));
  graph->preds = ggc_alloc_cleared (VEC_length (varinfo_t, varmap) * sizeof (*graph->preds));
  for (i = 0; VEC_iterate (constraint_t, constraints, i, c); i++)
    {
      struct constraint_expr lhs = c->lhs;
      struct constraint_expr rhs = c->rhs;
      if (lhs.type == DEREF)
        {
          /* *x = y or *x = &y (complex) */
          if (rhs.type == ADDRESSOF || rhs.var > anything_id)
            insert_into_complicated (lhs.var, c);
        }
      else if (rhs.type == DEREF)
        {
          /* NOT UNKNOWN = *y */
          if (lhs.var > anything_id) 
            insert_into_complicated (rhs.var, c);
        }
      else if (rhs.type == ADDRESSOF)
        {
          /* x = &y */
          bitmap_set_bit (get_varinfo (lhs.var)->solution, rhs.var);
        }
      else if (rhs.var > anything_id && lhs.var > anything_id)
        {
          /* Ignore 0 weighted self edges, as they can't possibly contribute
             anything */
          if (lhs.var != rhs.var || rhs.offset != 0 || lhs.offset != 0)
            {
              
              struct constraint_edge edge;
              edge.src = lhs.var;
              edge.dest = rhs.var;
              /* x = y (simple) */
              add_graph_edge (graph, edge);
              bitmap_set_bit (get_graph_weights (graph, edge),
                              rhs.offset);
            }
          
        }
    }
}
/* 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 in_component;
  int current_index;
  unsigned int *visited_index;
  varray_type scc_stack;
  varray_type unification_queue;
};

/* Recursive routine to find strongly connected components in GRAPH.  */

static void
scc_visit (constraint_graph_t graph, struct scc_info *si, unsigned int n)
{
  constraint_edge_t c;
  int i;
  gcc_assert (get_varinfo (n)->node == n);
  SET_BIT (si->visited, n);
  RESET_BIT (si->in_component, n);
  si->visited_index[n] = si->current_index ++;
  
  /* Visit all the successors.  */
  for (i = 0; VEC_iterate (constraint_edge_t, graph->succs[n], i, c); i++)
    {
      /* We only want to collapse the zero weight edges. */
      if (bitmap_bit_p (c->weights, 0))
        {
          unsigned int w = c->dest;
          if (!TEST_BIT (si->visited, w))
            scc_visit (graph, si, w);
          if (!TEST_BIT (si->in_component, w))
            {
              unsigned int t = get_varinfo (w)->node;
              unsigned int nnode = get_varinfo (n)->node;
              if (si->visited_index[t] < si->visited_index[nnode])
                {
                  get_varinfo (n)->node = t;
                }
            }
        }
    }
  
  /* See if any components have been identified.  */
  if (get_varinfo (n)->node == n)
    {
      unsigned int t = si->visited_index[n];
      SET_BIT (si->in_component, n);
      while (VARRAY_ACTIVE_SIZE (si->scc_stack) != 0 
             && t < si->visited_index[VARRAY_TOP_UINT (si->scc_stack)])
        {
          unsigned int w = VARRAY_TOP_UINT (si->scc_stack);
          get_varinfo (w)->node = n;
          SET_BIT (si->in_component, w);
          /* Mark this node for collapsing.  */
          VARRAY_PUSH_UINT (si->unification_queue, w);
          VARRAY_POP (si->scc_stack);
        } 
    }
  else
    VARRAY_PUSH_UINT (si->scc_stack, n);
}

/* Collapse two variables into one variable.  */

static void
collapse_nodes (constraint_graph_t graph, unsigned int to, unsigned int from)
{
  bitmap tosol, fromsol;
  struct constraint_edge edge;
  condense_varmap_nodes (to, from);
  tosol = get_varinfo (to)->solution;
  fromsol = get_varinfo (from)->solution;
  bitmap_ior_into (tosol, fromsol);
  merge_graph_nodes (graph, to, from);
  edge.src = to;
  edge.dest = to;
  if (valid_graph_edge (graph, edge))
    {
      bitmap weights = get_graph_weights (graph, edge);
      bitmap_clear_bit (weights, 0);
      if (bitmap_empty_p (weights))
        erase_graph_edge (graph, edge);
    }
  bitmap_clear (fromsol);
  get_varinfo (to)->address_taken |= get_varinfo (from)->address_taken;
  get_varinfo (to)->indirect_target |= get_varinfo (from)->indirect_target;
}


/* Unify nodes that we have found to be part of a cycle.  */

static void
process_unification_queue (constraint_graph_t graph, struct scc_info *si,
                           bool update_changed)
{
  size_t i = 0;
  bitmap tmp = BITMAP_ALLOC (NULL);
  bitmap_clear (tmp);
  while (i != VARRAY_ACTIVE_SIZE (si->unification_queue))
    {
      unsigned int tounify = VARRAY_UINT (si->unification_queue, i);
      unsigned int n = get_varinfo (tounify)->node;
      bool domore = false;
      if (dump_file && (dump_flags & TDF_DETAILS))
        fprintf (dump_file, "Unifying %s to %s\n", 
                 get_varinfo (tounify)->name,
                 get_varinfo (n)->name);
      if (update_changed)
        stats.unified_vars_dynamic++;
      else
        stats.unified_vars_static++;
      bitmap_ior_into (tmp, get_varinfo (tounify)->solution);
      merge_graph_nodes (graph, n, tounify);
      condense_varmap_nodes (n, tounify);
      
      if (update_changed && TEST_BIT (changed, tounify))
        {
          RESET_BIT (changed, tounify);
          if (!TEST_BIT (changed, n))
            SET_BIT (changed, n);
          else
            {
              gcc_assert (changed_count > 0);
              changed_count--;
            }
        }
      bitmap_clear (get_varinfo (tounify)->solution);
      ++i;
      if (i == VARRAY_ACTIVE_SIZE (si->unification_queue))
          domore = true;
      if (!domore)
        {
          tounify = VARRAY_UINT (si->unification_queue, i);
          if (get_varinfo (tounify)->node != n)
            domore = true;
        }     
      if (domore)
        {
          struct constraint_edge edge;
          /* If the solution changes because of the merging, we need to mark
             the variable as changed.  */
          if (bitmap_ior_into (get_varinfo (n)->solution, tmp))
            {
              if (update_changed && !TEST_BIT (changed, n))
                {
                  SET_BIT (changed, n);
                  changed_count++;
                }
            }
          bitmap_clear (tmp);
          edge.src = n;
          edge.dest = n;
          if (valid_graph_edge (graph, edge))
            {
              bitmap weights = get_graph_weights (graph, edge);
              bitmap_clear_bit (weights, 0);
              if (bitmap_empty_p (weights))
                erase_graph_edge (graph, edge);
            }
        }
    }
  BITMAP_FREE (tmp);
}

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

struct topo_info
{
  /* sbitmap of visited nodes.  */
  sbitmap visited;
  /* Array that stores the topographic order of the graph, *in
     reverse*.  */
  varray_type topo_order;
};

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

static struct topo_info *
init_topo_info (void)
{
  size_t size = VEC_length (varinfo_t, varmap);
  struct topo_info *ti = xmalloc (sizeof (struct topo_info));
  ti->visited = sbitmap_alloc (size);
  sbitmap_zero (ti->visited);
  VARRAY_UINT_INIT (ti->topo_order, 1, "Topological ordering");
  return ti;
}

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

static void
free_topo_info (struct topo_info *ti)
{
  sbitmap_free (ti->visited);
  VARRAY_CLEAR (ti->topo_order);
  free (ti);
}

/* Visit the graph in topographical 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)
{
  VEC(constraint_edge_t) *succs = graph->succs[n];
  constraint_edge_t c;
  int i;
  SET_BIT (ti->visited, n);
  for (i = 0; VEC_iterate (constraint_edge_t, succs, i, c); i++)
    {
      if (!TEST_BIT (ti->visited, c->dest))
        topo_visit (graph, ti, c->dest);
    }
  VARRAY_PUSH_UINT (ti->topo_order, n);
}

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

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

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

static void
do_da_constraint (constraint_graph_t graph ATTRIBUTE_UNUSED,
                  constraint_t c, bitmap delta)
{
  unsigned int rhs = c->rhs.var;
  unsigned HOST_WIDE_INT offset = c->lhs.offset;
  unsigned int j;
  bitmap_iterator bi;

  EXECUTE_IF_SET_IN_BITMAP (delta, 0, j, bi)
    {
      if (type_safe (j, &offset))
        {
          /* *x != NULL && *x != UNKNOWN */
          varinfo_t v;
          unsigned HOST_WIDE_INT fieldoffset = get_varinfo (j)->offset + offset;
          for (v = first_vi_for_offset (get_varinfo (j), fieldoffset);
               v;
               v = next_vi_for_offset (v, fieldoffset))
            {
              unsigned int t = v->node;
              bitmap sol = get_varinfo (t)->solution;
              if (!bitmap_bit_p (sol, rhs))
                {                 
                  bitmap_set_bit (sol, rhs);
                  if (!TEST_BIT (changed, t))
                    {
                      SET_BIT (changed, t);
                      changed_count++;
                    }
                }
            }
        }
      else if (dump_file)
        fprintf (dump_file, "Untypesafe usage in do_da_constraint.\n");
      
    }
}

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

static void
do_sd_constraint (constraint_graph_t graph, constraint_t c,
                  bitmap delta)
{
  unsigned int lhs = get_varinfo (c->lhs.var)->node;
  unsigned HOST_WIDE_INT roffset = c->rhs.offset;
  bool flag = false;
  bitmap sol = get_varinfo (lhs)->solution;
  unsigned int j;
  bitmap_iterator bi;
  
  /* For each variable j in delta (the starting solution point), we add
     an edge in the graph from the LHS to j + RHS offset, and update
     the current LHS solution.  */
  EXECUTE_IF_SET_IN_BITMAP (delta, 0, j, bi)
    {
      if (type_safe (j, &roffset))
        {
          varinfo_t v;
          unsigned HOST_WIDE_INT fieldoffset = get_varinfo (j)->offset + roffset;
          for (v = first_vi_for_offset (get_varinfo (j), fieldoffset);
               v;
               v = next_vi_for_offset (v, fieldoffset))
            {    
              unsigned int t = v->node;
              if (int_add_graph_edge (graph, lhs, t, 0))
                flag |= bitmap_ior_into (sol, get_varinfo (t)->solution);
            }
          
        }
      else if (dump_file)
        fprintf (dump_file, "Untypesafe usage in do_sd_constraint\n");
      
    }

  /* If the LHS solution changed, update it.  */
  if (flag)
    {
      get_varinfo (lhs)->solution = sol;
      if (!TEST_BIT (changed, lhs))
        {
          SET_BIT (changed, lhs);
          changed_count++;
        }
    }    
}

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

static void
do_ds_constraint (constraint_graph_t graph, constraint_t c, bitmap delta)
{
  unsigned int rhs = get_varinfo (c->rhs.var)->node;
  unsigned HOST_WIDE_INT loff = c->lhs.offset;
  unsigned HOST_WIDE_INT roff = c->rhs.offset;
  bitmap sol = get_varinfo (rhs)->solution;
  unsigned int j;
  bitmap_iterator bi;
  
  EXECUTE_IF_SET_IN_BITMAP (delta, 0, j, bi)
    {
      if (type_safe (j, &loff))
        {
          varinfo_t v;
          unsigned HOST_WIDE_INT fieldoffset = get_varinfo (j)->offset + loff;
          for (v = first_vi_for_offset (get_varinfo (j), fieldoffset);
               v;
               v = next_vi_for_offset (v, fieldoffset))
            {
              unsigned int t = v->node;
              
              if (int_add_graph_edge (graph, t, rhs, roff))
                {
                  bitmap tmp = get_varinfo (t)->solution;
                  if (set_union_with_increment (tmp, sol, roff))
                    {
                      get_varinfo (t)->solution = tmp;
                      if (t == rhs)
                        {
                          sol = get_varinfo (rhs)->solution;
                        }
                      if (!TEST_BIT (changed, t))
                        {
                          SET_BIT (changed, t);
                          changed_count++;
                        }
                    }
                }
            }
        }    
      else if (dump_file)
        fprintf (dump_file, "Untypesafe usage in do_ds_constraint\n");
    }
}

/* Handle a non-simple (simple meaning requires no iteration), non-copy
   constraint (IE *x = &y, x = *y, and *x = y).  */
   
static void
do_complex_constraint (constraint_graph_t graph, constraint_t c, bitmap delta)
{
  if (c->lhs.type == DEREF)
    {
      if (c->rhs.type == ADDRESSOF)
        {
          /* *x = &y */
          do_da_constraint (graph, c, delta);
        }
      else
        {
          /* *x = y */
          do_ds_constraint (graph, c, delta);
        }
    }
  else
    {
      /* x = *y */
      do_sd_constraint (graph, c, delta);
    }
}

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

static struct scc_info *
init_scc_info (void)
{
  struct scc_info *si = xmalloc (sizeof (struct scc_info));
  size_t size = VEC_length (varinfo_t, varmap);
  si->current_index = 0;
  si->visited = sbitmap_alloc (size);
  sbitmap_zero (si->visited);
  si->in_component = sbitmap_alloc (size);
  sbitmap_ones (si->in_component);
  si->visited_index = xcalloc (sizeof (unsigned int), size + 1);
  VARRAY_UINT_INIT (si->scc_stack, 1, "SCC stack");
  VARRAY_UINT_INIT (si->unification_queue, 1, "Unification queue");
  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->in_component);
  free (si->visited_index);
  VARRAY_CLEAR (si->scc_stack);
  VARRAY_CLEAR (si->unification_queue);
  free(si); 
}


/* Find cycles in GRAPH that occur, using strongly connected components, and
   collapse the cycles into a single representative node.  if UPDATE_CHANGED
   is true, then update the changed sbitmap to note those nodes whose
   solutions have  changed as a result of collapsing. */

static void
find_and_collapse_graph_cycles (constraint_graph_t graph, bool update_changed)
{
  unsigned int i;
  unsigned int size = VEC_length (varinfo_t, varmap);
  struct scc_info *si = init_scc_info ();

  for (i = 0; i != size; ++i)
    if (!TEST_BIT (si->visited, i) && get_varinfo (i)->node == i)
      scc_visit (graph, si, i);
  process_unification_queue (graph, si, update_changed);
  free_scc_info (si);
}

/* Compute a topographic order 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 = VEC_length (varinfo_t, varmap);
  
  for (i = 0; i != size; ++i)
    if (!TEST_BIT (ti->visited, i) && get_varinfo (i)->node == i)
      topo_visit (graph, ti, i);
}

/* Return true if bitmap B is empty, or a bitmap other than bit 0 is set. */

static bool
bitmap_other_than_zero_bit_set (bitmap b)
{
  unsigned int i;
  bitmap_iterator bi;
  if (bitmap_empty_p (b))
    return false;
  EXECUTE_IF_SET_IN_BITMAP (b, 1, i, bi)
    return true;
  return false;
}

/* Perform offline variable substitution, as per Rountev and Chandra.
   This is a linear 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.  */

static void
perform_rountev_chandra (constraint_graph_t graph)
{
  struct topo_info *ti = init_topo_info ();
 
  /* Compute the topographic ordering of the graph, then visit each
     node in topographic order.  */
  compute_topo_order (graph, ti);
 
  while (VARRAY_ACTIVE_SIZE (ti->topo_order) != 0)
    {
      unsigned int i = VARRAY_TOP_UINT (ti->topo_order);
      unsigned int pred;
      varinfo_t vi = get_varinfo (i);
      bool okay_to_elim = false;
      unsigned int root = VEC_length (varinfo_t, varmap);
      VEC(constraint_edge_t) *predvec = graph->preds[i];
      constraint_edge_t ce;
      bitmap tmp;

      VARRAY_POP (ti->topo_order);

      /* We can't eliminate things whose address is taken, or which is
         the target of a dereference.  */
      if (vi->address_taken || vi->indirect_target)
        continue;
      for (pred = 0; VEC_iterate (constraint_edge_t, predvec, pred, ce); pred++)
        {
          bitmap weight;
          unsigned int w;
          weight = get_graph_weights (graph, *ce);
        
          /* We can't eliminate variables that have non-zero weighted
             edges between them.  */
          if (bitmap_other_than_zero_bit_set (weight))
            {
              okay_to_elim = false;
              break;
            }
          w = get_varinfo (ce->dest)->node;
          /* We can't eliminate the node if one of the predecessors is
             part of a different strongly connected component.  */
          if (!okay_to_elim)
            {
              root = w;
              okay_to_elim = true;
            }
          else if (w != root)
            {
              okay_to_elim = false;
              break;
            }
          /* Theorem 4 in Rountev and Chandra: If i is a direct node,
             then Solution(i) is a subset of Solution (w), where w is a
             predecessor in the graph.  
             Corrolary: If all predecessors of i have the same
             points-to set, then i has that same points-to set as
             those predecessors.  */
          tmp = BITMAP_ALLOC (NULL);
          bitmap_and_compl (tmp, get_varinfo (i)->solution,
                            get_varinfo (w)->solution);
          if (!bitmap_empty_p (tmp))
            {
              okay_to_elim = false;
              BITMAP_FREE (tmp);
              break;
            }
          BITMAP_FREE (tmp);
        }
      /* See if the root is different than the original node. 
         If so, we've found an equivalence.  */
      if (root != get_varinfo (i)->node && okay_to_elim)
        {
          /* Found an equivalence */
          get_varinfo (i)->node = root;
          collapse_nodes (graph, root, i);
          if (dump_file && (dump_flags & TDF_DETAILS))
            fprintf (dump_file, "Collapsing %s into %s\n",
                     get_varinfo (i)->name,
                     get_varinfo (root)->name);
          stats.collapsed_vars++;
        }
    }
  free_topo_info (ti);
}

/* Solve the constraint graph GRAPH.  */

static void
solve_graph (constraint_graph_t graph)
{
  unsigned int size = VEC_length (varinfo_t, varmap);
  unsigned int i;
  changed_count = size;
  changed = sbitmap_alloc (size);
  sbitmap_ones (changed);
  
  /* The already collapsed/unreachable nodes will never change, so we
     need to  account for them in changed_count.  */
  for (i = 0; i < size; i++)
    if (get_varinfo (i)->node != i)
      changed_count--;
  
  while (changed_count > 0)
    {
      unsigned int i;
      struct topo_info *ti = init_topo_info ();
      stats.iterations++;
      find_and_collapse_graph_cycles (graph, true);
      compute_topo_order (graph, ti);
      while (VARRAY_ACTIVE_SIZE (ti->topo_order) != 0)
        {
          i = VARRAY_TOP_UINT (ti->topo_order);
          VARRAY_POP (ti->topo_order);
          gcc_assert (get_varinfo (i)->node == i);

          if (TEST_BIT (changed, i))
            {
              unsigned int j;
              constraint_t c;
              constraint_edge_t e;
              bitmap solution;
              VEC(constraint_t) *complicated = get_varinfo (i)->complicated;
              VEC(constraint_edge_t) *succs;
              RESET_BIT (changed, i);
              changed_count--;
              solution = get_varinfo (i)->solution;
              for (j = 0; VEC_iterate (constraint_t, complicated, j, c); j++)
                {
                  do_complex_constraint (graph, c, solution);
                }
              succs = graph->succs[i];
              for (j = 0; VEC_iterate (constraint_edge_t, succs, j, e); j++)
                {
                  bitmap tmp = get_varinfo (e->dest)->solution;
                  bool flag = false;
                  unsigned int k;
                  /* Process weighted edges */
                  bitmap weights = e->weights;
                  bitmap_iterator bi;

                  gcc_assert (!bitmap_empty_p (weights));
                  EXECUTE_IF_SET_IN_BITMAP (weights, 0, k, bi)
                    {
                      flag |= set_union_with_increment (tmp, solution, k);
                    }
                  if (flag)
                    {
                      get_varinfo (e->dest)->solution = tmp;                
                      if (!TEST_BIT (changed, e->dest))
                        {
                          SET_BIT (changed, e->dest);
                          changed_count++;
                        }
                    }
                }
            }
        }
      free_topo_info (ti);
    }
  sbitmap_free (changed);
}


/* Create points-to sets for the current function.  */

static void
create_alias_vars (void)
{
  basic_block bb;
  struct constraint_expr lhs, rhs;

  constraint_pool = create_alloc_pool ("Constraint pool", 
                                       sizeof (struct constraint), 30);
  variable_info_pool = create_alloc_pool ("Variable info pool",
                                          sizeof (struct variable_info), 30);
  constraint_edge_pool = create_alloc_pool ("Constraint edges",
                                            sizeof (struct constraint_edge), 30);
  
  constraints = VEC_alloc (constraint_t, 8);
  varmap = VEC_alloc (varinfo_t, 8);
  id_for_tree = htab_create (10, tree_id_hash, tree_id_eq, free);
  memset (&stats, 0, sizeof (stats));

  /* Create the NULL variable, used to represent that a variable points
     to NULL.  */
  nothing_tree = create_tmp_var_raw (void_type_node, "NULL");
  var_nothing = new_var_info (nothing_tree, 0, "NULL", 0);
  insert_id_for_tree (nothing_tree, 0);
  var_nothing->is_artificial_var = 1;
  var_nothing->offset = 0;
  var_nothing->size = ~0;
  var_nothing->fullsize = ~0;
  var_nothing->base = var_nothing;
  nothing_id = 0;
  VEC_safe_push (varinfo_t, varmap, var_nothing);

  /* Create the ANYTHING variable, used to represent that a variable
     points to some unknown piece of memory.  */
  anything_tree = create_tmp_var_raw (void_type_node, "ANYTHING");
  var_anything = new_var_info (anything_tree, 1, "ANYTHING", 1); 
  insert_id_for_tree (anything_tree, 1);
  var_anything->is_artificial_var = 1;
  var_anything->size = ~0;
  var_anything->offset = 0;
  var_anything->next = NULL;
  var_anything->base = var_anything;
  var_anything->fullsize = ~0;
  
  anything_id = 1;
  VEC_safe_push (varinfo_t, varmap, var_anything);
  lhs.type = SCALAR;
  lhs.var = anything_id;
  lhs.offset = 0;
  rhs.type = ADDRESSOF;
  rhs.var = anything_id;
  rhs.offset = 0;
  var_anything->address_taken = true;
  VEC_safe_push (constraint_t, constraints, 
                 new_constraint (lhs, rhs));

  /* Create the READONLY variable, used to represent that a variable
     points to readonly memory.  */
  readonly_tree = create_tmp_var_raw (void_type_node, "READONLY");
  var_readonly = new_var_info (readonly_tree, 2, "READONLY", 2);
  var_readonly->is_artificial_var = 1;
  var_readonly->offset = 0;
  var_readonly->size = ~0;
  var_readonly->fullsize = ~0;
  var_readonly->next = NULL;
  var_readonly->base = var_readonly;
  
  
  insert_id_for_tree (readonly_tree, 2);
  readonly_id = 2;
  VEC_safe_push (varinfo_t, varmap, var_readonly);
  lhs.type = SCALAR;
  lhs.var = readonly_id;
  lhs.offset = 0;
  rhs.type = ADDRESSOF;
  rhs.var = readonly_id;
  rhs.offset = 0;
  var_readonly->address_taken = true;

  VEC_safe_push (constraint_t, constraints, 
                 new_constraint (lhs, rhs));
  
  /* Create the INTEGER variable, used to represent that a variable points
     to an INTEGER.  */
  integer_tree = create_tmp_var_raw (void_type_node, "INTEGER");
  var_integer = new_var_info (integer_tree, 3, "INTEGER", 3);
  insert_id_for_tree (integer_tree, 3);
  var_integer->is_artificial_var = 1;
  var_integer->size = ~0;
  var_integer->fullsize = ~0;
  var_integer->offset = 0;
  var_integer->next = NULL;
  var_integer->base = var_integer;  
  integer_id = 3;
  VEC_safe_push (varinfo_t, varmap, var_integer);

  create_variable_infos ();
  /* Now walk all statements and derive aliases.  */
  FOR_EACH_BB (bb)
    {
      block_stmt_iterator bsi; 
      tree phi;
      for (phi = phi_nodes (bb); phi; phi = TREE_CHAIN (phi))
        if (is_gimple_reg (PHI_RESULT (phi)))
          find_func_aliases (phi);
      for (bsi = bsi_start (bb); !bsi_end_p (bsi); bsi_next (&bsi))
        find_func_aliases (bsi_stmt (bsi));
    }

  build_constraint_graph ();
  if (dump_file)
    {
      fprintf (dump_file, "Constraints:\n");
      print_constraints (dump_file);
    }
  if (dump_file)
    fprintf (dump_file, "Collapsing static cycles and doing variable substitution:\n");
  find_and_collapse_graph_cycles (graph, false);
  perform_rountev_chandra (graph);
  if (dump_file)
    fprintf (dump_file, "Solving graph:\n");
  solve_graph (graph);
  if (dump_file)
    {
      unsigned int i;
      if (dump_flags & TDF_STATS)
        {
          fprintf (dump_file, "Stats:\n");
          fprintf (dump_file, "Total vars:%d\n", stats.total_vars);
          fprintf (dump_file, "Statically unified vars:%d\n", stats.unified_vars_static);
          fprintf (dump_file, "Collapsed vars:%d\n", stats.collapsed_vars);
          fprintf (dump_file, "Dynamically unified vars:%d\n", stats.unified_vars_dynamic);
          fprintf (dump_file, "Iterations:%d\n", stats.iterations);
        }
      for (i = 0; i < VEC_length (varinfo_t, varmap); i++)
        print_solution_for_var (dump_file, i);
     
    }
  

}

struct tree_opt_pass pass_build_pta = 
{
  "pta",                                /* name */
  NULL,                                 /* gate */
  create_alias_vars,                    /* execute */
  NULL,                                 /* sub */
  NULL,                                 /* next */
  0,                                    /* static_pass_number */
  TV_TREE_PTA,                          /* tv_id */
  PROP_cfg,                             /* properties_required */
  PROP_pta,                             /* properties_provided */
  0,                                    /* properties_destroyed */
  0,                                    /* todo_flags_start */
  0,                                    /* todo_flags_finish */
  0                                     /* letter */
};
 

/* Delete created points-to sets.  */

static void
delete_alias_vars (void)
{
  htab_delete (id_for_tree);
  free_alloc_pool (variable_info_pool);
  free_alloc_pool (constraint_pool); 
  free_alloc_pool (constraint_edge_pool);
}

struct tree_opt_pass pass_del_pta = 
{
  NULL,                                 /* name */
  NULL,                                 /* gate */
  delete_alias_vars,                    /* execute */
  NULL,                                 /* sub */
  NULL,                                 /* next */
  0,                                    /* static_pass_number */
  TV_TREE_PTA,                          /* tv_id */
  PROP_pta,                             /* properties_required */
  0,                                    /* properties_provided */
  PROP_pta,                             /* properties_destroyed */
  0,                                    /* todo_flags_start */
  0,                                    /* todo_flags_finish */
  0                                     /* letter */
};


#define MASK_POINTER(P) ((unsigned)((unsigned long)(P) & 0xffff))

const char *
alias_get_name (tree t)
{
  const char *name;
  
  if (TREE_CODE (t) == FUNCTION_DECL)
    name = IDENTIFIER_POINTER (DECL_NAME (t));
  else if (TREE_CODE (t) == FIELD_DECL)
    {
      tree context = DECL_FIELD_CONTEXT (t);
      tree typename = TYPE_NAME (context);   
      const char *structname;
      char *result = alloca (512);
      char *newname;
      if (typename && TREE_CODE (typename) == TYPE_DECL)
        typename = DECL_NAME (typename);

      if (!typename)
        {
          char *namep;
          /* 2 = UF
             4 = the masked pointer
             2 = the <> around it
             1 = the terminator.  */
          namep = ggc_alloc (2 + 4 + 2 + 1);
          sprintf (namep, "<UV%x>", MASK_POINTER (t));
          structname = namep;
        }
      else
        structname = IDENTIFIER_POINTER (typename);

      sprintf (result, "%s.%s", structname, get_name (t));
      newname = ggc_alloc (strlen (result) + 1);
      strcpy (newname, result);
      name = newname;
    }
  else if (TREE_CODE (t) == RESULT_DECL)
    name = "<return value>";
  else if (TREE_CODE (t) == SSA_NAME)
    {
      char *result = alloca (128);
      char *newname;
      sprintf (result, "%s_%d", alias_get_name (SSA_NAME_VAR (t)),
               SSA_NAME_VERSION (t));
      newname = ggc_alloc (strlen (result) + 1);
      strcpy (newname, result);
      name = newname;
    }
  else if (TREE_CODE (t) == RESULT_DECL)
          name = "<return value>";
  else
    name = get_name (t);
  
  if (!name)
    {
      char *namep;
      /* 2 = UF
         4 = the masked pointer
         2 = the <> around it
         1 = the terminator.  */
      namep = ggc_alloc (2 + 4 + 2 + 1);
      sprintf (namep, "<UV%x>", MASK_POINTER (t));
      return namep;
    }
  return name;
}