--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/tree-ssa-uninit.c	Mon May 24 12:47:05 2010 +0900
@@ -0,0 +1,1759 @@
+/* Predicate aware uninitialized variable warning.
+   Copyright (C) 2001, 2002, 2003, 2004, 2005, 2007, 2008, 2010 Free Software
+   Foundation, Inc.
+   Contributed by Xinliang David Li <davidxl@google.com>
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tm.h"
+#include "tree.h"
+#include "flags.h"
+#include "tm_p.h"
+#include "langhooks.h"
+#include "basic-block.h"
+#include "output.h"
+#include "expr.h"
+#include "function.h"
+#include "diagnostic.h"
+#include "gimple-pretty-print.h"
+#include "bitmap.h"
+#include "pointer-set.h"
+#include "tree-flow.h"
+#include "gimple.h"
+#include "tree-inline.h"
+#include "timevar.h"
+#include "hashtab.h"
+#include "tree-dump.h"
+#include "tree-pass.h"
+#include "toplev.h"
+#include "timevar.h"
+
+/* This implements the pass that does predicate aware warning on uses of
+   possibly uninitialized variables. The pass first collects the set of
+   possibly uninitialized SSA names. For each such name, it walks through
+   all its immediate uses. For each immediate use, it rebuilds the condition
+   expression (the predicate) that guards the use. The predicate is then
+   examined to see if the variable is always defined under that same condition.
+   This is done either by pruning the unrealizable paths that lead to the
+   default definitions or by checking if the predicate set that guards the
+   defining paths is a superset of the use predicate.  */
+
+
+/* Pointer set of potentially undefined ssa names, i.e.,
+   ssa names that are defined by phi with operands that
+   are not defined or potentially undefined.  */
+static struct pointer_set_t *possibly_undefined_names = 0;
+
+/* Bit mask handling macros.  */
+#define MASK_SET_BIT(mask, pos) mask |= (1 << pos)
+#define MASK_TEST_BIT(mask, pos) (mask & (1 << pos))
+#define MASK_EMPTY(mask) (mask == 0)
+
+/* Returns the first bit position (starting from LSB)
+   in mask that is non zero. Returns -1 if the mask is empty.  */
+static int
+get_mask_first_set_bit (unsigned mask)
+{
+  int pos = 0;
+  if (mask == 0)
+    return -1;
+
+  while ((mask & (1 << pos)) == 0)
+    pos++;
+
+  return pos;
+}
+#define MASK_FIRST_SET_BIT(mask) get_mask_first_set_bit (mask)
+
+
+/* Return true if T, an SSA_NAME, has an undefined value.  */
+
+bool
+ssa_undefined_value_p (tree t)
+{
+  tree var = SSA_NAME_VAR (t);
+
+  /* Parameters get their initial value from the function entry.  */
+  if (TREE_CODE (var) == PARM_DECL)
+    return false;
+
+  /* Hard register variables get their initial value from the ether.  */
+  if (TREE_CODE (var) == VAR_DECL && DECL_HARD_REGISTER (var))
+    return false;
+
+  /* The value is undefined iff its definition statement is empty.  */
+  return (gimple_nop_p (SSA_NAME_DEF_STMT (t))
+          || (possibly_undefined_names
+              && pointer_set_contains (possibly_undefined_names, t)));
+}
+
+/* Checks if the operand OPND of PHI is defined by 
+   another phi with one operand defined by this PHI, 
+   but the rest operands are all defined. If yes, 
+   returns true to skip this this operand as being
+   redundant. Can be enhanced to be more general.  */
+
+static bool
+can_skip_redundant_opnd (tree opnd, gimple phi)
+{
+  gimple op_def;
+  tree phi_def;
+  int i, n;
+
+  phi_def = gimple_phi_result (phi);
+  op_def = SSA_NAME_DEF_STMT (opnd);
+  if (gimple_code (op_def) != GIMPLE_PHI)
+    return false;
+  n = gimple_phi_num_args (op_def);
+  for (i = 0; i < n; ++i)
+    {
+      tree op = gimple_phi_arg_def (op_def, i);
+      if (TREE_CODE (op) != SSA_NAME)
+        continue;
+      if (op != phi_def && ssa_undefined_value_p (op))
+        return false;
+    }
+
+  return true;
+}
+
+/* Returns a bit mask holding the positions of arguments in PHI
+   that have empty (or possibly empty) definitions.  */
+
+static unsigned
+compute_uninit_opnds_pos (gimple phi)
+{
+  size_t i, n;
+  unsigned uninit_opnds = 0;
+
+  n = gimple_phi_num_args (phi);
+
+  for (i = 0; i < n; ++i)
+    {
+      tree op = gimple_phi_arg_def (phi, i);
+      if (TREE_CODE (op) == SSA_NAME
+          && ssa_undefined_value_p (op)
+          && !can_skip_redundant_opnd (op, phi))
+        MASK_SET_BIT (uninit_opnds, i);
+    }
+  return uninit_opnds;
+}
+
+/* Find the immediate postdominator PDOM of the specified
+   basic block BLOCK.  */
+
+static inline basic_block
+find_pdom (basic_block block)
+{
+   if (block == EXIT_BLOCK_PTR)
+     return EXIT_BLOCK_PTR;
+   else
+     {
+       basic_block bb
+           = get_immediate_dominator (CDI_POST_DOMINATORS, block);
+       if (! bb)
+         return EXIT_BLOCK_PTR;
+       return bb;
+     }
+}
+
+/* Find the immediate DOM of the specified
+   basic block BLOCK.  */
+
+static inline basic_block
+find_dom (basic_block block)
+{
+   if (block == ENTRY_BLOCK_PTR)
+     return ENTRY_BLOCK_PTR;
+   else
+     {
+       basic_block bb = get_immediate_dominator (CDI_DOMINATORS, block);
+       if (! bb)
+         return ENTRY_BLOCK_PTR;
+       return bb;
+     }
+}
+
+/* Returns true if BB1 is postdominating BB2 and BB1 is
+   not a loop exit bb. The loop exit bb check is simple and does
+   not cover all cases.  */
+
+static bool
+is_non_loop_exit_postdominating (basic_block bb1, basic_block bb2)
+{
+  if (!dominated_by_p (CDI_POST_DOMINATORS, bb2, bb1))
+    return false;
+
+  if (single_pred_p (bb1) && !single_succ_p (bb2))
+    return false;
+
+  return true;
+}
+
+/* Find the closest postdominator of a specified BB, which is control
+   equivalent to BB.  */
+
+static inline  basic_block
+find_control_equiv_block (basic_block bb)
+{
+  basic_block pdom;
+
+  pdom = find_pdom (bb);
+
+  /* Skip the postdominating bb that is also loop exit.  */
+  if (!is_non_loop_exit_postdominating (pdom, bb))
+    return NULL;
+
+  if (dominated_by_p (CDI_DOMINATORS, pdom, bb))
+    return pdom;
+
+  return NULL;
+}
+
+#define MAX_NUM_CHAINS 8
+#define MAX_CHAIN_LEN 5
+
+/* Computes the control dependence chains (paths of edges)
+   for DEP_BB up to the dominating basic block BB (the head node of a
+   chain should be dominated by it).  CD_CHAINS is pointer to a
+   dynamic array holding the result chains. CUR_CD_CHAIN is the current
+   chain being computed.  *NUM_CHAINS is total number of chains.  The
+   function returns true if the information is successfully computed,
+   return false if there is no control dependence or not computed.  */
+
+static bool
+compute_control_dep_chain (basic_block bb, basic_block dep_bb,
+                           VEC(edge, heap) **cd_chains,
+                           size_t *num_chains,
+                           VEC(edge, heap) **cur_cd_chain)
+{
+  edge_iterator ei;
+  edge e;
+  size_t i;
+  bool found_cd_chain = false;
+  size_t cur_chain_len = 0;
+
+  if (EDGE_COUNT (bb->succs) < 2)
+    return false;
+
+  /* Could  use a set instead.  */
+  cur_chain_len = VEC_length (edge, *cur_cd_chain);
+  if (cur_chain_len > MAX_CHAIN_LEN)
+    return false;
+
+  for (i = 0; i < cur_chain_len; i++)
+    {
+      edge e = VEC_index (edge, *cur_cd_chain, i);
+      /* cycle detected. */
+      if (e->src == bb)
+        return false;
+    }
+
+  FOR_EACH_EDGE (e, ei, bb->succs)
+    {
+      basic_block cd_bb;
+      if (e->flags & (EDGE_FAKE | EDGE_ABNORMAL))
+        continue;
+
+      cd_bb = e->dest;
+      VEC_safe_push (edge, heap, *cur_cd_chain, e);
+      while (!is_non_loop_exit_postdominating (cd_bb, bb))
+        {
+          if (cd_bb == dep_bb)
+            {
+              /* Found a direct control dependence.  */
+              if (*num_chains < MAX_NUM_CHAINS)
+                {
+                  cd_chains[*num_chains]
+                      = VEC_copy (edge, heap, *cur_cd_chain);
+                  (*num_chains)++;
+                }
+              found_cd_chain = true;
+              /* check path from next edge.  */
+              break;
+            }
+
+          /* Now check if DEP_BB is indirectly control dependent on BB.  */
+          if (compute_control_dep_chain (cd_bb, dep_bb, cd_chains,
+                                         num_chains, cur_cd_chain))
+            {
+              found_cd_chain = true;
+              break;
+            }
+
+          cd_bb = find_pdom (cd_bb);
+          if (cd_bb == EXIT_BLOCK_PTR)
+            break;
+        }
+      VEC_pop (edge, *cur_cd_chain);
+      gcc_assert (VEC_length (edge, *cur_cd_chain) == cur_chain_len);
+    }
+  gcc_assert (VEC_length (edge, *cur_cd_chain) == cur_chain_len);
+
+  return found_cd_chain;
+}
+
+typedef struct use_pred_info
+{
+  gimple cond;
+  bool invert;
+} *use_pred_info_t;
+
+DEF_VEC_P(use_pred_info_t);
+DEF_VEC_ALLOC_P(use_pred_info_t, heap);
+
+
+/* Converts the chains of control dependence edges into a set of
+   predicates. A control dependence chain is represented by a vector
+   edges. DEP_CHAINS points to an array of dependence chains.
+   NUM_CHAINS is the size of the chain array. One edge in a dependence
+   chain is mapped to predicate expression represented by use_pred_info_t
+   type. One dependence chain is converted to a composite predicate that
+   is the result of AND operation of use_pred_info_t mapped to each edge.
+   A composite predicate is presented by a vector of use_pred_info_t. On
+   return, *PREDS points to the resulting array of composite predicates.
+   *NUM_PREDS is the number of composite predictes.  */
+
+static bool
+convert_control_dep_chain_into_preds (VEC(edge, heap) **dep_chains,
+                                      size_t num_chains,
+                                      VEC(use_pred_info_t, heap) ***preds,
+                                      size_t *num_preds)
+{
+  bool has_valid_pred = false;
+  size_t i, j;
+  if (num_chains == 0 || num_chains >= MAX_NUM_CHAINS)
+    return false;
+
+  /* Now convert CD chains into predicates  */
+  has_valid_pred = true;
+
+  /* Now convert the control dep chain into a set
+     of predicates.  */
+  *preds = XCNEWVEC (VEC(use_pred_info_t, heap) *,
+                     num_chains);
+  *num_preds = num_chains;
+
+  for (i = 0; i < num_chains; i++)
+    {
+      VEC(edge, heap) *one_cd_chain = dep_chains[i];
+      for (j = 0; j < VEC_length (edge, one_cd_chain); j++)
+        {
+          gimple cond_stmt;
+          gimple_stmt_iterator gsi;
+          basic_block guard_bb;
+          use_pred_info_t one_pred;
+          edge e;
+
+          e = VEC_index (edge, one_cd_chain, j);
+          guard_bb = e->src;
+          gsi = gsi_last_bb (guard_bb);
+          if (gsi_end_p (gsi))
+            {
+              has_valid_pred = false;
+              break;
+            }
+          cond_stmt = gsi_stmt (gsi);
+          if (gimple_code (cond_stmt) == GIMPLE_CALL
+              && EDGE_COUNT (e->src->succs) >= 2)
+            {
+              /* Ignore EH edge. Can add assertion
+                 on the other edge's flag.  */
+              continue;
+            }
+          /* Skip if there is essentially one succesor.  */
+          if (EDGE_COUNT (e->src->succs) == 2)
+            {
+              edge e1;
+              edge_iterator ei1;
+              bool skip = false;
+
+              FOR_EACH_EDGE (e1, ei1, e->src->succs)
+                {
+                  if (EDGE_COUNT (e1->dest->succs) == 0)
+                    {
+                      skip = true;
+                      break;
+                    }
+                }
+              if (skip)
+                continue;
+            }
+          if (gimple_code (cond_stmt) != GIMPLE_COND)
+            {
+              has_valid_pred = false;
+              break;
+            }
+          one_pred = XNEW (struct use_pred_info);
+          one_pred->cond = cond_stmt;
+          one_pred->invert = !!(e->flags & EDGE_FALSE_VALUE);
+          VEC_safe_push (use_pred_info_t, heap, (*preds)[i], one_pred);
+        }
+
+      if (!has_valid_pred)
+        break;
+    }
+  return has_valid_pred;
+}
+
+/* Computes all control dependence chains for USE_BB. The control
+   dependence chains are then converted to an array of composite
+   predicates pointed to by PREDS.  PHI_BB is the basic block of
+   the phi whose result is used in USE_BB.  */
+
+static bool
+find_predicates (VEC(use_pred_info_t, heap) ***preds,
+                 size_t *num_preds,
+                 basic_block phi_bb,
+                 basic_block use_bb)
+{
+  size_t num_chains = 0, i;
+  VEC(edge, heap) **dep_chains = 0;
+  VEC(edge, heap) *cur_chain = 0;
+  bool has_valid_pred = false;
+  basic_block cd_root = 0;
+
+  dep_chains = XCNEWVEC (VEC(edge, heap) *, MAX_NUM_CHAINS);
+
+  /* First find the closest bb that is control equivalent to PHI_BB
+     that also dominates USE_BB.  */
+  cd_root = phi_bb;
+  while (dominated_by_p (CDI_DOMINATORS, use_bb, cd_root))
+    {
+      basic_block ctrl_eq_bb = find_control_equiv_block (cd_root);
+      if (ctrl_eq_bb && dominated_by_p (CDI_DOMINATORS, use_bb, ctrl_eq_bb))
+        cd_root = ctrl_eq_bb;
+      else
+        break;
+    }
+
+  compute_control_dep_chain (cd_root, use_bb,
+                             dep_chains, &num_chains,
+                             &cur_chain);
+
+  has_valid_pred
+      = convert_control_dep_chain_into_preds (dep_chains,
+                                              num_chains,
+                                              preds,
+                                              num_preds);
+  /* Free individual chain  */
+  VEC_free (edge, heap, cur_chain);
+  for (i = 0; i < num_chains; i++)
+      VEC_free (edge, heap, dep_chains[i]);
+  free (dep_chains);
+  return has_valid_pred;
+}
+
+/* Computes the set of incoming edges of PHI that have non empty
+   definitions of a phi chain.  The collection will be done
+   recursively on operands that are defined by phis. CD_ROOT
+   is the control dependence root. *EDGES holds the result, and
+   VISITED_PHIS is a pointer set for detecting cycles.  */
+
+static void
+collect_phi_def_edges (gimple phi, basic_block cd_root,
+                       VEC(edge, heap) **edges,
+                       struct pointer_set_t *visited_phis)
+{
+  size_t i, n;
+  edge opnd_edge;
+  tree opnd;
+
+  if (pointer_set_insert (visited_phis, phi))
+    return;
+
+  n = gimple_phi_num_args (phi);
+  for (i = 0; i < n; i++)
+    {
+      opnd_edge = gimple_phi_arg_edge (phi, i);
+      opnd = gimple_phi_arg_def (phi, i);
+
+      if (TREE_CODE (opnd) != SSA_NAME
+          || !ssa_undefined_value_p (opnd))
+        VEC_safe_push (edge, heap, *edges, opnd_edge);
+      else
+        {
+          gimple def = SSA_NAME_DEF_STMT (opnd);
+          if (gimple_code (def) == GIMPLE_PHI
+              && dominated_by_p (CDI_DOMINATORS,
+                                 gimple_bb (def), cd_root))
+            collect_phi_def_edges (def, cd_root, edges,
+                                   visited_phis);
+        }
+    }
+}
+
+/* For each use edge of PHI, computes all control dependence chains.
+   The control dependence chains are then converted to an array of
+   composite predicates pointed to by PREDS.  */
+
+static bool
+find_def_preds (VEC(use_pred_info_t, heap) ***preds,
+                size_t *num_preds, gimple phi)
+{
+  size_t num_chains = 0, i, n;
+  VEC(edge, heap) **dep_chains = 0;
+  VEC(edge, heap) *cur_chain = 0;
+  VEC(edge, heap) *def_edges = 0;
+  bool has_valid_pred = false;
+  basic_block phi_bb, cd_root = 0;
+  struct pointer_set_t *visited_phis;
+
+  dep_chains = XCNEWVEC (VEC(edge, heap) *, MAX_NUM_CHAINS);
+
+  phi_bb = gimple_bb (phi);
+  /* First find the closest dominating bb to be
+     the control dependence root  */
+  cd_root = find_dom (phi_bb);
+  if (!cd_root)
+    return false;
+
+  visited_phis = pointer_set_create ();
+  collect_phi_def_edges (phi, cd_root, &def_edges, visited_phis);
+  pointer_set_destroy (visited_phis);
+
+  n = VEC_length (edge, def_edges);
+  if (n == 0)
+    return false;
+
+  for (i = 0; i < n; i++)
+    {
+      size_t prev_nc, j;
+      edge opnd_edge;
+
+      opnd_edge = VEC_index (edge, def_edges, i);
+      prev_nc = num_chains;
+      compute_control_dep_chain (cd_root, opnd_edge->src,
+                                 dep_chains, &num_chains,
+                                 &cur_chain);
+      /* Free individual chain  */
+      VEC_free (edge, heap, cur_chain);
+      cur_chain = 0;
+
+      /* Now update the newly added chains with
+         the phi operand edge:  */
+      if (EDGE_COUNT (opnd_edge->src->succs) > 1)
+        {
+          if (prev_nc == num_chains
+              && num_chains < MAX_NUM_CHAINS)
+            num_chains++;
+          for (j = prev_nc; j < num_chains; j++)
+            {
+              VEC_safe_push (edge, heap, dep_chains[j], opnd_edge);
+            }
+        }
+    }
+
+  has_valid_pred
+      = convert_control_dep_chain_into_preds (dep_chains,
+                                              num_chains,
+                                              preds,
+                                              num_preds);
+  for (i = 0; i < num_chains; i++)
+      VEC_free (edge, heap, dep_chains[i]);
+  free (dep_chains);
+  return has_valid_pred;
+}
+
+/* Dumps the predicates (PREDS) for USESTMT.  */
+
+static void
+dump_predicates (gimple usestmt, size_t num_preds,
+                 VEC(use_pred_info_t, heap) **preds,
+                 const char* msg)
+{
+  size_t i, j;
+  VEC(use_pred_info_t, heap) *one_pred_chain;
+  fprintf (dump_file, msg);
+  print_gimple_stmt (dump_file, usestmt, 0, 0);
+  fprintf (dump_file, "is guarded by :\n");
+  /* do some dumping here:  */
+  for (i = 0; i < num_preds; i++)
+    {
+      size_t np;
+
+      one_pred_chain = preds[i];
+      np = VEC_length (use_pred_info_t, one_pred_chain);
+
+      for (j = 0; j < np; j++)
+        {
+          use_pred_info_t one_pred
+              = VEC_index (use_pred_info_t, one_pred_chain, j);
+          if (one_pred->invert)
+            fprintf (dump_file, " (.NOT.) ");
+          print_gimple_stmt (dump_file, one_pred->cond, 0, 0);
+          if (j < np - 1)
+            fprintf (dump_file, "(.AND.)\n");
+        }
+      if (i < num_preds - 1)
+        fprintf (dump_file, "(.OR.)\n");
+    }
+}
+
+/* Destroys the predicate set *PREDS.  */
+
+static void
+destroy_predicate_vecs (size_t n,
+                        VEC(use_pred_info_t, heap) ** preds)
+{
+  size_t i, j;
+  for (i = 0; i < n; i++)
+    {
+      for (j = 0; j < VEC_length (use_pred_info_t, preds[i]); j++)
+        free (VEC_index (use_pred_info_t, preds[i], j));
+      VEC_free (use_pred_info_t, heap, preds[i]);
+    }
+  free (preds);
+}
+
+
+/* Computes the 'normalized' conditional code with operand 
+   swapping and condition inversion.  */
+
+static enum tree_code
+get_cmp_code (enum tree_code orig_cmp_code,
+              bool swap_cond, bool invert)
+{
+  enum tree_code tc = orig_cmp_code;
+
+  if (swap_cond)
+    tc = swap_tree_comparison (orig_cmp_code);
+  if (invert)
+    tc = invert_tree_comparison (tc, false);
+
+  switch (tc)
+    {
+    case LT_EXPR:
+    case LE_EXPR:
+    case GT_EXPR:
+    case GE_EXPR:
+    case EQ_EXPR:
+    case NE_EXPR:
+      break;
+    default:
+      return ERROR_MARK;
+    }
+  return tc;
+}
+
+/* Returns true if VAL falls in the range defined by BOUNDARY and CMPC, i.e.
+   all values in the range satisfies (x CMPC BOUNDARY) == true.  */
+
+static bool
+is_value_included_in (tree val, tree boundary, enum tree_code cmpc)
+{
+  bool inverted = false;
+  bool is_unsigned;
+  bool result;
+
+  /* Only handle integer constant here.  */
+  if (TREE_CODE (val) != INTEGER_CST
+      || TREE_CODE (boundary) != INTEGER_CST)
+    return true;
+
+  is_unsigned = TYPE_UNSIGNED (TREE_TYPE (val));
+
+  if (cmpc == GE_EXPR || cmpc == GT_EXPR
+      || cmpc == NE_EXPR)
+    {
+      cmpc = invert_tree_comparison (cmpc, false);
+      inverted = true;
+    }
+
+  if (is_unsigned)
+    {
+      if (cmpc == EQ_EXPR)
+        result = tree_int_cst_equal (val, boundary);
+      else if (cmpc == LT_EXPR)
+        result = INT_CST_LT_UNSIGNED (val, boundary);
+      else
+        {
+          gcc_assert (cmpc == LE_EXPR);
+          result = (tree_int_cst_equal (val, boundary)
+                    || INT_CST_LT_UNSIGNED (val, boundary));
+        }
+    }
+  else
+    {
+      if (cmpc == EQ_EXPR)
+        result = tree_int_cst_equal (val, boundary);
+      else if (cmpc == LT_EXPR)
+        result = INT_CST_LT (val, boundary);
+      else
+        {
+          gcc_assert (cmpc == LE_EXPR);
+          result = (tree_int_cst_equal (val, boundary)
+                    || INT_CST_LT (val, boundary));
+        }
+    }
+
+  if (inverted)
+    result ^= 1;
+
+  return result;
+}
+
+/* Returns true if PRED is common among all the predicate
+   chains (PREDS) (and therefore can be factored out).
+   NUM_PRED_CHAIN is the size of array PREDS.  */
+
+static bool
+find_matching_predicate_in_rest_chains (use_pred_info_t pred,
+                                        VEC(use_pred_info_t, heap) **preds,
+                                        size_t num_pred_chains)
+{
+  size_t i, j, n;
+
+  /* trival case  */
+  if (num_pred_chains == 1)
+    return true;
+
+  for (i = 1; i < num_pred_chains; i++)
+    {
+      bool found = false;
+      VEC(use_pred_info_t, heap) *one_chain = preds[i];
+      n = VEC_length (use_pred_info_t, one_chain);
+      for (j = 0; j < n; j++)
+        {
+          use_pred_info_t pred2
+              = VEC_index (use_pred_info_t, one_chain, j);
+          /* can relax the condition comparison to not
+             use address comparison. However, the most common
+             case is that multiple control dependent paths share
+             a common path prefix, so address comparison should
+             be ok.  */
+
+          if (pred2->cond == pred->cond
+              && pred2->invert == pred->invert)
+            {
+              found = true;
+              break;
+            }
+        }
+      if (!found)
+        return false;
+    }
+  return true;
+}
+
+/* Forward declaration.  */
+static bool
+is_use_properly_guarded (gimple use_stmt,
+                         basic_block use_bb,
+                         gimple phi,
+                         unsigned uninit_opnds,
+                         struct pointer_set_t *visited_phis);
+
+/* A helper function that determines if the predicate set
+   of the use is not overlapping with that of the uninit paths.
+   The most common senario of guarded use is in Example 1:
+     Example 1:
+           if (some_cond)
+           {
+              x = ...;
+              flag = true;
+           }
+
+            ... some code ...
+
+           if (flag)
+              use (x);
+
+     The real world examples are usually more complicated, but similar
+     and usually result from inlining:
+
+         bool init_func (int * x)
+         {
+             if (some_cond)
+                return false;
+             *x  =  ..
+             return true;
+         }
+
+         void foo(..)
+         {
+             int x;
+
+             if (!init_func(&x))
+                return;
+
+             .. some_code ...
+             use (x);
+         }
+
+     Another possible use scenario is in the following trivial example:
+
+     Example 2:
+          if (n > 0)
+             x = 1;
+          ...
+          if (n > 0)
+            {
+              if (m < 2)
+                 .. = x;
+            }
+
+     Predicate analysis needs to compute the composite predicate:
+
+       1) 'x' use predicate: (n > 0) .AND. (m < 2)
+       2) 'x' default value  (non-def) predicate: .NOT. (n > 0)
+       (the predicate chain for phi operand defs can be computed
+       starting from a bb that is control equivalent to the phi's
+       bb and is dominating the operand def.)
+
+       and check overlapping:
+          (n > 0) .AND. (m < 2) .AND. (.NOT. (n > 0))
+        <==> false
+
+     This implementation provides framework that can handle
+     scenarios. (Note that many simple cases are handled properly
+     without the predicate analysis -- this is due to jump threading
+     transformation which eliminates the merge point thus makes
+     path sensitive analysis unnecessary.)
+
+     NUM_PREDS is the number is the number predicate chains, PREDS is
+     the array of chains, PHI is the phi node whose incoming (undefined)
+     paths need to be pruned, and UNINIT_OPNDS is the bitmap holding
+     uninit operand positions. VISITED_PHIS is the pointer set of phi
+     stmts being checked.  */
+
+
+static bool
+use_pred_not_overlap_with_undef_path_pred (
+    size_t num_preds,
+    VEC(use_pred_info_t, heap) **preds,
+    gimple phi, unsigned uninit_opnds,
+    struct pointer_set_t *visited_phis)
+{
+  unsigned int i, n;
+  gimple flag_def = 0;
+  tree  boundary_cst = 0;
+  enum tree_code cmp_code;
+  bool swap_cond = false;
+  bool invert = false;
+  VEC(use_pred_info_t, heap) *the_pred_chain;
+
+  gcc_assert (num_preds > 0);
+  /* Find within the common prefix of multiple predicate chains
+     a predicate that is a comparison of a flag variable against
+     a constant.  */
+  the_pred_chain = preds[0];
+  n = VEC_length (use_pred_info_t, the_pred_chain);
+  for (i = 0; i < n; i++)
+    {
+      gimple cond;
+      tree cond_lhs, cond_rhs, flag = 0;
+
+      use_pred_info_t the_pred
+          = VEC_index (use_pred_info_t, the_pred_chain, i);
+
+      cond = the_pred->cond;
+      invert = the_pred->invert;
+      cond_lhs = gimple_cond_lhs (cond);
+      cond_rhs = gimple_cond_rhs (cond);
+      cmp_code = gimple_cond_code (cond);
+
+      if (cond_lhs != NULL_TREE && TREE_CODE (cond_lhs) == SSA_NAME
+          && cond_rhs != NULL_TREE && is_gimple_constant (cond_rhs))
+        {
+          boundary_cst = cond_rhs;
+          flag = cond_lhs;
+        }
+      else if (cond_rhs != NULL_TREE && TREE_CODE (cond_rhs) == SSA_NAME
+               && cond_lhs != NULL_TREE && is_gimple_constant (cond_lhs))
+        {
+          boundary_cst = cond_lhs;
+          flag = cond_rhs;
+          swap_cond = true;
+        }
+
+      if (!flag)
+        continue;
+
+      flag_def = SSA_NAME_DEF_STMT (flag);
+
+      if (!flag_def)
+        continue;
+
+      if ((gimple_code (flag_def) == GIMPLE_PHI)
+          && (gimple_bb (flag_def) == gimple_bb (phi))
+          && find_matching_predicate_in_rest_chains (
+              the_pred, preds, num_preds))
+        break;
+
+      flag_def = 0;
+    }
+
+  if (!flag_def)
+    return false;
+
+  /* Now check all the uninit incoming edge has a constant flag value
+     that is in conflict with the use guard/predicate.  */
+  cmp_code = get_cmp_code (cmp_code, swap_cond, invert);
+
+  if (cmp_code == ERROR_MARK)
+    return false;
+
+  for (i = 0; i < sizeof (unsigned); i++)
+    {
+      tree flag_arg;
+
+      if (!MASK_TEST_BIT (uninit_opnds, i))
+        continue;
+
+      flag_arg = gimple_phi_arg_def (flag_def, i);
+      if (!is_gimple_constant (flag_arg))
+        return false;
+
+      /* Now check if the constant is in the guarded range.  */
+      if (is_value_included_in (flag_arg, boundary_cst, cmp_code))
+        {
+          tree opnd;
+          gimple opnd_def;
+
+          /* Now that we know that this undefined edge is not
+             pruned. If the operand is defined by another phi,
+             we can further prune the incoming edges of that
+             phi by checking the predicates of this operands.  */
+
+          opnd = gimple_phi_arg_def (phi, i);
+          opnd_def = SSA_NAME_DEF_STMT (opnd);
+          if (gimple_code (opnd_def) == GIMPLE_PHI)
+            {
+              edge opnd_edge;
+              unsigned uninit_opnds2
+                  = compute_uninit_opnds_pos (opnd_def);
+              gcc_assert (!MASK_EMPTY (uninit_opnds2));
+              opnd_edge = gimple_phi_arg_edge (phi, i);
+              if (!is_use_properly_guarded (phi,
+                                            opnd_edge->src,
+                                            opnd_def,
+                                            uninit_opnds2,
+                                            visited_phis))
+                  return false;
+            }
+          else
+            return false;
+        }
+    }
+
+  return true;
+}
+
+/* Returns true if TC is AND or OR */
+
+static inline bool
+is_and_or_or (enum tree_code tc, tree typ)
+{
+  return (tc == TRUTH_AND_EXPR
+          || tc == TRUTH_OR_EXPR
+          || tc == BIT_IOR_EXPR
+          || (tc == BIT_AND_EXPR
+              && (typ == 0 || TREE_CODE (typ) == BOOLEAN_TYPE)));
+}
+
+typedef struct norm_cond
+{
+  VEC(gimple, heap) *conds;
+  enum tree_code cond_code;
+  bool invert;
+} *norm_cond_t;
+
+
+/* Normalizes gimple condition COND. The normalization follows
+   UD chains to form larger condition expression trees. NORM_COND
+   holds the normalized result. COND_CODE is the logical opcode
+   (AND or OR) of the normalized tree.  */
+
+static void
+normalize_cond_1 (gimple cond,
+                  norm_cond_t norm_cond,
+                  enum tree_code cond_code)
+{
+  enum gimple_code gc;
+  enum tree_code cur_cond_code;
+  tree rhs1, rhs2;
+
+  gc = gimple_code (cond);
+  if (gc != GIMPLE_ASSIGN)
+    {
+      VEC_safe_push (gimple, heap, norm_cond->conds, cond);
+      return;
+    }
+
+  cur_cond_code = gimple_assign_rhs_code (cond);
+  rhs1 = gimple_assign_rhs1 (cond);
+  rhs2 = gimple_assign_rhs2 (cond);
+  if (cur_cond_code == NE_EXPR)
+    {
+      if (integer_zerop (rhs2)
+          && (TREE_CODE (rhs1) == SSA_NAME))
+        normalize_cond_1 (
+            SSA_NAME_DEF_STMT (rhs1),
+            norm_cond, cond_code);
+      else if (integer_zerop (rhs1)
+               && (TREE_CODE (rhs2) == SSA_NAME))
+        normalize_cond_1 (
+            SSA_NAME_DEF_STMT (rhs2),
+            norm_cond, cond_code);
+      else
+        VEC_safe_push (gimple, heap, norm_cond->conds, cond);
+
+      return;
+    }
+
+  if (is_and_or_or (cur_cond_code, TREE_TYPE (rhs1))
+      && (cond_code == cur_cond_code || cond_code == ERROR_MARK)
+      && (TREE_CODE (rhs1) == SSA_NAME && TREE_CODE (rhs2) == SSA_NAME))
+    {
+      normalize_cond_1 (SSA_NAME_DEF_STMT (rhs1),
+                        norm_cond, cur_cond_code);
+      normalize_cond_1 (SSA_NAME_DEF_STMT (rhs2),
+                        norm_cond, cur_cond_code);
+      norm_cond->cond_code = cur_cond_code;
+    }
+  else
+    VEC_safe_push (gimple, heap, norm_cond->conds, cond);
+}
+
+/* See normalize_cond_1 for details. INVERT is a flag to indicate
+   if COND needs to be inverted or not.  */
+
+static void
+normalize_cond (gimple cond, norm_cond_t norm_cond, bool invert)
+{
+  enum tree_code cond_code;
+
+  norm_cond->cond_code = ERROR_MARK;
+  norm_cond->invert = false;
+  norm_cond->conds = NULL;
+  gcc_assert (gimple_code (cond) == GIMPLE_COND);
+  cond_code = gimple_cond_code (cond);
+  if (invert)
+    cond_code = invert_tree_comparison (cond_code, false);
+
+  if (cond_code == NE_EXPR)
+    {
+      if (integer_zerop (gimple_cond_rhs (cond))
+          && (TREE_CODE (gimple_cond_lhs (cond)) == SSA_NAME))
+        normalize_cond_1 (
+            SSA_NAME_DEF_STMT (gimple_cond_lhs (cond)),
+            norm_cond, ERROR_MARK);
+      else if (integer_zerop (gimple_cond_lhs (cond))
+               && (TREE_CODE (gimple_cond_rhs (cond)) == SSA_NAME))
+        normalize_cond_1 (
+            SSA_NAME_DEF_STMT (gimple_cond_rhs (cond)),
+            norm_cond, ERROR_MARK);
+      else
+        {
+          VEC_safe_push (gimple, heap, norm_cond->conds, cond);
+          norm_cond->invert = invert;
+        }
+    }
+  else
+    {
+      VEC_safe_push (gimple, heap, norm_cond->conds, cond);
+      norm_cond->invert = invert;
+    }
+
+  gcc_assert (VEC_length (gimple, norm_cond->conds) == 1
+              || is_and_or_or (norm_cond->cond_code, NULL));
+}
+
+/* Returns true if the domain for condition COND1 is a subset of
+   COND2. REVERSE is a flag. when it is true the function checks
+   if COND1 is a superset of COND2. INVERT1 and INVERT2 are flags
+   to indicate if COND1 and COND2 need to be inverted or not.  */
+
+static bool
+is_gcond_subset_of (gimple cond1, bool invert1,
+                    gimple cond2, bool invert2,
+                    bool reverse)
+{
+  enum gimple_code gc1, gc2;
+  enum tree_code cond1_code, cond2_code;
+  gimple tmp;
+  tree cond1_lhs, cond1_rhs, cond2_lhs, cond2_rhs;
+
+  /* Take the short cut.  */
+  if (cond1 == cond2)
+    return true;
+
+  if (reverse)
+    {
+      tmp = cond1;
+      cond1 = cond2;
+      cond2 = tmp;
+    }
+
+  gc1 = gimple_code (cond1);
+  gc2 = gimple_code (cond2);
+
+  if ((gc1 != GIMPLE_ASSIGN && gc1 != GIMPLE_COND)
+      || (gc2 != GIMPLE_ASSIGN && gc2 != GIMPLE_COND))
+    return cond1 == cond2;
+
+  cond1_code = ((gc1 == GIMPLE_ASSIGN)
+                ? gimple_assign_rhs_code (cond1)
+                : gimple_cond_code (cond1));
+
+  cond2_code = ((gc2 == GIMPLE_ASSIGN)
+                ? gimple_assign_rhs_code (cond2)
+                : gimple_cond_code (cond2));
+
+  if (TREE_CODE_CLASS (cond1_code) != tcc_comparison
+      || TREE_CODE_CLASS (cond2_code) != tcc_comparison)
+    return false;
+
+  if (invert1)
+    cond1_code = invert_tree_comparison (cond1_code, false);
+  if (invert2)
+    cond2_code = invert_tree_comparison (cond2_code, false);
+
+  cond1_lhs = ((gc1 == GIMPLE_ASSIGN)
+               ? gimple_assign_rhs1 (cond1)
+               : gimple_cond_lhs (cond1));
+  cond1_rhs = ((gc1 == GIMPLE_ASSIGN)
+               ? gimple_assign_rhs2 (cond1)
+               : gimple_cond_rhs (cond1));
+  cond2_lhs = ((gc2 == GIMPLE_ASSIGN)
+               ? gimple_assign_rhs1 (cond2)
+               : gimple_cond_lhs (cond2));
+  cond2_rhs = ((gc2 == GIMPLE_ASSIGN)
+               ? gimple_assign_rhs2 (cond2)
+               : gimple_cond_rhs (cond2));
+
+  /* Assuming const operands have been swapped to the
+     rhs at this point of the analysis.  */
+
+  if (cond1_lhs != cond2_lhs)
+    return false;
+
+  if (!is_gimple_constant (cond1_rhs)
+      || TREE_CODE (cond1_rhs) != INTEGER_CST)
+    return (cond1_rhs == cond2_rhs);
+
+  if (!is_gimple_constant (cond2_rhs)
+      || TREE_CODE (cond2_rhs) != INTEGER_CST)
+    return (cond1_rhs == cond2_rhs);
+
+  if (cond1_code == EQ_EXPR)
+    return is_value_included_in (cond1_rhs,
+                                 cond2_rhs, cond2_code);
+  if (cond1_code == NE_EXPR || cond2_code == EQ_EXPR)
+    return ((cond2_code == cond1_code)
+            && tree_int_cst_equal (cond1_rhs, cond2_rhs));
+
+  if (((cond1_code == GE_EXPR || cond1_code == GT_EXPR)
+       && (cond2_code == LE_EXPR || cond2_code == LT_EXPR))
+      || ((cond1_code == LE_EXPR || cond1_code == LT_EXPR)
+          && (cond2_code == GE_EXPR || cond2_code == GT_EXPR)))
+    return false;
+
+  if (cond1_code != GE_EXPR && cond1_code != GT_EXPR
+      && cond1_code != LE_EXPR && cond1_code != LT_EXPR)
+    return false;
+
+  if (cond1_code == GT_EXPR)
+    {
+      cond1_code = GE_EXPR;
+      cond1_rhs = fold_binary (PLUS_EXPR, TREE_TYPE (cond1_rhs),
+                               cond1_rhs,
+                               fold_convert (TREE_TYPE (cond1_rhs),
+                                             integer_one_node));
+    }
+  else if (cond1_code == LT_EXPR)
+    {
+      cond1_code = LE_EXPR;
+      cond1_rhs = fold_binary (MINUS_EXPR, TREE_TYPE (cond1_rhs),
+                               cond1_rhs,
+                               fold_convert (TREE_TYPE (cond1_rhs),
+                                             integer_one_node));
+    }
+
+  if (!cond1_rhs)
+    return false;
+
+  gcc_assert (cond1_code == GE_EXPR || cond1_code == LE_EXPR);
+
+  if (cond2_code == GE_EXPR || cond2_code == GT_EXPR ||
+      cond2_code == LE_EXPR || cond2_code == LT_EXPR)
+    return is_value_included_in (cond1_rhs,
+                                 cond2_rhs, cond2_code);
+  else if (cond2_code == NE_EXPR)
+    return
+        (is_value_included_in (cond1_rhs,
+                               cond2_rhs, cond2_code)
+         && !is_value_included_in (cond2_rhs,
+                                   cond1_rhs, cond1_code));
+  return false;
+}
+
+/* Returns true if the domain of the condition expression 
+   in COND is a subset of any of the sub-conditions
+   of the normalized condtion NORM_COND.  INVERT is a flag
+   to indicate of the COND needs to be inverted.
+   REVERSE is a flag. When it is true, the check is reversed --
+   it returns true if COND is a superset of any of the subconditions
+   of NORM_COND.  */
+
+static bool
+is_subset_of_any (gimple cond, bool invert,
+                  norm_cond_t norm_cond, bool reverse)
+{
+  size_t i;
+  size_t len = VEC_length (gimple, norm_cond->conds);
+
+  for (i = 0; i < len; i++)
+    {
+      if (is_gcond_subset_of (cond, invert,
+                              VEC_index (gimple, norm_cond->conds, i),
+                              false, reverse))
+        return true;
+    }
+  return false;
+}
+
+/* NORM_COND1 and NORM_COND2 are normalized logical/BIT OR
+   expressions (formed by following UD chains not control
+   dependence chains). The function returns true of domain
+   of and expression NORM_COND1 is a subset of NORM_COND2's.
+   The implementation is conservative, and it returns false if
+   it the inclusion relationship may not hold.  */
+
+static bool
+is_or_set_subset_of (norm_cond_t norm_cond1,
+                     norm_cond_t norm_cond2)
+{
+  size_t i;
+  size_t len = VEC_length (gimple, norm_cond1->conds);
+
+  for (i = 0; i < len; i++)
+    {
+      if (!is_subset_of_any (VEC_index (gimple, norm_cond1->conds, i),
+                             false, norm_cond2, false))
+        return false;
+    }
+  return true;
+}
+
+/* NORM_COND1 and NORM_COND2 are normalized logical AND
+   expressions (formed by following UD chains not control
+   dependence chains). The function returns true of domain
+   of and expression NORM_COND1 is a subset of NORM_COND2's.  */
+
+static bool
+is_and_set_subset_of (norm_cond_t norm_cond1,
+                      norm_cond_t norm_cond2)
+{
+  size_t i;
+  size_t len = VEC_length (gimple, norm_cond2->conds);
+
+  for (i = 0; i < len; i++)
+    {
+      if (!is_subset_of_any (VEC_index (gimple, norm_cond2->conds, i),
+                             false, norm_cond1, true))
+        return false;
+    }
+  return true;
+}
+
+/* Returns true of the domain if NORM_COND1 is a subset 
+   of that of NORM_COND2. Returns false if it can not be 
+   proved to be so.  */
+
+static bool
+is_norm_cond_subset_of (norm_cond_t norm_cond1,
+                        norm_cond_t norm_cond2)
+{
+  size_t i;
+  enum tree_code code1, code2;
+
+  code1 = norm_cond1->cond_code;
+  code2 = norm_cond2->cond_code;
+
+  if (code1 == TRUTH_AND_EXPR || code1 == BIT_AND_EXPR)
+    {
+      /* Both conditions are AND expressions.  */
+      if (code2 == TRUTH_AND_EXPR || code2 == BIT_AND_EXPR)
+        return is_and_set_subset_of (norm_cond1, norm_cond2);
+      /* NORM_COND1 is an AND expression, and NORM_COND2 is an OR
+         expression. In this case, returns true if any subexpression
+         of NORM_COND1 is a subset of any subexpression of NORM_COND2.  */
+      else if (code2 == TRUTH_OR_EXPR || code2 == BIT_IOR_EXPR)
+        {
+          size_t len1;
+          len1 = VEC_length (gimple, norm_cond1->conds);
+          for (i = 0; i < len1; i++)
+            {
+              gimple cond1 = VEC_index (gimple, norm_cond1->conds, i);
+              if (is_subset_of_any (cond1, false, norm_cond2, false))
+                return true;
+            }
+          return false;
+        }
+      else
+        {
+          gcc_assert (code2 == ERROR_MARK);
+          gcc_assert (VEC_length (gimple, norm_cond2->conds) == 1);
+          return is_subset_of_any (VEC_index (gimple, norm_cond2->conds, 0),
+                                   norm_cond2->invert, norm_cond1, true);
+        }
+    }
+  /* NORM_COND1 is an OR expression  */
+  else if (code1 == TRUTH_OR_EXPR || code1 == BIT_IOR_EXPR)
+    {
+      if (code2 != code1)
+        return false;
+
+      return is_or_set_subset_of (norm_cond1, norm_cond2);
+    }
+  else
+    {
+      gcc_assert (code1 == ERROR_MARK);
+      gcc_assert (VEC_length (gimple, norm_cond1->conds) == 1);
+      /* Conservatively returns false if NORM_COND1 is non-decomposible
+         and NORM_COND2 is an AND expression.  */
+      if (code2 == TRUTH_AND_EXPR || code2 == BIT_AND_EXPR)
+        return false;
+
+      if (code2 == TRUTH_OR_EXPR || code2 == BIT_IOR_EXPR)
+        return is_subset_of_any (VEC_index (gimple, norm_cond1->conds, 0),
+                                 norm_cond1->invert, norm_cond2, false);
+
+      gcc_assert (code2 == ERROR_MARK);
+      gcc_assert (VEC_length (gimple, norm_cond2->conds) == 1);
+      return is_gcond_subset_of (VEC_index (gimple, norm_cond1->conds, 0),
+                                 norm_cond1->invert,
+                                 VEC_index (gimple, norm_cond2->conds, 0),
+                                 norm_cond2->invert, false);
+    }
+}
+
+/* Returns true of the domain of single predicate expression
+   EXPR1 is a subset of that of EXPR2. Returns false if it
+   can not be proved.  */
+
+static bool
+is_pred_expr_subset_of (use_pred_info_t expr1,
+                        use_pred_info_t expr2)
+{
+  gimple cond1, cond2;
+  enum tree_code code1, code2;
+  struct norm_cond norm_cond1, norm_cond2;
+  bool is_subset = false;
+
+  cond1 = expr1->cond;
+  cond2 = expr2->cond;
+  code1 = gimple_cond_code (cond1);
+  code2 = gimple_cond_code (cond2);
+
+  if (expr1->invert)
+    code1 = invert_tree_comparison (code1, false);
+  if (expr2->invert)
+    code2 = invert_tree_comparison (code2, false);
+
+  /* Fast path -- match exactly  */
+  if ((gimple_cond_lhs (cond1) == gimple_cond_lhs (cond2))
+      && (gimple_cond_rhs (cond1) == gimple_cond_rhs (cond2))
+      && (code1 == code2))
+    return true;
+
+  /* Normalize conditions. To keep NE_EXPR, do not invert
+     with both need inversion.  */
+  normalize_cond (cond1, &norm_cond1, (expr1->invert));
+  normalize_cond (cond2, &norm_cond2, (expr2->invert));
+
+  is_subset = is_norm_cond_subset_of (&norm_cond1, &norm_cond2);
+
+  /* Free memory  */
+  VEC_free (gimple, heap, norm_cond1.conds);
+  VEC_free (gimple, heap, norm_cond2.conds);
+  return is_subset ;
+}
+
+/* Returns true if the domain of PRED1 is a subset
+   of that of PRED2. Returns false if it can not be proved so.  */
+
+static bool
+is_pred_chain_subset_of (VEC(use_pred_info_t, heap) *pred1,
+                         VEC(use_pred_info_t, heap) *pred2)
+{
+  size_t np1, np2, i1, i2;
+
+  np1 = VEC_length (use_pred_info_t, pred1);
+  np2 = VEC_length (use_pred_info_t, pred2);
+
+  for (i2 = 0; i2 < np2; i2++)
+    {
+      bool found = false;
+      use_pred_info_t info2
+          = VEC_index (use_pred_info_t, pred2, i2);
+      for (i1 = 0; i1 < np1; i1++)
+        {
+          use_pred_info_t info1
+              = VEC_index (use_pred_info_t, pred1, i1);
+          if (is_pred_expr_subset_of (info1, info2))
+            {
+              found = true;
+              break;
+            }
+        }
+      if (!found)
+        return false;
+    }
+  return true;
+}
+
+/* Returns true if the domain defined by
+   one pred chain ONE_PRED is a subset of the domain
+   of *PREDS. It returns false if ONE_PRED's domain is
+   not a subset of any of the sub-domains of PREDS (
+   corresponding to each individual chains in it), even
+   though it may be still be a subset of whole domain
+   of PREDS which is the union (ORed) of all its subdomains.
+   In other words, the result is conservative.  */
+
+static bool
+is_included_in (VEC(use_pred_info_t, heap) *one_pred,
+                VEC(use_pred_info_t, heap) **preds,
+                size_t n)
+{
+  size_t i;
+
+  for (i = 0; i < n; i++)
+    {
+      if (is_pred_chain_subset_of (one_pred, preds[i]))
+        return true;
+    }
+
+  return false;
+}
+
+/* compares two predicate sets PREDS1 and PREDS2 and returns
+   true if the domain defined by PREDS1 is a superset
+   of PREDS2's domain. N1 and N2 are array sizes of PREDS1 and
+   PREDS2 respectively. The implementation chooses not to build
+   generic trees (and relying on the folding capability of the
+   compiler), but instead performs brute force comparison of
+   individual predicate chains (won't be a compile time problem
+   as the chains are pretty short). When the function returns
+   false, it does not necessarily mean *PREDS1 is not a superset
+   of *PREDS2, but mean it may not be so since the analysis can
+   not prove it. In such cases, false warnings may still be
+   emitted.  */
+
+static bool
+is_superset_of (VEC(use_pred_info_t, heap) **preds1,
+                size_t n1,
+                VEC(use_pred_info_t, heap) **preds2,
+                size_t n2)
+{
+  size_t i;
+  VEC(use_pred_info_t, heap) *one_pred_chain;
+
+  for (i = 0; i < n2; i++)
+    {
+      one_pred_chain = preds2[i];
+      if (!is_included_in (one_pred_chain, preds1, n1))
+        return false;
+    }
+
+  return true;
+}
+
+/* Computes the predicates that guard the use and checks
+   if the incoming paths that have empty (or possibly
+   empty) defintion can be pruned/filtered. The function returns
+   true if it can be determined that the use of PHI's def in
+   USE_STMT is guarded with a predicate set not overlapping with
+   predicate sets of all runtime paths that do not have a definition.
+   Returns false if it is not or it can not be determined. USE_BB is
+   the bb of the use (for phi operand use, the bb is not the bb of
+   the phi stmt, but the src bb of the operand edge). UNINIT_OPNDS
+   is a bit vector. If an operand of PHI is uninitialized, the
+   correponding bit in the vector is 1.  VISIED_PHIS is a pointer
+   set of phis being visted.  */
+
+static bool
+is_use_properly_guarded (gimple use_stmt,
+                         basic_block use_bb,
+                         gimple phi,
+                         unsigned uninit_opnds,
+                         struct pointer_set_t *visited_phis)
+{
+  basic_block phi_bb;
+  VEC(use_pred_info_t, heap) **preds = 0;
+  VEC(use_pred_info_t, heap) **def_preds = 0;
+  size_t num_preds = 0, num_def_preds = 0;
+  bool has_valid_preds = false;
+  bool is_properly_guarded = false;
+
+  if (pointer_set_insert (visited_phis, phi))
+    return false;
+
+  phi_bb = gimple_bb (phi);
+
+  if (is_non_loop_exit_postdominating (use_bb, phi_bb))
+    return false;
+
+  has_valid_preds = find_predicates (&preds, &num_preds,
+                                     phi_bb, use_bb);
+
+  if (!has_valid_preds)
+    {
+      destroy_predicate_vecs (num_preds, preds);
+      return false;
+    }
+
+  if (dump_file)
+    dump_predicates (use_stmt, num_preds, preds,
+                     "Use in stmt ");
+
+  has_valid_preds = find_def_preds (&def_preds,
+                                    &num_def_preds, phi);
+
+  if (has_valid_preds)
+    {
+      if (dump_file)
+        dump_predicates (phi, num_def_preds, def_preds,
+                         "Operand defs of phi ");
+      is_properly_guarded =
+          is_superset_of (def_preds, num_def_preds,
+                          preds, num_preds);
+    }
+
+  /* further prune the dead incoming phi edges. */
+  if (!is_properly_guarded)
+    is_properly_guarded
+        = use_pred_not_overlap_with_undef_path_pred (
+            num_preds, preds, phi, uninit_opnds, visited_phis);
+
+  destroy_predicate_vecs (num_preds, preds);
+  destroy_predicate_vecs (num_def_preds, def_preds);
+  return is_properly_guarded;
+}
+
+/* Searches through all uses of a potentially
+   uninitialized variable defined by PHI and returns a use
+   statement if the use is not properly guarded. It returns
+   NULL if all uses are guarded. UNINIT_OPNDS is a bitvector
+   holding the position(s) of uninit PHI operands. WORKLIST
+   is the vector of candidate phis that may be updated by this
+   function. ADDED_TO_WORKLIST is the pointer set tracking
+   if the new phi is already in the worklist.  */
+
+static gimple
+find_uninit_use (gimple phi, unsigned uninit_opnds,
+                 VEC(gimple, heap) **worklist,
+		 struct pointer_set_t *added_to_worklist)
+{
+  tree phi_result;
+  use_operand_p use_p;
+  gimple use_stmt;
+  imm_use_iterator iter;
+
+  phi_result = gimple_phi_result (phi);
+
+  FOR_EACH_IMM_USE_FAST (use_p, iter, phi_result)
+    {
+      struct pointer_set_t *visited_phis;
+      basic_block use_bb;
+
+      use_stmt = use_p->loc.stmt;
+
+      visited_phis = pointer_set_create ();
+
+      use_bb = gimple_bb (use_stmt);
+      if (gimple_code (use_stmt) == GIMPLE_PHI)
+        {
+	  unsigned i, n;
+          n = gimple_phi_num_args (use_stmt);
+
+          /* Find the matching phi argument of the use.  */
+          for (i = 0; i < n; ++i)
+            {
+               if (gimple_phi_arg_def_ptr (use_stmt, i) == use_p->use)
+	         {
+		    edge e = gimple_phi_arg_edge (use_stmt, i);
+		    use_bb = e->src;
+                    break;
+		 }
+	    }
+	}
+
+      if (is_use_properly_guarded (use_stmt,
+                                   use_bb, 
+                                   phi,
+                                   uninit_opnds,
+                                   visited_phis))
+        {
+          pointer_set_destroy (visited_phis);
+          continue;
+        }
+      pointer_set_destroy (visited_phis);
+
+      /* Found one real use, return.  */
+      if (gimple_code (use_stmt) != GIMPLE_PHI)
+         return use_stmt;
+
+      /* Found a phi use that is not guarded,
+         add the phi to the worklist.  */
+      if (!pointer_set_insert (added_to_worklist,
+                               use_stmt))
+        {
+          VEC_safe_push (gimple, heap, *worklist, use_stmt);
+          pointer_set_insert (possibly_undefined_names,
+	                      phi_result);
+        }
+    }
+
+  return NULL;
+}
+
+/* Look for inputs to PHI that are SSA_NAMEs that have empty definitions
+   and gives warning if there exists a runtime path from the entry to a
+   use of the PHI def that does not contain a definition. In other words,
+   the warning is on the real use. The more dead paths that can be pruned
+   by the compiler, the fewer false positives the warning is. WORKLIST
+   is a vector of candidate phis to be examined. ADDED_TO_WORKLIST is
+   a pointer set tracking if the new phi is added to the worklist or not.  */
+
+static void
+warn_uninitialized_phi (gimple phi, VEC(gimple, heap) **worklist,
+                        struct pointer_set_t *added_to_worklist)
+{
+  unsigned uninit_opnds;
+  gimple uninit_use_stmt = 0;
+  tree uninit_op;
+
+  /* Don't look at memory tags.  */
+  if (!is_gimple_reg (gimple_phi_result (phi)))
+    return;
+
+  uninit_opnds = compute_uninit_opnds_pos (phi);
+
+  if  (MASK_EMPTY (uninit_opnds))
+    return;
+
+  /* Now check if we have any use of the value without proper guard.  */
+  uninit_use_stmt = find_uninit_use (phi, uninit_opnds,
+                                     worklist, added_to_worklist);
+
+  /* All uses are properly guarded.  */
+  if (!uninit_use_stmt)
+    return;
+
+  uninit_op = gimple_phi_arg_def (phi, MASK_FIRST_SET_BIT (uninit_opnds));
+  warn_uninit (uninit_op,
+               "%qD may be used uninitialized in this function",
+               uninit_use_stmt);
+
+}
+
+
+/* Entry point to the late uninitialized warning pass.  */
+
+static unsigned int
+execute_late_warn_uninitialized (void)
+{
+  basic_block bb;
+  gimple_stmt_iterator gsi;
+  VEC(gimple, heap) *worklist = 0;
+  struct pointer_set_t *added_to_worklist;
+
+  calculate_dominance_info (CDI_DOMINATORS);
+  calculate_dominance_info (CDI_POST_DOMINATORS);
+  /* Re-do the plain uninitialized variable check, as optimization may have
+     straightened control flow.  Do this first so that we don't accidentally
+     get a "may be" warning when we'd have seen an "is" warning later.  */
+  warn_uninitialized_vars (/*warn_possibly_uninitialized=*/1);
+
+  timevar_push (TV_TREE_UNINIT);
+
+  possibly_undefined_names = pointer_set_create ();
+  added_to_worklist = pointer_set_create ();
+
+  /* Initialize worklist  */
+  FOR_EACH_BB (bb)
+    for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
+      {
+        gimple phi = gsi_stmt (gsi);
+        size_t n, i;
+
+        n = gimple_phi_num_args (phi);
+
+        /* Don't look at memory tags.  */
+        if (!is_gimple_reg (gimple_phi_result (phi)))
+          continue;
+
+        for (i = 0; i < n; ++i)
+          {
+            tree op = gimple_phi_arg_def (phi, i);
+            if (TREE_CODE (op) == SSA_NAME
+                && ssa_undefined_value_p (op))
+              {
+                VEC_safe_push (gimple, heap, worklist, phi);
+		pointer_set_insert (added_to_worklist, phi);
+                break;
+              }
+          }
+      }
+
+  while (VEC_length (gimple, worklist) != 0)
+    {
+      gimple cur_phi = 0;
+      cur_phi = VEC_pop (gimple, worklist);
+      warn_uninitialized_phi (cur_phi, &worklist, added_to_worklist);
+    }
+  
+  VEC_free (gimple, heap, worklist);
+  pointer_set_destroy (added_to_worklist);
+  pointer_set_destroy (possibly_undefined_names);
+  possibly_undefined_names = NULL;
+  free_dominance_info (CDI_POST_DOMINATORS);
+  timevar_pop (TV_TREE_UNINIT);
+  return 0;
+}
+
+static bool
+gate_warn_uninitialized (void)
+{
+  return warn_uninitialized != 0;
+}
+
+struct gimple_opt_pass pass_late_warn_uninitialized =
+{
+ {
+  GIMPLE_PASS,
+  "uninit",				/* name */
+  gate_warn_uninitialized,		/* gate */
+  execute_late_warn_uninitialized,	/* execute */
+  NULL,					/* sub */
+  NULL,					/* next */
+  0,					/* static_pass_number */
+  TV_NONE,     	        		/* tv_id */
+  PROP_ssa,				/* properties_required */
+  0,					/* properties_provided */
+  0,					/* properties_destroyed */
+  0,					/* todo_flags_start */
+  0                                     /* todo_flags_finish */
+ }
+};