Update.

2002-10-11  Isamu Hasegawa  <isamu@yamato.ibm.com>

	* posix/regcomp.c (re_compile_fastmap_iter): Remove the handling
	OP_CONTEXT_NODE.
	(regfree): Likewise.
	(create_initial_state): Likewise.
	(analyze): Remove the substitutions which became useless.
	(calc_first): Likewise.
	(calc_epsdest): Use edests of OP_BACK_REF in case that it has
	epsilon destination.
	(duplicate_node_closure): New function.
	(duplicate_node): Remove the handling OP_CONTEXT_NODE.
	(calc_inveclosure): Likewise.
	(calc_eclosure): Likewise.
	(calc_eclosure_iter): Invoke duplicate_node_closure instead of
	direct invocation of duplicate_node.
	(parse): Don't use comma operator in the return to avoid compiler
	warning.
	(parse_reg_exp): Likewise.
	(parse_branch): Likewise.
	(parse_expression): Likewise.
	(parse_sub_exp): Likewise.
	(parse_dup_op): Likewise.
	* posix/regex_internal.c (re_dfa_add_node): Remove the substitutions
	which became useless.
	(create_ci_newstate): Remove the handling OP_CONTEXT_NODE.
	(create_cd_newstate): Likewise.
	* posix/regex_internal.h (re_token_type_t): Remove the obsolete type.
	(re_token_t): Likewise.
	(re_dfa_t): Likewise.
	(re_node_set_remove): New macro.
	* posix/regexec.c (check_matching): Remove the handling
	OP_CONTEXT_NODE.
	(check_halt_node_context): Likewise.
	(proceed_next_node): Likewise.
	(pop_fail_stack): Fix the memory leak.
	(set_regs): Likewise.
	(free_fail_stack_return): New function.
	(sift_states_backward): Fix the memory leak.  Remove the handling
	OP_CONTEXT_NODE.
	(update_cur_sifted_state): Append some if clause to avoid redundant
	call.
	(sub_epsilon_src_nodes): Use IS_EPSILON_NODE since it might be a
	back reference.
	(check_dst_limits): Remove the handling OP_CONTEXT_NODE.
	(check_subexp_limits): Likewise.
	(search_subexp): Likewise.
	(sift_states_bkref): Likewise.
	(transit_state_mb): Likewise.
	(transit_state_bkref_loop): Likewise.
	(transit_state_bkref_loop): Likewise.
	(group_nodes_into_DFAstates): Likewise.
	(check_node_accept): Likewise.
	(sift_ctx_init): Add initializing.

2002-10-12  Ulrich Drepper  <drepper@redhat.com>

	* sysdeps/unix/sysv/linux/i386/sysdep.h (INLINE_SYSCALL): Use
	__builtin_expect.

4 files changed, 303 insertions, 345 deletions

diff --git a/posix/regcomp.c b/posix/regcomp.c
index 7917c64..715dd0f 100644
--- a/posix/regcomp.c
+++ b/posix/regcomp.c
@@ -85,6 +85,9 @@ static reg_errcode_t analyze_tree (re_dfa_t *dfa, bin_tree_t *node);
 static void calc_first (re_dfa_t *dfa, bin_tree_t *node);
 static void calc_next (re_dfa_t *dfa, bin_tree_t *node);
 static void calc_epsdest (re_dfa_t *dfa, bin_tree_t *node);
+static reg_errcode_t duplicate_node_closure (re_dfa_t *dfa, int top_org_node,
+                                             int top_clone_node, int root_node,
+                                             unsigned int constraint);
 static reg_errcode_t duplicate_node (int *new_idx, re_dfa_t *dfa, int org_idx,
                                      unsigned int constraint);
 static reg_errcode_t calc_eclosure (re_dfa_t *dfa);
@@ -351,11 +354,6 @@ re_compile_fastmap_iter (bufp, init_state, fastmap)
     {
       int node = init_state->nodes.elems[node_cnt];
       re_token_type_t type = dfa->nodes[node].type;
-      if (type == OP_CONTEXT_NODE)
-        {
-          node = dfa->nodes[node].opr.ctx_info->entity;
-          type = dfa->nodes[node].type;
-        }
 
       if (type == CHARACTER)
         fastmap[dfa->nodes[node].opr.c] = 1;
@@ -587,18 +585,7 @@ regfree (preg)
 #endif /* RE_ENABLE_I18N */
           if (node->type == SIMPLE_BRACKET && node->duplicated == 0)
             re_free (node->opr.sbcset);
-          else if (node->type == OP_CONTEXT_NODE)
-            {
-              if (dfa->nodes[node->opr.ctx_info->entity].type == OP_BACK_REF)
-                {
-                  if (node->opr.ctx_info->bkref_eclosure != NULL)
-                    re_node_set_free (node->opr.ctx_info->bkref_eclosure);
-                  re_free (node->opr.ctx_info->bkref_eclosure);
-                }
-              re_free (node->opr.ctx_info);
-            }
         }
-      re_free (dfa->firsts);
       re_free (dfa->nexts);
       for (i = 0; i < dfa->nodes_len; ++i)
         {
@@ -883,39 +870,25 @@ create_initial_state (dfa)
         re_token_type_t type = dfa->nodes[node_idx].type;
 
         int clexp_idx;
-        int entity = (type != OP_CONTEXT_NODE ? node_idx
-                      : dfa->nodes[node_idx].opr.ctx_info->entity);
-        if ((type != OP_CONTEXT_NODE
-             || (dfa->nodes[entity].type != OP_BACK_REF))
-            && (type != OP_BACK_REF))
+        if (type != OP_BACK_REF)
           continue;
         for (clexp_idx = 0; clexp_idx < init_nodes.nelem; ++clexp_idx)
           {
             re_token_t *clexp_node;
             clexp_node = dfa->nodes + init_nodes.elems[clexp_idx];
             if (clexp_node->type == OP_CLOSE_SUBEXP
-                && clexp_node->opr.idx + 1 == dfa->nodes[entity].opr.idx)
+                && clexp_node->opr.idx + 1 == dfa->nodes[node_idx].opr.idx)
               break;
           }
         if (clexp_idx == init_nodes.nelem)
           continue;
 
-        if (type == OP_CONTEXT_NODE
-            && (dfa->nodes[dfa->nodes[node_idx].opr.ctx_info->entity].type
-                == OP_BACK_REF))
-          {
-            int prev_nelem = init_nodes.nelem;
-            re_node_set_merge (&init_nodes,
-                           dfa->nodes[node_idx].opr.ctx_info->bkref_eclosure);
-            if (prev_nelem < init_nodes.nelem)
-              i = 0;
-          }
-        else if (type == OP_BACK_REF)
+        if (type == OP_BACK_REF)
           {
-            int next_idx = dfa->nexts[node_idx];
-            if (!re_node_set_contains (&init_nodes, next_idx))
+            int dest_idx = dfa->edests[node_idx].elems[0];
+            if (!re_node_set_contains (&init_nodes, dest_idx))
               {
-                re_node_set_merge (&init_nodes, dfa->eclosures + next_idx);
+                re_node_set_merge (&init_nodes, dfa->eclosures + dest_idx);
                 i = 0;
               }
           }
@@ -959,18 +932,16 @@ analyze (dfa)
   reg_errcode_t ret;
 
   /* Allocate arrays.  */
-  dfa->firsts = re_malloc (int, dfa->nodes_alloc);
   dfa->nexts = re_malloc (int, dfa->nodes_alloc);
   dfa->edests = re_malloc (re_node_set, dfa->nodes_alloc);
   dfa->eclosures = re_malloc (re_node_set, dfa->nodes_alloc);
   dfa->inveclosures = re_malloc (re_node_set, dfa->nodes_alloc);
-  if (BE (dfa->firsts == NULL || dfa->nexts == NULL || dfa->edests == NULL
+  if (BE (dfa->nexts == NULL || dfa->edests == NULL
           || dfa->eclosures == NULL || dfa->inveclosures == NULL, 0))
     return REG_ESPACE;
   /* Initialize them.  */
   for (i = 0; i < dfa->nodes_len; ++i)
     {
-      dfa->firsts[i] = -1;
       dfa->nexts[i] = -1;
       re_node_set_init_empty (dfa->edests + i);
       re_node_set_init_empty (dfa->eclosures + i);
@@ -1083,8 +1054,6 @@ calc_first (dfa, node)
       node->first = node->left->first;
       break;
     }
-  if (node->type == 0)
-    dfa->firsts[idx] = node->first;
 }
 
 /* Calculate "next" for the node NODE.  */
@@ -1187,11 +1156,114 @@ calc_epsdest (dfa, node)
         }
       else if (dfa->nodes[idx].type == ANCHOR
                || dfa->nodes[idx].type == OP_OPEN_SUBEXP
-               || dfa->nodes[idx].type == OP_CLOSE_SUBEXP)
+               || dfa->nodes[idx].type == OP_CLOSE_SUBEXP
+               || dfa->nodes[idx].type == OP_BACK_REF)
         re_node_set_init_1 (dfa->edests + idx, node->next);
     }
 }
 
+/* Duplicate the epsilon closure of the node ROOT_NODE.
+   Note that duplicated nodes have constraint INIT_CONSTRAINT in addition
+   to their own constraint.  */
+
+static reg_errcode_t
+duplicate_node_closure (dfa, top_org_node, top_clone_node, root_node,
+                        init_constraint)
+     re_dfa_t *dfa;
+     int top_org_node, top_clone_node, root_node;
+     unsigned int init_constraint;
+{
+  reg_errcode_t err;
+  int org_node, clone_node, ret;
+  unsigned int constraint = init_constraint;
+  for (org_node = top_org_node, clone_node = top_clone_node;;)
+    {
+      int org_dest, clone_dest;
+      if (dfa->nodes[org_node].type == OP_BACK_REF)
+        {
+	  /* If the back reference epsilon-transit, its destination must
+	     also have the constraint.  Then duplicate the epsilon closure
+	     of the destination of the back reference, and store it in
+	     edests of the back reference.  */
+          org_dest = dfa->nexts[org_node];
+          re_node_set_empty (dfa->edests + clone_node);
+          err = duplicate_node (&clone_dest, dfa, org_dest, constraint);
+          if (BE (err != REG_NOERROR, 0))
+            return err;
+          dfa->nexts[clone_node] = dfa->nexts[org_node];
+          ret = re_node_set_insert (dfa->edests + clone_node, clone_dest);
+          if (BE (ret < 0, 0))
+            return REG_ESPACE;
+        }
+      else if (dfa->edests[org_node].nelem == 0)
+        {
+	  /* In case of the node can't epsilon-transit, don't duplicate the
+	     destination and store the original destination as the
+	     destination of the node.  */
+          dfa->nexts[clone_node] = dfa->nexts[org_node];
+          break;
+        }
+      else if (dfa->edests[org_node].nelem == 1)
+        {
+	  /* In case of the node can epsilon-transit, and it has only one
+	     destination.  */
+          org_dest = dfa->edests[org_node].elems[0];
+          re_node_set_empty (dfa->edests + clone_node);
+          if (dfa->nodes[org_node].type == ANCHOR)
+            {
+	      /* In case of the node has another constraint, append it.  */
+              if (org_node == root_node && clone_node != org_node)
+                {
+		  /* ...but if the node is root_node itself, it means the
+		     epsilon closure have a loop, then tie it to the
+		     destination of the root_node.  */
+                  ret = re_node_set_insert (dfa->edests + clone_node,
+                                            org_dest);
+                  if (BE (ret < 0, 0))
+                    return REG_ESPACE;
+                  break;
+                }
+              constraint |= dfa->nodes[org_node].opr.ctx_type;
+            }
+          err = duplicate_node (&clone_dest, dfa, org_dest, constraint);
+          if (BE (err != REG_NOERROR, 0))
+            return err;
+          ret = re_node_set_insert (dfa->edests + clone_node, clone_dest);
+          if (BE (ret < 0, 0))
+            return REG_ESPACE;
+        }
+      else /* dfa->edests[org_node].nelem == 2 */
+        {
+	  /* In case of the node can epsilon-transit, and it has two
+	     destinations.  */
+          org_dest = dfa->edests[org_node].elems[0];
+          re_node_set_empty (dfa->edests + clone_node);
+          err = duplicate_node (&clone_dest, dfa, org_dest, constraint);
+          if (BE (err != REG_NOERROR, 0))
+            return err;
+          ret = re_node_set_insert (dfa->edests + clone_node, clone_dest);
+          if (BE (ret < 0, 0))
+            return REG_ESPACE;
+
+          err = duplicate_node_closure (dfa, org_dest, clone_dest, root_node,
+                                        constraint);
+          if (BE (err != REG_NOERROR, 0))
+            return err;
+
+          org_dest = dfa->edests[org_node].elems[1];
+          err = duplicate_node (&clone_dest, dfa, org_dest, constraint);
+          if (BE (err != REG_NOERROR, 0))
+            return err;
+          ret = re_node_set_insert (dfa->edests + clone_node, clone_dest);
+          if (BE (ret < 0, 0))
+            return REG_ESPACE;
+        }
+      org_node = org_dest;
+      clone_node = clone_dest;
+    }
+  return REG_NOERROR;
+}
+
 /* Duplicate the node whose index is ORG_IDX and set the constraint CONSTRAINT.
    The new index will be stored in NEW_IDX and return REG_NOERROR if succeeded,
    otherwise return the error code.  */
@@ -1204,50 +1276,18 @@ duplicate_node (new_idx, dfa, org_idx, constraint)
 {
   re_token_t dup;
   int dup_idx;
-  reg_errcode_t err;
-
-  dup.type = OP_CONTEXT_NODE;
-  if (dfa->nodes[org_idx].type == OP_CONTEXT_NODE)
-    {
-      /* If the node whose index is ORG_IDX is the same as the intended
-         node, use it.  */
-      if (dfa->nodes[org_idx].constraint == constraint)
-        {
-          *new_idx = org_idx;
-          return REG_NOERROR;
-        }
-      dup.constraint = constraint |
-        dfa->nodes[org_idx].constraint;
-    }
-  else
-    dup.constraint = constraint;
 
-  /* In case that `entity' points OP_CONTEXT_NODE,
-     we correct `entity' to real entity in calc_inveclosures(). */
-  dup.opr.ctx_info = malloc (sizeof (*dup.opr.ctx_info));
+  dup = dfa->nodes[org_idx];
   dup_idx = re_dfa_add_node (dfa, dup, 1);
-  if (BE (dup.opr.ctx_info == NULL || dup_idx == -1, 0))
+  if (BE (dup_idx == -1, 0))
     return REG_ESPACE;
-  dup.opr.ctx_info->entity = org_idx;
-  dup.opr.ctx_info->bkref_eclosure = NULL;
-
+  dfa->nodes[dup_idx].constraint = constraint;
+  if (dfa->nodes[org_idx].type == ANCHOR)
+    dfa->nodes[dup_idx].constraint |= dfa->nodes[org_idx].opr.ctx_type;
   dfa->nodes[dup_idx].duplicated = 1;
-  dfa->firsts[dup_idx] = dfa->firsts[org_idx];
-  dfa->nexts[dup_idx] = dfa->nexts[org_idx];
-  err = re_node_set_init_copy (dfa->edests + dup_idx, dfa->edests + org_idx);
-  if (BE (err != REG_NOERROR, 0))
-    return err;
-  /* Since we don't duplicate epsilon nodes, epsilon closure have
-     only itself.  */
-  err = re_node_set_init_1 (dfa->eclosures + dup_idx, dup_idx);
-  if (BE (err != REG_NOERROR, 0))
-    return err;
-  err = re_node_set_init_1 (dfa->inveclosures + dup_idx, dup_idx);
-  if (BE (err != REG_NOERROR, 0))
-    return err;
-  /* Then we must update inveclosure for this node.
-     We process them at last part of calc_eclosure(),
-     since we don't complete to calculate them here.  */
+  re_node_set_init_empty (dfa->edests + dup_idx);
+  re_node_set_init_empty (dfa->eclosures + dup_idx);
+  re_node_set_init_empty (dfa->inveclosures + dup_idx);
 
   *new_idx = dup_idx;
   return REG_NOERROR;
@@ -1257,7 +1297,7 @@ static void
 calc_inveclosure (dfa)
      re_dfa_t *dfa;
 {
-  int src, idx, dest, entity;
+  int src, idx, dest;
   for (src = 0; src < dfa->nodes_len; ++src)
     {
       for (idx = 0; idx < dfa->eclosures[src].nelem; ++idx)
@@ -1265,15 +1305,6 @@ calc_inveclosure (dfa)
           dest = dfa->eclosures[src].elems[idx];
           re_node_set_insert (dfa->inveclosures + dest, src);
         }
-
-      entity = src;
-      while (dfa->nodes[entity].type == OP_CONTEXT_NODE)
-        {
-          entity = dfa->nodes[entity].opr.ctx_info->entity;
-          re_node_set_merge (dfa->inveclosures + src,
-                             dfa->inveclosures + entity);
-          dfa->nodes[src].opr.ctx_info->entity = entity;
-        }
     }
 }
 
@@ -1283,16 +1314,17 @@ static reg_errcode_t
 calc_eclosure (dfa)
      re_dfa_t *dfa;
 {
-  int idx, node_idx, max, incomplete = 0;
+  int node_idx, incomplete;
 #ifdef DEBUG
   assert (dfa->nodes_len > 0);
 #endif
+  incomplete = 0;
   /* For each nodes, calculate epsilon closure.  */
-  for (node_idx = 0, max = dfa->nodes_len; ; ++node_idx)
+  for (node_idx = 0; ; ++node_idx)
     {
       reg_errcode_t err;
       re_node_set eclosure_elem;
-      if (node_idx == max)
+      if (node_idx == dfa->nodes_len)
         {
           if (!incomplete)
             break;
@@ -1301,7 +1333,6 @@ calc_eclosure (dfa)
         }
 
 #ifdef DEBUG
-      assert (dfa->nodes[node_idx].type != OP_CONTEXT_NODE);
       assert (dfa->eclosures[node_idx].nelem != -1);
 #endif
       /* If we have already calculated, skip it.  */
@@ -1318,41 +1349,6 @@ calc_eclosure (dfa)
           re_node_set_free (&eclosure_elem);
         }
     }
-
-  /* for duplicated nodes.  */
-  for (idx = max; idx < dfa->nodes_len; ++idx)
-    {
-      int entity, i, constraint;
-      re_node_set *bkref_eclosure;
-      entity = dfa->nodes[idx].opr.ctx_info->entity;
-      re_node_set_merge (dfa->inveclosures + idx, dfa->inveclosures + entity);
-      if (dfa->nodes[entity].type != OP_BACK_REF)
-        continue;
-
-      /* If the node is backreference, duplicate the epsilon closure of
-         the next node. Since it may epsilon transit.  */
-      /* Note: duplicate_node() may realloc dfa->eclosures, etc.  */
-      bkref_eclosure = re_malloc (re_node_set, 1);
-      if (BE (bkref_eclosure == NULL, 0))
-	return REG_ESPACE;
-      re_node_set_init_empty (bkref_eclosure);
-      constraint = dfa->nodes[idx].constraint;
-      for (i = 0; i < dfa->eclosures[dfa->nexts[idx]].nelem; ++i)
-        {
-          int dest_node_idx = dfa->eclosures[dfa->nexts[idx]].elems[i];
-          if (!IS_EPSILON_NODE (dfa->nodes[dest_node_idx].type))
-            {
-              reg_errcode_t err;
-              err = duplicate_node (&dest_node_idx, dfa, dest_node_idx,
-                                    constraint);
-              if (BE (err != REG_NOERROR, 0))
-                return err;
-            }
-          re_node_set_insert (bkref_eclosure, dest_node_idx);
-        }
-      dfa->nodes[idx].opr.ctx_info->bkref_eclosure = bkref_eclosure;
-    }
-
   return REG_NOERROR;
 }
 
@@ -1366,8 +1362,9 @@ calc_eclosure_iter (new_set, dfa, node, root)
 {
   reg_errcode_t err;
   unsigned int constraint;
-  int i, max, incomplete = 0;
+  int i, incomplete;
   re_node_set eclosure;
+  incomplete = 0;
   err = re_node_set_alloc (&eclosure, dfa->edests[node].nelem + 1);
   if (BE (err != REG_NOERROR, 0))
     return err;
@@ -1378,9 +1375,19 @@ calc_eclosure_iter (new_set, dfa, node, root)
 
   constraint = ((dfa->nodes[node].type == ANCHOR)
                 ? dfa->nodes[node].opr.ctx_type : 0);
+  /* If the current node has constraints, duplicate all nodes.
+     Since they must inherit the constraints.  */
+  if (constraint && !dfa->nodes[dfa->edests[node].elems[0]].duplicated)
+    {
+      int org_node, cur_node;
+      org_node = cur_node = node;
+      err = duplicate_node_closure (dfa, node, node, node, constraint);
+      if (BE (err != REG_NOERROR, 0))
+        return err;
+    }
 
   /* Expand each epsilon destination nodes.  */
-  if (dfa->edests[node].nelem != 0)
+  if (IS_EPSILON_NODE(dfa->nodes[node].type))
     for (i = 0; i < dfa->edests[node].nelem; ++i)
       {
         re_node_set eclosure_elem;
@@ -1413,28 +1420,6 @@ calc_eclosure_iter (new_set, dfa, node, root)
           }
       }
 
-  /* If the current node has constraints, duplicate all non-epsilon nodes.
-     Since they must inherit the constraints.  */
-  if (constraint)
-    for (i = 0, max = eclosure.nelem; i < max; ++i)
-      {
-        int dest = eclosure.elems[i];
-        if (!IS_EPSILON_NODE (dfa->nodes[dest].type))
-          {
-            int dup_dest;
-            reg_errcode_t err;
-            err = duplicate_node (&dup_dest, dfa, dest, constraint);
-            if (BE (err != REG_NOERROR, 0))
-              return err;
-            if (dest != dup_dest)
-              {
-                re_node_set_remove_at (&eclosure, i--);
-                re_node_set_insert (&eclosure, dup_dest);
-                --max;
-              }
-          }
-      }
-
   /* Epsilon closures include itself.  */
   re_node_set_insert (&eclosure, node);
   if (incomplete && !root)
@@ -1793,7 +1778,10 @@ parse (regexp, preg, syntax, err)
   else
     root = eor;
   if (BE (new_idx == -1 || eor == NULL || root == NULL, 0))
-    return *err = REG_ESPACE, NULL;
+    {
+      *err = REG_ESPACE;
+      return NULL;
+    }
   return root;
 }
 
@@ -1841,7 +1829,10 @@ parse_reg_exp (regexp, preg, token, syntax, nest, err)
 	branch = NULL;
       tree = create_tree (tree, branch, 0, new_idx);
       if (BE (new_idx == -1 || tree == NULL, 0))
-        return *err = REG_ESPACE, NULL;
+        {
+          *err = REG_ESPACE;
+          return NULL;
+        }
       dfa->has_plural_match = 1;
     }
   return tree;
@@ -1883,7 +1874,10 @@ parse_branch (regexp, preg, token, syntax, nest, err)
         {
           tree = create_tree (tree, exp, CONCAT, 0);
           if (tree == NULL)
-            return *err = REG_ESPACE, NULL;
+            {
+              *err = REG_ESPACE;
+              return NULL;
+            }
         }
       else if (tree == NULL)
         tree = exp;
@@ -1916,7 +1910,10 @@ parse_expression (regexp, preg, token, syntax, nest, err)
       new_idx = re_dfa_add_node (dfa, *token, 0);
       tree = create_tree (NULL, NULL, 0, new_idx);
       if (BE (new_idx == -1 || tree == NULL, 0))
-        return *err = REG_ESPACE, NULL;
+        {
+          *err = REG_ESPACE;
+          return NULL;
+        }
 #ifdef RE_ENABLE_I18N
       if (MB_CUR_MAX > 1)
 	{
@@ -1954,7 +1951,10 @@ parse_expression (regexp, preg, token, syntax, nest, err)
       new_idx = re_dfa_add_node (dfa, *token, 0);
       tree = create_tree (NULL, NULL, 0, new_idx);
       if (BE (new_idx == -1 || tree == NULL, 0))
-        return *err = REG_ESPACE, NULL;
+        {
+          *err = REG_ESPACE;
+          return NULL;
+        }
       ++dfa->nbackref;
       dfa->has_mb_node = 1;
       break;
@@ -1963,7 +1963,10 @@ parse_expression (regexp, preg, token, syntax, nest, err)
     case OP_DUP_QUESTION:
     case OP_OPEN_DUP_NUM:
       if (syntax & RE_CONTEXT_INVALID_OPS)
-        return *err = REG_BADRPT, NULL;
+        {
+          *err = REG_BADRPT;
+          return NULL;
+        }
       else if (syntax & RE_CONTEXT_INDEP_OPS)
         {
           *token = fetch_token (regexp, syntax);
@@ -1973,7 +1976,10 @@ parse_expression (regexp, preg, token, syntax, nest, err)
     case OP_CLOSE_SUBEXP:
       if ((token->type == OP_CLOSE_SUBEXP) &&
           !(syntax & RE_UNMATCHED_RIGHT_PAREN_ORD))
-        return *err = REG_ERPAREN, NULL;
+        {
+          *err = REG_ERPAREN;
+          return NULL;
+        }
       /* else fall through  */
     case OP_CLOSE_DUP_NUM:
       /* We treat it as a normal character.  */
@@ -1983,7 +1989,10 @@ parse_expression (regexp, preg, token, syntax, nest, err)
       new_idx = re_dfa_add_node (dfa, *token, 0);
       tree = create_tree (NULL, NULL, 0, new_idx);
       if (BE (new_idx == -1 || tree == NULL, 0))
-        return *err = REG_ESPACE, NULL;
+        {
+          *err = REG_ESPACE;
+          return NULL;
+        }
       break;
     case ANCHOR:
       if (dfa->word_char == NULL)
@@ -2008,7 +2017,10 @@ parse_expression (regexp, preg, token, syntax, nest, err)
           if (BE (idx_first == -1 || idx_last == -1 || new_idx == -1
                   || tree_first == NULL || tree_last == NULL
                   || tree == NULL, 0))
-            return *err = REG_ESPACE, NULL;
+            {
+              *err = REG_ESPACE;
+              return NULL;
+            }
         }
       else
         {
@@ -2027,7 +2039,10 @@ parse_expression (regexp, preg, token, syntax, nest, err)
       new_idx = re_dfa_add_node (dfa, *token, 0);
       tree = create_tree (NULL, NULL, 0, new_idx);
       if (BE (new_idx == -1 || tree == NULL, 0))
-        return *err = REG_ESPACE, NULL;
+        {
+          *err = REG_ESPACE;
+          return NULL;
+        }
       if (MB_CUR_MAX > 1)
         dfa->has_mb_node = 1;
       break;
@@ -2108,7 +2123,10 @@ parse_sub_exp (regexp, preg, token, syntax, nest, err)
   new_idx = re_dfa_add_node (dfa, *token, 0);
   left_par = create_tree (NULL, NULL, 0, new_idx);
   if (BE (new_idx == -1 || left_par == NULL, 0))
-    return *err = REG_ESPACE, NULL;
+    {
+      *err = REG_ESPACE;
+      return NULL;
+    }
   dfa->nodes[new_idx].opr.idx = cur_nsub;
   *token = fetch_token (regexp, syntax);
 
@@ -2134,7 +2152,10 @@ parse_sub_exp (regexp, preg, token, syntax, nest, err)
           : create_tree (tree, right_par, CONCAT, 0));
   tree = create_tree (left_par, tree, CONCAT, 0);
   if (BE (new_idx == -1 || right_par == NULL || tree == NULL, 0))
-    return *err = REG_ESPACE, NULL;
+    {
+      *err = REG_ESPACE;
+      return NULL;
+    }
   dfa->nodes[new_idx].opr.idx = cur_nsub;
 
   return tree;
@@ -2252,7 +2273,10 @@ parse_dup_op (dup_elem, regexp, dfa, token, syntax, err)
               work_tree = duplicate_tree (elem, dfa);
               tree = create_tree (tree, work_tree, CONCAT, 0);
               if (BE (work_tree == NULL || tree == NULL, 0))
-                return *err = REG_ESPACE, NULL;
+                {
+                  *err = REG_ESPACE;
+                  return NULL;
+                }
             }
         }
     }
@@ -2261,7 +2285,10 @@ parse_dup_op (dup_elem, regexp, dfa, token, syntax, err)
       new_idx = re_dfa_add_node (dfa, *token, 0);
       tree = create_tree (tree, NULL, 0, new_idx);
       if (BE (new_idx == -1 || tree == NULL, 0))
-        return *err = REG_ESPACE, NULL;
+        {
+          *err = REG_ESPACE;
+          return NULL;
+        }
     }
   *token = fetch_token (regexp, syntax);
   return tree;
diff --git a/posix/regex_internal.c b/posix/regex_internal.c
index 92f59b4..69fb9a6 100644
--- a/posix/regex_internal.c
+++ b/posix/regex_internal.c
@@ -929,20 +929,18 @@ re_dfa_add_node (dfa, token, mode)
         dfa->nodes = new_array;
       if (mode)
         {
-          int *new_firsts, *new_nexts;
+          int *new_nexts;
           re_node_set *new_edests, *new_eclosures, *new_inveclosures;
 
-          new_firsts = re_realloc (dfa->firsts, int, dfa->nodes_alloc);
           new_nexts = re_realloc (dfa->nexts, int, dfa->nodes_alloc);
           new_edests = re_realloc (dfa->edests, re_node_set, dfa->nodes_alloc);
           new_eclosures = re_realloc (dfa->eclosures, re_node_set,
                                       dfa->nodes_alloc);
           new_inveclosures = re_realloc (dfa->inveclosures, re_node_set,
                                          dfa->nodes_alloc);
-          if (BE (new_firsts == NULL || new_nexts == NULL || new_edests == NULL
+          if (BE (new_nexts == NULL || new_edests == NULL
                   || new_eclosures == NULL || new_inveclosures == NULL, 0))
             return -1;
-          dfa->firsts = new_firsts;
           dfa->nexts = new_nexts;
           dfa->edests = new_edests;
           dfa->eclosures = new_eclosures;
@@ -951,6 +949,7 @@ re_dfa_add_node (dfa, token, mode)
     }
   dfa->nodes[dfa->nodes_len] = token;
   dfa->nodes[dfa->nodes_len].duplicated = 0;
+  dfa->nodes[dfa->nodes_len].constraint = 0;
   return dfa->nodes_len++;
 }
 
@@ -1126,7 +1125,7 @@ create_ci_newstate (dfa, nodes, hash)
     {
       re_token_t *node = dfa->nodes + nodes->elems[i];
       re_token_type_t type = node->type;
-      if (type == CHARACTER)
+      if (type == CHARACTER && !node->constraint)
         continue;
 
       /* If the state has the halt node, the state is a halt state.  */
@@ -1139,13 +1138,8 @@ create_ci_newstate (dfa, nodes, hash)
 #endif /* RE_ENABLE_I18N */
       else if (type == OP_BACK_REF)
         newstate->has_backref = 1;
-      else if (type == ANCHOR || OP_CONTEXT_NODE)
-        {
-          newstate->has_constraint = 1;
-          if (type == OP_CONTEXT_NODE
-              && dfa->nodes[node->opr.ctx_info->entity].type == END_OF_RE)
-            newstate->halt = 1;
-        }
+      else if (type == ANCHOR || node->constraint)
+        newstate->has_constraint = 1;
     }
   err = register_state (dfa, newstate, hash);
   return (err != REG_NOERROR) ? NULL : newstate;
@@ -1175,9 +1169,11 @@ create_cd_newstate (dfa, nodes, context, hash)
       unsigned int constraint = 0;
       re_token_t *node = dfa->nodes + nodes->elems[i];
       re_token_type_t type = node->type;
-      if (type == CHARACTER)
-        continue;
+      if (node->constraint)
+        constraint = node->constraint;
 
+      if (type == CHARACTER && !constraint)
+        continue;
       /* If the state has the halt node, the state is a halt state.  */
       else if (type == END_OF_RE)
         newstate->halt = 1;
@@ -1190,20 +1186,6 @@ create_cd_newstate (dfa, nodes, context, hash)
         newstate->has_backref = 1;
       else if (type == ANCHOR)
         constraint = node->opr.ctx_type;
-      else if (type == OP_CONTEXT_NODE)
-        {
-          re_token_type_t ctype = dfa->nodes[node->opr.ctx_info->entity].type;
-          constraint = node->constraint;
-          if (ctype == END_OF_RE)
-            newstate->halt = 1;
-          else if (ctype == OP_BACK_REF)
-            newstate->has_backref = 1;
-#ifdef RE_ENABLE_I18N
-          else if (ctype == COMPLEX_BRACKET
-                   || (type == OP_PERIOD && MB_CUR_MAX > 1))
-            newstate->accept_mb = 1;
-#endif /* RE_ENABLE_I18N */
-        }
 
       if (constraint)
         {
diff --git a/posix/regex_internal.h b/posix/regex_internal.h
index 5aef684..7193ea0 100644
--- a/posix/regex_internal.h
+++ b/posix/regex_internal.h
@@ -133,7 +133,6 @@ typedef enum
   OP_DUP_QUESTION,
   OP_BACK_REF,
   ANCHOR,
-  OP_CONTEXT_NODE,
 
   /* Dummy marker.  */
   END_OF_RE_TOKEN_T
@@ -198,11 +197,6 @@ typedef struct
 #endif /* RE_ENABLE_I18N */
     int idx;			/* for BACK_REF */
     re_context_type ctx_type;	/* for ANCHOR */
-    struct
-    {
-      int entity;		/* for OP_CONTEXT_NODE, index of the entity */
-      re_node_set *bkref_eclosure;
-    } *ctx_info;
   } opr;
 #if __GNUC__ >= 2
   re_token_type_t type : 8;
@@ -474,7 +468,6 @@ struct re_dfa_t
   int nodes_alloc;
   int nodes_len;
   bin_tree_t *str_tree;
-  int *firsts;
   int *nexts;
   re_node_set *edests;
   re_node_set *eclosures;
@@ -519,6 +512,8 @@ static int re_node_set_compare (const re_node_set *set1,
                                 const re_node_set *set2);
 static int re_node_set_contains (const re_node_set *set, int elem);
 static void re_node_set_remove_at (re_node_set *set, int idx);
+#define re_node_set_remove(set,id) \
+  (re_node_set_remove_at (set, re_node_set_contains (set, id) - 1))
 #define re_node_set_empty(p) ((p)->nelem = 0)
 #define re_node_set_free(set) re_free ((set)->elems)
 static int re_dfa_add_node (re_dfa_t *dfa, re_token_t token, int mode);
diff --git a/posix/regexec.c b/posix/regexec.c
index 7e3a832..5c80f19 100644
--- a/posix/regexec.c
+++ b/posix/regexec.c
@@ -95,6 +95,8 @@ static reg_errcode_t set_regs (const regex_t *preg,
                                const re_match_context_t *mctx,
                                size_t nmatch, regmatch_t *pmatch,
                                int fl_backtrack);
+static reg_errcode_t free_fail_stack_return (struct re_fail_stack_t *fs);
+
 #ifdef RE_ENABLE_I18N
 static int sift_states_iter_mb (const regex_t *preg,
                                 const re_match_context_t *mctx,
@@ -845,11 +847,8 @@ check_matching (preg, mctx, fl_search, fl_longest_match)
       re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
       for (i = 0; i < cur_state->nodes.nelem; ++i)
         {
-          re_token_type_t type;
           int node = cur_state->nodes.elems[i];
-          int entity = (dfa->nodes[node].type != OP_CONTEXT_NODE ? node
-                        : dfa->nodes[node].opr.ctx_info->entity);
-          type = dfa->nodes[entity].type;
+          re_token_type_t type = dfa->nodes[node].type;
           if (type == OP_BACK_REF)
             {
               int clexp_idx;
@@ -859,7 +858,7 @@ check_matching (preg, mctx, fl_search, fl_longest_match)
                   re_token_t *clexp_node;
                   clexp_node = dfa->nodes + cur_state->nodes.elems[clexp_idx];
                   if (clexp_node->type == OP_CLOSE_SUBEXP
-                      && clexp_node->opr.idx + 1== dfa->nodes[entity].opr.idx)
+                      && clexp_node->opr.idx + 1== dfa->nodes[node].opr.idx)
                     {
                       err = match_ctx_add_entry (mctx, node, 0, 0, 0);
                       if (BE (err != REG_NOERROR, 0))
@@ -955,15 +954,13 @@ static int check_halt_node_context (dfa, node, context)
     int node;
     unsigned int context;
 {
-  int entity;
   re_token_type_t type = dfa->nodes[node].type;
-  if (type == END_OF_RE)
-    return 1;
-  if (type != OP_CONTEXT_NODE)
+  unsigned int constraint = dfa->nodes[node].constraint;
+  if (type != END_OF_RE)
     return 0;
-  entity = dfa->nodes[node].opr.ctx_info->entity;
-  if (dfa->nodes[entity].type != END_OF_RE
-      || NOT_SATISFY_NEXT_CONSTRAINT (dfa->nodes[node].constraint, context))
+  if (!constraint)
+    return 1;
+  if (NOT_SATISFY_NEXT_CONSTRAINT (constraint, context))
     return 0;
   return 1;
 }
@@ -1008,39 +1005,27 @@ proceed_next_node (preg, nregs, regs, mctx, pidx, node, eps_via_nodes, fs)
     struct re_fail_stack_t *fs;
 {
   re_dfa_t *dfa = (re_dfa_t *)preg->buffer;
-  int i, err, dest_node, cur_entity;
+  int i, err, dest_node;
   dest_node = -1;
-  cur_entity = ((dfa->nodes[node].type == OP_CONTEXT_NODE)
-                ? dfa->nodes[node].opr.ctx_info->entity : node);
   if (IS_EPSILON_NODE (dfa->nodes[node].type))
     {
-      int ndest, dest_nodes[2], dest_entities[2];
+      re_node_set *cur_nodes = &mctx->state_log[*pidx]->nodes;
+      int ndest, dest_nodes[2];
       err = re_node_set_insert (eps_via_nodes, node);
       if (BE (err < 0, 0))
         return -1;
       /* Pick up valid destinations.  */
-      for (ndest = 0, i = 0; i < mctx->state_log[*pidx]->nodes.nelem; ++i)
+      for (ndest = 0, i = 0; i < dfa->edests[node].nelem; ++i)
         {
-          int candidate = mctx->state_log[*pidx]->nodes.elems[i];
-          int entity;
-          entity = ((dfa->nodes[candidate].type == OP_CONTEXT_NODE)
-                    ? dfa->nodes[candidate].opr.ctx_info->entity : candidate);
-          if (!re_node_set_contains (dfa->edests + node, entity))
+          int candidate = dfa->edests[node].elems[i];
+          if (!re_node_set_contains (cur_nodes, candidate))
             continue;
           dest_nodes[0] = (ndest == 0) ? candidate : dest_nodes[0];
-          dest_entities[0] = (ndest == 0) ? entity : dest_entities[0];
           dest_nodes[1] = (ndest == 1) ? candidate : dest_nodes[1];
-          dest_entities[1] = (ndest == 1) ? entity : dest_entities[1];
           ++ndest;
         }
       if (ndest <= 1)
         return ndest == 0 ? -1 : (ndest == 1 ? dest_nodes[0] : 0);
-      if (dest_entities[0] > dest_entities[1])
-        {
-          int swap_work = dest_nodes[0];
-          dest_nodes[0] = dest_nodes[1];
-          dest_nodes[1] = swap_work;
-        }
       /* In order to avoid infinite loop like "(a*)*".  */
       if (re_node_set_contains (eps_via_nodes, dest_nodes[0]))
         return dest_nodes[1];
@@ -1050,22 +1035,17 @@ proceed_next_node (preg, nregs, regs, mctx, pidx, node, eps_via_nodes, fs)
     }
   else
     {
-      int naccepted = 0, entity = node;
+      int naccepted = 0;
       re_token_type_t type = dfa->nodes[node].type;
-      if (type == OP_CONTEXT_NODE)
-        {
-          entity = dfa->nodes[node].opr.ctx_info->entity;
-          type = dfa->nodes[entity].type;
-        }
 
 #ifdef RE_ENABLE_I18N
       if (ACCEPT_MB_NODE (type))
-        naccepted = check_node_accept_bytes (preg, entity, mctx->input, *pidx);
+        naccepted = check_node_accept_bytes (preg, node, mctx->input, *pidx);
       else
 #endif /* RE_ENABLE_I18N */
       if (type == OP_BACK_REF)
         {
-          int subexp_idx = dfa->nodes[entity].opr.idx;
+          int subexp_idx = dfa->nodes[node].opr.idx;
           naccepted = regs[subexp_idx].rm_eo - regs[subexp_idx].rm_so;
           if (fs != NULL)
             {
@@ -1085,18 +1065,10 @@ proceed_next_node (preg, nregs, regs, mctx, pidx, node, eps_via_nodes, fs)
               err = re_node_set_insert (eps_via_nodes, node);
               if (BE (err < 0, 0))
                 return -2;
-              dest_node = dfa->nexts[node];
+              dest_node = dfa->edests[node].elems[0];
               if (re_node_set_contains (&mctx->state_log[*pidx]->nodes,
                                         dest_node))
                 return dest_node;
-              for (i = 0; i < mctx->state_log[*pidx]->nodes.nelem; ++i)
-                {
-                  dest_node = mctx->state_log[*pidx]->nodes.elems[i];
-                  if ((dfa->nodes[dest_node].type == OP_CONTEXT_NODE
-                       && (dfa->nexts[node]
-                           == dfa->nodes[dest_node].opr.ctx_info->entity)))
-                    return dest_node;
-                }
             }
         }
 
@@ -1153,6 +1125,7 @@ pop_fail_stack (fs, pidx, nregs, regs, eps_via_nodes)
  *pidx = fs->stack[num].idx;
   memcpy (regs, fs->stack[num].regs, sizeof (regmatch_t) * nregs);
   re_node_set_free (eps_via_nodes);
+  re_free (fs->stack[num].regs);
   *eps_via_nodes = fs->stack[num].eps_via_nodes;
   return fs->stack[num].node;
 }
@@ -1201,12 +1174,18 @@ set_regs (preg, mctx, nmatch, pmatch, fl_backtrack)
                 if (pmatch[reg_idx].rm_so > -1 && pmatch[reg_idx].rm_eo == -1)
                   break;
               if (reg_idx == nmatch)
-                return REG_NOERROR;
+                {
+                  re_node_set_free (&eps_via_nodes);
+                  return free_fail_stack_return (fs);
+                }
               cur_node = pop_fail_stack (fs, &idx, nmatch, pmatch,
                                          &eps_via_nodes);
             }
           else
-            return REG_NOERROR;
+            {
+              re_node_set_free (&eps_via_nodes);
+              return REG_NOERROR;
+            }
         }
 
       /* Proceed to next node.  */
@@ -1221,10 +1200,30 @@ set_regs (preg, mctx, nmatch, pmatch, fl_backtrack)
             cur_node = pop_fail_stack (fs, &idx, nmatch, pmatch,
                                        &eps_via_nodes);
           else
-            return REG_NOMATCH;
+            {
+              re_node_set_free (&eps_via_nodes);
+              return REG_NOMATCH;
+            }
         }
     }
   re_node_set_free (&eps_via_nodes);
+  return free_fail_stack_return (fs);
+}
+
+static reg_errcode_t
+free_fail_stack_return (fs)
+     struct re_fail_stack_t *fs;
+{
+  if (fs)
+    {
+      int fs_idx;
+      for (fs_idx = 0; fs_idx < fs->num; ++fs_idx)
+        {
+          re_node_set_free (&fs->stack[fs_idx].eps_via_nodes);
+          re_free (fs->stack[fs_idx].regs);
+        }
+      re_free (fs->stack);
+    }
   return REG_NOERROR;
 }
 
@@ -1314,6 +1313,7 @@ sift_states_backward (preg, mctx, sctx)
         {
           memset (sctx->sifted_states, '\0',
                   sizeof (re_dfastate_t *) * str_idx);
+          re_node_set_free (&cur_dest);
           return REG_NOERROR;
         }
       re_node_set_empty (&cur_dest);
@@ -1330,22 +1330,16 @@ sift_states_backward (preg, mctx, sctx)
       for (i = 0; i < cur_src->nelem; i++)
         {
           int prev_node = cur_src->elems[i];
-          int entity = prev_node;
           int naccepted = 0;
           re_token_type_t type = dfa->nodes[prev_node].type;
 
           if (IS_EPSILON_NODE(type))
             continue;
-          if (type == OP_CONTEXT_NODE)
-            {
-              entity = dfa->nodes[prev_node].opr.ctx_info->entity;
-              type = dfa->nodes[entity].type;
-            }
 #ifdef RE_ENABLE_I18N
           /* If the node may accept `multi byte'.  */
           if (ACCEPT_MB_NODE (type))
-            naccepted = sift_states_iter_mb (preg, mctx, sctx, entity, str_idx,
-                                             sctx->last_str_idx);
+            naccepted = sift_states_iter_mb (preg, mctx, sctx, prev_node,
+                                             str_idx, sctx->last_str_idx);
 
 #endif /* RE_ENABLE_I18N */
           /* We don't check backreferences here.
@@ -1459,12 +1453,15 @@ update_cur_sifted_state (preg, mctx, sctx, str_idx, dest_nodes)
 
   /* At first, add the nodes which can epsilon transit to a node in
      DEST_NODE.  */
-  err = add_epsilon_src_nodes (dfa, dest_nodes, candidates);
-  if (BE (err != REG_NOERROR, 0))
-    return err;
+  if (dest_nodes->nelem)
+    {
+      err = add_epsilon_src_nodes (dfa, dest_nodes, candidates);
+      if (BE (err != REG_NOERROR, 0))
+	return err;
+    }
 
   /* Then, check the limitations in the current sift_context.  */
-  if (sctx->limits.nelem)
+  if (dest_nodes->nelem && sctx->limits.nelem)
     {
       err = check_subexp_limits (dfa, dest_nodes, candidates, &sctx->limits,
                                  mctx->bkref_ents, str_idx);
@@ -1479,7 +1476,7 @@ update_cur_sifted_state (preg, mctx, sctx, str_idx, dest_nodes)
 
   /* If we are searching for the subexpression candidates.
      Note that we were from transit_state_bkref_loop() in this case.  */
-  if (sctx->check_subexp)
+  if (dest_nodes->nelem && sctx->check_subexp)
     {
       err = search_subexp (preg, mctx, sctx, str_idx, dest_nodes);
       if (BE (err != REG_NOERROR, 0))
@@ -1538,7 +1535,7 @@ sub_epsilon_src_nodes (dfa, node, dest_nodes, candidates)
         int cur_node = inv_eclosure->elems[ecl_idx];
         if (cur_node == node)
           continue;
-        if (dfa->edests[cur_node].nelem)
+        if (IS_EPSILON_NODE (dfa->nodes[cur_node].type))
           {
             int edst1 = dfa->edests[cur_node].elems[0];
             int edst2 = ((dfa->edests[cur_node].nelem > 1)
@@ -1580,12 +1577,10 @@ check_dst_limits (dfa, limits, mctx, dst_node, dst_idx, src_node, src_idx)
 
   for (lim_idx = 0; lim_idx < limits->nelem; ++lim_idx)
     {
-      int bkref, subexp_idx/*, node_idx, cls_node*/;
+      int subexp_idx;
       struct re_backref_cache_entry *ent;
       ent = mctx->bkref_ents + limits->elems[lim_idx];
-      bkref = (dfa->nodes[ent->node].type == OP_CONTEXT_NODE
-               ? dfa->nodes[ent->node].opr.ctx_info->entity : ent->node);
-      subexp_idx = dfa->nodes[bkref].opr.idx - 1;
+      subexp_idx = dfa->nodes[ent->node].opr.idx - 1;
 
       dst_pos = check_dst_limits_calc_pos (dfa, mctx, limits->elems[lim_idx],
                                            dfa->eclosures + dst_node,
@@ -1624,13 +1619,7 @@ check_dst_limits_calc_pos (dfa, mctx, limit, eclosures, subexp_idx, node,
       for (node_idx = 0; node_idx < eclosures->nelem; ++node_idx)
         {
           int node = eclosures->elems[node_idx];
-          int entity = node;
           re_token_type_t type= dfa->nodes[node].type;
-          if (type == OP_CONTEXT_NODE)
-            {
-              entity = dfa->nodes[node].opr.ctx_info->entity;
-              type = dfa->nodes[entity].type;
-            }
           if (type == OP_BACK_REF)
             {
               int bi;
@@ -1641,7 +1630,7 @@ check_dst_limits_calc_pos (dfa, mctx, limit, eclosures, subexp_idx, node,
                       && ent->str_idx == str_idx)
                     {
                       int cpos, dst;
-                      dst = dfa->nexts[node];
+                      dst = dfa->edests[node].elems[0];
                       cpos = check_dst_limits_calc_pos (dfa, mctx, limit,
                                                         dfa->eclosures + dst,
                                                         subexp_idx, dst,
@@ -1685,17 +1674,14 @@ check_subexp_limits (dfa, dest_nodes, candidates, limits, bkref_ents, str_idx)
 
   for (lim_idx = 0; lim_idx < limits->nelem; ++lim_idx)
     {
-      int bkref, subexp_idx;
+      int subexp_idx;
       struct re_backref_cache_entry *ent;
       ent = bkref_ents + limits->elems[lim_idx];
 
       if (str_idx <= ent->subexp_from || ent->str_idx < str_idx)
         continue; /* This is unrelated limitation.  */
 
-      bkref = (dfa->nodes[ent->node].type == OP_CONTEXT_NODE
-               ? dfa->nodes[ent->node].opr.ctx_info->entity : ent->node);
-      subexp_idx = dfa->nodes[bkref].opr.idx - 1;
-
+      subexp_idx = dfa->nodes[ent->node].opr.idx - 1;
       if (ent->subexp_to == str_idx)
         {
           int ops_node = -1;
@@ -1790,12 +1776,8 @@ search_subexp (preg, mctx, sctx, str_idx, dest_nodes)
   for (node_idx = 0; node_idx < dest_nodes->nelem; ++node_idx)
     {
       re_token_type_t type;
-      int entity;
       node = dest_nodes->elems[node_idx];
       type = dfa->nodes[node].type;
-      entity = (type != OP_CONTEXT_NODE ? node
-                : dfa->nodes[node].opr.ctx_info->entity);
-      type = (type != OP_CONTEXT_NODE ? type : dfa->nodes[entity].type);
 
       if (type == OP_CLOSE_SUBEXP
           && sctx->check_subexp == dfa->nodes[node].opr.idx + 1)
@@ -1933,14 +1915,10 @@ sift_states_bkref (preg, mctx, sctx, str_idx, dest_nodes)
 
   for (node_idx = 0; node_idx < candidates->nelem; ++node_idx)
     {
-      int entity;
       int cur_bkref_idx = re_string_cur_idx (mctx->input);
       re_token_type_t type;
       node = candidates->elems[node_idx];
       type = dfa->nodes[node].type;
-      entity = (type != OP_CONTEXT_NODE ? node
-                : dfa->nodes[node].opr.ctx_info->entity);
-      type = (type != OP_CONTEXT_NODE ? type : dfa->nodes[entity].type);
       if (node == sctx->cur_bkref && str_idx == cur_bkref_idx)
         continue;
       /* Avoid infinite loop for the REs like "()\1+".  */
@@ -1951,37 +1929,25 @@ sift_states_bkref (preg, mctx, sctx, str_idx, dest_nodes)
           int enabled_idx;
           for (enabled_idx = 0; enabled_idx < mctx->nbkref_ents; ++enabled_idx)
             {
-              int disabled_idx, subexp_len, to_idx;
+              int disabled_idx, subexp_len, to_idx, dst_node;
               struct re_backref_cache_entry *entry;
               entry = mctx->bkref_ents + enabled_idx;
               subexp_len = entry->subexp_to - entry->subexp_from;
               to_idx = str_idx + subexp_len;
+              dst_node = (subexp_len ? dfa->nexts[node]
+                          : dfa->edests[node].elems[0]);
 
               if (entry->node != node || entry->str_idx != str_idx
                   || to_idx > sctx->last_str_idx
                   || sctx->sifted_states[to_idx] == NULL)
                 continue;
-              if (!STATE_NODE_CONTAINS (sctx->sifted_states[to_idx],
-                                        dfa->nexts[node]))
-                {
-                  int dst_idx;
-                  re_node_set *dsts = &sctx->sifted_states[to_idx]->nodes;
-                  for (dst_idx = 0; dst_idx < dsts->nelem; ++dst_idx)
-                    {
-                      int dst_node = dsts->elems[dst_idx];
-                      if (dfa->nodes[dst_node].type == OP_CONTEXT_NODE
-                          && (dfa->nodes[dst_node].opr.ctx_info->entity
-                              == dfa->nexts[node]))
-                        break;
-                    }
-                  if (dst_idx == dsts->nelem)
-                    continue;
-                }
+              if (!STATE_NODE_CONTAINS (sctx->sifted_states[to_idx], dst_node))
+                continue;
 
               if (check_dst_limits (dfa, &sctx->limits, mctx, node,
                                     str_idx, dfa->nexts[node], to_idx))
                 continue;
-              if (sctx->check_subexp == dfa->nodes[entity].opr.idx)
+              if (sctx->check_subexp == dfa->nodes[node].opr.idx)
                 {
                   char *buf;
                   buf = (char *) re_string_get_buffer (mctx->input);
@@ -2038,9 +2004,10 @@ sift_states_bkref (preg, mctx, sctx, str_idx, dest_nodes)
                         return err;
                     }
                   local_sctx.sifted_states[str_idx] = cur_state;
-                  re_node_set_remove_at (&local_sctx.limits,
-                                         local_sctx.limits.nelem - 1);
-                  entry->flag = 1;
+                  re_node_set_remove (&local_sctx.limits, enabled_idx);
+		  /* We must not use the variable entry here, since
+		     mctx->bkref_ents might be realloced.  */
+		  mctx->bkref_ents[enabled_idx].flag = 1;
                 }
             }
           for (enabled_idx = 0; enabled_idx < mctx->nbkref_ents; ++enabled_idx)
@@ -2301,15 +2268,14 @@ transit_state_mb (preg, pstate, mctx)
       unsigned int context;
       re_dfastate_t *dest_state;
 
-      if (dfa->nodes[cur_node_idx].type == OP_CONTEXT_NODE)
+      if (dfa->nodes[cur_node_idx].constraint)
         {
           context = re_string_context_at (mctx->input,
                                           re_string_cur_idx (mctx->input),
                                           mctx->eflags, preg->newline_anchor);
           if (NOT_SATISFY_NEXT_CONSTRAINT (dfa->nodes[cur_node_idx].constraint,
-                                        context))
+                                           context))
             continue;
-          cur_node_idx = dfa->nodes[cur_node_idx].opr.ctx_info->entity;
         }
 
       /* How many bytes the node can accepts?  */
@@ -2404,17 +2370,16 @@ transit_state_bkref_loop (preg, nodes, work_state_log, mctx)
       /* Check whether `node' is a backreference or not.  */
       if (node->type == OP_BACK_REF)
         subexp_idx = node->opr.idx;
-      else if (node->type == OP_CONTEXT_NODE &&
-               dfa->nodes[node->opr.ctx_info->entity].type == OP_BACK_REF)
+      else
+        continue;
+
+      if (node->constraint)
         {
           context = re_string_context_at (mctx->input, cur_str_idx,
                                           mctx->eflags, preg->newline_anchor);
           if (NOT_SATISFY_NEXT_CONSTRAINT (node->constraint, context))
             continue;
-          subexp_idx = dfa->nodes[node->opr.ctx_info->entity].opr.idx;
         }
-      else
-        continue;
 
       /* `node' is a backreference.
          Check the substring which the substring matched.  */
@@ -2440,8 +2405,8 @@ transit_state_bkref_loop (preg, nodes, work_state_log, mctx)
           if (bkref_ent->node != node_idx || bkref_ent->str_idx != cur_str_idx)
             continue;
           subexp_len = bkref_ent->subexp_to - bkref_ent->subexp_from;
-          new_dest_nodes = ((node->type == OP_CONTEXT_NODE && subexp_len == 0)
-                            ? dfa->nodes[node_idx].opr.ctx_info->bkref_eclosure
+          new_dest_nodes = (subexp_len == 0
+                            ? dfa->eclosures + dfa->edests[node_idx].elems[0]
                             : dfa->eclosures + dfa->nexts[node_idx]);
           dest_str_idx = (cur_str_idx + bkref_ent->subexp_to
                           - bkref_ent->subexp_from);
@@ -2688,16 +2653,9 @@ group_nodes_into_DFAstates (preg, state, dests_node, dests_ch)
   /* For all the nodes belonging to `state',  */
   for (i = 0; i < cur_nodes->nelem; ++i)
     {
-      unsigned int constraint = 0;
       re_token_t *node = &dfa->nodes[cur_nodes->elems[i]];
       re_token_type_t type = node->type;
-
-      if (type == OP_CONTEXT_NODE)
-        {
-          constraint = node->constraint;
-          node = dfa->nodes + node->opr.ctx_info->entity;
-          type = node->type;
-        }
+      unsigned int constraint = node->constraint;
 
       /* Enumerate all single byte character this node can accept.  */
       if (type == CHARACTER)
@@ -2724,10 +2682,10 @@ group_nodes_into_DFAstates (preg, state, dests_node, dests_ch)
           if (constraint & NEXT_WORD_CONSTRAINT)
             for (j = 0; j < BITSET_UINTS; ++j)
               accepts[j] &= dfa->word_char[j];
-          else if (constraint & NEXT_NOTWORD_CONSTRAINT)
+          if (constraint & NEXT_NOTWORD_CONSTRAINT)
             for (j = 0; j < BITSET_UINTS; ++j)
               accepts[j] &= ~dfa->word_char[j];
-          else if (constraint & NEXT_NEWLINE_CONSTRAINT)
+          if (constraint & NEXT_NEWLINE_CONSTRAINT)
             {
               int accepts_newline = bitset_contain (accepts, NEWLINE_CHAR);
               bitset_empty (accepts);
@@ -3058,10 +3016,8 @@ check_node_accept (preg, node, mctx, idx)
     const re_match_context_t *mctx;
     int idx;
 {
-  const re_dfa_t *dfa = (re_dfa_t *) preg->buffer;
-  const re_token_t *cur_node;
   unsigned char ch;
-  if (node->type == OP_CONTEXT_NODE)
+  if (node->constraint)
     {
       /* The node has constraints.  Check whether the current context
          satisfies the constraints.  */
@@ -3070,17 +3026,13 @@ check_node_accept (preg, node, mctx, idx)
                                                    preg->newline_anchor);
       if (NOT_SATISFY_NEXT_CONSTRAINT (node->constraint, context))
         return 0;
-      cur_node = dfa->nodes + node->opr.ctx_info->entity;
     }
-  else
-    cur_node = node;
-
   ch = re_string_byte_at (mctx->input, idx);
-  if (cur_node->type == CHARACTER)
-    return cur_node->opr.c == ch;
-  else if (cur_node->type == SIMPLE_BRACKET)
-    return bitset_contain (cur_node->opr.sbcset, ch);
-  else if (cur_node->type == OP_PERIOD)
+  if (node->type == CHARACTER)
+    return node->opr.c == ch;
+  else if (node->type == SIMPLE_BRACKET)
+    return bitset_contain (node->opr.sbcset, ch);
+  else if (node->type == OP_PERIOD)
     return !((ch == '\n' && !(preg->syntax & RE_DOT_NEWLINE))
              || (ch == '\0' && (preg->syntax & RE_DOT_NOT_NULL)));
   else
@@ -3221,5 +3173,7 @@ sift_ctx_init (sctx, sifted_sts, limited_sts, last_node, last_str_idx,
   sctx->last_node = last_node;
   sctx->last_str_idx = last_str_idx;
   sctx->check_subexp = check_subexp;
+  sctx->cur_bkref = -1;
+  sctx->cls_subexp_idx = -1;
   re_node_set_init_empty (&sctx->limits);
 }