[gcc/devel/omp/gcc-11] Fix fallout from merge from releases/gcc-11

[gcc/devel/omp/gcc-11] Fix fallout from merge from releases/gcc-11

[Tobias Burnus]

https://gcc.gnu.org/g:36d5a174f82ac554014da4352f3f08ddfb3e561c

commit 36d5a174f82ac554014da4352f3f08ddfb3e561c
Author: Tobias Burnus <tobias@codesourcery.com>
Date:   Fri May 14 09:44:19 2021 +0200

    Fix fallout from merge from releases/gcc-11
    
    Re-apply commit f963d6c79b1d52ce565c772166c3c3e1b1d0aa78 on nvptx.c:
    "Remove duplicate SESE code in NVPTX backend"
    The code got readded by a wrongly resolved merge conflict.
    
    Apply to the OG11 code the change of the merge-conflict causing change:
    commit da9c085ddbfe61e5954c8ec4e996240fa3a994c0
    "nvptx: Fix up nvptx build against latest libstdc++ [PR100375]"
    
    gcc/ChangeLog
    
            * omp-sese.c (omp_sese_pseudo): Use nullptr instead of 0
            as first argument of pseudo_node_t constructors.
            * config/nvptx/nvptx.c (bb_pair_t, bb_pair_vec_t,
            pseudo_node_t, bracket, bracket_vec_t,
            bb_sese, bb_sese::~bb_sese, bb_sese::append, bb_sese::remove,
            BB_SET_SESE, BB_GET_SESE, nvptx_sese_number, nvptx_sese_pseudo,
            nvptx_sese_color, nvptx_find_sese): Remove again.

Diff:
---
 gcc/config/nvptx/nvptx.c | 619 -----------------------------------------------
 gcc/omp-sese.c           |  10 +-
 2 files changed, 5 insertions(+), 624 deletions(-)

diff --git a/gcc/config/nvptx/nvptx.c b/gcc/config/nvptx/nvptx.c
index b8fecfcacca..1bf37f2ed82 100644
--- a/gcc/config/nvptx/nvptx.c
+++ b/gcc/config/nvptx/nvptx.c
@@ -3492,625 +3492,6 @@ nvptx_discover_pars (bb_insn_map_t *map)
   return par;
 }
 
-/* Analyse a group of BBs within a partitioned region and create N
-   Single-Entry-Single-Exit regions.  Some of those regions will be
-   trivial ones consisting of a single BB.  The blocks of a
-   partitioned region might form a set of disjoint graphs -- because
-   the region encloses a differently partitoned sub region.
-
-   We use the linear time algorithm described in 'Finding Regions Fast:
-   Single Entry Single Exit and control Regions in Linear Time'
-   Johnson, Pearson & Pingali.  That algorithm deals with complete
-   CFGs, where a back edge is inserted from END to START, and thus the
-   problem becomes one of finding equivalent loops.
-
-   In this case we have a partial CFG.  We complete it by redirecting
-   any incoming edge to the graph to be from an arbitrary external BB,
-   and similarly redirecting any outgoing edge to be to  that BB.
-   Thus we end up with a closed graph.
-
-   The algorithm works by building a spanning tree of an undirected
-   graph and keeping track of back edges from nodes further from the
-   root in the tree to nodes nearer to the root in the tree.  In the
-   description below, the root is up and the tree grows downwards.
-
-   We avoid having to deal with degenerate back-edges to the same
-   block, by splitting each BB into 3 -- one for input edges, one for
-   the node itself and one for the output edges.  Such back edges are
-   referred to as 'Brackets'.  Cycle equivalent nodes will have the
-   same set of brackets.
-   
-   Determining bracket equivalency is done by maintaining a list of
-   brackets in such a manner that the list length and final bracket
-   uniquely identify the set.
-
-   We use coloring to mark all BBs with cycle equivalency with the
-   same color.  This is the output of the 'Finding Regions Fast'
-   algorithm.  Notice it doesn't actually find the set of nodes within
-   a particular region, just unorderd sets of nodes that are the
-   entries and exits of SESE regions.
-   
-   After determining cycle equivalency, we need to find the minimal
-   set of SESE regions.  Do this with a DFS coloring walk of the
-   complete graph.  We're either 'looking' or 'coloring'.  When
-   looking, and we're in the subgraph, we start coloring the color of
-   the current node, and remember that node as the start of the
-   current color's SESE region.  Every time we go to a new node, we
-   decrement the count of nodes with thet color.  If it reaches zero,
-   we remember that node as the end of the current color's SESE region
-   and return to 'looking'.  Otherwise we color the node the current
-   color.
-
-   This way we end up with coloring the inside of non-trivial SESE
-   regions with the color of that region.  */
-
-/* A pair of BBs.  We use this to represent SESE regions.  */
-typedef std::pair<basic_block, basic_block> bb_pair_t;
-typedef auto_vec<bb_pair_t> bb_pair_vec_t;
-
-/* A node in the undirected CFG.  The discriminator SECOND indicates just
-   above or just below the BB idicated by FIRST.  */
-typedef std::pair<basic_block, int> pseudo_node_t;
-
-/* A bracket indicates an edge towards the root of the spanning tree of the
-   undirected graph.  Each bracket has a color, determined
-   from the currrent set of brackets.  */
-struct bracket
-{
-  pseudo_node_t back; /* Back target */
-
-  /* Current color and size of set.  */
-  unsigned color;
-  unsigned size;
-
-  bracket (pseudo_node_t back_)
-  : back (back_), color (~0u), size (~0u)
-  {
-  }
-
-  unsigned get_color (auto_vec<unsigned> &color_counts, unsigned length)
-  {
-    if (length != size)
-      {
-	size = length;
-	color = color_counts.length ();
-	color_counts.quick_push (0);
-      }
-    color_counts[color]++;
-    return color;
-  }
-};
-
-typedef auto_vec<bracket> bracket_vec_t;
-
-/* Basic block info for finding SESE regions.    */
-
-struct bb_sese
-{
-  int node;  /* Node number in spanning tree.  */
-  int parent; /* Parent node number.  */
-
-  /* The algorithm splits each node A into Ai, A', Ao. The incoming
-     edges arrive at pseudo-node Ai and the outgoing edges leave at
-     pseudo-node Ao.  We have to remember which way we arrived at a
-     particular node when generating the spanning tree.  dir > 0 means
-     we arrived at Ai, dir < 0 means we arrived at Ao.  */
-  int dir;
-
-  /* Lowest numbered pseudo-node reached via a backedge from thsis
-     node, or any descendant.  */
-  pseudo_node_t high;
-
-  int color;  /* Cycle-equivalence color  */
-
-  /* Stack of brackets for this node.  */
-  bracket_vec_t brackets;
-
-  bb_sese (unsigned node_, unsigned p, int dir_)
-  :node (node_), parent (p), dir (dir_)
-  {
-  }
-  ~bb_sese ();
-
-  /* Push a bracket ending at BACK.  */
-  void push (const pseudo_node_t &back)
-  {
-    if (dump_file)
-      fprintf (dump_file, "Pushing backedge %d:%+d\n",
-	       back.first ? back.first->index : 0, back.second);
-    brackets.safe_push (bracket (back));
-  }
-  
-  void append (bb_sese *child);
-  void remove (const pseudo_node_t &);
-
-  /* Set node's color.  */
-  void set_color (auto_vec<unsigned> &color_counts)
-  {
-    color = brackets.last ().get_color (color_counts, brackets.length ());
-  }
-};
-
-bb_sese::~bb_sese ()
-{
-}
-
-/* Destructively append CHILD's brackets.  */
-
-void
-bb_sese::append (bb_sese *child)
-{
-  if (int len = child->brackets.length ())
-    {
-      int ix;
-
-      if (dump_file)
-	{
-	  for (ix = 0; ix < len; ix++)
-	    {
-	      const pseudo_node_t &pseudo = child->brackets[ix].back;
-	      fprintf (dump_file, "Appending (%d)'s backedge %d:%+d\n",
-		       child->node, pseudo.first ? pseudo.first->index : 0,
-		       pseudo.second);
-	    }
-	}
-      if (!brackets.length ())
-	std::swap (brackets, child->brackets);
-      else
-	{
-	  brackets.reserve (len);
-	  for (ix = 0; ix < len; ix++)
-	    brackets.quick_push (child->brackets[ix]);
-	}
-    }
-}
-
-/* Remove brackets that terminate at PSEUDO.  */
-
-void
-bb_sese::remove (const pseudo_node_t &pseudo)
-{
-  unsigned removed = 0;
-  int len = brackets.length ();
-
-  for (int ix = 0; ix < len; ix++)
-    {
-      if (brackets[ix].back == pseudo)
-	{
-	  if (dump_file)
-	    fprintf (dump_file, "Removing backedge %d:%+d\n",
-		     pseudo.first ? pseudo.first->index : 0, pseudo.second);
-	  removed++;
-	}
-      else if (removed)
-	brackets[ix-removed] = brackets[ix];
-    }
-  while (removed--)
-    brackets.pop ();
-}
-
-/* Accessors for BB's aux pointer.  */
-#define BB_SET_SESE(B, S) ((B)->aux = (S))
-#define BB_GET_SESE(B) ((bb_sese *)(B)->aux)
-
-/* DFS walk creating SESE data structures.  Only cover nodes with
-   BB_VISITED set.  Append discovered blocks to LIST.  We number in
-   increments of 3 so that the above and below pseudo nodes can be
-   implicitly numbered too.  */
-
-static int
-nvptx_sese_number (int n, int p, int dir, basic_block b,
-		   auto_vec<basic_block> *list)
-{
-  if (BB_GET_SESE (b))
-    return n;
-
-  if (dump_file)
-    fprintf (dump_file, "Block %d(%d), parent (%d), orientation %+d\n",
-	     b->index, n, p, dir);
-  
-  BB_SET_SESE (b, new bb_sese (n, p, dir));
-  p = n;
-      
-  n += 3;
-  list->quick_push (b);
-
-  /* First walk the nodes on the 'other side' of this node, then walk
-     the nodes on the same side.  */
-  for (unsigned ix = 2; ix; ix--)
-    {
-      vec<edge, va_gc> *edges = dir > 0 ? b->succs : b->preds;
-      size_t offset = (dir > 0 ? offsetof (edge_def, dest)
-		       : offsetof (edge_def, src));
-      edge e;
-      edge_iterator ei;
-
-      FOR_EACH_EDGE (e, ei, edges)
-	{
-	  basic_block target = *(basic_block *)((char *)e + offset);
-	  
-	  if (target->flags & BB_VISITED)
-	    n = nvptx_sese_number (n, p, dir, target, list);
-	}
-      dir = -dir;
-    }
-  return n;
-}
-
-/* Process pseudo node above (DIR < 0) or below (DIR > 0) ME.
-   EDGES are the outgoing edges and OFFSET is the offset to the src
-   or dst block on the edges.   */
-
-static void
-nvptx_sese_pseudo (basic_block me, bb_sese *sese, int depth, int dir,
-		   vec<edge, va_gc> *edges, size_t offset)
-{
-  edge e;
-  edge_iterator ei;
-  int hi_back = depth;
-  pseudo_node_t node_back (nullptr, depth);
-  int hi_child = depth;
-  pseudo_node_t node_child (nullptr, depth);
-  basic_block child = NULL;
-  unsigned num_children = 0;
-  int usd = -dir * sese->dir;
-
-  if (dump_file)
-    fprintf (dump_file, "\nProcessing %d(%d) %+d\n",
-	     me->index, sese->node, dir);
-
-  if (dir < 0)
-    {
-      /* This is the above pseudo-child.  It has the BB itself as an
-	 additional child node.  */
-      node_child = sese->high;
-      hi_child = node_child.second;
-      if (node_child.first)
-	hi_child += BB_GET_SESE (node_child.first)->node;
-      num_children++;
-    }
-
-  /* Examine each edge.
-     - if it is a child (a) append its bracket list and (b) record
-          whether it is the child with the highest reaching bracket.
-     - if it is an edge to ancestor, record whether it's the highest
-          reaching backlink.  */
-  FOR_EACH_EDGE (e, ei, edges)
-    {
-      basic_block target = *(basic_block *)((char *)e + offset);
-
-      if (bb_sese *t_sese = BB_GET_SESE (target))
-	{
-	  if (t_sese->parent == sese->node && !(t_sese->dir + usd))
-	    {
-	      /* Child node.  Append its bracket list. */
-	      num_children++;
-	      sese->append (t_sese);
-
-	      /* Compare it's hi value.  */
-	      int t_hi = t_sese->high.second;
-
-	      if (basic_block child_hi_block = t_sese->high.first)
-		t_hi += BB_GET_SESE (child_hi_block)->node;
-
-	      if (hi_child > t_hi)
-		{
-		  hi_child = t_hi;
-		  node_child = t_sese->high;
-		  child = target;
-		}
-	    }
-	  else if (t_sese->node < sese->node + dir
-		   && !(dir < 0 && sese->parent == t_sese->node))
-	    {
-	      /* Non-parental ancestor node -- a backlink.  */
-	      int d = usd * t_sese->dir;
-	      int back = t_sese->node + d;
-	
-	      if (hi_back > back)
-		{
-		  hi_back = back;
-		  node_back = pseudo_node_t (target, d);
-		}
-	    }
-	}
-      else
-	{ /* Fallen off graph, backlink to entry node.  */
-	  hi_back = 0;
-	  node_back = pseudo_node_t (nullptr, 0);
-	}
-    }
-
-  /* Remove any brackets that terminate at this pseudo node.  */
-  sese->remove (pseudo_node_t (me, dir));
-
-  /* Now push any backlinks from this pseudo node.  */
-  FOR_EACH_EDGE (e, ei, edges)
-    {
-      basic_block target = *(basic_block *)((char *)e + offset);
-      if (bb_sese *t_sese = BB_GET_SESE (target))
-	{
-	  if (t_sese->node < sese->node + dir
-	      && !(dir < 0 && sese->parent == t_sese->node))
-	    /* Non-parental ancestor node - backedge from me.  */
-	    sese->push (pseudo_node_t (target, usd * t_sese->dir));
-	}
-      else
-	{
-	  /* back edge to entry node */
-	  sese->push (pseudo_node_t (nullptr, 0));
-	}
-    }
-  
- /* If this node leads directly or indirectly to a no-return region of
-     the graph, then fake a backedge to entry node.  */
-  if (!sese->brackets.length () || !edges || !edges->length ())
-    {
-      hi_back = 0;
-      node_back = pseudo_node_t (nullptr, 0);
-      sese->push (node_back);
-    }
-
-  /* Record the highest reaching backedge from us or a descendant.  */
-  sese->high = hi_back < hi_child ? node_back : node_child;
-
-  if (num_children > 1)
-    {
-      /* There is more than one child -- this is a Y shaped piece of
-	 spanning tree.  We have to insert a fake backedge from this
-	 node to the highest ancestor reached by not-the-highest
-	 reaching child.  Note that there may be multiple children
-	 with backedges to the same highest node.  That's ok and we
-	 insert the edge to that highest node.  */
-      hi_child = depth;
-      if (dir < 0 && child)
-	{
-	  node_child = sese->high;
-	  hi_child = node_child.second;
-	  if (node_child.first)
-	    hi_child += BB_GET_SESE (node_child.first)->node;
-	}
-
-      FOR_EACH_EDGE (e, ei, edges)
-	{
-	  basic_block target = *(basic_block *)((char *)e + offset);
-
-	  if (target == child)
-	    /* Ignore the highest child. */
-	    continue;
-
-	  bb_sese *t_sese = BB_GET_SESE (target);
-	  if (!t_sese)
-	    continue;
-	  if (t_sese->parent != sese->node)
-	    /* Not a child. */
-	    continue;
-
-	  /* Compare its hi value.  */
-	  int t_hi = t_sese->high.second;
-
-	  if (basic_block child_hi_block = t_sese->high.first)
-	    t_hi += BB_GET_SESE (child_hi_block)->node;
-
-	  if (hi_child > t_hi)
-	    {
-	      hi_child = t_hi;
-	      node_child = t_sese->high;
-	    }
-	}
-      
-      sese->push (node_child);
-    }
-}
-
-
-/* DFS walk of BB graph.  Color node BLOCK according to COLORING then
-   proceed to successors.  Set SESE entry and exit nodes of
-   REGIONS.  */
-
-static void
-nvptx_sese_color (auto_vec<unsigned> &color_counts, bb_pair_vec_t &regions,
-		  basic_block block, int coloring)
-{
-  bb_sese *sese = BB_GET_SESE (block);
-
-  if (block->flags & BB_VISITED)
-    {
-      /* If we've already encountered this block, either we must not
-	 be coloring, or it must have been colored the current color.  */
-      gcc_assert (coloring < 0 || (sese && coloring == sese->color));
-      return;
-    }
-  
-  block->flags |= BB_VISITED;
-
-  if (sese)
-    {
-      if (coloring < 0)
-	{
-	  /* Start coloring a region.  */
-	  regions[sese->color].first = block;
-	  coloring = sese->color;
-	}
-
-      if (!--color_counts[sese->color] && sese->color == coloring)
-	{
-	  /* Found final block of SESE region.  */
-	  regions[sese->color].second = block;
-	  coloring = -1;
-	}
-      else
-	/* Color the node, so we can assert on revisiting the node
-	   that the graph is indeed SESE.  */
-	sese->color = coloring;
-    }
-  else
-    /* Fallen off the subgraph, we cannot be coloring.  */
-    gcc_assert (coloring < 0);
-
-  /* Walk each successor block.  */
-  if (block->succs && block->succs->length ())
-    {
-      edge e;
-      edge_iterator ei;
-      
-      FOR_EACH_EDGE (e, ei, block->succs)
-	nvptx_sese_color (color_counts, regions, e->dest, coloring);
-    }
-  else
-    gcc_assert (coloring < 0);
-}
-
-/* Find minimal set of SESE regions covering BLOCKS.  REGIONS might
-   end up with NULL entries in it.  */
-
-static void
-nvptx_find_sese (auto_vec<basic_block> &blocks, bb_pair_vec_t &regions)
-{
-  basic_block block;
-  int ix;
-
-  /* First clear each BB of the whole function.  */ 
-  FOR_ALL_BB_FN (block, cfun)
-    {
-      block->flags &= ~BB_VISITED;
-      BB_SET_SESE (block, 0);
-    }
-
-  /* Mark blocks in the function that are in this graph.  */
-  for (ix = 0; blocks.iterate (ix, &block); ix++)
-    block->flags |= BB_VISITED;
-
-  /* Counts of nodes assigned to each color.  There cannot be more
-     colors than blocks (and hopefully there will be fewer).  */
-  auto_vec<unsigned> color_counts;
-  color_counts.reserve (blocks.length ());
-
-  /* Worklist of nodes in the spanning tree.  Again, there cannot be
-     more nodes in the tree than blocks (there will be fewer if the
-     CFG of blocks is disjoint).  */
-  auto_vec<basic_block> spanlist;
-  spanlist.reserve (blocks.length ());
-
-  /* Make sure every block has its cycle class determined.  */
-  for (ix = 0; blocks.iterate (ix, &block); ix++)
-    {
-      if (BB_GET_SESE (block))
-	/* We already met this block in an earlier graph solve.  */
-	continue;
-
-      if (dump_file)
-	fprintf (dump_file, "Searching graph starting at %d\n", block->index);
-      
-      /* Number the nodes reachable from block initial DFS order.  */
-      int depth = nvptx_sese_number (2, 0, +1, block, &spanlist);
-
-      /* Now walk in reverse DFS order to find cycle equivalents.  */
-      while (spanlist.length ())
-	{
-	  block = spanlist.pop ();
-	  bb_sese *sese = BB_GET_SESE (block);
-
-	  /* Do the pseudo node below.  */
-	  nvptx_sese_pseudo (block, sese, depth, +1,
-			     sese->dir > 0 ? block->succs : block->preds,
-			     (sese->dir > 0 ? offsetof (edge_def, dest)
-			      : offsetof (edge_def, src)));
-	  sese->set_color (color_counts);
-	  /* Do the pseudo node above.  */
-	  nvptx_sese_pseudo (block, sese, depth, -1,
-			     sese->dir < 0 ? block->succs : block->preds,
-			     (sese->dir < 0 ? offsetof (edge_def, dest)
-			      : offsetof (edge_def, src)));
-	}
-      if (dump_file)
-	fprintf (dump_file, "\n");
-    }
-
-  if (dump_file)
-    {
-      unsigned count;
-      const char *comma = "";
-      
-      fprintf (dump_file, "Found %d cycle equivalents\n",
-	       color_counts.length ());
-      for (ix = 0; color_counts.iterate (ix, &count); ix++)
-	{
-	  fprintf (dump_file, "%s%d[%d]={", comma, ix, count);
-
-	  comma = "";
-	  for (unsigned jx = 0; blocks.iterate (jx, &block); jx++)
-	    if (BB_GET_SESE (block)->color == ix)
-	      {
-		block->flags |= BB_VISITED;
-		fprintf (dump_file, "%s%d", comma, block->index);
-		comma=",";
-	      }
-	  fprintf (dump_file, "}");
-	  comma = ", ";
-	}
-      fprintf (dump_file, "\n");
-   }
-  
-  /* Now we've colored every block in the subgraph.  We now need to
-     determine the minimal set of SESE regions that cover that
-     subgraph.  Do this with a DFS walk of the complete function.
-     During the walk we're either 'looking' or 'coloring'.  When we
-     reach the last node of a particular color, we stop coloring and
-     return to looking.  */
-
-  /* There cannot be more SESE regions than colors.  */
-  regions.reserve (color_counts.length ());
-  for (ix = color_counts.length (); ix--;)
-    regions.quick_push (bb_pair_t (0, 0));
-
-  for (ix = 0; blocks.iterate (ix, &block); ix++)
-    block->flags &= ~BB_VISITED;
-
-  nvptx_sese_color (color_counts, regions, ENTRY_BLOCK_PTR_FOR_FN (cfun), -1);
-
-  if (dump_file)
-    {
-      const char *comma = "";
-      int len = regions.length ();
-      
-      fprintf (dump_file, "SESE regions:");
-      for (ix = 0; ix != len; ix++)
-	{
-	  basic_block from = regions[ix].first;
-	  basic_block to = regions[ix].second;
-
-	  if (from)
-	    {
-	      fprintf (dump_file, "%s %d{%d", comma, ix, from->index);
-	      if (to != from)
-		fprintf (dump_file, "->%d", to->index);
-
-	      int color = BB_GET_SESE (from)->color;
-
-	      /* Print the blocks within the region (excluding ends).  */
-	      FOR_EACH_BB_FN (block, cfun)
-		{
-		  bb_sese *sese = BB_GET_SESE (block);
-
-		  if (sese && sese->color == color
-		      && block != from && block != to)
-		    fprintf (dump_file, ".%d", block->index);
-		}
-	      fprintf (dump_file, "}");
-	    }
-	  comma = ",";
-	}
-      fprintf (dump_file, "\n\n");
-    }
-  
-  for (ix = 0; blocks.iterate (ix, &block); ix++)
-    delete BB_GET_SESE (block);
-}
-
-#undef BB_SET_SESE
-#undef BB_GET_SESE
-
 /* Propagate live state at the start of a partitioned region.  IS_CALL
    indicates whether the propagation is for a (partitioned) call
    instruction.  BLOCK provides the live register information, and
diff --git a/gcc/omp-sese.c b/gcc/omp-sese.c
index af63e70d9ec..1ca175a9ab6 100644
--- a/gcc/omp-sese.c
+++ b/gcc/omp-sese.c
@@ -2084,9 +2084,9 @@ omp_sese_pseudo (basic_block me, bb_sese *sese, int depth, int dir,
   edge e;
   edge_iterator ei;
   int hi_back = depth;
-  pseudo_node_t node_back (0, depth);
+  pseudo_node_t node_back (nullptr, depth);
   int hi_child = depth;
-  pseudo_node_t node_child (0, depth);
+  pseudo_node_t node_child (nullptr, depth);
   basic_block child = NULL;
   unsigned num_children = 0;
   int usd = -dir * sese->dir;
@@ -2153,7 +2153,7 @@ omp_sese_pseudo (basic_block me, bb_sese *sese, int depth, int dir,
       else
 	{ /* Fallen off graph, backlink to entry node.  */
 	  hi_back = 0;
-	  node_back = pseudo_node_t (0, 0);
+	  node_back = pseudo_node_t (nullptr, 0);
 	}
     }
 
@@ -2174,7 +2174,7 @@ omp_sese_pseudo (basic_block me, bb_sese *sese, int depth, int dir,
       else
 	{
 	  /* back edge to entry node */
-	  sese->push (pseudo_node_t (0, 0));
+	  sese->push (pseudo_node_t (nullptr, 0));
 	}
     }
 
@@ -2183,7 +2183,7 @@ omp_sese_pseudo (basic_block me, bb_sese *sese, int depth, int dir,
   if (!sese->brackets.length () || !edges || !edges->length ())
     {
       hi_back = 0;
-      node_back = pseudo_node_t (0, 0);
+      node_back = pseudo_node_t (nullptr, 0);
       sese->push (node_back);
     }