Imported gcc-4.4.3

[msp430-gcc.git] / gcc / cfgloop.c

diff --git a/gcc/cfgloop.c b/gcc/cfgloop.c
index 2bd0d4c44bf72a45902ed9167781164e534ad335..e74284e8988d42b695074eca5836de2758a89660 100644 (file)
--- a/gcc/cfgloop.c
+++ b/gcc/cfgloop.c
@@ -1,11 +1,12 @@
 /* Natural loop discovery code for GNU compiler.
 /* Natural loop discovery code for GNU compiler.

-   Copyright (C) 2000, 2001 Free Software Foundation, Inc.
+   Copyright (C) 2000, 2001, 2003, 2004, 2005, 2006, 2007, 2008
+   Free Software Foundation, Inc.

 
 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
 
 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 2, or (at your option) any later
+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
 version.
 
 GCC is distributed in the hope that it will be useful, but WITHOUT ANY


@@ -14,823 +15,1623 @@ 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
 for more details.
 
 You should have received a copy of the GNU General Public License

-along with GCC; see the file COPYING.  If not, write to the Free
-Software Foundation, 59 Temple Place - Suite 330, Boston, MA
-02111-1307, USA.  */
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */

 
 #include "config.h"
 #include "system.h"
 
 #include "config.h"
 #include "system.h"

+#include "coretypes.h"
+#include "tm.h"

 #include "rtl.h"
 #include "hard-reg-set.h"
 #include "rtl.h"
 #include "hard-reg-set.h"

+#include "obstack.h"
+#include "function.h"

 #include "basic-block.h"
 #include "basic-block.h"

-
-static void flow_loops_cfg_dump                PARAMS ((const struct loops *,
-                                                FILE *));
-static int flow_loop_nested_p          PARAMS ((struct loop *,
-                                                struct loop *));
-static int flow_loop_entry_edges_find  PARAMS ((basic_block, const sbitmap,
-                                                edge **));
-static int flow_loop_exit_edges_find   PARAMS ((const sbitmap, edge **));
-static int flow_loop_nodes_find                PARAMS ((basic_block, basic_block,
-                                                sbitmap));
-static void flow_loop_pre_header_scan  PARAMS ((struct loop *));
-static basic_block flow_loop_pre_header_find PARAMS ((basic_block,
-                                                     const sbitmap *));
-static void flow_loop_tree_node_add    PARAMS ((struct loop *,
-                                                struct loop *));
-static void flow_loops_tree_build      PARAMS ((struct loops *));
-static int flow_loop_level_compute     PARAMS ((struct loop *, int));
-static int flow_loops_level_compute    PARAMS ((struct loops *));
+#include "toplev.h"
+#include "cfgloop.h"
+#include "flags.h"
+#include "tree.h"
+#include "tree-flow.h"
+#include "pointer-set.h"
+#include "output.h"
+#include "ggc.h"
+
+static void flow_loops_cfg_dump (FILE *);

 \f
 /* Dump loop related CFG information.  */
 
 static void
 \f
 /* Dump loop related CFG information.  */
 
 static void

-flow_loops_cfg_dump (loops, file)
-     const struct loops *loops;
-     FILE *file;
+flow_loops_cfg_dump (FILE *file)

 {
 {

-  int i;
+  basic_block bb;

 
 

-  if (! loops->num || ! file || ! loops->cfg.dom)
+  if (!file)

     return;
 
     return;
 

-  for (i = 0; i < n_basic_blocks; i++)
+  FOR_EACH_BB (bb)

     {
       edge succ;
     {
       edge succ;

+      edge_iterator ei;

 
 

-      fprintf (file, ";; %d succs { ", i);
-      for (succ = BASIC_BLOCK (i)->succ; succ; succ = succ->succ_next)
+      fprintf (file, ";; %d succs { ", bb->index);
+      FOR_EACH_EDGE (succ, ei, bb->succs)

        fprintf (file, "%d ", succ->dest->index);
        fprintf (file, "%d ", succ->dest->index);

-      flow_nodes_print ("} dom", loops->cfg.dom[i], file);
+      fprintf (file, "}\n");

     }
     }

+}

 
 

-  /* Dump the DFS node order.  */
-  if (loops->cfg.dfs_order)
-    {
-      fputs (";; DFS order: ", file);
-      for (i = 0; i < n_basic_blocks; i++)
-       fprintf (file, "%d ", loops->cfg.dfs_order[i]);
+/* Return nonzero if the nodes of LOOP are a subset of OUTER.  */

 
 

-      fputs ("\n", file);
-    }
+bool
+flow_loop_nested_p (const struct loop *outer, const struct loop *loop)
+{
+  unsigned odepth = loop_depth (outer);

 
 

-  /* Dump the reverse completion node order.  */
-  if (loops->cfg.rc_order)
-    {
-      fputs (";; RC order: ", file);
-      for (i = 0; i < n_basic_blocks; i++)
-       fprintf (file, "%d ", loops->cfg.rc_order[i]);
+  return (loop_depth (loop) > odepth
+         && VEC_index (loop_p, loop->superloops, odepth) == outer);
+}

 
 

-      fputs ("\n", file);
-    }
+/* Returns the loop such that LOOP is nested DEPTH (indexed from zero)
+   loops within LOOP.  */
+
+struct loop *
+superloop_at_depth (struct loop *loop, unsigned depth)
+{
+  unsigned ldepth = loop_depth (loop);
+
+  gcc_assert (depth <= ldepth);
+
+  if (depth == ldepth)
+    return loop;
+
+  return VEC_index (loop_p, loop->superloops, depth);

 }
 
 }
 

-/* Return non-zero if the nodes of LOOP are a subset of OUTER.  */
+/* Returns the list of the latch edges of LOOP.  */

 
 

-static int
-flow_loop_nested_p (outer, loop)
-     struct loop *outer;
-     struct loop *loop;
+static VEC (edge, heap) *
+get_loop_latch_edges (const struct loop *loop)

 {
 {

-  return sbitmap_a_subset_b_p (loop->nodes, outer->nodes);
+  edge_iterator ei;
+  edge e;
+  VEC (edge, heap) *ret = NULL;
+
+  FOR_EACH_EDGE (e, ei, loop->header->preds)
+    {
+      if (dominated_by_p (CDI_DOMINATORS, e->src, loop->header))
+       VEC_safe_push (edge, heap, ret, e);
+    }
+
+  return ret;

 }
 
 /* Dump the loop information specified by LOOP to the stream FILE
    using auxiliary dump callback function LOOP_DUMP_AUX if non null.  */
 
 void
 }
 
 /* Dump the loop information specified by LOOP to the stream FILE
    using auxiliary dump callback function LOOP_DUMP_AUX if non null.  */
 
 void

-flow_loop_dump (loop, file, loop_dump_aux, verbose)
-     const struct loop *loop;
-     FILE *file;
-     void (*loop_dump_aux) PARAMS((const struct loop *, FILE *, int));
-     int verbose;
+flow_loop_dump (const struct loop *loop, FILE *file,
+               void (*loop_dump_aux) (const struct loop *, FILE *, int),
+               int verbose)

 {
 {

+  basic_block *bbs;
+  unsigned i;
+  VEC (edge, heap) *latches;
+  edge e;
+

   if (! loop || ! loop->header)
     return;
 
   if (! loop || ! loop->header)
     return;
 

-  if (loop->first->head && loop->last->end)
-    fprintf (file, ";;\n;; Loop %d (%d to %d):%s%s\n",
-           loop->num, INSN_UID (loop->first->head),
-           INSN_UID (loop->last->end),
-           loop->shared ? " shared" : "", loop->invalid ? " invalid" : "");
+  fprintf (file, ";;\n;; Loop %d\n", loop->num);
+
+  fprintf (file, ";;  header %d, ", loop->header->index);
+  if (loop->latch)
+    fprintf (file, "latch %d\n", loop->latch->index);

   else
   else

-    fprintf (file, ";;\n;; Loop %d:%s%s\n", loop->num,
-            loop->shared ? " shared" : "", loop->invalid ? " invalid" : "");
-
-  fprintf (file, ";;  header %d, latch %d, pre-header %d, first %d, last %d\n",
-          loop->header->index, loop->latch->index,
-          loop->pre_header ? loop->pre_header->index : -1,
-          loop->first->index, loop->last->index);
-  fprintf (file, ";;  depth %d, level %d, outer %ld\n",
-          loop->depth, loop->level,
-          (long) (loop->outer ? loop->outer->num : -1));
-
-  if (loop->pre_header_edges)
-    flow_edge_list_print (";;  pre-header edges", loop->pre_header_edges,
-                         loop->num_pre_header_edges, file);
-
-  flow_edge_list_print (";;  entry edges", loop->entry_edges,
-                       loop->num_entries, file);
-  fprintf (file, ";;  %d", loop->num_nodes);
-  flow_nodes_print (" nodes", loop->nodes, file);
-  flow_edge_list_print (";;  exit edges", loop->exit_edges,
-                       loop->num_exits, file);
-
-  if (loop->exits_doms)
-    flow_nodes_print (";;  exit doms", loop->exits_doms, file);
+    {
+      fprintf (file, "multiple latches:");
+      latches = get_loop_latch_edges (loop);
+      for (i = 0; VEC_iterate (edge, latches, i, e); i++)
+       fprintf (file, " %d", e->src->index);
+      VEC_free (edge, heap, latches);
+      fprintf (file, "\n");
+    }
+
+  fprintf (file, ";;  depth %d, outer %ld\n",
+          loop_depth (loop), (long) (loop_outer (loop)
+                                     ? loop_outer (loop)->num : -1));
+
+  fprintf (file, ";;  nodes:");
+  bbs = get_loop_body (loop);
+  for (i = 0; i < loop->num_nodes; i++)
+    fprintf (file, " %d", bbs[i]->index);
+  free (bbs);
+  fprintf (file, "\n");

 
   if (loop_dump_aux)
     loop_dump_aux (loop, file, verbose);
 }
 
 
   if (loop_dump_aux)
     loop_dump_aux (loop, file, verbose);
 }
 

-/* Dump the loop information specified by LOOPS to the stream FILE,
+/* Dump the loop information about loops to the stream FILE,

    using auxiliary dump callback function LOOP_DUMP_AUX if non null.  */
 
 void
    using auxiliary dump callback function LOOP_DUMP_AUX if non null.  */
 
 void

-flow_loops_dump (loops, file, loop_dump_aux, verbose)
-     const struct loops *loops;
-     FILE *file;
-     void (*loop_dump_aux) PARAMS((const struct loop *, FILE *, int));
-     int verbose;
+flow_loops_dump (FILE *file, void (*loop_dump_aux) (const struct loop *, FILE *, int), int verbose)

 {
 {

-  int i, j;
-  int num_loops;
+  loop_iterator li;
+  struct loop *loop;

 
 

-  num_loops = loops->num;
-  if (! num_loops || ! file)
+  if (!current_loops || ! file)

     return;
 
     return;
 

-  fprintf (file, ";; %d loops found, %d levels\n", num_loops, loops->levels);
-  for (i = 0; i < num_loops; i++)
-    {
-      struct loop *loop = &loops->array[i];
+  fprintf (file, ";; %d loops found\n", number_of_loops ());

 
 

+  FOR_EACH_LOOP (li, loop, LI_INCLUDE_ROOT)
+    {

       flow_loop_dump (loop, file, loop_dump_aux, verbose);
       flow_loop_dump (loop, file, loop_dump_aux, verbose);

-      if (loop->shared)
-       for (j = 0; j < i; j++)
-         {
-           struct loop *oloop = &loops->array[j];
-
-           if (loop->header == oloop->header)
-             {
-               int disjoint;
-               int smaller;
-
-               smaller = loop->num_nodes < oloop->num_nodes;
-
-               /* If the union of LOOP and OLOOP is different than
-                  the larger of LOOP and OLOOP then LOOP and OLOOP
-                  must be disjoint.  */
-               disjoint = ! flow_loop_nested_p (smaller ? loop : oloop,
-                                                smaller ? oloop : loop);
-               fprintf (file,
-                        ";; loop header %d shared by loops %d, %d %s\n",
-                        loop->header->index, i, j,
-                        disjoint ? "disjoint" : "nested");
-             }
-         }

     }
 
   if (verbose)
     }
 
   if (verbose)

-    flow_loops_cfg_dump (loops, file);
+    flow_loops_cfg_dump (file);

 }
 
 }
 

-/* Free all the memory allocated for LOOPS.  */
+/* Free data allocated for LOOP.  */

 
 void
 
 void

-flow_loops_free (loops)
-     struct loops *loops;
+flow_loop_free (struct loop *loop)

 {
 {

-  if (loops->array)
+  struct loop_exit *exit, *next;
+
+  VEC_free (loop_p, gc, loop->superloops);
+
+  /* Break the list of the loop exit records.  They will be freed when the
+     corresponding edge is rescanned or removed, and this avoids
+     accessing the (already released) head of the list stored in the
+     loop structure.  */
+  for (exit = loop->exits->next; exit != loop->exits; exit = next)

     {
     {

-      int i;
+      next = exit->next;
+      exit->next = exit;
+      exit->prev = exit;
+    }
+
+  ggc_free (loop->exits);
+  ggc_free (loop);
+}

 
 

-      if (! loops->num)
-       abort ();
+/* Free all the memory allocated for LOOPS.  */
+
+void
+flow_loops_free (struct loops *loops)
+{
+  if (loops->larray)
+    {
+      unsigned i;
+      loop_p loop;

 
       /* Free the loop descriptors.  */
 
       /* Free the loop descriptors.  */

-      for (i = 0; i < loops->num; i++)
+      for (i = 0; VEC_iterate (loop_p, loops->larray, i, loop); i++)

        {
        {

-         struct loop *loop = &loops->array[i];
-
-         if (loop->pre_header_edges)
-           free (loop->pre_header_edges);
-         if (loop->nodes)
-           sbitmap_free (loop->nodes);
-         if (loop->entry_edges)
-           free (loop->entry_edges);
-         if (loop->exit_edges)
-           free (loop->exit_edges);
-         if (loop->exits_doms)
-           sbitmap_free (loop->exits_doms);
+         if (!loop)
+           continue;
+
+         flow_loop_free (loop);
+       }
+
+      VEC_free (loop_p, gc, loops->larray);
+    }
+}
+
+/* Find the nodes contained within the LOOP with header HEADER.
+   Return the number of nodes within the loop.  */
+
+int
+flow_loop_nodes_find (basic_block header, struct loop *loop)
+{
+  VEC (basic_block, heap) *stack = NULL;
+  int num_nodes = 1;
+  edge latch;
+  edge_iterator latch_ei;
+  unsigned depth = loop_depth (loop);
+
+  header->loop_father = loop;
+  header->loop_depth = depth;
+
+  FOR_EACH_EDGE (latch, latch_ei, loop->header->preds)
+    {
+      if (latch->src->loop_father == loop
+         || !dominated_by_p (CDI_DOMINATORS, latch->src, loop->header))
+       continue;
+
+      num_nodes++;
+      VEC_safe_push (basic_block, heap, stack, latch->src);
+      latch->src->loop_father = loop;
+      latch->src->loop_depth = depth;
+
+      while (!VEC_empty (basic_block, stack))
+       {
+         basic_block node;
+         edge e;
+         edge_iterator ei;
+
+         node = VEC_pop (basic_block, stack);
+
+         FOR_EACH_EDGE (e, ei, node->preds)
+           {
+             basic_block ancestor = e->src;
+
+             if (ancestor->loop_father != loop)
+               {
+                 ancestor->loop_father = loop;
+                 ancestor->loop_depth = depth;
+                 num_nodes++;
+                 VEC_safe_push (basic_block, heap, stack, ancestor);
+               }
+           }

        }
        }

+    }
+  VEC_free (basic_block, heap, stack);
+
+  return num_nodes;
+}
+
+/* Records the vector of superloops of the loop LOOP, whose immediate
+   superloop is FATHER.  */

 
 

-      free (loops->array);
-      loops->array = NULL;
+static void
+establish_preds (struct loop *loop, struct loop *father)
+{
+  loop_p ploop;
+  unsigned depth = loop_depth (father) + 1;
+  unsigned i;
+
+  VEC_truncate (loop_p, loop->superloops, 0);
+  VEC_reserve (loop_p, gc, loop->superloops, depth);
+  for (i = 0; VEC_iterate (loop_p, father->superloops, i, ploop); i++)
+    VEC_quick_push (loop_p, loop->superloops, ploop);
+  VEC_quick_push (loop_p, loop->superloops, father);
+
+  for (ploop = loop->inner; ploop; ploop = ploop->next)
+    establish_preds (ploop, loop);
+}

 
 

-      if (loops->cfg.dom)
-       sbitmap_vector_free (loops->cfg.dom);
+/* Add LOOP to the loop hierarchy tree where FATHER is father of the
+   added loop.  If LOOP has some children, take care of that their
+   pred field will be initialized correctly.  */

 
 

-      if (loops->cfg.dfs_order)
-       free (loops->cfg.dfs_order);
+void
+flow_loop_tree_node_add (struct loop *father, struct loop *loop)
+{
+  loop->next = father->inner;
+  father->inner = loop;

 
 

-      if (loops->shared_headers)
-       sbitmap_free (loops->shared_headers);
+  establish_preds (loop, father);
+}
+
+/* Remove LOOP from the loop hierarchy tree.  */
+
+void
+flow_loop_tree_node_remove (struct loop *loop)
+{
+  struct loop *prev, *father;
+
+  father = loop_outer (loop);
+
+  /* Remove loop from the list of sons.  */
+  if (father->inner == loop)
+    father->inner = loop->next;
+  else
+    {
+      for (prev = father->inner; prev->next != loop; prev = prev->next)
+       continue;
+      prev->next = loop->next;

     }
     }

+
+  VEC_truncate (loop_p, loop->superloops, 0);

 }
 
 }
 

-/* Find the entry edges into the loop with header HEADER and nodes
-   NODES and store in ENTRY_EDGES array.  Return the number of entry
-   edges from the loop.  */
+/* Allocates and returns new loop structure.  */

 
 

-static int
-flow_loop_entry_edges_find (header, nodes, entry_edges)
-     basic_block header;
-     const sbitmap nodes;
-     edge **entry_edges;
+struct loop *
+alloc_loop (void)
+{
+  struct loop *loop = GGC_CNEW (struct loop);
+
+  loop->exits = GGC_CNEW (struct loop_exit);
+  loop->exits->next = loop->exits->prev = loop->exits;
+
+  return loop;
+}
+
+/* Initializes loops structure LOOPS, reserving place for NUM_LOOPS loops
+   (including the root of the loop tree).  */
+
+static void
+init_loops_structure (struct loops *loops, unsigned num_loops)
+{
+  struct loop *root;
+
+  memset (loops, 0, sizeof *loops);
+  loops->larray = VEC_alloc (loop_p, gc, num_loops);
+
+  /* Dummy loop containing whole function.  */
+  root = alloc_loop ();
+  root->num_nodes = n_basic_blocks;
+  root->latch = EXIT_BLOCK_PTR;
+  root->header = ENTRY_BLOCK_PTR;
+  ENTRY_BLOCK_PTR->loop_father = root;
+  EXIT_BLOCK_PTR->loop_father = root;
+
+  VEC_quick_push (loop_p, loops->larray, root);
+  loops->tree_root = root;
+}
+
+/* Find all the natural loops in the function and save in LOOPS structure and
+   recalculate loop_depth information in basic block structures.
+   Return the number of natural loops found.  */
+
+int
+flow_loops_find (struct loops *loops)

 {
 {

+  int b;
+  int num_loops;

   edge e;
   edge e;

-  int num_entries;
+  sbitmap headers;
+  int *dfs_order;
+  int *rc_order;
+  basic_block header;
+  basic_block bb;

 
 

-  *entry_edges = NULL;
+  /* Ensure that the dominators are computed.  */
+  calculate_dominance_info (CDI_DOMINATORS);

 
 

-  num_entries = 0;
-  for (e = header->pred; e; e = e->pred_next)
+  /* Taking care of this degenerate case makes the rest of
+     this code simpler.  */
+  if (n_basic_blocks == NUM_FIXED_BLOCKS)

     {
     {

-      basic_block src = e->src;
+      init_loops_structure (loops, 1);
+      return 1;
+    }
+
+  dfs_order = NULL;
+  rc_order = NULL;
+
+  /* Count the number of loop headers.  This should be the
+     same as the number of natural loops.  */
+  headers = sbitmap_alloc (last_basic_block);
+  sbitmap_zero (headers);

 
 

-      if (src == ENTRY_BLOCK_PTR || ! TEST_BIT (nodes, src->index))
-       num_entries++;
+  num_loops = 0;
+  FOR_EACH_BB (header)
+    {
+      edge_iterator ei;
+
+      header->loop_depth = 0;
+
+      /* If we have an abnormal predecessor, do not consider the
+        loop (not worth the problems).  */
+      FOR_EACH_EDGE (e, ei, header->preds)
+       if (e->flags & EDGE_ABNORMAL)
+         break;
+      if (e)
+       continue;
+
+      FOR_EACH_EDGE (e, ei, header->preds)
+       {
+         basic_block latch = e->src;
+
+         gcc_assert (!(e->flags & EDGE_ABNORMAL));
+
+         /* Look for back edges where a predecessor is dominated
+            by this block.  A natural loop has a single entry
+            node (header) that dominates all the nodes in the
+            loop.  It also has single back edge to the header
+            from a latch node.  */
+         if (latch != ENTRY_BLOCK_PTR
+             && dominated_by_p (CDI_DOMINATORS, latch, header))
+           {
+             /* Shared headers should be eliminated by now.  */
+             SET_BIT (headers, header->index);
+             num_loops++;
+           }
+       }
+    }
+
+  /* Allocate loop structures.  */
+  init_loops_structure (loops, num_loops + 1);
+
+  /* Find and record information about all the natural loops
+     in the CFG.  */
+  FOR_EACH_BB (bb)
+    bb->loop_father = loops->tree_root;
+
+  if (num_loops)
+    {
+      /* Compute depth first search order of the CFG so that outer
+        natural loops will be found before inner natural loops.  */
+      dfs_order = XNEWVEC (int, n_basic_blocks);
+      rc_order = XNEWVEC (int, n_basic_blocks);
+      pre_and_rev_post_order_compute (dfs_order, rc_order, false);
+
+      num_loops = 1;
+
+      for (b = 0; b < n_basic_blocks - NUM_FIXED_BLOCKS; b++)
+       {
+         struct loop *loop;
+         edge_iterator ei;
+
+         /* Search the nodes of the CFG in reverse completion order
+            so that we can find outer loops first.  */
+         if (!TEST_BIT (headers, rc_order[b]))
+           continue;
+
+         header = BASIC_BLOCK (rc_order[b]);
+
+         loop = alloc_loop ();
+         VEC_quick_push (loop_p, loops->larray, loop);
+
+         loop->header = header;
+         loop->num = num_loops;
+         num_loops++;
+
+         flow_loop_tree_node_add (header->loop_father, loop);
+         loop->num_nodes = flow_loop_nodes_find (loop->header, loop);
+
+         /* Look for the latch for this header block, if it has just a
+            single one.  */
+         FOR_EACH_EDGE (e, ei, header->preds)
+           {
+             basic_block latch = e->src;
+
+             if (flow_bb_inside_loop_p (loop, latch))
+               {
+                 if (loop->latch != NULL)
+                   {
+                     /* More than one latch edge.  */
+                     loop->latch = NULL;
+                     break;
+                   }
+                 loop->latch = latch;
+               }
+           }
+       }
+
+      free (dfs_order);
+      free (rc_order);

     }
 
     }
 

-  if (! num_entries)
-    abort ();
+  sbitmap_free (headers);
+
+  loops->exits = NULL;
+  return VEC_length (loop_p, loops->larray);
+}

 
 

-  *entry_edges = (edge *) xmalloc (num_entries * sizeof (edge));
+/* Ratio of frequencies of edges so that one of more latch edges is
+   considered to belong to inner loop with same header.  */
+#define HEAVY_EDGE_RATIO 8
+
+/* Minimum number of samples for that we apply
+   find_subloop_latch_edge_by_profile heuristics.  */
+#define HEAVY_EDGE_MIN_SAMPLES 10
+
+/* If the profile info is available, finds an edge in LATCHES that much more
+   frequent than the remaining edges.  Returns such an edge, or NULL if we do
+   not find one.
+
+   We do not use guessed profile here, only the measured one.  The guessed
+   profile is usually too flat and unreliable for this (and it is mostly based
+   on the loop structure of the program, so it does not make much sense to
+   derive the loop structure from it).  */
+   
+static edge
+find_subloop_latch_edge_by_profile (VEC (edge, heap) *latches)
+{
+  unsigned i;
+  edge e, me = NULL;
+  gcov_type mcount = 0, tcount = 0;

 
 

-  num_entries = 0;
-  for (e = header->pred; e; e = e->pred_next)
+  for (i = 0; VEC_iterate (edge, latches, i, e); i++)

     {
     {

-      basic_block src = e->src;
+      if (e->count > mcount)
+       {
+         me = e;
+         mcount = e->count;
+       }
+      tcount += e->count;
+    }
+
+  if (tcount < HEAVY_EDGE_MIN_SAMPLES
+      || (tcount - mcount) * HEAVY_EDGE_RATIO > tcount)
+    return NULL;
+
+  if (dump_file)
+    fprintf (dump_file,
+            "Found latch edge %d -> %d using profile information.\n",
+            me->src->index, me->dest->index);
+  return me;
+}
+
+/* Among LATCHES, guesses a latch edge of LOOP corresponding to subloop, based
+   on the structure of induction variables.  Returns this edge, or NULL if we
+   do not find any.
+
+   We are quite conservative, and look just for an obvious simple innermost
+   loop (which is the case where we would lose the most performance by not
+   disambiguating the loop).  More precisely, we look for the following
+   situation: The source of the chosen latch edge dominates sources of all
+   the other latch edges.  Additionally, the header does not contain a phi node
+   such that the argument from the chosen edge is equal to the argument from
+   another edge.  */

 
 

-      if (src == ENTRY_BLOCK_PTR || ! TEST_BIT (nodes, src->index))
-       (*entry_edges)[num_entries++] = e;
+static edge
+find_subloop_latch_edge_by_ivs (struct loop *loop ATTRIBUTE_UNUSED, VEC (edge, heap) *latches)
+{
+  edge e, latch = VEC_index (edge, latches, 0);
+  unsigned i;
+  gimple phi;
+  gimple_stmt_iterator psi;
+  tree lop;
+  basic_block bb;
+
+  /* Find the candidate for the latch edge.  */
+  for (i = 1; VEC_iterate (edge, latches, i, e); i++)
+    if (dominated_by_p (CDI_DOMINATORS, latch->src, e->src))
+      latch = e;
+
+  /* Verify that it dominates all the latch edges.  */
+  for (i = 0; VEC_iterate (edge, latches, i, e); i++)
+    if (!dominated_by_p (CDI_DOMINATORS, e->src, latch->src))
+      return NULL;
+
+  /* Check for a phi node that would deny that this is a latch edge of
+     a subloop.  */
+  for (psi = gsi_start_phis (loop->header); !gsi_end_p (psi); gsi_next (&psi))
+    {
+      phi = gsi_stmt (psi);
+      lop = PHI_ARG_DEF_FROM_EDGE (phi, latch);
+
+      /* Ignore the values that are not changed inside the subloop.  */
+      if (TREE_CODE (lop) != SSA_NAME
+         || SSA_NAME_DEF_STMT (lop) == phi)
+       continue;
+      bb = gimple_bb (SSA_NAME_DEF_STMT (lop));
+      if (!bb || !flow_bb_inside_loop_p (loop, bb))
+       continue;
+
+      for (i = 0; VEC_iterate (edge, latches, i, e); i++)
+       if (e != latch
+           && PHI_ARG_DEF_FROM_EDGE (phi, e) == lop)
+         return NULL;

     }
 
     }
 

-  return num_entries;
+  if (dump_file)
+    fprintf (dump_file,
+            "Found latch edge %d -> %d using iv structure.\n",
+            latch->src->index, latch->dest->index);
+  return latch;

 }
 
 }
 

-/* Find the exit edges from the loop using the bitmap of loop nodes
-   NODES and store in EXIT_EDGES array.  Return the number of
-   exit edges from the loop.  */
+/* If we can determine that one of the several latch edges of LOOP behaves
+   as a latch edge of a separate subloop, returns this edge.  Otherwise
+   returns NULL.  */

 
 

-static int
-flow_loop_exit_edges_find (nodes, exit_edges)
-     const sbitmap nodes;
-     edge **exit_edges;
+static edge
+find_subloop_latch_edge (struct loop *loop)
+{
+  VEC (edge, heap) *latches = get_loop_latch_edges (loop);
+  edge latch = NULL;
+
+  if (VEC_length (edge, latches) > 1)
+    {
+      latch = find_subloop_latch_edge_by_profile (latches);
+
+      if (!latch
+         /* We consider ivs to guess the latch edge only in SSA.  Perhaps we
+            should use cfghook for this, but it is hard to imagine it would
+            be useful elsewhere.  */
+         && current_ir_type () == IR_GIMPLE)
+       latch = find_subloop_latch_edge_by_ivs (loop, latches);
+    }
+
+  VEC_free (edge, heap, latches);
+  return latch;
+}
+
+/* Callback for make_forwarder_block.  Returns true if the edge E is marked
+   in the set MFB_REIS_SET.  */
+
+static struct pointer_set_t *mfb_reis_set;
+static bool
+mfb_redirect_edges_in_set (edge e)
+{
+  return pointer_set_contains (mfb_reis_set, e);
+}
+
+/* Creates a subloop of LOOP with latch edge LATCH.  */
+
+static void
+form_subloop (struct loop *loop, edge latch)
+{
+  edge_iterator ei;
+  edge e, new_entry;
+  struct loop *new_loop;
+      
+  mfb_reis_set = pointer_set_create ();
+  FOR_EACH_EDGE (e, ei, loop->header->preds)
+    {
+      if (e != latch)
+       pointer_set_insert (mfb_reis_set, e);
+    }
+  new_entry = make_forwarder_block (loop->header, mfb_redirect_edges_in_set,
+                                   NULL);
+  pointer_set_destroy (mfb_reis_set);
+
+  loop->header = new_entry->src;
+
+  /* Find the blocks and subloops that belong to the new loop, and add it to
+     the appropriate place in the loop tree.  */
+  new_loop = alloc_loop ();
+  new_loop->header = new_entry->dest;
+  new_loop->latch = latch->src;
+  add_loop (new_loop, loop);
+}
+
+/* Make all the latch edges of LOOP to go to a single forwarder block --
+   a new latch of LOOP.  */
+
+static void
+merge_latch_edges (struct loop *loop)
+{
+  VEC (edge, heap) *latches = get_loop_latch_edges (loop);
+  edge latch, e;
+  unsigned i;
+
+  gcc_assert (VEC_length (edge, latches) > 0);
+
+  if (VEC_length (edge, latches) == 1)
+    loop->latch = VEC_index (edge, latches, 0)->src;
+  else
+    {
+      if (dump_file)
+       fprintf (dump_file, "Merged latch edges of loop %d\n", loop->num);
+
+      mfb_reis_set = pointer_set_create ();
+      for (i = 0; VEC_iterate (edge, latches, i, e); i++)
+       pointer_set_insert (mfb_reis_set, e);
+      latch = make_forwarder_block (loop->header, mfb_redirect_edges_in_set,
+                                   NULL);
+      pointer_set_destroy (mfb_reis_set);
+
+      loop->header = latch->dest;
+      loop->latch = latch->src;
+    }
+
+  VEC_free (edge, heap, latches);
+}
+
+/* LOOP may have several latch edges.  Transform it into (possibly several)
+   loops with single latch edge.  */
+
+static void
+disambiguate_multiple_latches (struct loop *loop)

 {
   edge e;
 {
   edge e;

-  int node;
-  int num_exits;
-
-  *exit_edges = NULL;
-
-  /* Check all nodes within the loop to see if there are any
-     successors not in the loop.  Note that a node may have multiple
-     exiting edges ?????  A node can have one jumping edge and one fallthru
-     edge so only one of these can exit the loop.  */
-  num_exits = 0;
-  EXECUTE_IF_SET_IN_SBITMAP (nodes, 0, node, {
-    for (e = BASIC_BLOCK (node)->succ; e; e = e->succ_next)
-      {
-       basic_block dest = e->dest;
-
-       if (dest == EXIT_BLOCK_PTR || ! TEST_BIT (nodes, dest->index))
-           num_exits++;
-      }
-  });
-
-  if (! num_exits)
+
+  /* We eliminate the multiple latches by splitting the header to the forwarder
+     block F and the rest R, and redirecting the edges.  There are two cases:
+
+     1) If there is a latch edge E that corresponds to a subloop (we guess
+        that based on profile -- if it is taken much more often than the
+       remaining edges; and on trees, using the information about induction
+       variables of the loops), we redirect E to R, all the remaining edges to
+       F, then rescan the loops and try again for the outer loop.
+     2) If there is no such edge, we redirect all latch edges to F, and the
+        entry edges to R, thus making F the single latch of the loop.  */
+
+  if (dump_file)
+    fprintf (dump_file, "Disambiguating loop %d with multiple latches\n",
+            loop->num);
+
+  /* During latch merging, we may need to redirect the entry edges to a new
+     block.  This would cause problems if the entry edge was the one from the
+     entry block.  To avoid having to handle this case specially, split
+     such entry edge.  */
+  e = find_edge (ENTRY_BLOCK_PTR, loop->header);
+  if (e)
+    split_edge (e);
+
+  while (1)
+    {
+      e = find_subloop_latch_edge (loop);
+      if (!e)
+       break;
+
+      form_subloop (loop, e);
+    }
+
+  merge_latch_edges (loop);
+}
+
+/* Split loops with multiple latch edges.  */
+
+void
+disambiguate_loops_with_multiple_latches (void)
+{
+  loop_iterator li;
+  struct loop *loop;
+
+  FOR_EACH_LOOP (li, loop, 0)
+    {
+      if (!loop->latch)
+       disambiguate_multiple_latches (loop);
+    }
+}
+
+/* Return nonzero if basic block BB belongs to LOOP.  */
+bool
+flow_bb_inside_loop_p (const struct loop *loop, const_basic_block bb)
+{
+  struct loop *source_loop;
+
+  if (bb == ENTRY_BLOCK_PTR || bb == EXIT_BLOCK_PTR)

     return 0;
 
     return 0;
 

-  *exit_edges = (edge *) xmalloc (num_exits * sizeof (edge));
+  source_loop = bb->loop_father;
+  return loop == source_loop || flow_loop_nested_p (loop, source_loop);
+}

 
 

-  /* Store all exiting edges into an array.  */
-  num_exits = 0;
-  EXECUTE_IF_SET_IN_SBITMAP (nodes, 0, node, {
-    for (e = BASIC_BLOCK (node)->succ; e; e = e->succ_next)
-      {
-       basic_block dest = e->dest;
+/* Enumeration predicate for get_loop_body_with_size.  */
+static bool
+glb_enum_p (const_basic_block bb, const void *glb_loop)
+{
+  const struct loop *const loop = (const struct loop *) glb_loop;
+  return (bb != loop->header
+         && dominated_by_p (CDI_DOMINATORS, bb, loop->header));
+}

 
 

-       if (dest == EXIT_BLOCK_PTR || ! TEST_BIT (nodes, dest->index))
-         (*exit_edges)[num_exits++] = e;
-      }
-  });
+/* Gets basic blocks of a LOOP.  Header is the 0-th block, rest is in dfs
+   order against direction of edges from latch.  Specially, if
+   header != latch, latch is the 1-st block.  LOOP cannot be the fake
+   loop tree root, and its size must be at most MAX_SIZE.  The blocks
+   in the LOOP body are stored to BODY, and the size of the LOOP is
+   returned.  */

 
 

-  return num_exits;
+unsigned
+get_loop_body_with_size (const struct loop *loop, basic_block *body,
+                        unsigned max_size)
+{
+  return dfs_enumerate_from (loop->header, 1, glb_enum_p,
+                            body, max_size, loop);

 }
 
 }
 

-/* Find the nodes contained within the loop with header HEADER and
-   latch LATCH and store in NODES.  Return the number of nodes within
-   the loop.  */
+/* Gets basic blocks of a LOOP.  Header is the 0-th block, rest is in dfs
+   order against direction of edges from latch.  Specially, if
+   header != latch, latch is the 1-st block.  */

 
 

-static int
-flow_loop_nodes_find (header, latch, nodes)
-     basic_block header;
-     basic_block latch;
-     sbitmap nodes;
+basic_block *
+get_loop_body (const struct loop *loop)

 {
 {

-  basic_block *stack;
-  int sp;
-  int num_nodes = 0;
+  basic_block *body, bb;
+  unsigned tv = 0;

 
 

-  stack = (basic_block *) xmalloc (n_basic_blocks * sizeof (basic_block));
-  sp = 0;
+  gcc_assert (loop->num_nodes);

 
 

-  /* Start with only the loop header in the set of loop nodes.  */
-  sbitmap_zero (nodes);
-  SET_BIT (nodes, header->index);
-  num_nodes++;
-  header->loop_depth++;
+  body = XCNEWVEC (basic_block, loop->num_nodes);

 
 

-  /* Push the loop latch on to the stack.  */
-  if (! TEST_BIT (nodes, latch->index))
+  if (loop->latch == EXIT_BLOCK_PTR)

     {
     {

-      SET_BIT (nodes, latch->index);
-      latch->loop_depth++;
-      num_nodes++;
-      stack[sp++] = latch;
+      /* There may be blocks unreachable from EXIT_BLOCK, hence we need to
+        special-case the fake loop that contains the whole function.  */
+      gcc_assert (loop->num_nodes == (unsigned) n_basic_blocks);
+      body[tv++] = loop->header;
+      body[tv++] = EXIT_BLOCK_PTR;
+      FOR_EACH_BB (bb)
+       body[tv++] = bb;

     }
     }

+  else
+    tv = get_loop_body_with_size (loop, body, loop->num_nodes);
+
+  gcc_assert (tv == loop->num_nodes);
+  return body;
+}

 
 

-  while (sp)
+/* Fills dominance descendants inside LOOP of the basic block BB into
+   array TOVISIT from index *TV.  */
+
+static void
+fill_sons_in_loop (const struct loop *loop, basic_block bb,
+                  basic_block *tovisit, int *tv)
+{
+  basic_block son, postpone = NULL;
+
+  tovisit[(*tv)++] = bb;
+  for (son = first_dom_son (CDI_DOMINATORS, bb);
+       son;
+       son = next_dom_son (CDI_DOMINATORS, son))

     {
     {

-      basic_block node;
-      edge e;
+      if (!flow_bb_inside_loop_p (loop, son))
+       continue;

 
 

-      node = stack[--sp];
-      for (e = node->pred; e; e = e->pred_next)
+      if (dominated_by_p (CDI_DOMINATORS, loop->latch, son))

        {
        {

-         basic_block ancestor = e->src;
-
-         /* If each ancestor not marked as part of loop, add to set of
-            loop nodes and push on to stack.  */
-         if (ancestor != ENTRY_BLOCK_PTR
-             && ! TEST_BIT (nodes, ancestor->index))
-           {
-             SET_BIT (nodes, ancestor->index);
-             ancestor->loop_depth++;
-             num_nodes++;
-             stack[sp++] = ancestor;
-           }
+         postpone = son;
+         continue;

        }
        }

+      fill_sons_in_loop (loop, son, tovisit, tv);

     }
     }

-  free (stack);
-  return num_nodes;
+
+  if (postpone)
+    fill_sons_in_loop (loop, postpone, tovisit, tv);

 }
 
 }
 

-/* Find the root node of the loop pre-header extended basic block and
-   the edges along the trace from the root node to the loop header.  */
+/* Gets body of a LOOP (that must be different from the outermost loop)
+   sorted by dominance relation.  Additionally, if a basic block s dominates
+   the latch, then only blocks dominated by s are be after it.  */

 
 

-static void
-flow_loop_pre_header_scan (loop)
-     struct loop *loop;
+basic_block *
+get_loop_body_in_dom_order (const struct loop *loop)

 {
 {

-  int num;
-  basic_block ebb;
-  edge e;
+  basic_block *tovisit;
+  int tv;

 
 

-  loop->num_pre_header_edges = 0;
-  if (loop->num_entries != 1)
-    return;
+  gcc_assert (loop->num_nodes);

 
 

-  ebb = loop->entry_edges[0]->src;
-  if (ebb == ENTRY_BLOCK_PTR)
-    return;
+  tovisit = XCNEWVEC (basic_block, loop->num_nodes);
+
+  gcc_assert (loop->latch != EXIT_BLOCK_PTR);

 
 

-  /* Count number of edges along trace from loop header to
-     root of pre-header extended basic block.  Usually this is
-     only one or two edges.  */
-  for (num = 1; ebb->pred->src != ENTRY_BLOCK_PTR && ! ebb->pred->pred_next;
-       num++)
-    ebb = ebb->pred->src;
+  tv = 0;
+  fill_sons_in_loop (loop, loop->header, tovisit, &tv);

 
 

-  loop->pre_header_edges = (edge *) xmalloc (num * sizeof (edge));
-  loop->num_pre_header_edges = num;
+  gcc_assert (tv == (int) loop->num_nodes);

 
 

-  /* Store edges in order that they are followed.  The source of the first edge
-     is the root node of the pre-header extended basic block and the
-     destination of the last last edge is the loop header.  */
-  for (e = loop->entry_edges[0]; num; e = e->src->pred)
-    loop->pre_header_edges[--num] = e;
+  return tovisit;

 }
 
 }
 

-/* Return the block for the pre-header of the loop with header
-   HEADER where DOM specifies the dominator information.  Return NULL if
-   there is no pre-header.  */
+/* Gets body of a LOOP sorted via provided BB_COMPARATOR.  */

 
 

-static basic_block
-flow_loop_pre_header_find (header, dom)
-     basic_block header;
-     const sbitmap *dom;
+basic_block *
+get_loop_body_in_custom_order (const struct loop *loop, 
+                              int (*bb_comparator) (const void *, const void *))

 {
 {

-  basic_block pre_header;
-  edge e;
+  basic_block *bbs = get_loop_body (loop);
+
+  qsort (bbs, loop->num_nodes, sizeof (basic_block), bb_comparator);
+
+  return bbs;
+}
+
+/* Get body of a LOOP in breadth first sort order.  */
+
+basic_block *
+get_loop_body_in_bfs_order (const struct loop *loop)
+{
+  basic_block *blocks;
+  basic_block bb;
+  bitmap visited;
+  unsigned int i = 0;
+  unsigned int vc = 1;
+
+  gcc_assert (loop->num_nodes);
+  gcc_assert (loop->latch != EXIT_BLOCK_PTR);

 
 

-  /* If block p is a predecessor of the header and is the only block
-     that the header does not dominate, then it is the pre-header.  */
-  pre_header = NULL;
-  for (e = header->pred; e; e = e->pred_next)
+  blocks = XCNEWVEC (basic_block, loop->num_nodes);
+  visited = BITMAP_ALLOC (NULL);
+
+  bb = loop->header;
+  while (i < loop->num_nodes)

     {
     {

-      basic_block node = e->src;
+      edge e;
+      edge_iterator ei;

 
 

-      if (node != ENTRY_BLOCK_PTR
-         && ! TEST_BIT (dom[node->index], header->index))
+      if (!bitmap_bit_p (visited, bb->index))

        {
        {

-         if (pre_header == NULL)
-           pre_header = node;
-         else
+         /* This basic block is now visited */
+         bitmap_set_bit (visited, bb->index);
+         blocks[i++] = bb;
+       }
+
+      FOR_EACH_EDGE (e, ei, bb->succs)
+       {
+         if (flow_bb_inside_loop_p (loop, e->dest))

            {
            {

-             /* There are multiple edges into the header from outside
-                the loop so there is no pre-header block.  */
-             pre_header = NULL;
-             break;
+             if (!bitmap_bit_p (visited, e->dest->index))
+               {
+                 bitmap_set_bit (visited, e->dest->index);
+                 blocks[i++] = e->dest;
+               }

            }
        }
            }
        }

+
+      gcc_assert (i >= vc);
+
+      bb = blocks[vc++];

     }
 
     }
 

-  return pre_header;
+  BITMAP_FREE (visited);
+  return blocks;
+}
+
+/* Hash function for struct loop_exit.  */
+
+static hashval_t
+loop_exit_hash (const void *ex)
+{
+  const struct loop_exit *const exit = (const struct loop_exit *) ex;
+
+  return htab_hash_pointer (exit->e);

 }
 
 }
 

-/* Add LOOP to the loop hierarchy tree where PREVLOOP was the loop
-   previously added.  The insertion algorithm assumes that the loops
-   are added in the order found by a depth first search of the CFG.  */
+/* Equality function for struct loop_exit.  Compares with edge.  */
+
+static int
+loop_exit_eq (const void *ex, const void *e)
+{
+  const struct loop_exit *const exit = (const struct loop_exit *) ex;
+
+  return exit->e == e;
+}
+
+/* Frees the list of loop exit descriptions EX.  */

 
 static void
 
 static void

-flow_loop_tree_node_add (prevloop, loop)
-     struct loop *prevloop;
-     struct loop *loop;
+loop_exit_free (void *ex)

 {
 {

+  struct loop_exit *exit = (struct loop_exit *) ex, *next;

 
 

-  if (flow_loop_nested_p (prevloop, loop))
+  for (; exit; exit = next)

     {
     {

-      prevloop->inner = loop;
-      loop->outer = prevloop;
-      return;
+      next = exit->next_e;
+         
+      exit->next->prev = exit->prev;
+      exit->prev->next = exit->next;
+
+      ggc_free (exit);

     }
     }

+}

 
 

-  for (; prevloop->outer; prevloop = prevloop->outer)
-    if (flow_loop_nested_p (prevloop->outer, loop))
-      {
-       prevloop->next = loop;
-       loop->outer = prevloop->outer;
-       return;
-      }
+/* Returns the list of records for E as an exit of a loop.  */

 
 

-  prevloop->next = loop;
-  loop->outer = NULL;
+static struct loop_exit *
+get_exit_descriptions (edge e)
+{
+  return (struct loop_exit *) htab_find_with_hash (current_loops->exits, e,
+                                                  htab_hash_pointer (e));

 }
 
 }
 

-/* Build the loop hierarchy tree for LOOPS.  */
+/* Updates the lists of loop exits in that E appears.
+   If REMOVED is true, E is being removed, and we
+   just remove it from the lists of exits.
+   If NEW_EDGE is true and E is not a loop exit, we
+   do not try to remove it from loop exit lists.  */

 
 

-static void
-flow_loops_tree_build (loops)
-     struct loops *loops;
+void
+rescan_loop_exit (edge e, bool new_edge, bool removed)

 {
 {

-  int i;
-  int num_loops;
+  void **slot;
+  struct loop_exit *exits = NULL, *exit;
+  struct loop *aloop, *cloop;
+
+  if (!loops_state_satisfies_p (LOOPS_HAVE_RECORDED_EXITS))
+    return;
+
+  if (!removed
+      && e->src->loop_father != NULL
+      && e->dest->loop_father != NULL
+      && !flow_bb_inside_loop_p (e->src->loop_father, e->dest))
+    {
+      cloop = find_common_loop (e->src->loop_father, e->dest->loop_father);
+      for (aloop = e->src->loop_father;
+          aloop != cloop;
+          aloop = loop_outer (aloop))
+       {
+         exit = GGC_NEW (struct loop_exit);
+         exit->e = e;
+
+         exit->next = aloop->exits->next;
+         exit->prev = aloop->exits;
+         exit->next->prev = exit;
+         exit->prev->next = exit;
+
+         exit->next_e = exits;
+         exits = exit;
+       }
+    } 

 
 

-  num_loops = loops->num;
-  if (! num_loops)
+  if (!exits && new_edge)

     return;
 
     return;
 

-  /* Root the loop hierarchy tree with the first loop found.
-     Since we used a depth first search this should be the
-     outermost loop.  */
-  loops->tree_root = &loops->array[0];
-  loops->tree_root->outer = loops->tree_root->inner
-    = loops->tree_root->next = NULL;
+  slot = htab_find_slot_with_hash (current_loops->exits, e,
+                                  htab_hash_pointer (e),
+                                  exits ? INSERT : NO_INSERT);
+  if (!slot)
+    return;

 
 

-  /* Add the remaining loops to the tree.  */
-  for (i = 1; i < num_loops; i++)
-    flow_loop_tree_node_add (&loops->array[i - 1], &loops->array[i]);
+  if (exits)
+    {
+      if (*slot)
+       loop_exit_free (*slot);
+      *slot = exits;
+    }
+  else
+    htab_clear_slot (current_loops->exits, slot);

 }
 
 }
 

-/* Helper function to compute loop nesting depth and enclosed loop level
-   for the natural loop specified by LOOP at the loop depth DEPTH.
-   Returns the loop level.  */
+/* For each loop, record list of exit edges, and start maintaining these
+   lists.  */

 
 

-static int
-flow_loop_level_compute (loop, depth)
-     struct loop *loop;
-     int depth;
+void
+record_loop_exits (void)

 {
 {

-  struct loop *inner;
-  int level = 1;
+  basic_block bb;
+  edge_iterator ei;
+  edge e;

 
 

-  if (! loop)
-    return 0;
+  if (!current_loops)
+    return;

 
 

-  /* Traverse loop tree assigning depth and computing level as the
-     maximum level of all the inner loops of this loop.  The loop
-     level is equivalent to the height of the loop in the loop tree
-     and corresponds to the number of enclosed loop levels (including
-     itself).  */
-  for (inner = loop->inner; inner; inner = inner->next)
-    {
-      int ilevel = flow_loop_level_compute (inner, depth + 1) + 1;
+  if (loops_state_satisfies_p (LOOPS_HAVE_RECORDED_EXITS))
+    return;
+  loops_state_set (LOOPS_HAVE_RECORDED_EXITS);

 
 

-      level = MAX (ilevel, level);
-    }
+  gcc_assert (current_loops->exits == NULL);
+  current_loops->exits = htab_create_alloc (2 * number_of_loops (),
+                                           loop_exit_hash,
+                                           loop_exit_eq,
+                                           loop_exit_free,
+                                           ggc_calloc, ggc_free);

 
 

-  loop->level = level;
-  loop->depth = depth;
-  return level;
+  FOR_EACH_BB (bb)
+    {
+      FOR_EACH_EDGE (e, ei, bb->succs)
+       {
+         rescan_loop_exit (e, true, false);
+       }
+    }

 }
 
 }
 

-/* Compute the loop nesting depth and enclosed loop level for the loop
-   hierarchy tree specified by LOOPS.  Return the maximum enclosed loop
-   level.  */
+/* Dumps information about the exit in *SLOT to FILE.
+   Callback for htab_traverse.  */

 
 static int
 
 static int

-flow_loops_level_compute (loops)
-     struct loops *loops;
+dump_recorded_exit (void **slot, void *file)

 {
 {

-  int levels = 0;
-  struct loop *loop;
-  int level;
+  struct loop_exit *exit = (struct loop_exit *) *slot;
+  unsigned n = 0;
+  edge e = exit->e;
+
+  for (; exit != NULL; exit = exit->next_e)
+    n++;

 
 

-  /* Traverse all the outer level loops.  */
-  for (loop = loops->tree_root; loop; loop = loop->next)
+  fprintf ((FILE*) file, "Edge %d->%d exits %u loops\n",
+          e->src->index, e->dest->index, n);
+
+  return 1;
+}
+
+/* Dumps the recorded exits of loops to FILE.  */
+
+extern void dump_recorded_exits (FILE *);
+void
+dump_recorded_exits (FILE *file)
+{
+  if (!current_loops->exits)
+    return;
+  htab_traverse (current_loops->exits, dump_recorded_exit, file);
+}
+
+/* Releases lists of loop exits.  */
+
+void
+release_recorded_exits (void)
+{
+  gcc_assert (loops_state_satisfies_p (LOOPS_HAVE_RECORDED_EXITS));
+  htab_delete (current_loops->exits);
+  current_loops->exits = NULL;
+  loops_state_clear (LOOPS_HAVE_RECORDED_EXITS);
+}
+
+/* Returns the list of the exit edges of a LOOP.  */
+
+VEC (edge, heap) *
+get_loop_exit_edges (const struct loop *loop)
+{
+  VEC (edge, heap) *edges = NULL;
+  edge e;
+  unsigned i;
+  basic_block *body;
+  edge_iterator ei;
+  struct loop_exit *exit;
+
+  gcc_assert (loop->latch != EXIT_BLOCK_PTR);
+
+  /* If we maintain the lists of exits, use them.  Otherwise we must
+     scan the body of the loop.  */
+  if (loops_state_satisfies_p (LOOPS_HAVE_RECORDED_EXITS))

     {
     {

-      level = flow_loop_level_compute (loop, 1);
-      levels = MAX (levels, level);
+      for (exit = loop->exits->next; exit->e; exit = exit->next)
+       VEC_safe_push (edge, heap, edges, exit->e);
+    }
+  else
+    {
+      body = get_loop_body (loop);
+      for (i = 0; i < loop->num_nodes; i++)
+       FOR_EACH_EDGE (e, ei, body[i]->succs)
+         {
+           if (!flow_bb_inside_loop_p (loop, e->dest))
+             VEC_safe_push (edge, heap, edges, e);
+         }
+      free (body);

     }
 
     }
 

-  return levels;
+  return edges;

 }
 
 }
 

-/* Scan a single natural loop specified by LOOP collecting information
-   about it specified by FLAGS.  */
+/* Counts the number of conditional branches inside LOOP.  */

 
 

-int
-flow_loop_scan (loops, loop, flags)
-     struct loops *loops;
-     struct loop *loop;
-     int flags;
+unsigned
+num_loop_branches (const struct loop *loop)

 {
 {

-  /* Determine prerequisites.  */
-  if ((flags & LOOP_EXITS_DOMS) && ! loop->exit_edges)
-    flags |= LOOP_EXIT_EDGES;
+  unsigned i, n;
+  basic_block * body;

 
 

-  if (flags & LOOP_ENTRY_EDGES)
-    /* Find edges which enter the loop header.  Note that the entry edges
-       should only enter the header of a natural loop.  */
-    loop->num_entries = flow_loop_entry_edges_find (loop->header, loop->nodes,
-                                                   &loop->entry_edges);
+  gcc_assert (loop->latch != EXIT_BLOCK_PTR);

 
 

-  if (flags & LOOP_EXIT_EDGES)
-    /* Find edges which exit the loop.  */
-    loop->num_exits
-      = flow_loop_exit_edges_find (loop->nodes, &loop->exit_edges);
+  body = get_loop_body (loop);
+  n = 0;
+  for (i = 0; i < loop->num_nodes; i++)
+    if (EDGE_COUNT (body[i]->succs) >= 2)
+      n++;
+  free (body);

 
 

-  if (flags & LOOP_EXITS_DOMS)
-    {
-      int j;
+  return n;
+}

 
 

-      /* Determine which loop nodes dominate all the exits
-        of the loop.  */
-      loop->exits_doms = sbitmap_alloc (n_basic_blocks);
-      sbitmap_copy (loop->exits_doms, loop->nodes);
-      for (j = 0; j < loop->num_exits; j++)
-       sbitmap_a_and_b (loop->exits_doms, loop->exits_doms,
-                        loops->cfg.dom[loop->exit_edges[j]->src->index]);
+/* Adds basic block BB to LOOP.  */
+void
+add_bb_to_loop (basic_block bb, struct loop *loop)
+{
+  unsigned i;
+  loop_p ploop;
+  edge_iterator ei;
+  edge e;

 
 

-      /* The header of a natural loop must dominate
-        all exits.  */
-      if (! TEST_BIT (loop->exits_doms, loop->header->index))
-       abort ();
+  gcc_assert (bb->loop_father == NULL);
+  bb->loop_father = loop;
+  bb->loop_depth = loop_depth (loop);
+  loop->num_nodes++;
+  for (i = 0; VEC_iterate (loop_p, loop->superloops, i, ploop); i++)
+    ploop->num_nodes++;
+
+  FOR_EACH_EDGE (e, ei, bb->succs)
+    {
+      rescan_loop_exit (e, true, false);
+    }
+  FOR_EACH_EDGE (e, ei, bb->preds)
+    {
+      rescan_loop_exit (e, true, false);

     }
     }

+}

 
 

-  if (flags & LOOP_PRE_HEADER)
+/* Remove basic block BB from loops.  */
+void
+remove_bb_from_loops (basic_block bb)
+{
+  int i;
+  struct loop *loop = bb->loop_father;
+  loop_p ploop;
+  edge_iterator ei;
+  edge e;
+
+  gcc_assert (loop != NULL);
+  loop->num_nodes--;
+  for (i = 0; VEC_iterate (loop_p, loop->superloops, i, ploop); i++)
+    ploop->num_nodes--;
+  bb->loop_father = NULL;
+  bb->loop_depth = 0;
+
+  FOR_EACH_EDGE (e, ei, bb->succs)

     {
     {

-      /* Look to see if the loop has a pre-header node.  */
-      loop->pre_header
-       = flow_loop_pre_header_find (loop->header, loops->cfg.dom);
+      rescan_loop_exit (e, false, true);
+    }
+  FOR_EACH_EDGE (e, ei, bb->preds)
+    {
+      rescan_loop_exit (e, false, true);
+    }
+}

 
 

-      /* Find the blocks within the extended basic block of
-        the loop pre-header.  */
-      flow_loop_pre_header_scan (loop);
+/* Finds nearest common ancestor in loop tree for given loops.  */
+struct loop *
+find_common_loop (struct loop *loop_s, struct loop *loop_d)
+{
+  unsigned sdepth, ddepth;
+
+  if (!loop_s) return loop_d;
+  if (!loop_d) return loop_s;
+
+  sdepth = loop_depth (loop_s);
+  ddepth = loop_depth (loop_d);
+
+  if (sdepth < ddepth)
+    loop_d = VEC_index (loop_p, loop_d->superloops, sdepth);
+  else if (sdepth > ddepth)
+    loop_s = VEC_index (loop_p, loop_s->superloops, ddepth);
+
+  while (loop_s != loop_d)
+    {
+      loop_s = loop_outer (loop_s);
+      loop_d = loop_outer (loop_d);

     }
     }

+  return loop_s;
+}

 
 

-  return 1;
+/* Removes LOOP from structures and frees its data.  */
+
+void
+delete_loop (struct loop *loop)
+{
+  /* Remove the loop from structure.  */
+  flow_loop_tree_node_remove (loop);
+
+  /* Remove loop from loops array.  */
+  VEC_replace (loop_p, current_loops->larray, loop->num, NULL);
+
+  /* Free loop data.  */
+  flow_loop_free (loop);

 }
 
 }
 

-/* Find all the natural loops in the function and save in LOOPS structure and
-   recalculate loop_depth information in basic block structures.  FLAGS
-   controls which loop information is collected.  Return the number of natural
-   loops found.  */
+/* Cancels the LOOP; it must be innermost one.  */

 
 

-int
-flow_loops_find (loops, flags)
-     struct loops *loops;
-     int flags;
+static void
+cancel_loop (struct loop *loop)

 {
 {

-  int i;
-  int b;
-  int num_loops;
-  edge e;
-  sbitmap headers;
-  sbitmap *dom;
-  int *dfs_order;
-  int *rc_order;
+  basic_block *bbs;
+  unsigned i;
+  struct loop *outer = loop_outer (loop);

 
 

-  /* This function cannot be repeatedly called with different
-     flags to build up the loop information.  The loop tree
-     must always be built if this function is called.  */
-  if (! (flags & LOOP_TREE))
-    abort ();
+  gcc_assert (!loop->inner);

 
 

-  memset (loops, 0, sizeof *loops);
+  /* Move blocks up one level (they should be removed as soon as possible).  */
+  bbs = get_loop_body (loop);
+  for (i = 0; i < loop->num_nodes; i++)
+    bbs[i]->loop_father = outer;

 
 

-  /* Taking care of this degenerate case makes the rest of
-     this code simpler.  */
-  if (n_basic_blocks == 0)
-    return 0;
+  delete_loop (loop);
+}

 
 

-  dfs_order = NULL;
-  rc_order = NULL;
+/* Cancels LOOP and all its subloops.  */
+void
+cancel_loop_tree (struct loop *loop)
+{
+  while (loop->inner)
+    cancel_loop_tree (loop->inner);
+  cancel_loop (loop);
+}

 
 

-  /* Compute the dominators.  */
-  dom = sbitmap_vector_alloc (n_basic_blocks, n_basic_blocks);
-  calculate_dominance_info (NULL, dom, CDI_DOMINATORS);
+/* Checks that information about loops is correct
+     -- sizes of loops are all right
+     -- results of get_loop_body really belong to the loop
+     -- loop header have just single entry edge and single latch edge
+     -- loop latches have only single successor that is header of their loop
+     -- irreducible loops are correctly marked
+  */
+void
+verify_loop_structure (void)
+{
+  unsigned *sizes, i, j;
+  sbitmap irreds;
+  basic_block *bbs, bb;
+  struct loop *loop;
+  int err = 0;
+  edge e;
+  unsigned num = number_of_loops ();
+  loop_iterator li;
+  struct loop_exit *exit, *mexit;

 
 

-  /* Count the number of loop edges (back edges).  This should be the
-     same as the number of natural loops.  */
-  num_loops = 0;
-  for (b = 0; b < n_basic_blocks; b++)
-    {
-      basic_block header;
+  /* Check sizes.  */
+  sizes = XCNEWVEC (unsigned, num);
+  sizes[0] = 2;

 
 

-      header = BASIC_BLOCK (b);
-      header->loop_depth = 0;
+  FOR_EACH_BB (bb)
+    for (loop = bb->loop_father; loop; loop = loop_outer (loop))
+      sizes[loop->num]++;
+
+  FOR_EACH_LOOP (li, loop, LI_INCLUDE_ROOT)
+    {
+      i = loop->num;

 
 

-      for (e = header->pred; e; e = e->pred_next)
+      if (loop->num_nodes != sizes[i])

        {
        {

-         basic_block latch = e->src;
+         error ("size of loop %d should be %d, not %d",
+                  i, sizes[i], loop->num_nodes);
+         err = 1;
+       }
+    }

 
 

-         /* Look for back edges where a predecessor is dominated
-            by this block.  A natural loop has a single entry
-            node (header) that dominates all the nodes in the
-            loop.  It also has single back edge to the header
-            from a latch node.  Note that multiple natural loops
-            may share the same header.  */
-         if (b != header->index)
-           abort ();
+  /* Check get_loop_body.  */
+  FOR_EACH_LOOP (li, loop, 0)
+    {
+      bbs = get_loop_body (loop);
+
+      for (j = 0; j < loop->num_nodes; j++)
+       if (!flow_bb_inside_loop_p (loop, bbs[j]))
+         {
+           error ("bb %d do not belong to loop %d",
+                   bbs[j]->index, loop->num);
+           err = 1;
+         }
+      free (bbs);
+    }
+
+  /* Check headers and latches.  */
+  FOR_EACH_LOOP (li, loop, 0)
+    {
+      i = loop->num;

 
 

-         if (latch != ENTRY_BLOCK_PTR && TEST_BIT (dom[latch->index], b))
-           num_loops++;
+      if (loops_state_satisfies_p (LOOPS_HAVE_PREHEADERS)
+         && EDGE_COUNT (loop->header->preds) != 2)
+       {
+         error ("loop %d's header does not have exactly 2 entries", i);
+         err = 1;
+       }
+      if (loops_state_satisfies_p (LOOPS_HAVE_SIMPLE_LATCHES))
+       {
+         if (!single_succ_p (loop->latch))
+           {
+             error ("loop %d's latch does not have exactly 1 successor", i);
+             err = 1;
+           }
+         if (single_succ (loop->latch) != loop->header)
+           {
+             error ("loop %d's latch does not have header as successor", i);
+             err = 1;
+           }
+         if (loop->latch->loop_father != loop)
+           {
+             error ("loop %d's latch does not belong directly to it", i);
+             err = 1;
+           }
+       }
+      if (loop->header->loop_father != loop)
+       {
+         error ("loop %d's header does not belong directly to it", i);
+         err = 1;
+       }
+      if (loops_state_satisfies_p (LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS)
+         && (loop_latch_edge (loop)->flags & EDGE_IRREDUCIBLE_LOOP))
+       {
+         error ("loop %d's latch is marked as part of irreducible region", i);
+         err = 1;

        }
     }
 
        }
     }
 

-  if (num_loops)
+  /* Check irreducible loops.  */
+  if (loops_state_satisfies_p (LOOPS_HAVE_MARKED_IRREDUCIBLE_REGIONS))

     {
     {

-      /* Compute depth first search order of the CFG so that outer
-        natural loops will be found before inner natural loops.  */
-      dfs_order = (int *) xmalloc (n_basic_blocks * sizeof (int));
-      rc_order = (int *) xmalloc (n_basic_blocks * sizeof (int));
-      flow_depth_first_order_compute (dfs_order, rc_order);
+      /* Record old info.  */
+      irreds = sbitmap_alloc (last_basic_block);
+      FOR_EACH_BB (bb)
+       {
+         edge_iterator ei;
+         if (bb->flags & BB_IRREDUCIBLE_LOOP)
+           SET_BIT (irreds, bb->index);
+         else
+           RESET_BIT (irreds, bb->index);
+         FOR_EACH_EDGE (e, ei, bb->succs)
+           if (e->flags & EDGE_IRREDUCIBLE_LOOP)
+             e->flags |= EDGE_ALL_FLAGS + 1;
+       }

 
 

-      /* Save CFG derived information to avoid recomputing it.  */
-      loops->cfg.dom = dom;
-      loops->cfg.dfs_order = dfs_order;
-      loops->cfg.rc_order = rc_order;
+      /* Recount it.  */
+      mark_irreducible_loops ();

 
 

-      /* Allocate loop structures.  */
-      loops->array
-       = (struct loop *) xcalloc (num_loops, sizeof (struct loop));
+      /* Compare.  */
+      FOR_EACH_BB (bb)
+       {
+         edge_iterator ei;

 
 

-      headers = sbitmap_alloc (n_basic_blocks);
-      sbitmap_zero (headers);
+         if ((bb->flags & BB_IRREDUCIBLE_LOOP)
+             && !TEST_BIT (irreds, bb->index))
+           {
+             error ("basic block %d should be marked irreducible", bb->index);
+             err = 1;
+           }
+         else if (!(bb->flags & BB_IRREDUCIBLE_LOOP)
+             && TEST_BIT (irreds, bb->index))
+           {
+             error ("basic block %d should not be marked irreducible", bb->index);
+             err = 1;
+           }
+         FOR_EACH_EDGE (e, ei, bb->succs)
+           {
+             if ((e->flags & EDGE_IRREDUCIBLE_LOOP)
+                 && !(e->flags & (EDGE_ALL_FLAGS + 1)))
+               {
+                 error ("edge from %d to %d should be marked irreducible",
+                        e->src->index, e->dest->index);
+                 err = 1;
+               }
+             else if (!(e->flags & EDGE_IRREDUCIBLE_LOOP)
+                      && (e->flags & (EDGE_ALL_FLAGS + 1)))
+               {
+                 error ("edge from %d to %d should not be marked irreducible",
+                        e->src->index, e->dest->index);
+                 err = 1;
+               }
+             e->flags &= ~(EDGE_ALL_FLAGS + 1);
+           }
+       }
+      free (irreds);
+    }

 
 

-      loops->shared_headers = sbitmap_alloc (n_basic_blocks);
-      sbitmap_zero (loops->shared_headers);
+  /* Check the recorded loop exits.  */
+  FOR_EACH_LOOP (li, loop, 0)
+    {
+      if (!loop->exits || loop->exits->e != NULL)
+       {
+         error ("corrupted head of the exits list of loop %d",
+                loop->num);
+         err = 1;
+       }
+      else
+       {
+         /* Check that the list forms a cycle, and all elements except
+            for the head are nonnull.  */
+         for (mexit = loop->exits, exit = mexit->next, i = 0;
+              exit->e && exit != mexit;
+              exit = exit->next)
+           {
+             if (i++ & 1)
+               mexit = mexit->next;
+           }
+
+         if (exit != loop->exits)
+           {
+             error ("corrupted exits list of loop %d", loop->num);
+             err = 1;
+           }
+       }

 
 

-      /* Find and record information about all the natural loops
-        in the CFG.  */
-      num_loops = 0;
-      for (b = n_basic_blocks - 1; b >= 0; b--)
+      if (!loops_state_satisfies_p (LOOPS_HAVE_RECORDED_EXITS))

        {
        {

-         basic_block latch;
+         if (loop->exits->next != loop->exits)
+           {
+             error ("nonempty exits list of loop %d, but exits are not recorded",
+                    loop->num);
+             err = 1;
+           }
+       }
+    }

 
 

-         /* Search the nodes of the CFG in reverse completion order
-            so that we can find outer loops first.  */
-         latch = BASIC_BLOCK (rc_order[b]);
+  if (loops_state_satisfies_p (LOOPS_HAVE_RECORDED_EXITS))
+    {
+      unsigned n_exits = 0, eloops;

 
 

-         /* Look for all the possible headers for this latch block.  */
-         for (e = latch->succ; e; e = e->succ_next)
+      memset (sizes, 0, sizeof (unsigned) * num);
+      FOR_EACH_BB (bb)
+       {
+         edge_iterator ei;
+         if (bb->loop_father == current_loops->tree_root)
+           continue;
+         FOR_EACH_EDGE (e, ei, bb->succs)

            {
            {

-             basic_block header = e->dest;
-
-             /* Look for forward edges where this block is dominated by
-                a successor of this block.  A natural loop has a single
-                entry node (header) that dominates all the nodes in the
-                loop.  It also has single back edge to the header from a
-                latch node.  Note that multiple natural loops may share
-                the same header.  */
-             if (header != EXIT_BLOCK_PTR
-                 && TEST_BIT (dom[latch->index], header->index))
-               {
-                 struct loop *loop;
+             if (flow_bb_inside_loop_p (bb->loop_father, e->dest))
+               continue;

 
 

-                 loop = loops->array + num_loops;
+             n_exits++;
+             exit = get_exit_descriptions (e);
+             if (!exit)
+               {
+                 error ("Exit %d->%d not recorded", 
+                        e->src->index, e->dest->index);
+                 err = 1;
+               }
+             eloops = 0;
+             for (; exit; exit = exit->next_e)
+               eloops++;

 
 

-                 loop->header = header;
-                 loop->latch = latch;
-                 loop->num = num_loops;
+             for (loop = bb->loop_father;
+                  loop != e->dest->loop_father;
+                  loop = loop_outer (loop))
+               {
+                 eloops--;
+                 sizes[loop->num]++;
+               }

 
 

-                 num_loops++;
+             if (eloops != 0)
+               {
+                 error ("Wrong list of exited loops for edge  %d->%d", 
+                        e->src->index, e->dest->index);
+                 err = 1;

                }
            }
        }
 
                }
            }
        }
 

-      for (i = 0; i < num_loops; i++)
+      if (n_exits != htab_elements (current_loops->exits))

        {
        {

-         struct loop *loop = &loops->array[i];
-
-         /* Keep track of blocks that are loop headers so
-            that we can tell which loops should be merged.  */
-         if (TEST_BIT (headers, loop->header->index))
-           SET_BIT (loops->shared_headers, loop->header->index);
-         SET_BIT (headers, loop->header->index);
-
-         /* Find nodes contained within the loop.  */
-         loop->nodes = sbitmap_alloc (n_basic_blocks);
-         loop->num_nodes
-           = flow_loop_nodes_find (loop->header, loop->latch, loop->nodes);
-
-         /* Compute first and last blocks within the loop.
-            These are often the same as the loop header and
-            loop latch respectively, but this is not always
-            the case.  */
-         loop->first
-           = BASIC_BLOCK (sbitmap_first_set_bit (loop->nodes));
-         loop->last
-           = BASIC_BLOCK (sbitmap_last_set_bit (loop->nodes));
-
-         flow_loop_scan (loops, loop, flags);
+         error ("Too many loop exits recorded");
+         err = 1;

        }
 
        }
 

-      /* Natural loops with shared headers may either be disjoint or
-        nested.  Disjoint loops with shared headers cannot be inner
-        loops and should be merged.  For now just mark loops that share
-        headers.  */
-      for (i = 0; i < num_loops; i++)
-       if (TEST_BIT (loops->shared_headers, loops->array[i].header->index))
-         loops->array[i].shared = 1;
-
-      sbitmap_free (headers);
+      FOR_EACH_LOOP (li, loop, 0)
+       {
+         eloops = 0;
+         for (exit = loop->exits->next; exit->e; exit = exit->next)
+           eloops++;
+         if (eloops != sizes[loop->num])
+           {
+             error ("%d exits recorded for loop %d (having %d exits)",
+                    eloops, loop->num, sizes[loop->num]);
+             err = 1;
+           }
+       }

     }
     }

-  else
-    sbitmap_vector_free (dom);

 
 

-  loops->num = num_loops;
+  gcc_assert (!err);
+
+  free (sizes);
+}
+
+/* Returns latch edge of LOOP.  */
+edge
+loop_latch_edge (const struct loop *loop)
+{
+  return find_edge (loop->latch, loop->header);
+}
+
+/* Returns preheader edge of LOOP.  */
+edge
+loop_preheader_edge (const struct loop *loop)
+{
+  edge e;
+  edge_iterator ei;

 
 

-  /* Build the loop hierarchy tree.  */
-  flow_loops_tree_build (loops);
+  gcc_assert (loops_state_satisfies_p (LOOPS_HAVE_PREHEADERS));

 
 

-  /* Assign the loop nesting depth and enclosed loop level for each
-     loop.  */
-  loops->levels = flow_loops_level_compute (loops);
+  FOR_EACH_EDGE (e, ei, loop->header->preds)
+    if (e->src != loop->latch)
+      break;

 
 

-  return num_loops;
+  return e;

 }
 
 }
 

-/* Update the information regarding the loops in the CFG
-   specified by LOOPS.  */
+/* Returns true if E is an exit of LOOP.  */

 
 

-int
-flow_loops_update (loops, flags)
-     struct loops *loops;
-     int flags;
+bool
+loop_exit_edge_p (const struct loop *loop, const_edge e)

 {
 {

-  /* One day we may want to update the current loop data.  For now
-     throw away the old stuff and rebuild what we need.  */
-  if (loops->array)
-    flow_loops_free (loops);
+  return (flow_bb_inside_loop_p (loop, e->src)
+         && !flow_bb_inside_loop_p (loop, e->dest));
+}
+
+/* Returns the single exit edge of LOOP, or NULL if LOOP has either no exit
+   or more than one exit.  If loops do not have the exits recorded, NULL
+   is returned always.  */

 
 

-  return flow_loops_find (loops, flags);
+edge
+single_exit (const struct loop *loop)
+{
+  struct loop_exit *exit = loop->exits->next;
+
+  if (!loops_state_satisfies_p (LOOPS_HAVE_RECORDED_EXITS))
+    return NULL;
+
+  if (exit->e && exit->next == loop->exits)
+    return exit->e;
+  else
+    return NULL;

 }
 
 }
 

-/* Return non-zero if edge E enters header of LOOP from outside of LOOP.  */
+/* Returns true when BB has an edge exiting LOOP.  */

 
 

-int
-flow_loop_outside_edge_p (loop, e)
-     const struct loop *loop;
-     edge e;
+bool
+is_loop_exit (struct loop *loop, basic_block bb)

 {
 {

-  if (e->dest != loop->header)
-    abort ();
+  edge e;
+  edge_iterator ei;
+
+  FOR_EACH_EDGE (e, ei, bb->preds)
+    if (loop_exit_edge_p (loop, e))
+      return true;

 
 

-  return (e->src == ENTRY_BLOCK_PTR)
-    || ! TEST_BIT (loop->nodes, e->src->index);
+  return false;

 }
 }