2000-09-12 Michael Hayes <mhayes@cygnus.com>

	* basic-block.h (LOOP_TREE, LOOP_PRE_HEADER, LOOP_EDGES): New.
	(LOOP_EXITS_DOMS, LOOP_ALL): Likewise.
	(flow_loops_update): New prototype.
	(flow_loops_find): Add flags to prototype.
	(struct loop): Add `pre_header_root' and `pre_header_trace' fields.
	* flow.c (flow_loop_pre_header_scan): New.
	(flow_loop_dump): Dump pre-header root and trace and exit dominators.
	(flow_loop_free): Free pre-header root and trace and exit dominators.
	(flow_loops_find): New argument flags.
	(flow_loops_update): New function.
	* toplev.c (rest_of_compilation): Add flag argument to flow_loops_find.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@36333 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 156 insertions, 54 deletions

diff --git a/gcc/flow.c b/gcc/flow.c
index 545f248d549..c2ae9650c7c 100644
--- a/gcc/flow.c
+++ b/gcc/flow.c
@@ -432,7 +432,9 @@ static basic_block flow_dfs_compute_reverse_execute
   PARAMS ((depth_first_search_ds));
 static void flow_dfs_compute_reverse_finish
   PARAMS ((depth_first_search_ds));
-static basic_block flow_loop_pre_header_find PARAMS ((basic_block, const 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));
@@ -7374,13 +7376,20 @@ flow_loop_dump (loop, file, loop_dump_aux, verbose)
 	   loop->depth, loop->level,
 	   (long) (loop->outer ? loop->outer->num : -1));
 
-  flow_edge_list_print (";;   entry edges", loop->entry_edges,
+  if (loop->pre_header_root)
+    fprintf (file, ";;  pre-header root %d\n", 
+	     loop->pre_header_root->index);
+  if (loop->pre_header_trace)
+    flow_nodes_print (";;  pre-header trace", loop->pre_header_trace,
+		      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,
+  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);
   if (loop_dump_aux)
     loop_dump_aux (loop, file, verbose);
 }
@@ -7463,12 +7472,16 @@ flow_loops_free (loops)
 	{
 	  struct loop *loop = &loops->array[i];
 
+	  if (loop->pre_header_trace)
+	    sbitmap_free (loop->pre_header_trace);
 	  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);
 	}
       free (loops->array);
       loops->array = NULL;
@@ -7478,7 +7491,8 @@ flow_loops_free (loops)
       if (loops->cfg.dfs_order)
 	free (loops->cfg.dfs_order);
 
-      sbitmap_free (loops->shared_headers);
+      if (loops->shared_headers)
+	sbitmap_free (loops->shared_headers);
     }
 }
 
@@ -7839,6 +7853,36 @@ flow_dfs_compute_reverse_finish (data)
   return;
 }
 
+
+/* Find the root node of the loop pre-header extended basic block and
+   the blocks along the trace from the root node to the loop header.  */
+
+static void
+flow_loop_pre_header_scan (loop)
+     struct loop *loop;
+{
+  basic_block ebb;
+
+  if (loop->num_entries != 1)
+     return;
+
+  /* Find pre_header root note and trace from root node to pre_header.  */
+  loop->pre_header_trace = sbitmap_alloc (n_basic_blocks);
+  sbitmap_zero (loop->pre_header_trace);
+  
+  ebb = loop->entry_edges[0]->src;
+  SET_BIT (loop->pre_header_trace, ebb->index);
+  while (ebb->pred->src != ENTRY_BLOCK_PTR
+	 && ! ebb->pred->pred_next)
+    {
+      ebb = ebb->pred->src;
+      SET_BIT (loop->pre_header_trace, ebb->index);
+    }
+  
+  loop->pre_header_root = ebb;
+}
+
+
 /* 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.  */
@@ -7987,13 +8031,16 @@ flow_loops_level_compute (loops)
   return levels;
 }
 
+
 /* 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.  */
 
 int
-flow_loops_find (loops)
+flow_loops_find (loops, flags)
      struct loops *loops;
+     int flags;
 {
   int i;
   int b;
@@ -8004,32 +8051,38 @@ flow_loops_find (loops)
   int *dfs_order;
   int *rc_order;
 
-  loops->num = 0;
-  loops->array = NULL;
-  loops->tree = NULL;
-  dfs_order = NULL;
-  rc_order = NULL;
+  /* 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 ();
+    
+  memset (loops, 0, sizeof (*loops));
 
   /* Taking care of this degenerate case makes the rest of
      this code simpler.  */
   if (n_basic_blocks == 0)
     return 0;
 
+  dfs_order = NULL;
+  rc_order = NULL;
+
   /* Compute the dominators.  */
   dom = sbitmap_vector_alloc (n_basic_blocks, n_basic_blocks);
   compute_flow_dominators (dom, NULL);
 
   /* Count the number of loop edges (back edges).  This should be the
-     same as the number of natural loops.  Also clear the loop_depth
-     and as we work from inner->outer in a loop nest we call
-     find_loop_nodes_find which will increment loop_depth for nodes
-     within the current loop, which happens to enclose inner loops.  */
+     same as the number of natural loops.  */
 
   num_loops = 0;
   for (b = 0; b < n_basic_blocks; b++)
     {
-      BASIC_BLOCK (b)->loop_depth = 0;
-      for (e = BASIC_BLOCK (b)->pred; e; e = e->pred_next)
+      basic_block header;
+
+      header = BASIC_BLOCK (b);
+      header->loop_depth = 0;
+
+      for (e = header->pred; e; e = e->pred_next)
 	{
 	  basic_block latch = e->src;
 
@@ -8039,6 +8092,9 @@ flow_loops_find (loops)
 	     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 ();
+
 	  if (latch != ENTRY_BLOCK_PTR && TEST_BIT (dom[latch->index], b))
 	    num_loops++;
 	}
@@ -8069,8 +8125,8 @@ flow_loops_find (loops)
 	{
 	  basic_block header;
 
-	  /* Search the nodes of the CFG in DFS order that we can find
-	     outer loops first.  */
+	  /* Search the nodes of the CFG in reverse completion order
+	     so that we can find outer loops first.  */
 	  header = BASIC_BLOCK (rc_order[b]);
 
 	  /* Look for all the possible latch blocks for this header.  */
@@ -8095,46 +8151,75 @@ flow_loops_find (loops)
 		  loop->latch = latch;
 		  loop->num = num_loops;
 
-		  /* Keep track of blocks that are loop headers so
-		     that we can tell which loops should be merged.  */
-		  if (TEST_BIT (headers, header->index))
-		    SET_BIT (loops->shared_headers, header->index);
-		  SET_BIT (headers, header->index);
-
-		  /* Find nodes contained within the loop.  */
-		  loop->nodes = sbitmap_alloc (n_basic_blocks);
-		  loop->num_nodes
-		    = flow_loop_nodes_find (header, 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));
-
-		  /* 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);
-
-		  /* Find edges which exit the loop.  */
-		  loop->num_exits
-		    = flow_loop_exit_edges_find (loop->nodes,
-						 &loop->exit_edges);
-
-		  /* Look to see if the loop has a pre-header node.  */
-		  loop->pre_header = flow_loop_pre_header_find (header, dom);
-
 		  num_loops++;
 		}
 	    }
 	}
 
+      for (i = 0; i < num_loops; i++)
+	{
+	  struct loop *loop = &loops->array[i];
+	  int j;
+
+	  /* 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));
+	  
+	  if (flags & LOOP_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);
+	      
+	      /* Find edges which exit the loop.  */
+	      loop->num_exits
+		= flow_loop_exit_edges_find (loop->nodes,
+					     &loop->exit_edges);
+	      
+	      /* 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,
+				 dom[loop->exit_edges[j]->src->index]);
+	      
+	      /* The header of a natural loop must dominate
+		 all exits.  */
+	      if (! TEST_BIT (loop->exits_doms, loop->header->index))
+		abort ();
+	    }
+	  
+	  if (flags & LOOP_PRE_HEADER)
+	    {
+	      /* Look to see if the loop has a pre-header node.  */
+	      loop->pre_header 
+		= flow_loop_pre_header_find (loop->header, dom);
+
+	      flow_loop_pre_header_scan (loop);
+	    }
+	}
+
       /* 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
@@ -8163,6 +8248,23 @@ flow_loops_find (loops)
   return num_loops;
 }
 
+
+/* Update the information regarding the loops in the CFG
+   specified by LOOPS.  */
+int
+flow_loops_update (loops, flags)
+     struct loops *loops;
+     int flags;
+{
+  /* 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_loops_find (loops, flags);
+}
+
+
 /* Return non-zero if edge E enters header of LOOP from outside of LOOP.  */
 
 int