PR tree-optimization/18815

       * tree-if-conv.c (combine_blocks): Adjust loop header edges for
       loops with zero exit edges.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@95923 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 16 insertions, 3 deletions

diff --git a/gcc/tree-if-conv.c b/gcc/tree-if-conv.c
index bb832d24616..ef9dc574ce1 100644
--- a/gcc/tree-if-conv.c
+++ b/gcc/tree-if-conv.c
@@ -858,7 +858,8 @@ combine_blocks (struct loop *loop)
   basic_block bb, exit_bb, merge_target_bb;
   unsigned int orig_loop_num_nodes = loop->num_nodes;
   unsigned int i;
-
+  unsigned int n_exits;
+  edge *exits = get_loop_exit_edges (loop, &n_exits);
   /* Process phi nodes to prepare blocks for merge.  */
   process_phi_nodes (loop);
 
@@ -905,11 +906,23 @@ combine_blocks (struct loop *loop)
 	continue;
 
       /* It is time to remove this basic block.	 First remove edges.  */
-      while (EDGE_COUNT (bb->succs) > 0)
-	remove_edge (EDGE_SUCC (bb, 0));
       while (EDGE_COUNT (bb->preds) > 0)
 	remove_edge (EDGE_PRED (bb, 0));
 
+      /* This is loop latch and loop does not have exit then do not
+ 	 delete this basic block. Just remove its PREDS and reconnect 
+ 	 loop->header and loop->latch blocks.  */
+      if (bb == loop->latch && n_exits == 0)
+ 	{
+	  exits = NULL; /* To suppress unused warning.  */
+ 	  make_edge (loop->header, loop->latch, EDGE_FALLTHRU);
+ 	  set_immediate_dominator (CDI_DOMINATORS, loop->latch, loop->header);
+	  continue;
+ 	}
+
+      while (EDGE_COUNT (bb->succs) > 0)
+	remove_edge (EDGE_SUCC (bb, 0));
+
       /* Remove labels and make stmts member of loop->header.  */
       for (bsi = bsi_start (bb); !bsi_end_p (bsi); )
 	{