2012-04-03 Richard Guenther <rguenther@suse.de>

	PR tree-optimization/52808
	* tracer.c (tail_duplicate): Return whether we have duplicated
	any block.
	(tracer): If we have duplicated any block, cleanup the CFG.
	* cfghooks.c (duplicate_block): If we duplicated a loop
	header but not its loop, destroy the loop because it now has
	multiple entries.
	* tree-ssa-threadupdate.c (thread_through_loop_header): Tell
	the cfg manipulation routines we are not creating a multiple
	entry loop.

	* gcc.dg/pr52808.c: New testcase.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@186104 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 19 insertions, 9 deletions

diff --git a/gcc/cfghooks.c b/gcc/cfghooks.c
index 1dca79a70cf..bc1b7a2f582 100644
--- a/gcc/cfghooks.c
+++ b/gcc/cfghooks.c
@@ -1009,18 +1009,28 @@ duplicate_block (basic_block bb, edge e, basic_block after)
     {
       struct loop *cloop = bb->loop_father;
       struct loop *copy = get_loop_copy (cloop);
-      add_bb_to_loop (new_bb, copy ? copy : cloop);
-      /* If we copied the loop latch block but not the loop, adjust
-	 loop state.
-	 ???  If we copied the loop header block but not the loop
-	 we might either have created a loop copy or a loop with
-	 multiple entries.  In both cases we probably have to
-	 ditch the loops and arrange for a fixup.  */
+      /* If we copied the loop header block but not the loop
+	 we have created a loop with multiple entries.  Ditch the loop,
+	 add the new block to the outer loop and arrange for a fixup.  */
       if (!copy
-	  && cloop->latch == bb)
+	  && cloop->header == bb)
 	{
+	  add_bb_to_loop (new_bb, loop_outer (cloop));
+	  cloop->header = NULL;
 	  cloop->latch = NULL;
-	  loops_state_set (LOOPS_MAY_HAVE_MULTIPLE_LATCHES);
+	  loops_state_set (LOOPS_NEED_FIXUP);
+	}
+      else
+	{
+	  add_bb_to_loop (new_bb, copy ? copy : cloop);
+	  /* If we copied the loop latch block but not the loop, adjust
+	     loop state.  */
+	  if (!copy
+	      && cloop->latch == bb)
+	    {
+	      cloop->latch = NULL;
+	      loops_state_set (LOOPS_MAY_HAVE_MULTIPLE_LATCHES);
+	    }
 	}
     }