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

6 files changed, 65 insertions, 17 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 7c1d1b3bb20..74a5a184811 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,16 @@
+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.
+
 2012-04-03  Tristan Gingold  <gingold@adacore.com>
 
 	* config/vms/vms-c.c (vms_pragma_nomember_alignment): Handle
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);
+	    }
 	}
     }
 
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 7fe8a18ca0f..c757d42d177 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2012-04-03  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/52808
+	* gcc.dg/pr52808.c: New testcase.
+
 2012-04-03  Jakub Jelinek  <jakub@redhat.com>
 
 	PR tree-optimization/52835
diff --git a/gcc/testsuite/gcc.dg/pr52808.c b/gcc/testsuite/gcc.dg/pr52808.c
new file mode 100644
index 00000000000..b731cb40133
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr52808.c
@@ -0,0 +1,12 @@
+/* { dg-do compile } */
+/* { dg-options "-O -ftracer" } */
+
+int **fn1 () __attribute__ ((__const__));
+int main ()
+{
+  int i;
+  i = 0;
+  for (;; i++)
+    if (*fn1 ()[i] && !'a' <= 0 && i <= 'z' || *fn1 ()[0] && 'a' <= 'z')
+      return;
+}
diff --git a/gcc/tracer.c b/gcc/tracer.c
index 602e7580d99..8fb9817dbe9 100644
--- a/gcc/tracer.c
+++ b/gcc/tracer.c
@@ -59,7 +59,6 @@ static bool better_p (const_edge, const_edge);
 static edge find_best_successor (basic_block);
 static edge find_best_predecessor (basic_block);
 static int find_trace (basic_block, basic_block *);
-static void tail_duplicate (void);
 
 /* Minimal outgoing edge probability considered for superblock formation.  */
 static int probability_cutoff;
@@ -224,7 +223,7 @@ find_trace (basic_block bb, basic_block *trace)
 /* Look for basic blocks in frequency order, construct traces and tail duplicate
    if profitable.  */
 
-static void
+static bool
 tail_duplicate (void)
 {
   fibnode_t *blocks = XCNEWVEC (fibnode_t, last_basic_block);
@@ -236,6 +235,7 @@ tail_duplicate (void)
   gcov_type cover_insns;
   int max_dup_insns;
   basic_block bb;
+  bool changed = false;
 
   /* Create an oversized sbitmap to reduce the chance that we need to
      resize it.  */
@@ -332,6 +332,7 @@ tail_duplicate (void)
 			 bb2->index, copy->index, copy->frequency);
 
 	      bb2 = copy;
+	      changed = true;
 	    }
 	  mark_bb_seen (bb2);
 	  bb = bb2;
@@ -353,6 +354,8 @@ tail_duplicate (void)
   free (trace);
   free (counts);
   fibheap_delete (heap);
+
+  return changed;
 }
 
 /* Main entry point to this file.  */
@@ -360,6 +363,8 @@ tail_duplicate (void)
 static unsigned int
 tracer (void)
 {
+  bool changed;
+
   gcc_assert (current_ir_type () == IR_GIMPLE);
 
   if (n_basic_blocks <= NUM_FIXED_BLOCKS + 1)
@@ -370,15 +375,14 @@ tracer (void)
     dump_flow_info (dump_file, dump_flags);
 
   /* Trace formation is done on the fly inside tail_duplicate */
-  tail_duplicate ();
+  changed = tail_duplicate ();
+  if (changed)
+    free_dominance_info (CDI_DOMINATORS);
 
-  /* FIXME: We really only need to do this when we know tail duplication
-            has altered the CFG. */
-  free_dominance_info (CDI_DOMINATORS);
   if (dump_file)
     dump_flow_info (dump_file, dump_flags);
 
-  return 0;
+  return changed ? TODO_cleanup_cfg : 0;
 }
 
 static bool
diff --git a/gcc/tree-ssa-threadupdate.c b/gcc/tree-ssa-threadupdate.c
index 000bd3f2e40..687eee0485a 100644
--- a/gcc/tree-ssa-threadupdate.c
+++ b/gcc/tree-ssa-threadupdate.c
@@ -1004,8 +1004,12 @@ thread_through_loop_header (struct loop *loop, bool may_peel_loop_headers)
       basic_block *bblocks;
       unsigned nblocks, i;
 
-      /* First handle the case latch edge is redirected.  */
+      /* First handle the case latch edge is redirected.  We are copying
+         the loop header but not creating a multiple entry loop.  Make the
+	 cfg manipulation code aware of that fact.  */
+      set_loop_copy (loop, loop);
       loop->latch = thread_single_edge (latch);
+      set_loop_copy (loop, NULL);
       gcc_assert (single_succ (loop->latch) == tgt_bb);
       loop->header = tgt_bb;