re PR tree-optimization/58343 (ICE in dfs_enumerate_from, at cfganal.c:1036)

	PR tree-optimization/58343
	* tree-ssa-threadupdate.c (thread_block): Identify and disable
	jump threading requests through loop headers buried in the middle
	of a jump threading path.

	* tree-ssa-threadedge.c (thread_around_empty_blocks): Fix thinko
	in return value/type.

	* gcc.c-torture/compile/pr58343.c: New test.

From-SVN: r202441

gcc/ChangeLog

+2013-09-10  Jeff Law  <law@redhat.com>
+
+	PR tree-optimization/58343
+	* tree-ssa-threadupdate.c (thread_block): Identify and disable
+	jump threading requests through loop headers buried in the middle
+	of a jump threading path.
+
+	* tree-ssa-threadedge.c (thread_around_empty_blocks): Fix thinko
+	in return value/type.
+
 2013-09-10  Jakub Jelinek  <jakub@redhat.com>
 
 	PR rtl-optimization/58365

gcc/testsuite/ChangeLog

+2013-09-10  Jeff Law  <law@redhat.com>
+
+	* gcc.c-torture/compile/pr58343.c: New test.
+
 2013-09-10  Jakub Jelinek  <jakub@redhat.com>
 
 	PR rtl-optimization/58365

gcc/testsuite/gcc.c-torture/compile/pr58343.c

+int a;
+
+int main ()
+{
+  int b = a; 
+
+  for (a = 1; a > 0; a--)
+    ;
+
+ lbl:
+  if (b && a)
+    goto lbl; 
+
+  return 0;
+}

gcc/tree-ssa-threadedge.c

@@ -764,7 +764,7 @@ thread_around_empty_blocks (edge taken_edge,
      when threading.  Thus they can not have visible side effects such
      as PHI nodes.  */
   if (!gsi_end_p (gsi_start_phis (bb)))
-    return NULL;
+    return false;
 
   /* Skip over DEBUG statements at the start of the block.  */
   gsi = gsi_start_nondebug_bb (bb);

gcc/tree-ssa-threadupdate.c

@@ -640,14 +640,36 @@ thread_block (basic_block bb, bool noloop_only)
       else
 	e2 = THREAD_TARGET (e);
 
-      if (!e2
+      if (!e2 || noloop_only)
+	{
 	  /* If NOLOOP_ONLY is true, we only allow threading through the
-	     header of a loop to exit edges.  */
-	  || (noloop_only
-	      && bb == bb->loop_father->header
+	     header of a loop to exit edges. 
+
+	     There are two cases to consider.  The first when BB is the
+	     loop header.  We will attempt to thread this elsewhere, so
+	     we can just continue here.  */
+
+	  if (bb == bb->loop_father->header
 	      && (!loop_exit_edge_p (bb->loop_father, e2)
-		  || THREAD_TARGET2 (e))))
-	continue;
+		  || THREAD_TARGET2 (e)))
+	    continue;
+
+
+	  /* The second occurs when there was loop header buried in a jump
+	     threading path.  We do not try and thread this elsewhere, so
+	     just cancel the jump threading request by clearing the AUX
+	     field now.  */
+	  if (bb->loop_father != e2->src->loop_father
+	      && !loop_exit_edge_p (e2->src->loop_father, e2))
+	    {
+	      /* Since this case is not handled by our special code
+		 to thread through a loop header, we must explicitly
+		 cancel the threading request here.  */
+	      free (e->aux);
+	      e->aux = NULL;
+	      continue;
+	    }
+	}
 
       if (e->dest == e2->src)
 	update_bb_profile_for_threading (e->dest, EDGE_FREQUENCY (e),