re PR middle-end/54520 (ice in merge_latch_edges with -O3)

2012-09-10  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/54520
	* tree-ssa-threadupdate.c (def_split_header_continue_p):
	Properly consider sub-loops.

	* gcc.dg/torture/pr54520.c: New testcase.

From-SVN: r191141

gcc/ChangeLog

+2012-09-10  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/54520
+	* tree-ssa-threadupdate.c (def_split_header_continue_p):
+	Properly consider sub-loops.
+
 2012-09-10  Richard Henderson  <rth@redhat.com>
 
 	* config/alpha/predicates.md (small_symbolic_operand): Disallow

gcc/testsuite/ChangeLog

+2012-09-10  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/54520
+	* gcc.dg/torture/pr54520.c: New testcase.
+
 2012-09-10  Jason Merrill  <jason@redhat.com>
 
 	PR c++/54506

gcc/testsuite/gcc.dg/torture/pr54520.c

+/* { dg-do compile } */
+
+char *a;
+void
+fn1 ()
+{
+  char *p = a;
+  while (p && *p != '\0')
+    {
+      while (*p == '\t')
+	*p++ = '\0';
+      if (*p != '\0')
+	p = 0;
+    }
+}

gcc/tree-ssa-threadupdate.c

@@ -846,8 +846,9 @@ static bool
 def_split_header_continue_p (const_basic_block bb, const void *data)
 {
   const_basic_block new_header = (const_basic_block) data;
-  return (bb->loop_father == new_header->loop_father
-	  && bb != new_header);
+  return (bb != new_header
+	  && (loop_depth (bb->loop_father)
+	      >= loop_depth (new_header->loop_father)));
 }
 
 /* Thread jumps through the header of LOOP.  Returns true if cfg changes.
@@ -1031,10 +1032,11 @@ thread_through_loop_header (struct loop *loop, bool may_peel_loop_headers)
       nblocks = dfs_enumerate_from (header, 0, def_split_header_continue_p,
 				    bblocks, loop->num_nodes, tgt_bb);
       for (i = 0; i < nblocks; i++)
-	{
-	  remove_bb_from_loops (bblocks[i]);
-	  add_bb_to_loop (bblocks[i], loop_outer (loop));
-	}
+	if (bblocks[i]->loop_father == loop)
+	  {
+	    remove_bb_from_loops (bblocks[i]);
+	    add_bb_to_loop (bblocks[i], loop_outer (loop));
+	  }
       free (bblocks);
 
       /* If the new header has multiple latches mark it so.  */