re PR middle-end/64083 (ICE: in fix_loop_structure, at loop-init.c:252 compiling Linux Kernel)

2014-11-27  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/64083
	* tree-ssa-threadupdate.c (thread_through_all_blocks): Do not
	forcibly mark loop for removal the wrong way.

	* gcc.dg/torture/pr64083.c: New testcase.

From-SVN: r218115

gcc/ChangeLog

 2014-11-27  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/64083
+	* tree-ssa-threadupdate.c (thread_through_all_blocks): Do not
+	forcibly mark loop for removal the wrong way.
+
+2014-11-27  Richard Biener  <rguenther@suse.de>
+
 	PR middle-end/63704
 	* alias.c (mems_in_disjoint_alias_sets_p): Remove assert
 	and instead return false when !fstrict-aliasing.

gcc/testsuite/ChangeLog

 2014-11-27  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/64083
+	* gcc.dg/torture/pr64083.c: New testcase.
+
+2014-11-27  Richard Biener  <rguenther@suse.de>
+
 	PR tree-optimization/61634
 	* gcc.dg/vect/pr61634.c: New testcase.
 

gcc/testsuite/gcc.dg/torture/pr64083.c

+/* { dg-do compile } */
+
+int a, b;
+void
+fn1 ()
+{
+  int c = 0;
+  while (b)
+    {
+      switch (c)
+    case 1:
+	fn1 ();
+	if (a)
+	  c = 1;
+	b = 0;
+    }
+}

gcc/tree-ssa-threadupdate.c

@@ -2428,16 +2428,8 @@ thread_through_all_blocks (bool may_peel_loop_headers)
 		/* Our path is still valid, thread it.  */
 	        if (e->aux)
 		  {
-		    struct loop *loop = (*path)[0]->e->dest->loop_father;
-
 		    if (thread_block ((*path)[0]->e->dest, false))
-		      {
-			/* This jump thread likely totally scrambled this loop.
-			   So arrange for it to be fixed up.  */
-			loop->header = NULL;
-			loop->latch = NULL;
 		      e->aux = NULL;
-		      }
 		    else
 		      {
 		        delete_jump_thread_path (path);