re PR tree-optimization/71881 (ICE on valid code at -O3 with -g enabled on…

re PR tree-optimization/71881 (ICE on valid code at -O3 with -g enabled on x86_64-linux-gnu: cannot update SSA form)

2016-07-15  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/71881
	* tree-loop-distribution.c (destroy_loop): Remove blocks in
	reverse DOM order to make debug temp generation happy.

	* gcc.dg/torture/pr71881.c: New testcase.

From-SVN: r238374

gcc/ChangeLog

 2016-07-15  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/71881
+	* tree-loop-distribution.c (destroy_loop): Remove blocks in
+	reverse DOM order to make debug temp generation happy.
+
+2016-07-15  Richard Biener  <rguenther@suse.de>
+
 	PR tree-optimization/71887
 	* tree-ssa-phiopt.c (absorbing_element_p): Add rhs arg and
 	verify it is not zero for division / modulo handling.

gcc/testsuite/ChangeLog

 2016-07-15  Richard Biener  <rguenther@suse.de>
 
+	PR tree-optimization/71881
+	* gcc.dg/torture/pr71881.c: New testcase.
+
+2016-07-15  Richard Biener  <rguenther@suse.de>
+
 	PR tree-optimization/71887
 	* gcc.dg/torture/pr71887.c: New testcase.
 

gcc/testsuite/gcc.dg/torture/pr71881.c

+/* { dg-do compile } */
+/* { dg-additional-options "-g" } */
+
+int a, b, c, d, *e, f, g;
+
+int fn1 ()
+{
+  char h[2];
+  int i = 0;
+  for (; i < 2; i++)
+    {
+      if (c)
+	for (*e = 0; *e;)
+	  {
+	    int j[f];
+	    i = *e;
+	  }
+      h[i] = 0;
+    }
+  for (; a;)
+    return h[0];
+  for (b = 0; b;)
+    i = g = (1 & i) < d;
+  return 0;
+}

gcc/tree-loop-distribution.c

@@ -888,13 +888,15 @@ destroy_loop (struct loop *loop)
   cancel_loop_tree (loop);
   rescan_loop_exit (exit, false, true);
 
-  for (i = 0; i < nbbs; i++)
+  i = nbbs;
+  do
     {
       /* We have made sure to not leave any dangling uses of SSA
          names defined in the loop.  With the exception of virtuals.
 	 Make sure we replace all uses of virtual defs that will remain
 	 outside of the loop with the bare symbol as delete_basic_block
 	 will release them.  */
+      --i;
       for (gphi_iterator gsi = gsi_start_phis (bbs[i]); !gsi_end_p (gsi);
 	   gsi_next (&gsi))
 	{
@@ -912,6 +914,8 @@ destroy_loop (struct loop *loop)
 	}
       delete_basic_block (bbs[i]);
     }
+  while (i != 0);
+
   free (bbs);
 
   set_immediate_dominator (CDI_DOMINATORS, dest,