re PR debug/66688 (compare debug failure building Linux kernel on ppc64le)

	PR tree-optimization/66688
	* tree-cfgcleanup.c (cleanup_control_flow_bb): Handle
	noreturn call followed only by debug stmts by removing
	the debug stmts and handling it the same as if the noreturn
	call is the last stmt.

	* gcc.dg/pr66688.c: New test.

From-SVN: r231644

gcc/ChangeLog

+2015-12-15  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/66688
+	* tree-cfgcleanup.c (cleanup_control_flow_bb): Handle
+	noreturn call followed only by debug stmts by removing
+	the debug stmts and handling it the same as if the noreturn
+	call is the last stmt.
+
 2015-12-14  Steve Ellcey  <sellcey@imgtec.com>
 
 	* config/mips/mips.c (mips_promote_function_mode): New function.

gcc/testsuite/ChangeLog

+2015-12-15  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/66688
+	* gcc.dg/pr66688.c: New test.
+
 2015-12-15  Patrick Palka  <ppalka@gcc.gnu.org>
 
 	PR c++/21802

gcc/testsuite/gcc.dg/pr66688.c

+/* PR tree-optimization/66688 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fno-reorder-blocks -fcompare-debug" } */
+
+struct fdt_header { unsigned magic; } *a;
+
+int d;
+
+int
+__fswab32 (int p1)
+{
+  return __builtin_bswap32 (p1);
+}
+
+void
+fdt_set_magic (int p1)
+{
+  struct fdt_header *b = a;
+  b->magic = __builtin_constant_p (p1) ? : __fswab32 (p1);
+}
+
+int
+_fdt_sw_check_header ()
+{
+  int c = ((struct fdt_header *) 1)->magic;
+  if (c)
+    return 1;
+  return 0;
+}
+
+int
+fdt_finish ()
+{
+  if (_fdt_sw_check_header ())
+    if (d)
+      return 0;
+  fdt_set_magic (0);
+  return 0;
+}

gcc/tree-cfgcleanup.c

@@ -186,7 +186,7 @@ cleanup_control_flow_bb (basic_block bb)
      we need to prune cfg.  */
   retval |= gimple_purge_dead_eh_edges (bb);
 
-  gsi = gsi_last_bb (bb);
+  gsi = gsi_last_nondebug_bb (bb);
   if (gsi_end_p (gsi))
     return retval;
 
@@ -197,7 +197,10 @@ cleanup_control_flow_bb (basic_block bb)
 
   if (gimple_code (stmt) == GIMPLE_COND
       || gimple_code (stmt) == GIMPLE_SWITCH)
+    {
+      gcc_checking_assert (gsi_stmt (gsi_last_bb (bb)) == stmt);
       retval |= cleanup_control_expr_graph (bb, gsi);
+    }
   else if (gimple_code (stmt) == GIMPLE_GOTO
 	   && TREE_CODE (gimple_goto_dest (stmt)) == ADDR_EXPR
 	   && (TREE_CODE (TREE_OPERAND (gimple_goto_dest (stmt), 0))
@@ -210,6 +213,7 @@ cleanup_control_flow_bb (basic_block bb)
       edge_iterator ei;
       basic_block target_block;
 
+      gcc_checking_assert (gsi_stmt (gsi_last_bb (bb)) == stmt);
       /* First look at all the outgoing edges.  Delete any outgoing
 	 edges which do not go to the right block.  For the one
 	 edge which goes to the right block, fix up its flags.  */
@@ -242,9 +246,15 @@ cleanup_control_flow_bb (basic_block bb)
   /* Check for indirect calls that have been turned into
      noreturn calls.  */
   else if (is_gimple_call (stmt)
-           && gimple_call_noreturn_p (stmt)
-           && remove_fallthru_edge (bb->succs))
+	   && gimple_call_noreturn_p (stmt))
+    {
+      /* If there are debug stmts after the noreturn call, remove them
+	 now, they should be all unreachable anyway.  */
+      for (gsi_next (&gsi); !gsi_end_p (gsi); )
+	gsi_remove (&gsi, true);
+      if (remove_fallthru_edge (bb->succs))
 	retval = true;
+    }
 
   return retval;
 }