Fix PR middle-end/86864

[Eric Botcazou]

This is a regression present on the mainline: an assertion is triggered in 
commit_one_edge_insertion at expansion time because a BB contains a BARRIER in 
its BB_END, which is not valid.  expand_gimple_basic_block is supposed to 
prevent that from happening, but it doesn't properly handle the sequence:

  JUMP
  BARRIER
  JUMP_TABLE_DATA
  BARRIER

that can be generated for a switch construct.

Bootstrapped/regtested on x86_64-suse-linux, applied on mainline as obvious.


2018-09-15  Eric Botcazou  <ebotca...@adacore.com>

        PR middle-end/86864
        * cfgexpand.c (expand_gimple_basic_block): Be prepared for a BARRIER
        before and after a JUMP_TABLE_DATA.


2018-09-15  Eric Botcazou  <ebotca...@adacore.com>

        * gcc.c-torture/compile/20180915-1.c: New test.

-- 
Eric Botcazou
Index: cfgexpand.c
===================================================================
--- cfgexpand.c	(revision 264202)
+++ cfgexpand.c	(working copy)
@@ -5810,6 +5810,8 @@ expand_gimple_basic_block (basic_block b
     last = PREV_INSN (last);
   if (JUMP_TABLE_DATA_P (last))
     last = PREV_INSN (PREV_INSN (last));
+  if (BARRIER_P (last))
+    last = PREV_INSN (last);
   BB_END (bb) = last;
 
   update_bb_for_insn (bb);

/* PR middle-end/86864 */
/* Testcase by Serge Belyshev <belys...@depni.sinp.msu.ru> */

long a;
void f ();
void g (int b, int c, int d)
{
  switch (b)
    {
    case 42:
    case 29:
    case 48:
    case 40:
    case 32:
      c = 2;
      break;
    case 0:
      c = 1;
      break;
    default:
      __builtin_unreachable ();
    }
  if (d || a)
    f ();
  if (c == 1)
    f ();
}