[ubsan] Call c_fully_fold on SAVE_EXPRs

[Marek Polacek]

With ubsan, we ICEd in gimplify_expr e.g. on the following testcase

typedef volatile int VI;

int
foo (void)
{
  VI vi = 100;
  return 2 << ++vi;
}

because c_save_expr created c_maybe_const_expr which then leaked into
gimplification, oops.  Fixed by calling c_fully_fold on second argument;
I'm calling it on the first one too, because it seems safer, but from
my testing it almost seemed that it isn't actually needed, since we didn't
ICEd e.g. with
  return ++vi << 2;

Ok for ubsan branch?

2013-07-20  Marek Polacek  <pola...@redhat.com>

        * c-typeck.c (build_binary_op): Call c_fully_fold on both
        SAVE_EXPRs.

--- gcc/c/c-typeck.c.mp3        2013-07-20 20:28:36.841214356 +0200
+++ gcc/c/c-typeck.c    2013-07-20 20:29:36.646445839 +0200
@@ -10493,6 +10493,8 @@ build_binary_op (location_t location, en
       /* OP0 and/or OP1 might have side-effects.  */
       op0 = c_save_expr (op0);
       op1 = c_save_expr (op1);
+      op0 = c_fully_fold (op0, false, NULL);
+      op1 = c_fully_fold (op1, false, NULL);
       if (doing_div_or_mod)
        instrument_expr = ubsan_instrument_division (location, op0, op1);
       else if (doing_shift)

        Marek