[Bug tree-optimization/86611] missing -Warray-bounds on a large negative index into a string in lp64

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86611

--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
Ditto for the following (distilled from gcc.dg/Warray-bounds-31.c:

void f (int);

void g (void)
{
  const char *q = "12345678" + 4;
  __PTRDIFF_TYPE__ i = __PTRDIFF_MAX__ - 3;
  f (q[i]);
}