[Bug rtl-optimization/63804] [5 Regression] ice in find_oldest_value_reg with -g -O2

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63804

--- Comment #5 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
Please ignore comment 4.

Testcase without implicit functions:

markus@x4 tmp % cat bug169.c
struct brw_context
{
  int gen;
} e;
int a, d;
long b;
enum brw_reg_type
{
  BRW_REGISTER_TYPE_Q
};
struct brw_reg
{
  enum brw_reg_type type : 1;
  int nr : 1;
  struct
  {
    unsigned ud;
  } dw1;
};
enum brw_reg_type c;
void
fn1 (int p1)
{
  b = p1 & a;
}

int fn2 ();
void fn3 ();
void
fn4 (struct brw_reg p1, unsigned p2, int p3)
{
  struct brw_reg f, g, h, j = p1, l, m = l;
  struct brw_context i = e;
  if (i.gen)
    p2 = 0;
  j.type = c;
  g = j;
  p1 = g;
  fn3 ();
  int k = p2, v = p1.nr, p = v;
  m.dw1.ud = k;
  f = m;
  h = f;
  struct brw_reg n = h;
  fn3 (n);
  {
    d = fn2 ();
    int o = d;
    fn1 (o);
  }
  if (i.gen)
    fn3 (p1);
  b = p & a;
  fn3 (p3);
}