[Bug middle-end/35545] virtual call specialization not happening with FDO

[hubicka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=35545

--- Comment #12 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
We still fail to fold here.  After tracer we get:
  # ap_2 = PHI <ap_8(4)>
  # prephitmp_14 = PHI <&MEM[(void *)&_ZTV1A + 16B](4)>
  _19 = *prephitmp_14;
  PROF_24 = [obj_type_ref] OBJ_TYPE_REF(_19;(struct A)ap_2->0);
  if (PROF_24 == foo)
    goto <bb 9>;
  else
    goto <bb 8>;

and the necessary forward propagation & folding to realize that:
  _19 = foo;
  PROF_24 = [obj_type_ref] OBJ_TYPE_REF(_19;(struct A)ap_8->0);
  if (PROF_24 == foo)

happens only in .optimized dump.

I would go with patch from comment 5 moving tracer earlier - the tail
duplication intends to make code more optimizable and it is stupid to run it
only after all optimizations are done.