TREE_ADDRESSABLE types cause ICE in declare_return_variable

[Johannes Pfau]

Hi,

the gdc D compiler currently doesn't implement "non-POD" types. As in C++ those
types can have copy constructors or destructors and should be kept in memory.
Right now I just set TREE_ADDRESSABLE on the RECORD_TYPE tree and it's mostly
working. Some test cases fail though if optimization / inlining is enabled:

D code like this:
------
Appender appender() { return Appender(""); }

void main() {
    Appender w = appender();
    auto x = &w;
}
------
where Appender is a non-POD type causes an assertion failure in
declare_return_variable: "gcc_assert (!TREE_ADDRESSABLE (callee_type));"

There's a comment saying "All types requiring non-trivial constructors should
have been handled." but where and how? The problem only occurs if the address of
w is taken, as this will mark w as addressable. Then 
gimple_call_return_slot_opt_p test in expand_call_inline fails and return_slot
is not set. If the address of w is not taken the return_slot is used and
everything works fine.

-fdump-tree-original dump:
------
;; Function appender (_D6format8appenderFZS6format8Appender)
;; enabled by -tree-original
{
  struct Appender __ctmp5;
  return <retval> = *format.Appender.this (&((void) (__ctmp5 = {});, __ctmp5),
    {.length=0, .ptr=""});
}

;; Function main (_Dmain)
;; enabled by -tree-original
{
  struct Appender * x;
  struct Appender w;
  (void) (w = format.appender ());
  (void) (x = &w);
  return <retval> = 0;
}
------


Thanks,

Johannes