[Bug middle-end/59711] ICE in force_constant_size, at gimplify.c:619 with variably-modified return type

[fweimer at redhat dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59711

--- Comment #6 from Florian Weimer <fweimer at redhat dot com> ---
Created attachment 31772
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=31772&action=edit
pr59711.adb

Here's the same thing in Ada (where it actually works—it's actually fairly
idiomatic code, I believe).  The generated GIMPLE looks like this (with GCC
4.8.2 from Fedora):

PR59711 (const natural___XDLU_0__2147483647 n)
{
  integer n.3;
  sizetype D.2600;
  bitsizetype D.2601;
  bitsizetype D.2602;
  struct pr59711__s * R.4;
  character D.2604;
  void * saved_stack.5;
  natural___XDLU_0__2147483647 pr59711__s__T1b___U;
  typedef pr59711__s__T1b___XDL_1 pr59711__s__T1b___XDL_1;
  typedef signed long struct signed long;
  typedef character pr59711__s__T2b[1:D.2600];
  typedef struct pr59711__s pr59711__s;
  struct pr59711__s R.0 [value-expr: *R.4];

  saved_stack.5 = .builtin_stack_save ();
  try
    {
      pr59711__s__T1b___U = n;
      n.3 = (integer) n;
      n.3 = (integer) n;
      D.2600 = (sizetype) n.3;
      n.3 = (integer) n;
      D.2600 = (sizetype) n.3;
      D.2601 = (bitsizetype) D.2600;
      D.2602 = D.2601 * 8;
      n.3 = (integer) n;
      D.2600 = (sizetype) n.3;
      n.3 = (integer) n;
      D.2600 = (sizetype) n.3;
      D.2601 = (bitsizetype) D.2600;
      D.2602 = D.2601 * 8;
      n.3 = (integer) n;
      D.2600 = (sizetype) n.3;
      n.3 = (integer) n;
      D.2600 = (sizetype) n.3;
      D.2601 = (bitsizetype) D.2600;
      D.2602 = D.2601 * 8;
      n.3 = (integer) n;
      D.2600 = (sizetype) n.3;
      n.3 = (integer) n;
      D.2600 = (sizetype) n.3;
      D.2601 = (bitsizetype) D.2600;
      D.2602 = D.2601 * 8;
      n.3 = (integer) n;
      D.2600 = (sizetype) n.3;
      R.4 = .builtin_alloca_with_align (D.2600, 8);
      *R.4 = pr59711.f (); [return slot optimization]
      D.2604 = R.4->a[1]{lb: 1 sz: 1};
      return D.2604;
    }
  finally
    {
      .builtin_stack_restore (saved_stack.5);
    }
}