Remove an old workaround that was kept around for ABI-compatibility on x86-64 between different LLVM versions. This means LLVM r67588 is required if you want to compile for x86-64, otherwise the backend will assert when you try to return e.g. struct { int i; char c; } from a function. (In particular, this is no longer compatible with LLVM 2.5) It also means that any code returning small structs on x86-64 will probably need to be recompiled in order to be linkable to code compiled with this change.

module structs4;

struct S{
    int a;
    T t;
}

struct T{
    int b;
    U u;
}

struct U{
    int c;
}

void main()
{
    S s;
    s.a = 3;
    s.t = T.init;
    s.t.b = 4;
    s.t.u = U.init;
    s.t.u.c = 5;
    //{assert(s.t.u.c == 5);}
}