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.

class C
{
    int a;
    union
    {
        int i;
        double d;
    }
    int z;
}

void func()
{
    scope c = new C;
    access1(c);
    assert(c.i == 42);
    access2(c);
    assert(c.d == 2.5);
}

void access1(C c)
{
    c.i = 42;
}

void access2(C c)
{
    c.d = 2.5;
}

void main()
{
    func();
}