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 union5;

union S
{
    T t;
    U u;
    uint i;
    struct {
        ushort sl,sh;
    }
}

struct T
{
    int i;
}

struct U
{
    float f;
}

void main()
{
    S s;
    assert(s.t.i == 0);
    assert(s.u.f == 0);
    s.t.i = -1;
    assert(s.i == 0xFFFF_FFFF);
    float f = 3.1415;
    s.u.f = f;
    uint pi = *cast(uint*)&f;
    assert(s.i == pi);
    assert(s.sl == (pi&0xFFFF));
    assert(s.sh == (pi>>>16));
}