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 mini.atomic1;

pragma(intrinsic, "llvm.atomic.swap.i#.p0i#")
    T atomic_swap(T)(T* ptr, T val);

void main()
{
    int i = 42;
    int j = atomic_swap(&i, 43);
    assert(j == 42);
    assert(i == 43);
}