Union of Return

[wsmoses]

The generated sret variable by julia doens't actually have sret marked on the LLVM function, leading to issues.

The sret condition needs to be replaced with something more robust.

cc @vtjnash

using Enzyme

function meta(a, out, cond)
    if cond
        out[] = a
    end
end

out = Ref(0.0)
dout = Ref(1.0)
@show Enzyme.autodiff(meta, Active(2.0), Duplicated(out, dout), true)