LoopVectorization: Best way to have a multi and single threaded version?

General Usage
,
1

Sometimes when I use LoopVectorization, I want to have both a single and multi-threaded variant of the function available. For instance:

using LoopVectorization

function add!(out, x, y; thread)
    if thread
        add_multi_thread!(out, x, y)
    else
        add_single_thread!(out, x, y)
    end
end

function add_single_thread!(out, x, y)
    @turbo thread=false for i in eachindex(out, x, y)
        out[i] = x[i] + y[i]
    end
    out
end

function add_multi_thread!(out, x, y)
    @turbo thread=true for i in eachindex(out, x, y)
        out[i] = x[i] + y[i]
    end
    out
end

x = randn(10)
y = randn(10)
out1 = randn(10)
out2 = randn(10)
add!(out1, x, y, thread=true)
add!(out2, x, y, thread=false)
@assert out1 ≈ out2

What is a good way to reduce code duplication here? Should I use@eval? What if I also want to control the number of threads at runtime, would I need to use @generated?