unroll.jl

unroll(f, ::Val{1}) = f()
function unroll(f, ::Val{N}) where N
    f(); unroll(f, Val(N-1))
end
function test()
    box = Ref(1.0) # explicitely box to make escape analysis easier
    unroll(()-> box[] += sin(box[]), Val(3))
    box[]
end

# as you can see, the box will get eliminated on julia 0.7!
julia> @code_llvm test()
define double @julia_test_33284() #0 {
top:
  %0 = call double @julia_sin_33229(double 1.000000e+00)
  %1 = fadd double %0, 1.000000e+00
  %2 = call double @julia_sin_33229(double %1)
  %3 = fadd double %1, %2
  %4 = call double @julia_sin_33229(double %3)
  %5 = fadd double %3, %4
  ret double %5
}