Julia: how to see devectorized code? - julia

Question

I would like to see devectorized code of some expression say here
obj.mask = exp.(1.0im*lambda*obj.dt/2.);
How one could print a generic expression in devectorized form in Julia?

Answer 1

I don't think that what you ask for exists (please proof me wrong if I'm mistaken!).
The best you can do is use #code_lowered, #code_typed, #code_llvm, #code_native macros (in particular #code_lowered) to see what happens to your Julia code snippet. However, as Julia isn't translating all dots to explicit for loops internally, non of these snippets will show you a for-loop version of your code.
Example:
julia> a,b = rand(3), rand(3);
julia> f(a,b) = a.*b
f (generic function with 1 method)
julia> #code_lowered f(a,b)
CodeInfo(
1 1 ─ %1 = Base.Broadcast.materialize │
│ %2 = Base.Broadcast.broadcasted │
│ %3 = (%2)(Main.:*, a, b) │
│ %4 = (%1)(%3) │
└── return %4 │
)
So, Julia translates the .* into a Base.Broadcast.broadcasted call. Of course, we can go further and do
julia> #which Base.Broadcast.broadcasted(Main.:*, a, b)
broadcasted(f, arg1, arg2, args...) in Base.Broadcast at broadcast.jl:1139
and check broadcast.jl in line 1139 and so on to trace the actual broadcasted method that will be called (maybe Tim Holy's Rebugger is useful here :D). But as I said before, there won't be a for-loop in it. Instead you will find something like this:
broadcasted(::DefaultArrayStyle{1}, ::typeof(*), r::AbstractRange, x::Number) = range(first(r)*x, step=step(r)*x, length=length(r))
broadcasted(::DefaultArrayStyle{1}, ::typeof(*), r::StepRangeLen{T}, x::Number) where {T} =
StepRangeLen{typeof(T(r.ref)*x)}(r.ref*x, r.step*x, length(r), r.offset)
broadcasted(::DefaultArrayStyle{1}, ::typeof(*), r::LinRange, x::Number) = LinRange(r.start * x, r.stop * x, r.len)
Update
Ok, eventually, I found for-loops in copyto! in broadcast.jl. But this is probably to deep into the rabbit hole.