Devectorize is just a macro that transform certain syntax to loops. Parallelaccelerator is a full fledged compiler doing much more advanced transformations.
Fortunately, as mentioned in the link that @stevengj posted, Julia has gained the ability to devectorize and fuse loops without any external packages at all. As of Julia v0.6, you can just write: a .* b .+ c .* d .+ a and get exactly one loop over the data, just as you would with Devectorize on earlier version of Julia.