Sorting precompile.jl (and removing duplicates)


I was looking into changing precompile.jl so that it displayed some sort of indication that it was actually working, and also whether by sorting, the parts being precompiled could be displayed when there are large numbers of methods being precompiled in the same module (such as Core.Compile.*).
When I sorted the precompile lines, I noticed that there were a number of duplicates.
What happens when precompile() is called on a method that has already been precompiled?
Does it spend the same amount of time, or does it exit early seeing that it had already been precompiled?