problem with isbitstype usage after union-splitting optim

[vtjnash]

OrderedCollections.jl/src/ordered_dict.jl

Lines 136 to 149 in 1ca4dd3

	ptrs = !isbitstype(K)
	to = 1
	# TODO: to get the best performance we need to avoid reallocating these.
	# This algorithm actually works in place, unless the dict is modified
	# due to GC during this process.
	newkeys = similar(keys, count0)
	newvals = similar(vals, count0)
	@inbounds for from = 1:length(keys)
	if !ptrs || isassigned(keys, from)
	k = keys[from]
	hashk = hash(k)%Int
	isdeleted = false
	if !ptrs
	iter = 0

The first check (!ptrs || isassigned(keys, from)) can be just isassigned(keys, from) (these should be the same, since isbits arrays are always assigned)

The second check should now use Base.isbitsunion (and perhaps isassigned(values, from) too as an optimization)

[fingolfin]

The code now uses isbitsunion but not quite in the way described here. But it seems to work anyway.