`reinterpret` to a single value from an array of a smaller data type

[gdkrmr]

If you have a tuple of UInt8’s, the following gets completely optimized out for all Unsigned types:

Type piracy?

I was just toying around with this and found the following weird performance issue (Julia Version 0.7.0-DEV.4570): function f(::Type{UInt16}, x::NTuple{2, UInt8}) x1 = 0x0001 * x[1] x2 = 0x0100 * x[2] x1 + x2 end const NBytes{N} = NTuple{N, UInt8} function f(::Type{UInt16}, x::NBytes{2}) x1 = 0x0001 * x[1] x2 = 0x0100 * x[2] x1 + x2 end julia> @btime f(UInt16, (0x01, 0x02)) 0.017 ns (0 allocations: 0 bytes) 0x0201 julia> x = NBytes((0x01, 0x02)) (0x01, 0x02) julia> …

I haven’t found a no op way to create byte tuples from UIntX.