Re: JIT-friendly version of unpack()
- From: Craig Barnes <craigbarnes85@xxxxxxxxx>
- To: luajit@xxxxxxxxxxxxx
- Date: Tue, 16 Sep 2014 14:01:43 +0100
On 16 September 2014 13:00, Roman Tsisyk <roman@xxxxxxxxxxxxx> wrote:
> 2. Specialized versions for particular sizes - do compile, but looks ugly
>
> local function unpack3(t)
> if #t == 1 then
> return t[1]
> else if #t == 2 then
> return t[1], t[2]
> else if #t == 3 then
> return t[1], t[2], t[3]
> else
> return unpack(t) -- goodbye, JIT
> end
> end
It doesn't have to be that ugly. The following is more or less equivalent:
local function unpack3(t)
if #t <= 3 then
return t[1], t[2], t[3]
else
return unpack(t)
end
end
You could also make an unpack5 without any extra redundant branches or
length operators and only a little extra code.
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