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- Subject: Re: Re: NaN packing for TValue
- From: Peter Cawley <lua@...>
- Date: Fri, 25 Feb 2011 13:51:58 +0000
2011/2/24 Yura Sokolov <funny.falcon@gmail.com>:
> Well, x64 at the moment uses only 48 bits for addresses.
>
> 1bit for a sign + 11bits for mantis + 1bit for quiet NaN + 48 bits for an
> address = 61bit
> So that there is 3bits for tagging.
>
> Currently Lua uses 13 different tag values, so that it would be tricky to
> pack them into three bits :)
If you're willing to pay the price of an extra indirection, you might
be able to get away with using a single tag value for all GC types, as
the GC header stores the tag value.
