For info Google v8 Javascript uses the bottom bit to tag pointers. One problem with this mechanism though is that the pointers can only be used directly with unscaled offset memory access instructions (LDUR/STUR). So in particular, no LDP/STP.

On 28 April 2016 at 22:41, Wookey <wookey@wookware.org> wrote:

+++ Adhemerval Zanella [2016-04-28 12:07 -0300]:
> I do not think this issue is inherent to all JIT implements, but rather to
> luajit with its NaN-tagging scheme [1] which packs different types of objects
> in a 8-byte.

Other jits use the same/similar schemes (mozilla's ionmonkey is one
AIUI). Not sure how many others do this, or how many JITs do it a
different way. BUt it is certainly wider than just luajit.

Wookey
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