Potential performance issue

[Dibyendu Majumdar]

Hi Dave,

I have not yet had the time to try out replacing union with struct to
check performance. Hope to do this soon. But I did try another change
and was somewhat surprised by the result.

As you know currently I take the address of a Lua stack value and then
use the pointer to manipulate the value. This is hangover from the
LLVM port as there it has to be a pointer. But in the libgccjit world,
we actually do not need the pointer unless the pointer needs to be
passed to a function. So most of the time we can just work off the
value array directly.

That is instead of:

(&base[1])->value.tt_

I can just use
base[1]->value.tt_

I was hoping that this might help performance somewhat as presumably a
pointer (going by your change to get_address) may not be optimisable.
To my surprise however the performance dropped by half after the
change. So of course I have not committed this change.

This is just an FYI as I don't intend to investigate this right now (I
have saved the changes so that I can look at this at some time in the
future).

Regards
Dibyendu