RE: disabled JIT compiler for cpu with no sse2 support

["Anton Kukura" <lua@...>]

Well, that's what I was afraid of. 

I was looking forward to use JIT on embedded system (AMD Geode LX800). Many
current embedded solutions have CPUs with not SSE support (I believe that
number 99% is misleading and it includes only commercial, industrial and
games computers).
LuaJIT boots scripting performance very well on embedded systems, it is
needed due to CPU speed limitations. It is just too bad we have to stick
with version 1.x.

May be others will join me and would vote to keep x87 as a back up for those
systems.

Mike, once Lua 5.2 is officially released would you consider to update
LuaJIT 1.x to Lua 5.2?

Thanks,
Anton


, as many other embedded cpu do not suport sse instructions

Well, I was looking for using JIT on embedded system. 

-----Original Message-----
From: lua-bounces@bazar2.conectiva.com.br
[mailto:lua-bounces@bazar2.conectiva.com.br] On Behalf Of Mike Pall
Sent: Thursday, March 04, 2010 4:38 PM
To: Lua list
Subject: Re: disabled JIT compiler for cpu with no sse2 support

Anton Kukura wrote:
> I was under impression that LuaJIT generates x87 instructions for cpu 
> with no sse support.

Umm, LuaJIT 2.0 never JIT compiled to x87 code (LuaJIT 1.x did).

The interpreter uses x87 (still the default on x86) or SSE2 (optional on
x86, default on x64).

> Unfortunately, the latest git mirror, does not allow to turn JIT 
> engine on for cpu without sse2 support.

That's correct. It disables the JIT compiler and falls back to the
interpreter. Previously it simply refused to run at all on a
non-SSE2 CPU. I'd say that's an improvement.

> Mike, do you plan to work on it in near future? 

Not anymore. The number of machines out there without SSE2 is rapidly
shrinking. I'm not sure it's a good investment of my time to add x87 code
generation to the backend. It would be rather difficult to integrate into
the current design and/or won't perform well, too.

Arguably the Steam hardware survey is biased by their audience:

  http://store.steampowered.com/hwsurvey

But still ... scroll to the bottom, click on "Other Settings" and you'll see
that 98.20% of their users have SSE2. By the time I'd be finished, it'll be
at 99% ...


[BTW: barring unforseen difficulties, beta3 will be out tomorrow (including
x64 support). Anyone testing git HEAD please speak up now, if you find any
issues on any platform. Thank you!]

--Mike