Re: LuaJIT and SSE2

[Petri Häkkinen <petrih3@...>]

On 17.6.2010, at 21.36, Mike Pall wrote:

> Petri Häkkinen wrote:
>> However, LuaJIT seems to be running like a dog on my older AMD
>> setup which I use primarily for development at home. The CPU
>> does not support SSE2 instructions so I figured this is most
>> likely the culprit.
> 
> If the CPU doesn't have SSE2, the JIT compiler is turned off and
> LuaJIT falls back to the interpreter. You can check this by
> starting the standalone executable without arguments. The 2nd line
> either prints "JIT: ON" or "JIT: OFF".
> 
>> So my question is, what are the chances of getting jit to work
>> on non-SSE2 capable CPUs?
> 
> Well, not without substantial effort. Quoting myself from:
>  http://lua-users.org/lists/lua-l/2010-03/msg00142.html
> 
>  "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."
> 
>> If my chances are slim, I guess I need to visit the nearest PC
>> hardware store...
> 
> Considering the cost of an upgrade, the overall speedup, the option
> to use a 64 bit OS and the availability of hardware virtualization,
> I'd say this is well worth the investment for a developer machine.
> 
> --Mike

Okay, thanks for the speedy and detailed response, Mike. Silly me, I should have checked the archives first.

I agree with you that it would not be wise to spend considerable amount of your time on this. I had a wishful thinking that SSE2 was only used in a couple of places.

So time to upgrade it is.

Petri