Re: Raspberry Pi and Lua

[Mike Pall <mikelu-1203@...>]

David Given wrote:
> So all the floating point operations are done in software? The FPU is
> not used anywhere? (I was under the impression that it did use VFP at
> least to some extent.)

LuaJIT/ARM is currently a pure soft-float port.

There are actually three popular variants out there:
* Soft-float EABI + soft-float library calls (armel)
* Soft-float EABI + VFP (armel option, less efficient)
* Hard-float EABI + VFP (armhf)

Obviously a future ARM/VFP port of LuaJIT ought to support both of
the EABI variants.

> And are intra-Lua calls done using the standard C ABI? Most JITs I've
> met don't; they use custom ABIs internally, and only translate to the
> external ABI for interoperation with C.

It's a trace compiler. There are no intra-Lua calls. At least not
by any standard definition. :-)

So, yes, it doesn't need to conform to any particular calling
convention. And it passes around everything in registers as far as
possible, of course.

--Mike