Re: Reproducible floating point arithmetic in LuaJIT 2

[Mike Pall <mikelu-0911@...>]

Erik Lindroos wrote:
> [BTW: That still doesn't solve the various issues with the x87
> > transcendental functions or with pow().]
> 
> Yes, I will replace them with fdlibm derivatives.

Be careful about spilled registers when calling C functions. I've
already added generic C call handling for compiled code, so you
may want to wait for the next developer snapshot or the next beta
before adding this.

> Ah, I considered this, but DISPATCH isn't available in lj_vm_foldarith,
> right?
> Although, lj_vm_foldarith doesn't need to be very fast anyway.

Yes, it's not available there and yes, performance of this
function is not relevant.

> > But IMHO the better solution is to (optionally) use SSE2 in the
> > interpreter, too. The intersection of the set of people who still
> > have an x87-only box and the set of people who really need
> > reproducible FP arithmetic is probably empty.
> 
> I agree it's almost not worth the bother, but I'd like to keep things as
> portable as possible unless it's a large effort.

Well, I'll need this for the x64 port, anyway. And only a dozen
lines need to be changed (ignoring the transcendental functions).

--Mike