Thanks! Very helpful.
No, there is no need in multiplatform support in one build. Register pairs
don't need to be ordered.
--Evgeny
On Monday, August 13, 2012 5:10:30 PM UTC+7, Vyacheslav Egorov wrote:
>
> Here is another possibility: in low level IR explode double values
> into pairs of low-level values.
>
> d2 = Mul d0, d1
>
> becomes smth like
>
> (i20, i21) = Mul (i00, i01), (i10, i11)
>
> that would require a minor change in the pipeline to allow multiple
> return values but I think it might be less painful than supporting
> register pairs across the pipeline.
>
> --
> Vyacheslav Egorov
>
>
> On Mon, Aug 13, 2012 at 11:34 AM, Vyacheslav Egorov
> <veg...@chromium.org <javascript:>> wrote:
> > Are you planning to allocate a couple of general purpose registers to
> > represent a double? Do these registers have to be ordered? (e.g. do
> > you need r_{N}, r_{N+1})
> >
> > Do you want a single build of V8 work both on a hardware that supports
> > real double registers and that does not?
> >
> > If you don't need binary portability then I don't think you need to
> > extend unallocated policies. Just change "interpretation" of
> > DOUBLE_REGISTER policy everywhere.
> >
> > Otherwise, yeah, you need new policies (which would require some bit
> > stealing cause LUnallocated is packed pretty tight already).
> >
> > In any case it would require some adjustments in allocator to get
> > "what interferes with what" right.
> >
> > --
> > Vyacheslav Egorov
> >
> >
> > On Mon, Aug 13, 2012 at 7:53 AM, Evgeny Baskakov
> > <evgeny....@gmail.com <javascript:>> wrote:
> >> Hi guys,
> >>
> >> I'm looking for ways to modify the Crankshaft compilation mode to make
> it
> >> work without 64-bit hardware registers.
> >>
> >> Could someone give me brief guidelines? Is it possible at all, without
> the
> >> whole V8 codebase reworking?
> >>
> >> My first impulse is to extend the LUnallocated policies set and make
> the
> >> codegen distinguish between single and coupled registers. Then, the
> lithium
> >> codegen would use the CPU-based code stubs instead of native
> double-related
> >> instructions. What pitfalls should I be aware of here?
> >>
> >> --Evgeny
> >>
> >> --
> >> v8-users mailing list
> >> v8-u...@googlegroups.com <javascript:>
> >> http://groups.google.com/group/v8-users
>
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