Fwd: Would you send me your hard float experiment results you presented in Budapest?

[David Rusling]

I'm a little confused.  There's two comparisons to be made. 

The comparison between vfp enabled in all cases, comparing using the
soft float ABI with using the hard float ABI means that you'll identify
the effect of moving VFP registers in and out of integer registers to
make function call (soft float ABI) versus using them directly (hard
float ABI).

The comparision of using VFP at all versus only using integer emulation
of floating point is separate and different.

Both have an effect, the effects manifest themselves differently.

Dave

On Wed, 2011-09-07 at 16:33 -0500, Rob Clark wrote:
> On Fri, Sep 2, 2011 at 1:27 PM, Christian Robottom Reis <kiko at linaro.org> wrote:
> > On Tue, Aug 30, 2011 at 11:24:59AM -0500, Zach Pfeffer wrote:
> >> I'd like you to meet Jim who did the initial hardfloat work. This
> >> email contains the results that Jim produced.
> >
> > Hmm, but the email seems to not actually contain a hard-float run. Or am
> > I misreading what he means by Fixed vs VFP?
> >
> >> I believe that the conclusion was that skia and webkit may benefit,
> >> but that such benefits would impose an undue burden on Android's
> >> distribution model which tries to create libs that can run on as many
> >> architectures as possible.
> >
> > You may be confusing things here. Hard-float is a pure software ABI
> > change, and any platform which supports VFP can use it if you build it
> > that way. However, since it is an ABI change it requires that hard-float
> > libraries be available.
> >
> > What /would/ stop code from running on certain platforms is using
> > NEON (it would exclude the Tegra2 and some existing Marvell v7s). But
> > that doesn't seem to be in question here.
> 
> Fwiw, VFP and NEON share same registers.. so as long as Tegra2 has
> VFP, I think it could use hard-float.  Are we supporting any armv7-a
> that doesn't have at least VFP?
> 
> Although I'm a bit lost on this topic, are we comparing
> non-hard-float-but-vfp-enabled (ie. fp op's not falling back to sw) vs
> hard-float?  Or soft-float vs hard-float?
> 
> BR,
> -R
> 
> >> ---------- Forwarded message ----------
> >> From: Jim Huang <jserv at 0xlab.org>
> >> Date: 7 August 2011 18:01
> >> Subject: Re: Would you send me your hard float experiment results you
> >> presented in Budapest?
> >> To: Zach Pfeffer <zach.pfeffer at linaro.org>
> >>
> >>
> >> 2011/8/7 Zach Pfeffer <zach.pfeffer at linaro.org>:
> >> > Jim,
> >> >
> >> > Thanks. Would it be possible to post them by the end of the day?
> >>
> >> skia ->
> >>
> >>    Switch from VFP back to fixed scalar based calculation
> >>
> >>    Previous configuration enabled ARM VFP for scalar float, but VFP on
> >>    ARM11 is not as powerful as VFPv3 or NEON.
> >>
> >>    Reference benchmark:
> >>    Item            Fixed based     VFP-based
> >>    ------------    -----------     ---------
> >>    Draw Canvas     58.37 fps       58.40 fps
> >>    Draw Circle     37.48 fps       22.93 fps
> >>    Draw Circle2    17.14 fps       18.31 fps
> >>    Draw Rect       17.62 fps       20.69 fps
> >>    Draw Arc        24.79 fps       27.45 fps
> >>    Draw Image      19.08 fps       18.73 fps
> >>    Draw Text       29.22 fps       25.79 fps
> >>
> >>
> >> >
> >> > Also, have you sync'd up with Mike? He wants to negotiate on your contract.
> >>
> >> I sent mail to Mike already.  I don't know how to proceed.
> >>
> >> Thanks,
> >> -jserv
> >
> >
> >
> >> _______________________________________________
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> >> linaro-dev at lists.linaro.org
> >> http://lists.linaro.org/mailman/listinfo/linaro-dev
> >
> > --
> > Christian Robottom Reis, Engineering VP
> > Brazil (GMT-3) | [+55] 16 9112 6430 | [+1] 612 216 4935
> > Linaro.org: Open Source Software for ARM SoCs
> >
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> >
> 
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-- 
David Rusling, CTO

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