Re: Possible GSoC idea: MIPS N32 ABI Port
On Fri, Mar 1, 2013 at 3:10 PM, Aaro Koskinen <aaro.koskinen@iki.fi> wrote:
> Hi,
>
> On Fri, Mar 01, 2013 at 11:01:20AM -0800, Matt Turner wrote:
>> Besides questionable usefulness, since the hardware is sort of obsoleted
>> by new Loongson 3A hardware, the actual work to do involves getting code
>> upstream that Lemote was too lazy to upstream.
>
> What code are you referring to?
The things I know about are:
- handling NaN cases for Loongson-specific floating-point
instructions in the kernel FPU emulator. There are some patches, but
they need to go through review and a bit of clean up.
- Making the X server work on 2F. Lemote (or someone?) wrote patches,
but they're awful hacks not suitable for upstream. Real work needs to
happen here.
- There are patches for the siliconmotion DDX that use MMI to speed
up YUV colorspace conversion. This code should really be in pixman,
with the X server using that.
I've spent /some/ time on each of these.
> BTW, what are the practical benefits of this effort, especially on
> Loongson 2F HW? (Any performance figures?)
Not having to apply hacky patches the kernel and X server to have a
usable system seems like an intrinsic benefit to me.
As far as performance goes, maybe you could find something to optimize
with the MMI instructions like I did for pixman [1]. I'm not sure what
though.
I think MIPS (the company) contributed a MIPS-backend to Firefox's
JavaScript JIT compiler but only for o32. Updating it, or perhaps
contributing a new one, for N32/N64 might make a nice project. It
would certainly improve the Firefox user experience on Loongson. That
would be useful for Loongson 2F, 3A, and any other hardware that's
n32-capable.
[1] http://mattst88.com/blog/2012/05/17/Optimizing_pixman_for_Loongson:_Process_and_Results/
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