5 ms·

300% faster float point ops on ARM Linux

27 points by iqster 15y ago

wccrawford 15y ago
lol I love the confusion of the interviewer. Props to this guy (and his team-mates) for taking on such a project and seeing it through. I'm sure there was a lot of detractors saying things like 'It won't matter enough" and "Recompiling everything is going fragment the ARM repositories and it's not worth it."
nitrogen 15y ago
So they changed the default value of -mfloat-abi or a similar compiler flag? Or is there something more significant here?
- lucian1900 15y ago
  Mostly yes. Then, the fixed all the bugs that particular compiler flag exposed. Then, they compiled new repos.
batterseapower 15y ago
Basically what is going on here is that the system is recompiled to pass floating point numbers in the ARM VFP registers, rather than the integer registers. This both reduces register pressure and means you don't have to marshal stuff to and from the integer registers at function boundaries. The reason this hasn't happened before is because VFP is an optional part of the instruction set, and you can still configure compliant ARM cores without a FPU. I'm not sure if their port uses NEON (the ARM SSE equivalent) at all.
- zdw 15y ago
  Haven't watched the video, but I'm wondering if this hack is available to other projects/build systems. OpenEmbedded/Angstrom would be ideal targets.
- sc68cal 15y ago
  Wow. That was far more informative than the Engadget summary. Maybe you can take Dante Cesa's job?
deleted 15y ago
[deleted]
malkia 15y ago
I have Efika MX. SmartBook, and SmartTop. I started reading the Genesi forum - www.PowerDeveloper.org, and there was mentioning of hardfp arm version. Maybe that's what they are talking about. Btw, I'm very satisfied with the genesi products - OpenGL ES 2.0 works just fine, with some little bugs, but overall very cool and I think cheap system (Ubuntu 10.10, and they are working toward Ubuntu 11.04). LuaJIT works also there (and jits), giving 4-5 speedup over standard lua (It would be better, once LuaJIT too starts using hard floats, it's still relying on software math libs)

27 points by iqster 15y ago

lol I love the confusion of the interviewer. Props to this guy (and his team-mates) for taking on such a project and seeing it through. I'm sure there was a lot of detractors saying things like 'It won't matter enough" and "Recompiling everything is going fragment the ARM repositories and it's not worth it."

nitrogen 15y ago

So they changed the default value of -mfloat-abi or a similar compiler flag? Or is there something more significant here?

lucian1900 15y ago
Mostly yes. Then, the fixed all the bugs that particular compiler flag exposed. Then, they compiled new repos.

batterseapower 15y ago

Basically what is going on here is that the system is recompiled to pass floating point numbers in the ARM VFP registers, rather than the integer registers. This both reduces register pressure and means you don't have to marshal stuff to and from the integer registers at function boundaries. The reason this hasn't happened before is because VFP is an optional part of the instruction set, and you can still configure compliant ARM cores without a FPU. I'm not sure if their port uses NEON (the ARM SSE equivalent) at all.

zdw 15y ago
Haven't watched the video, but I'm wondering if this hack is available to other projects/build systems. OpenEmbedded/Angstrom would be ideal targets.
sc68cal 15y ago
Wow. That was far more informative than the Engadget summary. Maybe you can take Dante Cesa's job?

deleted 15y ago

[deleted]

malkia 15y ago

I have Efika MX. SmartBook, and SmartTop. I started reading the Genesi forum - www.PowerDeveloper.org, and there was mentioning of hardfp arm version. Maybe that's what they are talking about. Btw, I'm very satisfied with the genesi products - OpenGL ES 2.0 works just fine, with some little bugs, but overall very cool and I think cheap system (Ubuntu 10.10, and they are working toward Ubuntu 11.04). LuaJIT works also there (and jits), giving 4-5 speedup over standard lua (It would be better, once LuaJIT too starts using hard floats, it's still relying on software math libs)