nexus 7 simd neon-- i thought it was supported?

[K-man]

Hi All,

I have a Nexus 7, and wanted to start getting into the SIMD programming.  I know that the Nexus 7 has a Tegra 3 chipset inside it, and according to WIkipedia, Tegra 3 supports the NEON instruction set?

I have the following line of code in my program, and it always prints out... suggesting that my Nexus 7 tablet doesn't support NEON?

features = android_getCpuFeatures();

if ((features & ANDROID_CPU_ARM_FEATURE_NEON) == 0) {

__android_log_print(ANDROID_LOG_DEBUG, "VMUL", "cpu doesnt support neon! -- ???");

}

I'm confused?  Was there an older version of the nexus 7's that didn't support NEON or something?

Thanks in advance

[David Turner]

It is actually supported by the Nexus 7, and many other Android devices (but not all). It's a regression in the cpufeatures library that was introduced recently (really sorry about this, unit testing didn't catch it because the problem doesn't always happen). You can see here for the fix in AOSP (you should be able to download the new source file  by clicking the "Download" icon).

 

Thanks in advance

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[K-man]

Hi David,

Thanks for the quick response.  Ok... so pardon my ignorance.  What would I do with this patch?  Do I have to build the whole Android OS and then install that new update onto my Tablet (i.e. root, flash, etc etc...?)  Are there other options?

pardon my ignorance, and thanks again!

[Dan V.]

The file to patch is $NDK/sources/android/cpufeatures/cpu-features.c

[K-man]

Oh.. that makes sense.  Pardon the dumb question :*(     I have to patch the NDK builder.. got it!

Thanks again!

[David Turner]

On Thu, Feb 7, 2013 at 2:43 AM, K-man <kiran...@gmail.com> wrote:

Hi David,

Thanks for the quick response.  Ok... so pardon my ignorance.  What would I do with this patch?  Do I have to build the whole Android OS and then install that new update onto my Tablet (i.e. root, flash, etc etc...?)  Are there other options?

Just copy the new version of the file over the one in your $NDK/sources/android/cpufeatures/cpu-features.c, and rebuild your project with ndk-build.