Open Bug 1289569 Opened 3 years ago Updated Last year

Require NEON support for ARM builds

Categories

(Firefox Build System :: General, defect)

ARM
Unspecified
defect
Not set

Tracking

(Not tracked)

People

(Reporter: lsalzman, Unassigned)

References

Details

Skia upstream has removed support for runtime detection of NEON on ARM. While it might be feasible to hack runtime detection back in, it will probably not be perfect and lose some performance relative to previous Skia versions.

This puts us in a similar situation to where we were with Skia and SSE2 support which we resolved by finally just requiring SSE2 in our builds.

Is it reasonable to just start building NEON support in now for us as well?
I don't know that it is. The NVIDIA Tegra 2 is notorious for shipping without Neon. Devices were shipped as recently as Q2 2012. A very rough search on crash stats returns 14k results for crashes on Android 15+ and the word Tegra [1]. Some of these are later Tegra 3+ SOC which have Neon support. We should look at Play data and/or add a probe to understand scope. If we go the probe route we should make sure that the probe only measures ARM devices as we support Intel Android as well.

A listing of affected devices can be found at http://pdadb.net/index.php?m=pdamaster in the "Processor" section any of the Nvidia Tegra 2 processors are affected. ~100 devices. 

[1] https://crash-stats.mozilla.com/search/?product=FennecAndroid&adapter_device_id=Tegra&android_version=%21%3D13&android_version=%21%3D14&android_version=%21%3D12&android_version=%21%3D11&android_version=%21%3D10&android_version=%21%3D9&_sort=-date&_facets=signature&_columns=date&_columns=signature&_columns=product&_columns=version&_columns=build_id&_columns=platform#crash-reports
In the most recent random telemetry sample, about 0.6% reported no neon - basically, anybody that was ARMv6 or better was reporting neon.  Kevin, does that fit with your numbers above?
Depends on: 1344906
Just a note for those who find this - it's still possible to build Firefox Android without Neon support with some minor hackery, since skia still support build time neon disabling:

https://github.com/wryun/firefox-ics-tegra2/releases
By the way, shouldn't this bug be closed now, since runtime detection is no longer supported (and neither is buildtime without patching)?
Product: Core → Firefox Build System
See Also: → 1515602
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