android neon detection busticated

Bug #911860 reported by Tom Gall
8
This bug affects 1 person
Affects Status Importance Assigned to Milestone
libjpeg-turbo
Triaged
Undecided
Tom Gall

Bug Description

hwcap.h and link.h appears to be both missing from Android ICS.

The old NEON detection is fragile.

We need a newer and more reliable method of detecting if NEON is available for use on Android.

Tom Gall (tom-gall)
Changed in libjpeg-turbo:
assignee: nobody → Tom Gall (tom-gall)
milestone: none → 1.1.90-2012.01
status: New → Triaged
Revision history for this message
Dave Martin (dave-martin-arm) wrote :

Just a quick comment based on what I see in http://bazaar.launchpad.net/~ubuntu-branches/ubuntu/precise/libjpeg-turbo/precise/view/3/simd/jsimd_arm.c:

Yes, the current code looks a bit dodgy... you'll need to open /proc/self/auxv instead of trying to find the auxv data by scanning from envp.

Except in native assembler programs which do not use a C library, there's no guarantee that the auxv data will be present at the end of the environment since the C library may have overwritten or moved the initial environment block since the process started. AFAIK, libc doesn't provide any API for getting at the auxv data, so reading /proc/self/auxv or /proc/cpuinfo is the only option (and /proc/self/auxv has a more fixed, easier-to-parse format)

Revision history for this message
Walter (wdoekes) wrote :

However, /proc/self/auxv isn't always available for reading.

See: https://bugs.launchpad.net/ubuntu/+source/virtualbox/+bug/1014487

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