The vector mode was deprecated in ARMv7-A/VFPv3 and various cpu
implementations do not support it in hardware. Vector mode code will
depending the OS either be emulated in software or result in an illegal
instruction on cpus which does not support it. This was not really
problem in practice since NEON implementations of the same functions are
preferred. It will however become a problem for checkasm which tests
every cpu flag separately.
Since this is a cpu feature newer cpu do not support anymore the
behaviour of this flag differs from the other flags. It can be only
activated by runtime cpu feature selection.
When running on a 64 bit kernel, /proc/cpuinfo lists different
optional features than on 32 bit kernels (because some of them
are mandatory in the 64 bit implemenations).
The kernel does list the old features properly if they are queried
via /proc/self/auxv though - however this file is not always readable
(e.g. on most android systems). The getauxval function could also
provide the same info as /proc/self/auxv even if this file isn't
readable, but this function is not always available (and thus would
need to be loaded with dlsym for compatibility with older android
versions).
The android cpufeatures library does this slightly differently,
by assuming that these are available if the "CPU architecture"
line is >= 8, see [1] for details.
It has been suggested to include the old, non-optional features in
/proc/cpuinfo as well, but that suggested patch never was merged.
See [2] for the discussion around this suggestion.
[1] https://android-review.googlesource.com/91380
[2] http://marc.info/?l=linux-arm-kernel&m=139087240101974
Signed-off-by: Martin Storsjö <martin@martin.st>
On recent android versions, /proc/self/auxw is unreadable
(unless the process is running running under the shell uid or
in debuggable mode, which makes it hard to notice). See
http://b.android.com/43055 and
https://android-review.googlesource.com/51271 for more information
about the issue.
This makes sure e.g. neon optimizations are enabled at runtime in
android apps even when built in release mode, if configured to
use the runtime detection.
CC: libav-stable@libav.org
Signed-off-by: Martin Storsjö <martin@martin.st>
This allows compiling optimised functions for features not enabled
in the core build and selecting these at runtime if the system has
the necessary support.
Signed-off-by: Mans Rullgard <mans@mansr.com>
This is consistent with usual ARM nomenclature as well as with the
VFPV3 and NEON symbols which both lack the ARM prefix.
Signed-off-by: Mans Rullgard <mans@mansr.com>
This allows masking CPU features with the -cpuflags avconv option
which is useful for testing different optimisations without rebuilding.
Signed-off-by: Mans Rullgard <mans@mansr.com>
The were broken since August of 2010 without anyone noticing until
three weeks ago. Nobody cares about it anymore and hopefully Marvell
will support NEON like in the PXA978 from now on.
Instead of defining functions in per-arch header files included
by the main cpu.c, define them normally and call them from the
generic one.
Originally committed as revision 25084 to svn://svn.ffmpeg.org/ffmpeg/trunk
Janne Grunau
Martin Storsjö
Diego Biurrun
Mans Rullgard