[FFmpeg-cvslog] arm: Detect 32 bit cpu features on ARMv8 when running on a 64 bit kernel
git at videolan.org
Sat Jun 28 21:44:03 CEST 2014
ffmpeg | branch: master | Martin Storsjö <martin at martin.st> | Mon Jun 23 20:49:21 2014 +0300| [7b0c7c9163fe3dd0081696befde28617119d2590] | committer: Martin Storsjö
arm: Detect 32 bit cpu features on ARMv8 when running on a 64 bit kernel
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
The android cpufeatures library does this slightly differently,
by assuming that these are available if the "CPU architecture"
line is >= 8, see  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  for the discussion around this suggestion.
Signed-off-by: Martin Storsjö <martin at martin.st>
libavutil/arm/cpu.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/libavutil/arm/cpu.c b/libavutil/arm/cpu.c
index 85ea662..8bdaa88 100644
@@ -90,8 +90,10 @@ static int get_cpuinfo(uint32_t *hwcap)
*hwcap |= HWCAP_VFP;
if (strstr(buf, " vfpv3 "))
*hwcap |= HWCAP_VFPv3;
- if (strstr(buf, " neon "))
+ if (strstr(buf, " neon ") || strstr(buf, " asimd "))
*hwcap |= HWCAP_NEON;
+ if (strstr(buf, " fp ")) // Listed on 64 bit ARMv8 kernels
+ *hwcap |= HWCAP_VFP | HWCAP_VFPv3;
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