On Mon, 19 Jan 2015, Niels Möller wrote:
Nikos Mavrogiannopoulos <[email protected]> writes:
It's early, but it would be nice if the arm neon code was part of fat as well.
I've pushed a start for fat binary support on arm.
Unfortunately I don't have much opinion on the other things you mentioned
in your mail, but I did have a brief look at the arm feature detection.
I see you're looking at the CPU architecture field as well. There's a big
gotcha related to that one; some ARMv6 CPUs report CPU architecture: 7.
See http://code.google.com/p/android/issues/detail?id=10812 and
https://android.googlesource.com/platform/ndk/+/13a99c7f/sources/android/cpufeatures/cpu-features.c
(lines 716-737) for more details about this. (Unfortunately I don't have
any better pointers to the kernel source/discussions for an explanation of
this.)
For example a raspberry pi has got the following /proc/cpuinfo:
processor : 0
model name : ARMv6-compatible processor rev 7 (v6l)
Features : swp half thumb fastmult vfp edsp java tls
CPU implementer : 0x41
CPU architecture: 7
CPU variant : 0x0
CPU part : 0xb76
CPU revision : 7
Hardware : BCM2708
Revision : 0002
Serial : 00000000d605188c
If you only need to decide whether to enable ARMv6 specific instructions,
it should be just fine, but in case you'd use it for enabling ARMv7 stuff
as well, you'd need some sort of workaround for this.
// Martin
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