Re: [Discuss-gnuradio] Volk: Am I getting all that's available for ARM?

[Marcus Müller]

I was just a little confused, because I read the volk/gen/archs.xml 
template, and figured if
has_neon() returned true, -mfloat_abi=soft and -nfpu=neon would have 
been added to the C_FLAGS...
and cmake's output contained "Performing Test have_mfloat_abi_softfp - 
Failed", so I guessed that (since I was quite sure that your machine 
supports softfp) it was disabled by lack of compiler flags...

Thanks for your comprehensive answer and for finding my mistakes (the 
sed slipped in there because I was stripping the leading offsets and 
whitespaces...)!

Greetings,
Marcus

Monahan-Mitchell, Tim:
> Hi, Marcus.
>
> Thanks for your help. Tom seems to have given a pretty definitive reply, but 
> this is just to completely answer your reply.
>
> > On 08/07/2013 02:44 AM, Marcus Müller wrote:
> > > [1] note: in kernel terms of auxvec.h this stands for AT_HWCAP, see 
> > > http://lxr.free-electrons.com/source/include/uapi/linux/auxvec.h?a=arm#L24
> > > How Volk handles it looks like AT_HWCAP can only start on a 4-byte-aligned 
> > > address within auxv;
> > > I'm absolutely not sure whether this is correct; on my x86_64 machine, there is 
> > > no AT_HWCAP in that case.
> > decided to have a look into this instead of sleeping; man proc(5) and volk are 
> > right: AT_HWCAP can only occur every 64 bit in /proc/PID/auxv. Sorry for the 
> > confusion.
> Your earlier reply said:
>
> <snip> "... however, as it seems, detection of Neon fails."
>
> But the cmake output I included said:
>
> -- Performing Test have_mfpu_neon - Success
> -- Performing Test have_funsafe_math_optimizations - Success
>
> So I think the neon detection works?
>
> You also asked: "does executing
>     hexdump /proc/self/auxv|sed '0000 0010'
> show anything?"
>
> Yes, an error :) ... Maybe you meant grep? The first line of auxv matches to 
> your string:
>
> $ hexdump /proc/self/auxv
> 0000000 0010 0000 b0d7 0001 0006 0000 1000 0000
> 0000010 0011 0000 0064 0000 0003 0000 8034 0000
> 0000020 0004 0000 0020 0000 0005 0000 0009 0000
> 0000030 0007 0000 c000 4002 0008 0000 0000 0000
> 0000040 0009 0000 8f35 0000 000b 0000 0000 0000
> 0000050 000c 0000 0000 0000 000d 0000 0000 0000
> 0000060 000e 0000 0000 0000 0017 0000 0000 0000
> 0000070 0019 0000 dc07 bed4 001f 0000 dfeb bed4
> 0000080 000f 0000 dc17 bed4 0000 0000 0000 0000
> 0000090
>
> And if I run the basic "cmake ../" command, I still get the same output for 
> Volk.
>
> You asked for the CFLAGS in CMakeCache.txt in that s case, here you go:
>
> // CMAKE_C_FLAGS used) Debug Release RelWithDebInfo MinSizeRel.
> CMAKE_C_FLAGS:STRING=
> CMAKE_C_FLAGS_DEBUG:STRING=-g
> CMAKE_C_FLAGS_MINSIZEREL:STRING=-Os -DNDEBUG
> CMAKE_C_FLAGS_RELEASE:STRING=-O3 -DNDEBUG
> CMAKE_C_FLAGS_RELWITHDEBINFO:STRING=-O2 -g -DNDEBUG
> //ADVANCED property for variable: CMAKE_C_FLAGS
> CMAKE_C_FLAGS-ADVANCED:INTERNAL=1
> //ADVANCED property for variable: CMAKE_C_FLAGS_DEBUG
> CMAKE_C_FLAGS_DEBUG-ADVANCED:INTERNAL=1
> //ADVANCED property for variable: CMAKE_C_FLAGS_MINSIZEREL
> CMAKE_C_FLAGS_MINSIZEREL-ADVANCED:INTERNAL=1
> //ADVANCED property for variable: CMAKE_C_FLAGS_RELEASE
> CMAKE_C_FLAGS_RELEASE-ADVANCED:INTERNAL=1
> //ADVANCED property for variable: CMAKE_C_FLAGS_RELWITHDEBINFO
> CMAKE_C_FLAGS_RELWITHDEBINFO-ADVANCED:INTERNAL=1
>
> Just to compare, running my original cmake command yields the CFLAGS I manually 
> specified:
>
> grep C_FLAGS CMakeCache.txt
> // CMAKE_C_FLAGS used) Debug Release RelWithDebInfo MinSizeRel.
> CMAKE_C_FLAGS:STRING=-I/usr/include/arm-linux-gnueabihf -mcpu=cortex-a15 
> -mfpu=neon -mvectorize-with-neon-quad -ffast-math -funsafe-loop-optimizations
> CMAKE_C_FLAGS_DEBUG:STRING=-g
> CMAKE_C_FLAGS_MINSIZEREL:STRING=-Os -DNDEBUG
> CMAKE_C_FLAGS_RELEASE:STRING=-O3 -DNDEBUG
> CMAKE_C_FLAGS_RELWITHDEBINFO:STRING=-O2 -g -DNDEBUG
> //ADVANCED property for variable: CMAKE_C_FLAGS
> CMAKE_C_FLAGS-ADVANCED:INTERNAL=1
> //ADVANCED property for variable: CMAKE_C_FLAGS_DEBUG
> CMAKE_C_FLAGS_DEBUG-ADVANCED:INTERNAL=1
> //ADVANCED property for variable: CMAKE_C_FLAGS_MINSIZEREL
> CMAKE_C_FLAGS_MINSIZEREL-ADVANCED:INTERNAL=1
> //ADVANCED property for variable: CMAKE_C_FLAGS_RELEASE
> CMAKE_C_FLAGS_RELEASE-ADVANCED:INTERNAL=1
> //ADVANCED property for variable: CMAKE_C_FLAGS_RELWITHDEBINFO
> CMAKE_C_FLAGS_RELWITHDEBINFO-ADVANCED:INTERNAL=1
>
> Thanks again and all the best,
> Tim