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

[Monahan-Mitchell, Tim]

Hi, Marcus

> On 08/07/2013 09:48 PM, Monahan-Mitchell, Tim wrote:
>> Because of the 'abi_softfp' test failing on my x86, I decided I did not need 
>> to re-build the ARM tool chain to support soft ABI to try and help Volk. Is 
>> that still correct? (I have been able to build and run gnuradio without the 
>> soft flag just fine).
> I don't think -mfloat_abi=softfp (or even =soft) applies to x86; I think I 
> remember the equivalent flag being something along the ways of 
> -msoft-float... Or am I misunderstanding you and you talk about 
> cross-compiling on x86 for arm?

In my volk travels to answer this email thread's question, I was comparing what 
cmake did on my x86 (where there is more volk support) to what cmake does on my 
ARM target. I noted that both had "-- Performing Test have_mfloat_abi_softfp - 
Failed", hence my conclusion that softfp was not a requirement for volk.

<snip>

> If the selected floating-point hardware includes the NEON extension (e.g. 
> -mfpu='neon'), note that floating-point operations are not generated by GCC's 
> auto-vectorization pass unless -funsafe-math-optimizations is also specified. 
> This is because NEON hardware does not fully implement the IEEE 754 standard 
> for floating-point arithmetic (in particular denormal values are treated as 
> zero), so the use of NEON instructions may lead to a loss of precision.

> So it might make sense to include -funsafe-math-optimizations, if 
> vectorize-with-neon-quad does not do that implicitly.

Yes, I have -funsafe-math-optimizations and the cmake test for it passes: " 
Performing Test have_funsafe_math_optimizations - Success"

Thanks,
Tim