Re: Comparison of GCC-4.9 and LLVM-3.4 performance on SPECInt2000 for x86-64 and ARM

[Vladimir Makarov <vmakarov at redhat dot com>]

On 2014-06-24, 10:57 AM, Ramana Radhakrishnan wrote:
> The ball-park number you have probably won't change much.
>
> > I don't think Neon can improve score for SPECInt2000 significantly but
> > may be I am wrong.
>
> It won't probably improve the overall score by a large amount but some
> individual benchmarks will get some help.
>
> > > Did you add any other architecture specific options to your SPEC2k
> > > runs ?
> > No.  The only options I used are -Ofast.
> >
> > Could you recommend me what best options you think I should use for this
> > processor.
>
> I would personally use --with-cpu=cortex-a15 --with-fpu=neon-vfpv4
> --with-float=hard on this processor as that maps with the processor
> available on that particular piece of Silicon.

I've tried this options too.  As I guessed it resulted in GCC 
improvement of eon only by 6% which improved overall score by less 0.5%. 
 No change for LLVM though.  Eon is more fp benchmark with my point of 
view and it should be in SPECFP but it is a different story.

I've tried GCC SPECFP2000 also with and without this options and it gave 
about 12% improvement (1006 vs 988).  That is a *huge* improvement.  I 
guess using NEON for ARM is really important for fp benchmarks.