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



The ball-park number you have probably won't change much.


Unfortunately, that is the configuration I can use on my system because
of lack of libraries for other configurations.

Using --with-fpu={neon / neon-vfpv4} shouldn't cause you ABI issues with libraries for any other configurations. neon / neon-vfpv4 enable use of the neon unit in a manner that is ABI compatible with the rest of the system.

For more on command line options for AArch32 and how they map to various CPU's you might find this blog interesting.

http://community.arm.com/groups/tools/blog/2013/04/15/arm-cortex-a-processors-and-gcc-command-lines


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.

Also given it's a big LITTLE system with probably kernel switching - it may be better to also make sure that you are always running on the big core.


As I wrote, I am more interesting in aarch64 which can be used in a
server (as you know RedHat works on a server market) but unfortunately I
have no such machine for SPEC benchmarking.


Ramana






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