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


On 24 June 2014 15:11, Vladimir Makarov <vmakarov@redhat.com> wrote:
>   A few people asked me about new performance comparison of latest GCC
> and LLVM.  So I've finished it and put it on my site
>
> http://vmakarov.fedorapeople.org/spec/
>
>   The comparison is achievable from 2014 link and links under it in
> the left frame.

Hi Vladimir,

Nice comparison!

It's on the same ballpark of my own findings (with SPEC and other
benchmarks) on ARM: +10% performance, but also code size for GCC over
LLVM, and massive compilation time savings on LLVM.

I wonder how much of that is due to auto-vectorization (on LLVM, -O2+
turns it on, I suppose GCC is only on -O3?). From Ramana's point,
there may be nothing serious if you haven't enabled NEON, though.

Also interesting to see the impact of LTO being a major drive in
recent performance improvements on both compilers.

cheers,
--renato


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