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Re: Comparison of GCC-4.9 and LLVM-3.4 performance on SPECInt2000 for x86-64 and ARM
- From: Renato Golin <renato dot golin at linaro dot org>
- To: Bingfeng Mei <bmei at broadcom dot com>
- Cc: Vladimir Makarov <vmakarov at redhat dot com>, Ramana Radhakrishnan <ramana dot radhakrishnan at arm dot com>, "gcc.gcc.gnu.org" <gcc at gcc dot gnu dot org>
- Date: Wed, 25 Jun 2014 10:32:14 +0100
- Subject: Re: Comparison of GCC-4.9 and LLVM-3.4 performance on SPECInt2000 for x86-64 and ARM
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On 25 June 2014 10:26, Bingfeng Mei <bmei@broadcom.com> wrote:
> Why is GCC code size so much bigger than LLVM? Does -Ofast have more unrolling
> on GCC? It doesn't seem increasing code size help performance (164.gzip & 197.parser)
> Is there comparisons for O2? I guess that is more useful for typical
> mobile/embedded programmers.
Hi Bingfeng,
My analysis wasn't as thorough as Vladimir's, but I found that GCC
wasn't eliminating some large blocks of dead code or inlining as much
as LLVM was. I haven't dug deeper, though. Some of the differences
were quite big, I'd be surprised if it all can be explained by
unrolling loops and vectorization...
cheers,
--renato