On Wed, Jun 25, 2014 at 5:26 PM, Bingfeng Mei <b...@broadcom.com> wrote: > Thanks for nice benchmarks. Vladimir. > > Why is GCC code size so much bigger than LLVM? Does -Ofast have more unrolling On the contrary, I don't think rtl unrolling is enabled by default on GCC with level O3/Ofast. There is no unroll dump file at all unless -funroll-loops/-funroll-all-loops is explicitly specified.
Thanks, bin > 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. > > Bingfeng > >> -----Original Message----- >> From: gcc-ow...@gcc.gnu.org [mailto:gcc-ow...@gcc.gnu.org] On Behalf Of >> Vladimir Makarov >> Sent: 24 June 2014 16:07 >> To: Ramana Radhakrishnan; gcc.gcc.gnu.org >> Subject: Re: Comparison of GCC-4.9 and LLVM-3.4 performance on >> SPECInt2000 for x86-64 and ARM >> >> On 06/24/2014 10:57 AM, Ramana Radhakrishnan wrote: >> > >> > 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. >> > >> There are some few benchmarks which benefit from autovectorization (eon >> particularly). >> >>> 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. >> Thanks, Ramana. Next time, I'll try these options. >> > >> > 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. >> > >> The results are pretty stable. Also this version of Fedora does not >> implement switching from Big to Little processors. >
