Re: open64 versus gcc

Steven Bosscher <stevenb.gcc@gmail.com>
26 Nov 2006 21:44:55 -0500

          From comp.compilers
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open64 versus gcc drizzle76@gmail.com (dz) (2006-11-22)
Re: open64 versus gcc shreyas76@gmail.com (shrey) (2006-11-24)
Re: open64 versus gcc touati.sid-pas-de-spam-svp@gmail.com-pasdespam (touati) (2006-11-24)
Re: open64 versus gcc stevenb.gcc@gmail.com (Steven Bosscher) (2006-11-26)
Re: open64 versus gcc Sid-pasdespam.Touati@inria.fr (Sid Touati) (2006-11-27)
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Re: open64 versus gcc alewando@fala2005.com (A.L.) (2006-12-01)
Re: open64 versus gcc jthorn@aei.mpg-zebra.de (Jonathan Thornburg -- remove -animal to reply) (2006-12-03)
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From: Steven Bosscher <stevenb.gcc@gmail.com>
Newsgroups: comp.compilers
Date: 26 Nov 2006 21:44:55 -0500
Organization: Compilers Central
References: 06-11-094 06-11-100
Keywords: GCC, performance
Posted-Date: 26 Nov 2006 21:44:54 EST

On 24 Nov 2006 08:21:12 -0500, touati wrote:
> Actually, Open64 produces better code than gcc.


Ah, generalizations... It depends on the target you want to look at.
Open64 on Itanium destroys GCC, but on e.g. AMD64 the difference is
really not that much. Sometimes, Open64 compilers produce better code
than GCC, and sometimes GCC produces better code. For example, look
at the following comparable SPEC results:


http://www.spec.org/osg/cpu2000/results/res2006q3/cpu2000-20060814-06971.html
http://www.spec.org/osg/cpu2000/results/res2006q3/cpu2000-20060724-06813.html


PathScale is an Open64-based compiler. Note that the PathScale
scores are with profile feedback, and only base runs were done
with GCC. The GCC baseline rate (without PDO) is within 10% of
the PathScale scores (with PDO).


What's certainly true is that Open64 has more optimizations
implemented, especially Open64 2.0 for Itanium. But whether
those pay off for other targets, I don't know. Also, the
implementation of some of these optimizations is apparently
very Itanium-specific (people from STM wrote about this here:
http://www.st.com/stonline/press/magazine/stjournal/vol0102/special_report/pdf/vol12sr.pdf).




> Open64 is programmed in C++, while gcc is programmed in C.
> Open64 is not as maintained as gcc.
> gcc has more backends compared to Open64.


Does anyone even know how many Open64 backends there are? The
more visible ones are the Itanium and x86-64 backends, but are
there others (publicly) available?


> The gcc comunity is larger, but this is not a quality criteria.


It should help for stability though.


Gr.
Steven

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