Re: GCC code quality, was Compiler Companies in Australia

"Robert H" <robert.hundt@gmail.com>
22 Jul 2005 20:18:42 -0400

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From: "Robert H" <robert.hundt@gmail.com>
Newsgroups: comp.compilers
Date: 22 Jul 2005 20:18:42 -0400
Organization: http://groups.google.com
References: 05-07-00805-07-017
Keywords: GCC

>> I'd be interested to hear about the research you might have done to
>>make this kind of claim. What compilers have you compared, on
>>what
>>platforms? What did the numbers look like?


I can't tell you too many details. However, from our experience and
measurements on Itanium HP-UX and Linux, I can tell you that gcc is the
far inferior compiler in terms of performance when compared, for
example, against the Intel compiler, our HP-UX compiler, or the ORC
(Open64 compiler) and its derivatives. It is decent for integer
benchmarks, but for some benchmarks, in particular fp, gcc is up to 70%
behind - and more! (but take this number with a grain of salt - many
compilers are heavily tuned for SPEC ;-). But even on the upcoming SPEC
2006, where the vendors didn't have the time to fully tune yet, gcc is
behind a lot.


Sorry for being vague at this point. You should be able to decode some
of the details by looking at various sources, such as the SPEC pages
and other company disclosures and academia papers.


gcc's strenght is portability - and it is getting better and better in
the high level optimizer (just see new SSA framework in 4.0, or the
LLVM effort). Machine specific optimizations, which are particularly
important for Itanium, are not up to snuff - yet ;-)


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