Re: optimizing compilers
Re: optimizing compilers
- Subject: Re: optimizing compilers
- From: John Hörnkvist <email@hidden>
- Date: Fri, 1 Feb 2002 23:07:10 +0100
On Friday, February 1, 2002, at 08:34 PM, Finlay Dobbie wrote:
No, it's a combination of multiple factors. It's well known that gcc
2.95.2 sucks for PPC code generation.
As far as I know, gcc sucks for code generation, period. You can help it
a fair bit by using some of the attributes and language extensions that
it implements.
I think it should be better with gcc 3.1, which Stan Shebs and the
Apple compiler team are working overtime on bringing up to scratch on
Darwin/OS X.
I've benchmarked a fairly recent version of gcc 3.1 and 2.95.2, and the
difference has been quite small.
To make matters worse, the PPC seems rather sensitive to bad code; when
I turn on optimizations in my research compiler, I can speed up
execution by almost a factor of three on the PPC (16.11 to 5.76 seconds)
but less than two times on an AMD Duron (7.95 to 4.32 seconds).
I heard a while back that they moved a lot of their ex-MrC engineers
over to work on gcc 3.1/Darwin (MrC was Apple's compiler that was part
of MPW, and it was widely recognised as being one of the most
optimizing PPC compilers. see
http://developer.apple.com/tools/mpw-
tools/compilers/benchmarks/index.html for examples).
Well, that makes sense; no reason to have them working on a dead
compiler.
Regards,
John Hornkvist
--
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