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Re: contribution
- From: Toon Moene <moene at knmi dot nl>
- To: Andi Kleen <ak at suse dot de>
- Cc: gcc at gcc dot gnu dot org, starlex at eng dot sun dot com
- Date: Fri, 12 Apr 2002 12:53:54 +0000
- Subject: Re: contribution
- Organization: Royal Netherlands Meteorological Institute
- References: <3CB6D448.45A4FE3E@knmi.nl.suse.lists.egcs> <p73ads9axvo.fsf@oldwotan.suse.de>
Andi Kleen wrote:
> > > You could compiled 172.mgrid with gcc twice this way and it showed
> > > 48% improvement ? Or did you use a different compiler as backend?
> > > If you used gcc - is it known where that huge difference comes
> > > from?
> To be honest I don't believe that he got that result with multiple runs
> of gcc. If yes that would be a very bad bug in the optimizer. More likely
> it was reached with the proprietary Sun compiler as backend (that would
> make the patch more a porting tool for GNU C programs to Sun C)
Hmm, I wouldn't be surprised at all ... When g77 came out (in February
'95) we had a hard time beating the f2c+gcc combo. It might still be
the case that, e.g., multi-rank array code (as in mgrid) is treated more
optimally by the gcc middle-end when first "squashed" by a Fortran to C
converter into a linear array.
--
Toon Moene, KNMI, PO Box 201, 3730 AE De Bilt, The Netherlands.
Tel. +31302206443, Fax +31302210407, e-mail moene@knmi.nl
URL: http://www.knmi.nl/hirlam