This is the mail archive of the
gcc@gcc.gnu.org
mailing list for the GCC project.
Re: Serious performance regression -- some tree optimizer questions
- From: Toon Moene <toon at moene dot indiv dot nluug dot nl>
- To: Jakub Jelinek <jakub at redhat dot com>
- Cc: Ulrich Weigand <Ulrich dot Weigand at de dot ibm dot com>, Zdenek Dvorak <rakdver at atrey dot karlin dot mff dot cuni dot cz>,Zdenek Dvorak <dvorakz at suse dot de>, gcc at gcc dot gnu dot org, Michael Matz <matz at suse dot de>
- Date: Wed, 29 Dec 2004 21:34:27 +0100
- Subject: Re: Serious performance regression -- some tree optimizer questions
- Organization: Moene Computational Physics, Maartensdijk, NL
- References: <20041227013815.GA3289@atrey.karlin.mff.cuni.cz> <OF310432D7.DA8A69F1-ON41256F79.00503BE7-41256F79.0051125D@de.ibm.com> <12354968.1104334291868.JavaMail.root@dtm1eusosrv72.dtm.ops.eu.uu.net>
Jakub Jelinek wrote:
On Wed, Dec 29, 2004 at 03:45:31PM +0100, Ulrich Weigand wrote:
[ Serious performance regression in SPEC2000's mgrid*.f* ]
It is not always constant.
Consider say unsigned int i; on LP64 target and
char A[(long) UINT_MAX + 1];
&A[i+1] - &A[i] is (ptrdiff_t) 1 unless i == UINT_MAX, for which
it is - (ptrdiff_t) UINT_MAX.
Oh, sure, but we are talking Fortran here - you can't apply the
limitations of C to a discussion about optimizing Fortran code. Fortran
knows of no UINT_MAX, or the intrincacies of C's ptrdiff_t.
:-)
--
Toon Moene - e-mail: toon@moene.indiv.nluug.nl - phone: +31 346 214290
Saturnushof 14, 3738 XG Maartensdijk, The Netherlands
Maintainer, GNU Fortran 77: http://gcc.gnu.org/onlinedocs/g77_news.html
A maintainer of GNU Fortran 95: http://gcc.gnu.org/fortran/