This is the mail archive of the
mailing list for the GCC project.
Re: Comparing Linux C and C++ Compilers: Benchmarks and Analysis
- From: Jeremy Sanders <jss at ast dot cam dot ac dot uk>
- To: Richard Guenther <richard dot guenther at gmail dot com>
- Cc: Scott Robert Ladd <coyote at coyotegulch dot com>, gcc mailing list <gcc at gcc dot gnu dot org>
- Date: Sun, 19 Sep 2004 15:02:37 +0100 (BST)
- Subject: Re: Comparing Linux C and C++ Compilers: Benchmarks and Analysis
- References: <email@example.com>
On Sat, 18 Sep 2004, Richard Guenther wrote:
You may want to check gcc 4.0s auto-vectorizing capabilities by using
-ftree-vectorize. I believe Intel compiler does this by default with
your optimization settings, and also unrolls loops where profitable
(-funroll-loops for all gcc versions). While I personally do not have
success with auto-vectorizing (neither with Intel nor with gcc), loop
unrolling shows very positive effects on my numerical codes.
I tried compiling scimark with gcc 4 with -ftree-vectorize -msse2
-fdump-tree-vect-stats and again with the lno branch. This was with a P4
on Fedora Core 2. Looking at the generated .vect files, it looked like gcc
wasn't able to vectorize any of the loops in scimark, which is a bit
diappointing. It's possible I didn't use it correctly I suppose.
Jeremy Sanders <firstname.lastname@example.org> http://www-xray.ast.cam.ac.uk/~jss/
X-Ray Group, Institute of Astronomy, University of Cambridge, UK.
Public Key Server PGP Key ID: E1AAE053