This is the mail archive of the
gcc@gcc.gnu.org
mailing list for the GCC project.
Re: mul + div with 64 bit signed ints on IA32
- To: Tim Prince <tprince at computer dot org>
- Subject: Re: mul + div with 64 bit signed ints on IA32
- From: Jan Hubicka <jh at suse dot cz>
- Date: Wed, 5 Sep 2001 13:44:05 +0200
- Cc: Frank Klemm <pfk at fuchs dot offl dot uni-jena dot de>, Jan Hubicka <jh at suse dot cz>, gcc at gcc dot gnu dot org
- References: <20010827004731.G2544@fuchs.offl.uni-jena.de> <20010827121624.D8568@atrey.karlin.mff.cuni.cz> <20010827143032.C636@fuchs.offl.uni-jena.de> <20010827173025.F11402@atrey.karlin.mff.cuni.cz> <20010901202854.A7713@fuchs.offl.uni-jena.de> <20010902000000.C27182@atrey.karlin.mff.cuni.cz> <20010902024104.F7713@fuchs.offl.uni-jena.de> <20010903171717.E13574@atrey.karlin.mff.cuni.cz> <20010904215156.C438@fuchs.offl.uni-jena.de> <007001c1358e$6f53b6f0$7edd18ac@amr.corp.intel.com>
> > Option proposals:
> >
> > -fsaverc
> > -ffastrc
> > -fsavecld ; the same for the cld flag
> > -ffastcld
> >
> glibc includes implementations of lrint() and the like. I'd like
> to see something like -ffast-rint to support g77 (Fortran
> spelling -ffast-nint), which has a precedent in the MipsPro
> compilers. That only modifies the code to accept IEEE style
> round-to-nearest in place of Fortran style round-to-nearest.
This appears to be requested commonly enought and make perfect sense for 3d
software, where converison to integer is perofrmance cirtical and IEEE
behaviour secondary. With my new 3.1 mode switching implementation it can be
easy to make gcc expect "round towards zero" CW setting, so I can implement it.
Insead of -ffast-rint, I think we can name it -mround-towards-zero, as it
will make user to more think what the switch actually does.
When compiling it can make fast fp->int converison to be generated and we
can manage spec file to link in an library to actually set the switch,
as we do on other platforms for -ffast-math.
Sounds sensible?
Honza
>