This is the mail archive of the
gcc@gcc.gnu.org
mailing list for the GCC project.
Re: -funsafe-loop-optimizations
- From: Olivier Galibert <galibert at pobox dot com>
- To: Richard Henderson <rth at redhat dot com>,David Edelsohn <dje at watson dot ibm dot com>,Daniel Berlin <dberlin at dberlin dot org>,Zdenek Dvorak <rakdver at atrey dot karlin dot mff dot cuni dot cz>, gcc at gcc dot gnu dot org
- Date: Sat, 1 Jan 2005 16:52:47 +0100
- Subject: Re: -funsafe-loop-optimizations
- References: <20041231211409.GA22814@atrey.karlin.mff.cuni.cz> <Pine.LNX.4.60.0412311649170.6844@dberlin.org> <20041231232501.GA16663@redhat.com> <200501010543.j015h3D33264@makai.watson.ibm.com> <20050101101152.GA17037@redhat.com>
On Sat, Jan 01, 2005 at 02:11:52AM -0800, Richard Henderson wrote:
> On Sat, Jan 01, 2005 at 12:43:03AM -0500, David Edelsohn wrote:
> > While we discuss whether this should be the default or enabled at
> > any optimization level, can we agree that users should be able to assert
> > with a commandline option that they want less strict induction variable
> > semantics?
>
> And/or a -W option that warns for these sorts of loops so that
> (a) we can see how often this happens, really, (b) so that users
> can fix the presumed mistake.
If you could detect them and warn for them, you could not optimize
them in the first place (and that's what happens when the boundaries
are constants). They're detectable only at runtime and even en not
necessarily easily.
OG.