Re: Do C++ signed types have modulo semantics?

[Mark Mitchell <mark at codesourcery dot com>]

Daniel Berlin wrote:
> On Tue, 28 Jun 2005, Mark Mitchell wrote:
>
> > Joe Buck wrote:
> >
> > > I don't think we should give the user any such promise, and if we do
> > > give such a promise, we will never catch icc.  The main problem is that
> > > we will no longer be able to optimize many loops.
> >
> >
> > It's entirely possible that I was naive in assuming that this wouldn't 
> > have a big optimization impact.  Reiterating my response to Daniel, if 
> > it is in fact the case that this is a major loss for optimization, 
> > then I would have to retract my claim.
>
>
> I've got some notes in to various XLC people to get info if they have 
> actual numbers.
>
> However, in the meanwhile, the manual actually says it causes very 
> severe performance degradation, and that you are better off doing -O2 
> and -qnostrict_induction than -O3 + qstrict_induction, if it makes your 
> code work.

OK.  I'll withdraw my statement, then.  And, so, I now think that 
<limits> needs to change is_modulo back to false.

--
Mark Mitchell
CodeSourcery, LLC
mark@codesourcery.com
(916) 791-8304