Re: -funsafe-loop-optimizations

[Robert Dewar <dewar at adacore dot com>]

Mark Mitchell wrote:
> 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?  I hope that we can move forward with an option to address
> > these performance regressions and allow users to request this optimzation
> > when they *do* want it, along the lines of the draft patch.

> I would certainly agree.  I think the first thing to do is to get a 
> patch that implements the semantics we want, in the aggressive mode; 
> then, we can decide whether we want it to be the default at some 
> optimization level or not.

I agree except that "less strict induction variable semantics" is
not an acceptable semantic description, and I think it is essential
to have a clear simple semantic description of what this means.

So to me, the first step is a spec that describes "the semantics we
want"

A patch is the second step, not the first!