Re: changing "configure" to default to "gcc -g -O2 -fwrapv ..."

["Richard Guenther" <richard dot guenther at gmail dot com>]

On 12/31/06, Richard Kenner <kenner@vlsi1.ultra.nyu.edu> wrote:
> > I think this is a fragile and not very practical approach.  How do
> > you define these "traditional" cases?
>
> You don't need to define the "cases" in advance.  Rather, you look at
> each place where you'd be making an optimization based on the non-existance
> of overflow and use knowlege of the importance of that optimization and the
> types of code likely to trigger it to choose the default for whether to make
> it or not.  It seems quite practical to me.
>
> It also doesn't seem fragile: if you guess wrong on one particular default,
> it's easy to change it.

Are you volunteering to audit the present cases and argue whether they
fall in the "traditional" cases?  Note that -fwrapv also _enables_ some
transformations on signed integers that are disabled otherwise.  We for
example constant fold -CST for -fwrapv while we do not if signed overflow
is undefined.  Would you change those?

Richard.