Re: Should -fcross-jumping be part of -O1?

[Robert Dewar <dewar at gnat dot com>]

Scott Robert Ladd wrote:

> Richard Kenner wrote:
>
> > I don't see why it would be any worse than all the -f options we
> > currently have.
>
>
> I agree.
>
> A thought experiment: Allow a complexity of switches for those of us
> that want to fine-tune code, while implementing "general purpose"
> switches (e.g., -Os/-Ospeed) for people who are less complexity in their
> use of GCC.
>
> Based on personal experience and the conversation herein, optimization
> appears to be a five-dimensional space with these axis:
>
>   * compilation speed (-Ospeed)
>   * debugability      (-Odebug)
>   * code size          (-Osize)
>   * execution speed   (-Ofast)
>   * FP accuracy       (-Oaccuracy)

Well as part of this thought experiment, please consider that if each of
these five axes has three settings, then there are 3**5 combinations,
which is a large number, and of course there is no possibility of the
compiler behaving in 3**5 significantly different ways.

THe above five axis layout is indeed helpful as a framework, but in 
practice I think we need to find a few useful points in this space and
pin them down, and then try to make the compiler useful at those points.