Re: [RFC] Enabling loop unrolls at -O3?

[Robert Dewar <dewar at adacore dot com>]

Giovanni Bajo wrote:

> I believe you are missing my point. What is the GCC command line option for
> "try to optimize as best as you can, please, I don't care compiletime"? I
> believe that should be -O3. Otherwise let's make -O4. Or -O666. The only real
> argument I heard till now is that -funroll-loops isn't valuable without profile
> feedback. My experience is that it isn't true, I for sure use it for profit in
> my code. But it looks like the only argument that could make a difference is
> SPEC, and SPEC is not freely available. So I'd love if someone could
> SPEC -funroll-loops for me.

It is not at all the case that SPEC is the only good argument, in fact
SPEC on its own is a bad argument. Much more important is impact on real
life applications, so your data point that it makes a significant difference
for your application is more interesting than SPEC marks. When it comes
to GCC, we are more interested in performance than good SPEC figures!
> Giovanni Bajo