-O vs. -O2

[Florian Weimer]

* Bulat Ziganshin:

> cloning gcc policy may be a good choice. -O2 is the best optimization
> that "guaranteed" to make program faster and -O3 is for speculative
> optimization (those that may be breaked by unusual code or made
> program slower). not sure about -O1,

-O1 is supposed to yield somewhat optimized code with very good
debugging information.  Quality of debugging information at -O2 was
really abysmal for a while, but it should be improving again.