As part of the mid-2007 stability drive, we disabled many of the O2 optimizations in the opt compiler because it was generally believed that they were less stable than the rest of the code base. We've now achieved better stability than at any previous point in the project's history. It's time to re-assess the O2 optimizations and on a case-by-case basis re-enable them, fix them (if they are salvageable) or remove them entirely (if they are deemed to be unfixable).
We will proceed in a series of staged steps in this process, since when the optimizations were disabled in 2007, some of the crashes we were seeing were intermittent. A number of JIRA tasks and sub-tasks will be created under this overall item to specify the plan.