On Mon, Jan 19, 2015 at 6:03 PM, Jeff Law <l...@redhat.com> wrote: > On 01/17/15 07:34, Gary Funck wrote: >> >> On 01/14/15 23:15:59, Jeff Law wrote: >>> >>> Sounds good. I think just starting with the list & creating the buckets >>> with the list. Then post here and we'll iterate and try to nail that >>> down >>> before you start moving everything in the .texi file. >> >> >> Something to consider, if the optimization options are re-worked: >> Arrange the -O options such that -O1 can be described by a >> distinct set of specific optimizations enabled (or disabled) >> in addition to -O0, and -O2 would be described as a composite >> of specific optimizations applied to -O1 and so on. (This >> might require the addition of new optimization options.) > > For -O1 to -O2 and -O2 to -O3, that makes sense. However, -O0 to -O1 isn't > something we can do this for right now as there are still many things that > -O1 turns on that are not flag controlled. > > Whether or not to make all those bits individually controllable is a subject > of debate. Personally, I think we have too many options, so my inclination > would not be to make all those bits individually controllable. Others may > have different opinions.
Also note that I'd like to go away from sharing the same pipeline with -O1 and -O2 at least. -Og started this already (you can't turn on extra passes in the -Og GIMPLE pipeline) and the -O1 "pipeline" doesn't make much sense currently - I'd rather base -O1 on -Og or split it away completely. The issue here is that a single flag controls multiple instances of a pass, and -O1 would still have things like -ftree-copy-prop but not run as many times as -O2 (and -O1 currently). For us developers I'd always envisioned to make our pass manager scriptable and the pass pipeline being basically a script (so you can even do things like iterating ... heh). So I really really don't believe in the usefulness of 95% of the optimization options we have (to a compiler user). And I'd rather flag most of them as debugging ... Richard. > jeff >
