On 2012/12/20 19:41, Edd Barrett wrote: > What would proper testing of -O3 for gcc4 arches entail? Would this be > building the whole ports tree -O3 and trying the packages.
While I think there are (a very few) cases where it makes sense to test/enable higher O levels on an arch by arch basis doing this for the whole tree would be insane. > Is there a more systematic approach, like a test suite or benchmark > of correctness? Bugs notwithstanding, optimisers assume things about code and change results of undefined behaviour and corner cases in ways people don't expect. Test suites and benchmarks of the compiler/optimiser aren't going to help predict what it will do with some unknown code. If (and only if) a particular very performance-sensitive program has regularly been built on other OS on a certain arch with a certain optimisation level with a similar compiler I think we might consider that. Otherwise stick with the OS default.
