----- Original Message ----- > > On Sep 3, 2013, at 9:53 AM, Rafael Espíndola > <[email protected]> wrote: > > >>> This is something Chris requested, IIRC. I'm not sure I remember > >>> the > >>> motivation beyond that. > >> > >> Two reasons: > >> > >> 1) -O1 doesn't actually mean anything. It is the optimization > >> level least understood by both the GCC folks and us. Recently > >> (last 5 years?) there has been a move to try to make this > >> "optimize without messing up debug info", but this is a new > >> movement. > > > > Another thing that is making -O1 better defined is asan. It is the > > optimization level that makes asan fast but still provides useful > > backtraces :-) > > Ok, makes sense. Those uses can use an explicit -O1 though :-) > > > > >> 2) Users who specify -O generally don't know it maps onto -O1. > >> They almost certainly don't want whatever -O1 provides. In my > >> experience, most are coming from Sun, HP or other compilers, > >> where -O was a generally useful flag. > >> > >> 3) There are some benchmarks that pass -O (because of #2), which > >> is ridiculous, but reflects some reality that people use -O. I > >> don't recall what these benchmarks were. > >> > >> These are reasons that I suggested the change. I really don't > >> like -O1 :-) > > > > I haven't seen -O being used in wild, so I OK with keeping it > > mapping to -O2. > > I'd be curious to know how many files in a linux distro are built > with -O. I wouldn't be surprised if it is 5-10%.
FWIW, IBM's xlc compiler (at least the version on the BG/Q machines), have several -O<level>, but specifically omit -O1. -O is an alias to -O2. -Hal > > -Chris > _______________________________________________ > cfe-commits mailing list > [email protected] > http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits > -- Hal Finkel Assistant Computational Scientist Leadership Computing Facility Argonne National Laboratory _______________________________________________ cfe-commits mailing list [email protected] http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
