http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56244
Bug #: 56244 Summary: -O3 should imply -funroll-loops Classification: Unclassified Product: gcc Version: unknown Status: UNCONFIRMED Severity: normal Priority: P3 Component: driver AssignedTo: unassig...@gcc.gnu.org ReportedBy: joost.vandevond...@mat.ethz.ch As suggested by Richard, -O3 should imply -funroll-loops http://gcc.gnu.org/ml/gcc/2013-02/msg00073.html I think this makes a lot of sense. For our simulation codes, we essentially add it 'by default' yielding small but measurable speedups (1%?). Having it on by default (like vectorization), will likely improve the heuristics, and the interaction with e.g. vectorization will improve.