On Fri, 2007-02-09 at 01:25 +0100, Patrice Dumas wrote: > On Thu, Feb 08, 2007 at 04:16:58PM -0600, Callum Lerwick wrote: > > > > With what GCC version? And with what other flags? Optimization is an > > incredibly finicky thing, that can wildly vary depending on the version > > of GCC, and different opt flags can interact in strange ways. > > > > Unless you can show a conclusive benchmark showing -O3 is better with > > *our* GCC and all the rest of *our* opt flags, this shouldn't be allowed > > IMHO. > > Why not trust upstream? If you mean those people who implement RPM_OPT_FLAGS, then I'd agree. If you mean a packages upstream: Yes, -O3 might have improved speed on this upstream's test systems, but ... only on very rare occasions, these "upstreams" will be able to prove generality of their claims. > And if a benchmark shows that it is untrue, > come back to -O2. If i recall well -O3 make debuging harder, so there is > a choice to do, but the packager should certainly be trusted in those > cases. Your answer clearly shows you don't know what -O3 really does (I don't know either), which details it all affects and which bugs it suffers from. This is no surprise, because -O3 (like any other -Ox flags) comprises a set of optimizations which silently changes over time, can have different effect on different architectures, particular cpus and will vary between distributions (The fedora GCC is not a vanilla FSF gcc), etc. So, the only results of recommendations to trust when it comes to packaging binaries for a distro is those who are deeply familiar with the guts of the OS, in case of Fedora, RH's GCC, glibc and kernel developers. They recommend those flags in RPM_OPT_FLAGS. Ralf -- fedora-extras-list mailing list fedora-extras-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/fedora-extras-list
