On 2016.10.27 at 18:08 +0100, Sven C. Dack wrote: > On 27/10/16 17:30, Marc Glisse wrote: > > On Thu, 27 Oct 2016, Sven C. Dack wrote: > > > > > I've been installing private copies of gcc for a while now, but only > > > recently did I notice that my distro's gcc (Debian testing) is doing > > > much better when comparing compile times than any of my copies. For > > > instance does it take 230s for my copy to compile a linux kernel, > > > but only 163s for my distro's gcc, which is almost a minute in > > > difference for something that doesn't take more than 3-4 minutes to > > > compile. > > > > > > What makes this noteworthy for me is that I've compiled my copy with > > > profiledbootstrap and LTO enabled and also optimized it for my CPU, > > > whereas the distro's compiler won't have been optimized quite that > > > much, but yet is it so much faster in speed. I don't know how > > > exactly my distro's gcc has been set up, because the Debian build > > > rules are rather complex and include their own set of patches. So I > > > thought I start with asking here first. > > > > > > What is that can make such a huge difference in compile speed for > > > two copies of gcc, both version 6.2, using the same options, on the > > > same source? Or are any of the configure options know to have a huge > > > impact on the resulting compiler's speed? > > > > --enable-checking=release would be the first thing to check. > > > Thank you, will do. > > I can already say that I am using "yes", because I'm using the latest git > versions and have always favoured a reasonable amount of checks. If this is > already the cause for the difference then I might actually keep it this way. Yes, this is the cause. You can use -fno-checking to switch some checks off at compile time. -- Markus
