Date: 10 Apr 2000 09:19:07 +0300 From: Ville-Pertti Keinonen <will@iki.fi> To: kris@FreeBSD.org (Kris Kennaway) Cc: hackers@FreeBSD.org Subject: Re: What are the best gcc optimization options for Pentium 200 MMX Message-ID: <86snwuwk9w.fsf@not.demophon.com> In-Reply-To: kris@FreeBSD.org's message of "9 Apr 2000 00:19:09 %2B0300" References: <Pine.LNX.4.10.10004082114170.23805-100000@inet.ssc.nsu.ru> <Pine.BSF.4.21.0004081416110.70551-100000@freefall.freebsd.org>
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kris@FreeBSD.org (Kris Kennaway) writes: > Can you say "gimmick"? :-) gcc often produces demonstrably broken code for > optimisation levels higher than -O. That -O is safe seems to be a persistent myth. GCC also produces broken code for -O and no optimization in some cases, sometimes while producing working code for higher optimization levels... I wouldn't state e.g. that -O2 produces broken code any more often than -O, this may have been true for version X.Y.Z but is certainly not universally true. I believe that the reasons the FreeBSD build uses -O are the fact that especially with older versions of gcc, -O2 slowed down compilation considerably for little noticable performance improvement (as for -O3, automatic inlining is generally undesirable), and it is always best to only have to test the system with a single set of flags. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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