Date: Fri, 10 Mar 2000 15:22:44 -0600 From: Dan Nelson <dnelson@emsphone.com> To: C J Michaels <cjm2@earthling.net> Cc: wsanborn@uswest.net, questions@FreeBSD.ORG Subject: Re: Any major downside to using "-O3" when compiling? Message-ID: <20000310152244.A41054@dan.emsphone.com> In-Reply-To: <NDBBILKDCLLECBCLPMBIKEANCAAA.cjm2@earthling.net>; from "C J Michaels" on Fri Mar 10 13:28:38 GMT 2000 References: <38C1422B.16524.3085E0@localhost> <NDBBILKDCLLECBCLPMBIKEANCAAA.cjm2@earthling.net>
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In the last episode (Mar 10), C J Michaels said: > I put -O3 in my /etc/make.conf probably 4 months ago, and have done > several make world's with it and have had no problems. I am still > err'ing on the side of caution with the kernel and have left that on > -O2. > > As for performance increasing, I can't really say since I've never > run any benchmarks between the 2. > > Also, from what I have read, anything over -O3 (e.g. -O4) is broken, > do a search through the mailing list archives for more info. There is nothing over -O3. And all -O3 does is make gcc unroll as many loops as it can. This makes your code bigger, and can possibly slow it down if the unrolled loops are larger than your L1 cache size. It all depends on the code being compiled. -- Dan Nelson dnelson@emsphone.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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