-----Original Message----- From: Vladimir Makarov <vmakarov@xxxxxxxxxx> To: Ian Lance Taylor <iant@xxxxxxxxxx> Date: Thu, 05 Oct 2006 12:08:28 -0400 Subject: Re: gcc 3.4.3: -march optimization for Intel Core2Duo Ian Lance Taylor wrote: >"Jan Dillmann" <jan.dillmann@xxxxxxxxxx> writes: > > > >>we are running several benchmarks (SpecCPU200...) on 32-bit linux-systems and are able to set an optimization-parameter >>for '-march'. We use Intel Core2uo-CPUs. Which parameter should we use (nocona, prescott...) ? >> >> > >gcc 3.4.3 has no specific tuning for Core2 Duo, if for no other reason >than the release was made before the processors became available. My >guess would be that you will get the best results with -mtune=nocona. >But it is only a guess. > > > I believe that pentium-m will work better. Nocona (a x86_64 processor) is based on northwood/prescott core which is a high frequency core with long pipelines. Core2 Duo is closer to pentium M (lower frequency core with much shorter pipelines). Although usage of penium-m will result a bigger code in comparison with nocona because aligning loop/function will be forced (nortwood core is not so sensitive to aligning therfore aligining is not done when -mtune=nocona is used). I don't remember Intel recomendation about aligning code for Core Duo (probably it is the same as for penium M). ________________________________ FWIW, pentium-m is optimized by using 387 code for nearly everything except (int) casts. This is because of the Banias SSE decoder bottleneck. If you use -march=pentium-m, you would add -fpmath=sse to attempt to get code more optimum for any CPU other than Banias/Dothan. OP question was about Core 2 Duo, a more advanced (64-bit capable) CPU than Core Duo. Tim Prince
