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Re: core2 flag for arch on gcc 4.3.2
- From: Tim Prince <TimothyPrince at sbcglobal dot net>
- To: tom gogh <tomgogh20 at yahoo dot com>
- Cc: gcc-help at gcc dot gnu dot org
- Date: Sat, 27 Dec 2008 21:22:36 -0800
- Subject: Re: core2 flag for arch on gcc 4.3.2
- References: <638203.10349.qm@web31402.mail.mud.yahoo.com>
- Reply-to: tprince at computer dot org
tom gogh wrote:
> I am planning to migrate my linux to 4.3.2 but, current flag for core 2 duo is nocona.
> I couldn't find elaborate explanation of core2 flag compare to nocona.
> What is difference between core2 and nocona flags?
> Do they behave identical or core2 offers better performance/tunning?
Not knowing where you're trying to go with this, default for 64-bit gcc is
good for Core 2, from no difference up to 50% better throughput than
nocona in my tests. -msse3 is available for either Nocona or Core 2 CPUs.
You probably wouldn't want the nocona option even for the older CPU. I
can't imagine why you don't simply try the options you have in mind, nor
do I understand what you mean by nocona being a current flag. Maybe you
mean the best option for some old version of gcc which predates Core 2.
I don't think -mtune=barcelona is available until more recent versions of
gcc; it may often give better vectorization even on Core 2, particularly
for Fortran, maybe for C, not so much for C++.