gcc 3.4.3: -march optimization for Intel Core2Duo

[Vladimir Makarov]

Ian Lance Taylor wrote:

>"Jan Dillmann" <jan.dillmann@tooltec.de> 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).