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Martin Herrman wrote: |
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> On Tue, Dec 9, 2008 at 1:23 PM, Sami Näätänen <sn.ml@××××××××××××.fi> wrote: |
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> |
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> to /etc/portage/package.keywords. With 4.3.2 I use: |
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> CFLAGS="-march=native -O2 -pipe" |
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> |
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> With only a small effort, you get most of the benefits. So fine-tuning |
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> to the edge will give you issues to solve with only a very small |
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> percentage of performance increase in return. |
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> |
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> My 2 cents.. |
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> |
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> Martin |
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My vote goes for this one, too. In general, anything higher than -O2 |
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will bring you next to nothing in best case, on averagy you'll end with |
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longer code that executes about the same and in some cases, result will |
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be slower. BY far most important thing, at least in general seems to be |
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to nail your march right, in oreder for compiler to be able to utilize |
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all that cpu has to offer. |
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For my Phenom "-march=barcelona" is optimal, but then I have problems |
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with "<=gcc-4.2*", which has no separate K-10 backend, so |
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"-march=native" is optimal - which means that gcc checks the CPU it is |
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running on and makes the best available choice. |
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If all your gcc compilers are of version 4* upwards, then also |
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"-combine" might be useful. |
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In short, CFLAGS="-march=native -O2 -pipe -combine" is optimal for me... |
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Regards, |
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Branko |
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