[Cbe-oss-dev] [RFC, PATCH] selection of CPU optimization

Segher Boessenkool segher at kernel.crashing.org
Sat Apr 14 04:43:02 EST 2007

> My understanding at this point is that we can always fall back
> to -mcpu=powerpc or -mcpu=powerpc64,

Yes.  With perhaps and added -mno-string or similar if
some supported CPU really needs it.

>  and also


> So if we select e.g. power6 and cell, it needs to fall back to power4,
> which is the common subset. Selecting both 403 and 405 would result
> in falling back to -mcpu=powerpc, because they don't have any larger
> subset.

This is way complicated.  Also, it is not unique to the
kernel; you'd be better off adding this logic to the
compiler itself.  OTOH, it's such a niche market, maybe
the distros that want it (if any do) should do this in
their RPM build scripts or similar.


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