power4 optimization

[Hollis Blanchard]

On Tuesday, Oct 14, 2003, at 18:08 US/Central, Anton Blanchard wrote:
>
> It makes sense to optimise for POWER4 in the default kernel. Up until
> recently -mcpu=POWER4 would tune for it but would still run on RS64 and
> POWER3.
>
> Unfortunately the mtcrf optimisation in POWER4 results in an illegal
> instruction on POWER3.

How about the (totally untested) attached patch?

As future CPUs gain their own gcc optimizations it should turn into a
Kconfig "choice", but this will work for now...

Questions:
1. what version of gcc started using the mtcrf optimization?
2. do RS64 CPUs support mtcrf?
3. what is the marketing name for RS64? :) (for the Kconfig help text)

--
Hollis Blanchard
IBM Linux Technology Center
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