On Thu, 2017-08-31 at 22:11 +0200, Florian Weimer wrote:
On 08/31/2017 09:45 PM, David Woodhouse wrote:
> On Thu, 2017-08-31 at 15:40 -0400, Josh Boyer wrote:
>> As a middle ground, does disabling POWER6 and POWER7 variants save
>> significant time? Having 970 and POWER8 covers the lowest commonly
>> avaiable "cheap" option as well as the newest released POWER
>> hardware.
>
> POWER6 is in-order, so *if* we still care about it at all then there is
> potentially some benefit in having a dedicated build for it. Dropping
> POWER7 is probably a no-brainer; it ought to cope with whatever we
> throw at it.
Could we build the 970 baseline build with -mtune=power6? Then perhaps
we only need two builds.
We are only taking PPC64BE here...
970 is is really power4+ altivec so it is very back level compared to
power6 which added DFP.
But I can certainly drop POWER7 as a first step and see how the
build
time compares with armhfp.
power7 is major update with Vector Scalar Extensions (more registers and
200+ new instructions).
If you want to cut back you can't try 970 as base, plus power6 and
power7 -mtune power8
Thanks,
Florian
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