Re: [ppc] Include hwcap as ifunc argument

[David Miller <davem at davemloft dot net>]

From: Richard Henderson <rth@twiddle.net>
Date: Mon, 21 May 2012 13:29:59 -0700

> On 05/21/12 12:42, David Miller wrote:
>> And on this topic I frankly think, as I did when I made the original
>> sparc change, that we should pass the hwcaps into the IFUNC resolvers
>> on every target not just a select few.
> 
> I'm ok not doing this for x86.  The hwcap word is totally useless
> for x86_64, and next to useless for i686.  Users will have to go
> to the other cpuid words for anything interesting anyway.

This argument against doing it on x86 is circular, let me tell you
why.

The only reason it's useless on x86, is because x86 ran into the
same problem I'm about to run into on sparc.  Namely, running out
of bits in the HWCAP aux vector entry.

So the only reason it's really useless is because it only reports
the first cpuid word.

If the aux vector hwcaps were extended to be able to report more
words, and then subsequently propagate them into the ifunc, then
we'd be solving two problems.

First, I'd have a solution for the sparc hwcap issue.

Second, we really could start to move away from all of the cpuid
probing stuff that has to be done on x86.