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Re: Include hwcap as ifunc argument
- From: Andreas Krebbel <krebbel at linux dot vnet dot ibm dot com>
- To: Richard Henderson <rth at twiddle dot net>
- Cc: "Ryan S. Arnold" <ryan dot arnold at gmail dot com>, libc-alpha at sourceware dot org, libc-ports at sourceware dot org
- Date: Fri, 08 Jun 2012 16:00:14 +0200
- Subject: Re: Include hwcap as ifunc argument
- References: <4FBA744A.6000702@twiddle.net> <4FBFC4EC.1060209@twiddle.net> <CAAKybw_qMks+2nP=mR6=og9H3AphS50UfcOZ5OauTivE98B3Pw@mail.gmail.com> <4FCD333E.3090107@twiddle.net>
On 06/05/2012 12:14 AM, Richard Henderson wrote:
> On 06/04/2012 02:21 PM, Ryan S. Arnold wrote:
>> Peter Bergner reminded me today that on PowerPC the IFUNC resolver
>> will most likely/often use the value in AT_PLATFORM rather than
>> AT_HWCAP to determine which optimized function to use. I suppose this
>> would diminish the necessity of passing the hwcap to the ifunc
>> resolver.
>
> It depends on what's being tested, I suppose.
>
> Within glibc itself you've got lots of platform-specific tuning, so
> you may well use AT_PLATFORM more.
>
> Outside glibc, it might just be a test for Altivec or VDX or whatever.
>From a S/390 perspective AT_PLATFORM would also be more helpful. We do not add every new
machine feature to the hwcaps vector so it is not possible to deduce the cpu level just
from the hwcaps vector.
I'm working on the S/390 ifunc support and hope to be able to come up with a patch soon.
Bye,
-Andreas-