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Message-ID: <20160929220514.GI1280@port70.net>
Date: Fri, 30 Sep 2016 00:05:15 +0200
From: Szabolcs Nagy <nsz@...t70.net>
To: musl@...ts.openwall.com
Subject: Re: Model specific optimizations?
* Adhemerval Zanella <adhemerval.zanella@...aro.org> [2016-09-29 11:52:44 -0700]:
> On 29/09/2016 11:13, Rich Felker wrote:
> > On Linux it's supposed to be the kernel which detects availability of
> > features (either by feature-specific cpu flags or translating a model
> > to flags) but I don't see anything for fsqrt on ppc. :-( How/why did
> > they botch this?
>
> Maybe because recent power work on kernel is POWER oriented, where fsqrt
> is define since POWER4. However some more recent freescale chips (such
> as e5500 and e6500) also decided to not add fsqrt instruction.
>
> With GCC you can check for _ARCH_PPCSQ to see if current arch flags
> allows fsqrt. From runtine I presume programs can check for hwcap bit
> PPC_FEATURE_POWER4, however it does not help on non-POWER chips which
> do support fsqrt.
>
how can distros deal with this?
do they require POWER4?
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