Re: [PATCH Linux] powerpc: add documentation for HWCAPs

From: Segher Boessenkool <segher@kernel.crashing.org>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: Florian Weimer <fweimer@redhat.com>,
	gcc@gcc.gnu.org, libc-alpha@sourceware.org,
	linuxppc-dev@lists.ozlabs.org,
	Paul E Murphy <murphyp@linux.ibm.com>
Subject: Re: [PATCH Linux] powerpc: add documentation for HWCAPs
Date: Fri, 15 Jul 2022 09:35:54 -0500	[thread overview]
Message-ID: <20220715143554.GY25951@gate.crashing.org> (raw)
In-Reply-To: <1657846871.9qtz2ahf6c.astroid@bobo.none>

On Fri, Jul 15, 2022 at 11:17:24AM +1000, Nicholas Piggin wrote:
> Excerpts from Segher Boessenkool's message of May 25, 2022 4:32 am:
> > Linux runs on ISA 1.xx and ISA 2.01 machines still.  "Category" wasn't
> > invented for either yet either, but similar concepts did exist of
> > course.
> 
> Not sure what to say about this. It now also has "Compliancy Subset"
> although maybe that's more like a set of features rather than
> incompatible features or modes such as some of the category stuff
> seems to be. I'll try add something.

The compliancy subset stuff is an attempt to simplify things again.
In most cases you want to require a whole swath of feature at once,
if you really try to support fine-grained optional features you need to
test thousands of configurations, while you really can test only ten
(if you are lucky!)

Maybe it is best to just be a bit vague here?

Segher