Re: Update list of i686-class processors in sysdeps/x86/cpu-features.h

[Florian Weimer <fw at deneb dot enyo dot de>]

* Joseph Myers:

> Question: would it be better to implement this conditional in a
> negative sense (!defined __i486__ && !defined __i586__ && !defined
> __geode__, based on what macros are in the fixed conditional, but
> maybe using __k6__ instead of __geode__ based on GCC's understanding
> of the options in question) to reduce the chances of it needing
> updating in future?  (__i586__ is actually handled above.)

I think the GCC developers expect that we use the individual feature
test macros (__SSE2__ etc.).  The model-based macros are useless
because CPU features are increasingly non-monotonic, and it does not
make sense to replicate GCC's view of the Intel and AMD roadmaps in
glibc.

> Question: is the inclusion of __k6__ in the present conditional
> logically incorrect, and the omission of __geode__ logically
> incorrect, as regards whether to define HAVE_I686?  The way GCC
> defines -march=k6 and -march=geode, it seems to think that the former
> excludes CMOV and the latter includes it.  (-march=geode is
> specifically "AMD Geode embedded processor with MMX and 3DNow!@:
> instruction set support.".)

Geode lacks support for long NOPs, but our i686 port requires them.