Re: [PATCH] rs6000: Better error messages for power8/9-vector builtins

["Paul A. Clarke" <pc@us.ibm.com>]

On Wed, Nov 17, 2021 at 02:00:02PM -0600, Segher Boessenkool wrote:
> On Wed, Nov 17, 2021 at 11:45:02AM -0600, Paul A. Clarke wrote:
> > I guess I'm being pedantic.  "requires -mcpu=power8 and -mvsx" is not
> > accurate from a user's point a view, as "-mcpu=power8" is sufficient,
> > since "-mvsx" is enabled when "-mcpu=power8" is specified.
> 
> To be really pedantic, -mcpu=power8 isn't required either: anythng that
> enable the subset of ISA 2.07 that is needed is enough already.  But we
> don't want to encourage users to use those interfaces.
> 
> > The real "requires" is "-mcpu=power8" and no "-mno-vsx".
> 
> And no -mno-altivec.  And and and.  There is a huge web.
> 
> > It's not a strong objection, since specifying "-mno-vsx" should be
> > uncommon.  (Right?)  And, specifying "-mcpu=power8 -mvsx" is harmless.
> 
> Maybe the warning could say "requires -mcpu=power8 (and -mvsx)"?  Is
> that clearer, to your eye?

Hrm. No, but let me withdraw my expression of concern. Both "power8" and
"vsx" are required, and those two options get that explicitly.
That "-mcpu=power8" also pulls in "-mvsx" is a subtlety that is
perhaps not terribly relevant.

Thanks for entertaining my concern, but we've spent too much time on it
already.  :-)

PC