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Date: Wed, 17 Nov 2021 14:00:02 -0600
From: Segher Boessenkool <segher@kernel.crashing.org>
To: "Paul A. Clarke" <pc@us.ibm.com>
Cc: wschmidt@linux.ibm.com, GCC Patches <gcc-patches@gcc.gnu.org>,
 David Edelsohn <dje.gcc@gmail.com>
Subject: Re: [PATCH] rs6000: Better error messages for power8/9-vector builtins
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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?


Segher