[PATCH] x86: Support BHI_CTRL instruction

[Jiang, Haochen]

> From: Jiang, Haochen
> Sent: Wednesday, August 5, 2026 4:53 PM
> 
> > From: Jan Beulich <jbeulich@suse.com>
> > Sent: Wednesday, August 5, 2026 4:50 PM
> >
> > On 03.06.2026 10:08, Jan Beulich wrote:
> > > On 03.06.2026 09:47, Jiang, Haochen wrote:
> > >> This let me further wonder if a user input something like "{rex2} ibhf",
> > >> should we accept that? Let me double check that.
> > >
> > > We should accept it if the resulting encoding does what is intended /
> written.
> > > According to Christian's reply REX2.W doesn't have the same effect, but I
> wonder
> > > if it's really sensible that way. The W bits, whether encoded in REX or REX2,
> > > really ought to have the same meaning as per the APX spec. Unless of
> course this
> > > is indeed meant to be another special case besides PUSHP/POPP (when
> imo it would
> > > be really nice if special cases were avoided whenever possible).
> >
> > Has this been clarified in the meantime? It's somewhat sad that 2.47 shipped
> > without this addition, when that has been missing for quite some time.
> 
> I have got an internal clarification for BHI_CTRL, pending for documentation
> change. REX.W and REX2.W should have the same effect. But it will take some
> time. I planned to mention it in my updated patch.
> 

Well, there are some more input which blocks my patch. I have warned them
the risk of toolchain version delay. Maybe some more time to wait. It is not
as urgent as I thought two months ago.

Thx,
Haochen