[PATCH] x86: Support BHI_CTRL instruction

[Jiang, Haochen]

> From: Christian Ludloff <ludloff@gmail.com>
> Sent: Thursday, June 4, 2026 4:07 AM
> 
> On Wed, Jun 3, 2026 at 1:16 AM Jiang, Haochen <haochen.jiang@intel.com>
> wrote:
> > I am confirming with arch team for these issues. This instruction seems to me
> > the first instruction we only borrowed W1 with no effect, other using
> REX.W1
> > at least implied operand size. This definitely needs some clarification.
> >
> > Will come back to you all after I get a clear answer.
> 
> Arguably RDSSP{D,Q} is a litmus test – can it REX2 or EVEX?

I suppose it should be a REX2, not EVEX MAP4. Its opcode is in those
REX2 permitted opcode.

Thx,
Haochen