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[PATCH 1/9] x86: refine TPAUSE and UMWAIT

H.J. Lu hjl.tools@gmail.com
Thu Mar 5 14:38:00 GMT 2020 
On Thu, Mar 5, 2020 at 6:08 AM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 05.03.2020 15:04, H.J. Lu wrote:
> > On Thu, Mar 5, 2020 at 12:08 AM Jan Beulich <jbeulich@suse.com> wrote:
> >>
> >> On 04.03.2020 12:44, H.J. Lu wrote:
> >>> On Wed, Mar 4, 2020 at 3:40 AM Jan Beulich <jbeulich@suse.com> wrote:
> >>>> On 04.03.2020 12:36, H.J. Lu wrote:
> >>>>> On Wed, Mar 4, 2020 at 1:37 AM Jan Beulich <jbeulich@suse.com> wrote:
> >>>>>> Allowing 64-bit registers is misleading here: Elsewhere these get allowed
> >>>>>> when there's no difference between either variant, because of 32-bit
> >>>>>> destination registers having their upper halves zeroed in 64-bit mode.
> >>>>>> Here, however, they're source registers, and hence specifying 64-bit
> >>>>>> registers would lead to the ambiguity of whether the upper 32 bits
> >>>>>> actually matter.
> >>>>>>
> >>>>>> Additionally, for proper code generation in 16-bit mode, IgnoreSize is
> >>>>>> needed on both.
> >>>>>
> >>>>> Are there testcases to show IgnoreSize is needed on them?
> >>>>
> >>>> The situation with 16-bit test cases is rather poor anyway. I didn't
> >>>> consider it reasonable to add such very special ones when far more
> >>>> general ones don't exist. But if your question is to mean you demand
> >>>
> >>> Let's start from somewhere.
> >>>
> >>>> such to be added, then I'll (somewhat hesitantly) add/extend some.
> >>>> Please clarify.
> >>>
> >>> Please add testcases.
> >>
> >> Actually they were there, in patch 2. I've moved them to this patch
> >> and have just sent v1.1 for just this one patch.
> >
> > Do we need to adjust disassembler for 16-bit mode?
>
> I haven't checked, but (a) this would be an independent change
> and (b) it would likely affect more than just the insns here
> (see e.g. other parts of the series).
>

Disassembler should be adjusted when IgnoreSize is added
to tpause and umwait.

-- 
H.J.
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