[PATCH] x86: Don't display eiz with no scale

[H.J. Lu]

On Tue, Jul 21, 2020 at 7:01 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Tue, Jul 21, 2020 at 5:22 AM Jan Beulich <jbeulich@suse.com> wrote:
> >
> > On 21.07.2020 13:29, H.J. Lu wrote:
> > > On Tue, Jul 21, 2020 at 2:40 AM Jan Beulich <jbeulich@suse.com> wrote:
> > >>
> > >> On 15.07.2020 15:57, H.J. Lu wrote:
> > >>> On Tue, Jul 14, 2020 at 11:14 PM Jan Beulich <jbeulich@suse.com> wrote:
> > >>>>
> > >>>> On 14.07.2020 18:54, H.J. Lu wrote:
> > >>>>> On Tue, Jul 14, 2020 at 5:55 AM H.J. Lu <hjl.tools@gmail.com> wrote:
> > >>>>>>
> > >>>>>> On Tue, Jul 14, 2020 at 5:51 AM Jan Beulich <jbeulich@suse.com> wrote:
> > >>>>>>>
> > >>>>>>> On 14.07.2020 14:43, H.J. Lu wrote:
> > >>>>>>>> On Mon, Jul 13, 2020 at 11:12 PM Jan Beulich <jbeulich@suse.com> wrote:
> > >>>>>>>>> Nevertheless, I've meanwhile thought of a (contrived) case that was
> > >>>>>>>>> broken with the code present:
> > >>>>>>>>>
> > >>>>>>>>>         addr32 mov $0x89abcdef, %rax
> > >>>>>>>>>
> > >>>>>>>>> would have got the immediate sign-extended from 32 to 64 bits.
> > >>>>>>>>>
> > >>>>>>>>
> > >>>>>>>> I opened:
> > >>>>>>>>
> > >>>>>>>> https://sourceware.org/bugzilla/show_bug.cgi?id=26237
> > >>>>>>>>
> > >>>>>>>> There are multiple issues.
> > >>>>>>>
> > >>>>>>> Hmm, the former two lines there look correct to me, while the latter
> > >>>>>>> two lines look to have been translated with a gas that didn't have
> > >>>>>>> yesterday's change yet. IOW - I'm somewhat confused.
> > >>>>>>
> > >>>>>> The bug is against binutils 2.35, not master.
> > >>>>>>
> > >>>>>
> > >>>>> Here is the patch for master branch.
> > >>>>
> > >>>> Ah, so your issue was just with disassembly. Yet then why not go a step
> > >>>> further and (at least in 64-bit mode) print
> > >>>>
> > >>>> [       ]*[a-f0-9]+:    67 48 89 1c 25 ef cd ab 89      mov[ ]+%rbx,0x89abcdef
> > >>>> [       ]*[a-f0-9]+:    67 89 04 25 11 22 33 ff         mov[ ]+%eax,0xff332211
> > >>>>
> > >>>> instead of
> > >>>>
> > >>>> [       ]*[a-f0-9]+:    67 48 89 1c 25 ef cd ab 89      mov[ ]+%rbx,0x89abcdef\(,%eiz,1\)
> > >>>> [       ]*[a-f0-9]+:    67 89 04 25 11 22 33 ff         mov[ ]+%eax,0xff332211\(,%eiz,1\)
> > >>>>
> > >>>> and keep the () part only for
> > >>>>
> > >>>> [       ]*[a-f0-9]+:    67 89 04 65 11 22 33 ff         mov[ ]+%eax,0xff332211\(,%eiz,2\)
> > >>>>
> > >>>> , as there's no SIB-less way to express a base-and-index-less address?
> > >>>>
> > >>>
> > >>> Done.
> > >>>
> > >>> I am checking in this.
> > >>
> > >> Having only now noticed the collision with my change to
> > >> evex-no-scale-64.d, I wonder whether we want to revert your change,
> > >> and hence whether my underlying suggestion was a bad one: There's
> > >> now no sign left that these insns use 32-bit address mode. The
> > >> alternative would be to ensure that an addr32 prefix gets emitted.
> > >> I'd personally favor this alternative, but I could live with the
> > >> revert. (When making the suggestion I didn't realize this is a
> > >> 32-bit-addressing-specific output mode.)
> > >>
> > >
> > > Can you revert it for me?
> >
> > Done.
>
> Thanks.

I am backporting it to 2.35 branch.


-- 
H.J.