[PATCH] x86-64: Zero-extend lower 32 bits displacement to 64 bits

[Jan Beulich]

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?

Jan