[PATCH v3 03/10] x86: move certain MOVSX/MOVZX tests

[Jan Beulich]

On 13.01.2020 18:33,  H.J. Lu  wrote:
> On Fri, Dec 27, 2019 at 1:24 AM Jan Beulich <JBeulich@suse.com> wrote:
>>
>> Some encodings are about to gain a warning - move them from test cases
>> not expecting any diagnostics to the new, dedicated ones, to allow
>> better focus on the actual changes in the subsequent patch.
>>
>> The new tests added have some wrong expectations right now, which will
>> be corrected by the next patch. The test is being added here to make
>> more visible which cases actually were wrong (and hence get changed),
>> besides demonstrating that in the vast majority of cases the subsequent
>> change doesn't alter generated code.
> 
> We can't change the encoding nor disallow it.  At most, we can issue a
> warning.   If it is the case, calling it "wrong" isn't accurate.

If you look at the following patch you'll find that the two cases
where an encoding actually changes, this will then be accompanied
by a warning. I don't see why disallowing an insn which we've
mistakenly accepted so far wouldn't be permitted. How would we
ever fix any bugs involving e.g. mis-parsing of operands, or
wrongly coded insn templates. By there then being an error, it'll
be quite clear what needs changing on the source side. I'm also
pretty sure that such has happened quite a few times in the past.

Jan