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Re: [PATCH 1/4] x86: correctly encode FSUBP
>>> On 07.03.18 at 13:39, <hjl.tools@gmail.com> wrote:
> On Wed, Mar 7, 2018 at 4:36 AM, Jan Beulich <JBeulich@suse.com> wrote:
>>>>> On 07.03.18 at 13:30, <hjl.tools@gmail.com> wrote:
>>> On Wed, Mar 7, 2018 at 1:47 AM, Jan Beulich <JBeulich@suse.com> wrote:
>>>> While the combination of Intel syntax and AT&T mnemonics is bogus
>>>> anyway, we nevertheless shouldn't mis-encode such insns.
>>>>
>>>> gas/
>>>> 2018-03-07 Jan Beulich <jbeulich@suse.com>
>>>>
>>>> * testsuite/gas/i386/fsubp.l, testsuite/gas/i386/fsubp.s: New.
>>>> * testsuite/gas/i386/i386.exp: Run new test.
>>>>
>>>> opcodes/
>>>> 2018-03-07 Jan Beulich <jbeulich@suse.com>
>>>>
>>>> * i386-opc.tbl (fsubp): Correct encoding.
>>>> * i386-tlb.h: Re-generate.
>>>>
>>>
>>> I assume that no one uses it. Can't we simply drop it?
>>
>> I don't know, and would dare to chance it. But perhaps you know
>> better than me. Of course, if we drop this one, there are others to
>> be dropped at the same time.
>
> We are changing their encodings. If we can't drop them, it means
> that someone is depending on their old encodings.
Well, no, not exactly: If we do as you suggest, we should remove
more than just this broken encoding. People may use some of the
others, or may have happened to use the one here only with odd
numbered registers. But again - I'm not entirely opposed to dropping
the whole OldGcc logic, it's just that (at least at this point in time) it's
not going to be me to do it. Hence rather than leaving things broken,
I'd prefer to fix them. (As a side note, patch 3 and maybe also patch
4 of this series would probably need changing, just like a number of
existing test cases.)
Jan