[llvm-commits] PATCH: Fix PR8528

[İsmail Dönmez]

On Sat, Nov 6, 2010 at 10:37 AM, İsmail Dönmez <ismail at namtrac.org> wrote:

> Hi Chris;
>
> On Sat, Nov 6, 2010 at 8:18 AM, Chris Lattner <clattner at apple.com> wrote:
>
>>
>> On Nov 3, 2010, at 3:54 PM, İsmail Dönmez wrote:
>>
>> Hi;
>>
>> Original patch by pdox on #llvm . Asm parser was not handling fist and
>> fistp instructions correctly. Please apply.
>>
>>
>> Hi Ismail,
>>
>> This is great detective work!  Just to verify my understanding, the issue
>> is that GAS is treating:
>>    fistp (%rax)
>> as an alias for:
>>   fistps (%rax)
>> and we're compiling it to:
>>   fistpl (%rax)
>>
>>
> You are correct.
>
>
>> If this is the case, I think that the MC assembler should be changed to
>> *reject* fisp, not to emulate GAS's behavior.  With a simple mem operand,
>> there is nothing to say that "4 bytes" is the right size of the store, it
>> should be diagnosed as an ambiguous instruction.  Reporting it as a bug in
>> the code is much more friendly than miscompiling it of course. :)
>>
>> What do you think?
>>
>
> I am no assembly expert but this seems to be another vague gas behaviour. I
> guess rejecting this is the correct behaviour indeed.
>

Also there is an existing alias for fstp, should that be removed also?

Regards,
ismail
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