Comment for EXTRACT_VECTOR_ELT

[Hal Finkel via llvm-commits]

On 01/24/2017 07:14 AM, Jonas Paulsson wrote:
>
>>>
>>>
>>>> Hi,
>>>>
>>>> I would like to see the comment for EXTRACT_VECTOR_ELT in 
>>>> ISDOpcodes.h clarified. Is my patch correct in assuming that an 
>>>> any-extend is allowed?
>>
>> Given that it says just 'extended' currently, without specifying how, 
>> I don't see how the proposed wording is semantically different. If 
>> you want to make this clearer, you'll need to say explicitly that the 
>> high bits are undefined.
>>
>>  -Hal
>
> I was kind of expecting to have the extend operation explicitly 
> described, although I certainly also would guess 'any-ext'. I am fine 
> with your wording as well -- see attachement. Is it ok? /Jonas

I think that we need to make it clear that the statement is only 
associated with the extension case. I'd word it as: "In that case, the 
high bits are undefined."

  -Hal


-- 
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory