llvm dev - Jan 2014 - [LLVMdev] Gather load in LLVM IR

Hi All,
I was in the process of implementing a gathering load for my language.  
I got the getelementptr vector form working.  However there doesn't seem 
to be a way to load a vector of values using the vector of pointers from 
getelementptr.  Am I correct that this is not possible with LLVM IR 
currently (apart from with the avx2 gather intrinsic)?

And if so, are there plans to allow loading of a vector of values?

I think extending the load instruction to take a vector of pointers (as 
would be produced by getelementptr) would work well.

Thanks,
     Nick C.

On Jan 14, 2014, at 11:11 AM, Nicholas Chapman <admin at
indigorenderer.com> wrote:
> Hi All,
> I was in the process of implementing a gathering load for my language.  I
got the getelementptr vector form working.  However there doesn't seem to be
a way to load a vector of values using the vector of pointers from
getelementptr.  Am I correct that this is not possible with LLVM IR currently
(apart from with the avx2 gather intrinsic)?
I believe you are correct. This is not currently possible.
> 
> And if so, are there plans to allow loading of a vector of values?
> 
> I think extending the load instruction to take a vector of pointers (as
would be produced by getelementptr) would work well.
This is of interests to a lot of people and I think it's a reasonable time
to start the discussion. Do you have any concrete proposal in mind?

Evan
> 
> Thanks,
>    Nick C.
> 
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

Hi Evan, all,
The most obvious thing to me would be to extend the load instruction to 
have an additional form that takes a vector of pointers instead of a 
single pointer.
This form would return a vector of values instead of a single value.
If a gather instruction is not available on the target, then the load 
could be lowered to a series of scalar loads and insertelements.

Thanks,
     Nick

On 20/01/2014 5:59 p.m., Evan Cheng wrote:
> On Jan 14, 2014, at 11:11 AM, Nicholas Chapman <admin at
indigorenderer.com> wrote:
>
>> Hi All,
>> I was in the process of implementing a gathering load for my language. 
I got the getelementptr vector form working.  However there doesn't seem to
be a way to load a vector of values using the vector of pointers from
getelementptr.  Am I correct that this is not possible with LLVM IR currently
(apart from with the avx2 gather intrinsic)?
> I believe you are correct. This is not currently possible.
>
>> And if so, are there plans to allow loading of a vector of values?
>>
>> I think extending the load instruction to take a vector of pointers (as
would be produced by getelementptr) would work well.
> This is of interests to a lot of people and I think it's a reasonable
time to start the discussion. Do you have any concrete proposal in mind?
>
> Evan
>
>> Thanks,
>>     Nick C.
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev