[LLVMdev] loop vectorizer and storing to uniform addresses

[Nadav Rotem]

Can you attach the incoming IR ?

Yes, we support reductions:   http://llvm.org/docs/Vectorizers.html




On Nov 7, 2013, at 5:18 PM, Frank Winter <fwinter at jlab.org> wrote:

> I am trying my luck on this global reduction kernel:
> 
> float foo( int start , int end , float * A  )
> {
>  float sum[4] = {0.,0.,0.,0.};
>  for (int i = start ; i < end ; ++i ) {
>    for (int q = 0 ; q < 4 ; ++q )
>      sum[q] += A[i*4+q];
>  }
>  return sum[0]+sum[1]+sum[2]+sum[3];
> }
> 
> 
> LV: Checking a loop in "foo"
> LV: Found a loop: for.cond1
> LV: Found an induction variable.
> LV: We don't allow storing to uniform addresses
> LV: Can't vectorize due to memory conflicts
> LV: Not vectorizing.
> 
> 
> My interpretation would be that the loop vectorizer does not support loops which implement a reduction. Is this correct?
> 
> Frank
> 
> 
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev