[BUG]: Tuning policy will not be selected properly for CUB Merge Sort

[NaderAlAwar]

Is this a duplicate?

• I confirmed there appear to be no duplicate issues for this bug and that I agree to the Code of Conduct

Type of Bug

Something else

Component

CUB

Describe the bug

The dynamic dispatch PR for Merge Sort #3525 introduced a bug into how the tuning policy is selected. By making VSMemHelper a template of the DispatchMergeSort class that is instantiated with typename PolicyHub::MaxPolicy::MergeSortPolicy, this PR changed the original behavior, where we were instantiating it with the ActivePolicy passed from Invoke(), which would have selected the correct tuning policy. See this comment as well #3525 (comment).

How to Reproduce

There are differences in the SASS for pre-Pascal architectures before and after applying the changes in this PR.

Expected behavior

VSMemHelper should be instantiated with the correct policy.

Reproduction link

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Operating System

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nvidia-smi output

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NVCC version

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