Support Union values in shfl-based kernel

[tkf]

No description provided.

[codecov]

Codecov Report

Merging #80 (29d0a77) into master (5aab516) will decrease coverage by 4.08%.
The diff coverage is 17.80%.

@@            Coverage Diff             @@
##           master      #80      +/-   ##
==========================================
- Coverage   48.52%   44.44%   -4.09%     
==========================================
  Files           3        4       +1     
  Lines         305      369      +64     
==========================================
+ Hits          148      164      +16     
- Misses        157      205      +48     

Flag	Coverage Δ
Pkg.test-cpu	?
Run.test-cpu	0.00% <0.00%> (ø)

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Impacted Files	Coverage Δ
src/api.jl	90.00% <ø> (ø)
src/kernels.jl	48.44% <0.00%> (-0.92%)	⬇️
src/unionvalues.jl	18.18% <18.18%> (ø)
src/shfl.jl	46.85% <21.42%> (+2.32%)	⬆️

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[tkf]

julia> xs = CUDA.ones(2^30);

julia> @btime sum(xs);
  7.057 ms (1764 allocations: 29.72 KiB)

julia> @btime Folds.sum(xs);
  160.098 ms (78557 allocations: 1.20 MiB)

julia> @btime Folds.sum(xs, CoalescedCUDAEx(); init = 0.0f0);
  8.192 ms (3038 allocations: 50.98 KiB)