Sparse tensor lowering to GPU

[jim22k]

Looks like @aartbik has been working on this in stealth mode

Sparse Compiler and GPU Code-Generation

It is time to continue the older sparse compiler thread into a new topical thread. Even though the MLIR sparse compiler is obviously meant as a re-targetable tool to exploit sparsity, most development so far has been focused on generating sparse code that runs on a CPU. Even though CPUs are least used for ML problems, having the ability to easily exploit unstructured sparsity still makes this a viable approach for accelerating sparse problems with very high sparsities. Recently, however, we s…