transformations: (csl-stencil-bufferize) Fold csl_stencil.access that have no effect

[n-io]

The csl-stencil-bufferize pass lowers stencil.field and tensor types to memref.

The type conversion pass creates the scenario that some csl_stencil.access ops are equal input and output types, for instance, (memref<512xf32>) -> memref<512xf32>. This only happens for ops accessing own data. In this case, the access op has no effect and can safely be folded away.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.89%. Comparing base (04fcab7) to head (23306ff).
Report is 16 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3084      +/-   ##
==========================================
- Coverage   89.90%   89.89%   -0.01%     
==========================================
  Files         418      418              
  Lines       52914    52918       +4     
  Branches     8204     8205       +1     
==========================================
+ Hits        47571    47572       +1     
- Misses       4017     4019       +2     
- Partials     1326     1327       +1     

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[dk949]

LGTM, but I'm not 100% sure this is the right place to do this transformation. This rewrite ends up either transforming the access or converting it to a to_tensor

[n-io]

It only folds accesses that have no effect.