[mlir][tensor] Enhance tensor.pad result shape deduction

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Summary

This is a preliminary pattern to expose static information to enable
further transformations on tensor.pad like vectorization.

Depends On D117019

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Rebase

[mravishankar]

mlir/lib/Dialect/Linalg/Transforms/Transforms.cpp

957 ↗

(On Diff #406204)

I am not sure we want to do it this way. This is effectively shape propagation. This is explicitly why this interface is for https://github.com/llvm/llvm-project/blob/5a7235769717eb7f0046465e823f93f110478710/mlir/include/mlir/Interfaces/InferTypeOpInterface.td#L151 .

You should be able to get that trigger with this pass https://github.com/llvm/llvm-project/blob/5a7235769717eb7f0046465e823f93f110478710/mlir/include/mlir/Dialect/MemRef/Transforms/Passes.td#L148 . Is this not working?

[antiagainst]

mlir/lib/Dialect/Linalg/Transforms/Transforms.cpp

957 ↗

(On Diff #406204)

No, it's not covering the case I want to handle here. I can move this pattern to also use the above interface if that's better.

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Address comments