[mlir][spirv] Support abbreviated SPIR-V type format

[kuhar]

We can elide the leading dialect prefix when dealing with nested SPIR-V types, e.g.: !spirv.ptr<!spirv.array<...>> ==> !spirv.ptr<array<...>>.

The abbreviated format should support arbitrary nesting of SPIR-V types.

[llvmbot]

@llvm/issue-subscribers-mlir-spirv

[llvmbot]

Hi!

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[llvmbot]

@llvm/issue-subscribers-good-first-issue

Author: Jakub Kuderski (kuhar)

We can elide the leading dialect prefix when dealing with nested SPIR-V types, e.g.: `!spirv.ptr<!spirv.array<...>>` ==> `!spirv.ptr<array<...>>`. The abbreviated format should support arbitrary nesting of SPIR-V types.

[kuhar]

Update: I looked at this at some point and this would require writing a bunch of custom parsing/printing code similar to the llvm dialect. There was a proposal presented during the US LLVM Dev / MLIR summit to allow these abbreviated formats in a more general way. I can't find the abstract now, maybe someone like @ftynse or @jpienaar know what I'm talking about.

I think we should put this issue on hold until this generic support in MLIR is in place.