non-standard machine value types

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1

Hi all.

I’m looking for a ways of defining register files with non-standard machine value type in tablegen. The value types not covered by SimpleValueType enum. For example (from the top of my head) 25 bit integers, or 8 way 18 bit integers. These types going to be used with intrinsics so I also need appropriate C custom types defined.

I wonder if I can describe those in tablegen files or do I need to extend llvm. What is the right way of supporting such types?

I’m not familiar will llvm internals so far, so any help and pointers appreciated.

Thanks,
Volodymyr.

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You would need an MVT type defined for every legal type you have, so you would need to add those. However, LLVM has a pretty widely spread assumption of 8-bit bytes, so that will be far more problematic for your target. Fixing that would be a large project.

-Matt

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We maintain a set of patches for enabling 24/40-bit MVTs, and also a set of patches to support 16-bit bytes. I can provide them upon request. (Only llvm, no clang patches yet.)

/Patrik Hägglund

4

Users can extend our architecture with own register files and own instructions. They are not limited to a narrow set of bit widths. I think, to support such extensions, I’ll need to handle MVTs dynamically. Perhaps, use standard MVTs whenever is possible and reserve a range for extensions.

Still, it’s interesting to see your set of 24/40-bit MVTs related patches, this might be a good example on how to extend MVTs. Is it publicly available?

Thanks,
Volodymyr.