[fuhsnn]

Looks like this is implemented with LLVM's builtin matrix type, also available as a Clang extension: https://clang.llvm.org/docs/MatrixTypes.html

[gingerBill]

Actually we implement it manually ourselves the exact same way that the extensions work. This is because we have to support multiple different versions of LLVM which don't have those extensions.

[fuhsnn]

Thanks for clarifying!