The talk at the FOSDEM conference in 2023 was about building your own MLIR dialect. MLIR, or Multi-Level Intermediate Representation, is a compiler infrastructure introduced by Google in 2019 and later donated to the LLVM foundation. It is part of the LLVM project and allows developers to define operations, attributes, and types in dialects to create their own intermediate representation. The speaker demonstrated how to extend the standalone example in MLIR and build your own dialect, combine it with other dialects, and extend it with types and attributes. They also discussed the use of the LLVM external projects mechanism for building multiple dialects and mentioned various resources available for further learning. The talk also included a Q&A session where questions about using MLIR for front-end parsing and just-in-time compilation were addressed. Overall, the talk aimed to provide guidance and insights for developers interested in building their own MLIR dialect.