The vector dialect and related transformations are crucial components in the MLIR CodeGen flow for machine learning (ML). Today I will zoom in on it to explain its positioning in the overall picture, characteristics, important operations and transformations, and best practices of using it based on my experiences.
The initial blog post in this series captured my overall take on the evolution trends of compilers and IRs. It also touched on LLVM IR, SPIR-V, and MLIR, explaining the problems they are addressing and design focuses thereof. Today I will expand on MLIR and talk about its dialect hierarchy for machine learning (ML) compilers systematically.
Compilers are often critical components in various development toolchains that boosts developer productivity. A compiler is normally used as a monolithic black box that consumes a high-level source program and produces a semantically-equivalent low-level one. It is still structured inside though; what flows between internal layers are called intermediate representations (IRs). IRs are critical to compilers. Like there are many compilers, there are also many IRs in use. I’m fortunate to have direct experience with three major schools of IRs or infrastructures thus far—LLVM IR, SPIR-V, MLIR, particularly extensively for the last two, where I both joined development in an early stage. So I’d like to write a series of blog posts to log down my understanding of compilers and IRs. Hopefully it could be beneficial to others.
This blog post talks about how to generate performant code for convolution ops using MLIR’s multiple levels of abstractions and transformations. I initially created it for targeting ARM Mali GPUs in IREE. But given it is just direct tiling and vectorization, it should be widely applicable. I will walk through the lowering steps, so if you are interested to know how to organize MLIR’s various dialects/patterns together to achieve similar tasks, this blog post might also be useful.