In pursuit of easy(er) JITs (invited talk)

n the early days of the Eclipse OMR project, we created the unimaginatively named JitBuilder API aiming to make it easier to build a JIT compiler. JitBuilder has been used to create prototype JIT compilers in a few thousand lines of C++ for WebAssembly, Lua, Smalltalk, Javascript, the Rosie Pattern Language, BF, Kaleidoscope, and Base9, as well as a number of other less language-centric dynamic code generators (including an alternative code generator for LLVM IR). Although it brings key facilities for privatizing virtual machine state and translating bytecode handlers, the JitBuilder API did not completely meet the “easy” goal particularly in the areas of extensibility and debuggability and did not offer strong DSL optimization possibilities. In this talk, I’ll explain and summarize the key features of the JitBuilder API before introducing some recent exploratory work to create the next version: JitBuilder2. This new fully-fledged (if currently in complete) compiler IL shares some directions with MLIR, but has some unique challenges and features, all designed around the pursuit of “easy” JIT compiler construction. Through the talk, I’ll show off some of these features (that’s right, I’ll demo a compiler IL!) and highlight some of the interesting directions I think we could take it from here.