Even when not using LLVM, Jai still does "codegen twice." Most compilers today (even JITs) have at least one IR in between the syntax tree and the generated cod

Even when not using LLVM, Jai still does "codegen twice." Most compilers today (even JITs) have at least one IR in between the syntax tree and the generated code. The existence of LLVM IR is not the problem- rather, it's how it gets used (on both sides of the API). Generating a lot of naive IR and letting the optimizer clean it up, for example, has a large cost. And, while I'm not too up to date on the details of Jai, the last thing I heard it was still very fast to compile even in release builds that did use LLVM. That is, the Jai compiler is smarter about how it generates IR.