https://stackoverflow.com/a/43456211/1544203 https://stackoverflow.com/a/43456211/1544203 is a little old, but still very much relevant. Julia has an untyped IR

https://stackoverflow.com/a/43456211/1544203 https://stackoverflow.com/a/43456211/1544203 is a little old, but still very much relevant. Julia has an untyped IR that it lowers into, then typed IR on which inference is performed, then it lowers to LLVM which lowers it to native. You can introspect the IR at these steps by taking a function call and doing `@code_lowered`, `@code_typed`, `@code_llvm`, and `@code_native`. For some examples, the compiler plugins interface acts on typed IR, so things like Diffractor for automatic differentiation or JET static analysis and EscapeAnalysis.jl act there. Notably, Zygote automatic differentiation acted on the untyped IR. GPUCompiler.jl does some operations on the typed IR then lowers to the LLVM IR level and then intercepts the normal compilation process to choose alternative backends (e.g. compile to .ptx for compilation of native Julia to CUDA). Enzyme.jl uses the Enzyme LLVM-based automatic differentiation, so it does some actions on the typed IR before lowering to LLVM and then injecting the Enzyme LLVM pass before compiling via GPUCompiler.jl (now to the normal CPU backend).