Building a JIT: Extreme Laziness - Using Compile Callbacks to JIT from ASTs

This tutorial is under active development. It is incomplete and details may change frequently. Nonetheless we invite you to try it out as it stands, and we welcome any feedback.

Chapter 4 Introduction

Welcome to Chapter 4 of the "Building an ORC-based JIT in LLVM" tutorial. This chapter introduces the Compile Callbacks and Indirect Stubs APIs and shows how they can be used to replace the CompileOnDemand layer from Chapter 3 with a custom lazy-JITing scheme that JITs directly from Kaleidoscope ASTs.

To be done:

(1) Describe the drawbacks of JITing from IR (have to compile to IR first, which reduces the benefits of laziness).

(2) Describe CompileCallbackManagers and IndirectStubManagers in detail.

(3) Run through the implementation of addFunctionAST.

Full Code Listing

Here is the complete code listing for our running example that JITs lazily from Kaleidoscope ASTS. To build this example, use:

# Compile
clang++ -g toy.cpp `llvm-config --cxxflags --ldflags --system-libs --libs core orcjit native` -O3 -o toy
# Run
./toy

Here is the code:

Next: Remote-JITing -- Process-isolation and laziness-at-a-distance