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===========================================================================
Building a JIT: Extreme Laziness - Using Compile Callbacks to JIT from ASTs
===========================================================================
.. contents::
:local:
**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 <BuildingAJIT3.html>`_ 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:
.. code-block:: bash
# Compile
clang++ -g toy.cpp `llvm-config --cxxflags --ldflags --system-libs --libs core orcjit native` -O3 -o toy
# Run
./toy
Here is the code:
.. literalinclude:: ../../examples/Kaleidoscope/BuildingAJIT/Chapter4/KaleidoscopeJIT.h
:language: c++
`Next: Remote-JITing -- Process-isolation and laziness-at-a-distance <BuildingAJIT5.html>`_
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