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Hacking on Clang

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This document provides some hints for how to get started hacking + on Clang for developers who are new to the Clang and/or LLVM + codebases. +

Developer Documentation
Debugging
LLVM IR Generation

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Developer Documentation

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Both Clang and LLVM use doxygen to provide API documentation. Their + respective web pages (generated nightly) are here: +

Clang
LLVM

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For work on the LLVM IR generation, the LLVM assembly language + reference manual is + also useful.

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Debugging

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Inspecting data structures in a debugger: +

Many LLVM and Clang data structures provide + a dump() method which will print a description of the + data structure to stderr.
The QualType + structure is used pervasively. This is a simple value class for + wrapping types with qualifiers; you can use + the isConstQualified(), for example, to get one of the + qualifiers, and the getTypePtr() method to get the + wrapped Type* which you can then dump.

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LLVM IR Generation

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The LLVM IR generation part of clang handles conversion of the + AST nodes output by the Sema module to the LLVM Intermediate + Representation (IR). Historically, this was referred to as + "codegen", and the Clang code for this lives + in lib/CodeGen.

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The output is most easily inspected using the -emit-llvm + option to clang (possibly in conjunction with -o -). You + can also use -emit-llvm-bc to write an LLVM bitcode file + which can be processed by the suite of LLVM tools + like llvm-dis, llvm-nm, etc. See the LLVM + Command Guide + for more information.

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