LLVM Language Reference Manual
Defines the LLVM intermediate representation and the assembly form of the different nodes.
LLVM Atomic Instructions and Concurrency Guide
Information about LLVM’s concurrency model.
Introduction to the general layout of the LLVM sourcebase, important classes and APIs, and some tips & tricks.
CommandLine 2.0 Library Manual
Provides information on using the command line parsing library.
Details the LLVM coding standards and provides useful information on writing efficient C++ code.
How to set up LLVM-style RTTI for your class hierarchy
How to make isa<>, dyn_cast<>, etc. available for clients of your class hierarchy.
Extending LLVM: Adding instructions, intrinsics, types, etc.
Look here to see how to add instructions and intrinsics to LLVM.
Architecture & Platform Information for Compiler Writers
A list of helpful links for compiler writers.