Topic Overview

• High-level overview of LLVM & Clang
  • Will include how to get started coding on LLVM & Clang
  • Overview of core design elements, data structures, APIs, and patterns used in the codebase
  • High-level testing strategy for LLVM & Clang using tools like Clang’s ‘-verify’, opt, llc, FileCheck, and GoogleTest
  • Process of submitting a patch, code review, and community interactions
• How to add an optimization pass to LLVM
  • Tutorial on the LLVM IR both in the abstract and at the level of internal APIs
  • Basic APIs and data structures needed to implement, test, and wire a new pass into the compiler.
  • Overview of the relationship between transform and analysis passes.
  • Overview of the different kinds of transformation passes, how they interact, and what they can and can’t do
  • Actually add a transformation pass and an analysis pass to the compiler that depend on each other and exercise this machinery.
    • Includes authoring relevant tests for each component
• High-level overview of the architecture of an LLVM backend, with an emphasis on modifying or enhancing existing backends rather than adding a new one
  • Detailed review of where things are: from SelectionDAG to FastISel to the register allocator
  • Detailed review of exactly how a backend’s tablegen works, and how to make changes there and debug things
• Add a target-independent SelectionDAG combine to the code generator
  • Include detailed walk through of the relevant DAG combine interfaces.
• Add a target-specific DAG combine with special consideration of legalization
• Add support for a new instruction pattern to a backend
• Every bit of performance matters, and how the LLVM coding standard helps here