User Guides¶
NOTE: If you are a user who is only interested in using an LLVM-based compiler, you should look into Clang instead. The documentation here is intended for users who have a need to work with the intermediate LLVM representation.
Clang¶
- How To Build On ARM
Notes on building and testing LLVM/Clang on ARM.
- How To Build Clang and LLVM with Profile-Guided Optimizations
Notes on building LLVM/Clang with PGO.
- How To Cross-Compile Clang/LLVM using Clang/LLVM
Notes on cross-building and testing LLVM/Clang.
- How to build the C, C++, ObjC, and ObjC++ front end
Instructions for building the clang front-end from source.
- LLVM Code Coverage Mapping Format
This describes the format and encoding used for LLVM’s code coverage mapping.
- Control Flow Verification Tool Design Document
A description of the verification tool for Control Flow Integrity.
LLVM Builds and Distributions¶
- Building a Distribution of LLVM
A best-practices guide for using LLVM’s CMake build system to package and distribute LLVM-based tools.
- Building LLVM with CMake
An addendum to the main Getting Started guide for those using the CMake build system.
- A guide to Dockerfiles for building LLVM
A reference for using Dockerfiles provided with LLVM.
- Support Library
This document describes the LLVM Support Library (
lib/Support) and how to keep LLVM source code portable.- Advanced Build Configurations
This document describes more advanced build configurations.
Optimizations¶
- Writing an LLVM Pass
Information on how to write LLVM transformations and analyses.
- Writing an LLVM Pass
Information on how to write LLVM transformations under the new pass manager.
- LLVM’s Analysis and Transform Passes
A list of optimizations and analyses implemented in LLVM.
- Stack Safety Analysis
This document describes the design of the stack safety analysis of local variables.
- MergeFunctions pass, how it works
Describes functions merging optimization.
- LLVM Alias Analysis Infrastructure
Information on how to write a new alias analysis implementation or how to use existing analyses.
- MemorySSA
Information about the MemorySSA utility in LLVM, as well as how to use it.
- LLVM Loop Terminology (and Canonical Forms)
A document describing Loops and associated terms as used in LLVM.
- LLVM Cycle Terminology
A document describing cycles as a generalization of loops.
- Auto-Vectorization in LLVM
This document describes the current status of vectorization in LLVM.
- LLVM Link Time Optimization: Design and Implementation
This document describes the interface between LLVM intermodular optimizer and the linker and its design
- The LLVM gold plugin
How to build your programs with link-time optimization on Linux.
- Remarks
A reference on the implementation of remarks in LLVM.
- Source Level Debugging with LLVM
This document describes the design and philosophy behind the LLVM source-level debugger.
- How to Update Debug Info
This document specifies how to correctly update debug info in various kinds of code transformations.
- Instruction referencing for debug info
This document explains how LLVM uses value tracking, or instruction referencing, to determine variable locations for debug info in the final stages of compilation.
Code Generation¶
- Writing an LLVM Backend
Information on how to write LLVM backends for machine targets.
- The LLVM Target-Independent Code Generator
The design and implementation of the LLVM code generator. Useful if you are working on retargetting LLVM to a new architecture, designing a new codegen pass, or enhancing existing components.
- TableGen
Describes the TableGen tool, which is used heavily by the LLVM code generator.
JIT¶
- MCJIT Design and Implementation
Describes the inner workings of MCJIT execution engine.
- ORC Design and Implementation
Describes the design and implementation of the ORC APIs, including some usage examples, and a guide for users transitioning from ORCv1 to ORCv2.
- JITLink and ORC’s ObjectLinkingLayer
Describes the design and APIs for the JITLink library, ORC’s new JIT linker.
- Debugging JIT-ed Code
How to debug JITed code with GDB.
How to debug JITed code with GDB.
Additional Topics¶
- CommandLine 2.0 Library Manual
Provides information on using the command line parsing library.
- Extending LLVM: Adding instructions, intrinsics, types, etc.
Look here to see how to add instructions and intrinsics to LLVM.
- How To Add A Constrained Floating-Point Intrinsic
Gives the steps necessary when adding a new constrained math intrinsic to LLVM.
- How to build Windows Itanium applications.
Notes on assembling a Windows Itanium environment.
- How to Cross Compile Compiler-rt Builtins For Arm
Notes on cross-building and testing the compiler-rt builtins for Arm.
- Using ARM NEON instructions in big endian mode
LLVM’s support for generating NEON instructions on big endian ARM targets is somewhat nonintuitive. This document explains the implementation and rationale.
- Compiling CUDA with clang
LLVM support for CUDA.
- User Guide for NVPTX Back-end
This document describes using the NVPTX backend to compile GPU kernels.
- User Guide for AMDGPU Backend
This document describes using the AMDGPU backend to compile GPU kernels.
- DWARF Extensions For Heterogeneous Debugging
This document describes DWARF extensions to support heterogeneous debugging for targets such as the AMDGPU backend.
- Allow Location Descriptions on the DWARF Expression Stack
This document describes a DWARF extension to allow location descriptions on the DWARF expression stack. It is part of DWARF Extensions For Heterogeneous Debugging.
- User Guide for SPIR-V Target
This document describes using the SPIR-V target to compile GPU kernels.
- User Guide for the DirectX Target
This document describes using the DirectX target to compile GPU code for the DirectX runtime.