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 under the new pass manager.
- Writing an LLVM Pass (legacy PM version)
Information on how to write LLVM transformations and analyses under the legacy 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.
- Debug info migration: From intrinsics to records
This is a migration guide describing how to move from debug info using intrinsics such as dbg.value to using the non-instruction DbgRecord object.
- Instrumentation Profile Format
This document explains two binary formats of instrumentation-based profiles.
- InstCombine contributor guide
This document specifies guidelines for contributions for InstCombine and related passes.
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.
GlobalISel¶
- MIRPatterns
Describes the design of MIR Patterns and how to use them.
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.
- Support for AArch64 Scalable Matrix Extension in LLVM
LLVM’s support for AArch64 SME ACLE and ABI.
- 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.
- User Guide for RISC-V Target
This document describes using the RISC-V target.
- RISC-V Vector Extension
This document describes how the RISC-V Vector extension can be expressed in LLVM IR and how code is generated for it in the backend.
- Sandbox IR
This document describes the design and usage of Sandbox IR, a transactional layer over LLVM IR.