User Guides — LLVM 19.1.7 documentation

# 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 RISCV-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.