Reference — LLVM 22.1.1 documentation

# Reference

LLVM and API reference documentation.

## API Reference

Doxygen generated documentation

  (classes)

How To Use Attributes

  Answers some questions about the new Attributes infrastructure.

## LLVM Reference

### Command Line Utilities

LLVM Command Guide

  A reference manual for the LLVM command line utilities (“man” pages for LLVM tools).

LLVM bugpoint tool: design and usage

  Automatic bug finder and test-case reducer description and usage information.

Using -opt-bisect-limit to debug optimization errors

  A command line option for debugging optimization-induced failures.

Symbolizer Markup Format

  A reference for the log symbolizer markup accepted by `llvm-symbolizer`.

The Microsoft PDB File Format

  A detailed description of the Microsoft PDB (Program Database) file format.

### Garbage Collection

Garbage Collection with LLVM

  The interfaces source-language compilers should use for compiling GC’d programs.

Garbage Collection Safepoints in LLVM

  This describes a set of experimental extensions for garbage collection support.

### LibFuzzer

libFuzzer – a library for coverage-guided fuzz testing.

  A library for writing in-process guided fuzzers.

Fuzzing LLVM libraries and tools

  Information on writing and using Fuzzers to find bugs in LLVM.

### LLVM IR

LLVM Language Reference Manual

  Defines the LLVM intermediate representation and the assembly form of the different nodes.

Undefined Behavior (UB)

  A guide on what UB/undef/poison are and when to use each one.

Design and Usage of the InAlloca Attribute

  Description of the `inalloca` argument attribute.

LLVM Bitcode File Format

  This describes the file format and encoding used for LLVM “bc” files.

Machine IR (MIR) Format Reference Manual

  A reference manual for the MIR serialization format, which is used to test LLVM’s code generation passes.

Global Instruction Selection

  This describes the prototype instruction selection replacement, GlobalISel.

Convergent Operation Semantics

  Description of `convergent` operation semantics and related intrinsics.

### Testing and Debugging

LLVM Testing Infrastructure Guide

  A reference manual for using the LLVM testing infrastructure.

test-suite Guide

  Describes how to compile and run the test-suite benchmarks.

GWP-ASan

  A sampled heap memory error detection toolkit designed for production use.

### XRay

XRay Instrumentation

  High-level documentation of how to use XRay in LLVM.

Debugging with XRay

  An example of how to debug an application with XRay.

### Additional Topics

FaultMaps and implicit checks

  LLVM support for folding control flow into faulting machine instructions.

LLVM Atomic Instructions and Concurrency Guide

  Information about LLVM’s concurrency model.

Exception Handling in LLVM

  This document describes the design and implementation of exception handling in LLVM.

LLVM Extensions

  LLVM-specific extensions to tools and formats LLVM seeks compatibility with.

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.

LLVM Block Frequency Terminology

  Provides information about terminology used in the `BlockFrequencyInfo` analysis pass.

LLVM Branch Weight Metadata

  Provides information about Branch Prediction Information.

The Often Misunderstood GEP Instruction

  Answers to some very frequent questions about LLVM’s most frequently misunderstood instruction.

Scudo Hardened Allocator

  A library that implements a security-hardened malloc().

Memory Model Relaxation Annotations

  Target-defined relaxation to LLVM’s concurrency model.

MemTagSanitizer

  Security hardening for production code aiming to mitigate memory related vulnerabilities. Based on the Armv8.5-A Memory Tagging Extension.

Dependence Graphs

  A description of the design of the various dependence graphs such as the DDG (Data Dependence Graph).

Speculative Load Hardening

  A description of the Speculative Load Hardening mitigation for Spectre v1.

Segmented Stacks in LLVM

  This document describes segmented stacks and how they are used in LLVM.

LLVM’s Optional Rich Disassembly Output

  This document describes the optional rich disassembly output syntax.

Stack maps and patch points in LLVM

  LLVM support for mapping instruction addresses to the location of values and allowing code to be patched.

Coroutines in LLVM

  LLVM support for coroutines.

Pointer Authentication

  A description of pointer authentication, its LLVM IR representation, and its support in the backend.

YAML I/O

  A reference guide for using LLVM’s YAML I/O library.

Convergence And Uniformity

  A description of uniformity analysis in the presence of irreducible control flow, and its implementation.

Machine Learning - Guided Optimization (MLGO)

  Facilities for ML-Guided Optimization, such as collecting IR corpora from a build, interfacing with ML models, an exposing features for training.

Content Addressable Storage

  A reference guide for using LLVM’s CAS library.

LLVM CI Best Practices

  A list of guidelines and best practices to use when working on LLVM’s CI systems.