himank-test/tessl-llvm

LLVM 22.x tile for building compilers, language runtimes, and out-of-tree tooling

1.23x

Quality

83%

Does it follow best practices?

Impact

96%

1.23x

Average score across 5 eval scenarios

Securityby

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Out-of-Tree LLVM 22 Projects — CMake Setup & Linking

Name: himank-test/tessl-llvm
Rating: 88.21 (1 reviews)
Author: himank-test

Reference: Building LLVM with CMake | llvm-config

When to build out-of-tree

Build out-of-tree (against an installed LLVM) when you are:

Writing a standalone compiler frontend or language runtime
Developing a pass plugin loadable by opt --load-pass-plugin
Building tooling (e.g., a static analyzer, refactoring tool) on top of LLVM

Build in-tree (inside the LLVM source tree) when you are:

Adding a new target backend
Adding in-tree passes, intrinsics, or IR changes
Contributing to LLVM upstream

Installing LLVM 22

# macOS (Homebrew)
brew install llvm@22
# Headers: /opt/homebrew/opt/llvm@22/include
# CMake:   /opt/homebrew/opt/llvm@22/lib/cmake/llvm

# Ubuntu / Debian
apt install llvm-22-dev libclang-22-dev
# Headers: /usr/lib/llvm-22/include
# CMake:   /usr/lib/llvm-22/lib/cmake/llvm

# Build from source
cmake -S llvm -B build \
  -DCMAKE_BUILD_TYPE=Release \
  -DCMAKE_INSTALL_PREFIX=/usr/local/llvm-22 \
  -DLLVM_TARGETS_TO_BUILD="X86;AArch64;RISCV" \
  -DLLVM_ENABLE_PROJECTS="clang" \
  -G Ninja
ninja -C build install

Locate the cmake config directory:

llvm-config-22 --cmakedir
# /usr/lib/llvm-22/lib/cmake/llvm

Minimal CMakeLists.txt

cmake_minimum_required(VERSION 3.20)
project(MyCompiler CXX)

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)
set(CMAKE_EXPORT_COMPILE_COMMANDS ON)

# ── Locate LLVM 22 ────────────────────────────────────────────────────────────
find_package(LLVM 22 REQUIRED CONFIG)
message(STATUS "LLVM version: ${LLVM_PACKAGE_VERSION}")
message(STATUS "LLVM CMake dir: ${LLVM_DIR}")

include_directories(${LLVM_INCLUDE_DIRS})
separate_arguments(LLVM_DEFINITIONS_LIST NATIVE_COMMAND ${LLVM_DEFINITIONS})
add_definitions(${LLVM_DEFINITIONS_LIST})

# ── Map LLVM components to link targets ───────────────────────────────────────
llvm_map_components_to_libnames(LLVM_LIBS
  Core          # LLVMContext, Module, IRBuilder, basic types
  Support       # raw_ostream, StringRef, Error, CommandLine
  Analysis      # DominatorTree, ScalarEvolution, AliasAnalysis
  Passes        # PassBuilder, NPM infrastructure
  IRReader      # parseIRFile, parseAssemblyString
  BitWriter     # WriteBitcodeToFile
  Target        # TargetMachine, TargetRegistry
  X86CodeGen    # X86 backend (replace with your target)
  X86AsmParser
  X86Desc
  X86Info
)

# ── Targets ───────────────────────────────────────────────────────────────────
add_executable(mycompiler
  src/main.cpp
  src/Frontend.cpp
  src/CodeGen.cpp
)

target_include_directories(mycompiler PRIVATE include)
target_link_libraries(mycompiler PRIVATE ${LLVM_LIBS})

Component reference

List all available components:

llvm-config-22 --components

Commonly used components

Component	What it provides
`Core`	`LLVMContext`, `Module`, `Function`, `IRBuilder`, all IR types
`Support`	`raw_ostream`, `StringRef`, `Error`, `Expected`, `CommandLine`, `MemoryBuffer`
`Analysis`	`DominatorTree`, `LoopInfo`, `ScalarEvolution`, `AAResults`, `CallGraph`
`Passes`	`PassBuilder`, `ModulePassManager`, all standard analyses
`IRReader`	`parseIRFile()`, `parseAssemblyString()`
`BitReader`	`parseBitcodeFile()`
`BitWriter`	`WriteBitcodeToFile()`
`Linker`	`Linker::linkModules()`
`TransformUtils`	`CloneFunction`, `InlineFunction`, utility transforms
`Scalar`	Scalar optimization passes (instcombine, simplifycfg, etc.)
`IPO`	Interprocedural passes (inliner, argument promotion, etc.)
`Vectorize`	Loop and SLP vectorizers
`Target`	`TargetMachine`, `TargetRegistry`, `TargetOptions`
`MC`	`MCContext`, `MCInstrInfo`, `MCRegisterInfo` — needed for MC layer
`ExecutionEngine`	LLVM interpreter / JIT infrastructure
`MCJIT`	MCJIT execution engine
`OrcJIT`	ORC JIT v2 (preferred JIT in LLVM 22)
`X86CodeGen`	X86 target code generation
`AArch64CodeGen`	AArch64 target code generation
`RISCVCodeGen`	RISC-V target code generation

Build and configure

# Using LLVM_DIR explicitly
cmake -S . -B build \
  -DCMAKE_BUILD_TYPE=Release \
  -DLLVM_DIR=$(llvm-config-22 --cmakedir)

# Or via CMAKE_PREFIX_PATH
cmake -S . -B build \
  -DCMAKE_BUILD_TYPE=Release \
  -DCMAKE_PREFIX_PATH=/usr/local/llvm-22

cmake --build build -j$(nproc)

Pass plugin CMake setup

To build a pass loadable by opt --load-pass-plugin:

add_library(MyPassPlugin MODULE
  src/MyPass.cpp
)

target_include_directories(MyPassPlugin PRIVATE
  ${LLVM_INCLUDE_DIRS}
  include
)

target_compile_definitions(MyPassPlugin PRIVATE ${LLVM_DEFINITIONS})

set_target_properties(MyPassPlugin PROPERTIES
  CXX_STANDARD 17
  POSITION_INDEPENDENT_CODE ON
  # No default lib prefix on macOS/Linux
  PREFIX ""
)

# Do NOT link LLVM libs into the plugin — use symbols from the host (opt)
# target_link_libraries(MyPassPlugin PRIVATE ${LLVM_LIBS})  ← DON'T DO THIS

Test the plugin:

opt --load-pass-plugin=./MyPassPlugin.so \
    -passes=my-pass -S input.ll

LLVM_ENABLE_ASSERTIONS and build types

# Debug build with assertions (slow, catches bugs early)
cmake -DCMAKE_BUILD_TYPE=Debug \
      -DLLVM_ENABLE_ASSERTIONS=ON ...

# Release with assertions (recommended for development)
cmake -DCMAKE_BUILD_TYPE=RelWithDebInfo \
      -DLLVM_ENABLE_ASSERTIONS=ON ...

# Release (production / benchmarking)
cmake -DCMAKE_BUILD_TYPE=Release \
      -DLLVM_ENABLE_ASSERTIONS=OFF ...

Match LLVM_ENABLE_ASSERTIONS to what your LLVM install was built with to avoid ABI mismatches.

Multiple LLVM installs

If you have multiple LLVM versions installed, avoid mixing them:

# Ensure cmake finds LLVM 22, not LLVM 21:
export PATH=/usr/local/llvm-22/bin:$PATH
cmake -DLLVM_DIR=/usr/local/llvm-22/lib/cmake/llvm ...

# Check version after configure:
# The cmake output should show: "LLVM version: 22.x.x"

Useful cmake variables set by LLVMConfig.cmake

Variable	Description
`LLVM_PACKAGE_VERSION`	Full version string, e.g. `22.1.2`
`LLVM_VERSION_MAJOR`	Major version integer, e.g. `22`
`LLVM_INCLUDE_DIRS`	Header search paths
`LLVM_LIBRARY_DIRS`	Library search paths
`LLVM_DEFINITIONS`	Compiler definitions (e.g. `-D_GNU_SOURCE`)
`LLVM_TOOLS_BINARY_DIR`	Path to `opt`, `llc`, `llvm-lit`, etc.
`LLVM_BUILD_MAIN_SRC_DIR`	Source tree (only set for build-tree installs)
`LLVM_ENABLE_ASSERTIONS`	Whether assertions were enabled
`LLVM_ENABLE_EH`	Whether exceptions are enabled in LLVM
`LLVM_ENABLE_RTTI`	Whether RTTI is enabled in LLVM

Important: If LLVM_ENABLE_RTTI=OFF (the default), your project must also disable RTTI:
if(NOT LLVM_ENABLE_RTTI)
  target_compile_options(mycompiler PRIVATE -fno-rtti)
endif()

Common mistakes

Do NOT hardcode -lLLVMCore etc. — use llvm_map_components_to_libnames so CMake handles ordering and transitive deps.
Do NOT link LLVM libs into a pass plugin — the plugin is loaded into opt which already has them; double-linking causes symbol conflicts.
Do NOT mix LLVM 22 headers with LLVM 21 libraries — always verify LLVM_PACKAGE_VERSION in the cmake output.
Do NOT forget to match RTTI and exception settings between your project and the LLVM install.
ALWAYS call InitializeAll*() target init functions before using TargetRegistry or creating TargetMachine.