LLVM-22.1.0

#### Beyond Linux® From Scratch (systemd Edition) - Version r13.0-553

### Chapter 13. Programming

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# LLVM-22.1.0

## Introduction to LLVM

The LLVM package contains a collection of modular and reusable compiler and toolchain technologies. The Low Level Virtual Machine (LLVM) Core libraries provide a modern source and target-independent optimizer, along with code generation support for many popular CPUs (as well as some less common ones!). These libraries are built around a well specified code representation known as the LLVM intermediate representation ("LLVM IR").

Clang provides new C, C++, Objective C and Objective C++ front-ends for LLVM and is required by some desktop packages such as firefox and for rust if that is built using the system LLVM.

The Compiler RT package provides runtime sanitizer and profiling libraries for developers who use Clang and LLVM.

### Note

Development versions of BLFS may not build or run some packages properly if LFS or dependencies have been updated since the most recent stable versions of the books.

### Package Information

- Download (HTTP): https://github.com/llvm/llvm-project/releases/download/llvmorg-22.1.0/llvm-project-22.1.0.src.tar.xz

- Download MD5 sum: eebd30f81349347d789f04b5ddd41112

- Download size: 160 MB

- Estimated disk space required: 4.7 GB (1.1 GB installed; add 23 GB for tests and 2.3 GB for documentation)

- Estimated build time: 13 SBU (Add 19 SBU for tests; both using parallelism=8)

### LLVM Dependencies

#### Required

CMake-4.3.2

#### Optional

Doxygen-1.17.0, git-2.54.0, Graphviz-14.1.5, libunwind-1.8.3, libxml2-2.15.3, psutil-7.2.2 (for tests), Pygments-2.20.0, PyYAML-6.0.3 (for tests), rsync-3.4.2 (for tests), sphinx-9.1.0, Systemd-260.1 (rebuilt with PAM, for tests), texlive-20250308 (or install-tl-unx), Valgrind-3.27.0, Zip-3.0, myst-parser (for building documentation), OCaml, and Z3

## Installation of LLVM

There are many Python scripts in this package which use /usr/bin/env python to access the system Python which on LFS is Python-3.14.4. Use the following command to fix these scripts:

    grep -rl '#!.*python$' | xargs sed -i '1s/python$/python3/'

Ensure installing the FileCheck program which is needed by the test suite of some packages (for example rustc-1.95.0):

    sed 's/utility/tool/' -i llvm/utils/FileCheck/CMakeLists.txt

Install LLVM by running the following commands:

    mkdir -v llvm/build &&
    cd       llvm/build &&

    CC=gcc CXX=g++                               \
    cmake -D CMAKE_INSTALL_PREFIX=/usr           \
          -D CMAKE_SKIP_INSTALL_RPATH=ON         \
          -D LLVM_ENABLE_FFI=ON                  \
          -D CMAKE_BUILD_TYPE=Release            \
          -D LLVM_BUILD_LLVM_DYLIB=ON            \
          -D LLVM_LINK_LLVM_DYLIB=ON             \
          -D LLVM_ENABLE_RTTI=ON                 \
          -D LLVM_TARGETS_TO_BUILD="host;AMDGPU" \
          -D LLVM_ENABLE_PROJECTS=clang          \
          -D LLVM_ENABLE_RUNTIMES=compiler-rt    \
          -D LLVM_BINUTILS_INCDIR=/usr/include   \
          -D LLVM_INCLUDE_BENCHMARKS=OFF         \
          -D CLANG_DEFAULT_PIE_ON_LINUX=ON       \
          -D CLANG_CONFIG_FILE_SYSTEM_DIR=/etc/clang \
          -W no-dev -G Ninja ..                  &&
    ninja

LLVM test suite can produce many core dump files. They will occupy a large amount of disk space, and the core dump process can significantly slow down the testing. To test the results with core dump disabled, ensure Systemd-260.1 and Shadow-4.19.4 have been rebuilt with Linux-PAM-1.7.2 support (if you are interacting via a SSH or graphical session, also ensure the OpenSSH-10.3p1 server or the desktop manager has been built with Linux-PAM-1.7.2) and the current login session is started after updating the `/etc/pam.d/system-session` file to include `pam_systemd.so`, then issue:

    systemctl   --user start dbus &&
    systemd-run --user --pty -d -G -p LimitCORE=0 ninja check-all

If `-jN` (N replaced with a number) is passed to ninja, the tests will be built with N logical cores, but run using all available logical cores. Run the test command in a cgroup (pass the `-p AllowedCPUs=...` option to the systemd-run command, read the section called “Use Linux Control Group to Limit the Resource Usage” for details) to limit the number of logical cores for running the tests. Four tests named `Linux/pthread_join.cpp` are known to fail. One test named `Linux/clone_setns.cpp` will fail if `CONFIG_USER_NS` is not enabled in kernel configuration.

Now, as the `root` user:

    ninja install

## Command Explanations

`-D CMAKE_SKIP_INSTALL_RPATH=ON`: This switch makes cmake remove hardcoded library search paths (rpath) when installing a binary executable file or a shared library. This package does not need rpath once it's installed into the standard location, and rpath may sometimes cause unwanted effects or even security issues.

`-D LLVM_ENABLE_FFI=ON`: This switch allows LLVM to use libffi.

`-D LLVM_BUILD_LLVM_DYLIB=ON`: This switch builds the libraries as static and links all of them into an unique shared one. This is the recommended way of building a shared library.

`-D CMAKE_BUILD_TYPE=Release`: This switch enables compiler optimizations in order to speed up the code and reduce its size. It also disables some compile checks which are not necessary on a production system.

`-D LLVM_TARGETS_TO_BUILD="host;AMDGPU"`: This switch enables building for the same target as the host, and also for the r600 AMD GPU used by the Mesa r600 and radeonsi drivers. The default is all of the targets. You can use a semicolon separated list. Valid targets are: host, AArch64, AMDGPU, ARM, AVR, BPF, Hexagon, Lanai, LoongArch, Mips, MSP430, NVPTX, PowerPC, RISCV, Sparc, SystemZ, VE, WebAssembly, X86, XCore, or all.

`-D LLVM_ENABLE_PROJECTS=clang`: This switch selects the LLVM subprojects to be built (in addition to the LLVM libraries). Read the `LLVM_ALL_PROJECTS` definition in `llvm/CMakeLists.txt` for the list of all the subprojects. For BLFS we only build clang (that the developers of some BLFS packages recommend to use instead of GCC).

`-D LLVM_ENABLE_RUNTIMES=compiler-rt`: This switch selects the LLVM runtime libraries to be built. For BLFS we only need compiler-rt (for some features of clang and rustc-1.95.0) and libclc, and the latter have to be built separately (libclc-22.1.0) to avoid a circular dependency involving SPIRV-LLVM-Translator-22.1.2. So we only enable compiler-rt here.

`-D LLVM_LINK_LLVM_DYLIB=ON`: Used in conjunction with `-D LLVM_BUILD_LLVM_DYLIB=ON`, this switch enables linking the tools against the shared library instead of the static ones. It slightly reduces their size and also ensures that llvm-config will correctly use libLLVM-22.so.

`-D LLVM_ENABLE_RTTI=ON`: This switch is used to build LLVM with run-time type information. This is required for building Mesa-26.0.1.

`-D LLVM_BINUTILS_INCDIR=/usr/include`: This switch is used to tell the build system the location of binutils headers, which were installed in LFS. This allows the building of `LLVMgold.so`, which is needed for building programs with clang and Link Time Optimization (LTO).

`-D LLVM_INCLUDE_BENCHMARKS=OFF`: is used to disable generation build targets for the LLVM benchmarks. This option requires additional code that is not currently available.

`-D CLANG_DEFAULT_PIE_ON_LINUX=ON`: makes `-fpie` option the default when compiling programs. Together with the ASLR feature enabled in the kernel, this defeats some kind of attacks based on known memory layouts.

`-D CLANG_CONFIG_FILE_SYSTEM_DIR=/etc/clang`: makes clang and clang++ search `/etc/clang` for configuration files.

`-D BUILD_SHARED_LIBS=ON`: if used instead of `-D LLVM_BUILD_LLVM_DYLIB=ON` and `-D LLVM_LINK_LLVM_DYLIB=ON`, builds all the LLVM libraries (about 60) as shared libraries instead of static.

`-D LLVM_ENABLE_DOXYGEN=ON -D LLVM_ENABLE_DOCS=ON`: Enables the generation of browsable HTML documentation if you have installed Doxygen-1.17.0. The documentation will be built at the end of the build process.

## Configuring LLVM

### Configuration Information

If you've built Clang, as the `root` user create two configuration files to make SSP enabled by default for clang and clang++, so the default configuration of their SSP feature will be consistent with GCC-15.2.0:

    mkdir -pv /etc/clang &&
    for i in clang clang++; do
      echo -fstack-protector-strong > /etc/clang/$i.cfg
    done

## Contents

Installed Programs: amdgpu-arch, analyze-build, bugpoint, c-index-test, clang, clang++ (symlinks to clang-22), clang-22, clang-check, clang-cl, clang-cpp (last two symlinks to clang), clang-extdef-mapping, clang-format, clang-installapi, clang-linker-wrapper, clang-nvlink-wrapper, clang-offload-bundler, clang-offload-packager, clang-refactor, clang-repl, clang-scan-deps, clang-sycl-linker, clang-tblgen, diagtool, dsymutil, FileCheck, git-clang-format, hmaptool, intercept-build, llc, lli, llvm-addr2line (symlink to llvm-symbolizer), llvm-ar, llvm-as, llvm-bcanalyzer, llvm-bitcode-strip (symlink to llvm-objcopy), llvm-cat, llvm-cfi-verify, llvm-cgdata, llvm-config, llvm-cov, llvm-c-test, llvm-ctxprog-util, llvm-cvtres, llvm-cxxdump, llvm-cxxfilt, llvm-cxxmap, llvm-debuginfo-analyzer, llvm-debuginfod, llvm-debuginfod-find, llvm-diff, llvm-dis, llvm-dlltool (symlink to llvm-ar), llvm-dwarfdump, llvm-dwarfutil, llvm-dwp, llvm-exegesis, llvm-extract, llvm-gsymutil, llvm-ifs, llvm-install-name-tool (symlink to llvm-objcopy), llvm-jitlink, llvm-lib (symlink to llvm-ar), llvm-libtool-darwin, llvm-link, llvm-lipo, llvm-lto, llvm-lto2, llvm-mc, llvm-mca, llvm-ml, llvm-modextract, llvm-mt, llvm-nm, llvm-objcopy, llvm-objdump, llvm-opt-report, llvm-otool (symlink to llv-objdump), llvm-pdbutil, llvm-profdata, llvm-profgen, llvm-ranlib (symlink to llvm-ar), llvm-rc, llvm-readelf (symlink to llvm-readobj), llvm-readobj, llvm-readtapi, llvm-reduce, llvm-remarkutil, llvm-rtdyld, llvm-sim, llvm-size, llvm-split, llvm-stress, llvm-strings, llvm-strip (symlink to llvm-objcopy), llvm-symbolizer, llvm-tblgen, llvm-tli-checker, llvm-undname, llvm-windres (symlink to llvm-rc), llvm-xray, nvptx-arch, opt, sancov, sanstats, scan-build, scan-build-py, scan-view, and verify-uselistorder
Installed Libraries: libLLVM.so, libLLVM*.a (107 libraries), libLTO.so, libRemarks.so, libclang.so, libclang-cpp.so, libclang*.a (43 libraries), and LLVMgold.so
Installed Directories: /usr/include/{clang,clang-c,llvm,llvm-c}, /usr/lib/{clang,cmake/{clang,llvm},libear,libscanbuild}, /usr/share/{clang,opt-viewer,scan-build,scan-view}, and /etc/clang

### Short Descriptions

amdgpu-arch | lists AMD GPUs installed; at runtime it needs `libhsa-runtime64.so` which is not a part of BLFS
analyze-build | is a static analysis tool
bugpoint | is the automatic test case reduction tool
c-index-test | is used to test the libclang API and demonstrate its usage
clang | is the Clang C, C++, and Objective-C compiler
clang-check | is a tool to perform static code analysis and display Abstract Syntax Trees (AST)
clang-extdef-mapping | is a tool to collect the USR name and location of external definitions in a source file
clang-format | is a tool to format C/C++/Java/JavaScript/Objective-C/Protobuf code
clang-linker-wrapper | is a wrapper utility over the host linker
clang-offload-bundler | is a tool to bundle/unbundle OpenMP offloaded files associated with a common source file
clang-offload-packager | is a tool to bundle several object files into a single binary, which can then be used to create a fatbinary containing offloading code
clang-refactor | is a Clang-based refactoring tool for C, C++ and Objective-C
clang-scan-deps | is a tool to scan for dependencies in a source file
clang-tblgen | is a program that translates compiler-related target description (`.td`) files into C++ code and other output formats
diagtool | is a combination of tools for dealing with diagnostics in clang
FileCheck | is a tool that reads two files (one from standard input, and one specified on the command line) and uses one to verify the other.
dsymutil | is a tool used to manipulate archived DWARF debug symbol files, compatible with the Darwin command dsymutil
git-clang-format | runs clang-format on git generated patches (requires git-2.54.0)
hmaptool | is a Python tool to dump and construct header maps
intercept-build | generates a database of build commands for a project
llc | is the LLVM static compiler
lli | is used to directly execute programs from LLVM bitcode
llvm-addr2line | is a tool used to convert addresses into file names and line numbers
llvm-ar | is the LLVM archiver
llvm-as | is the LLVM assembler
llvm-bcanalyzer | is the LLVM bitcode analyzer
llvm-bitcode-strip | strips LLVM bitcode from an object
llvm-cat | is a tool to concatenate llvm modules
llvm-cfi-verify | identifies whether Control Flow Integrity protects all indirect control flow instructions in the provided object file, DSO, or binary
llvm-config | Prints LLVM compilation options
llvm-cov | is used to emit coverage information
llvm-c-test | is a bytecode disassembler
llvm-cvtres | is a tool to convert Microsoft resource files to COFF
llvm-cxxdump | is used as a C++ ABI Data Dumper
llvm-cxxfilt | is used to demangle C++ symbols in llvm code
llvm-cxxmap | is used to remap C++ mangled symbols
llvm-debuginfo-analyzer | prints a logical representation of low-level debug information
llvm-debuginfod | is a service providing debug information over an HTTP API for analyzing stripped binaries
llvm-debuginfod-find | is an interface to the llvm-debuginfod daemon for finding debuginfod artifacts
llvm-diff | is the LLVM structural 'diff'
llvm-dis | is the LLVM disassembler
llvm-dwarfdump | prints the content of DWARF sections in object files
llvm-dwarfutil | is a tool to copy and manipulate debug info
llvm-dwp | merges split DWARF files
llvm-elfabi | is used to read information about an ELF binary's ABI
llvm-exegesis | is a benchmarking tool that uses information available in LLVM to measure host machine instruction characteristics like latency or port decomposition
llvm-extract | is used to extract a function from an LLVM module
llvm-gsymutil | is used to process GSYM Symbolication Format files which convert memory addresses to function name and source file line. These files are smaller than DWARF or Breakpad files
llvm-ifs | is used to merge interface stubs with object files
llvm-install-name-tool | is used to rewrite load commands into MachO binary format
llvm-jitlink | is used to parse relocatable object files to make their contents executable in a target process
llvm-libtool-darwin | provides basic libtool functionality on Darwin-based systems. This is mostly useful if you are generating binaries for macOS systems
llvm-link | is the LLVM linker
llvm-lipo | is used to create universal binaries from MachO files
llvm-lto | is the LLVM LTO (link time optimization) linker
llvm-lto2 | is a test harness for the resolution based LTO interface
llvm-mc | is a standalone machine code assembler/disassembler
llvm-mca | is a performance analysis tool to statically measure the performance of machine code
llvm-ml | is a playground for machine code provided by LLVM
llvm-modextract | is a tool to extract one module from multimodule bitcode files
llvm-mt | is a tool to generate signed files and catalogs from a side-by-side assembly manifest (used for Microsoft SDK)
llvm-nm | is used to list LLVM bitcode and object file's symbol table
llvm-objcopy | is LLVM's version of an objcopy tool
llvm-objdump | is an LLVM object file dumper
llvm-opt-report | is a tool to generate an optimization report from YAML optimization record files
llvm-pdbutil | is a PDB (Program Database) dumper. PDB is a Microsoft format
llvm-profdata | is a small tool to manipulate and print profile data files
llvm-profgen | generates LLVM SPGO profiling information
llvm-ranlib | is used to generate an index for a LLVM archive
llvm-rc | is a platform-independent tool to compile resource scripts into binary resource files
llvm-readobj | displays low-level format-specific information about object files
llvm-readtapi | is the LLVM TAPI file reader and transformer
llvm-reduce | is used to automatically reduce testcases when running a test suite
llvm-remarkutil | converts remark files between bitstream and YAML; or prints function instruction count information in remark files
llvm-rtdyld | is the LLVM MC-JIT tool
llvm-size | is the LLVM object size dumper
llvm-split | is the LLVM module splitter
llvm-stress | is used to generate random `.ll` files
llvm-strings | print strings found in a binary (object file, executable, or archive library)
llvm-symbolizer | converts addresses into source code locations
llvm-tblgen | is the LLVM Target Description To C++ Code Generator
llvm-tli-checker | is the LLVM TargetLibraryInfo versus SDK checker
llvm-undname | is a tool to demangle names
llvm-xray | is an implementation of Google's XRay function call tracing system
nvptx-arch | lists NVIDIA GPUs installed; at runtime it needs `libcuda.so` which is not a part of BLFS
opt | is the LLVM optimizer
sancov | is the sanitizer coverage processing tool
sanstats | is the sanitizer statistics processing tool
scan-build | is a Perl script that invokes the Clang static analyzer
scan-build-py | is a Python script that invokes the Clang static analyzer
scan-view | is a viewer for Clang static analyzer results
verify-uselistorder | is the LLVM tool to verify use-list order

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