Using LLVM/Clang for Compilation
This chapter describes the basic knowledge of LLVM/Clang compilation and provides examples for demonstration. For more information about how to use Clang, run the clang --help command.
Overview
LLVM is a compiler that covers multiple programming languages and target processors. It uses Clang as the compiler and driver of C and C++. Clang can not only compile C and C++ programs into the LLVM intermediate representations (IRs), but also invoke all LLVM optimization passes for code generation until the final binary file is generated.
LLVM/Clang Installation
Install the Clang and LLVM software packages using the Yum source in the openEuler OS. llvm12 is installed by default.
yum install llvm
yum install clang
yum install lld // The openEuler Yum source does not contain LLD12.
Check whether the installation is successful.
clang -v
If the command output contains the Clang version information, the installation is successful.
Coexistence of Multiple Versions
Configure the openEuler LLVM/Clang multi-version support as follows:
Yum package name:
llvm<ver>{-*}
clang<ver>{-*}
lld<ver>{-*}
bolt<ver>{-*}
Example:
clang15
llvm15-devel
Installation path:
/usr/lib64/llvm<ver>
Example:
/usr/lib64/llvm15
Executable files with the -<ver> suffix are installed in the /usr/bin directory.
Example:
/usr/bin/clang-15
/usr/bin/lld-15
Currently, the following LLVM/Clang versions are supported:
llvm //By default, llvm12 is installed.
llvm-15
Install other versions using Yum.
yum install llvm15
yum install clang15
yum install lld15
Check whether the installation is successful.
clang-15 -v
Example
Compile and run C and C++ programs.
clang [command line flags] hello.c -o hello.o
./hello.o
clang++ [command line flags] hello.cpp -o hello.o
./hello.o
Specify the LLD of LLVM as the linker. If it is not specified, the default LLD is used.
clang [command line flags] -fuse-ld=lld hello.c -o hello.o
./hello.o
For more information, see the LLVM User Guides.
