M1

Build LLVM on Apple Silicon(M1)

How bo build

Build cmake

I recommend that you install cmake via cmake.org. You can use cmake with adding the path to PATH.

Build LLVM

At first, check your Terminal.app without using Rosetta.

To avoid using libxml2, edit CMakeLists.txt as follows,

set(LLVM_ENABLE_LIBXML2 "OFF" CACHE STRING "Use libxml2 if available. Can be ON, OFF, or FORCE_ON")

Without this modification, linker can not build llvm because it can not find and link libxml. I do not use libxml in my codes. If you want to use libxml in LLVM, I can not help you.

Next, prepare and build any files using cmake. My MacBookPro M1 crashed when I ran the make -j command because the build process used up all the memory.　It is recommended that you specify the number of processes with the j option.

mkdir build
cd build
cmake .. $LLVM_SRC_DIR -DCMAKE_BUILD_TYPE=Release -DLLVM_TARGETS_TO_BUILD="ARM;X86;AArch64"
make -j 4

Build sources

I do not copy any llvm files into /usr/, because I want to use multiple versions of LLVM switching between them.

For example, we can build source codes using LLVM as follows,

 /usr/bin/clang++ add.cpp -o add `<path to llvm>/build/bin/llvm-config --cxxflags --ldflags --libs --libfiles core orcjit mcjit native --system-libs`

Compile speed

I compared the compile speed between Apple Silicon M1 and Intel Core i9, using add.cpp.

• Apple Silicon(M1) 1.93[sec]
• Intel(Core i9) 4.6[sec]

As a result, M1 was 2.4 times faster than Core i9.

Visual Studio Code

Visual studio terminal runs on i386 at default. Therefore, I enforcely compile the files for ARM using the following settings.

{
    "tasks": [
        {
            "type": "shell",
            "label": "clang++ build active file",
            "command": "arch",
            "args": [
                "-arm64",
                "/usr/bin/clang++",
                "-g",
                "-O0",
                "${fileDirname}/${fileBasename}",
                "-o",
                "${fileDirname}/${fileBasenameNoExtension}",
                "`/Users/sonson/Downloads/llvm-11.0.0.src/build/bin/llvm-config", "--cppflags`",
                "-std=c++17",
                "`/Users/sonson/Downloads/llvm-11.0.0.src/build/bin/llvm-config", "--ldflags", "--libs", "--libfiles", "core","orcjit","mcjit", "native", "--system-libs`"
            ]
        }
    ],
    "version": "2.0.0"
}

Debugging in Visual studio code.

• Use CodeLLDB and following launch.json.

{
    // Use IntelliSense to learn about possible attributes.
    // Hover to view descriptions of existing attributes.
    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [
        {
            "name": "clang++",
            "type": "lldb",
            "request": "launch",
            // "targetArchitecture": "arm64",
            "program": "${fileDirname}/${fileBasenameNoExtension}",
            "args": [],
            // "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            // "environment": [],
            // "externalConsole": false,
            // "MIMode": "lldb",
            "preLaunchTask": "clang++ build active file"
        }
    ]
}