Set up the SME2 environment

Choose an SME2 execution environment

You can run the examples using one of the following routes:

• Build and run natively on an arm64 macOS device with an M4 processor or later.
• Cross-compile on macOS or Linux and run on an Android phone with SME2 support.

Before selecting a target device, see the list of devices with native SME2 support .

The examples use recent Arm C Language Extensions (ACLE) intrinsics and Scalable Matrix Extension 2 (SME2) assembly syntax. Use Homebrew LLVM Clang 22 or later for native macOS builds. Android cross-compilation requires host LLVM Clang 22 and Android NDK r29.

Set up native macOS development

Confirm that the system uses the arm64 architecture:

    

        
        
uname -m

    

The expected output is:

    

        
        arm64

        
    

Check that SME2 is available to applications and inspect the maximum streaming vector length (SVL):

    

        
        
sysctl -n hw.optional.arm.FEAT_SME2
sysctl -n hw.optional.arm.sme_max_svl_b

    

The output is similar to:

    

        
        1
64

        
    

The first command must print 1. The second command reports the maximum SVL in bytes. For example, 64 bytes corresponds to an SVL of 512 bits.

If needed, install Homebrew LLVM:

    

        
        
brew install llvm

    

Confirm the version:

    

        
        
/opt/homebrew/opt/llvm/bin/clang --version

    

The output is similar to:

    

        
        Homebrew clang version 22.1.7
Target: arm64-apple-darwin27.0.0

        
    

The Makefile uses Homebrew LLVM at /opt/homebrew/opt/llvm.

Set up Android cross-compilation

The build host doesn’t need SME2 support. The Android device that runs the lookup-table instruction (LUTI) examples does. Install the compiler tools on your macOS or Linux host.

Install LLVM 22 on the build host. On macOS, use Homebrew LLVM. The following Linux commands target Ubuntu 24.04 LTS on either x86-64 or AArch64 and use the LLVM APT packages :

    

        
        

brew install llvm
"$(brew --prefix llvm)/bin/clang" --version
  

    

    

        
        

sudo apt update
sudo apt install ca-certificates wget lsb-release software-properties-common gnupg
wget -O llvm.sh https://apt.llvm.org/llvm.sh
sudo bash llvm.sh 22
sudo apt install llvm-22
clang-22 --version
  

    

Check that Clang reports version 22 or later.

Install Android Native Development Kit (Android NDK) r29:

    

        
        

brew install wget
mkdir -p "$HOME/Library/Android"
cd "$HOME/Library/Android"
wget https://dl.google.com/android/repository/android-ndk-r29-darwin.zip
unzip android-ndk-r29-darwin.zip
  

    

    

        
        

sudo apt update
sudo apt install build-essential wget unzip
cd "$HOME"
wget https://dl.google.com/android/repository/android-ndk-r29-linux.zip
unzip android-ndk-r29-linux.zip
  

    

Set NDK_PATH and ANDROID_NDK_HOME so that the Makefile can locate the NDK:

    

        
        

export NDK_PATH="$HOME/Library/Android/android-ndk-r29"
export ANDROID_NDK_HOME="$NDK_PATH"
  

    

    

        
        

export NDK_PATH="$HOME/android-ndk-r29"
export ANDROID_NDK_HOME="$NDK_PATH"
  

    

Install Android Debug Bridge (adb) if it isn’t already available:

    

        
        

brew install android-platform-tools
  

    

    

        
        

sudo apt install adb
  

    

Enable developer options and USB debugging on the Android phone, connect it to the host, and accept the debugging prompt on the phone.

Verify the connection:

    

        
        
adb devices -l

    

Confirm that the device uses the arm64-v8a application binary interface (ABI):

    

        
        
adb shell getprop ro.product.cpu.abi

    

The expected output is:

    

        
        arm64-v8a

        
    

You can also inspect the CPU feature list:

    

        
        
adb shell "grep -m1 '^Features' /proc/cpuinfo"

    

If SME2 isn’t available to the device, the examples will skip at runtime and exit successfully.

Download and explore the code examples

Download the source and build files into a new code directory. Run the following commands from a working directory of your choice:

    

        
        
BASE_URL=https://raw.githubusercontent.com/ArmDeveloperEcosystem/arm-learning-paths/main/content/learning-paths/mobile-graphics-and-gaming/luti

mkdir code
cd code
for FILE in \
  Makefile \
  example_1_luti_decoding.c \
  example_1_luti_decoding_runner.c \
  example_2_luti_programming.c \
  example_2_luti_programming_test.c; do
  wget "$BASE_URL/code/$FILE" -O "$FILE" || exit 1
done

    

After the download completes, the code directory contains the following source and build files:

    

        
        code/
├── Makefile
├── example_1_luti_decoding.c
├── example_1_luti_decoding_runner.c
├── example_2_luti_programming.c
└── example_2_luti_programming_test.c

        
    

What you’ve accomplished and what’s next

You’ve prepared a compatible Clang compiler, verified an SME2-capable target, and downloaded the source files for the standalone examples.

Next, you’ll use example_1_luti_decoding.c to compare plain C shifts, masks, and scalar lookups with SME2 LUTI2 expansion and matrix accumulation.