Arm Toolchain for Embedded (ATfE) - Zephyr

.. _toolchain_atfe:

Arm Toolchain for Embedded (ATfE) #################################

Arm Toolchain for Embedded (ATfE) is a C and C++ toolchain from Arm based on the free and open-source LLVM Compiler Infrastructure and the Picolib C library for baremetal targets.

ATfE is fined-tuned with a particular focus on performance for newer ARM products (post 2024) like 64-bit Arm Architectures (AArch64), or the M-Profile Vector Extension (MVE, a 32-bit Armv8.1-M extension).

Installation

#. Download and install a Arm toolchain for embedded_ build for your operating system and extract it on your file system.

#. :ref:Set these environment variables <env_vars>:

Set :envvar:ZEPHYR_TOOLCHAIN_VARIANT to host/llvm.
Set :envvar:LLVM_TOOLCHAIN_PATH to the toolchain installation directory.

#. To check that you have set these variables correctly in your current environment, follow these example shell sessions (the :envvar:LLVM_TOOLCHAIN_PATH values may be different on your system):

.. tabs::

  .. group-tab:: Ubuntu

     .. code-block:: bash

        echo $ZEPHYR_TOOLCHAIN_VARIANT
        host/llvm
        echo $LLVM_TOOLCHAIN_PATH
        /home/you/Downloads/ATfE

  .. group-tab:: macOS

     .. code-block:: bash

        echo $ZEPHYR_TOOLCHAIN_VARIANT
        host/llvm
        echo $LLVM_TOOLCHAIN_PATH
        /home/you/Downloads/ATfE

  .. group-tab:: Windows

     .. code-block:: powershell

        > echo %ZEPHYR_TOOLCHAIN_VARIANT%
        host/llvm
        > echo %LLVM_TOOLCHAIN_PATH%
        C:\ATfE

.. _toolchain_env_var:

#. You can also set ZEPHYR_TOOLCHAIN_VARIANT and LLVM_TOOLCHAIN_PATH as CMake variables when generating a build system for a Zephyr application, like so:

.. code-block:: console

  west build ... -- -DZEPHYR_TOOLCHAIN_VARIANT=host/llvm -DLLVM_TOOLCHAIN_PATH=...

Toolchain settings

Because LLVM is widely compatible with GNU tools, When builiding with any LLVM toolchain, you have to specify some settings to let the compiler know what tools to use:

Linker

Set :envvar:CONFIG_LLVM_USE_LLD=y to use LLVM linker.
Set :envvar:CONFIG_LLVM_USE_LD=y to use the GNU LD linker.

Runtime library

Set :envvar:CONFIG_COMPILER_RT_RTLIB=y to use LLVM runtime library.
Set :envvar:CONFIG_LIBGCC_RTLIB=y to use LibGCC runtime library.

.. code-block:: console

west build ... -- -DZEPHYR_TOOLCHAIN_VARIANT=host/llvm -DLLVM_TOOLCHAIN_PATH=... -DCONFIG_LLVM_USE_LLD=y -DCONFIG_COMPILER_RT_RTLIB=y

.. _Arm Toolchain for Embedded: https://developer.arm.com/Tools%20and%20Software/Arm%20Toolchain%20for%20Embedded