From 8a093a00ec402988b1784fcff1b2fc3b48c38298 Mon Sep 17 00:00:00 2001
From: Jakub Sujak <jakub.sujak@arm.com>
Date: Mon, 8 Jul 2024 13:18:01 +0100
Subject: [PATCH] Add CMake build instructions

* Add instructions for building for various platforms using CMake.

* Provide a CMake toolchain file for Arm GNU Toolchain.

Signed-off-by: Jakub Sujak <jakub.sujak@arm.com>
---
 README.md                                     | 41 +++++++++++++++++++
 .../aarch64-none-linux-gnu.toolchain.cmake    | 15 +++++++
 2 files changed, 56 insertions(+)
 create mode 100644 cmake/toolchains/aarch64-none-linux-gnu.toolchain.cmake

diff --git a/README.md b/README.md
index f480734b..b4730790 100644
--- a/README.md
+++ b/README.md
@@ -164,6 +164,47 @@ Some of the data types currently supported with the KleidiAI library are the fol
 </tr>
 </table>
 
+<h1> How to build </h1>
+
+<h2> Prerequisites </h2>
+
+KleidiAI requires the following dependencies, obtainable via your preferred package manager, to be installed and available on your system to be able to build the project.
+
+- `build-essential`
+- `cmake >= 3.18`
+
+In addition, you may choose to use the following toolchains:
+
+- (Optional) `Arm GNU toolchain` available to download from the [Arm Developer](https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads) website.
+- (Optional) `Android NDK` available to download from the [Android Developer](https://developer.android.com/ndk/downloads/index.html) website.
+
+<h2> Compile natively on an Arm®-based system </h2>
+
+You can quickly compile KleidiAI on your system with an Arm® processor by using the following commands:
+
+```shell
+cmake -DCMAKE_BUILD_TYPE=Release -S . -B build/
+cmake --build ./build
+```
+
+<h2> Cross-compile to Android™ </h2>
+
+Cross-compiling for Android systems requires the Android NDK toolset. The downloaded NDK contains the CMake toolchain file necessary for cross-compiling the project and must be provided to CMake with the `-DCMAKE_TOOLCHAIN_FILE` option.
+
+```shell
+cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_TOOLCHAIN_FILE=$NDK/build/cmake/android.toolchain.cmake -DANDROID_ABI=arm64-v8a -S . -B build/
+cmake --build ./build
+```
+
+<h2> Cross-compile to Linux® </h2>
+
+The Arm GNU toolchain can be used to cross-compile to a Linux system with an Arm® processor like a Raspberry Pi from an x86_64 Linux host machine. Ensure the toolchain is available on your PATH and provide to CMake the Arm GNU Toolchain CMakefile found in `cmake/toolchains` directory with the `-DCMAKE_TOOLCHAIN_FILE` option.
+
+```shell
+cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_TOOLCHAIN_FILE=cmake/toolchains/aarch64-none-linux-gnu.toolchain.cmake -S . -B build/
+cmake --build ./build
+```
+
 <h1> Release Cadence </h1>
 The release is a tagged version of the source code.
 After the first official release (v0.1.0), releases will be made at least once every 3 months. The goal is a predictable and shorter time span between the releases. Until that point is
diff --git a/cmake/toolchains/aarch64-none-linux-gnu.toolchain.cmake b/cmake/toolchains/aarch64-none-linux-gnu.toolchain.cmake
new file mode 100644
index 00000000..83843084
--- /dev/null
+++ b/cmake/toolchains/aarch64-none-linux-gnu.toolchain.cmake
@@ -0,0 +1,15 @@
+#
+# SPDX-FileCopyrightText: Copyright 2024 Arm Limited and/or its affiliates <open-source-office@arm.com>
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+# The Arm GNU Toolchain is available for download from Arm Developer.
+# https://developer.arm.com/downloads/-/arm-gnu-toolchain-downloads
+
+set(CMAKE_SYSTEM_NAME      Linux)
+set(CMAKE_SYSTEM_PROCESSOR aarch64)
+set(CMAKE_CROSSCOMPILING   TRUE)
+
+set(CMAKE_C_COMPILER   aarch64-none-linux-gnu-gcc)
+set(CMAKE_CXX_COMPILER aarch64-none-linux-gnu-g++)
-- 
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