Llvm.NET

Welcome to Llvm.NET!

Llvm.NET provides LLVM language and runtime bindings for .NET based applications. Llvm.NET's goal is to provide as robust Class library that accurately reflects the underlying LLVM C++ model. This is done through an extend LLVM-C API bundled as a native windows DLL (LibLLVM.DLL). Llvm.NET uses the support of LibLLVM to gain access to the LLVM class library and project it into a .NET managed library that reflects the original class library design.
The goal is to match the original class model as closely as possible, while providing an object model to .NET applications that feels familiar and consistent with common styles and patterns in .NET Framework applications. Thus, while class, method and enumeration names are similar to their counterparts in LLVM, they are not always identical.

Documentation for the Llvm.NET class library is located at http://netmf.github.io/Llvm.NET

Why Llvm.NET?

Llvm.NET was developed as a means to leverage LLVM as the back-end for an Ahead-Of-Time (AOT) compilation tool for .NET applications targeting micro controllers (e.g. An AOT compiler for the .NET Micro Framework ). The initial proof of concept built on Llvm.NET was successful in delivering on a basic application that could implement the micro controller equivalent of the classic "Hello World!" application (e.g. Blinky - an app that blinks an LED) using LLVM as the back-end code generator. This led to the revival of a former project doing AOT with its own code generator that was tied to the ARMv4 Instruction set. Thus the Llilum project was born. Llvm.NET has continued to evolve and improve along with Llilum, though it remains a distinct project as it has no dependencies on Llilum or any of its components. Llvm.NET is viable for any .NET applications wishing to leverage the functionality of the LLVM libraries from .NET applications.

Brief History

Llvm.NET began with LLVM 3.4 as a C++/CLI wrapper which enabled a closer binding to the original C++ object model then the official LLVM-C API supported. As Llvm.NET progressed so to did LLVM. Eventually the LLVM code base migrated to requiring C++11 support in the language to build. This became an issue for the C++/CLI wrapper as the Microsoft C++/CLI compiler didn't support the C++11 syntax. Thus a change was made to Llvm.NET to move to an extended C API with a C# adapter layer to provide the full experience .NET developers expect. While the transition was a tedious one very little application code required changes.

Platform Support

Currently LLVM.NET supports Win32 and x64 buids targeting the full desktop framework v4.5. To keep life simpler the nuget package contains both native platform binaries and Llvm.NET itself is built for the "AnyCPU" platform. Llvm.NET contains code to dynamically detect the platform it is running on and load the appropriate DLL. This allows applications to build for AnyCPU without creating multiple build configurations and release vehicles for applications. However, if your application has other needs that require a specific platform target, then LlVM.NET can still function.

Building Llvm.NET

Pre-requsites

• Download LLVM source for 3.9.1 (At this time LLVM is 3.9.1 )
  • You will need a tool to extract files from that archive format. On Windows the recommended tool is 7zip
• Build of LLVM libraries
  To Build the LLVM libraries you can use the Build-LlvmWithVS PowerShell script provided. For more information on using the script open a PowerShell command prompt in the Llvm.NET source directory and run PS> Get-Help .\Build-LlvmWithVs.ps1.

NOTE: On a typical developer machines the LLVM library build takes approximately 1.5 hours so letting it run overnight or when you are otherwise away from your computer is usually a good idea. Fortunately this only needs to be done once for a given release of LLVM.

If you have Visual Studio 2017 RC (or RTM when available) with the Visual C++ Tools for CMake, you can build the LLVM libs in VS. However, the default behavior is to build everything, which can take upwards of 6 hours on most typical machines. Instead of doing a full build you can use the Build-LlvmWithVS PowerShell script with the -CreateSettingsJson to create the CMakeSettings.json file that VS will use to configure VS to reduce what is built to just the libraries needed for Llvm.NET.

Using Visual Studio

The repository contains a Visual Studio solution file that allows building Llvm.NET and LibLLVM for a single platform configuration, as well as running the available unit tests. This is the primary mode of working with the Llvm.NET source code duing development.

Replicating the automated build

The Automated build support for Llvm.NET uses BuildAll.slnproj to build all the binaries, sign them [signing not yet supported], and generate a nuget package. To build the full package simply run msbuild BuildAll.slnproj

Sample Application

The TestDebugInfo sample application provides an example of using Llvm.NET to generate LLVM Bit code equivalent to what the Clang compiler generates for a simple C language file. TestDebugInfo doesn't actually parse the source, instead it is a manually constructed and documented example of how to use Llvm.NET to accomplish the bit-code generation.

Code of Conduct

This project has adopted the code of conduct defined by the Contributor Covenant to clarify expected behavior in our community. For more information, see the .NET Foundation Code of Conduct.