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Sulong Logo

Sulong is a high-performance LLVM bitcode interpreter built on the GraalVM by Oracle Labs.

Sulong is written in Java and uses the Truffle language implementation framework and Graal as a dynamic compiler.

With Sulong you can execute C/C++, Fortran, and other programming languages that can be transformed to LLVM bitcode on Graal VM. To execute a program, you have to compile the program to LLVM bitcode by a LLVM front end such as clang.

Graal VM

Sulong is part of the Graal VM. Graal VM supports Linux or Mac OS X on x86 64-bit systems.

  1. Download the Graal VM binaries.
  2. Extract the archive to your file system.
  3. Add the Graal VM /bin folder to your PATH environment variable.

To run programs in LLVM bitcode format on Graal VM, use:

lli [LLI Options] [Graal VM Options] [Polyglot Options] file.bc [program args]

Where file.bc is a single program source file in LLVM bitcode format. Graal VM executes the LLVM bitcode using Sulong as an interpreter. Note: LLVM bitcode is platform dependent. The program must be compiled to bitcode for the appropriate platform.

LLI Options

  • -L <path> sets a path where lli searches for libraries. You can specify -L multiple times.

  • --lib <libraries> adds external library sources (e.g. --lib /path/to/libexample.so or --lib /path/to/example.bc). These library sources are precompiled native libraries or bitcode files. You can specify --lib multiple times. Note: You must specify the library example with --lib /path/to/libexample.so as opposed to common linker -l options.

Graal VM Options

  • --jvm executes the application in JVM mode instead of executing the Graal VM native image.

  • --jvm.<option> passes JVM options to Graal VM. List available JVM options with --jvm.help.

  • --graal.<property>=<value> passes settings to the Graal compiler. For example, --graal.DumpOnError=true sends the compiler intermediate representation (IR) to dump handlers if errors occur.

Polyglot Options

  • --polyglot enables you to interoperate with other programming languages.

  • --<languageID>.<property>=<value> passes properties to guest languages through the Graal Polyglot SDK.

Compiling to LLVM bitcode format

Graal VM can execute C/C++, Fortran, and other programs that can be compiled to LLVM bitcode. As a first step, you have to compile the program to LLVM bitcode using an LLVM frontend such as clang. C/C++ code can be compiled to LLVM bitcode using clang with the -emit-llvm option.

Let's compile test.c

#include <stdio.h>

int main() {
  printf("Hello from Sulong!");
  return 0;

to an LLVM bitcode file test.bc.

clang -O1 -c -emit-llvm -o test.bc test.c

You can then run test.bc on Graal VM as follows:

lli test.bc

Note the -O1 flag in the compile command. Compiling without optimizations is not recommended with Sulong. In particular, cross-language interoperability with Java or another Truffle language will not work when the bitcode is compiled without optimizations.

Compiling C++

You need to add -stdlib=libc++ when compiling C++ code in order to use the right standard library.

clang++ -O1 -c -emit-llvm -stdlib=libc++ -o test.bc test.cpp

Build Dependencies

Sulong is mostly implemented in Java. However, parts of Sulong are implemented in C/C++ and will be compiled to a shared library or a bitcode file. For a successful build you need to have LLVM (incl. CLANG and OPT tool) v3.8 - v6.0 installed.

MacOS: Apple's default LLVM does not contain the opt tool, which a Sulong build needs. We recommend installing LLVM via homebrew and appending the bin path to the PATH. For best experience we suggest to install LLVM 4.0.

brew install llvm@4
export PATH="/usr/local/opt/llvm@4/bin:$PATH"

Runtime Dependencies

LLVM is only needed for compiling the bitcode files. For running compiled bitcode files, there are no special runtime dependencies, but additional libraries might be needed if the user code has external dependencies.

In particular, for running C++ code, you need libc++ (the C++ standard library from the LLVM project).

How to get started?

First create a new directory, which will contain the needed GraalVM projects:

mkdir sulong-dev && cd sulong-dev

Then, download mx, which is the build tool used by Sulong:

git clone https://github.com/graalvm/mx
export PATH=$PWD/mx:$PATH

Next, use git to clone the Sulong project and its dependencies:

git clone https://github.com/oracle/graal

Next, you need to download a recent labsjdk. Extract it inside the sulong-dev directory:

tar -zxf labsjdk-8u172-jvmci-0.47-linux-amd64.tar.gz

Set JAVA_HOME to point to the extracted labsjdk from above:

echo JAVA_HOME=`pwd`/labsjdk1.8.0_172-jvmci-0.47 > graal/sulong/mx.sulong/env

Sulong partially consists of C/C++ code that is compiled using make. To speed up the build process you can edit the MAKEFLAGS environment variable:

echo MAKEFLAGS=-j9 >> graal/sulong/mx.sulong/env

Finally, build the project:

cd graal/sulong && mx build

The first build will take some time because mx has not only to build Sulong, but also its dependencies and primary testsuite.

Now, Sulong is ready to start. You can for example compile a C file named test.c (see further below) with clang and then use Sulong to execute it:

clang -c -emit-llvm -o test.bc test.c
mx lli test.bc

For best experience we suggest to use clang 3.8, though versions 3.2, 3.3 and 3.8 to 6.0 should also work. Additionally, if you compile with the -g option Sulong can provide source-file information in stacktraces.

You can specify additional libraries to load with the -Dpolyglot.llvm.libraries option. These can be precompiled libraries (*.so / *.dylib) as well as LLVM bitcode files. The -Dpolyglot.llvm.libraryPath option can be used to amend the search path for the specifed libraries with a relative path. Both options can be given multiple arguments separated by :.

mx lli -Dpolyglot.llvm.libraryPath=lib -Dpolyglot.llvm.libraries=liba.so test.bc

Running with the Graal compiler

In contrast to Graal VM, mx lli will by default not optimize your program. If you are interested in high performance, you might want to import the Graal compiler. To do so, first ensure that the compiler is built:

mx --dynamicimport /compiler build

Once the compiler is ready

mx --dynamicimport /compiler --jdk jvmci lli test.bc

IDE Setup

If you want to use the project from within Eclipse, use the following command to generate the Eclipse project files (there is also mx ideinit for other IDEs):

mx eclipseinit

If you want to use the project from within Intellij Idea, use the following command instead:

mx intellijinit

If you also want to edit the mx configuration files from within Idea, you can append the --mx-python-modules argument to this. Since the configuration files consist of Python code, you will probably want to install the Python Language Support Plugin.

You can also develop Sulong in Netbeans. The following command will generate the project files and print instructions on how to import them into the IDE:

mx netbeansinit

If you want to inspect the command line that mx generates for a mx command you can use the -v flag.

From where does the project name originate?

Sulong is the romanization of the Chinese term "速龙" (Velocisaurus). The first character translates as fast, rapid or quick, while the second character means dragon. A literal translation of the name giving Chinese term is thus "fast dragon". The name relates to the LLVM logo which is a dragon (more specifically a wyvern), and is also in line with the LLVM Dragonegg project.

What is LLVM?

LLVM is an umbrella project for a modular and reusable compiler infrastructure written in C++. It includes a compiler frontend clang for compiling C, C++, Objective C and Objective C++ to LLVM bitcode IR. Many of the other tools such as the optimizer opt, assembler, linker, and backends then operate on the LLVM bitcode, to finally produce machine code. LLVM envisions that transformations and analyses can be applied during compile-time, link-time, runtime, and offline.

What is Truffle?

Truffle is a language implementation framework written in Java. It allows language designers to implement a (guest) language as an Abstract Syntax Tree (AST) interpreter. Additionally, Truffle provides many language independent facilities to the host language such as profiling, debugging, and language interoperability. When a Truffle AST is executed often and then dynamically compiled with Graal, Graal can exploit its knowledge about the Truffle framework and produce efficient machine code.

Further Information

The logo was designed by Valentina Caruso.

Sulong is developed in a research collaboration with Johannes Kepler University, Linz.