Download Cilk

The latest version of the Cilk system consists of the Tapir/LLVM compiler and the Intel Cilk Plus runtime library. This version has been tested on x86-64 systems running recent distributions of Linux, including Ubuntu 16.04 and Fedora 24.

The Tapir/LLVM compiler is the newest compiler that supports Cilk. Tapir/LLVM extends LLVM and Clang with support for the Cilk keywords, Cilk reducer hyperobjects, and a version of the grainsize pragma for cilk_for loops. The Tapir/LLVM compiler implements the Tapir extension of LLVM’s intermediate representation (Schardl, Moses, & Leiserson, 2017) to compile task-parallel programs more efficiently than previous compilers. Tapir/LLVM also includes the Cilksan determinacy-race detector, which is guaranteed to find a race if one exists or certify the absence of races in a program execution.

The current release of the Tapir/LLVM compiler is version 1.0-3. This release is based on version 5 of LLVM and Clang. The source for an experimental version of Tapir/LLVM, based on version 6.0 of LLVM and Clang, is available on GitHub.

Debian package

For x86-64 systems running Debian or Ubuntu, binaries for Tapir/LLVM are available via the following package: [amd64]. You can install this package using apt as follows:

$ sudo apt-get install ./tapir_1.0-3_amd64.deb

Mac OS X installation

You can install Tapir/LLVM on Mac OS X using Homebrew.

This installation process is currently under development. Your mileage might vary.
$ brew install wsmoses/tools/cilkrts
$ brew install wsmoses/tools/tapir


You can download the Tapir/LLVM source code Plus runtime system separately.

Building Tapir/LLVM involves building the LLVM and Clang systems that they extend. To build Tapir/LLVM from source, you will need a C/C++ compiler and a recent version of cmake. See for more information on building LLVM and Clang.

Building the LLVM and Clang systems considers significant computing resources. We have found that building a Release build of LLVM and Clang requires approximately 50 GB of disk space and 12 GB of main memory to compile. A fresh build can take substantial time to complete as well, e.g., approximately an hour on one processor of an AWS c4.8xlarge instance.

Quick start

The Tapir-Meta repository on GitHub provides a simple means for downloading and building Tapir/LLVM compiler and its companion repositories, via the following commands:

$ git clone --recursive
$ cd Tapir-Meta/
$ ./ release
$ source ./

The build script will attempt to use parallel processors to speed up compilation.

Build guide

The source code for the Tapir/LLVM compiler consists of several integrated repositories. The repository structure reflects that of LLVM itself.

  • The Tapir-LLVM repository houses the Tapir fork of LLVM. This fork implements the Tapir extensions to LLVM’s intermediate representation. This fork also implements support for the CSI tool framework.

  • The Tapir-Clang repository houses the Tapir fork of LLVM’s Clang front-end. This fork implements support for Cilk and generates LLVM IR with Tapir from Cilk’s parallel language constructs.

  • The Tapir-compiler-rt repository houses the fork of LLVM’s compiler-rt repository. This fork includes the source code of the Cilksan and Cilkscale tools. This fork also includes the runtime for the CSI framework.

  • The Tapir-Polly repository houses the fork of LLVM’s Polly repository. This fork implements extensions to Polly to generate Tapir intermediate representation for parallel loops.

For LLVM repositories that do not have a custom fork, Tapir/LLVM should be able to work with the existing LLVM repository natively.

The following instructions will check out this collection of repositories appropriately in the current directory:

$ git clone src
$ git clone src/tools/clang
$ git clone src/projects/compiler-rt
$ git clone src/tools/polly

To build Tapir/LLVM, you will need the following executables and libraries:

  • CMake, version 3.4.3 or newer, and a C++ compiler that supports C++11, are needed to build Tapir/LLVM.

  • The Snappy compression/decompression library is needed to build and run Cilksan. Many platforms provide a package for installing Snappy, e.g., libsnappy-dev on Ubuntu, snappy-devel on Fedora, or brew install snappy on Mac OS X.

  • Binutils is needed to use link-time optimization (LTO). Many platforms provide a package for to install binutils, e.g., binutils-dev on Ubuntu, or binutils-devel on Fedora.

After checking out these repositories, you can build Tapir/LLVM from source using the following command.

$ mkdir src/build
$ cd src/build
$ cmake --build .

Additional build-configuration options are available. Please see for more information.


  1. Schardl, T. B., Moses, W. S., & Leiserson, C. E. (2017). Tapir: Embedding Fork-Join Parallelism into LLVM’s Intermediate Representation. In PPoPP (pp. 249–265). ACM.

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