Thursday, November 29, 2012

LLVM - ARM cross-compilation using Raspberry!!

Well, a short break on continuous integration posts!

I bought my Raspberry Pi ( board some weeks ago mainly to use it as a developer board (pretty affordable and efficient). So, I decided to use it to cross-compile LLVM (

So, here you go.


First of all, download LLVM (from either SVN or GIT repositories). I got the following information from  LLVM documentation. For more details, check this out!

  • Checkout LLVM:
    $ cd where-you-want-llvm-to-live
    $ svn co llvm

  • Checkout Clang:
    $ cd where-you-want-llvm-to-live
    $ cd llvm/tools
    $ svn co clang
  • Checkout Compiler-RT:
    $ cd where-you-want-llvm-to-live
    $ cd llvm/projects
    $ svn co compiler-rt
  • Get the Test Suite Source Code [Optional]
    $ cd where-you-want-llvm-to-live
    $ cd llvm/projects
    $ svn co test-suite

To cross-compile it to ARM platform, you need a toolchain. I use Sourcery G++ Lite 2011.03-41 (MentorGraphics Sourcery CodeBench Lite Edition) - it is free and contains everything we need. Install it and also remember to set the PATH variable so that you can use your toolchain.
$ export $PATH=$PATH:/home/user/CodeSourcery/Sourcery_G++_Lite/bin
Now, it´s time to build the application (and remember: for further details, check this out!)

$ cd where-you-want-to-build-llvm
$ mkdir build
(for building without polluting the source dir)
$ cd build
$ ../configure --target=arm-none-linux-gnueabi --host=arm-none-linux-gnueabi --enable-optimized (the target/host value may change depending on the toolchain that you have chosen.)
$ make

Now, you just need to wait for a couple of minutes :-) Next step is NFS-mounting the LLVM dir in your Raspberry Pi.


Now, LLVM is cross-compiled and we are able to use it and perform some tests on Raspberry Pi. I prefer NFS as partition mounting solution. An important information is that you have to have the same path on both environments (desktop and remote). It means that if you are building LLVM on /home/user/llvm desktop folder, you have to mount it on /home/user/llvm remote folder (in most of cases, you have to create the user on your Raspberry environment - just use the command).  Firstly, set up your desktop machine:
  • Install NFS packages
    @desktop$ sudo apt-get install portmap nfs-kernel-server nfs-common
  • Edit /etc/exports and add the following line
  • Restart NFS system
    @desktop$ sudo service nfs-kernel-server restart
  • Change access permission of your shared folder (in this case, I use the same folder)
    @desktop$ chmod -R 777 /home/user/llvm

Configuration on Raspberry Pi is also straightforward:

  • Install NFS packages (most of Raspberry distributions contain NFS installed, so maybe this step is not necessary)
    @remote$ sudo apt-get install portmap nfs-kernel-server nfs-common
  • Create the host folder
    @remote$ mkdir llvm
    @remote$ chmod 777 llvm
  • Mount the NFS-shared folder
    @remote$ sudo mount /home/user/llvm
Now it is done and you can use your cross-compiled LLVM on your Raspberry.


Let´s now focus on LLVM tests and how we can run them on ARM platforms. In this case, I am running tests under /home/user/llvm/tests folder.

  • CD to test dir
    @remote$ cd llvm/build/test
  • Run tests
    @remote:/home/user/llvm/build/test$ make 

After some minutes, LLVM test suite runs all integration tests and provides a report with results.

@remote:/home/user/llvm/build/test$ make
PASS: LLVM :: ExecutionEngine/MCJIT/test-shift.ll (59 of 59)
Testing Time: 11.65s
Unexpected Passing Tests (1):
    LLVM :: ExecutionEngine/MCJIT/test-data-align-remote.ll
Failing Tests (7):
    LLVM :: ExecutionEngine/MCJIT/2003-01-04-ArgumentBug.ll
    LLVM :: ExecutionEngine/MCJIT/2005-12-02-TailCallBug.ll
    LLVM :: ExecutionEngine/MCJIT/fpbitcast.ll
    LLVM :: ExecutionEngine/MCJIT/pr13727.ll
    LLVM :: ExecutionEngine/MCJIT/test-call.ll
    LLVM :: ExecutionEngine/MCJIT/test-common-symbols.ll
    LLVM :: ExecutionEngine/MCJIT/test-ret.ll
  Expected Passes    : 45
  Expected Failures  : 6
  Unexpected Passes  : 1
  Unexpected Failures: 7
UPDATE: Raspberry Pi the ARM target platform for LLVM project at this moment. If you want to contribute to LLVM project by supporting ARM features, check a PandaBoard development kit.