mirror of
https://github.com/RPCS3/llvm-mirror.git
synced 2024-11-25 12:12:47 +01:00
176 lines
6.1 KiB
ReStructuredText
176 lines
6.1 KiB
ReStructuredText
===================================================================
|
|
How To Cross-Compile Clang/LLVM using Clang/LLVM
|
|
===================================================================
|
|
|
|
Introduction
|
|
============
|
|
|
|
This document contains information about building LLVM and
|
|
Clang on host machine, targeting another platform.
|
|
|
|
For more information on how to use Clang as a cross-compiler,
|
|
please check http://clang.llvm.org/docs/CrossCompilation.html.
|
|
|
|
TODO: Add MIPS and other platforms to this document.
|
|
|
|
Cross-Compiling from x86_64 to ARM
|
|
==================================
|
|
|
|
In this use case, we'll be using CMake and Ninja, on a Debian-based Linux
|
|
system, cross-compiling from an x86_64 host (most Intel and AMD chips
|
|
nowadays) to a hard-float ARM target (most ARM targets nowadays).
|
|
|
|
The packages you'll need are:
|
|
|
|
* ``cmake``
|
|
* ``ninja-build`` (from backports in Ubuntu)
|
|
* ``gcc-4.7-arm-linux-gnueabihf``
|
|
* ``gcc-4.7-multilib-arm-linux-gnueabihf``
|
|
* ``binutils-arm-linux-gnueabihf``
|
|
* ``libgcc1-armhf-cross``
|
|
* ``libsfgcc1-armhf-cross``
|
|
* ``libstdc++6-armhf-cross``
|
|
* ``libstdc++6-4.7-dev-armhf-cross``
|
|
|
|
Configuring CMake
|
|
-----------------
|
|
|
|
For more information on how to configure CMake for LLVM/Clang,
|
|
see :doc:`CMake`.
|
|
|
|
The CMake options you need to add are:
|
|
* ``-DCMAKE_CROSSCOMPILING=True``
|
|
* ``-DCMAKE_INSTALL_PREFIX=<install-dir>``
|
|
* ``-DLLVM_TABLEGEN=<path-to-host-bin>/llvm-tblgen``
|
|
* ``-DCLANG_TABLEGEN=<path-to-host-bin>/clang-tblgen``
|
|
* ``-DLLVM_DEFAULT_TARGET_TRIPLE=arm-linux-gnueabihf``
|
|
* ``-DLLVM_TARGET_ARCH=ARM``
|
|
* ``-DLLVM_TARGETS_TO_BUILD=ARM``
|
|
* ``-DCMAKE_CXX_FLAGS='-target armv7a-linux-gnueabihf -mcpu=cortex-a9 -I/usr/arm-linux-gnueabihf/include/c++/4.7.2/arm-linux-gnueabihf/ -I/usr/arm-linux-gnueabihf/include/ -mfloat-abi=hard -ccc-gcc-name arm-linux-gnueabihf-gcc'``
|
|
|
|
The TableGen options are required to compile it with the host compiler,
|
|
so you'll need to compile LLVM (or at least ``llvm-tblgen``) to your host
|
|
platform before you start. The CXX flags define the target, cpu (which
|
|
defaults to ``fpu=VFP3`` with NEON), and forcing the hard-float ABI. If you're
|
|
using Clang as a cross-compiler, you will *also* have to set ``-ccc-gcc-name``,
|
|
to make sure it picks the correct linker.
|
|
|
|
Most of the time, what you want is to have a native compiler to the
|
|
platform itself, but not others. It might not even be feasible to
|
|
produce x86 binaries from ARM targets, so there's no point in compiling
|
|
all back-ends. For that reason, you should also set the
|
|
``TARGETS_TO_BUILD`` to only build the ARM back-end.
|
|
|
|
You must set the ``CMAKE_INSTALL_PREFIX``, otherwise a ``ninja install``
|
|
will copy ARM binaries to your root filesystem, which is not what you
|
|
want.
|
|
|
|
Hacks
|
|
-----
|
|
|
|
There are some bugs in current LLVM, which require some fiddling before
|
|
running CMake:
|
|
|
|
#. If you're using Clang as the cross-compiler, there is a problem in
|
|
the LLVM ARM back-end that is producing absolute relocations on
|
|
position-independent code (``R_ARM_THM_MOVW_ABS_NC``), so for now, you
|
|
should disable PIC:
|
|
|
|
.. code-block:: bash
|
|
|
|
-DLLVM_ENABLE_PIC=False
|
|
|
|
This is not a problem, since Clang/LLVM libraries are statically
|
|
linked anyway, it shouldn't affect much.
|
|
|
|
#. The ARM libraries won't be installed in your system, and possibly
|
|
not easily installable anyway, so you'll have to build/download
|
|
them separately. But the CMake prepare step, which checks for
|
|
dependencies, will check the *host* libraries, not the *target*
|
|
ones.
|
|
|
|
A quick way of getting the libraries is to download them from
|
|
a distribution repository, like Debian (http://packages.debian.org/wheezy/),
|
|
and download the missing libraries. Note that the ``libXXX``
|
|
will have the shared objects (``.so``) and the ``libXXX-dev`` will
|
|
give you the headers and the static (``.a``) library. Just in
|
|
case, download both.
|
|
|
|
The ones you need for ARM are: ``libtinfo``, ``zlib1g``,
|
|
``libxml2`` and ``liblzma``. In the Debian repository you'll
|
|
find downloads for all architectures.
|
|
|
|
After you download and unpack all ``.deb`` packages, copy all
|
|
``.so`` and ``.a`` to a directory, make the appropriate
|
|
symbolic links (if necessary), and add the relevant ``-L``
|
|
and ``-I`` paths to ``-DCMAKE_CXX_FLAGS`` above.
|
|
|
|
|
|
Running CMake and Building
|
|
--------------------------
|
|
|
|
Finally, if you're using your platform compiler, run:
|
|
|
|
.. code-block:: bash
|
|
|
|
$ cmake -G Ninja <source-dir> <options above>
|
|
|
|
If you're using Clang as the cross-compiler, run:
|
|
|
|
.. code-block:: bash
|
|
|
|
$ CC='clang' CXX='clang++' cmake -G Ninja <source-dir> <options above>
|
|
|
|
If you have ``clang``/``clang++`` on the path, it should just work, and special
|
|
Ninja files will be created in the build directory. I strongly suggest
|
|
you to run ``cmake`` on a separate build directory, *not* inside the
|
|
source tree.
|
|
|
|
To build, simply type:
|
|
|
|
.. code-block:: bash
|
|
|
|
$ ninja
|
|
|
|
It should automatically find out how many cores you have, what are
|
|
the rules that needs building and will build the whole thing.
|
|
|
|
You can't run ``ninja check-all`` on this tree because the created
|
|
binaries are targeted to ARM, not x86_64.
|
|
|
|
Installing and Using
|
|
--------------------
|
|
|
|
After the LLVM/Clang has built successfully, you should install it
|
|
via:
|
|
|
|
.. code-block:: bash
|
|
|
|
$ ninja install
|
|
|
|
which will create a sysroot on the install-dir. You can then tar
|
|
that directory into a binary with the full triple name (for easy
|
|
identification), like:
|
|
|
|
.. code-block:: bash
|
|
|
|
$ ln -sf <install-dir> arm-linux-gnueabihf-clang
|
|
$ tar zchf arm-linux-gnueabihf-clang.tar.gz arm-linux-gnueabihf-clang
|
|
|
|
If you copy that tarball to your target board, you'll be able to use
|
|
it for running the test-suite, for example. Follow the guidelines at
|
|
http://llvm.org/docs/lnt/quickstart.html, unpack the tarball in the
|
|
test directory, and use options:
|
|
|
|
.. code-block:: bash
|
|
|
|
$ ./sandbox/bin/python sandbox/bin/lnt runtest nt \
|
|
--sandbox sandbox \
|
|
--test-suite `pwd`/test-suite \
|
|
--cc `pwd`/arm-linux-gnueabihf-clang/bin/clang \
|
|
--cxx `pwd`/arm-linux-gnueabihf-clang/bin/clang++
|
|
|
|
Remember to add the ``-jN`` options to ``lnt`` to the number of CPUs
|
|
on your board. Also, the path to your clang has to be absolute, so
|
|
you'll need the `pwd` trick above.
|