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* Moved autotools configure & build example out of "Getting Started Quickly (A Summary)" and into BuildingLLVMWithAutoTools. * Removed the annotations that CMake is the recommended process and Autotools is alternate. * Added brief documentation about build targets under "Getting Started Quickly..." * Added Overview text to BuildingLLVMWithAutotools * Fixed up a broken link. llvm-svn: 232278
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====================================
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Building LLVM With Autotools
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====================================
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.. contents::
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:local:
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Overview
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========
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This document details how to use the LLVM autotools based build system to
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configure and build LLVM from source. The normal developer process using CMake
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is detailed `here <GettingStarted.html#check-here>`_.
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A Quick Summary
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---------------
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#. Configure and build LLVM and Clang:
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* ``cd where-you-want-to-build-llvm``
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* ``mkdir build`` (for building without polluting the source dir)
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* ``cd build``
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* ``../llvm/configure [options]``
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Some common options:
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* ``--prefix=directory`` --- Specify for *directory* the full pathname of
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where you want the LLVM tools and libraries to be installed (default
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``/usr/local``).
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* ``--enable-optimized`` --- Compile with optimizations enabled (default
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is NO).
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* ``--enable-assertions`` --- Compile with assertion checks enabled
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(default is YES).
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* ``make [-j]`` --- The ``-j`` specifies the number of jobs (commands) to run
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simultaneously. This builds both LLVM and Clang for Debug+Asserts mode.
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The ``--enable-optimized`` configure option is used to specify a Release
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build.
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* ``make check-all`` --- This run the regression tests to ensure everything
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is in working order.
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* If you get an "internal compiler error (ICE)" or test failures, see
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`here <GettingStarted.html#check-here>`_.
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Local LLVM Configuration
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------------------------
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Once checked out from the Subversion repository, the LLVM suite source code must
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be configured via the ``configure`` script. This script sets variables in the
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various ``*.in`` files, most notably ``llvm/Makefile.config`` and
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``llvm/include/Config/config.h``. It also populates *OBJ_ROOT* with the
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Makefiles needed to begin building LLVM.
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The following environment variables are used by the ``configure`` script to
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configure the build system:
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+------------+-----------------------------------------------------------+
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| Variable | Purpose |
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+============+===========================================================+
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| CC | Tells ``configure`` which C compiler to use. By default, |
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| | ``configure`` will check ``PATH`` for ``clang`` and GCC C |
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| | compilers (in this order). Use this variable to override |
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| | ``configure``\'s default behavior. |
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+------------+-----------------------------------------------------------+
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| CXX | Tells ``configure`` which C++ compiler to use. By |
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| | default, ``configure`` will check ``PATH`` for |
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| | ``clang++`` and GCC C++ compilers (in this order). Use |
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| | this variable to override ``configure``'s default |
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| | behavior. |
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+------------+-----------------------------------------------------------+
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The following options can be used to set or enable LLVM specific options:
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``--enable-optimized``
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Enables optimized compilation (debugging symbols are removed and GCC
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optimization flags are enabled). Note that this is the default setting if you
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are using the LLVM distribution. The default behavior of a Subversion
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checkout is to use an unoptimized build (also known as a debug build).
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``--enable-debug-runtime``
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Enables debug symbols in the runtime libraries. The default is to strip debug
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symbols from the runtime libraries.
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``--enable-jit``
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Compile the Just In Time (JIT) compiler functionality. This is not available
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on all platforms. The default is dependent on platform, so it is best to
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explicitly enable it if you want it.
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``--enable-targets=target-option``
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Controls which targets will be built and linked into llc. The default value
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for ``target_options`` is "all" which builds and links all available targets.
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The "host" target is selected as the target of the build host. You can also
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specify a comma separated list of target names that you want available in llc.
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The target names use all lower case. The current set of targets is:
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``aarch64, arm, arm64, cpp, hexagon, mips, mipsel, mips64, mips64el, msp430,
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powerpc, nvptx, r600, sparc, systemz, x86, x86_64, xcore``.
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``--enable-doxygen``
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Look for the doxygen program and enable construction of doxygen based
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documentation from the source code. This is disabled by default because
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generating the documentation can take a long time and producess 100s of
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megabytes of output.
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To configure LLVM, follow these steps:
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#. Change directory into the object root directory:
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.. code-block:: console
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% cd OBJ_ROOT
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#. Run the ``configure`` script located in the LLVM source tree:
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.. code-block:: console
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% SRC_ROOT/configure --prefix=/install/path [other options]
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Compiling the LLVM Suite Source Code
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------------------------------------
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Once you have configured LLVM, you can build it. There are three types of
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builds:
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Debug Builds
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These builds are the default when one is using a Subversion checkout and
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types ``gmake`` (unless the ``--enable-optimized`` option was used during
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configuration). The build system will compile the tools and libraries with
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debugging information. To get a Debug Build using the LLVM distribution the
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``--disable-optimized`` option must be passed to ``configure``.
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Release (Optimized) Builds
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These builds are enabled with the ``--enable-optimized`` option to
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``configure`` or by specifying ``ENABLE_OPTIMIZED=1`` on the ``gmake`` command
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line. For these builds, the build system will compile the tools and libraries
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with GCC optimizations enabled and strip debugging information from the
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libraries and executables it generates. Note that Release Builds are default
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when using an LLVM distribution.
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Profile Builds
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These builds are for use with profiling. They compile profiling information
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into the code for use with programs like ``gprof``. Profile builds must be
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started by specifying ``ENABLE_PROFILING=1`` on the ``gmake`` command line.
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Once you have LLVM configured, you can build it by entering the *OBJ_ROOT*
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directory and issuing the following command:
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.. code-block:: console
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% gmake
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If the build fails, please `check here <GettingStarted.html#check-here>`_
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to see if you are using a version of GCC that is known not to compile LLVM.
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If you have multiple processors in your machine, you may wish to use some of the
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parallel build options provided by GNU Make. For example, you could use the
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command:
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.. code-block:: console
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% gmake -j2
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There are several special targets which are useful when working with the LLVM
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source code:
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``gmake clean``
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Removes all files generated by the build. This includes object files,
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generated C/C++ files, libraries, and executables.
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``gmake dist-clean``
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Removes everything that ``gmake clean`` does, but also removes files generated
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by ``configure``. It attempts to return the source tree to the original state
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in which it was shipped.
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``gmake install``
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Installs LLVM header files, libraries, tools, and documentation in a hierarchy
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under ``$PREFIX``, specified with ``./configure --prefix=[dir]``, which
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defaults to ``/usr/local``.
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``gmake -C runtime install-bytecode``
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Assuming you built LLVM into $OBJDIR, when this command is run, it will
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install bitcode libraries into the GCC front end's bitcode library directory.
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If you need to update your bitcode libraries, this is the target to use once
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you've built them.
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Please see the `Makefile Guide <MakefileGuide.html>`_ for further details on
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these ``make`` targets and descriptions of other targets available.
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It is also possible to override default values from ``configure`` by declaring
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variables on the command line. The following are some examples:
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``gmake ENABLE_OPTIMIZED=1``
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Perform a Release (Optimized) build.
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``gmake ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1``
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Perform a Release (Optimized) build without assertions enabled.
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``gmake ENABLE_OPTIMIZED=0``
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Perform a Debug build.
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``gmake ENABLE_PROFILING=1``
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Perform a Profiling build.
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``gmake VERBOSE=1``
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Print what ``gmake`` is doing on standard output.
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``gmake TOOL_VERBOSE=1``
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Ask each tool invoked by the makefiles to print out what it is doing on
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the standard output. This also implies ``VERBOSE=1``.
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Every directory in the LLVM object tree includes a ``Makefile`` to build it and
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any subdirectories that it contains. Entering any directory inside the LLVM
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object tree and typing ``gmake`` should rebuild anything in or below that
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directory that is out of date.
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This does not apply to building the documentation.
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LLVM's (non-Doxygen) documentation is produced with the
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`Sphinx <http://sphinx-doc.org/>`_ documentation generation system.
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There are some HTML documents that have not yet been converted to the new
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system (which uses the easy-to-read and easy-to-write
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`reStructuredText <http://sphinx-doc.org/rest.html>`_ plaintext markup
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language).
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The generated documentation is built in the ``SRC_ROOT/docs`` directory using
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a special makefile.
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For instructions on how to install Sphinx, see
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`Sphinx Introduction for LLVM Developers
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<http://lld.llvm.org/sphinx_intro.html>`_.
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After following the instructions there for installing Sphinx, build the LLVM
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HTML documentation by doing the following:
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.. code-block:: console
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$ cd SRC_ROOT/docs
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$ make -f Makefile.sphinx
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This creates a ``_build/html`` sub-directory with all of the HTML files, not
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just the generated ones.
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This directory corresponds to ``llvm.org/docs``.
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For example, ``_build/html/SphinxQuickstartTemplate.html`` corresponds to
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``llvm.org/docs/SphinxQuickstartTemplate.html``.
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The :doc:`SphinxQuickstartTemplate` is useful when creating a new document.
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Cross-Compiling LLVM
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--------------------
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It is possible to cross-compile LLVM itself. That is, you can create LLVM
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executables and libraries to be hosted on a platform different from the platform
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where they are built (a Canadian Cross build). To configure a cross-compile,
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supply the configure script with ``--build`` and ``--host`` options that are
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different. The values of these options must be legal target triples that your
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GCC compiler supports.
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The result of such a build is executables that are not runnable on on the build
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host (--build option) but can be executed on the compile host (--host option).
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Check :doc:`HowToCrossCompileLLVM` and `Clang docs on how to cross-compile in general
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<http://clang.llvm.org/docs/CrossCompilation.html>`_ for more information
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about cross-compiling.
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The Location of LLVM Object Files
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---------------------------------
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The LLVM build system is capable of sharing a single LLVM source tree among
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several LLVM builds. Hence, it is possible to build LLVM for several different
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platforms or configurations using the same source tree.
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This is accomplished in the typical autoconf manner:
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* Change directory to where the LLVM object files should live:
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.. code-block:: console
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% cd OBJ_ROOT
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* Run the ``configure`` script found in the LLVM source directory:
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.. code-block:: console
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% SRC_ROOT/configure
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The LLVM build will place files underneath *OBJ_ROOT* in directories named after
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the build type:
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Debug Builds with assertions enabled (the default)
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Tools
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``OBJ_ROOT/Debug+Asserts/bin``
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Libraries
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``OBJ_ROOT/Debug+Asserts/lib``
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Release Builds
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Tools
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``OBJ_ROOT/Release/bin``
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Libraries
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``OBJ_ROOT/Release/lib``
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Profile Builds
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Tools
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``OBJ_ROOT/Profile/bin``
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Libraries
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``OBJ_ROOT/Profile/lib``
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