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diff --git a/docs/BuildingLLVMWithAutotools.rst b/docs/BuildingLLVMWithAutotools.rst new file mode 100644 index 0000000..4c04f1e --- /dev/null +++ b/docs/BuildingLLVMWithAutotools.rst @@ -0,0 +1,332 @@ +==================================== +Building LLVM With Autotools +==================================== + +.. contents:: + :local: + +Overview +======== + +This document details how to use the LLVM autotools based build system to +configure and build LLVM from source. The normal developer process using CMake +is detailed `here <GettingStarted.html#check-here>`_. + +A Quick Summary +--------------- + +#. Configure and build LLVM and Clang: + + * ``cd where-you-want-to-build-llvm`` + * ``mkdir build`` (for building without polluting the source dir) + * ``cd build`` + * ``../llvm/configure [options]`` + Some common options: + + * ``--prefix=directory`` --- Specify for *directory* the full pathname of + where you want the LLVM tools and libraries to be installed (default + ``/usr/local``). + + * ``--enable-optimized`` --- Compile with optimizations enabled (default + is NO). + + * ``--enable-assertions`` --- Compile with assertion checks enabled + (default is YES). + + * ``make [-j]`` --- The ``-j`` specifies the number of jobs (commands) to run + simultaneously. This builds both LLVM and Clang for Debug+Asserts mode. + The ``--enable-optimized`` configure option is used to specify a Release + build. + + * ``make check-all`` --- This run the regression tests to ensure everything + is in working order. + + * If you get an "internal compiler error (ICE)" or test failures, see + `here <GettingStarted.html#check-here>`_. + +Local LLVM Configuration +------------------------ + +Once checked out from the Subversion repository, the LLVM suite source code must +be configured via the ``configure`` script. This script sets variables in the +various ``*.in`` files, most notably ``llvm/Makefile.config`` and +``llvm/include/Config/config.h``. It also populates *OBJ_ROOT* with the +Makefiles needed to begin building LLVM. + +The following environment variables are used by the ``configure`` script to +configure the build system: + ++------------+-----------------------------------------------------------+ +| Variable | Purpose | ++============+===========================================================+ +| CC | Tells ``configure`` which C compiler to use. By default, | +| | ``configure`` will check ``PATH`` for ``clang`` and GCC C | +| | compilers (in this order). Use this variable to override | +| | ``configure``\'s default behavior. | ++------------+-----------------------------------------------------------+ +| CXX | Tells ``configure`` which C++ compiler to use. By | +| | default, ``configure`` will check ``PATH`` for | +| | ``clang++`` and GCC C++ compilers (in this order). Use | +| | this variable to override ``configure``'s default | +| | behavior. | ++------------+-----------------------------------------------------------+ + +The following options can be used to set or enable LLVM specific options: + +``--enable-optimized`` + + Enables optimized compilation (debugging symbols are removed and GCC + optimization flags are enabled). Note that this is the default setting if you + are using the LLVM distribution. The default behavior of a Subversion + checkout is to use an unoptimized build (also known as a debug build). + +``--enable-debug-runtime`` + + Enables debug symbols in the runtime libraries. The default is to strip debug + symbols from the runtime libraries. + +``--enable-jit`` + + Compile the Just In Time (JIT) compiler functionality. This is not available + on all platforms. The default is dependent on platform, so it is best to + explicitly enable it if you want it. + +``--enable-targets=target-option`` + + Controls which targets will be built and linked into llc. The default value + for ``target_options`` is "all" which builds and links all available targets. + The "host" target is selected as the target of the build host. You can also + specify a comma separated list of target names that you want available in llc. + The target names use all lower case. The current set of targets is: + + ``aarch64, arm, arm64, cpp, hexagon, mips, mipsel, mips64, mips64el, msp430, + powerpc, nvptx, r600, sparc, systemz, x86, x86_64, xcore``. + +``--enable-doxygen`` + + Look for the doxygen program and enable construction of doxygen based + documentation from the source code. This is disabled by default because + generating the documentation can take a long time and producess 100s of + megabytes of output. + +To configure LLVM, follow these steps: + +#. Change directory into the object root directory: + + .. code-block:: console + + % cd OBJ_ROOT + +#. Run the ``configure`` script located in the LLVM source tree: + + .. code-block:: console + + % SRC_ROOT/configure --prefix=/install/path [other options] + +Compiling the LLVM Suite Source Code +------------------------------------ + +Once you have configured LLVM, you can build it. There are three types of +builds: + +Debug Builds + + These builds are the default when one is using a Subversion checkout and + types ``gmake`` (unless the ``--enable-optimized`` option was used during + configuration). The build system will compile the tools and libraries with + debugging information. To get a Debug Build using the LLVM distribution the + ``--disable-optimized`` option must be passed to ``configure``. + +Release (Optimized) Builds + + These builds are enabled with the ``--enable-optimized`` option to + ``configure`` or by specifying ``ENABLE_OPTIMIZED=1`` on the ``gmake`` command + line. For these builds, the build system will compile the tools and libraries + with GCC optimizations enabled and strip debugging information from the + libraries and executables it generates. Note that Release Builds are default + when using an LLVM distribution. + +Profile Builds + + These builds are for use with profiling. They compile profiling information + into the code for use with programs like ``gprof``. Profile builds must be + started by specifying ``ENABLE_PROFILING=1`` on the ``gmake`` command line. + +Once you have LLVM configured, you can build it by entering the *OBJ_ROOT* +directory and issuing the following command: + +.. code-block:: console + + % gmake + +If the build fails, please `check here <GettingStarted.html#check-here>`_ +to see if you are using a version of GCC that is known not to compile LLVM. + +If you have multiple processors in your machine, you may wish to use some of the +parallel build options provided by GNU Make. For example, you could use the +command: + +.. code-block:: console + + % gmake -j2 + +There are several special targets which are useful when working with the LLVM +source code: + +``gmake clean`` + + Removes all files generated by the build. This includes object files, + generated C/C++ files, libraries, and executables. + +``gmake dist-clean`` + + Removes everything that ``gmake clean`` does, but also removes files generated + by ``configure``. It attempts to return the source tree to the original state + in which it was shipped. + +``gmake install`` + + Installs LLVM header files, libraries, tools, and documentation in a hierarchy + under ``$PREFIX``, specified with ``./configure --prefix=[dir]``, which + defaults to ``/usr/local``. + +``gmake -C runtime install-bytecode`` + + Assuming you built LLVM into $OBJDIR, when this command is run, it will + install bitcode libraries into the GCC front end's bitcode library directory. + If you need to update your bitcode libraries, this is the target to use once + you've built them. + +Please see the `Makefile Guide <MakefileGuide.html>`_ for further details on +these ``make`` targets and descriptions of other targets available. + +It is also possible to override default values from ``configure`` by declaring +variables on the command line. The following are some examples: + +``gmake ENABLE_OPTIMIZED=1`` + + Perform a Release (Optimized) build. + +``gmake ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1`` + + Perform a Release (Optimized) build without assertions enabled. + +``gmake ENABLE_OPTIMIZED=0`` + + Perform a Debug build. + +``gmake ENABLE_PROFILING=1`` + + Perform a Profiling build. + +``gmake VERBOSE=1`` + + Print what ``gmake`` is doing on standard output. + +``gmake TOOL_VERBOSE=1`` + + Ask each tool invoked by the makefiles to print out what it is doing on + the standard output. This also implies ``VERBOSE=1``. + +Every directory in the LLVM object tree includes a ``Makefile`` to build it and +any subdirectories that it contains. Entering any directory inside the LLVM +object tree and typing ``gmake`` should rebuild anything in or below that +directory that is out of date. + +This does not apply to building the documentation. +LLVM's (non-Doxygen) documentation is produced with the +`Sphinx <http://sphinx-doc.org/>`_ documentation generation system. +There are some HTML documents that have not yet been converted to the new +system (which uses the easy-to-read and easy-to-write +`reStructuredText <http://sphinx-doc.org/rest.html>`_ plaintext markup +language). +The generated documentation is built in the ``SRC_ROOT/docs`` directory using +a special makefile. +For instructions on how to install Sphinx, see +`Sphinx Introduction for LLVM Developers +<http://lld.llvm.org/sphinx_intro.html>`_. +After following the instructions there for installing Sphinx, build the LLVM +HTML documentation by doing the following: + +.. code-block:: console + + $ cd SRC_ROOT/docs + $ make -f Makefile.sphinx + +This creates a ``_build/html`` sub-directory with all of the HTML files, not +just the generated ones. +This directory corresponds to ``llvm.org/docs``. +For example, ``_build/html/SphinxQuickstartTemplate.html`` corresponds to +``llvm.org/docs/SphinxQuickstartTemplate.html``. +The :doc:`SphinxQuickstartTemplate` is useful when creating a new document. + +Cross-Compiling LLVM +-------------------- + +It is possible to cross-compile LLVM itself. That is, you can create LLVM +executables and libraries to be hosted on a platform different from the platform +where they are built (a Canadian Cross build). To configure a cross-compile, +supply the configure script with ``--build`` and ``--host`` options that are +different. The values of these options must be legal target triples that your +GCC compiler supports. + +The result of such a build is executables that are not runnable on on the build +host (--build option) but can be executed on the compile host (--host option). + +Check :doc:`HowToCrossCompileLLVM` and `Clang docs on how to cross-compile in general +<http://clang.llvm.org/docs/CrossCompilation.html>`_ for more information +about cross-compiling. + +The Location of LLVM Object Files +--------------------------------- + +The LLVM build system is capable of sharing a single LLVM source tree among +several LLVM builds. Hence, it is possible to build LLVM for several different +platforms or configurations using the same source tree. + +This is accomplished in the typical autoconf manner: + +* Change directory to where the LLVM object files should live: + + .. code-block:: console + + % cd OBJ_ROOT + +* Run the ``configure`` script found in the LLVM source directory: + + .. code-block:: console + + % SRC_ROOT/configure + +The LLVM build will place files underneath *OBJ_ROOT* in directories named after +the build type: + +Debug Builds with assertions enabled (the default) + + Tools + + ``OBJ_ROOT/Debug+Asserts/bin`` + + Libraries + + ``OBJ_ROOT/Debug+Asserts/lib`` + +Release Builds + + Tools + + ``OBJ_ROOT/Release/bin`` + + Libraries + + ``OBJ_ROOT/Release/lib`` + +Profile Builds + + Tools + + ``OBJ_ROOT/Profile/bin`` + + Libraries + + ``OBJ_ROOT/Profile/lib`` |