lfs/chapter06/llvm-pass2.xml

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  <!ENTITY % general-entities SYSTEM "../general.ent">
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<sect1 id="ch-tools-llvm-pass2" role="wrap">
  <?dbhtml filename="llvm-pass2.html"?>

  <sect1info condition="script">
    <productname>LLVM</productname>
    <productnumber>&llvm-version;</productnumber>
    <address>&llvm-url;</address>
  </sect1info>

  <title>LLVM-&llvm-version; - Pass 2</title>

  <indexterm zone="ch-tools-llvm-pass2">
    <primary sortas="a-LLVM">LLVM</primary>
    <secondary>tools, pass 2</secondary>
  </indexterm>

  <sect2 role="package">
    <title/>

    <para>The LLVM package contains a collection of modular and reusable
    compiler and toolchain technologies.</para>

    <segmentedlist>
      <segtitle>&buildtime;</segtitle>
      <segtitle>&diskspace;</segtitle>

      <seglistitem>
        <seg>&llvm-tmpp2-sbu;</seg>
        <seg>&llvm-tmpp2-du;</seg>
      </seglistitem>
    </segmentedlist>

  </sect2>

  <sect2 role="installation">
    <title>Installation of LLVM</title>

    <para>Prepare some CMake modules needed by LLVM building system:</para>

<screen><userinput remap="pre">tar -xf ../llvm-cmake-&llvm-version;.src.tar.xz
mv cmake-&llvm-version;.src ../cmake</userinput></screen>

    <para>The LLVM documentation recommends building LLVM in a dedicated
    build directory:</para>

<screen><userinput remap="pre">mkdir -v build
cd       build</userinput></screen>

    <para>For cross-compiling LLVM, create a CMake toolchain description
    file:</para>

<screen><userinput remap="pre">cat &gt; cross.cmake &lt;&lt; EOF
<literal># the name of the target operating system
set(CMAKE_SYSTEM_NAME Linux)

# which compilers to use for C and C++
set(CMAKE_C_COMPILER   </literal>$LFS_TGT<literal>-gcc)
set(CMAKE_CXX_COMPILER </literal>$LFS_TGT<literal>-g++)

# where is the target environment located
set(CMAKE_FIND_ROOT_PATH  </literal>$LFS<literal>)

# adjust the default behavior of the FIND_XXX() commands:
# search programs in the host environment
set(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)

# search headers and libraries in the target environment
set(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
set(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)</literal>
EOF</userinput></screen>

    <para>Prepare LLVM for compilation:</para>

<screen><userinput remap="configure">OPTS="-DLLVM_ENABLE_FFI=OFF;\
-DLLVM_BUILD_LLVM_DYLIB=ON;\
-DLLVM_LINK_LLVM_DYLIB=ON;\
-DLLVM_ENABLE_RTTI=ON;\
-DLLVM_TARGETS_TO_BUILD=host;\
-DLLVM_INCLUDE_BENCHMARKS=OFF"

CC=gcc CXX=g++ cmake                           \
    -DCMAKE_INSTALL_PREFIX=$LFS/tools/$LFS_TGT \
    -DCMAKE_BUILD_TYPE=Release                 \
    -DCMAKE_TOOLCHAIN_FILE=cross.cmake         \
    -DLLVM_TABLEGEN=$LFS/tools/bin/llvm-tblgen \
    $(echo $OPTS | sed 's/;/ /g')              \
    -DCROSS_TOOLCHAIN_FLAGS_NATIVE=$OPTS       \
    -Wno-dev ..

unset OPTS</userinput></screen>

    <variablelist>
      <title>The meaning of the configure options:</title>

      <varlistentry>
        <term><parameter>-DLLVM_ENABLE_FFI=OFF</parameter></term>
        <listitem>
          <para>Allow building LLVM without libffi installed in $LFS.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><parameter>-DLLVM_TABLEGEN=$LFS/tools/bin/llvm-tblgen</parameter></term>
        <listitem>
          <para>Use <command>llvm-tblgen</command> from LLVM pass 1, instead
          of building it again for the host distro.</para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term>
          <command>OPTS=...</command>,
          <parameter>$(echo $OPTS | sed 's/;/ ')</parameter>, and
          <parameter>-DCROSS_TOOLCHAIN_FLAGS_NATIVE=$OPTS</parameter></term>
        <listitem>
          <para>Use the same configuration for cross compiling LLVM to
          generate <command>llvm-config</command> which is runnable on the
          host distro.  <command>llvm-config</command> will be used building
          Rustc Pass 2.  This option ensures it will correctly output the
          configuration of the cross compiled LLVM libraries.  We save the
          configuration in an environment variable to avoid typing the same
          options again.</para>
        </listitem>
      </varlistentry>
    </variablelist>

    <para>For the meaning of other CMake options, see TODO.</para>

    <para>Compile LLVM by running:</para>

<screen><userinput remap="make">make</userinput></screen>

    <para>Install the headers and shared library:</para>

<screen><userinput remap="install">DESTDIR=$PWD/dest make install
cp -av dest/$LFS/tools/$LFS_TGT/lib/libLLVM*.so \
            $LFS/tools/$LFS_TGT/lib
cp -av dest/$LFS/tools/$LFS_TGT/include/* \
            $LFS/tools/$LFS_TGT/include</userinput></screen>

    <para>Install another copy of the shared library into
    <filename class='directory'>$LFS/usr/lib</filename>, so it will be able
    to be used in the chroot environment:</para>

<screen><userinput remap="install">cp -av dest/$LFS/tools/$LFS_TGT/lib/libLLVM*.so $LFS/usr/lib</userinput></screen>

    <para>Install <command>llvm-config</command>:</para>

<screen><userinput remap="install">install -vm755 NATIVE/bin/llvm-config $LFS/tools/$LFS_TGT/bin</userinput></screen>

    <para>Clean up the source directory:</para>

<screen><userinput remap="install">rm -rf ../../cmake</userinput></screen>

  </sect2>

  <sect2 role="content">
    <title/>

    <para>Details on this package are located in
    <xref linkend="contents-llvm" role="."/></para>
  </sect2>

</sect1>