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| <title>Advice on Packaging LLVM</title> |
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| |
| <h1>Advice on Packaging LLVM</h1> |
| <ol> |
| <li><a href="#overview">Overview</a></li> |
| <li><a href="#compilation">Compile Flags</a></li> |
| <li><a href="#cxx-features">C++ Features</a></li> |
| <li><a href="#shared-library">Shared Library</a></li> |
| <li><a href="#deps">Dependencies</a></li> |
| </ol> |
| |
| <!--=========================================================================--> |
| <h2><a name="overview">Overview</a></h2> |
| <!--=========================================================================--> |
| <div> |
| |
| <p>LLVM sets certain default configure options to make sure our developers don't |
| break things for constrained platforms. These settings are not optimal for most |
| desktop systems, and we hope that packagers (e.g., Redhat, Debian, MacPorts, |
| etc.) will tweak them. This document lists settings we suggest you tweak. |
| </p> |
| |
| <p>LLVM's API changes with each release, so users are likely to want, for |
| example, both LLVM-2.6 and LLVM-2.7 installed at the same time to support apps |
| developed against each. |
| </p> |
| </div> |
| |
| <!--=========================================================================--> |
| <h2><a name="compilation">Compile Flags</a></h2> |
| <!--=========================================================================--> |
| <div> |
| |
| <p>LLVM runs much more quickly when it's optimized and assertions are removed. |
| However, such a build is currently incompatible with users who build without |
| defining NDEBUG, and the lack of assertions makes it hard to debug problems in |
| user code. We recommend allowing users to install both optimized and debug |
| versions of LLVM in parallel. The following configure flags are relevant: |
| </p> |
| |
| <dl> |
| <dt><tt>--disable-assertions</tt></dt><dd>Builds LLVM with <tt>NDEBUG</tt> |
| defined. Changes the LLVM ABI. Also available by setting |
| <tt>DISABLE_ASSERTIONS=0|1</tt> in <tt>make</tt>'s environment. This defaults |
| to enabled regardless of the optimization setting, but it slows things |
| down.</dd> |
| |
| <dt><tt>--enable-debug-symbols</tt></dt><dd>Builds LLVM with <tt>-g</tt>. |
| Also available by setting <tt>DEBUG_SYMBOLS=0|1</tt> in <tt>make</tt>'s |
| environment. This defaults to disabled when optimizing, so you should turn it |
| back on to let users debug their programs.</dd> |
| |
| <dt><tt>--enable-optimized</tt></dt><dd>(For svn checkouts) Builds LLVM with |
| <tt>-O2</tt> and, by default, turns off debug symbols. Also available by |
| setting <tt>ENABLE_OPTIMIZED=0|1</tt> in <tt>make</tt>'s environment. This |
| defaults to enabled when not in a checkout.</dd> |
| </dl> |
| </div> |
| |
| <!--=========================================================================--> |
| <h2><a name="cxx-features">C++ Features</a></h2> |
| <!--=========================================================================--> |
| <div> |
| |
| <dl> |
| <dt>RTTI</dt><dd>LLVM disables RTTI by default. Add <tt>REQUIRES_RTTI=1</tt> |
| to your environment while running <tt>make</tt> to re-enable it. This will |
| allow users to build with RTTI enabled and still inherit from LLVM |
| classes.</dd> |
| </dl> |
| </div> |
| |
| <!--=========================================================================--> |
| <h2><a name="shared-library">Shared Library</a></h2> |
| <!--=========================================================================--> |
| <div> |
| |
| <p>Configure with <tt>--enable-shared</tt> to build |
| <tt>libLLVM-<var>major</var>.<var>minor</var>.(so|dylib)</tt> and link the tools |
| against it. This saves lots of binary size at the cost of some startup time. |
| </p> |
| </div> |
| |
| <!--=========================================================================--> |
| <h2><a name="deps">Dependencies</a></h2> |
| <!--=========================================================================--> |
| <div> |
| |
| <dl> |
| <dt><tt>--enable-libffi</tt></dt><dd>Depend on <a |
| href="http://sources.redhat.com/libffi/">libffi</a> to allow the LLVM |
| interpreter to call external functions.</dd> |
| <dt><tt>--with-oprofile</tt></dt><dd>Depend on <a |
| href="http://oprofile.sourceforge.net/doc/devel/index.html">libopagent</a> |
| (>=version 0.9.4) to let the LLVM JIT tell oprofile about function addresses and |
| line numbers.</dd> |
| </dl> |
| </div> |
| |
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| Last modified: $Date: 2011-04-22 20:30:22 -0400 (Fri, 22 Apr 2011) $ |
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