+<pre class="doc_code">
+gmake[2]: *** No rule to make target `/path/to/somefile', needed by
+`/path/to/another/file.d'.<br>
+Stop.
+</pre>
+
+<p>This may occur anytime files are moved within the Subversion repository or
+removed entirely. In this case, the best solution is to erase all
+<tt>.d</tt> files, which list dependencies for source files, and rebuild:</p>
+
+<pre class="doc_code">
+% cd $LLVM_OBJ_DIR
+% rm -f `find . -name \*\.d`
+% gmake
+</pre>
+
+<p>In other cases, it may be necessary to run <tt>make clean</tt> before
+rebuilding.</p>
+</div>
+
+<div class="question"><p><a name="llvmc">
+The <tt>llvmc</tt> program gives me errors/doesn't work.</a></p>
+</div>
+
+<div class="answer">
+<p><tt>llvmc</tt> is experimental and isn't really supported. We suggest
+using <tt>llvm-gcc</tt> instead.</p>
+</div>
+
+<!-- *********************************************************************** -->
+<div class="doc_section"><a name="felangs">Source Languages</a></div>
+
+<div class="question"><p>
+ <a name="langs">What source languages are supported?</a></p>
+</div>
+<div class="answer">
+ <p>LLVM currently has full support for C and C++ source languages. These are
+ available through a special version of GCC that LLVM calls the
+ <a href="#cfe">C Front End</a></p>
+ <p>There is an incomplete version of a Java front end available in the
+ <tt>java</tt> module. There is no documentation on this yet so
+ you'll need to download the code, compile it, and try it.</p>
+ <p>The PyPy developers are working on integrating LLVM into the PyPy backend
+ so that PyPy language can translate to LLVM.</p>
+</div>
+
+<div class="question"><p><a name="langirgen">
+ I'd like to write a self-hosting LLVM compiler. How should I interface with
+ the LLVM middle-end optimizers and back-end code generators?
+</a></p></div>
+<div class="answer">
+ <p>Your compiler front-end will communicate with LLVM by creating a module in
+ the LLVM intermediate representation (IR) format. Assuming you want to
+ write your language's compiler in the language itself (rather than C++),
+ there are 3 major ways to tackle generating LLVM IR from a front-end:</p>
+ <ul>
+ <li>
+ <strong>Call into the LLVM libraries code using your language's FFI
+ (foreign function interface).</strong>
+ <ul>
+ <li><em>for:</em> best tracks changes to the LLVM IR, .ll syntax,
+ and .bc format</li>
+ <li><em>for:</em> enables running LLVM optimization passes without a
+ emit/parse overhead</li>
+ <li><em>for:</em> adapts well to a JIT context</li>
+ <li><em>against:</em> lots of ugly glue code to write</li>
+ </ul>
+ </li>
+ <li>
+ <strong>Emit LLVM assembly from your compiler's native language.</strong>
+ <ul>
+ <li><em>for:</em> very straightforward to get started</li>
+ <li><em>against:</em> the .ll parser is slower than the bitcode reader
+ when interfacing to the middle end</li>
+ <li><em>against:</em> you'll have to re-engineer the LLVM IR object
+ model and asm writer in your language</li>
+ <li><em>against:</em> it may be harder to track changes to the IR</li>
+ </ul>
+ </li>
+ <li>
+ <strong>Emit LLVM bitcode from your compiler's native language.</strong>
+ <ul>
+ <li><em>for:</em> can use the more-efficient bitcode reader when
+ interfacing to the middle end</li>
+ <li><em>against:</em> you'll have to re-engineer the LLVM IR object
+ model and bitcode writer in your language</li>
+ <li><em>against:</em> it may be harder to track changes to the IR</li>
+ </ul>
+ </li>
+ </ul>
+ <p>If you go with the first option, the C bindings in include/llvm-c should
+ help a lot, since most languages have strong support for interfacing with
+ C. The most common hurdle with calling C from managed code is interfacing
+ with the garbage collector. The C interface was designed to require very
+ little memory management, and so is straightforward in this regard.</p>
+</div>
+
+<div class="question"><p><a name="langhlsupp">
+ What support is there for a higher level source language constructs for
+ building a compiler?</a></p>
+</div>
+<div class="answer">
+ <p>Currently, there isn't much. LLVM supports an intermediate representation
+ which is useful for code representation but will not support the high level
+ (abstract syntax tree) representation needed by most compilers. There are no
+ facilities for lexical nor semantic analysis. There is, however, a <i>mostly
+ implemented</i> configuration-driven
+ <a href="CompilerDriver.html">compiler driver</a> which simplifies the task
+ of running optimizations, linking, and executable generation.</p>
+</div>
+
+<div class="question"><p><a name="getelementptr">
+ I don't understand the GetElementPtr instruction. Help!</a></p>
+</div>
+<div class="answer">
+ <p>See <a href="GetElementPtr.html">The Often Misunderstood GEP
+ Instruction</a>.</p>