+<p>This is <a href="http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13392">a bug in
+ GCC</a>, and affects projects other than LLVM. Try upgrading or downgrading
+ your GCC.</p>
+</div>
+
+<div class="question">
+<p>Compiling LLVM with GCC succeeds, but the resulting tools do not work, what
+ can be wrong?</p>
+</div>
+
+<div class="answer">
+<p>Several versions of GCC have shown a weakness in miscompiling the LLVM
+ codebase. Please consult your compiler version (<tt>gcc --version</tt>) to
+ find out whether it is <a href="GettingStarted.html#brokengcc">broken</a>.
+ If so, your only option is to upgrade GCC to a known good version.</p>
+</div>
+
+<div class="question">
+<p>After Subversion update, rebuilding gives the error "No rule to make
+ target".</p>
+</div>
+
+<div class="answer">
+<p>If the error is of the form:</p>
+
+<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="question">
+<p><a name="srcdir-objdir">When I compile LLVM-GCC with srcdir == objdir, it
+ fails. Why?</a></p>
+</div>
+
+<div class="answer">
+<p>The <tt>GNUmakefile</tt> in the top-level directory of LLVM-GCC is a special
+ <tt>Makefile</tt> used by Apple to invoke the <tt>build_gcc</tt> script after
+ setting up a special environment. This has the unforunate side-effect that
+ trying to build LLVM-GCC with srcdir == objdir in a "non-Apple way" invokes
+ the <tt>GNUmakefile</tt> instead of <tt>Makefile</tt>. Because the
+ environment isn't set up correctly to do this, the build fails.</p>
+
+<p>People not building LLVM-GCC the "Apple way" need to build LLVM-GCC with
+ srcdir != objdir, or simply remove the GNUmakefile entirely.</p>
+
+<p>We regret the inconvenience.</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>