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Open LLVM Projects
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<ul>
<li><a href="#what">What is this?</a></li>
<li><a href="#improving">Improving the current system</a>
<ol>
<li><a href="#glibc">Port glibc to LLVM</a></li>
<li><a href="#NightlyTest">Improving the Nightly Tester</a></li>
<li><a href="#programs">Compile programs with the LLVM Compiler</a></li>
<li><a href="#llvm_ir">Extend the LLVM intermediate representation</a></li>
<li><a href="#misc_imp">Miscellaneous Improvements</a></li>
</ol></li>
<li><a href="#new">Adding new capabilities to LLVM</a>
<ol>
<li><a href="#pointeranalysis">Pointer and Alias Analysis</a></li>
<li><a href="#profileguided">Profile Guided Optimization</a></li>
<li><a href="#xforms">New Transformations and Analyses</a></li>
<li><a href="#x86be">X86 Back-end Improvements</a></li>
<li><a href="#misc_new">Miscellaneous Additions</a></li>
</ol></li>
</ul>
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<div class="doc_section">
<a name="what">What is this?</a>
</div>
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<div class="doc_text">
<p>This document is meant to be a sort of "big TODO list" for LLVM. Each
project in this document is something that would be useful for LLVM to have, and
would also be a great way to get familiar with the system. Some of these
projects are small and self-contained, which may be implemented in a couple of
days, others are larger. Several of these projects may lead to interesting
research projects in their own right. In any case, we welcome all
contributions.</p>
<p>If you are thinking about tackling one of these projects, please send a mail
to the <a href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM
Developer's</a> mailing list, so that we know the project is being worked on.
Additionally this is a good way to get more information about a specific project
or to suggest other projects to add to this page. Another good place to look
for ideas is the <a href="http://llvm.cs.uiuc.edu/bugs/">LLVM bug
tracker</a>.</p>
</div>
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<div class="doc_section">
<a name="improving">Improving the current system</a>
</div>
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<div class="doc_text">
<p>Improvements to the current infrastructure are always very welcome and tend
to be fairly straight-forward to implement. Here are some of the key areas that
can use improvement...</p>
</div>
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<div class="doc_subsection">
<a name="glibc">Port glibc to LLVM</a>
</div>
<div class="doc_text">
<p>It would be very useful to <a
href="http://www.gnu.org/software/libc/porting.html">port</a> <a
href="http://www.gnu.org/software/glibc/">glibc</a> to LLVM. This would allow a
variety of interprocedural algorithms to be much more effective in the face of
library calls. The most important pieces to port are things like the string
library and the <tt>stdio</tt> related functions... low-level system calls like
'<tt>read</tt>' should stay unimplemented in LLVM.</p>
</div>
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<div class="doc_subsection">
<a name="NightlyTest">Improving the Nightly Tester</a>
</div>
<div class="doc_text">
<p>The <a href="/testresults/">Nightly Tester</a> is a simple perl script
(located in <tt>utils/NightlyTest.pl</tt>) which runs every night to generate a
daily report. It could use the following improvements:</p>
<ol>
<li>Regression tests - We should run the regression tests in addition to the
program tests...</li>
</ol>
</div>
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<div class="doc_subsection">
<a name="programs">Compile programs with the LLVM Compiler</a>
</div>
<div class="doc_text">
<p>We are always looking for new testcases and benchmarks for use with LLVM. In
particular, it is useful to try compiling your favorite C source code with LLVM.
If it doesn't compile, try to figure out why or report it to the <a
href="http://mail.cs.uiuc.edu/pipermail/llvmbugs/">llvm-bugs</a> list. If you
get the program to compile, it would be extremely useful to convert the build
system to be compatible with the LLVM Programs testsuite so that we can check it
into CVS and the automated tester can use it to track progress of the
compiler.</p>
<p>When testing a code, try running it with a variety of optimizations, and with
all the back-ends: CBE, llc, and lli.</p>
</div>
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<div class="doc_subsection">
<a name="llvm_ir">Extend the LLVM intermediate representation</a>
</div>
<div class="doc_text">
<ol>
<li>Add a new conditional move instruction: <tt>X = select bool Cond, Y,
Z</tt></li>
<li>Add support for platform-independent prefetch support. The GCC <a
href="http://gcc.gnu.org/projects/prefetch.html">prefetch project</a> page
has a good survey of the prefetching capabilities of a variety of modern
processors.</li>
</ol>
</div>
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<div class="doc_subsection">
<a name="misc_imp">Miscellaneous Improvements</a>
</div>
<div class="doc_text">
<ol>
<li>Someone needs to look into getting the <tt>ranlib</tt> tool to index LLVM
bytecode files, so that linking in .a files is not hideously slow. They
would also then have to implement the reader for this index in
<tt>gccld</tt>.</li>
<li>Rework the PassManager to be more flexible</li>
<li>Some transformations and analyses only work on reducible flow graphs. It
would be nice to have a transformation which could be "required" by these passes
which makes irreducible graphs reducible. This can easily be accomplished
through code duplication. See <a
href="http://citeseer.nj.nec.com/janssen97making.html">Making Graphs Reducible
with Controlled Node Splitting</a> and perhaps <a
href="http://doi.acm.org/10.1145/262004.262005">Nesting of Reducible and
Irreducible Loops</a>.</li>
</ol>
</div>
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<div class="doc_section">
<a name="new">Adding new capabilities to LLVM</a>
</div>
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<div class="doc_text">
<p>Sometimes creating new things is more fun that improving existing things.
These projects tend to be more involved and perhaps require more work, but can
also be very rewarding.</p>
</div>
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<div class="doc_subsection">
<a name="pointeranalysis">Pointer and Alias Analysis</a>
</div>
<div class="doc_text">
<p>We have a <a href="AliasAnalysis.html">strong base for development</a> of
both pointer analysis based optimizations as well as pointer analyses
themselves. It seems natural to want to take advantage of this...</p>
<ol>
<li>Implement a flow-sensitive context-sensitive alias analysis algorithm<br>
- Pick one of the somewhat efficient algorithms, but strive for maximum
precision</li>
<li>Implement a flow-sensitive context-insensitive alias analysis algorithm<br>
- Just an efficient local algorithm perhaps?</li>
<li>Implement an interface to update analyses in response to common code motion
transformations</li>
<li>Implement alias-analysis-based optimizations:
<ul>
<li>Dead store elimination</li>
<li>...</li>
</ul></li>
</ol>
</div>
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<div class="doc_subsection">
<a name="profileguided">Profile Guided Optimization</a>
</div>
<div class="doc_text">
<p>We are getting to the point where we really need a unified infrastructure for
profile guided optimizations. It would be wonderful to be able to write profile
guided transformations which can be performed either at static compile time
(compile time or offline optimization time) or at runtime in a JIT type setup.
The LLVM transformation itself shouldn't need to know how it is being used.</p>
<p>Ideas for profile guided transformations:</p>
<ol>
<li>Superblock formation (with many optimizations)</li>
<li>Loop unrolling/peeling</li>
<li>Profile directed inlining</li>
<li>Code layout</li>
<li>...</li>
</ol>
</div>
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<div class="doc_subsection">
<a name="xforms">New Transformations and Analyses</a>
</div>
<div class="doc_text">
<ol>
<li>Implement a Dependence Analysis Infrastructure<br>
- Design some way to represent and query dep analysis</li>
<li>Implement a strength reduction pass</li>
<li>Value range propagation pass</li>
<li>Implement an unswitching pass</li>
<li>Write a loop unroller, with a simple heuristic for when to unroll</li>
</ol>
</div>
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<div class="doc_section">
<a name="x86be">X86 Back-end Improvements</a>
</div>
<div class="doc_text">
<ol>
<li>Implement a global register allocator</li>
<li>Implement a better instruction selector</li>
<li>Implement support for the "switch" instruction without requiring the
lower-switches pass.</li>
</ol>
</div>
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<div class="doc_subsection">
<a name="misc_new">Miscellaneous Additions</a>
</div>
<div class="doc_text">
<ol>
<li>Write a new frontend for some language (Java? OCaml? Forth?)</li>
<li>Write a new backend for a target (IA64? MIPS? MMIX?)</li>
</ol>
</div>
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<hr>
<div class="doc_footer">
<address><a href="mailto:sabre@nondot.org">Chris Lattner</a></address>
<a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a>
<br>
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