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| <div class="doc_title"> |
| Open LLVM Projects |
| </div> |
| |
| <ul> |
| <li><a href="#what">What is this?</a></li> |
| <li><a href="#improving">Improving the current system</a> |
| <ol> |
| <li><a href="#code-cleanups">Implementing Code Cleanup bugs</a></li> |
| <li><a href="#glibc">Port glibc to LLVM</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="#target">Target backend improvements</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="#newfeaturebugs">Implementing new feature PRs</a></li> |
| <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> |
| |
| <div class="doc_author"> |
| <p>Written by the <a href="http://llvm.cs.uiuc.edu/">LLVM Team</a></p> |
| </div> |
| |
| |
| <!-- *********************************************************************** --> |
| <div class="doc_section"> |
| <a name="what">What is this?</a> |
| </div> |
| <!-- *********************************************************************** --> |
| |
| <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. |
| </p> |
| |
| <p>The projects in this page are open-ended. More specific projects are |
| filed as unassigned enhancements in the <a href="http://llvm.cs.uiuc.edu/bugs/"> |
| LLVM bug tracker</a>. See the <a href="http://llvm.cs.uiuc.edu/bugs/buglist.cgi?keywords_type=allwords&keywords=&bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED&bug_severity=enhancement&emailassigned_to1=1&emailtype1=substring&email1=unassigned">list of currently outstanding issues</a> if you wish to help improve LLVM.</p> |
| |
| </div> |
| |
| <!-- *********************************************************************** --> |
| <div class="doc_section"> |
| <a name="improving">Improving the current system</a> |
| </div> |
| <!-- *********************************************************************** --> |
| |
| <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> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="code-cleanups">Implementing Code Cleanup bugs</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <p> |
| The <a href="http://llvm.cs.uiuc.edu/bugs/">LLVM bug tracker</a> occasionally |
| has <a |
| href="http://llvm.cs.uiuc.edu/bugs/buglist.cgi?short_desc_type=allwordssubstr&short_desc=&long_desc_type=allwordssubstr&long_desc=&bug_file_loc_type=allwordssubstr&bug_file_loc=&status_whiteboard_type=allwordssubstr&status_whiteboard=&keywords_type=allwords&keywords=code-cleanup&bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED&emailassigned_to1=1&emailtype1=substring&email1=&emailassigned_to2=1&emailreporter2=1&emailcc2=1&emailtype2=substring&email2=&bugidtype=include&bug_id=&votes=&changedin=&chfieldfrom=&chfieldto=Now&chfieldvalue=&cmdtype=doit&order=Bug+Number&field0-0-0=noop&type0-0-0=noop&value0-0-0=">"code-cleanup" bugs</a> filed in it. Taking one of these and fixing it is a good |
| way to get your feet wet in the LLVM code and discover how some of its components |
| work. |
| </p> |
| |
| </div> |
| |
| <!-- ======================================================================= --> |
| <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/manual/html_node/Porting.html">port</a> <a |
| href="http://www.gnu.org/software/libc/">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> |
| |
| <!-- ======================================================================= --> |
| <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> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="llvm_ir">Extend the LLVM intermediate representation</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <ol> |
| <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> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="target">Target backend improvements</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <ol> |
| <li>Find benchmarks either using our <a |
| href="http://llvm.cs.uiuc.edu/testresults/">test results</a> or on your own, |
| where LLVM code generators do not produce optimal code or simply where another |
| compiler produces better code. Try to minimize the test case that |
| demonstrates the issue. Then, either <a |
| href="http://llvm.cs.uiuc.edu/bugs/">submit a bug</a> with your testcase and |
| the code that LLVM produces vs. the code that it <em>should</em> produce, or |
| even better, see if you can improve the code generator and submit a |
| patch.</li> |
| </ol> |
| |
| </div> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="misc_imp">Miscellaneous Improvements</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <ol> |
| <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> |
| |
| <!-- *********************************************************************** --> |
| <div class="doc_section"> |
| <a name="new">Adding new capabilities to LLVM</a> |
| </div> |
| <!-- *********************************************************************** --> |
| |
| <div class="doc_text"> |
| |
| <p>Sometimes creating new things is more fun than improving existing things. |
| These projects tend to be more involved and perhaps require more work, but can |
| also be very rewarding.</p> |
| |
| </div> |
| |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="newfeaturebugs">Implementing new feature PRs</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <p>Many ideas for feature requests are stored in LLVM bugzilla. Just <a |
| href="http://llvm.cs.uiuc.edu/bugs/buglist.cgi?short_desc_type=allwordssubstr&short_desc=&long_desc_type=allwordssubstr&long_desc=&bug_file_loc_type=allwordssubstr&bug_file_loc=&status_whiteboard_type=allwordssubstr&status_whiteboard=&keywords_type=allwords&keywords=new-feature&bug_status=UNCONFIRMED&bug_status=NEW&bug_status=ASSIGNED&bug_status=REOPENED&emailassigned_to1=1&emailtype1=substring&email1=&emailassigned_to2=1&emailreporter2=1&emailcc2=1&emailtype2=substring&email2=&bugidtype=include&bug_id=&votes=&changedin=&chfieldfrom=&chfieldto=Now&chfieldvalue=&cmdtype=doit&namedcmd=All+PRs&newqueryname=&order=Bug+Number&field0-0-0=noop&type0-0-0=noop&value0-0-0=">search for bugs with a "new-feature" keyword</a>.</p> |
| |
| </div> |
| |
| <!-- ======================================================================= --> |
| <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 alias-analysis-based optimizations: |
| <ul> |
| <li>...</li> |
| </ul></li> |
| </ol> |
| |
| </div> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="profileguided">Profile-Guided Optimization</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <p>We now have a unified infrastructure for writing profile-guided |
| transformations, which will work either at offline-compile-time or in the JIT, |
| but we don't have many transformations. We would welcome new profile-guided |
| transformations as well as improvements to the current profiling system. |
| </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> |
| |
| <p>Improvements to the existing support:</p> |
| |
| <ol> |
| <li>The current block and edge profiling code that gets inserted is very simple |
| and inefficient. Through the use of control-dependence information, many fewer |
| counters could be inserted into the code. Also, if the execution count of a |
| loop is known to be a compile-time or runtime constant, all of the counters in |
| the loop could be avoided.</li> |
| |
| <li>You could implement one of the "static profiling" algorithms which analyze a |
| piece of code an make educated guesses about the relative execution frequencies |
| of various parts of the code.</li> |
| |
| <li>You could add path profiling support, or adapt the existing LLVM path |
| profiling code to work with the generic profiling interfaces.</li> |
| </ol> |
| |
| </div> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_subsection"> |
| <a name="xforms">New Transformations and Analyses</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <ol> |
| <li>Implement <a href="http://www.cs.purdue.edu/homes/vandrutj/">GVN-PRE</a>, a |
| powerful and simple Partial Redundancy Elimination algorithm for SSA form</li> |
| <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> |
| </ol> |
| |
| </div> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_section"> |
| <a name="x86be">X86 Back-end Improvements</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <ol> |
| <li>Implement a better instruction selector</li> |
| <li>Implement support for the "switch" instruction without requiring the |
| lower-switches pass.</li> |
| <li>Implement interprocedural register allocation. The CallGraphSCCPass can be |
| used to implement a bottom-up analysis that will determine the *actual* |
| registers clobbered by a function. Use the pass to fine tune register usage |
| in callers based on *actual* registers used by the callee.</li> |
| </ol> |
| |
| </div> |
| |
| <!-- ======================================================================= --> |
| <div class="doc_section"> |
| <a name="misc_new">Miscellaneous Additions</a> |
| </div> |
| |
| <div class="doc_text"> |
| |
| <ol> |
| <li>Port the <a href="http://www-sop.inria.fr/mimosa/fp/Bigloo/">Bigloo</A> |
| Scheme compiler, from Manuel Serrano at INRIA Sophia-Antipolis, to |
| output LLVM bytecode. It seems that it can already output .NET |
| bytecode, JVM bytecode, and C, so LLVM would ostensibly be another good |
| candidate.</li> |
| <li>Write a new frontend for C/C++ <b>in</b> C++, giving us the ability to |
| directly use LLVM C++ classes from within a compiler rather than use |
| C-based wrapper functions a la llvm-gcc. One possible starting point is the <a |
| href="http://www.parashift.com/c++-faq-lite/compiler-dependencies.html#faq-37.11">C++ |
| yacc grammar by Ed Willink</a>.</li> |
| <li>Write a new frontend for some other language (Java? OCaml? Forth?)</li> |
| <li>Write a new backend for a target (IA64? MIPS? MMIX?)</li> |
| <li>Write a disassembler for machine code that would use TableGen to output |
| <tt>MachineInstr</tt>s for transformations, optimizations, etc.</li> |
| <li>Random test vector generator: Use a C grammar to generate random C code; |
| run it through llvm-gcc, then run a random set of passes on it using opt. |
| Try to crash opt. When opt crashes, use bugpoint to reduce the test case and |
| mail the result to yourself. Repeat ad infinitum.</li> |
| <li>Design a simple, recognizable logo.</li> |
| <li>Improve the usefulness and utility of the Skeleton target backend: |
| <ul> |
| <li>Convert the non-functional Skeleton target to become an abstract machine |
| target (choose some simple instructions, a register set, etc). This will |
| become a much more useful example of a backend since it would be a simple |
| but <em>functional</em> backend. Examples of such architectures include MIX, |
| MMIX, <a |
| href="http://www.cs.cinvestav.mx/SC/prof_personal/adiaz/vhdl/DLX/">DLX</a>, |
| or come up with your own!</li> |
| <li>Use the new Skeleton backend in the Interpreter: compile LLVM to Skeleton |
| target, and then interpret that code instead of LLVM. Performance win would |
| be the primary goal, as the number of registers would be a small constant |
| instead of unbounded, for example.</li> |
| </ul></li> |
| </ol> |
| |
| </div> |
| |
| <!-- *********************************************************************** --> |
| |
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