llvm/docs/OpenProjects.html - llvm-project - Git at Google

 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
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 <html>
 <head>
   <title>Open LLVM Projects</title>
   <link rel="stylesheet" href="llvm.css" type="text/css">
 </head>
 <body>

 <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="#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>

 <!-- *********************************************************************** -->
 <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 our <a href="http://llvm.cs.uiuc.edu/bugs/">
 LLVM bug tracker</a>. Here is the current list:
 </p>

 <iframe src="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" frameborder="1" align="center" width="100%" height="400">
 </iframe>

 </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="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>

 <!-- ======================================================================= -->
 <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>

 <!-- ======================================================================= -->
 <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="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>

 <!-- *********************************************************************** -->
 <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 that 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="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>

 <!-- ======================================================================= -->
 <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 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>

 <!-- ======================================================================= -->
 <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>

 <!-- ======================================================================= -->
 <div class="doc_section">
   <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>
 <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>
 </ol>

 </div>

 <!-- *********************************************************************** -->

 <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>
   Last modified: $Date$
 </div>

 </body>
 </html>
	<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
	"http://www.w3.org/TR/html4/strict.dtd">
	<html>
	<head>
	<title>Open LLVM Projects</title>
	<link rel="stylesheet" href="llvm.css" type="text/css">
	</head>
	<body>

	<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="#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>

	<!-- *********************************************************************** -->
	<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 our <a href="http://llvm.cs.uiuc.edu/bugs/">
	LLVM bug tracker</a>. Here is the current list:
	</p>

	<iframe src="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" frameborder="1" align="center" width="100%" height="400">
	</iframe>

	</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="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>

	<!-- ======================================================================= -->
	<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>

	<!-- ======================================================================= -->
	<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="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>

	<!-- *********************************************************************** -->
	<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 that 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="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>

	<!-- ======================================================================= -->
	<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 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>

	<!-- ======================================================================= -->
	<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>

	<!-- ======================================================================= -->
	<div class="doc_section">
	<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>
	<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>
	</ol>

	</div>

	<!-- *********************************************************************** -->

	<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>
	Last modified: $Date$
	</div>

	</body>
	</html>