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286 lines
12 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html><head><title>Open LLVM Projects</title></head>
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<body bgcolor=white>
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<center><h1><font size=7>Open LLVM Projects</font></h1></center>
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<ul>
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<li><a href="#what">What is this?</a>
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<li><a href="#improving">Improving the current system</a>
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<ol>
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<li><a href="#glibc">Port glibc to LLVM</a>
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<li><a href="#NightlyTest">Improving the Nightly Tester</a>
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<li><a href="#programs">Compile programs with the LLVM Compiler</a>
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<li><a href="#llvm_ir">Extend the LLVM intermediate representation</a>
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<li><a href="#misc_imp">Miscellaneous Improvements</a>
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</ol>
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<li><a href="#new">Adding new capabilities to LLVM</a>
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<ol>
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<li><a href="#pointeranalysis">Pointer and Alias Analysis</a>
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<li><a href="#profileguided">Profile Guided Optimization</a>
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<li><a href="#xforms">New Transformations and Analyses</a>
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<li><a href="#x86be">X86 Back-end Improvements</a>
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<li><a href="#misc_new">Miscellaneous Additions</a>
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</ol>
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</ul>
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<br><br>
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<table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
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<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
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<a name="what">What is this?
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</b></font></td></tr></table><ul>
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<!-- *********************************************************************** -->
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This document is meant to be a sort of "big TODO list" for LLVM. Each project
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in this document is something that would be useful for LLVM to have, and would
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also be a great way to get familiar with the system. Some of these projects are
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small and self-contained, which may be implemented in a couple of days, others
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are larger. Several of these projects may lead to interesting research projects
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in their own right. In any case, we welcome all contributions.<p>
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If you are thinking about tackling one of these projects, please send a mail to
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the <a href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM
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Developer's</a> mailing list, so that we know the project is being worked on.
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Additionally this is a good way to get more information about a specific project
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or to suggest other projects to add to this page.<p>
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<!-- *********************************************************************** -->
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</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
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<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
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<a name="improving">Improving the current system
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</b></font></td></tr></table><ul>
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<!-- *********************************************************************** -->
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Improvements to the current infrastructure are always very welcome and tend to
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be fairly straight-forward to implement. Here are some of the key areas that
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can use improvement...<p>
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<!-- ======================================================================= -->
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</ul><table width="50%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
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<tr><td> </td><td width=100%>
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<font color="#EEEEFF" size=+1 face="Georgia,Palatino"><b>
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<a name="glibc">Port glibc to LLVM
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</b></font></td></tr></table><ul>
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It would be very useful to <a
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href="http://www.gnu.org/software/libc/porting.html">port</a> <a
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href="http://www.gnu.org/software/glibc/">glibc</a> to LLVM. This would allow a
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variety of interprocedural algorithms to be much more effective in the face of
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library calls. The most important pieces to port are things like the string
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library and the <tt>stdio</tt> related functions... low-level system calls like
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'<tt>read</tt>' should stay unimplemented in LLVM.<p>
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<!-- ======================================================================= -->
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</ul><table width="50%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
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<tr><td> </td><td width=100%>
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<font color="#EEEEFF" size=+1 face="Georgia,Palatino"><b>
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<a name="NightlyTest">Improving the Nightly Tester
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</b></font></td></tr></table><ul>
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The <a href="/testresults/">Nightly Tester</a> is a simple perl script (located
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in utils/NightlyTest.pl) which runs every night to generate a daily report. It
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could use the following improvements:<p>
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<ol>
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<li>Olden timings - Time the compilation and execution times for the Olden
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benchmark suite, keeping track of these values over time.
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<li>Graphs - It would be great to have gnuplot graphs to keep track of how the
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tree is changing over time. We already gather a several statistics, it
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just necessary to add the script-fu to gnuplotize it.
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<li>Regression tests - We should run the regression tests in addition to the
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program tests...
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</ol><p>
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<!-- ======================================================================= -->
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</ul><table width="50%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
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<tr><td> </td><td width=100%>
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<font color="#EEEEFF" size=+1 face="Georgia,Palatino"><b>
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<a name="programs">Compile programs with the LLVM Compiler
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</b></font></td></tr></table><ul>
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We are always looking for new testcases and benchmarks for use with LLVM. In
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particular, it is useful to try compiling your favorite C source code with LLVM.
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If it doesn't compile, try to figure out why or report it to the <a
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href="http://mail.cs.uiuc.edu/pipermail/llvmbugs/">llvm-bugs</a> list. If you
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get the program to compile, it would be extremely useful to convert the build
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system to be compatible with the LLVM Programs testsuite so that we can check it
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into CVS and the automated tester can use it to track progress of the
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compiler.<p>
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When testing a code, try running it with a variety of optimizations, and with
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all the back-ends: CBE, llc, and lli.<p>
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<!-- ======================================================================= -->
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</ul><table width="50%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
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<tr><td> </td><td width=100%>
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<font color="#EEEEFF" size=+1 face="Georgia,Palatino"><b>
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<a name="llvm_ir">Extend the LLVM intermediate representation
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</b></font></td></tr></table><ul>
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<ol>
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<li>Transform <tt>setjmp</tt> and <tt>longjmp</tt> calls to use the LLVM
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<tt>invoke</tt> mechanism.
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<li>Add support for a volatile attribute on loads and stores
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<li>Add a new conditional move instruction: <tt>X = select bool Cond, Y, Z</tt>
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<li>Add support for platform independent prefetch support. The GCC <a
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href="http://gcc.gnu.org/projects/prefetch.html">prefetch project</a> page
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has a good survey of the prefetching capabilities of a variety of modern
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processors.
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</ol>
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<!-- ======================================================================= -->
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</ul><table width="50%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
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<tr><td> </td><td width=100%>
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<font color="#EEEEFF" size=+1 face="Georgia,Palatino"><b>
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<a name="misc_imp">Miscellaneous Improvements
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</b></font></td></tr></table><ul>
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<ol>
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<li>Someone needs to look into getting the <tt>ranlib</tt> tool to index LLVM
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bytecode files, so that linking in .a files is not hideously slow. They
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would also then have to implement the reader for this index in
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<tt>gccld</tt>.<br>
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<li>Improve the efficiency of the bytecode loader/writer, allow streaming lazy
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loading of functions from the bytecode (for use by the JIT, for example)<br>
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<li>Rework the PassManager to be more flexible
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<li>Some transformations and analyses only work on reducible flow graphs. It
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would be nice to have a transformation which could be "required" by these passes
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which makes irreducible graphs reducible. This can easily be accomplished
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through code duplication. See <a
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href="http://citeseer.nj.nec.com/janssen97making.html">Making Graphs Reducible
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with Controlled Node Splitting</a> and perhaps <a
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href="http://doi.acm.org/10.1145/262004.262005">Nesting of Reducible and
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Irreducible Loops</a>.
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</ol>
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<!-- *********************************************************************** -->
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</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
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<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
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<a name="new">Adding new capabilities to LLVM
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</b></font></td></tr></table><ul>
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<!-- *********************************************************************** -->
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Sometimes creating new things is more fun that improving existing things. These
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projects tend to be more involved and perhaps require more work, but can also be
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very rewarding.<p>
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<!-- ======================================================================= -->
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</ul><table width="50%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
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<tr><td> </td><td width=100%>
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<font color="#EEEEFF" size=+1 face="Georgia,Palatino"><b>
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<a name="pointeranalysis">Pointer and Alias Analysis
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</b></font></td></tr></table><ul>
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We have a <a href="AliasAnalysis.html">strong base for development</a> of both
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pointer analysis based optimizations as well as pointer analyses themselves. It
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seems natural to want to take advantage of this...<p>
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<ol>
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<li>Implement a flow-sensitive context-sensitive alias analysis algorithm<br>
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- Pick one of the somewhat efficient algorithms, but strive for maximum
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precision
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<li>Implement a flow-sensitive context-insensitive alias analysis algorithm<br>
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- Just an efficient local algorithm perhaps?
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<li>Implement an interface to update analyses in response to common code motion
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transformations
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<li>Implement alias analysis based optimizations:
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<ul>
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<li>Dead store elimination
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</ul>
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</ol>
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<!-- ======================================================================= -->
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</ul><table width="50%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
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<tr><td> </td><td width=100%>
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<font color="#EEEEFF" size=+1 face="Georgia,Palatino"><b>
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<a name="profileguided">Profile Guided Optimization
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</b></font></td></tr></table><ul>
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We are getting to the point where we really need a unified infrastructure for
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profile guided optimizations. It would be wonderful to be able to write profile
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guided transformations which can be performed either at static compile time
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(compile time or offline optimization time) or at runtime in a JIT type setup.
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The LLVM transformation itself shouldn't need to know how it is being used.<p>
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Ideas for profile guided transformations:<p>
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<ol>
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<li>Superblock formation (with many optimizations)
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<li>Loop unrolling/peeling
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<li>Profile directed inlining
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<li>Code layout
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<li>...
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</ol><p>
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<!-- ======================================================================= -->
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</ul><table width="50%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
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<tr><td> </td><td width=100%>
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<font color="#EEEEFF" size=+1 face="Georgia,Palatino"><b>
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<a name="xforms">New Transformations and Analyses
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</b></font></td></tr></table><ul>
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<ol>
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<li>Implement a Dependence Analysis Infrastructure<br>
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- Design some way to represent and query dep analysis
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<li>Implement a faster Dominator Set Construction Algorithm<br>
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- A linear time or nearly so algorithm
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<li>Implement a strength reduction pass
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<li>Value range propagation pass
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<li>Implement a tail recursion elimination pass
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<li>Implement an unswitching pass
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<li>Write a loop unroller, with a simple heuristic for when to unroll
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</ol>
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<!-- ======================================================================= -->
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</ul><table width="50%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
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<tr><td> </td><td width=100%>
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<font color="#EEEEFF" size=+1 face="Georgia,Palatino"><b>
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<a name="x86be">X86 Back-end Improvements
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</b></font></td></tr></table><ul>
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<ol>
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<li>Implement a global register allocator
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<li>Implement a better instruction selector
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<li>Implement support for the "switch" instruction without requiring the
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lower-switches pass.
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</ol>
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<!-- ======================================================================= -->
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</ul><table width="50%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
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<tr><td> </td><td width=100%>
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<font color="#EEEEFF" size=+1 face="Georgia,Palatino"><b>
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<a name="misc_new">Miscellaneous Additions
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</b></font></td></tr></table><ul>
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<ol>
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<li>Write a new frontend for some language (Java? OCaml? Forth?)
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<li>Write a new backend for a target (IA64? MIPS? MMIX?)
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</ol>
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<!-- *********************************************************************** -->
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</ul>
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<!-- *********************************************************************** -->
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<hr><font size-1>
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<address><a href="mailto:sabre@nondot.org">Chris Lattner</a></address>
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<!-- Created: Tue Aug 6 15:00:33 CDT 2002 -->
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<!-- hhmts start -->
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Last modified: Wed Aug 6 10:40:05 CDT 2003
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<!-- hhmts end -->
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</font></body></html>
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