2003-05-22 06:21:07 +08:00
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<html><head><title>How to submit an LLVM bug report</title></head>
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<body bgcolor=white>
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<table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
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<tr><td> <font size=+3 color="#EEEEFF" face="Georgia,Palatino,Times,Roman"><b>How to submit an LLVM bug report</b></font></td>
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</tr></table>
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<table border=0 width=100%>
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<tr><td valign=top>
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<p><font size=+1>
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<ol>
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<li><a href="#introduction">Introduction - Got bugs?</a>
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<li><a href="#crashers">Crashing Bugs</a>
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<ul>
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<li><a href="#front-end">Front-end bugs</a>
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<li><a href="#gccas">GCCAS bugs</a>
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<li><a href="#gccld">GCCLD bugs</a>
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<li><a href="#passes">Bugs in LLVM passes</a>
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</ul>
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<li><a href="#miscompilations">Miscompilations</a>
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<p><b>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a></b><p>
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</ol><p></font>
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</td><td valign=top align=right>
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<img src="Debugging.gif" width=444 height=314>
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</td></tr>
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</table>
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<!-- *********************************************************************** -->
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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="introduction">Introduction - Got bugs?
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</b></font></td></tr></table><ul>
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<!-- *********************************************************************** -->
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If you're working with LLVM and run into a bug, we definitely want to know about
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it. This document describes what you can do to increase the odds of getting it
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fixed quickly.<p>
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Basically you have to do two things at a minimum. First, decide whether the bug
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<a href="#crashers">crashes the compiler</a> (or an LLVM pass), or if the
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compiler is <a href="#miscompilations">miscompiling</a> the program. Based on
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what type of bug it is, follow the instructions in the linked section to narrow
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down the bug so that the person who fixes it will be able to find the problem
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more easily.<p>
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Once you have a reduced test-case, email information about the bug to: <a
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href="mailto:llvmbugs@cs.uiuc.edu">llvmbugs@cs.uiuc.edu</a>. This should
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include all of the information necessary to reproduce the problem, including
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where you got the LLVM tree from (if you're not working out of CVS).<p>
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Thanks for helping us make LLVM better!<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="crashers">Crashing Bugs
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</b></font></td></tr></table><ul>
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<!-- *********************************************************************** -->
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More often than not, bugs in the compiler cause it to crash - often due to an
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assertion failure of some sort. If you are running <tt><b>opt</b></tt> or
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<tt><b>analyze</b></tt> directly, and something crashes, jump to the section on
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<a href="#passes">bugs in LLVM passes</a>. Otherwise, the most important
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piece of the puzzle is to figure out if it is the GCC-based front-end that is
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buggy or if it's one of the LLVM tools that has problems.<p>
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To figure out which program is crashing (the front-end, <tt><b>gccas</b></tt>,
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or <tt><b>gccld</b></tt>), run the <tt><b>llvm-gcc</b></tt> command line as you
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were when the crash occurred, but add a <tt>-v</tt> option to the command line.
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The compiler will print out a bunch of stuff, and should end with telling you
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that one of <tt><b>cc1</b></tt>, <tt><b>gccas</b></tt>, or <tt><b>gccld</b></tt>
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crashed.<p>
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<ul>
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<li>If <tt><b>cc1</b></tt> crashed, you found a problem with the front-end.
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Jump ahead to the section on <a href="#front-end">front-end bugs</a>.
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<li>If <tt><b>gccas</b></tt> crashed, you found a bug in <a href="#gccas">one of
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the passes in <tt><b>gccas</b></tt></a>.
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<li>If <tt><b>gccld</b></tt> crashed, you found a bug in <a href="#gccld">one
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of the passes in <tt><b>gccld</b></tt></a>.
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<li>Otherwise, something really weird happened. Email the list with what you
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have at this point.
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</ul><p>
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<!-- ======================================================================= -->
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</ul><table width="100%" 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" face="Georgia,Palatino"><b>
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<a name="front-end">Front-end bugs
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</b></font></td></tr></table><ul>
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If the problem is in the front-end, pretty much the only thing you can do is
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preprocess the input (compile with the <tt>-E</tt> option) and send us the
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results. There is no good way to reduce source-level test-cases that I know
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of... if you do know, send me information and we can extend this section. :)<p>
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<!-- ======================================================================= -->
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</ul><table width="100%" 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" face="Georgia,Palatino"><b>
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<a name="gccas">GCCAS bugs
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</b></font></td></tr></table><ul>
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If you find that a bug crashes in the <tt><b>gccas</b></tt> stage of
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compilation, compile your test-case to a <tt>.s</tt> file with the <tt>-S</tt>
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option to <tt><b>llvm-gcc</b></tt>. Then run:<p>
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<pre>
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<b>gccas</b> -debug-pass=Arguments < /dev/null -o - > /dev/null
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</pre><p>
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... which will print a list of arguments, indicating the list of passes that
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<tt><b>gccas</b></tt> runs. Once you have the input file and the list of
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passes, go to the section on <a href="#passes">debugging bugs in LLVM
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passes</a>.<p>
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<!-- ======================================================================= -->
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</ul><table width="100%" 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" face="Georgia,Palatino"><b>
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<a name="gccld">GCCLD bugs
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</b></font></td></tr></table><ul>
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If you find that a bug crashes in the <tt><b>gccld</b></tt> stage of
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compilation, gather all of the <tt>.o</tt> bytecode files and libraries that are
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being linked together (the "<tt><b>llvm-gcc</b> -v</tt>" output should include
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the full list of objects linked). Then run:<p>
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<pre>
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2003-05-23 22:49:32 +08:00
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<b>as</b> < /dev/null > null.bc
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<b>gccld</b> -debug-pass=Arguments null.bc
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2003-05-22 06:21:07 +08:00
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</pre><p>
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... which will print a list of arguments, indicating the list of passes that
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<tt><b>gccld</b></tt> runs. Once you have the input files and the list of
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passes, go to the section on <a href="#passes">debugging bugs in LLVM
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passes</a>.<p>
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<!-- ======================================================================= -->
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</ul><table width="100%" 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" face="Georgia,Palatino"><b>
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<a name="passes">Bugs in LLVM passes
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</b></font></td></tr></table><ul>
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At this point, you should have some number of LLVM assembly files or bytecode
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files and a list of passes which crash when run on the specified input. In
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order to reduce the list of passes (which is probably large) and the input to
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something tractable, use the <tt><b>bugpoint</b></tt> tool as follows:<p>
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<pre>
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<b>bugpoint</b> <input files> <list of passes>
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</pre><p>
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<tt><b>bugpoint</b></tt> will print a bunch of output as it reduces the
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test-case, but it should eventually print something like this:<p>
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<pre>
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...
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Emitted bytecode to 'bugpoint-reduced-simplified.bc'
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*** You can reproduce the problem with: opt bugpoint-reduced-simplified.bc -licm
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</pre><p>
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Once you complete this, please send the LLVM bytecode file and the command line
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to reproduce the problem to the llvmbugs mailing list.<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="miscompilations">Miscompilations
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</b></font></td></tr></table><ul>
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<!-- *********************************************************************** -->
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Fortunately we haven't had to many miscompilations. Because of this, this
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section is a TODO. Basically, use bugpoint to track down the problem.<p>
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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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2003-05-23 22:49:32 +08:00
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Last modified: Fri May 23 09:48:53 CDT 2003
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2003-05-22 06:21:07 +08:00
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<!-- hhmts end -->
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</font></body></html>
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