[llvm-commits] CVS: llvm/www/docs/HowToSubmitABug.html
Chris Lattner
lattner at cs.uiuc.edu
Wed May 21 17:22:00 PDT 2003
Changes in directory llvm/www/docs:
HowToSubmitABug.html added (r1.1)
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+ <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
+ <html><head><title>How to submit an LLVM bug report</title></head>
+
+ <body bgcolor=white>
+
+ <table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
+ <tr><td> <font size=+3 color="#EEEEFF" face="Georgia,Palatino,Times,Roman"><b>How to submit an LLVM bug report</b></font></td>
+ </tr></table>
+
+ <table border=0 width=100%>
+ <tr><td valign=top>
+ <p><font size=+1>
+ <ol>
+ <li><a href="#introduction">Introduction - Got bugs?</a>
+ <li><a href="#crashers">Crashing Bugs</a>
+ <ul>
+ <li><a href="#front-end">Front-end bugs</a>
+ <li><a href="#gccas">GCCAS bugs</a>
+ <li><a href="#gccld">GCCLD bugs</a>
+ <li><a href="#passes">Bugs in LLVM passes</a>
+ </ul>
+ <li><a href="#miscompilations">Miscompilations</a>
+
+ <p><b>Written by <a href="mailto:sabre at nondot.org">Chris Lattner</a></b><p>
+ </ol><p></font>
+ </td><td valign=top align=right>
+ <img src="Debugging.gif" width=444 height=314>
+ </td></tr>
+ </table>
+
+
+ <!-- *********************************************************************** -->
+ <table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
+ <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
+ <a name="introduction">Introduction - Got bugs?
+ </b></font></td></tr></table><ul>
+ <!-- *********************************************************************** -->
+
+ If you're working with LLVM and run into a bug, we definitely want to know about
+ it. This document describes what you can do to increase the odds of getting it
+ fixed quickly.<p>
+
+ Basically you have to do two things at a minimum. First, decide whether the bug
+ <a href="#crashers">crashes the compiler</a> (or an LLVM pass), or if the
+ compiler is <a href="#miscompilations">miscompiling</a> the program. Based on
+ what type of bug it is, follow the instructions in the linked section to narrow
+ down the bug so that the person who fixes it will be able to find the problem
+ more easily.<p>
+
+ Once you have a reduced test-case, email information about the bug to: <a
+ href="mailto:llvmbugs at cs.uiuc.edu">llvmbugs at cs.uiuc.edu</a>. This should
+ include all of the information necessary to reproduce the problem, including
+ where you got the LLVM tree from (if you're not working out of CVS).<p>
+
+ Thanks for helping us make LLVM better!<p>
+
+
+ <!-- *********************************************************************** -->
+ </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
+ <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
+ <a name="crashers">Crashing Bugs
+ </b></font></td></tr></table><ul>
+ <!-- *********************************************************************** -->
+
+ More often than not, bugs in the compiler cause it to crash - often due to an
+ assertion failure of some sort. If you are running <tt><b>opt</b></tt> or
+ <tt><b>analyze</b></tt> directly, and something crashes, jump to the section on
+ <a href="#passes">bugs in LLVM passes</a>. Otherwise, the most important
+ piece of the puzzle is to figure out if it is the GCC-based front-end that is
+ buggy or if it's one of the LLVM tools that has problems.<p>
+
+ To figure out which program is crashing (the front-end, <tt><b>gccas</b></tt>,
+ or <tt><b>gccld</b></tt>), run the <tt><b>llvm-gcc</b></tt> command line as you
+ were when the crash occurred, but add a <tt>-v</tt> option to the command line.
+ The compiler will print out a bunch of stuff, and should end with telling you
+ that one of <tt><b>cc1</b></tt>, <tt><b>gccas</b></tt>, or <tt><b>gccld</b></tt>
+ crashed.<p>
+
+ <ul>
+ <li>If <tt><b>cc1</b></tt> crashed, you found a problem with the front-end.
+ Jump ahead to the section on <a href="#front-end">front-end bugs</a>.
+ <li>If <tt><b>gccas</b></tt> crashed, you found a bug in <a href="#gccas">one of
+ the passes in <tt><b>gccas</b></tt></a>.
+ <li>If <tt><b>gccld</b></tt> crashed, you found a bug in <a href="#gccld">one
+ of the passes in <tt><b>gccld</b></tt></a>.
+ <li>Otherwise, something really weird happened. Email the list with what you
+ have at this point.
+ </ul><p>
+
+
+ <!-- ======================================================================= -->
+ </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
+ <tr><td> </td><td width="100%">
+ <font color="#EEEEFF" face="Georgia,Palatino"><b>
+ <a name="front-end">Front-end bugs
+ </b></font></td></tr></table><ul>
+
+ If the problem is in the front-end, pretty much the only thing you can do is
+ preprocess the input (compile with the <tt>-E</tt> option) and send us the
+ results. There is no good way to reduce source-level test-cases that I know
+ of... if you do know, send me information and we can extend this section. :)<p>
+
+
+ <!-- ======================================================================= -->
+ </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
+ <tr><td> </td><td width="100%">
+ <font color="#EEEEFF" face="Georgia,Palatino"><b>
+ <a name="gccas">GCCAS bugs
+ </b></font></td></tr></table><ul>
+
+ If you find that a bug crashes in the <tt><b>gccas</b></tt> stage of
+ compilation, compile your test-case to a <tt>.s</tt> file with the <tt>-S</tt>
+ option to <tt><b>llvm-gcc</b></tt>. Then run:<p>
+
+ <pre>
+ <b>gccas</b> -debug-pass=Arguments < /dev/null -o - > /dev/null
+ </pre><p>
+
+ ... which will print a list of arguments, indicating the list of passes that
+ <tt><b>gccas</b></tt> runs. Once you have the input file and the list of
+ passes, go to the section on <a href="#passes">debugging bugs in LLVM
+ passes</a>.<p>
+
+
+ <!-- ======================================================================= -->
+ </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
+ <tr><td> </td><td width="100%">
+ <font color="#EEEEFF" face="Georgia,Palatino"><b>
+ <a name="gccld">GCCLD bugs
+ </b></font></td></tr></table><ul>
+
+ If you find that a bug crashes in the <tt><b>gccld</b></tt> stage of
+ compilation, gather all of the <tt>.o</tt> bytecode files and libraries that are
+ being linked together (the "<tt><b>llvm-gcc</b> -v</tt>" output should include
+ the full list of objects linked). Then run:<p>
+
+ <pre>
+ <b>gccld</b> -debug-pass=Arguments < /dev/null -o - > /dev/null
+ </pre><p>
+
+ ... which will print a list of arguments, indicating the list of passes that
+ <tt><b>gccld</b></tt> runs. Once you have the input files and the list of
+ passes, go to the section on <a href="#passes">debugging bugs in LLVM
+ passes</a>.<p>
+
+ <!-- ======================================================================= -->
+ </ul><table width="100%" bgcolor="#441188" border=0 cellpadding=4 cellspacing=0>
+ <tr><td> </td><td width="100%">
+ <font color="#EEEEFF" face="Georgia,Palatino"><b>
+ <a name="passes">Bugs in LLVM passes
+ </b></font></td></tr></table><ul>
+
+ At this point, you should have some number of LLVM assembly files or bytecode
+ files and a list of passes which crash when run on the specified input. In
+ order to reduce the list of passes (which is probably large) and the input to
+ something tractable, use the <tt><b>bugpoint</b></tt> tool as follows:<p>
+
+ <pre>
+ <b>bugpoint</b> <input files> <list of passes>
+ </pre><p>
+
+ <tt><b>bugpoint</b></tt> will print a bunch of output as it reduces the
+ test-case, but it should eventually print something like this:<p>
+
+ <pre>
+ ...
+ Emitted bytecode to 'bugpoint-reduced-simplified.bc'
+
+ *** You can reproduce the problem with: opt bugpoint-reduced-simplified.bc -licm
+ </pre><p>
+
+ Once you complete this, please send the LLVM bytecode file and the command line
+ to reproduce the problem to the llvmbugs mailing list.<p>
+
+
+ <!-- *********************************************************************** -->
+ </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0>
+ <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b>
+ <a name="miscompilations">Miscompilations
+ </b></font></td></tr></table><ul>
+ <!-- *********************************************************************** -->
+
+ Fortunately we haven't had to many miscompilations. Because of this, this
+ section is a TODO. Basically, use bugpoint to track down the problem.<p>
+
+
+ <!-- *********************************************************************** -->
+ </ul>
+ <!-- *********************************************************************** -->
+
+ <hr><font size-1>
+ <address><a href="mailto:sabre at nondot.org">Chris Lattner</a></address>
+ <!-- Created: Tue Aug 6 15:00:33 CDT 2002 -->
+ <!-- hhmts start -->
+ Last modified: Wed May 21 17:20:13 CDT 2003
+ <!-- hhmts end -->
+ </font></body></html>
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