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Sean Silva
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
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"http://www.w3.org/TR/html4/strict.dtd">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<title>How to submit an LLVM bug report</title>
|
||||
<link rel="stylesheet" href="_static/llvm.css" type="text/css">
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</head>
|
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<body>
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|
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<h1>
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How to submit an LLVM bug report
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</h1>
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|
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<table class="layout" style="width: 90%" >
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<tr class="layout">
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<td class="left">
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<ol>
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<li><a href="#introduction">Introduction - Got bugs?</a></li>
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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="#ct_optimizer">Compile-time optimization bugs</a>
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<li><a href="#ct_codegen">Code generator bugs</a>
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</ul></li>
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<li><a href="#miscompilations">Miscompilations</a></li>
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<li><a href="#codegen">Incorrect code generation (JIT and LLC)</a></li>
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</ol>
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||||
<div class="doc_author">
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<p>Written by <a href="mailto:sabre@nondot.org">Chris Lattner</a> and
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<a href="http://misha.brukman.net">Misha Brukman</a></p>
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</div>
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||||
</td>
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||||
</tr>
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||||
</table>
|
||||
|
||||
<!-- *********************************************************************** -->
|
||||
<h2>
|
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<a name="introduction">Introduction - Got bugs?</a>
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||||
</h2>
|
||||
<!-- *********************************************************************** -->
|
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|
||||
<div>
|
||||
|
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<p>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>
|
||||
|
||||
<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 (i.e., the
|
||||
compiler successfully produces an executable, but it doesn't run right). 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>
|
||||
|
||||
<p>Once you have a reduced test-case, go to <a
|
||||
href="http://llvm.org/bugs/enter_bug.cgi">the LLVM Bug Tracking
|
||||
System</a> and fill out the form with the necessary details (note that you don't
|
||||
need to pick a category, just use the "new-bugs" category if you're not sure).
|
||||
The bug description should contain the following
|
||||
information:</p>
|
||||
|
||||
<ul>
|
||||
<li>All information necessary to reproduce the problem.</li>
|
||||
<li>The reduced test-case that triggers the bug.</li>
|
||||
<li>The location where you obtained LLVM (if not from our Subversion
|
||||
repository).</li>
|
||||
</ul>
|
||||
|
||||
<p>Thanks for helping us make LLVM better!</p>
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||||
|
||||
</div>
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||||
|
||||
<!-- *********************************************************************** -->
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||||
<h2>
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<a name="crashers">Crashing Bugs</a>
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</h2>
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||||
<!-- *********************************************************************** -->
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|
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<div>
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|
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<p>More often than not, bugs in the compiler cause it to crash—often due
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to an assertion failure of some sort. The most important
|
||||
piece of the puzzle is to figure out if it is crashing in the GCC front-end
|
||||
or if it is one of the LLVM libraries (e.g. the optimizer or code generator)
|
||||
that has problems.</p>
|
||||
|
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<p>To figure out which component is crashing (the front-end,
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optimizer or code generator), run the
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<tt><b>llvm-gcc</b></tt> command line as you were when the crash occurred, but
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with the following extra command line options:</p>
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|
||||
<ul>
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<li><tt><b>-O0 -emit-llvm</b></tt>: If <tt>llvm-gcc</tt> still crashes when
|
||||
passed these options (which disable the optimizer and code generator), then
|
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the crash is in the front-end. Jump ahead to the section on <a
|
||||
href="#front-end">front-end bugs</a>.</li>
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|
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<li><tt><b>-emit-llvm</b></tt>: If <tt>llvm-gcc</tt> crashes with this option
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(which disables the code generator), you found an optimizer bug. Jump ahead
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to <a href="#ct_optimizer"> compile-time optimization bugs</a>.</li>
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|
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<li>Otherwise, you have a code generator crash. Jump ahead to <a
|
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href="#ct_codegen">code generator bugs</a>.</li>
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|
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</ul>
|
||||
|
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<!-- ======================================================================= -->
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<h3>
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<a name="front-end">Front-end bugs</a>
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</h3>
|
||||
|
||||
<div>
|
||||
|
||||
<p>If the problem is in the front-end, you should re-run the same
|
||||
<tt>llvm-gcc</tt> command that resulted in the crash, but add the
|
||||
<tt>-save-temps</tt> option. The compiler will crash again, but it will leave
|
||||
behind a <tt><i>foo</i>.i</tt> file (containing preprocessed C source code) and
|
||||
possibly <tt><i>foo</i>.s</tt> for each
|
||||
compiled <tt><i>foo</i>.c</tt> file. Send us the <tt><i>foo</i>.i</tt> file,
|
||||
along with the options you passed to llvm-gcc, and a brief description of the
|
||||
error it caused.</p>
|
||||
|
||||
<p>The <a href="http://delta.tigris.org/">delta</a> tool helps to reduce the
|
||||
preprocessed file down to the smallest amount of code that still replicates the
|
||||
problem. You're encouraged to use delta to reduce the code to make the
|
||||
developers' lives easier. <a
|
||||
href="http://gcc.gnu.org/wiki/A_guide_to_testcase_reduction">This website</a>
|
||||
has instructions on the best way to use delta.</p>
|
||||
|
||||
</div>
|
||||
|
||||
<!-- ======================================================================= -->
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<h3>
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<a name="ct_optimizer">Compile-time optimization bugs</a>
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</h3>
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|
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<div>
|
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|
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<p>If you find that a bug crashes in the optimizer, compile your test-case to a
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<tt>.bc</tt> file by passing "<tt><b>-emit-llvm -O0 -c -o foo.bc</b></tt>".
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Then run:</p>
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|
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<div class="doc_code">
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<p><tt><b>opt</b> -std-compile-opts -debug-pass=Arguments foo.bc
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-disable-output</tt></p>
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</div>
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|
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<p>This command should do two things: it should print out a list of passes, and
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then it should crash in the same way as llvm-gcc. If it doesn't crash, please
|
||||
follow the instructions for a <a href="#front-end">front-end bug</a>.</p>
|
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|
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<p>If this does crash, then you should be able to debug this with the following
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bugpoint command:</p>
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<div class="doc_code">
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<p><tt><b>bugpoint</b> foo.bc <list of passes printed by
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<b>opt</b>></tt></p>
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</div>
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|
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<p>Please run this, then file a bug with the instructions and reduced .bc files
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that bugpoint emits. If something goes wrong with bugpoint, please submit the
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||||
"foo.bc" file and the list of passes printed by <b>opt</b>.</p>
|
||||
|
||||
</div>
|
||||
|
||||
<!-- ======================================================================= -->
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<h3>
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<a name="ct_codegen">Code generator bugs</a>
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||||
</h3>
|
||||
|
||||
<div>
|
||||
|
||||
<p>If you find a bug that crashes llvm-gcc in the code generator, compile your
|
||||
source file to a .bc file by passing "<tt><b>-emit-llvm -c -o foo.bc</b></tt>"
|
||||
to llvm-gcc (in addition to the options you already pass). Once your have
|
||||
foo.bc, one of the following commands should fail:</p>
|
||||
|
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<ol>
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<li><tt><b>llc</b> foo.bc</tt></li>
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||||
<li><tt><b>llc</b> foo.bc -relocation-model=pic</tt></li>
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<li><tt><b>llc</b> foo.bc -relocation-model=static</tt></li>
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||||
</ol>
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|
||||
<p>If none of these crash, please follow the instructions for a
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||||
<a href="#front-end">front-end bug</a>. If one of these do crash, you should
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||||
be able to reduce this with one of the following bugpoint command lines (use
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||||
the one corresponding to the command above that failed):</p>
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||||
|
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<ol>
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<li><tt><b>bugpoint</b> -run-llc foo.bc</tt></li>
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<li><tt><b>bugpoint</b> -run-llc foo.bc --tool-args
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-relocation-model=pic</tt></li>
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<li><tt><b>bugpoint</b> -run-llc foo.bc --tool-args
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-relocation-model=static</tt></li>
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||||
</ol>
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||||
|
||||
<p>Please run this, then file a bug with the instructions and reduced .bc file
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that bugpoint emits. If something goes wrong with bugpoint, please submit the
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||||
"foo.bc" file and the option that llc crashes with.</p>
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||||
</div>
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||||
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||||
</div>
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||||
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<!-- *********************************************************************** -->
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<h2>
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<a name="miscompilations">Miscompilations</a>
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||||
</h2>
|
||||
<!-- *********************************************************************** -->
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<div>
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<p>If llvm-gcc successfully produces an executable, but that executable doesn't
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run right, this is either a bug in the code or a bug in the
|
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compiler. The first thing to check is to make sure it is not using undefined
|
||||
behavior (e.g. reading a variable before it is defined). In particular, check
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||||
to see if the program <a href="http://valgrind.org/">valgrind</a>s clean,
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||||
passes purify, or some other memory checker tool. Many of the "LLVM bugs" that
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we have chased down ended up being bugs in the program being compiled, not
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LLVM.</p>
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<p>Once you determine that the program itself is not buggy, you should choose
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which code generator you wish to compile the program with (e.g. LLC or the JIT)
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and optionally a series of LLVM passes to run. For example:</p>
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|
||||
<div class="doc_code">
|
||||
<p><tt>
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<b>bugpoint</b> -run-llc [... optzn passes ...] file-to-test.bc --args -- [program arguments]</tt></p>
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||||
</div>
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||||
|
||||
<p><tt>bugpoint</tt> will try to narrow down your list of passes to the one pass
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||||
that causes an error, and simplify the bitcode file as much as it can to assist
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you. It will print a message letting you know how to reproduce the resulting
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||||
error.</p>
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||||
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||||
</div>
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||||
|
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<!-- *********************************************************************** -->
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<h2>
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||||
<a name="codegen">Incorrect code generation</a>
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||||
</h2>
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||||
<!-- *********************************************************************** -->
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|
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<div>
|
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<p>Similarly to debugging incorrect compilation by mis-behaving passes, you can
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debug incorrect code generation by either LLC or the JIT, using
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<tt>bugpoint</tt>. The process <tt>bugpoint</tt> follows in this case is to try
|
||||
to narrow the code down to a function that is miscompiled by one or the other
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||||
method, but since for correctness, the entire program must be run,
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||||
<tt>bugpoint</tt> will compile the code it deems to not be affected with the C
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Backend, and then link in the shared object it generates.</p>
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<p>To debug the JIT:</p>
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<div class="doc_code">
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<pre>
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bugpoint -run-jit -output=[correct output file] [bitcode file] \
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--tool-args -- [arguments to pass to lli] \
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--args -- [program arguments]
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</pre>
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</div>
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<p>Similarly, to debug the LLC, one would run:</p>
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<div class="doc_code">
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<pre>
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bugpoint -run-llc -output=[correct output file] [bitcode file] \
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--tool-args -- [arguments to pass to llc] \
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--args -- [program arguments]
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</pre>
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</div>
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<p><b>Special note:</b> if you are debugging MultiSource or SPEC tests that
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already exist in the <tt>llvm/test</tt> hierarchy, there is an easier way to
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debug the JIT, LLC, and CBE, using the pre-written Makefile targets, which
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will pass the program options specified in the Makefiles:</p>
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<div class="doc_code">
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<p><tt>
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cd llvm/test/../../program<br>
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make bugpoint-jit
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</tt></p>
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</div>
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<p>At the end of a successful <tt>bugpoint</tt> run, you will be presented
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with two bitcode files: a <em>safe</em> file which can be compiled with the C
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backend and the <em>test</em> file which either LLC or the JIT
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mis-codegenerates, and thus causes the error.</p>
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<p>To reproduce the error that <tt>bugpoint</tt> found, it is sufficient to do
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the following:</p>
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<ol>
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<li><p>Regenerate the shared object from the safe bitcode file:</p>
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<div class="doc_code">
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<p><tt>
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<b>llc</b> -march=c safe.bc -o safe.c<br>
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<b>gcc</b> -shared safe.c -o safe.so
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</tt></p>
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</div></li>
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<li><p>If debugging LLC, compile test bitcode native and link with the shared
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object:</p>
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<div class="doc_code">
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<p><tt>
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<b>llc</b> test.bc -o test.s<br>
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<b>gcc</b> test.s safe.so -o test.llc<br>
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./test.llc [program options]
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</tt></p>
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</div></li>
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<li><p>If debugging the JIT, load the shared object and supply the test
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bitcode:</p>
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<div class="doc_code">
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<p><tt><b>lli</b> -load=safe.so test.bc [program options]</tt></p>
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</div></li>
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</ol>
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||||
</div>
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||||
|
||||
<!-- *********************************************************************** -->
|
||||
<hr>
|
||||
<address>
|
||||
<a href="http://jigsaw.w3.org/css-validator/check/referer"><img
|
||||
src="http://jigsaw.w3.org/css-validator/images/vcss-blue" alt="Valid CSS"></a>
|
||||
<a href="http://validator.w3.org/check/referer"><img
|
||||
src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a>
|
||||
|
||||
<a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
|
||||
<a href="http://llvm.org/">The LLVM Compiler Infrastructure</a>
|
||||
<br>
|
||||
Last modified: $Date$
|
||||
</address>
|
||||
|
||||
</body>
|
||||
</html>
|
||||
|
|
@ -0,0 +1,233 @@
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|||
.. _how-to-submit-a-bug-report:
|
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================================
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||||
How to submit an LLVM bug report
|
||||
================================
|
||||
|
||||
.. sectionauthor:: Chris Lattner <sabre@nondot.org> and Misha Brukman <http://misha.brukman.net>
|
||||
|
||||
Introduction - Got bugs?
|
||||
========================
|
||||
|
||||
|
||||
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.
|
||||
|
||||
Basically you have to do two things at a minimum. First, decide whether
|
||||
the bug `crashes the compiler`_ (or an LLVM pass), or if the
|
||||
compiler is `miscompiling`_ the program (i.e., the
|
||||
compiler successfully produces an executable, but it doesn't run right).
|
||||
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.
|
||||
|
||||
Once you have a reduced test-case, go to `the LLVM Bug Tracking System
|
||||
<http://llvm.org/bugs/enter_bug.cgi>`_ and fill out the form with the
|
||||
necessary details (note that you don't need to pick a category, just use
|
||||
the "new-bugs" category if you're not sure). The bug description should
|
||||
contain the following information:
|
||||
|
||||
* All information necessary to reproduce the problem.
|
||||
* The reduced test-case that triggers the bug.
|
||||
* The location where you obtained LLVM (if not from our Subversion
|
||||
repository).
|
||||
|
||||
Thanks for helping us make LLVM better!
|
||||
|
||||
.. _crashes the compiler:
|
||||
|
||||
Crashing Bugs
|
||||
=============
|
||||
|
||||
More often than not, bugs in the compiler cause it to crash---often due to
|
||||
an assertion failure of some sort. The most important piece of the puzzle
|
||||
is to figure out if it is crashing in the GCC front-end or if it is one of
|
||||
the LLVM libraries (e.g. the optimizer or code generator) that has
|
||||
problems.
|
||||
|
||||
To figure out which component is crashing (the front-end, optimizer or code
|
||||
generator), run the ``llvm-gcc`` command line as you were when the crash
|
||||
occurred, but with the following extra command line options:
|
||||
|
||||
* ``-O0 -emit-llvm``: If ``llvm-gcc`` still crashes when passed these
|
||||
options (which disable the optimizer and code generator), then the crash
|
||||
is in the front-end. Jump ahead to the section on :ref:`front-end bugs
|
||||
<front-end>`.
|
||||
|
||||
* ``-emit-llvm``: If ``llvm-gcc`` crashes with this option (which disables
|
||||
the code generator), you found an optimizer bug. Jump ahead to
|
||||
`compile-time optimization bugs`_.
|
||||
|
||||
* Otherwise, you have a code generator crash. Jump ahead to `code
|
||||
generator bugs`_.
|
||||
|
||||
.. _front-end bug:
|
||||
.. _front-end:
|
||||
|
||||
Front-end bugs
|
||||
--------------
|
||||
|
||||
If the problem is in the front-end, you should re-run the same ``llvm-gcc``
|
||||
command that resulted in the crash, but add the ``-save-temps`` option.
|
||||
The compiler will crash again, but it will leave behind a ``foo.i`` file
|
||||
(containing preprocessed C source code) and possibly ``foo.s`` for each
|
||||
compiled ``foo.c`` file. Send us the ``foo.i`` file, along with the options
|
||||
you passed to ``llvm-gcc``, and a brief description of the error it caused.
|
||||
|
||||
The `delta <http://delta.tigris.org/>`_ tool helps to reduce the
|
||||
preprocessed file down to the smallest amount of code that still replicates
|
||||
the problem. You're encouraged to use delta to reduce the code to make the
|
||||
developers' lives easier. `This website
|
||||
<http://gcc.gnu.org/wiki/A_guide_to_testcase_reduction>`_ has instructions
|
||||
on the best way to use delta.
|
||||
|
||||
.. _compile-time optimization bugs:
|
||||
|
||||
Compile-time optimization bugs
|
||||
------------------------------
|
||||
|
||||
If you find that a bug crashes in the optimizer, compile your test-case to a
|
||||
``.bc`` file by passing "``-emit-llvm -O0 -c -o foo.bc``".
|
||||
Then run:
|
||||
|
||||
.. code-block:: bash
|
||||
|
||||
opt -std-compile-opts -debug-pass=Arguments foo.bc -disable-output
|
||||
|
||||
This command should do two things: it should print out a list of passes, and
|
||||
then it should crash in the same way as llvm-gcc. If it doesn't crash, please
|
||||
follow the instructions for a `front-end bug`_.
|
||||
|
||||
If this does crash, then you should be able to debug this with the following
|
||||
bugpoint command:
|
||||
|
||||
.. code-block:: bash
|
||||
|
||||
bugpoint foo.bc <list of passes printed by opt>
|
||||
|
||||
Please run this, then file a bug with the instructions and reduced .bc
|
||||
files that bugpoint emits. If something goes wrong with bugpoint, please
|
||||
submit the "foo.bc" file and the list of passes printed by ``opt``.
|
||||
|
||||
.. _code generator bugs:
|
||||
|
||||
Code generator bugs
|
||||
-------------------
|
||||
|
||||
If you find a bug that crashes llvm-gcc in the code generator, compile your
|
||||
source file to a .bc file by passing "``-emit-llvm -c -o foo.bc``" to
|
||||
llvm-gcc (in addition to the options you already pass). Once your have
|
||||
foo.bc, one of the following commands should fail:
|
||||
|
||||
#. ``llc foo.bc``
|
||||
#. ``llc foo.bc -relocation-model=pic``
|
||||
#. ``llc foo.bc -relocation-model=static``
|
||||
|
||||
If none of these crash, please follow the instructions for a `front-end
|
||||
bug`_. If one of these do crash, you should be able to reduce this with
|
||||
one of the following bugpoint command lines (use the one corresponding to
|
||||
the command above that failed):
|
||||
|
||||
#. ``bugpoint -run-llc foo.bc``
|
||||
#. ``bugpoint -run-llc foo.bc --tool-args -relocation-model=pic``
|
||||
#. ``bugpoint -run-llc foo.bc --tool-args -relocation-model=static``
|
||||
|
||||
Please run this, then file a bug with the instructions and reduced .bc file
|
||||
that bugpoint emits. If something goes wrong with bugpoint, please submit
|
||||
the "foo.bc" file and the option that llc crashes with.
|
||||
|
||||
.. _miscompiling:
|
||||
|
||||
Miscompilations
|
||||
===============
|
||||
|
||||
If llvm-gcc successfully produces an executable, but that executable
|
||||
doesn't run right, this is either a bug in the code or a bug in the
|
||||
compiler. The first thing to check is to make sure it is not using
|
||||
undefined behavior (e.g. reading a variable before it is defined). In
|
||||
particular, check to see if the program `valgrind
|
||||
<http://valgrind.org/>`_'s clean, passes purify, or some other memory
|
||||
checker tool. Many of the "LLVM bugs" that we have chased down ended up
|
||||
being bugs in the program being compiled, not LLVM.
|
||||
|
||||
Once you determine that the program itself is not buggy, you should choose
|
||||
which code generator you wish to compile the program with (e.g. LLC or the JIT)
|
||||
and optionally a series of LLVM passes to run. For example:
|
||||
|
||||
.. code-block:: bash
|
||||
|
||||
bugpoint -run-llc [... optzn passes ...] file-to-test.bc --args -- [program arguments]
|
||||
|
||||
bugpoint will try to narrow down your list of passes to the one pass that
|
||||
causes an error, and simplify the bitcode file as much as it can to assist
|
||||
you. It will print a message letting you know how to reproduce the
|
||||
resulting error.
|
||||
|
||||
Incorrect code generation
|
||||
=========================
|
||||
|
||||
Similarly to debugging incorrect compilation by mis-behaving passes, you
|
||||
can debug incorrect code generation by either LLC or the JIT, using
|
||||
``bugpoint``. The process ``bugpoint`` follows in this case is to try to
|
||||
narrow the code down to a function that is miscompiled by one or the other
|
||||
method, but since for correctness, the entire program must be run,
|
||||
``bugpoint`` will compile the code it deems to not be affected with the C
|
||||
Backend, and then link in the shared object it generates.
|
||||
|
||||
To debug the JIT:
|
||||
|
||||
.. code-block:: bash
|
||||
|
||||
bugpoint -run-jit -output=[correct output file] [bitcode file] \
|
||||
--tool-args -- [arguments to pass to lli] \
|
||||
--args -- [program arguments]
|
||||
|
||||
Similarly, to debug the LLC, one would run:
|
||||
|
||||
.. code-block:: bash
|
||||
|
||||
bugpoint -run-llc -output=[correct output file] [bitcode file] \
|
||||
--tool-args -- [arguments to pass to llc] \
|
||||
--args -- [program arguments]
|
||||
|
||||
**Special note:** if you are debugging MultiSource or SPEC tests that
|
||||
already exist in the ``llvm/test`` hierarchy, there is an easier way to
|
||||
debug the JIT, LLC, and CBE, using the pre-written Makefile targets, which
|
||||
will pass the program options specified in the Makefiles:
|
||||
|
||||
.. code-block:: bash
|
||||
|
||||
cd llvm/test/../../program
|
||||
make bugpoint-jit
|
||||
|
||||
At the end of a successful ``bugpoint`` run, you will be presented
|
||||
with two bitcode files: a *safe* file which can be compiled with the C
|
||||
backend and the *test* file which either LLC or the JIT
|
||||
mis-codegenerates, and thus causes the error.
|
||||
|
||||
To reproduce the error that ``bugpoint`` found, it is sufficient to do
|
||||
the following:
|
||||
|
||||
#. Regenerate the shared object from the safe bitcode file:
|
||||
|
||||
.. code-block:: bash
|
||||
|
||||
llc -march=c safe.bc -o safe.c
|
||||
gcc -shared safe.c -o safe.so
|
||||
|
||||
#. If debugging LLC, compile test bitcode native and link with the shared
|
||||
object:
|
||||
|
||||
.. code-block:: bash
|
||||
|
||||
llc test.bc -o test.s
|
||||
gcc test.s safe.so -o test.llc
|
||||
./test.llc [program options]
|
||||
|
||||
#. If debugging the JIT, load the shared object and supply the test
|
||||
bitcode:
|
||||
|
||||
.. code-block:: bash
|
||||
|
||||
lli -load=safe.so test.bc [program options]
|
||||
|
|
@ -15,6 +15,7 @@ User Guides
|
|||
Packaging
|
||||
HowToAddABuilder
|
||||
yaml2obj
|
||||
HowToSubmitABug
|
||||
|
||||
* `The LLVM Getting Started Guide <GettingStarted.html>`_
|
||||
|
||||
|
|
@ -59,7 +60,7 @@ User Guides
|
|||
|
||||
This describes new features, known bugs, and other limitations.
|
||||
|
||||
* `How to Submit A Bug Report <HowToSubmitABug.html>`_
|
||||
* :ref:`how-to-submit-a-bug-report`
|
||||
|
||||
Instructions for properly submitting information about any bugs you run into
|
||||
in the LLVM system.
|
||||
|
|
|
|||
Loading…
Reference in New Issue