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Chris Lattner1213bc72003-10-07 20:33:30 +0000[diff] [blame]1<html>
2<title>LLVM: bugpoint tool</title>
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4<body bgcolor=white>
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6<center><h1>LLVM: <tt>bugpoint</tt> tool</h1></center>
7<HR>
8
9<h3>NAME</h3>
10<tt>bugpoint</tt>
11
12<h3>SYNOPSIS</h3>
Brian Gaekeb9b3c332003-10-19 17:03:59 +0000[diff] [blame]13<tt>bugpoint [options] [input LLVM ll/bc files] [LLVM passes] --args &lt;program arguments&gt;...</tt>
Chris Lattner1213bc72003-10-07 20:33:30 +0000[diff] [blame]14
15<img src="../Debugging.gif" width=444 height=314 align=right>
16<h3>DESCRIPTION</h3>
17
Brian Gaeke237b3662003-10-19 17:20:15 +0000[diff] [blame]18The <tt>bugpoint</tt> tool narrows down the source of
Chris Lattnerd1eb6f72003-10-18 20:36:15 +0000[diff] [blame]19problems in LLVM tools and passes. It can be used to debug three types of
20failures: optimizer crashes, miscompilations by optimizers, or invalid native
Brian Gaeke237b3662003-10-19 17:20:15 +0000[diff] [blame]21code generation. It aims to reduce large test cases to small, useful ones.
22For example,
Chris Lattnerd1eb6f72003-10-18 20:36:15 +0000[diff] [blame]23if <tt><a href="gccas.html">gccas</a></tt> crashes while optimizing a file, it
24will identify the optimization (or combination of optimizations) that causes the
25crash, and reduce the file down to a small example which triggers the crash.<p>
Chris Lattner1213bc72003-10-07 20:33:30 +0000[diff] [blame]26
Brian Gaeke237b3662003-10-19 17:20:15 +0000[diff] [blame]27<a name="designphilosophy">
28<h4>Design Philosophy</h4>
29
Chris Lattner129e7a82003-10-19 17:27:12 +0000[diff] [blame]30<tt>bugpoint</tt> is designed to be a useful tool without requiring any
Brian Gaekeb9b3c332003-10-19 17:03:59 +0000[diff] [blame]31hooks into the LLVM infrastructure at all. It works with any and all LLVM
Chris Lattner5cd840c2003-10-18 20:54:37 +0000[diff] [blame]32passes and code generators, and does not need to "know" how they work. Because
33of this, it may appear to do a lot of stupid things or miss obvious
Brian Gaeke237b3662003-10-19 17:20:15 +0000[diff] [blame]34simplifications. <tt>bugpoint</tt> is also designed to trade off programmer
35time for computer time in the compiler-debugging process; consequently, it may
36take a long period of (unattended) time to reduce a test case, but we feel it
37is still worth it. :-) <p>
Chris Lattner5cd840c2003-10-18 20:54:37 +0000[diff] [blame]38
Brian Gaeke6ff33102003-10-19 17:30:36 +0000[diff] [blame]39<a name="automaticdebuggerselection">
40<h4>Automatic Debugger Selection</h4>
Chris Lattner5cd840c2003-10-18 20:54:37 +0000[diff] [blame]41
Brian Gaeke237b3662003-10-19 17:20:15 +0000[diff] [blame]42<tt>bugpoint</tt> reads each <tt>.bc</tt> or <tt>.ll</tt> file
43specified on the command line and links them together into a single module,
44called the test program. If any LLVM passes are
45specified on the command line, it runs these passes on the test program. If
Brian Gaeke6ff33102003-10-19 17:30:36 +0000[diff] [blame]46any of the passes crash, or if they produce malformed output,
47<tt>bugpoint</tt> starts the <a href="#crashdebug">crash debugger</a>.<p>
Chris Lattner1213bc72003-10-07 20:33:30 +0000[diff] [blame]48
Chris Lattnerd1eb6f72003-10-18 20:36:15 +0000[diff] [blame]49Otherwise, if the <a href="#opt_output"><tt>-output</tt></a> option was not
Chris Lattnereb373aa2004-02-18 23:30:21 +0000[diff] [blame]50specified, <tt>bugpoint</tt> runs the test program with the C backend (which is
51assumed to generate good code) to generate a reference output. Once
Brian Gaeke237b3662003-10-19 17:20:15 +0000[diff] [blame]52<tt>bugpoint</tt> has a reference output for the test program, it tries
Chris Lattnereb373aa2004-02-18 23:30:21 +0000[diff] [blame]53executing it with the <a href="#opt_run-">selected</a> code generator. If the
54selected code generator crashes, <tt>bugpoint</tt> starts the <a
55href="#crashdebug">crash debugger</a> on the code generator. Otherwise, if the
56resulting output differs from the reference output, it assumes the difference
57resulted from a code generator failure, and starts the <a
58href="#codegendebug">code generator debugger</a>.<p>
Chris Lattnerd1eb6f72003-10-18 20:36:15 +0000[diff] [blame]59
Chris Lattnereb373aa2004-02-18 23:30:21 +0000[diff] [blame]60Finally, if the output of the selected code generator matches the reference
61output, <tt>bugpoint</tt> runs the test program after all of the LLVM passes
62have been applied to it. If its output differs from the reference output, it
63assumes the difference resulted from a failure in one of the LLVM passes, and
64enters the <a href="#miscompilationdebug">miscompilation
65debugger</a>. Otherwise, there is no problem <tt>bugpoint</tt> can debug.<p>
Chris Lattnerd1eb6f72003-10-18 20:36:15 +0000[diff] [blame]66
67<a name="crashdebug">
Brian Gaeke6ff33102003-10-19 17:30:36 +0000[diff] [blame]68<h4>Crash debugger</h4>
Chris Lattner1213bc72003-10-07 20:33:30 +0000[diff] [blame]69
Chris Lattnereb373aa2004-02-18 23:30:21 +0000[diff] [blame]70If an optimizer or code generator crashes, <tt>bugpoint</tt> will try as hard as
71it can to reduce the list of passes (for optimizer crashes) and the size of the
72test program. First, <tt>bugpoint</tt> figures out which combination of
73optimizer passes triggers the bug. This is useful when debugging a problem
74exposed by <tt>gccas</tt>, for example, because it runs over 25
75optimizations.<p>
Misha Brukman3f717222003-10-16 18:14:43 +0000[diff] [blame]76
Brian Gaeke6ff33102003-10-19 17:30:36 +0000[diff] [blame]77Next, <tt>bugpoint</tt> tries removing functions from the test program, to
Chris Lattnereb373aa2004-02-18 23:30:21 +0000[diff] [blame]78reduce its size. Usually it is able to reduce a test program to a single
79function, when debugging intraprocedural optimizations. Once the number of
Chris Lattnerd1eb6f72003-10-18 20:36:15 +0000[diff] [blame]80functions has been reduced, it attempts to delete various edges in the control
81flow graph, to reduce the size of the function as much as possible. Finally,
Brian Gaekeb9b3c332003-10-19 17:03:59 +0000[diff] [blame]82<tt>bugpoint</tt> deletes any individual LLVM instructions whose absence does
Chris Lattnerd1eb6f72003-10-18 20:36:15 +0000[diff] [blame]83not eliminate the failure. At the end, <tt>bugpoint</tt> should tell you what
84passes crash, give you a bytecode file, and give you instructions on how to
Chris Lattnereb373aa2004-02-18 23:30:21 +0000[diff] [blame]85reproduce the failure with <tt><a href="opt.html">opt</a></tt>, <tt><a
86href="analyze.html">analyze</a></tt>, or <tt><a href="llc.html">llc</a></tt>.<p>
Chris Lattner1213bc72003-10-07 20:33:30 +0000[diff] [blame]87
Chris Lattnerd1eb6f72003-10-18 20:36:15 +0000[diff] [blame]88<a name="codegendebug">
Brian Gaeke6ff33102003-10-19 17:30:36 +0000[diff] [blame]89<h4>Code generator debugger</h4>
Chris Lattner1213bc72003-10-07 20:33:30 +0000[diff] [blame]90
Chris Lattner5cd840c2003-10-18 20:54:37 +0000[diff] [blame]91The code generator debugger attempts to narrow down the amount of code that is
92being miscompiled by the <a href="#opt_run-">selected</a> code generator. To do
Brian Gaeke6ff33102003-10-19 17:30:36 +0000[diff] [blame]93this, it takes the test program and partitions it into two pieces: one piece
Chris Lattner5cd840c2003-10-18 20:54:37 +0000[diff] [blame]94which it compiles with the C backend (into a shared object), and one piece which
95it runs with either the JIT or the static LLC compiler. It uses several
96techniques to reduce the amount of code pushed through the LLVM code generator,
97to reduce the potential scope of the problem. After it is finished, it emits
Brian Gaeke6ff33102003-10-19 17:30:36 +0000[diff] [blame]98two bytecode files (called "test" [to be compiled with the code generator] and
99"safe" [to be compiled with the C backend] respectively), and instructions for
100reproducing the problem. The code generator debugger assumes that the C
101backend produces good code.<p>
Chris Lattner5cd840c2003-10-18 20:54:37 +0000[diff] [blame]102
Brian Gaeke6ff33102003-10-19 17:30:36 +0000[diff] [blame]103If you are using the code generator debugger and get an error message that
Misha Brukman65797b82003-10-20 19:47:25 +0000[diff] [blame]104says "UNSUPPORTED: external function used as a global initializer!", try using
105the <tt>-run-llc</tt> option instead of the <tt>-run-jit</tt> option. This is
106due to an unimplemented feature in the code generator debugger.<p>
Chris Lattner1213bc72003-10-07 20:33:30 +0000[diff] [blame]107
Chris Lattnerd1eb6f72003-10-18 20:36:15 +0000[diff] [blame]108<a name="miscompilationdebug">
Brian Gaeke6ff33102003-10-19 17:30:36 +0000[diff] [blame]109<h4>Miscompilation debugger</h4>
Chris Lattner1213bc72003-10-07 20:33:30 +0000[diff] [blame]110
Brian Gaeke6ff33102003-10-19 17:30:36 +0000[diff] [blame]111The miscompilation debugger works similarly to the code generator
112debugger. It works by splitting the test program into two pieces, running the
113optimizations specified on one piece, linking the two pieces back together,
114and then executing the result.
Chris Lattner5cd840c2003-10-18 20:54:37 +0000[diff] [blame]115It attempts to narrow down the list of passes to the one (or few) which are
Brian Gaeke6ff33102003-10-19 17:30:36 +0000[diff] [blame]116causing the miscompilation, then reduce the portion of the test program which is
117being miscompiled. The miscompilation debugger assumes that the selected
118code generator is working properly.<p>
Chris Lattner1213bc72003-10-07 20:33:30 +0000[diff] [blame]119
Chris Lattner634ec562003-10-18 21:34:15 +0000[diff] [blame]120<a name="bugpoint notes">
121<h4>Advice for using <tt>bugpoint</tt></h4>
122
123<tt>bugpoint</tt> can be a remarkably useful tool, but it sometimes works in
124non-obvious ways. Here are some hints and tips:<p>
125
126<ol>
Brian Gaeke6ff33102003-10-19 17:30:36 +0000[diff] [blame]127<li>In the code generator and miscompilation debuggers, <tt>bugpoint</tt> only
Chris Lattner634ec562003-10-18 21:34:15 +0000[diff] [blame]128 works with programs that have deterministic output. Thus, if the program
Brian Gaekeb9b3c332003-10-19 17:03:59 +0000[diff] [blame]129 outputs the date, time, or any other "random" data, <tt>bugpoint</tt> may
130 misinterpret differences in these data, when output, as the result of a
131 miscompilation. Programs should be temporarily modified to disable
132 outputs that are likely to vary from run to run.
Chris Lattner634ec562003-10-18 21:34:15 +0000[diff] [blame]133
Brian Gaeke6ff33102003-10-19 17:30:36 +0000[diff] [blame]134<li>In the code generator and miscompilation debuggers, debugging will go
Chris Lattner634ec562003-10-18 21:34:15 +0000[diff] [blame]135 faster if you manually modify the program or its inputs to reduce the
136 runtime, but still exhibit the problem.
137
138<li><tt>bugpoint</tt> is extremely useful when working on a new optimization:
139 it helps track down regressions quickly. To avoid having to relink
Brian Gaekeb9b3c332003-10-19 17:03:59 +0000[diff] [blame]140 <tt>bugpoint</tt> every time you change your optimization however, have
Chris Lattner634ec562003-10-18 21:34:15 +0000[diff] [blame]141 <tt>bugpoint</tt> dynamically load your optimization with the <a
142 href="#opt_load"><tt>-load</tt></a> option.
143
144<li><tt>bugpoint</tt> can generate a lot of output and run for a long period of
145 time. It is often useful to capture the output of the program to file. For
Brian Gaekeb9b3c332003-10-19 17:03:59 +0000[diff] [blame]146 example, in the C shell, you can type:<br>
Chris Lattnere99e7342003-10-19 17:37:33 +0000[diff] [blame]147 <tt>bugpoint ..... |&amp; tee bugpoint.log</tt>
Brian Gaekeb9b3c332003-10-19 17:03:59 +0000[diff] [blame]148 <br>to get a copy of <tt>bugpoint</tt>'s output in the file
Brian Gaeke768a3182003-10-19 17:37:12 +0000[diff] [blame]149 <tt>bugpoint.log</tt>, as well as on your terminal.
Chris Lattner634ec562003-10-18 21:34:15 +0000[diff] [blame]150
Brian Gaeke6ff33102003-10-19 17:30:36 +0000[diff] [blame]151<li><tt>bugpoint</tt> cannot debug problems with the linker. If
152 <tt>bugpoint</tt> crashes before you see its "All input ok" message,
153 you might try <tt>llvm-link -v</tt> on the same set of input files. If
154 that also crashes, you may be experiencing a linker bug.
Brian Gaeke421f3172004-02-11 18:44:55 +0000[diff] [blame]155
156<li>If your program is <b>supposed</b> to crash, <tt>bugpoint</tt> will be
157 confused. One way to deal with this is to cause bugpoint to ignore the exit
158 code from your program, by giving it the <tt>-check-exit-code=false</tt>
159 option.
Brian Gaeke6ff33102003-10-19 17:30:36 +0000[diff] [blame]160
Chris Lattner634ec562003-10-18 21:34:15 +0000[diff] [blame]161</ol>
162
Chris Lattner1213bc72003-10-07 20:33:30 +0000[diff] [blame]163<h3>OPTIONS</h3>
164
165<ul>
John Criswellf9c78652004-01-26 21:26:54 +0000[diff] [blame]166 <li><tt>-additional-so &lt;library&gt;</tt><br>
167 Load <tt>&lt;library&gt;</tt> into the test program whenever it is run.
Brian Gaekeb9b3c332003-10-19 17:03:59 +0000[diff] [blame]168 This is useful if you are debugging programs which depend on non-LLVM
169 libraries (such as the X or curses libraries) to run.<p>
Chris Lattner1213bc72003-10-07 20:33:30 +0000[diff] [blame]170
Brian Gaekeb9b3c332003-10-19 17:03:59 +0000[diff] [blame]171 <li><tt>-args &lt;program args&gt;</tt><br>
172 Pass all arguments specified after <tt>-args</tt> to the
173 test program whenever it runs. Note that if any of
174 the <tt>&lt;program args&gt;</tt> start with a '-', you should use:
Chris Lattner0b4ffea2003-10-18 20:57:23 +0000[diff] [blame]175 <p>
Brian Gaekeb9b3c332003-10-19 17:03:59 +0000[diff] [blame]176 <tt>bugpoint &lt;bugpoint args&gt; -args -- &lt;program args&gt;</tt>
Chris Lattner0b4ffea2003-10-18 20:57:23 +0000[diff] [blame]177 <p>
178 The "<tt>--</tt>" right after the <tt>-args</tt> option tells
179 <tt>bugpoint</tt> to consider any options starting with <tt>-</tt> to be
180 part of the <tt>-args</tt> option, not as options to <tt>bugpoint</tt>
181 itself.<p>
Chris Lattner5cd840c2003-10-18 20:54:37 +0000[diff] [blame]182
Brian Gaeke4fda7762004-02-11 18:40:04 +0000[diff] [blame]183 <li><tt>-check-exit-code={true,false}</tt><br>
184 Assume a non-zero exit code or core dump from the test program is
185 a failure. Defaults to true.<p>
186
Chris Lattner6a6d2a22004-03-13 19:36:30 +0000[diff] [blame^]187 <li><tt>-disable-{dce,simplifycfg}</tt><br>
Brian Gaekeb9b3c332003-10-19 17:03:59 +0000[diff] [blame]188 Do not run the specified passes to clean up and reduce the size of the
189 test program. By default, <tt>bugpoint</tt> uses these passes internally
190 when attempting to reduce test programs. If you're trying to find
191 a bug in one of these passes, <tt>bugpoint</tt> may crash.<p>
Chris Lattner1213bc72003-10-07 20:33:30 +0000[diff] [blame]192
Chris Lattner5cd840c2003-10-18 20:54:37 +0000[diff] [blame]193 <li> <tt>-help</tt><br>
194 Print a summary of command line options.<p>
Chris Lattner1213bc72003-10-07 20:33:30 +0000[diff] [blame]195
Chris Lattner5cd840c2003-10-18 20:54:37 +0000[diff] [blame]196 <a name="opt_input"><li><tt>-input &lt;filename&gt;</tt><br>
Brian Gaekeb9b3c332003-10-19 17:03:59 +0000[diff] [blame]197 Open <tt>&lt;filename&gt;</tt> and redirect the standard input of the
198 test program, whenever it runs, to come from that file.
Chris Lattner1213bc72003-10-07 20:33:30 +0000[diff] [blame]199 <p>
200
John Criswellf9c78652004-01-26 21:26:54 +0000[diff] [blame]201 <a name="opt_load"><li> <tt>-load &lt;plugin&gt;</tt><br>
202 Load the dynamic object <tt>&lt;plugin&gt;</tt> into <tt>bugpoint</tt>
Brian Gaekeb9b3c332003-10-19 17:03:59 +0000[diff] [blame]203 itself. This object should register new
Chris Lattner1213bc72003-10-07 20:33:30 +0000[diff] [blame]204 optimization passes. Once loaded, the object will add new command line
205 options to enable various optimizations. To see the new complete list
206 of optimizations, use the -help and -load options together:
207 <p>
John Criswellf9c78652004-01-26 21:26:54 +0000[diff] [blame]208 <tt>bugpoint -load &lt;plugin&gt; -help</tt>
Chris Lattner1213bc72003-10-07 20:33:30 +0000[diff] [blame]209 <p>
210
Chris Lattner5cd840c2003-10-18 20:54:37 +0000[diff] [blame]211 <a name="opt_output"><li><tt>-output &lt;filename&gt;</tt><br>
Brian Gaekeb9b3c332003-10-19 17:03:59 +0000[diff] [blame]212 Whenever the test program produces output on its standard output
213 stream, it should match the contents of <tt>&lt;filename&gt;</tt>
214 (the "reference output"). If you do not use this option,
215 <tt>bugpoint</tt> will attempt to generate a reference output by
216 compiling the program with the C backend and running it.<p>
Chris Lattner1213bc72003-10-07 20:33:30 +0000[diff] [blame]217
Brian Gaeke28dbfce2003-10-19 17:35:35 +0000[diff] [blame]218 <a name="opt_run-"><li><tt>-run-{int,jit,llc,cbe}</tt><br>
Brian Gaekeb9b3c332003-10-19 17:03:59 +0000[diff] [blame]219 Whenever the test program is compiled, <tt>bugpoint</tt> should generate
220 code for it using the specified code generator. These options allow
221 you to choose the interpreter, the JIT compiler, the static native
222 code compiler, or the C backend, respectively.<p>
Chris Lattner1213bc72003-10-07 20:33:30 +0000[diff] [blame]223</ul>
224
225<h3>EXIT STATUS</h3>
226
227If <tt>bugpoint</tt> succeeds in finding a problem, it will exit with 0.
228Otherwise, if an error occurs, it will exit with a non-zero value.
229
230<h3>SEE ALSO</h3>
John Criswell589d91f2003-10-16 20:15:17 +0000[diff] [blame]231<a href="opt.html"><tt>opt</tt></a>,
Chris Lattner1213bc72003-10-07 20:33:30 +0000[diff] [blame]232<a href="analyze.html"><tt>analyze</tt></a>
233
234<HR>
235Maintained by the <a href="http://llvm.cs.uiuc.edu">LLVM Team</a>.
236</body>
237</html>