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LLVM bugpoint tool: design and usage
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<ul>
<li><a href="#desc">Description</a></li>
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<a name="desc">Description</a>
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<p><tt>bugpoint</tt> narrows down the source of problems in LLVM tools and
passes. It can be used to debug three types of failures: optimizer crashes,
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<a name="design">Design Philosophy</a>
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<p><tt>bugpoint</tt> is designed to be a useful tool without requiring any
hooks into the LLVM infrastructure at all. It works with any and all LLVM
debugging a miscompilation where each test of the program (which requires
executing it) takes a long time.</p>
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<a name="autoselect">Automatic Debugger Selection</a>
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<p><tt>bugpoint</tt> reads each <tt>.bc</tt> or <tt>.ll</tt> file specified on
the command line and links them together into a single module, called the test
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<a name="crashdebug">Crash debugger</a>
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<p>If an optimizer or code generator crashes, <tt>bugpoint</tt> will try as hard
as it can to reduce the list of passes (for optimizer crashes) and the size of
flow graph, to reduce the size of the function as much as possible. Finally,
<tt>bugpoint</tt> deletes any individual LLVM instructions whose absence does
not eliminate the failure. At the end, <tt>bugpoint</tt> should tell you what
-passes crash, give you a bytecode file, and give you instructions on how to
+passes crash, give you a bitcode file, and give you instructions on how to
reproduce the failure with <tt>opt</tt> or <tt>llc</tt>.</p>
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<a name="codegendebug">Code generator debugger</a>
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+</h3>
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<p>The code generator debugger attempts to narrow down the amount of code that
is being miscompiled by the selected code generator. To do this, it takes the
with the C backend (into a shared object), and one piece which it runs with
either the JIT or the static LLC compiler. It uses several techniques to
reduce the amount of code pushed through the LLVM code generator, to reduce the
-potential scope of the problem. After it is finished, it emits two bytecode
+potential scope of the problem. After it is finished, it emits two bitcode
files (called "test" [to be compiled with the code generator] and "safe" [to be
compiled with the C backend], respectively), and instructions for reproducing
the problem. The code generator debugger assumes that the C backend produces
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<a name="miscompilationdebug">Miscompilation debugger</a>
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<p>The miscompilation debugger works similarly to the code generator debugger.
It works by splitting the test program into two pieces, running the
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+<h2>
<a name="advice">Advice for using bugpoint</a>
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<tt>bugpoint</tt> can be a remarkably useful tool, but it sometimes works in
non-obvious ways. Here are some hints and tips:<p>
you might try <tt>llvm-link -v</tt> on the same set of input files. If
that also crashes, you may be experiencing a linker bug.
-<li>If your program is <b>supposed</b> to crash, <tt>bugpoint</tt> will be
- confused. One way to deal with this is to cause bugpoint to ignore the exit
- code from your program, by giving it the <tt>-check-exit-code=false</tt>
- option.
-
<li><tt>bugpoint</tt> is useful for proactively finding bugs in LLVM.
Invoking <tt>bugpoint</tt> with the <tt>-find-bugs</tt> option will cause
the list of specified optimizations to be randomized and applied to the
program. This process will repeat until a bug is found or the user
kills <tt>bugpoint</tt>.
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</ol>
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<a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
- <a href="http://llvm.org">LLVM Compiler Infrastructure</a><br>
+ <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
Last modified: $Date$
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projects / oota-llvm.git / blobdiff