diff options
Diffstat (limited to 'docs/CommandGuide/bugpoint.html')
| -rw-r--r-- | docs/CommandGuide/bugpoint.html | 249 |
1 files changed, 0 insertions, 249 deletions
diff --git a/docs/CommandGuide/bugpoint.html b/docs/CommandGuide/bugpoint.html deleted file mode 100644 index 519e02d527..0000000000 --- a/docs/CommandGuide/bugpoint.html +++ /dev/null @@ -1,249 +0,0 @@ -<html> -<title>LLVM: bugpoint tool</title> - -<body bgcolor=white> - -<center><h1>LLVM: <tt>bugpoint</tt> tool</h1></center> -<HR> - -<h3>NAME</h3> -<tt>bugpoint</tt> - -<h3>SYNOPSIS</h3> -<tt>bugpoint [options] [input LLVM ll/bc files] [LLVM passes] --args <program arguments>...</tt> - -<img src="../img/Debugging.gif" width=444 height=314 align=right> -<h3>DESCRIPTION</h3> - -The <tt>bugpoint</tt> tool narrows down the source of -problems in LLVM tools and passes. It can be used to debug three types of -failures: optimizer crashes, miscompilations by optimizers, or bad native -code generation (including problems in the static and JIT compilers). It aims -to reduce large test cases to small, useful ones. For example, -if <tt><a href="gccas.html">gccas</a></tt> crashes while optimizing a file, it -will identify the optimization (or combination of optimizations) that causes the -crash, and reduce the file down to a small example which triggers the crash.<p> - -<a name="designphilosophy"> -<h4>Design Philosophy</h4> - -<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 -passes and code generators, and does not need to "know" how they work. Because -of this, it may appear to do stupid things or miss obvious -simplifications. <tt>bugpoint</tt> is also designed to trade off programmer -time for computer time in the compiler-debugging process; consequently, it may -take a long period of (unattended) time to reduce a test case, but we feel it -is still worth it. Note that <tt>bugpoint</tt> is generally very quick unless -debugging a miscompilation where each test of the program (which requires -executing it) takes a long time.<p> - -<a name="automaticdebuggerselection"> -<h4>Automatic Debugger Selection</h4> - -<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 program. If any LLVM passes are -specified on the command line, it runs these passes on the test program. If -any of the passes crash, or if they produce malformed output (which causes the -verifier to abort), -<tt>bugpoint</tt> starts the <a href="#crashdebug">crash debugger</a>.<p> - -Otherwise, if the <a href="#opt_output"><tt>-output</tt></a> option was not -specified, <tt>bugpoint</tt> runs the test program with the C backend (which is -assumed to generate good code) to generate a reference output. Once -<tt>bugpoint</tt> has a reference output for the test program, it tries -executing it with the <a href="#opt_run-">selected</a> code generator. If the -selected code generator crashes, <tt>bugpoint</tt> starts the <a -href="#crashdebug">crash debugger</a> on the code generator. Otherwise, if the -resulting output differs from the reference output, it assumes the difference -resulted from a code generator failure, and starts the <a -href="#codegendebug">code generator debugger</a>.<p> - -Finally, if the output of the selected code generator matches the reference -output, <tt>bugpoint</tt> runs the test program after all of the LLVM passes -have been applied to it. If its output differs from the reference output, it -assumes the difference resulted from a failure in one of the LLVM passes, and -enters the <a href="#miscompilationdebug">miscompilation -debugger</a>. Otherwise, there is no problem <tt>bugpoint</tt> can debug.<p> - -<a name="crashdebug"> -<h4>Crash debugger</h4> - -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 the -test program. First, <tt>bugpoint</tt> figures out which combination of -optimizer passes triggers the bug. This is useful when debugging a problem -exposed by <tt>gccas</tt>, for example, because it runs over 38 passes.<p> - -Next, <tt>bugpoint</tt> tries removing functions from the test program, to -reduce its size. Usually it is able to reduce a test program to a single -function, when debugging intraprocedural optimizations. Once the number of -functions has been reduced, it attempts to delete various edges in the control -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 -reproduce the failure with <tt><a href="opt.html">opt</a></tt>, <tt><a -href="analyze.html">analyze</a></tt>, or <tt><a href="llc.html">llc</a></tt>.<p> - -<a name="codegendebug"> -<h4>Code generator debugger</h4> - -<p>The code generator debugger attempts to narrow down the amount of code that -is being miscompiled by the <a href="#opt_run-">selected</a> code generator. To -do this, it takes the test program and partitions it into two pieces: one piece -which it compiles 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 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 good code.</p> - -<a name="miscompilationdebug"> -<h4>Miscompilation debugger</h4> - -The miscompilation debugger works similarly to the code generator -debugger. It works by splitting the test program into two pieces, running the -optimizations specified on one piece, linking the two pieces back together, -and then executing the result. -It attempts to narrow down the list of passes to the one (or few) which are -causing the miscompilation, then reduce the portion of the test program which is -being miscompiled. The miscompilation debugger assumes that the selected -code generator is working properly.<p> - -<a name="bugpoint notes"> -<h4>Advice for using <tt>bugpoint</tt></h4> - -<tt>bugpoint</tt> can be a remarkably useful tool, but it sometimes works in -non-obvious ways. Here are some hints and tips:<p> - -<ol> -<li>In the code generator and miscompilation debuggers, <tt>bugpoint</tt> only - works with programs that have deterministic output. Thus, if the program - outputs <tt>argv[0]</tt>, the date, time, or any other "random" data, <tt>bugpoint</tt> may - misinterpret differences in these data, when output, as the result of a - miscompilation. Programs should be temporarily modified to disable - outputs that are likely to vary from run to run. - -<li>In the code generator and miscompilation debuggers, debugging will go - faster if you manually modify the program or its inputs to reduce the - runtime, but still exhibit the problem. - -<li><tt>bugpoint</tt> is extremely useful when working on a new optimization: - it helps track down regressions quickly. To avoid having to relink - <tt>bugpoint</tt> every time you change your optimization however, have - <tt>bugpoint</tt> dynamically load your optimization with the <a - href="#opt_load"><tt>-load</tt></a> option. - -<li><tt>bugpoint</tt> can generate a lot of output and run for a long period of - time. It is often useful to capture the output of the program to file. For - example, in the C shell, you can type:<br> - <tt>bugpoint ..... |& tee bugpoint.log</tt> - <br>to get a copy of <tt>bugpoint</tt>'s output in the file - <tt>bugpoint.log</tt>, as well as on your terminal. - -<li><tt>bugpoint</tt> cannot debug problems with the LLVM linker. If - <tt>bugpoint</tt> crashes before you see its "All input ok" message, - 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. - -</ol> - -<h3>OPTIONS</h3> - -<ul> - <li><tt>-additional-so <library></tt><br> - Load <tt><library></tt> into the test program whenever it is run. - This is useful if you are debugging programs which depend on non-LLVM - libraries (such as the X or curses libraries) to run.<p> - - <li><tt>-args <program args></tt><br> - Pass all arguments specified after <tt>-args</tt> to the - test program whenever it runs. Note that if any of - the <tt><program args></tt> start with a '-', you should use: - <p> - <tt>bugpoint <bugpoint args> -args -- <program args></tt> - <p> - The "<tt>--</tt>" right after the <tt>-args</tt> option tells - <tt>bugpoint</tt> to consider any options starting with <tt>-</tt> to be - part of the <tt>-args</tt> option, not as options to <tt>bugpoint</tt> - itself.<p> - - <li><tt>-tool-args <tool args></tt><br> - Pass all arguments specified after <tt>-tool-args</tt> to the - LLVM tool under test (llc, lli, etc.) whenever it runs. - You should use this option in the following way: - <p> - <tt>bugpoint <bugpoint args> -tool-args -- <tool args></tt> - <p> - The "<tt>--</tt>" right after the <tt>-tool-args</tt> option tells - <tt>bugpoint</tt> to consider any options starting with <tt>-</tt> to be - part of the <tt>-tool-args</tt> option, not as options to - <tt>bugpoint</tt> itself. (See <tt>-args</tt>, above.)<p> - - <li><tt>-check-exit-code={true,false}</tt><br> - Assume a non-zero exit code or core dump from the test program is - a failure. Defaults to true.<p> - - <li><tt>-disable-{dce,simplifycfg}</tt><br> - Do not run the specified passes to clean up and reduce the size of the - test program. By default, <tt>bugpoint</tt> uses these passes internally - when attempting to reduce test programs. If you're trying to find - a bug in one of these passes, <tt>bugpoint</tt> may crash.<p> - - <li> <tt>-help</tt><br> - Print a summary of command line options.<p> - - <a name="opt_input"><li><tt>-input <filename></tt><br> - Open <tt><filename></tt> and redirect the standard input of the - test program, whenever it runs, to come from that file. - <p> - - <a name="opt_load"><li> <tt>-load <plugin></tt><br> - Load the dynamic object <tt><plugin></tt> into <tt>bugpoint</tt> - itself. This object should register new - optimization passes. Once loaded, the object will add new command line - options to enable various optimizations. To see the new complete list - of optimizations, use the -help and -load options together: - <p> - <tt>bugpoint -load <plugin> -help</tt> - <p> - - <a name="opt_output"><li><tt>-output <filename></tt><br> - Whenever the test program produces output on its standard output - stream, it should match the contents of <tt><filename></tt> - (the "reference output"). If you do not use this option, - <tt>bugpoint</tt> will attempt to generate a reference output by - compiling the program with the C backend and running it.<p> - - <li><tt>-profile-info-file <filename></tt><br> - Profile file loaded by -profile-loader.<p> - - <a name="opt_run-"><li><tt>-run-{int,jit,llc,cbe}</tt><br> - Whenever the test program is compiled, <tt>bugpoint</tt> should generate - code for it using the specified code generator. These options allow - you to choose the interpreter, the JIT compiler, the static native - code compiler, or the C backend, respectively.<p> -</ul> - -<h3>EXIT STATUS</h3> - -If <tt>bugpoint</tt> succeeds in finding a problem, it will exit with 0. -Otherwise, if an error occurs, it will exit with a non-zero value. - -<h3>SEE ALSO</h3> -<a href="opt.html"><tt>opt</tt></a>, -<a href="analyze.html"><tt>analyze</tt></a> - -<HR> -Maintained by the <a href="http://llvm.cs.uiuc.edu">LLVM Team</a>. -</body> -</html> |