From: Misha Brukman Date: Thu, 9 Dec 2004 20:26:20 +0000 (+0000) Subject: Convert from being a copy of the man page to a full-fledged document. X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=d97cb4608c205ab31dbb758923ed2bb0e9dbbba7;p=oota-llvm.git Convert from being a copy of the man page to a full-fledged document. This doc keeps all the descriptive info from the man page, but not the options. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@18719 91177308-0d34-0410-b5e6-96231b3b80d8 --- diff --git a/docs/Bugpoint.html b/docs/Bugpoint.html index af6155e8b66..81dce4f42a5 100644 --- a/docs/Bugpoint.html +++ b/docs/Bugpoint.html @@ -1,41 +1,63 @@ - + - - LLVM: bugpoint tool + LLVM bugpoint tool: design and usage - - - - -

LLVM: bugpoint tool

-
+
+ LLVM bugpoint tool: design and usage +
+ + + +
+

Written by Chris Lattner

+
+ + +
+Description +
+ -

NAME

-bugpoint +
-

SYNOPSIS

-bugpoint [options] [input LLVM ll/bc files] [LLVM passes] --args <program arguments>... +

bugpoint 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 gccas 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.

- -

DESCRIPTION

+

For detailed case scenarios, such as debugging gccas, +gccld, or one of the LLVM code generators, see How To Submit a Bug Report document.

-The bugpoint 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 gccas 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.

+

- -

Design Philosophy

+ +
+Design Philosophy +
+ -bugpoint is designed to be a useful tool without requiring any +
+ +

bugpoint 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 @@ -44,47 +66,57 @@ 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 bugpoint is generally very quick unless debugging a miscompilation where each test of the program (which requires -executing it) takes a long time.

- - -

Automatic Debugger Selection

- -bugpoint reads each .bc or .ll 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), -bugpoint starts the crash debugger.

- -Otherwise, if the -output option was not -specified, bugpoint runs the test program with the C backend (which is -assumed to generate good code) to generate a reference output. Once -bugpoint has a reference output for the test program, it tries -executing it with the selected code generator. If the -selected code generator crashes, bugpoint starts the crash debugger 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 code generator debugger.

- -Finally, if the output of the selected code generator matches the reference +executing it) takes a long time.

+ +
+ + +
+ Automatic Debugger Selection +
+ +
+ +

bugpoint reads each .bc or .ll 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), bugpoint starts +the crash debugger.

+ +

Otherwise, if the -output option was not specified, +bugpoint runs the test program with the C backend (which is assumed to +generate good code) to generate a reference output. Once bugpoint has +a reference output for the test program, it tries executing it with the +selected code generator. If the selected code generator crashes, +bugpoint starts the crash debugger 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 code generator debugger.

+ +

Finally, if the output of the selected code generator matches the reference output, bugpoint 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 miscompilation -debugger. Otherwise, there is no problem bugpoint can debug.

+enters the miscompilation debugger. +Otherwise, there is no problem bugpoint can debug.

+ +
- -

Crash debugger

+ +
+ Crash debugger +
-If an optimizer or code generator crashes, bugpoint will try as hard as -it can to reduce the list of passes (for optimizer crashes) and the size of the -test program. First, bugpoint figures out which combination of +
+ +

If an optimizer or code generator crashes, bugpoint will try as hard +as it can to reduce the list of passes (for optimizer crashes) and the size of +the test program. First, bugpoint figures out which combination of optimizer passes triggers the bug. This is useful when debugging a problem -exposed by gccas, for example, because it runs over 38 passes.

+exposed by gccas, for example, because it runs over 38 passes.

-Next, bugpoint tries removing functions from the test program, to +

Next, bugpoint 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 @@ -92,38 +124,55 @@ flow graph, to reduce the size of the function as much as possible. Finally, bugpoint deletes any individual LLVM instructions whose absence does not eliminate the failure. At the end, bugpoint should tell you what passes crash, give you a bytecode file, and give you instructions on how to -reproduce the failure with opt, analyze, or llc.

+reproduce the failure with opt, analyze, or llc.

+ +
- -

Code generator debugger

+ +
+ Code generator debugger +
+ +

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 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.

- - -

Miscompilation debugger

- -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.

- - -

Advice for using bugpoint

+is being miscompiled by the selected 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.

+ +
+ + +
+ Miscompilation debugger +
+ +
+ +

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.

+ +
+ + +
+ Advice for using bugpoint +
+ + +
bugpoint can be a remarkably useful tool, but it sometimes works in non-obvious ways. Here are some hints and tips:

@@ -131,10 +180,10 @@ non-obvious ways. Here are some hints and tips:

  1. In the code generator and miscompilation debuggers, bugpoint only works with programs that have deterministic output. Thus, if the program - outputs argv[0], the date, time, or any other "random" data, bugpoint 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. + outputs argv[0], the date, time, or any other "random" data, + bugpoint 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.
  2. In the code generator and miscompilation debuggers, debugging will go faster if you manually modify the program or its inputs to reduce the @@ -143,15 +192,19 @@ non-obvious ways. Here are some hints and tips:

  3. bugpoint is extremely useful when working on a new optimization: it helps track down regressions quickly. To avoid having to relink bugpoint every time you change your optimization however, have - bugpoint dynamically load your optimization with the -load option. + bugpoint dynamically load your optimization with the + -load option. + +

  4. bugpoint 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 run:

    -
  5. bugpoint 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:
    - bugpoint ..... |& tee bugpoint.log -
    to get a copy of bugpoint's output in the file - bugpoint.log, as well as on your terminal. +
    +

    bugpoint ... |& tee bugpoint.log

    +
    + +

    to get a copy of bugpoint's output in the file + bugpoint.log, as well as on your terminal.

  6. bugpoint cannot debug problems with the LLVM linker. If bugpoint crashes before you see its "All input ok" message, @@ -165,89 +218,21 @@ non-obvious ways. Here are some hints and tips:

-

OPTIONS

+
- + -

EXIT STATUS

+
+
+ Valid CSS! + Valid HTML 4.01! -If bugpoint succeeds in finding a problem, it will exit with 0. -Otherwise, if an error occurs, it will exit with a non-zero value. + Chris Lattner
+ LLVM Compiler Infrastructure
+ Last modified: $Date$ +
-
-Maintained by the LLVM Team.