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| author | Chris Lattner <sabre@nondot.org> | 2002-09-06 02:02:58 +0000 |
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| committer | Chris Lattner <sabre@nondot.org> | 2002-09-06 02:02:58 +0000 |
| commit | 480e2efb2e3638cd202551ed53fb456d6179d5e0 (patch) | |
| tree | bcc937456694e6d2fe514f0be330d2bba151364a /docs/WritingAnLLVMPass.html | |
| parent | 68f716190baa08675793adba428605797eb658a4 (diff) | |
| download | llvm-480e2efb2e3638cd202551ed53fb456d6179d5e0.tar.gz llvm-480e2efb2e3638cd202551ed53fb456d6179d5e0.tar.bz2 llvm-480e2efb2e3638cd202551ed53fb456d6179d5e0.tar.xz | |
* Remove notes at the top of the file
* Add information about how to debug a dynamically loaded pass.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@3583 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'docs/WritingAnLLVMPass.html')
| -rw-r--r-- | docs/WritingAnLLVMPass.html | 123 |
1 files changed, 93 insertions, 30 deletions
diff --git a/docs/WritingAnLLVMPass.html b/docs/WritingAnLLVMPass.html index 3e2f167ccb..d1cf63cae8 100644 --- a/docs/WritingAnLLVMPass.html +++ b/docs/WritingAnLLVMPass.html @@ -1,34 +1,6 @@ <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html><head><title>Writing an LLVM Pass</title></head> -<!-- -I. General Structure of an LLVM Program - -I.1 "What is a 'Value'?": Value & User class -I.2 Type & Derived Types -I.3 GlobalVariable, Function -I.4 BasicBlock -I.5 Instruction & Subclasses -1.6 Argument -1.7 Constants - -III. Useful things to know about the LLVM source base: - -III.1 Useful links that introduce the STL -III.2 isa<>, cast<>, dyn_cast<> -III.3 Makefiles, useful options -III.4 How to use opt & analyze to debug stuff -III.5 How to write a regression test -III.6 DEBUG() and Statistics (-debug & -stats) -III.7 The -time-passes option -III.8 ... more as needed ... - -I think that writing Section #1 would be very helpful and that's the most -stable portion of the sourcebase. #3 can be started on, but will probably -just grow as time goes on. - ---> - <body bgcolor=white> <table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0> @@ -80,6 +52,11 @@ just grow as time goes on. <ul> <li><a href="#releaseMemory">The <tt>releaseMemory</tt> method</a> </ul> + <li><a href="#debughints">Using GDB with dynamically loaded passes</a> + <ul> + <li><a href="#breakpoint">Setting a breakpoint in your pass + <li><a href="#debugmisc">Miscellaneous Problems + </ul> <li><a href="#future">Future extensions planned</a> <ul> <li><a href="#SMP">Multithreaded LLVM</a> @@ -1028,6 +1005,92 @@ class, before the next call of <tt>run*</tt> in your pass.<p> <!-- *********************************************************************** --> </ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0> <tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b> +<a name="debughints">Using GDB with dynamically loaded passes +</b></font></td></tr></table><ul> +<!-- *********************************************************************** --> + +Unfortunately, using GDB with dynamically loaded passes is not as easy as it +should be. First of all, you can't set a breakpoint in a shared object that has +not been loaded yet, and second of all there are problems with inlined functions +in shared objects. Here are some suggestions to debugging your pass with +GDB.<p> + +For sake of discussion, I'm going to assume that you are debugging a +transformation invoked by <tt>opt</tt>, although nothing described here depends +on that.<p> + +<!-- _______________________________________________________________________ --> +</ul><h4><a name="breakpoint"><hr size=0>Setting a breakpoint in your pass</h4><ul> + +First thing you do is start <tt>gdb</tt> on the <tt>opt</tt> process:<p> + +<pre> +$ <b>gdb opt</b> +GNU gdb 5.0 +Copyright 2000 Free Software Foundation, Inc. +GDB is free software, covered by the GNU General Public License, and you are +welcome to change it and/or distribute copies of it under certain conditions. +Type "show copying" to see the conditions. +There is absolutely no warranty for GDB. Type "show warranty" for details. +This GDB was configured as "sparc-sun-solaris2.6"... +(gdb) +</pre><p> + +Note that <tt>opt</tt> has a lot of debugging information in it, so it takes +time to load. Be patient. Since we cannot set a breakpoint in our pass yet +(the shared object isn't loaded until runtime), we must execute the process, and +have it stop before it invokes our pass, but after it has loaded the shared +object. The most foolproof way of doing this is to set a breakpoint in +<tt>PassManager::run</tt> and then run the process with the arguments you +want:<p> + +<pre> +(gdb) <b>break PassManager::run</b> +Breakpoint 1 at 0x2413bc: file Pass.cpp, line 70. +(gdb) <b>run test.bc -load /shared/lattner/cvs/llvm/lib/Debug/[libname].so -[passoption]</b> +Starting program: /shared/lattner/cvs/llvm/tools/Debug/opt test.bc + -load /shared/lattner/cvs/llvm/lib/Debug/[libname].so -[passoption] +Breakpoint 1, PassManager::run (this=0xffbef174, M=@0x70b298) at Pass.cpp:70 +70 bool PassManager::run(Module &M) { return PM->run(M); } +(gdb) +</pre></p> + +Once the <tt>opt</tt> stops in the <tt>PassManager::run</tt> method you are now +free to set breakpoints in your pass so that you can trace through execution or +do other standard debugging stuff.<p> + + +<!-- _______________________________________________________________________ --> +</ul><h4><a name="debugmisc"><hr size=0>Miscellaneous Problems</h4><ul> + +Once you have the basics down, there are a couple of problems that GDB has, some +with solutions, some without.<p> + +<ul> +<li>Inline functions have bogus stack information. In general, GDB does a +pretty good job getting stack traces and stepping through inline functions. +When a pass is dynamically loaded however, it somehow completely loses this +capability. The only solution I know of is to de-inline a function (move it +from the body of a class to a .cpp file).<p> + +<li>Restarting the program breaks breakpoints. After following the information +above, you have succeeded in getting some breakpoints planted in your pass. Nex +thing you know, you restart the program (i.e., you type '<tt>run</tt>' again), +and you start getting errors about breakpoints being unsettable. The only way I +have found to "fix" this problem is to <tt>delete</tt> the breakpoints that are +already set in your pass, run the program, and re-set the breakpoints once +execution stops in <tt>PassManager::run</tt>.<p> + +</ul> + +Hopefully these tips will help with common case debugging situations. If you'd +like to contribute some tips of your own, just contact <a +href="mailto:sabre@nondot.org">Chris</a>.<p> + + +<!-- *********************************************************************** --> +</ul><table width="100%" bgcolor="#330077" border=0 cellpadding=4 cellspacing=0> +<tr><td align=center><font color="#EEEEFF" size=+2 face="Georgia,Palatino"><b> <a name="future">Future extensions planned </b></font></td></tr></table><ul> <!-- *********************************************************************** --> @@ -1098,9 +1161,9 @@ href="#Pass"><tt>Pass</tt></a>, only the other way around.<p> <!-- *********************************************************************** --> <hr><font size-1> -<address><a href="mailto:sabre@nondot.org">Christopher Lattner</a></address> +<address><a href="mailto:sabre@nondot.org">Chris Lattner</a></address> <!-- Created: Tue Aug 6 15:00:33 CDT 2002 --> <!-- hhmts start --> -Last modified: Thu Aug 22 14:19:43 CDT 2002 +Last modified: Thu Sep 5 15:06:01 CDT 2002 <!-- hhmts end --> </font></body></html> |