X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=docs%2FHowToSubmitABug.html;h=bdec1c091096f971ea6bbee5a035259cbdeea965;hb=08d012eba490c4906ec773c39db9f2a18a78c997;hp=d8db473390e3a3b5e8526c7c682ff95203a2acaf;hpb=0f6d7c0e20a67a0e6be2bff6d4d83cfeb149c17f;p=oota-llvm.git diff --git a/docs/HowToSubmitABug.html b/docs/HowToSubmitABug.html index d8db473390e..bdec1c09109 100644 --- a/docs/HowToSubmitABug.html +++ b/docs/HowToSubmitABug.html @@ -1,282 +1,355 @@ - -
How to submit an LLVM bug report | -
-
+
+
+
+ Written by Chris Lattner and
- Misha Brukman
-
-
+ If you're working with LLVM and run into a bug, we definitely want to know
+about it. This document describes what you can do to increase the odds of
+getting it fixed quickly. Basically you have to do two things at a minimum. First, decide whether the
+bug crashes the compiler (or an LLVM pass), or if the
+compiler is miscompiling the program (i.e., the
+compiler successfully produces an executable, but it doesn't run right). Based
+on
what type of bug it is, follow the instructions in the linked section to narrow
down the bug so that the person who fixes it will be able to find the problem
-more easily.
-
-Once you have a reduced test-case, go to
-
-the LLVM Bug Tracking System,
-
-select the catagory in which the bug falls, and fill out the form with the
-necessary details. The bug description should contain the following
-information:
+more easily. Once you have a reduced test-case, go to the LLVM Bug Tracking
+System and fill out the form with the necessary details (note that you don't
+need to pick a catagory, just use the "new-bugs" catagory if you're not sure).
+The bug description should contain the following
+information:
-Thanks for helping us make LLVM better!
+ Thanks for helping us make LLVM better!
+
+ More often than not, bugs in the compiler cause it to crash—often due
+to an assertion failure of some sort. The most important
+piece of the puzzle is to figure out if it is crashing in the GCC front-end
+or if it is one of the LLVM libraries (e.g. the optimizer or code generator)
+that has problems. To figure out which component is crashing (the front-end,
+optimizer or code generator), run the
+llvm-gcc command line as you were when the crash occurred, but
+with the following extra command line options:
+ If the problem is in the front-end, you should re-run the same
llvm-gcc command that resulted in the crash, but add the
--save-temps option. The compiler will crash again, but it
-will leave behind a foo.i file (containing preprocessed
-C source code) and possibly foo.s (containing LLVM
-assembly code), for each compiled foo.c file. Send us
-the foo.i file, along with a brief description of the
-error it caused.
+-save-temps option. The compiler will crash again, but it will leave
+behind a foo.i file (containing preprocessed C source code) and
+possibly foo.s for each
+compiled foo.c file. Send us the foo.i file,
+along with the options you passed to llvm-gcc, and a brief description of the
+error it caused. The delta tool helps to reduce the
+preprocessed file down to the smallest amount of code that still replicates the
+problem. You're encouraged to use delta to reduce the code to make the
+developers' lives easier. This website
+has instructions on the best way to use delta.
+
+ If you find that a bug crashes in the optimizer, compile your test-case to a
+.bc file by passing "-emit-llvm -O0 -c -o foo.bc".
+Then run:
+ opt -std-compile-opts -debug-pass=Arguments foo.bc
+ -disable-output This command should do two things: it should print out a list of passes, and
+then it should crash in the same was as llvm-gcc. If it doesn't crash, please
+follow the instructions for a front-end bug. If this does crash, then you should be able to debug this with the following
+bugpoint command:
+ bugpoint foo.bc <list of passes printed by
+opt>
+ Please run this, then file a bug with the instructions and reduced .bc files
+that bugpoint emits. If something goes wrong with bugpoint, please submit the
+"foo.bc" file and the list of passes printed by opt.
+
+
+ If you find a bug that crashes llvm-gcc in the code generator, compile your
+source file to a .bc file by passing "-emit-llvm -c -o foo.bc"
+to llvm-gcc (in addition to the options you already pass). Once your have
+foo.bc, one of the following commands should fail:
+ If none of these crash, please follow the instructions for a
+front-end bug. If one of these do crash, you should
+be able to reduce this with one of the following bugpoint command lines (use
+the one corresponding to the command above that failed):
+
+ Please run this, then file a bug with the instructions and reduced .bc file
+that bugpoint emits. If something goes wrong with bugpoint, please submit the
+"foo.bc" file and the option that llc crashes with.
+ If llvm-gcc successfully produces an executable, but that executable doesn't
+run right, this is either a bug in the code or a bug in the
+compiler. The first thing to check is to make sure it is not using undefined
+behavior (e.g. reading a variable before it is defined). In particular, check
+to see if the program valgrinds clean,
+passes purify, or some other memory checker tool. Many of the "LLVM bugs" that
+we have chased down ended up being bugs in the program being compiled, not
+ LLVM. Once you determine that the program itself is not buggy, you should choose
+which code generator you wish to compile the program with (e.g. C backend, the
+JIT, or LLC) and optionally a series of LLVM passes to run. For example:
+bugpoint -run-cbe [... optzn passes ...] file-to-test.bc --args -- [program arguments] bugpoint will try to narrow down your list of passes to the one pass
+that causes an error, and simplify the bitcode file as much as it can to assist
you. It will print a message letting you know how to reproduce the resulting
-error.
+error. Similarly to debugging incorrect compilation by mis-behaving passes, you can
debug incorrect code generation by either LLC or the JIT, using
bugpoint. The process bugpoint follows in this case is to try
to narrow the code down to a function that is miscompiled by one or the other
method, but since for correctness, the entire program must be run,
bugpoint will compile the code it deems to not be affected with the C
-Backend, and then link in the shared object it generates.
+Backend, and then link in the shared object it generates. To debug the JIT: Similarly, to debug the LLC, one would run: Special note: if you are debugging MultiSource or SPEC tests that
+already exist in the llvm/test hierarchy, there is an easier way to
+debug the JIT, LLC, and CBE, using the pre-written Makefile targets, which
+will pass the program options specified in the Makefiles:
+cd llvm/test/../../program At the end of a successful bugpoint run, you will be presented
+with two bitcode files: a safe file which can be compiled with the C
backend and the test file which either LLC or the JIT
-mis-codegenerates, and thus causes the error.
+mis-codegenerates, and thus causes the error. To reproduce the error that bugpoint found, it is sufficient to do
+the following:
- If debugging the JIT, load the shared object and supply the test bytecode: Regenerate the shared object from the safe bitcode file:
+llc -march=c safe.bc -o safe.c If debugging LLC, compile test bitcode native and link with the shared
+ object:
+llc test.bc -o test.s -f If debugging the JIT, load the shared object and supply the test
+ bitcode: lli -load=safe.so test.bc [program options] |