diff --git a/docs/HowToSubmitABug.html b/docs/HowToSubmitABug.html deleted file mode 100644 index 39f83851293..00000000000 --- a/docs/HowToSubmitABug.html +++ /dev/null @@ -1,345 +0,0 @@ - - - - - How to submit an LLVM bug report - - - - -

- How to submit an LLVM bug report -

- - - - - -
-
    -
  1. Introduction - Got bugs?
    2. -
  2. Crashing Bugs -
    3. -
  3. Miscompilations
    4. -
  4. Incorrect code generation (JIT and LLC)
    5. -
-
-

Written by Chris Lattner and - Misha Brukman

-
-
- - -

- Introduction - Got bugs? -

- - -
- -

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 and fill out the form with the necessary details (note that you don't -need to pick a category, just use the "new-bugs" category if you're not sure). -The bug description should contain the following -information:

- - - -

Thanks for helping us make LLVM better!

- -
- - -

- Crashing Bugs -

- - -
- -

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:

- - - - -

- Front-end bugs -

- -
- -

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 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.

- -
- - -

- Compile-time optimization bugs -

- -
- -

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 way 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.

- -
- - -

- Code generator bugs -

- -
- -

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:

- -
    -
  1. llc foo.bc
    2. -
  2. llc foo.bc -relocation-model=pic
    3. -
  3. llc foo.bc -relocation-model=static
    4. -
- -

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):

- -
    -
  1. bugpoint -run-llc foo.bc
    2. -
  2. bugpoint -run-llc foo.bc --tool-args - -relocation-model=pic
    3. -
  3. bugpoint -run-llc foo.bc --tool-args - -relocation-model=static
    4. -
- -

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.

- -
- -
- - -

- Miscompilations -

- - -
- -

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. LLC or the JIT) -and optionally a series of LLVM passes to run. For example:

- -
-

-bugpoint -run-llc [... 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.

- -
- - -

- Incorrect code generation -

- - -
- -

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.

- -

To debug the JIT:

- -
-
-bugpoint -run-jit -output=[correct output file] [bitcode file]  \
-         --tool-args -- [arguments to pass to lli]              \
-         --args -- [program arguments]
-
-
- -

Similarly, to debug the LLC, one would run:

- -
-
-bugpoint -run-llc -output=[correct output file] [bitcode file]  \
-         --tool-args -- [arguments to pass to llc]              \
-         --args -- [program arguments]
-
-
- -

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
-make bugpoint-jit -

-
- -

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.

- -

To reproduce the error that bugpoint found, it is sufficient to do -the following:

- -
    - -

  1. Regenerate the shared object from the safe bitcode file:

    - -
    -

    -llc -march=c safe.bc -o safe.c
    -gcc -shared safe.c -o safe.so -

    -
    2. - -

  2. If debugging LLC, compile test bitcode native and link with the shared - object:

    - -
    -

    -llc test.bc -o test.s
    -gcc test.s safe.so -o test.llc
    -./test.llc [program options] -

    -
    3. - -

  3. If debugging the JIT, load the shared object and supply the test - bitcode:

    - -
    -

    lli -load=safe.so test.bc [program options]

    -
    4. - -
- -
- - -
-
- Valid CSS - Valid HTML 4.01 - - Chris Lattner
- The LLVM Compiler Infrastructure -
- Last modified: $Date$ -
- - - diff --git a/docs/HowToSubmitABug.rst b/docs/HowToSubmitABug.rst new file mode 100644 index 00000000000..ff2d649ce33 --- /dev/null +++ b/docs/HowToSubmitABug.rst @@ -0,0 +1,233 @@ +.. _how-to-submit-a-bug-report: + +================================ +How to submit an LLVM bug report +================================ + +.. sectionauthor:: Chris Lattner and Misha Brukman + +Introduction - Got bugs? +======================== + + +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 +`_ and fill out the form with the +necessary details (note that you don't need to pick a category, just use +the "new-bugs" category if you're not sure). The bug description should +contain the following information: + +* All information necessary to reproduce the problem. +* The reduced test-case that triggers the bug. +* The location where you obtained LLVM (if not from our Subversion + repository). + +Thanks for helping us make LLVM better! + +.. _crashes the compiler: + +Crashing Bugs +============= + +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: + +* ``-O0 -emit-llvm``: If ``llvm-gcc`` still crashes when passed these + options (which disable the optimizer and code generator), then the crash + is in the front-end. Jump ahead to the section on :ref:`front-end bugs + `. + +* ``-emit-llvm``: If ``llvm-gcc`` crashes with this option (which disables + the code generator), you found an optimizer bug. Jump ahead to + `compile-time optimization bugs`_. + +* Otherwise, you have a code generator crash. Jump ahead to `code + generator bugs`_. + +.. _front-end bug: +.. _front-end: + +Front-end bugs +-------------- + +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`` 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. + +.. _compile-time optimization bugs: + +Compile-time optimization bugs +------------------------------ + +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: + +.. code-block:: bash + + 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 way 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: + +.. code-block:: bash + + bugpoint foo.bc + +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``. + +.. _code generator bugs: + +Code generator bugs +------------------- + +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: + +#. ``llc foo.bc`` +#. ``llc foo.bc -relocation-model=pic`` +#. ``llc foo.bc -relocation-model=static`` + +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): + +#. ``bugpoint -run-llc foo.bc`` +#. ``bugpoint -run-llc foo.bc --tool-args -relocation-model=pic`` +#. ``bugpoint -run-llc foo.bc --tool-args -relocation-model=static`` + +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. + +.. _miscompiling: + +Miscompilations +=============== + +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 `valgrind +`_'s 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. LLC or the JIT) +and optionally a series of LLVM passes to run. For example: + +.. code-block:: bash + + bugpoint -run-llc [... 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. + +Incorrect code generation +========================= + +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. + +To debug the JIT: + +.. code-block:: bash + + bugpoint -run-jit -output=[correct output file] [bitcode file] \ + --tool-args -- [arguments to pass to lli] \ + --args -- [program arguments] + +Similarly, to debug the LLC, one would run: + +.. code-block:: bash + + bugpoint -run-llc -output=[correct output file] [bitcode file] \ + --tool-args -- [arguments to pass to llc] \ + --args -- [program arguments] + +**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: + +.. code-block:: bash + + cd llvm/test/../../program + make bugpoint-jit + +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. + +To reproduce the error that ``bugpoint`` found, it is sufficient to do +the following: + +#. Regenerate the shared object from the safe bitcode file: + + .. code-block:: bash + + llc -march=c safe.bc -o safe.c + gcc -shared safe.c -o safe.so + +#. If debugging LLC, compile test bitcode native and link with the shared + object: + + .. code-block:: bash + + llc test.bc -o test.s + gcc test.s safe.so -o test.llc + ./test.llc [program options] + +#. If debugging the JIT, load the shared object and supply the test + bitcode: + + .. code-block:: bash + + lli -load=safe.so test.bc [program options] diff --git a/docs/userguides.rst b/docs/userguides.rst index c7197ef6289..3a205141b40 100644 --- a/docs/userguides.rst +++ b/docs/userguides.rst @@ -15,6 +15,7 @@ User Guides Packaging HowToAddABuilder yaml2obj + HowToSubmitABug * `The LLVM Getting Started Guide `_ @@ -59,7 +60,7 @@ User Guides This describes new features, known bugs, and other limitations. -* `How to Submit A Bug Report `_ +* :ref:`how-to-submit-a-bug-report` Instructions for properly submitting information about any bugs you run into in the LLVM system.