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46 changes: 23 additions & 23 deletions llvm/docs/HowToSubmitABug.rst
Original file line number Diff line number Diff line change
Expand Up @@ -6,26 +6,26 @@ Introduction - Got bugs?
========================


If you're working with LLVM and run into a bug, we definitely want to know
If you're working with LLVM and encounter 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.

🔒 If you believe that the bug is security related, please follow :ref:`report-security-issue`. 🔒

Basically you have to do two things at a minimum. First, decide whether the
Basically, you have to do two things at a minimum. First, decide whether the
bug `crashes the compiler`_ 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
Once you have a reduced test case, go to `the LLVM Bug Tracking System
<https://github.com/llvm/llvm-project/issues>`_ and fill out the form with the
necessary details (note that you don't need to pick a label, just use 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 reduced test case that triggers the bug.
* The location where you obtained LLVM (if not from our Git
repository).

Expand All @@ -39,10 +39,10 @@ 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 Clang front-end or if it is one of
the LLVM libraries (e.g. the optimizer or code generator) that has
the LLVM libraries (e.g., the optimizer or code generator) that has
problems.

To figure out which component is crashing (the front-end, middle-end
To identify the crashing component (the front-end, middle-end
optimizer, or backend code generator), run the ``clang`` command line as you
were when the crash occurred, but with the following extra command line
options:
Expand All @@ -53,7 +53,7 @@ options:
<frontend-crash>`.

* ``-emit-llvm``: If ``clang`` crashes with this option (which disables
the code generator), you found a middle-end optimizer bug. Jump ahead to
the code generator), you've found a middle-end optimizer bug. Jump ahead to
:ref:`middle-end bugs <middleend-crash>`.

* Otherwise, you have a backend code generator crash. Jump ahead to :ref:`code
Expand Down Expand Up @@ -102,19 +102,19 @@ functions. Then run:
If this doesn't crash, please follow the instructions for a :ref:`front-end
bug <frontend-crash>`.

If this does crash, then you should be able to debug this with the following
If this does crash, then you can debug this with the following
:doc:`bugpoint <Bugpoint>` command:

.. code-block:: bash

bugpoint foo.bc -O3

Run this, then file a bug with the instructions and reduced .bc
Run this, then file a bug with the instructions and reduced ``.bc``
files that bugpoint emits.

If bugpoint doesn't reproduce the crash,
:doc:`llvm-reduce <CommandGuide/llvm-reduce>` is an alternative way to reduce
LLVM IR. Create a script that repros the crash and run:
LLVM IR. Create a script that reproduces the crash and run:

.. code-block:: bash

Expand All @@ -137,26 +137,26 @@ Backend code generator bugs
---------------------------

If you find a bug that crashes clang in the code generator, compile your
source file to a .bc file by passing "``-emit-llvm -c -o foo.bc``" to
clang (in addition to the options you already pass). Once your have
foo.bc, one of the following commands should fail:
source file to a ``.bc`` file by passing "``-emit-llvm -c -o foo.bc``" to
clang (in addition to the options you already pass). Once you 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 :ref:`front-end
bug<frontend-crash>`. If one of these do crash, you should be able to reduce
bug<frontend-crash>`. If one of these crashes, you should be able to reduce
this with one of the following :doc:`bugpoint <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
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.
the ``foo.bc`` file and the option that llc crashes with.

LTO bugs
---------------------------
Expand All @@ -174,7 +174,7 @@ in addition to your existing compilation options:
These options enable LTO and save temporary files generated during compilation
for later analysis.

On Windows, you should be using lld-link as the linker. Adjust your compilation
On Windows, use lld-link as the linker. Adjust your compilation
flags as follows:
* Add ``/lldsavetemps`` to the linker flags.
* When linking from the compiler driver, add ``/link /lldsavetemps`` in order to forward that flag to the linker.
Expand All @@ -199,7 +199,7 @@ command line (use the bc file corresponding to the command above that failed):

llvm-reduce --test reduce.sh a.out.0.2.internalize.bc

Example of reduce.sh script
Example of ``reduce.sh`` script

.. code-block:: bash

Expand All @@ -209,9 +209,9 @@ Example of reduce.sh script
path/to/not --crash path/to/opt "-passes=lto<O3>" $1 -o temp.bc 2> err.log
grep -q "It->second == &Insn" err.log

Here we have grepped the failed assert message.
Here we have grepped for the failed assert message.

Please run this, then file a bug with the instructions and reduced .bc file
Please run this, then file a bug with the instructions and reduced ``.bc`` file
that llvm-reduce emits.

.. _miscompiling:
Expand All @@ -221,16 +221,16 @@ Miscompilations

If clang 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.
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 is clean under various `sanitizers
<https://github.com/google/sanitizers>`_ (e.g. ``clang
<https://github.com/google/sanitizers>`_ (e.g., ``clang
-fsanitize=undefined,address``) and `valgrind <http://valgrind.org/>`_. Many
"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)
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
Expand Down
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