llvm/docs/TestingGuide.rst - toolchain/llvm-project - Gitiles

 =================================
 LLVM Testing Infrastructure Guide
 =================================

 Written by John T. Criswell, Daniel Dunbar, Reid Spencer, and Tanya
 Lattner

 .. contents::
    :local:

 .. toctree::
    :hidden:

    TestSuiteMakefileGuide

 Overview
 ========

 This document is the reference manual for the LLVM testing
 infrastructure. It documents the structure of the LLVM testing
 infrastructure, the tools needed to use it, and how to add and run
 tests.

 Requirements
 ============

 In order to use the LLVM testing infrastructure, you will need all of
 the software required to build LLVM, as well as
 `Python <http://python.org>`_ 2.4 or later.

 LLVM testing infrastructure organization
 ========================================

 The LLVM testing infrastructure contains two major categories of tests:
 regression tests and whole programs. The regression tests are contained
 inside the LLVM repository itself under ``llvm/test`` and are expected
 to always pass -- they should be run before every commit.

 The whole programs tests are referred to as the "LLVM test suite" (or
 "test-suite") and are in the ``test-suite`` module in subversion. For
 historical reasons, these tests are also referred to as the "nightly
 tests" in places, which is less ambiguous than "test-suite" and remains
 in use although we run them much more often than nightly.

 Regression tests
 ----------------

 The regression tests are small pieces of code that test a specific
 feature of LLVM or trigger a specific bug in LLVM. The language they are
 written in depends on the part of LLVM being tested. These tests are driven by
 the :doc:`Lit <CommandGuide/lit>` testing tool (which is part of LLVM), and
 are located in the ``llvm/test`` directory.

 Typically when a bug is found in LLVM, a regression test containing just
 enough code to reproduce the problem should be written and placed
 somewhere underneath this directory. For example, it can be a small
 piece of LLVM IR distilled from an actual application or benchmark.

 ``test-suite``
 --------------

 The test suite contains whole programs, which are pieces of code which
 can be compiled and linked into a stand-alone program that can be
 executed. These programs are generally written in high level languages
 such as C or C++.

 These programs are compiled using a user specified compiler and set of
 flags, and then executed to capture the program output and timing
 information. The output of these programs is compared to a reference
 output to ensure that the program is being compiled correctly.

 In addition to compiling and executing programs, whole program tests
 serve as a way of benchmarking LLVM performance, both in terms of the
 efficiency of the programs generated as well as the speed with which
 LLVM compiles, optimizes, and generates code.

 The test-suite is located in the ``test-suite`` Subversion module.

 Debugging Information tests
 ---------------------------

 The test suite contains tests to check quality of debugging information.
 The test are written in C based languages or in LLVM assembly language.

 These tests are compiled and run under a debugger. The debugger output
 is checked to validate of debugging information. See README.txt in the
 test suite for more information . This test suite is located in the
 ``debuginfo-tests`` Subversion module.

 Quick start
 ===========

 The tests are located in two separate Subversion modules. The
 regressions tests are in the main "llvm" module under the directory
 ``llvm/test`` (so you get these tests for free with the main LLVM tree).
 Use ``make check-all`` to run the regression tests after building LLVM.

 The more comprehensive test suite that includes whole programs in C and C++
 is in the ``test-suite`` module. See :ref:`test-suite Quickstart
 <test-suite-quickstart>` for more information on running these tests.

 Regression tests
 ----------------

 To run all of the LLVM regression tests, use the master Makefile in the
 ``llvm/test`` directory. LLVM Makefiles require GNU Make (read the :doc:`LLVM
 Makefile Guide <MakefileGuide>` for more details):

 .. code-block:: bash

     % make -C llvm/test

 or:

 .. code-block:: bash

     % make check

 If you have `Clang <http://clang.llvm.org/>`_ checked out and built, you
 can run the LLVM and Clang tests simultaneously using:

 .. code-block:: bash

     % make check-all

 To run the tests with Valgrind (Memcheck by default), just append
 ``VG=1`` to the commands above, e.g.:

 .. code-block:: bash

     % make check VG=1

 To run individual tests or subsets of tests, you can use the ``llvm-lit``
 script which is built as part of LLVM. For example, to run the
 ``Integer/BitPacked.ll`` test by itself you can run:

 .. code-block:: bash

     % llvm-lit ~/llvm/test/Integer/BitPacked.ll

 or to run all of the ARM CodeGen tests:

 .. code-block:: bash

     % llvm-lit ~/llvm/test/CodeGen/ARM

 For more information on using the :program:`lit` tool, see ``llvm-lit --help``
 or the :doc:`lit man page <CommandGuide/lit>`.

 Debugging Information tests
 ---------------------------

 To run debugging information tests simply checkout the tests inside
 clang/test directory.

 .. code-block:: bash

     % cd clang/test
     % svn co http://llvm.org/svn/llvm-project/debuginfo-tests/trunk debuginfo-tests

 These tests are already set up to run as part of clang regression tests.

 Regression test structure
 =========================

 The LLVM regression tests are driven by :program:`lit` and are located in the
 ``llvm/test`` directory.

 This directory contains a large array of small tests that exercise
 various features of LLVM and to ensure that regressions do not occur.
 The directory is broken into several sub-directories, each focused on a
 particular area of LLVM.

 Writing new regression tests
 ----------------------------

 The regression test structure is very simple, but does require some
 information to be set. This information is gathered via ``configure``
 and is written to a file, ``test/lit.site.cfg`` in the build directory.
 The ``llvm/test`` Makefile does this work for you.

 In order for the regression tests to work, each directory of tests must
 have a ``lit.local.cfg`` file. :program:`lit` looks for this file to determine
 how to run the tests. This file is just Python code and thus is very
 flexible, but we've standardized it for the LLVM regression tests. If
 you're adding a directory of tests, just copy ``lit.local.cfg`` from
 another directory to get running. The standard ``lit.local.cfg`` simply
 specifies which files to look in for tests. Any directory that contains
 only directories does not need the ``lit.local.cfg`` file. Read the :doc:`Lit
 documentation <CommandGuide/lit>` for more information.

 Each test file must contain lines starting with "RUN:" that tell :program:`lit`
 how to run it. If there are no RUN lines, :program:`lit` will issue an error
 while running a test.

 RUN lines are specified in the comments of the test program using the
 keyword ``RUN`` followed by a colon, and lastly the command (pipeline)
 to execute. Together, these lines form the "script" that :program:`lit`
 executes to run the test case. The syntax of the RUN lines is similar to a
 shell's syntax for pipelines including I/O redirection and variable
 substitution. However, even though these lines may *look* like a shell
 script, they are not. RUN lines are interpreted by :program:`lit`.
 Consequently, the syntax differs from shell in a few ways. You can specify
 as many RUN lines as needed.

 :program:`lit` performs substitution on each RUN line to replace LLVM tool names
 with the full paths to the executable built for each tool (in
 ``$(LLVM_OBJ_ROOT)/$(BuildMode)/bin)``. This ensures that :program:`lit` does
 not invoke any stray LLVM tools in the user's path during testing.

 Each RUN line is executed on its own, distinct from other lines unless
 its last character is ``\``. This continuation character causes the RUN
 line to be concatenated with the next one. In this way you can build up
 long pipelines of commands without making huge line lengths. The lines
 ending in ``\`` are concatenated until a RUN line that doesn't end in
 ``\`` is found. This concatenated set of RUN lines then constitutes one
 execution. :program:`lit` will substitute variables and arrange for the pipeline
 to be executed. If any process in the pipeline fails, the entire line (and
 test case) fails too.

 Below is an example of legal RUN lines in a ``.ll`` file:

 .. code-block:: llvm

     ; RUN: llvm-as < %s | llvm-dis > %t1
     ; RUN: llvm-dis < %s.bc-13 > %t2
     ; RUN: diff %t1 %t2

 As with a Unix shell, the RUN lines permit pipelines and I/O
 redirection to be used. However, the usage is slightly different than
 for Bash. In general, it's useful to read the code of other tests to figure out
 what you can use in yours. The major differences are:

 -  You can't do ``2>&1``. That will cause :program:`lit` to write to a file
    named ``&1``. Usually this is done to get stderr to go through a pipe. You
    can do that with ``|&`` so replace this idiom:
    ``... 2>&1 | grep`` with ``... |& grep``
 -  You can only redirect to a file, not to another descriptor and not
    from a here document.

 There are some quoting rules that you must pay attention to when writing
 your RUN lines. In general nothing needs to be quoted. :program:`lit` won't
 strip off any quote characters so they will get passed to the invoked program.
 For example:

 .. code-block:: bash

     ... | grep 'find this string'

 This will fail because the ``'`` characters are passed to ``grep``. This would
 make ``grep`` to look for ``'find`` in the files ``this`` and
 ``string'``. To avoid this use curly braces to tell :program:`lit` that it
 should treat everything enclosed as one value. So our example would become:

 .. code-block:: bash

     ... | grep {find this string}

 In general, you should strive to keep your RUN lines as simple as possible,
 using them only to run tools that generate the output you can then examine. The
 recommended way to examine output to figure out if the test passes it using the
 :doc:`FileCheck tool <CommandGuide/FileCheck>`. The usage of ``grep`` in RUN
 lines is discouraged.

 The FileCheck utility
 ---------------------

 A powerful feature of the RUN lines is that it allows any arbitrary
 commands to be executed as part of the test harness. While standard
 (portable) unix tools like ``grep`` work fine on run lines, as you see
 above, there are a lot of caveats due to interaction with shell syntax,
 and we want to make sure the run lines are portable to a wide range of
 systems. Another major problem is that ``grep`` is not very good at checking
 to verify that the output of a tools contains a series of different
 output in a specific order. The :program:`FileCheck` tool was designed to
 help with these problems.

 :program:`FileCheck` is designed to read a file to check from standard input,
 and the set of things to verify from a file specified as a command line
 argument. :program:`FileCheck` is described in :doc:`the FileCheck man page
 <CommandGuide/FileCheck>`.

 Variables and substitutions
 ---------------------------

 With a RUN line there are a number of substitutions that are permitted.
 To make a substitution just write the variable's name preceded by a ``$``.
 Additionally, for compatibility reasons with previous versions of the
 test library, certain names can be accessed with an alternate syntax: a
 % prefix. These alternates are deprecated and may go away in a future
 version.

 Here are the available variable names. The alternate syntax is listed in
 parentheses.

 ``$test`` (``%s``)
    The full path to the test case's source. This is suitable for passing on
    the command line as the input to an LLVM tool.

 ``%(line)``, ``%(line+<number>)``, ``%(line-<number>)``
    The number of the line where this variable is used, with an optional
    integer offset. This can be used in tests with multiple RUN lines,
    which reference test file's line numbers.

 ``$srcdir``
    The source directory from where the ``make check`` was run.

 ``objdir``
    The object directory that corresponds to the ``$srcdir``.

 ``subdir``
    A partial path from the ``test`` directory that contains the
    sub-directory that contains the test source being executed.

 ``srcroot``
    The root directory of the LLVM src tree.

 ``objroot``
    The root directory of the LLVM object tree. This could be the same as
    the srcroot.

 ``path``
    The path to the directory that contains the test case source. This is
    for locating any supporting files that are not generated by the test,
    but used by the test.

 ``tmp``
    The path to a temporary file name that could be used for this test case.
    The file name won't conflict with other test cases. You can append to it
    if you need multiple temporaries. This is useful as the destination of
    some redirected output.

 ``target_triplet`` (``%target_triplet``)
    The target triplet that corresponds to the current host machine (the one
    running the test cases). This should probably be called "host".

 ``link`` (``%link``)
    This full link command used to link LLVM executables. This has all the
    configured ``-I``, ``-L`` and ``-l`` options.

 ``shlibext`` (``%shlibext``)
    The suffix for the host platforms shared library (DLL) files. This
    includes the period as the first character.

 To add more variables, look at ``test/lit.cfg``.

 Other Features
 --------------

 To make RUN line writing easier, there are several helper scripts and programs
 in the ``llvm/test/Scripts`` directory. This directory is in the PATH
 when running tests, so you can just call these scripts using their name.
 For example:

 ``ignore``
    This script runs its arguments and then always returns 0. This is useful
    in cases where the test needs to cause a tool to generate an error (e.g.
    to check the error output). However, any program in a pipeline that
    returns a non-zero result will cause the test to fail.  This script
    overcomes that issue and nicely documents that the test case is
    purposefully ignoring the result code of the tool
 ``not``
    This script runs its arguments and then inverts the result code from it.
    Zero result codes become 1. Non-zero result codes become 0.

 Sometimes it is necessary to mark a test case as "expected fail" or
 XFAIL. You can easily mark a test as XFAIL just by including ``XFAIL:``
 on a line near the top of the file. This signals that the test case
 should succeed if the test fails. Such test cases are counted separately
 by the testing tool. To specify an expected fail, use the XFAIL keyword
 in the comments of the test program followed by a colon and one or more
 failure patterns. Each failure pattern can be either ``*`` (to specify
 fail everywhere), or a part of a target triple (indicating the test
 should fail on that platform), or the name of a configurable feature
 (for example, ``loadable_module``). If there is a match, the test is
 expected to fail. If not, the test is expected to succeed. To XFAIL
 everywhere just specify ``XFAIL: *``. Here is an example of an ``XFAIL``
 line:

 .. code-block:: llvm

     ; XFAIL: darwin,sun

 To make the output more useful, :program:`lit` will scan
 the lines of the test case for ones that contain a pattern that matches
 ``PR[0-9]+``. This is the syntax for specifying a PR (Problem Report) number
 that is related to the test case. The number after "PR" specifies the
 LLVM bugzilla number. When a PR number is specified, it will be used in
 the pass/fail reporting. This is useful to quickly get some context when
 a test fails.

 Finally, any line that contains "END." will cause the special
 interpretation of lines to terminate. This is generally done right after
 the last RUN: line. This has two side effects:

 (a) it prevents special interpretation of lines that are part of the test
     program, not the instructions to the test case, and

 (b) it speeds things up for really big test cases by avoiding
     interpretation of the remainder of the file.

 ``test-suite`` Overview
 =======================

 The ``test-suite`` module contains a number of programs that can be
 compiled and executed. The ``test-suite`` includes reference outputs for
 all of the programs, so that the output of the executed program can be
 checked for correctness.

 ``test-suite`` tests are divided into three types of tests: MultiSource,
 SingleSource, and External.

 -  ``test-suite/SingleSource``

    The SingleSource directory contains test programs that are only a
    single source file in size. These are usually small benchmark
    programs or small programs that calculate a particular value. Several
    such programs are grouped together in each directory.

 -  ``test-suite/MultiSource``

    The MultiSource directory contains subdirectories which contain
    entire programs with multiple source files. Large benchmarks and
    whole applications go here.

 -  ``test-suite/External``

    The External directory contains Makefiles for building code that is
    external to (i.e., not distributed with) LLVM. The most prominent
    members of this directory are the SPEC 95 and SPEC 2000 benchmark
    suites. The ``External`` directory does not contain these actual
    tests, but only the Makefiles that know how to properly compile these
    programs from somewhere else. When using ``LNT``, use the
    ``--test-externals`` option to include these tests in the results.

 .. _test-suite-quickstart:

 ``test-suite`` Quickstart
 -------------------------

 The modern way of running the ``test-suite`` is focused on testing and
 benchmarking complete compilers using the
 `LNT <http://llvm.org/docs/lnt>`_ testing infrastructure.

 For more information on using LNT to execute the ``test-suite``, please
 see the `LNT Quickstart <http://llvm.org/docs/lnt/quickstart.html>`_
 documentation.

 ``test-suite`` Makefiles
 ------------------------

 Historically, the ``test-suite`` was executed using a complicated setup
 of Makefiles. The LNT based approach above is recommended for most
 users, but there are some testing scenarios which are not supported by
 the LNT approach. In addition, LNT currently uses the Makefile setup
 under the covers and so developers who are interested in how LNT works
 under the hood may want to understand the Makefile based setup.

 For more information on the ``test-suite`` Makefile setup, please see
 the :doc:`Test Suite Makefile Guide <TestSuiteMakefileGuide>`.
	=================================
	LLVM Testing Infrastructure Guide
	=================================

	Written by John T. Criswell, Daniel Dunbar, Reid Spencer, and Tanya
	Lattner

	.. contents::
	:local:

	.. toctree::
	:hidden:

	TestSuiteMakefileGuide

	Overview
	========

	This document is the reference manual for the LLVM testing
	infrastructure. It documents the structure of the LLVM testing
	infrastructure, the tools needed to use it, and how to add and run
	tests.

	Requirements
	============

	In order to use the LLVM testing infrastructure, you will need all of
	the software required to build LLVM, as well as
	`Python <http://python.org>`_ 2.4 or later.

	LLVM testing infrastructure organization
	========================================

	The LLVM testing infrastructure contains two major categories of tests:
	regression tests and whole programs. The regression tests are contained
	inside the LLVM repository itself under ``llvm/test`` and are expected
	to always pass -- they should be run before every commit.

	The whole programs tests are referred to as the "LLVM test suite" (or
	"test-suite") and are in the ``test-suite`` module in subversion. For
	historical reasons, these tests are also referred to as the "nightly
	tests" in places, which is less ambiguous than "test-suite" and remains
	in use although we run them much more often than nightly.

	Regression tests
	----------------

	The regression tests are small pieces of code that test a specific
	feature of LLVM or trigger a specific bug in LLVM. The language they are
	written in depends on the part of LLVM being tested. These tests are driven by
	the :doc:`Lit <CommandGuide/lit>` testing tool (which is part of LLVM), and
	are located in the ``llvm/test`` directory.

	Typically when a bug is found in LLVM, a regression test containing just
	enough code to reproduce the problem should be written and placed
	somewhere underneath this directory. For example, it can be a small
	piece of LLVM IR distilled from an actual application or benchmark.

	``test-suite``
	--------------

	The test suite contains whole programs, which are pieces of code which
	can be compiled and linked into a stand-alone program that can be
	executed. These programs are generally written in high level languages
	such as C or C++.

	These programs are compiled using a user specified compiler and set of
	flags, and then executed to capture the program output and timing
	information. The output of these programs is compared to a reference
	output to ensure that the program is being compiled correctly.

	In addition to compiling and executing programs, whole program tests
	serve as a way of benchmarking LLVM performance, both in terms of the
	efficiency of the programs generated as well as the speed with which
	LLVM compiles, optimizes, and generates code.

	The test-suite is located in the ``test-suite`` Subversion module.

	Debugging Information tests
	---------------------------

	The test suite contains tests to check quality of debugging information.
	The test are written in C based languages or in LLVM assembly language.

	These tests are compiled and run under a debugger. The debugger output
	is checked to validate of debugging information. See README.txt in the
	test suite for more information . This test suite is located in the
	``debuginfo-tests`` Subversion module.

	Quick start
	===========

	The tests are located in two separate Subversion modules. The
	regressions tests are in the main "llvm" module under the directory
	``llvm/test`` (so you get these tests for free with the main LLVM tree).
	Use ``make check-all`` to run the regression tests after building LLVM.

	The more comprehensive test suite that includes whole programs in C and C++
	is in the ``test-suite`` module. See :ref:`test-suite Quickstart
	<test-suite-quickstart>` for more information on running these tests.

	Regression tests
	----------------

	To run all of the LLVM regression tests, use the master Makefile in the
	``llvm/test`` directory. LLVM Makefiles require GNU Make (read the :doc:`LLVM
	Makefile Guide <MakefileGuide>` for more details):

	.. code-block:: bash

	% make -C llvm/test

	or:

	.. code-block:: bash

	% make check

	If you have `Clang <http://clang.llvm.org/>`_ checked out and built, you
	can run the LLVM and Clang tests simultaneously using:

	.. code-block:: bash

	% make check-all

	To run the tests with Valgrind (Memcheck by default), just append
	``VG=1`` to the commands above, e.g.:

	.. code-block:: bash

	% make check VG=1

	To run individual tests or subsets of tests, you can use the ``llvm-lit``
	script which is built as part of LLVM. For example, to run the
	``Integer/BitPacked.ll`` test by itself you can run:

	.. code-block:: bash

	% llvm-lit ~/llvm/test/Integer/BitPacked.ll

	or to run all of the ARM CodeGen tests:

	.. code-block:: bash

	% llvm-lit ~/llvm/test/CodeGen/ARM

	For more information on using the :program:`lit` tool, see ``llvm-lit --help``
	or the :doc:`lit man page <CommandGuide/lit>`.

	Debugging Information tests
	---------------------------

	To run debugging information tests simply checkout the tests inside
	clang/test directory.

	.. code-block:: bash

	% cd clang/test
	% svn co http://llvm.org/svn/llvm-project/debuginfo-tests/trunk debuginfo-tests

	These tests are already set up to run as part of clang regression tests.

	Regression test structure
	=========================

	The LLVM regression tests are driven by :program:`lit` and are located in the
	``llvm/test`` directory.

	This directory contains a large array of small tests that exercise
	various features of LLVM and to ensure that regressions do not occur.
	The directory is broken into several sub-directories, each focused on a
	particular area of LLVM.

	Writing new regression tests
	----------------------------

	The regression test structure is very simple, but does require some
	information to be set. This information is gathered via ``configure``
	and is written to a file, ``test/lit.site.cfg`` in the build directory.
	The ``llvm/test`` Makefile does this work for you.

	In order for the regression tests to work, each directory of tests must
	have a ``lit.local.cfg`` file. :program:`lit` looks for this file to determine
	how to run the tests. This file is just Python code and thus is very
	flexible, but we've standardized it for the LLVM regression tests. If
	you're adding a directory of tests, just copy ``lit.local.cfg`` from
	another directory to get running. The standard ``lit.local.cfg`` simply
	specifies which files to look in for tests. Any directory that contains
	only directories does not need the ``lit.local.cfg`` file. Read the :doc:`Lit
	documentation <CommandGuide/lit>` for more information.

	Each test file must contain lines starting with "RUN:" that tell :program:`lit`
	how to run it. If there are no RUN lines, :program:`lit` will issue an error
	while running a test.

	RUN lines are specified in the comments of the test program using the
	keyword ``RUN`` followed by a colon, and lastly the command (pipeline)
	to execute. Together, these lines form the "script" that :program:`lit`
	executes to run the test case. The syntax of the RUN lines is similar to a
	shell's syntax for pipelines including I/O redirection and variable
	substitution. However, even though these lines may look like a shell
	script, they are not. RUN lines are interpreted by :program:`lit`.
	Consequently, the syntax differs from shell in a few ways. You can specify
	as many RUN lines as needed.

	:program:`lit` performs substitution on each RUN line to replace LLVM tool names
	with the full paths to the executable built for each tool (in
	``$(LLVM_OBJ_ROOT)/$(BuildMode)/bin)``. This ensures that :program:`lit` does
	not invoke any stray LLVM tools in the user's path during testing.

	Each RUN line is executed on its own, distinct from other lines unless
	its last character is ``\``. This continuation character causes the RUN
	line to be concatenated with the next one. In this way you can build up
	long pipelines of commands without making huge line lengths. The lines
	ending in ``\`` are concatenated until a RUN line that doesn't end in
	``\`` is found. This concatenated set of RUN lines then constitutes one
	execution. :program:`lit` will substitute variables and arrange for the pipeline
	to be executed. If any process in the pipeline fails, the entire line (and
	test case) fails too.

	Below is an example of legal RUN lines in a ``.ll`` file:

	.. code-block:: llvm

	; RUN: llvm-as < %s \| llvm-dis > %t1
	; RUN: llvm-dis < %s.bc-13 > %t2
	; RUN: diff %t1 %t2

	As with a Unix shell, the RUN lines permit pipelines and I/O
	redirection to be used. However, the usage is slightly different than
	for Bash. In general, it's useful to read the code of other tests to figure out
	what you can use in yours. The major differences are:

	- You can't do ``2>&1``. That will cause :program:`lit` to write to a file
	named ``&1``. Usually this is done to get stderr to go through a pipe. You
	can do that with ``\|&`` so replace this idiom:
	``... 2>&1 \| grep`` with ``... \|& grep``
	- You can only redirect to a file, not to another descriptor and not
	from a here document.

	There are some quoting rules that you must pay attention to when writing
	your RUN lines. In general nothing needs to be quoted. :program:`lit` won't
	strip off any quote characters so they will get passed to the invoked program.
	For example:

	.. code-block:: bash

	... \| grep 'find this string'

	This will fail because the ``'`` characters are passed to ``grep``. This would
	make ``grep`` to look for ``'find`` in the files ``this`` and
	``string'``. To avoid this use curly braces to tell :program:`lit` that it
	should treat everything enclosed as one value. So our example would become:

	.. code-block:: bash

	... \| grep {find this string}

	In general, you should strive to keep your RUN lines as simple as possible,
	using them only to run tools that generate the output you can then examine. The
	recommended way to examine output to figure out if the test passes it using the
	:doc:`FileCheck tool <CommandGuide/FileCheck>`. The usage of ``grep`` in RUN
	lines is discouraged.

	The FileCheck utility
	---------------------

	A powerful feature of the RUN lines is that it allows any arbitrary
	commands to be executed as part of the test harness. While standard
	(portable) unix tools like ``grep`` work fine on run lines, as you see
	above, there are a lot of caveats due to interaction with shell syntax,
	and we want to make sure the run lines are portable to a wide range of
	systems. Another major problem is that ``grep`` is not very good at checking
	to verify that the output of a tools contains a series of different
	output in a specific order. The :program:`FileCheck` tool was designed to
	help with these problems.

	:program:`FileCheck` is designed to read a file to check from standard input,
	and the set of things to verify from a file specified as a command line
	argument. :program:`FileCheck` is described in :doc:`the FileCheck man page
	<CommandGuide/FileCheck>`.

	Variables and substitutions
	---------------------------

	With a RUN line there are a number of substitutions that are permitted.
	To make a substitution just write the variable's name preceded by a ``$``.
	Additionally, for compatibility reasons with previous versions of the
	test library, certain names can be accessed with an alternate syntax: a
	% prefix. These alternates are deprecated and may go away in a future
	version.

	Here are the available variable names. The alternate syntax is listed in
	parentheses.

	``$test`` (``%s``)
	The full path to the test case's source. This is suitable for passing on
	the command line as the input to an LLVM tool.

	``%(line)``, ``%(line+<number>)``, ``%(line-<number>)``
	The number of the line where this variable is used, with an optional
	integer offset. This can be used in tests with multiple RUN lines,
	which reference test file's line numbers.

	``$srcdir``
	The source directory from where the ``make check`` was run.

	``objdir``
	The object directory that corresponds to the ``$srcdir``.

	``subdir``
	A partial path from the ``test`` directory that contains the
	sub-directory that contains the test source being executed.

	``srcroot``
	The root directory of the LLVM src tree.

	``objroot``
	The root directory of the LLVM object tree. This could be the same as
	the srcroot.

	``path``
	The path to the directory that contains the test case source. This is
	for locating any supporting files that are not generated by the test,
	but used by the test.

	``tmp``
	The path to a temporary file name that could be used for this test case.
	The file name won't conflict with other test cases. You can append to it
	if you need multiple temporaries. This is useful as the destination of
	some redirected output.

	``target_triplet`` (``%target_triplet``)
	The target triplet that corresponds to the current host machine (the one
	running the test cases). This should probably be called "host".

	``link`` (``%link``)
	This full link command used to link LLVM executables. This has all the
	configured ``-I``, ``-L`` and ``-l`` options.

	``shlibext`` (``%shlibext``)
	The suffix for the host platforms shared library (DLL) files. This
	includes the period as the first character.

	To add more variables, look at ``test/lit.cfg``.

	Other Features
	--------------

	To make RUN line writing easier, there are several helper scripts and programs
	in the ``llvm/test/Scripts`` directory. This directory is in the PATH
	when running tests, so you can just call these scripts using their name.
	For example:

	``ignore``
	This script runs its arguments and then always returns 0. This is useful
	in cases where the test needs to cause a tool to generate an error (e.g.
	to check the error output). However, any program in a pipeline that
	returns a non-zero result will cause the test to fail. This script
	overcomes that issue and nicely documents that the test case is
	purposefully ignoring the result code of the tool
	``not``
	This script runs its arguments and then inverts the result code from it.
	Zero result codes become 1. Non-zero result codes become 0.

	Sometimes it is necessary to mark a test case as "expected fail" or
	XFAIL. You can easily mark a test as XFAIL just by including ``XFAIL:``
	on a line near the top of the file. This signals that the test case
	should succeed if the test fails. Such test cases are counted separately
	by the testing tool. To specify an expected fail, use the XFAIL keyword
	in the comments of the test program followed by a colon and one or more
	failure patterns. Each failure pattern can be either ``*`` (to specify
	fail everywhere), or a part of a target triple (indicating the test
	should fail on that platform), or the name of a configurable feature
	(for example, ``loadable_module``). If there is a match, the test is
	expected to fail. If not, the test is expected to succeed. To XFAIL
	everywhere just specify ``XFAIL: *``. Here is an example of an ``XFAIL``
	line:

	.. code-block:: llvm

	; XFAIL: darwin,sun

	To make the output more useful, :program:`lit` will scan
	the lines of the test case for ones that contain a pattern that matches
	``PR[0-9]+``. This is the syntax for specifying a PR (Problem Report) number
	that is related to the test case. The number after "PR" specifies the
	LLVM bugzilla number. When a PR number is specified, it will be used in
	the pass/fail reporting. This is useful to quickly get some context when
	a test fails.

	Finally, any line that contains "END." will cause the special
	interpretation of lines to terminate. This is generally done right after
	the last RUN: line. This has two side effects:

	(a) it prevents special interpretation of lines that are part of the test
	program, not the instructions to the test case, and

	(b) it speeds things up for really big test cases by avoiding
	interpretation of the remainder of the file.

	``test-suite`` Overview
	=======================

	The ``test-suite`` module contains a number of programs that can be
	compiled and executed. The ``test-suite`` includes reference outputs for
	all of the programs, so that the output of the executed program can be
	checked for correctness.

	``test-suite`` tests are divided into three types of tests: MultiSource,
	SingleSource, and External.

	- ``test-suite/SingleSource``

	The SingleSource directory contains test programs that are only a
	single source file in size. These are usually small benchmark
	programs or small programs that calculate a particular value. Several
	such programs are grouped together in each directory.

	- ``test-suite/MultiSource``

	The MultiSource directory contains subdirectories which contain
	entire programs with multiple source files. Large benchmarks and
	whole applications go here.

	- ``test-suite/External``

	The External directory contains Makefiles for building code that is
	external to (i.e., not distributed with) LLVM. The most prominent
	members of this directory are the SPEC 95 and SPEC 2000 benchmark
	suites. The ``External`` directory does not contain these actual
	tests, but only the Makefiles that know how to properly compile these
	programs from somewhere else. When using ``LNT``, use the
	``--test-externals`` option to include these tests in the results.

	.. _test-suite-quickstart:

	``test-suite`` Quickstart
	-------------------------

	The modern way of running the ``test-suite`` is focused on testing and
	benchmarking complete compilers using the
	`LNT <http://llvm.org/docs/lnt>`_ testing infrastructure.

	For more information on using LNT to execute the ``test-suite``, please
	see the `LNT Quickstart <http://llvm.org/docs/lnt/quickstart.html>`_
	documentation.

	``test-suite`` Makefiles
	------------------------

	Historically, the ``test-suite`` was executed using a complicated setup
	of Makefiles. The LNT based approach above is recommended for most
	users, but there are some testing scenarios which are not supported by
	the LNT approach. In addition, LNT currently uses the Makefile setup
	under the covers and so developers who are interested in how LNT works
	under the hood may want to understand the Makefile based setup.

	For more information on the ``test-suite`` Makefile setup, please see
	the :doc:`Test Suite Makefile Guide <TestSuiteMakefileGuide>`.