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LLVM Testing Infrastructure Guide

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

.. 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 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. They are usually written in LLVM assembly language, but can be written in other languages if the test targets a particular language front end (and the appropriate --with-llvmgcc options were used at configure time of the llvm module). These tests are driven by the 'lit' testing tool, which is part of LLVM.

These code fragments are not complete programs. The code generated from them is never executed to determine correct behavior.

These code fragment tests 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. In most cases, this will be a small piece of LLVM assembly language code, often 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 master Makefile in the llvm/test directory:

% gmake -C llvm/test

or

% gmake check

If you have Clang checked out and built, you can run the LLVM and Clang tests simultaneously using:

or

% gmake check-all

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

% gmake 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:

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

or to run all of the ARM CodeGen tests:

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

For more information on using the 'lit' tool, see 'llvm-lit --help' or the 'lit' man page.

Debugging Information tests

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

% 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 '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. A few of the important ones are:

  • Analysis: checks Analysis passes.
  • Archive: checks the Archive library.
  • Assembler: checks Assembly reader/writer functionality.
  • Bitcode: checks Bitcode reader/writer functionality.
  • CodeGen: checks code generation and each target.
  • Features: checks various features of the LLVM language.
  • Linker: tests bitcode linking.
  • Transforms: tests each of the scalar, IPO, and utility transforms to ensure they make the right transformations.
  • Verifier: tests the IR verifier.

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, lit.site.cfg in llvm/test. 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. 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.

The llvm-runtests function looks at each file that is passed to it and gathers any lines together that match "RUN:". These are the "RUN" lines that specify how the test is to be run. So, each test script must contain RUN lines if it is to do anything. If there are no RUN lines, the llvm-runtests function will issue an error and the test will fail.

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 llvm-runtests 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 directly by the Tcl exec command. They are never executed by a shell. Consequently the syntax differs from normal shell script syntax in a few ways. You can specify as many RUN lines as needed.

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 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. Tcl 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:

; 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. To check what's legal, see the documentation for the Tcl exec command and the tutorial. The major differences are:

  • You can't do 2>&1. That will cause Tcl to write to a file named &1. Usually this is done to get stderr to go through a pipe. You can do that in tcl 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.
  • tcl supports redirecting to open files with the @ syntax but you shouldn't use that here.

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

... | grep 'find this string'

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

... | grep {find this string}

Additionally, the characters [ and ] are treated specially by Tcl. They tell Tcl to interpret the content as a command to execute. Since these characters are often used in regular expressions this can have disastrous results and cause the entire test run in a directory to fail. For example, a common idiom is to look for some basicblock number:

... | grep bb[2-8]

This, however, will cause Tcl to fail because its going to try to execute a program named "2-8". Instead, what you want is this:

... | grep {bb\[2-8\]}

Finally, if you need to pass the \ character down to a program, then it must be doubled. This is another Tcl special character. So, suppose you had:

... | grep 'i32\*'

This will fail to match what you want (a pointer to i32). First, the ' do not get stripped off. Second, the \ gets stripped off by Tcl so what grep sees is: 'i32*'. That's not likely to match anything. To resolve this you must use \\ and the {}, like this:

... | grep {i32\\*}

If your system includes GNU grep, make sure that GREP_OPTIONS is not set in your environment. Otherwise, you may get invalid results (both false positives and false negatives).

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 Tcl 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 FileCheck tool was designed to help with these problems.

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. 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. In general, any Tcl variable that is available in the substitute function (in test/lib/llvm.exp) can be substituted into a RUN line. 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 share library (dll) files. This includes the period as the first character.

To add more variables, two things need to be changed. First, add a line in the test/Makefile that creates the site.exp file. This will "set" the variable as a global in the site.exp file. Second, in the test/lib/llvm.exp file, in the substitute proc, add the variable name to the list of "global" declarations at the beginning of the proc. That's it, the variable can then be used in test scripts.

Other Features

To make RUN line writing easier, there are several shell scripts located 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. This is useful to invert the result of a grep. For example "not grep X" means succeed only if you don't find X in the input.

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:

; XFAIL: darwin,sun

To make the output more useful, the llvm_runtest function wil 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:

  1. it prevents special interpretation of lines that are part of the test program, not the instructions to the test case, and
  2. 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

The modern way of running the test-suite is focused on testing and benchmarking complete compilers using the LNT testing infrastructure.

For more information on using LNT to execute the test-suite, please see the LNT Quickstart 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>`.