LLVM Testing Infrastructure Guide

  1. Overview
  2. Requirements
  3. LLVM testing infrastructure organization
  4. Quick start
  5. Regression test structure
  6. test-suite Overview

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


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.


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.


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 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


% gmake check

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


% 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/BitCast.ll' test by itself you can run:

% llvm-lit ~/llvm/test/Integer/BitCast.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:

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 Lit documentation 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:

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 (whose basic command line arguments are described in the FileCheck man page 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. A simple example of using FileCheck from a RUN line looks like this:

; RUN: llvm-as < %s | llc -march=x86-64 | FileCheck %s

This syntax says to pipe the current file ("%s") into llvm-as, pipe that into llc, then pipe the output of llc into FileCheck. This means that FileCheck will be verifying its standard input (the llc output) against the filename argument specified (the original .ll file specified by "%s"). To see how this works, let's look at the rest of the .ll file (after the RUN line):

define void @sub1(i32* %p, i32 %v) {
; CHECK: sub1:
; CHECK: subl
        %0 = tail call i32 @llvm.atomic.load.sub.i32.p0i32(i32* %p, i32 %v)
        ret void

define void @inc4(i64* %p) {
; CHECK: inc4:
; CHECK: incq
        %0 = tail call i64 @llvm.atomic.load.add.i64.p0i64(i64* %p, i64 1)
        ret void

Here you can see some "CHECK:" lines specified in comments. Now you can see how the file is piped into llvm-as, then llc, and the machine code output is what we are verifying. FileCheck checks the machine code output to verify that it matches what the "CHECK:" lines specify.

The syntax of the CHECK: lines is very simple: they are fixed strings that must occur in order. FileCheck defaults to ignoring horizontal whitespace differences (e.g. a space is allowed to match a tab) but otherwise, the contents of the CHECK: line is required to match some thing in the test file exactly.

One nice thing about FileCheck (compared to grep) is that it allows merging test cases together into logical groups. For example, because the test above is checking for the "sub1:" and "inc4:" labels, it will not match unless there is a "subl" in between those labels. If it existed somewhere else in the file, that would not count: "grep subl" matches if subl exists anywhere in the file.

The FileCheck -check-prefix option

The FileCheck -check-prefix option allows multiple test configurations to be driven from one .ll file. This is useful in many circumstances, for example, testing different architectural variants with llc. Here's a simple example:

; RUN: llvm-as < %s | llc -mtriple=i686-apple-darwin9 -mattr=sse41 \
; RUN:              | FileCheck %s -check-prefix=X32
; RUN: llvm-as < %s | llc -mtriple=x86_64-apple-darwin9 -mattr=sse41 \
; RUN:              | FileCheck %s -check-prefix=X64

define <4 x i32> @pinsrd_1(i32 %s, <4 x i32> %tmp) nounwind {
        %tmp1 = insertelement <4 x i32> %tmp, i32 %s, i32 1
        ret <4 x i32> %tmp1
; X32: pinsrd_1:
; X32:    pinsrd $1, 4(%esp), %xmm0

; X64: pinsrd_1:
; X64:    pinsrd $1, %edi, %xmm0

In this case, we're testing that we get the expected code generation with both 32-bit and 64-bit code generation.

The "CHECK-NEXT:" directive

Sometimes you want to match lines and would like to verify that matches happen on exactly consecutive lines with no other lines in between them. In this case, you can use CHECK: and CHECK-NEXT: directives to specify this. If you specified a custom check prefix, just use "<PREFIX>-NEXT:". For example, something like this works as you'd expect:

define void @t2(<2 x double>* %r, <2 x double>* %A, double %B) {
	%tmp3 = load <2 x double>* %A, align 16
	%tmp7 = insertelement <2 x double> undef, double %B, i32 0
	%tmp9 = shufflevector <2 x double> %tmp3,
                              <2 x double> %tmp7,
                              <2 x i32> < i32 0, i32 2 >
	store <2 x double> %tmp9, <2 x double>* %r, align 16
	ret void
; CHECK: t2:
; CHECK: 	movl	8(%esp), %eax
; CHECK-NEXT: 	movapd	(%eax), %xmm0
; CHECK-NEXT: 	movhpd	12(%esp), %xmm0
; CHECK-NEXT: 	movl	4(%esp), %eax
; CHECK-NEXT: 	movapd	%xmm0, (%eax)
; CHECK-NEXT: 	ret

CHECK-NEXT: directives reject the input unless there is exactly one newline between it an the previous directive. A CHECK-NEXT cannot be the first directive in a file.

The "CHECK-NOT:" directive

The CHECK-NOT: directive is used to verify that a string doesn't occur between two matches (or the first match and the beginning of the file). For example, to verify that a load is removed by a transformation, a test like this can be used:

define i8 @coerce_offset0(i32 %V, i32* %P) {
  store i32 %V, i32* %P
  %P2 = bitcast i32* %P to i8*
  %P3 = getelementptr i8* %P2, i32 2

  %A = load i8* %P3
  ret i8 %A
; CHECK: @coerce_offset0
; CHECK-NOT: load
; CHECK: ret i8

FileCheck Pattern Matching Syntax

The CHECK: and CHECK-NOT: directives both take a pattern to match. For most uses of FileCheck, fixed string matching is perfectly sufficient. For some things, a more flexible form of matching is desired. To support this, FileCheck allows you to specify regular expressions in matching strings, surrounded by double braces: {{yourregex}}. Because we want to use fixed string matching for a majority of what we do, FileCheck has been designed to support mixing and matching fixed string matching with regular expressions. This allows you to write things like this:

; CHECK: movhpd	{{[0-9]+}}(%esp), {{%xmm[0-7]}}

In this case, any offset from the ESP register will be allowed, and any xmm register will be allowed.

Because regular expressions are enclosed with double braces, they are visually distinct, and you don't need to use escape characters within the double braces like you would in C. In the rare case that you want to match double braces explicitly from the input, you can use something ugly like {{[{][{]}} as your pattern.

FileCheck Variables

It is often useful to match a pattern and then verify that it occurs again later in the file. For codegen tests, this can be useful to allow any register, but verify that that register is used consistently later. To do this, FileCheck allows named variables to be defined and substituted into patterns. Here is a simple example:

; CHECK: test5:
; CHECK:    notw	[[REGISTER:%[a-z]+]]
; CHECK:    andw	{{.*}}[[REGISTER]]

The first check line matches a regex (%[a-z]+) and captures it into the variables "REGISTER". The second line verifies that whatever is in REGISTER occurs later in the file after an "andw". FileCheck variable references are always contained in [[ ]] pairs, are named, and their names can be formed with the regex "[a-zA-Z][a-zA-Z0-9]*". If a colon follows the name, then it is a definition of the variable, if not, it is a use.

FileCheck variables can be defined multiple times, and uses always get the latest value. Note that variables are all read at the start of a "CHECK" line and are all defined at the end. This means that if you have something like "CHECK: [[XYZ:.*]]x[[XYZ]]" that the check line will read the previous value of the XYZ variable and define a new one after the match is performed. If you need to do something like this you can probably take advantage of the fact that FileCheck is not actually line-oriented when it matches, this allows you to define two separate CHECK lines that match on the same line.

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.
The source directory from where the "make check" was run.
The object directory that corresponds to the $srcdir.
A partial path from the test directory that contains the sub-directory that contains the test source being executed.
The root directory of the LLVM src tree.
The root directory of the LLVM object tree. This could be the same as the srcroot.
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.
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:

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
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 regular expressions (separated by a comma). The regular expressions allow you to XFAIL the test conditionally by host platform. The regular expressions following the : are matched against the target triplet for the host machine. 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: (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 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 Test Suite Makefile Guide.

Valid CSS Valid HTML 4.01 John T. Criswell, Daniel Dunbar, Reid Spencer, and Tanya Lattner
The LLVM Compiler Infrastructure
Last modified: $Date: 2012-04-18 01:02:25 -0700 (Wed, 18 Apr 2012) $