LLVM Testing Infrastructure Guide¶
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 2.7 or later.
If you intend to run the test-suite, you will also need a development version of zlib (zlib1g-dev is known to work on several Linux distributions).
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 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 test-suite Quickstart for more information on running these tests.
Regression tests¶
To run all of the LLVM regression tests use the check-llvm target:
% make check-llvm
If you have Clang checked out and built, you can run the LLVM and Clang tests simultaneously using:
% make check-all
To run the tests with Valgrind (Memcheck by default), use the LIT_ARGS
make
variable to pass the required options to lit. For example, you can use:
% make check LIT_ARGS="-v --vg --vg-leak"
to enable testing with valgrind and with leak checking enabled.
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.
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. 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.
Each test file must contain lines starting with “RUN:” that tell lit how to run it. If there are no RUN lines, 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 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 lit.
Consequently, the syntax differs from shell 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. 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:
; 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.
There are some quoting rules that you must pay attention to when writing your RUN lines. In general nothing needs to be quoted. lit won’t strip off any quote characters so they will get passed to the invoked program. To avoid this use curly braces to tell lit that it should treat everything enclosed as one value.
In general, you should strive to keep your RUN lines as simple as possible, using them only to run tools that generate textual output you can then examine. The recommended way to examine output to figure out if the test passes is using the FileCheck tool. [The usage of grep in RUN lines is deprecated - please do not send or commit patches that use it.]
Put related tests into a single file rather than having a separate file per test. Check if there are files already covering your feature and consider adding your code there instead of creating a new file.
Extra files¶
If your test requires extra files besides the file containing the RUN:
lines, the idiomatic place to put them is in a subdirectory Inputs
.
You can then refer to the extra files as %S/Inputs/foo.bar
.
For example, consider test/Linker/ident.ll
. The directory structure is
as follows:
test/
Linker/
ident.ll
Inputs/
ident.a.ll
ident.b.ll
For convenience, these are the contents:
;;;;; ident.ll:
; RUN: llvm-link %S/Inputs/ident.a.ll %S/Inputs/ident.b.ll -S | FileCheck %s
; Verify that multiple input llvm.ident metadata are linked together.
; CHECK-DAG: !llvm.ident = !{!0, !1, !2}
; CHECK-DAG: "Compiler V1"
; CHECK-DAG: "Compiler V2"
; CHECK-DAG: "Compiler V3"
;;;;; Inputs/ident.a.ll:
!llvm.ident = !{!0, !1}
!0 = metadata !{metadata !"Compiler V1"}
!1 = metadata !{metadata !"Compiler V2"}
;;;;; Inputs/ident.b.ll:
!llvm.ident = !{!0}
!0 = metadata !{metadata !"Compiler V3"}
For symmetry reasons, ident.ll
is just a dummy file that doesn’t
actually participate in the test besides holding the RUN:
lines.
Note
Some existing tests use RUN: true
in extra files instead of just
putting the extra files in an Inputs/
directory. This pattern is
deprecated.
Fragile tests¶
It is easy to write a fragile test that would fail spuriously if the tool being
tested outputs a full path to the input file. For example, opt by
default outputs a ModuleID
:
$ cat example.ll
define i32 @main() nounwind {
ret i32 0
}
$ opt -S /path/to/example.ll
; ModuleID = '/path/to/example.ll'
define i32 @main() nounwind {
ret i32 0
}
ModuleID
can unexpectedly match against CHECK
lines. For example:
; RUN: opt -S %s | FileCheck
define i32 @main() nounwind {
; CHECK-NOT: load
ret i32 0
}
This test will fail if placed into a download
directory.
To make your tests robust, always use opt ... < %s
in the RUN line.
opt does not output a ModuleID
when input comes from stdin.
Platform-Specific Tests¶
Whenever adding tests that require the knowledge of a specific platform, either related to code generated, specific output or back-end features, you must make sure to isolate the features, so that buildbots that run on different architectures (and don’t even compile all back-ends), don’t fail.
The first problem is to check for target-specific output, for example sizes of structures, paths and architecture names, for example:
- Tests containing Windows paths will fail on Linux and vice-versa.
- Tests that check for
x86_64
somewhere in the text will fail anywhere else. - Tests where the debug information calculates the size of types and structures.
Also, if the test rely on any behaviour that is coded in any back-end, it must
go in its own directory. So, for instance, code generator tests for ARM go
into test/CodeGen/ARM
and so on. Those directories contain a special
lit
configuration file that ensure all tests in that directory will
only run if a specific back-end is compiled and available.
For instance, on test/CodeGen/ARM
, the lit.local.cfg
is:
config.suffixes = ['.ll', '.c', '.cpp', '.test']
if not 'ARM' in config.root.targets:
config.unsupported = True
Other platform-specific tests are those that depend on a specific feature
of a specific sub-architecture, for example only to Intel chips that support AVX2
.
For instance, test/CodeGen/X86/psubus.ll
tests three sub-architecture
variants:
; RUN: llc -mcpu=core2 < %s | FileCheck %s -check-prefix=SSE2
; RUN: llc -mcpu=corei7-avx < %s | FileCheck %s -check-prefix=AVX1
; RUN: llc -mcpu=core-avx2 < %s | FileCheck %s -check-prefix=AVX2
And the checks are different:
; SSE2: @test1
; SSE2: psubusw LCPI0_0(%rip), %xmm0
; AVX1: @test1
; AVX1: vpsubusw LCPI0_0(%rip), %xmm0, %xmm0
; AVX2: @test1
; AVX2: vpsubusw LCPI0_0(%rip), %xmm0, %xmm0
So, if you’re testing for a behaviour that you know is platform-specific or depends on special features of sub-architectures, you must add the specific triple, test with the specific FileCheck and put it into the specific directory that will filter out all other architectures.
Constraining test execution¶
Some tests can be run only in specific configurations, such as
with debug builds or on particular platforms. Use REQUIRES
and UNSUPPORTED
to control when the test is enabled.
Some tests are expected to fail. For example, there may be a known bug
that the test detect. Use XFAIL
to mark a test as an expected failure.
An XFAIL
test will be successful if its execution fails, and
will be a failure if its execution succeeds.
; This test will be only enabled in the build with asserts.
; REQUIRES: asserts
; This test is disabled on Linux.
; UNSUPPORTED: -linux-
; This test is expected to fail on PowerPC.
; XFAIL: powerpc
REQUIRES
and UNSUPPORTED
and XFAIL
all accept a comma-separated
list of boolean expressions. The values in each expression may be:
- Features added to
config.available_features
by configuration files such aslit.cfg
. - Substrings of the target triple (
UNSUPPORTED
andXFAIL
only).
REQUIRES
enables the test if all expressions are true.UNSUPPORTED
disables the test if any expression is true.XFAIL
expects the test to fail if any expression is true.As a special case, XFAIL: *
is expected to fail everywhere.
; This test is disabled on Windows,
; and is disabled on Linux, except for Android Linux.
; UNSUPPORTED: windows, linux && !android
; This test is expected to fail on both PowerPC and ARM.
; XFAIL: powerpc || arm
Substitutions¶
Besides replacing LLVM tool names the following substitutions are performed in RUN lines:
%%
- Replaced by a single
%
. This allows escaping other substitutions. %s
File path to the test case’s source. This is suitable for passing on the command line as the input to an LLVM tool.
Example:
/home/user/llvm/test/MC/ELF/foo_test.s
%S
Directory path to the test case’s source.
Example:
/home/user/llvm/test/MC/ELF
%t
File 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.
Example:
/home/user/llvm.build/test/MC/ELF/Output/foo_test.s.tmp
%T
Directory of
%t
. Deprecated. Shouldn’t be used, because it can be easily misused and cause race conditions between tests.Use
rm -rf %t && mkdir %t
instead if a temporary directory is necessary.Example:
/home/user/llvm.build/test/MC/ELF/Output
%{pathsep}
Expands to the path separator, i.e.:
(or;
on Windows).
%/s, %/S, %/t, %/T:
Act like the corresponding substitution above but replace any
\
character with a/
. This is useful to normalize path separators.Example:
%s: C:\Desktop Files/foo_test.s.tmp
Example:
%/s: C:/Desktop Files/foo_test.s.tmp
%:s, %:S, %:t, %:T:
Act like the corresponding substitution above but remove colons at the beginning of Windows paths. This is useful to allow concatenation of absolute paths on Windows to produce a legal path.
Example:
%s: C:\Desktop Files\foo_test.s.tmp
Example:
%:s: C\Desktop Files\foo_test.s.tmp
LLVM-specific substitutions:
%shlibext
The suffix for the host platforms shared library files. This includes the period as the first character.
Example:
.so
(Linux),.dylib
(OS X),.dll
(Windows)%exeext
The suffix for the host platforms executable files. This includes the period as the first character.
Example:
.exe
(Windows), empty on Linux.%(line)
,%(line+<number>)
,%(line-<number>)
- The number of the line where this substitution is used, with an optional integer offset. This can be used in tests with multiple RUN lines, which reference test file’s line numbers.
Clang-specific substitutions:
%clang
- Invokes the Clang driver.
%clang_cpp
- Invokes the Clang driver for C++.
%clang_cl
- Invokes the CL-compatible Clang driver.
%clangxx
- Invokes the G++-compatible Clang driver.
%clang_cc1
- Invokes the Clang frontend.
%itanium_abi_triple
,%ms_abi_triple
- These substitutions can be used to get the current target triple adjusted to
the desired ABI. For example, if the test suite is running with the
i686-pc-win32
target,%itanium_abi_triple
will expand toi686-pc-mingw32
. This allows a test to run with a specific ABI without constraining it to a specific triple.
To add more substituations, look at test/lit.cfg
or lit.local.cfg
.
Options¶
The llvm lit configuration allows to customize some things with user options:
llc
,opt
, …Substitute the respective llvm tool name with a custom command line. This allows to specify custom paths and default arguments for these tools. Example:
% llvm-lit “-Dllc=llc -verify-machineinstrs”
run_long_tests
- Enable the execution of long running tests.
llvm_site_config
- Load the specified lit configuration instead of the default one.
Other Features¶
To make RUN line writing easier, there are several helper programs. These helpers are in the PATH when running tests, so you can just call them using their name. For example:
not
- This program runs its arguments and then inverts the result code from it. Zero result codes become 1. Non-zero result codes become 0.
To make the output more useful, 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:
- it prevents special interpretation of lines that are part of the test program, not the instructions to the test case, and
- 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 usingLNT
, 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 Test Suite Makefile Guide.