test-suite Guide

Quickstart

  1. The lit test runner is required to run the tests. You can either use one from an LLVM build:

    % <path to llvm build>/bin/llvm-lit --version
lit 0.8.0dev

    An alternative is installing it as a python package in a python virtual environment:

    % mkdir venv
% virtualenv venv
% . venv/bin/activate
% pip install svn+https://llvm.org/svn/llvm-project/llvm/trunk/utils/lit
% lit --version
lit 0.8.0dev

  2. Check out the test-suite module with:

    % git clone https://github.com/llvm/llvm-test-suite.git test-suite

  3. Create a build directory and use CMake to configure the suite. Use the CMAKE_C_COMPILER option to specify the compiler to test. Use a cache file to choose a typical build configuration:

    % mkdir test-suite-build
% cd test-suite-build
% cmake -DCMAKE_C_COMPILER=<path to llvm build>/bin/clang \
        -C../test-suite/cmake/caches/O3.cmake \
        ../test-suite

NOTE! if you are using your built clang, and you want to build and run the MicroBenchmarks/XRay microbenchmarks, you need to add compiler-rt to your LLVM_ENABLE_RUNTIMES cmake flag.

  1. Build the benchmarks:

    % make
Scanning dependencies of target timeit-target
[  0%] Building C object tools/CMakeFiles/timeit-target.dir/timeit.c.o
[  0%] Linking C executable timeit-target
...

  2. Run the tests with lit:

    % llvm-lit -v -j 1 -o results.json .
-- Testing: 474 tests, 1 threads --
PASS: test-suite :: MultiSource/Applications/ALAC/decode/alacconvert-decode.test (1 of 474)
********** TEST 'test-suite :: MultiSource/Applications/ALAC/decode/alacconvert-decode.test' RESULTS **********
compile_time: 0.2192
exec_time: 0.0462
hash: "59620e187c6ac38b36382685ccd2b63b"
size: 83348
**********
PASS: test-suite :: MultiSource/Applications/ALAC/encode/alacconvert-encode.test (2 of 474)
...

NOTE! even in the case you only want to get the compile-time results(code size, llvm stats etc), you need to run the test with the above llvm-lit command. In that case, the results.json file will contain compile-time metrics.

  1. Show and compare result files (optional):

    # Make sure pandas and scipy are installed. Prepend `sudo` if necessary.
% pip install pandas scipy
# Show a single result file:
% test-suite/utils/compare.py results.json
# Compare two result files:
% test-suite/utils/compare.py results_a.json results_b.json

Structure

The test-suite contains benchmark and test programs. The programs come with reference outputs so that their correctness can be checked. The suite comes with tools to collect metrics such as benchmark runtime, compilation time and code size.

The test-suite is divided into several directories:

  • SingleSource/

    Contains test programs that are only a single source file in size. A subdirectory may contain several programs.

  • MultiSource/

    Contains subdirectories which entire programs with multiple source files. Large benchmarks and whole applications go here.

  • MicroBenchmarks/

    Programs using the google-benchmark library. The programs define functions that are run multiple times until the measurement results are statistically significant.

  • External/

    Contains descriptions and test data for code that cannot be directly distributed with the test-suite. The most prominent members of this directory are the SPEC CPU benchmark suites. See External Suites.

  • Bitcode/

    These tests are mostly written in LLVM bitcode.

  • CTMark/

    Contains symbolic links to other benchmarks forming a representative sample for compilation performance measurements.

Benchmarks

Every program can work as a correctness test. Some programs are unsuitable for performance measurements. Setting the TEST_SUITE_BENCHMARKING_ONLY CMake option to ON will disable them.

Configuration

The test-suite has configuration options to customize building and running the benchmarks. CMake can print a list of them:

% cd test-suite-build
# Print basic options:
% cmake -LH
# Print all options:
% cmake -LAH

Common Configuration Options

  • CMAKE_C_FLAGS

    Specify extra flags to be passed to C compiler invocations. The flags are also passed to the C++ compiler and linker invocations. See https://cmake.org/cmake/help/latest/variable/CMAKE_LANG_FLAGS.html

  • CMAKE_C_COMPILER

    Select the C compiler executable to be used. Note that the C++ compiler is inferred automatically i.e. when specifying path/to/clang CMake will automatically use path/to/clang++ as the C++ compiler. See https://cmake.org/cmake/help/latest/variable/CMAKE_LANG_COMPILER.html

  • CMAKE_Fortran_COMPILER

    Select the Fortran compiler executable to be used. Not set by default and not required unless running the Fortran Test Suite.

  • CMAKE_BUILD_TYPE

    Select a build type like OPTIMIZE or DEBUG selecting a set of predefined compiler flags. These flags are applied regardless of the CMAKE_C_FLAGS option and may be changed by modifying CMAKE_C_FLAGS_OPTIMIZE etc. See https://cmake.org/cmake/help/latest/variable/CMAKE_BUILD_TYPE.html

  • TEST_SUITE_FORTRAN

    Activate that Fortran tests. This is a work in progress. More information can be found in the Flang documentation

  • TEST_SUITE_RUN_UNDER

    Prefix test invocations with the given tool. This is typically used to run cross-compiled tests within a simulator tool.

  • TEST_SUITE_BENCHMARKING_ONLY

    Disable tests that are unsuitable for performance measurements. The disabled tests either run for a very short time or are dominated by I/O performance making them unsuitable as compiler performance tests.

  • TEST_SUITE_SUBDIRS

    Semicolon-separated list of directories to include. This can be used to only build parts of the test-suite or to include external suites. This option does not work reliably with deeper subdirectories as it skips intermediate CMakeLists.txt files which may be required.

  • TEST_SUITE_COLLECT_STATS

    Collect internal LLVM statistics. Appends -save-stats=obj when invoking the compiler and makes the lit runner collect and merge the statistic files.

  • TEST_SUITE_RUN_BENCHMARKS

    If this is set to OFF then lit will not actually run the tests but just collect build statistics like compile time and code size.

  • TEST_SUITE_USE_PERF

    Use the perf tool for time measurement instead of the timeit tool that comes with the test-suite. The perf is usually available on linux systems.

  • TEST_SUITE_SPEC2000_ROOT, TEST_SUITE_SPEC2006_ROOT, TEST_SUITE_SPEC2017_ROOT, …

    Specify installation directories of external benchmark suites. You can find more information about expected versions or usage in the README files in the External directory (such as External/SPEC/README)

Common CMake Flags

  • -GNinja

    Generate build files for the ninja build tool.

  • -Ctest-suite/cmake/caches/<cachefile.cmake>

    Use a CMake cache. The test-suite comes with several CMake caches which predefine common or tricky build configurations.

Displaying and Analyzing Results

The compare.py script displays and compares result files. A result file is produced when invoking lit with the -o filename.json flag.

Example usage:

  • Basic Usage:

    % test-suite/utils/compare.py baseline.json
Warning: 'test-suite :: External/SPEC/CINT2006/403.gcc/403.gcc.test' has No metrics!
Tests: 508
Metric: exec_time

Program                                         baseline

INT2006/456.hmmer/456.hmmer                   1222.90
INT2006/464.h264ref/464.h264ref               928.70
...
             baseline
count  506.000000
mean   20.563098
std    111.423325
min    0.003400
25%    0.011200
50%    0.339450
75%    4.067200
max    1222.896800

  • Show compile_time or text segment size metrics:

    % test-suite/utils/compare.py -m compile_time baseline.json
% test-suite/utils/compare.py -m size.__text baseline.json

  • Compare two result files and filter short running tests:

    % test-suite/utils/compare.py --filter-short baseline.json experiment.json
...
Program                                         baseline  experiment  diff

SingleSour.../Benchmarks/Linpack/linpack-pc     5.16      4.30        -16.5%
MultiSourc...erolling-dbl/LoopRerolling-dbl     7.01      7.86         12.2%
SingleSour...UnitTests/Vectorizer/gcc-loops     3.89      3.54        -9.0%
...

  • Merge multiple baseline and experiment result files by taking the minimum runtime each:

    % test-suite/utils/compare.py base0.json base1.json base2.json vs exp0.json exp1.json exp2.json

Continuous Tracking with LNT

LNT is a set of client and server tools for continuously monitoring performance. You can find more information at https://llvm.org/docs/lnt. The official LNT instance of the LLVM project is hosted at http://lnt.llvm.org.

External Suites

External suites such as SPEC can be enabled by either

  • placing (or linking) them into the test-suite/test-suite-externals/xxx directory (example: test-suite/test-suite-externals/speccpu2000)

  • using a configuration option such as -D TEST_SUITE_SPEC2000_ROOT=path/to/speccpu2000

You can find further information in the respective README files such as test-suite/External/SPEC/README.

For the SPEC benchmarks you can switch between the test, train and ref input datasets via the TEST_SUITE_RUN_TYPE configuration option. The train dataset is used by default.

Custom Suites

You can build custom suites using the test-suite infrastructure. A custom suite has a CMakeLists.txt file at the top directory. The CMakeLists.txt will be picked up automatically if placed into a subdirectory of the test-suite or when setting the TEST_SUITE_SUBDIRS variable:

% cmake -DTEST_SUITE_SUBDIRS=path/to/my/benchmark-suite ../test-suite

Profile Guided Optimization

Profile guided optimization requires to compile and run twice. First the benchmark should be compiled with profile generation instrumentation enabled and setup for training data. The lit runner will merge the profile files using llvm-profdata so they can be used by the second compilation run.

Example:

# Profile generation run using LLVM IR PGO:
% cmake -DTEST_SUITE_PROFILE_GENERATE=ON \
        -DTEST_SUITE_USE_IR_PGO=ON \
        -DTEST_SUITE_RUN_TYPE=train \
        ../test-suite
% make
% llvm-lit .
# Use the profile data for compilation and actual benchmark run:
% cmake -DTEST_SUITE_PROFILE_GENERATE=OFF \
        -DTEST_SUITE_PROFILE_USE=ON \
        -DTEST_SUITE_RUN_TYPE=ref \
        .
% make
% llvm-lit -o result.json .

To use Clang frontend’s PGO instead of LLVM IR PGO, set -DTEST_SUITE_USE_IR_PGO=OFF.

The TEST_SUITE_RUN_TYPE setting only affects the SPEC benchmark suites.

Cross Compilation and External Devices

Compilation

CMake allows to cross compile to a different target via toolchain files. More information can be found here:

Cross compilation from macOS to iOS is possible with the test-suite/cmake/caches/target-target-*-iphoneos-internal.cmake CMake cache files; this requires an internal iOS SDK.

Running

There are two ways to run the tests in a cross compilation setting:

  • Via SSH connection to an external device: The TEST_SUITE_REMOTE_HOST option should be set to the SSH hostname. The executables and data files need to be transferred to the device after compilation. This is typically done via the rsync make target. After this, the lit runner can be used on the host machine. It will prefix the benchmark and verification command lines with an ssh command.

    Example:

    % cmake -G Ninja -D CMAKE_C_COMPILER=path/to/clang \
        -C ../test-suite/cmake/caches/target-arm64-iphoneos-internal.cmake \
        -D CMAKE_BUILD_TYPE=Release \
        -D TEST_SUITE_REMOTE_HOST=mydevice \
        ../test-suite
% ninja
% ninja rsync
% llvm-lit -j1 -o result.json .

  • You can specify a simulator for the target machine with the TEST_SUITE_RUN_UNDER setting. The lit runner will prefix all benchmark invocations with it.

Running the test-suite via LNT

The LNT tool can run the test-suite. Use this when submitting test results to an LNT instance. See https://llvm.org/docs/lnt/tests.html#llvm-cmake-test-suite for details.

Running the test-suite via Makefiles (deprecated)

Note: The test-suite comes with a set of Makefiles that are considered deprecated. They do not support newer testing modes like Bitcode or Microbenchmarks and are harder to use.

Old documentation is available in the test-suite Makefile Guide.