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
Check out the
% git clone https://github.com/llvm/llvm-test-suite.git test-suite
Create a build directory and use CMake to configure the suite. Use the
CMAKE_C_COMPILERoption 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
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 ...
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) ...
Show and compare result files (optional):
# Make sure pandas is installed. Prepend `sudo` if necessary. % pip install pandas # 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
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:
Contains test programs that are only a single source file in size. A subdirectory may contain several programs.
Contains subdirectories which entire programs with multiple source files. Large benchmarks and whole applications go here.
Programs using the google-benchmark library. The programs define functions that are run multiple times until the measurement results are statistically significant.
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.
These tests are mostly written in LLVM bitcode.
Contains symbolic links to other benchmarks forming a representative sample for compilation performance measurements.
Every program can work as a correctness test. Some programs are unsuitable for
performance measurements. Setting the
ON will disable them.
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¶
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
Select the C compiler executable to be used. Note that the C++ compiler is inferred automatically i.e. when specifying
path/to/clangCMake will automatically use
path/to/clang++as the C++ compiler. See https://cmake.org/cmake/help/latest/variable/CMAKE_LANG_COMPILER.html
Select a build type like
DEBUGselecting a set of predefined compiler flags. These flags are applied regardless of the
CMAKE_C_FLAGSoption and may be changed by modifying
CMAKE_C_FLAGS_OPTIMIZEetc. See https://cmake.org/cmake/help/latest/variable/CMAKE_BUILD_TYPE.html
Prefix test invocations with the given tool. This is typically used to run cross-compiled tests within a simulator tool.
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.
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.txtfiles which may be required.
Collect internal LLVM statistics. Appends
-save-stats=objwhen invocing the compiler and makes the lit runner collect and merge the statistic files.
If this is set to
OFFthen lit will not actually run the tests but just collect build statistics like compile time and code size.
perftool for time measurement instead of the
timeittool that comes with the test-suite. The
perfis usually available on linux systems.
Specify installation directories of external benchmark suites. You can find more information about expected versions or usage in the README files in the
Externaldirectory (such as
Common CMake Flags¶
Generate build files for the ninja build tool.
Use a CMake cache. The test-suite comes with several CMake caches which predefine common or tricky build configurations.
Displaying and Analyzing Results¶
compare.py script displays and compares result files. A result file is
produced when invoking lit with the
-o filename.json flag.
% 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
External suites such as SPEC can be enabled by either
placing (or linking) them into the
using a configuration option such as
You can find further information in the respective README files such as
For the SPEC benchmarks you can switch between the
ref input datasets via the
TEST_SUITE_RUN_TYPE configuration option.
train dataset is used by default.
You can build custom suites using the test-suite infrastructure. A custom suite
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
% 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
llvm-profdata so they can be used by the second compilation run.
# Profile generation run: % cmake -DTEST_SUITE_PROFILE_GENERATE=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 .
TEST_SUITE_RUN_TYPE setting only affects the SPEC benchmark suites.
Cross Compilation and External Devices¶
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.
There are two ways to run the tests in a cross compilation setting:
Via SSH connection to an external device: The
TEST_SUITE_REMOTE_HOSToption 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
rsyncmake target. After this, the lit runner can be used on the host machine. It will prefix the benchmark and verification command lines with an
% cmake -G Ninja -D CMAKE_C_COMPILER=path/to/clang \ -C ../test-suite/cmake/caches/target-arm64-iphoneos-internal.cmake \ -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_UNDERsetting. 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.