[llvm-dev] Separate test harness for LLVM test-suite

Mon Jul 9 11:46:28 PDT 2018

> On Jul 9, 2018, at 10:55 AM, Roman Lebedev via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> 
> On Mon, Jul 9, 2018 at 10:26 AM, Elena Lepilkina via llvm-dev
> <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>> wrote:
>> Dear community,
>> 
>> 
>> 
>> LLVM test-suite includes both default applications (benchmarks, tests) and
>> test harness (CMake modules, lit-support, some scripts, etc.). Test suite
>> provides extension interface to add “external” tests suite and folders. This
>> worked well, we enhanced basic harness and integrated large set of internal
>> benchmarks and applications.
>> 
>> 
>> 
>> However, we have users interested in LLVM test harness to build, profile,
>> test applications and experiment with tools/compilers without using
>> applications from full LLVM test-suite (~2,5 Gb).
>> 
>> 
>> 
>> Are there reasons why separation of test-suite into 1) basic test-harness
>> and 2) applications is undesirable or impossible?
> I would like to cautiously +1 this question.
> 
> I've been personally eyeing using LNT for personal benchmarking needs,
> but so far did not get to it. There seems to be no good docs (with examples!)
> on how to actually write an external lnt test producer, which is understandable,
> and the test-suite itself is rather tightly coupled with the LLVM.

Note that you do not need LNT to run benchmarks. LNT is good for storing and tracking benchmark results over time. For simple A/B tests you are usually better of just running llvm-testsuite directly via cmake.

Thanks to Chris there is some introduction about it here: http://llvm.org/docs/TestSuiteMakefileGuide.html#running-the-test-suite-via-cmake <http://llvm.org/docs/TestSuiteMakefileGuide.html#running-the-test-suite-via-cmake> 

You can conveniently view the results via test-suite/results/compare.py

llvm-testsuites cmake files are also designed to be extensible. Unfortunately this is not separately documented yet (the 1 sentence explanation is: Create a folder and write your own CMakeLists.txt and point TEST_SUITE_SUBDIRS to it at cmake time).

I'd be happy to answer any questions in the area; I'd also highly apreciate it if someone wanted to contribute to LLVM by writing the missing documentation ;-)

> 
> Thus i too think that such a split into the supporting framework,
> and all the actual benchmarks *may* be a good thing.
> Or at least i would love to see some good docs.

The driving code is already modular and you can mix and match testsuite (the included ones or by writing external ones) by setting TEST_SUITE_SUBDIRS. We successfully use this for some additional test-suite modes like CTMark or the new MicroBenchmarks; we also have some internal test-suite here that now plug into this system. This is good software design and we should make sure it stays the way it is.

Regardless I would vote to not split things up: The situation actually feels similar to the mono-repository vs. multi-repository debate we have on the clang/llvm/compiler-rt/... side. My take here would be that things that are usually shipped or used as a unit should stay in the same repository. If you end up in a situation where you often have to synchronize commits across repositories things become more complicated and development slows down. My impression is that the test-suite driver and the core test-suite is in the majority of cases used together, indicating to me that it is benefitial to keep them in the same repository.

- Matthias

> 
>> We will be glad to hear opinions of community.
>> 
>> 
>> 
>> Best regards,
>> 
>> Elena Lepilkina,
> Roman.
> 
>> Synopsys Corp, ARC processors
>> 
>> 
>> 
>> 
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