[PATCH] D73776: Entropic: Boosting LibFuzzer Performance

[marcel via Phabricator via llvm-commits]

marcel marked 4 inline comments as done.
marcel added inline comments.


================
Comment at: compiler-rt/lib/fuzzer/tests/FuzzerUnittest.cpp:595
   Random Rand(0);
-  std::unique_ptr<InputCorpus> C(new InputCorpus(""));
+  struct EntropicOptions Entropic = {false, 0xFF, 100};
+  std::unique_ptr<InputCorpus> C(new InputCorpus("", Entropic));
----------------
kcc wrote:
> When running 'ninja check-fuzzer' this test fails for me: 
> 
> That's weird: why does the functionality change with Entropic off? 
> 
> [5/9] Running Fuzzer unit tests
> FAIL: LLVMFuzzer-Unittest :: ./Fuzzer-x86_64-Test/Corpus.Distribution (48 of 55)
> ******************** TEST 'LLVMFuzzer-Unittest :: ./Fuzzer-x86_64-Test/Corpus.Distribution' FAILED ********************
> Note: Google Test filter = Corpus.Distribution
> [==========] Running 1 test from 1 test case.
> [----------] Global test environment set-up.
> [----------] 1 test from Corpus
> [ RUN      ] Corpus.Distribution
> /usr/local/google/home/kcc/llvm-project/compiler-rt/lib/fuzzer/tests/FuzzerUnittest.cpp:609: Failure
> Expected: (Hist[i]) > (TriesPerUnit / N / 3), actual: 0 vs 2184
> /usr/local/google/home/kcc/llvm-project/compiler-rt/lib/fuzzer/tests/FuzzerUnittest.cpp:609: Failure
> Expected: (Hist[i]) > (TriesPerUnit / N / 3), actual: 0 vs 2184
> /usr/local/google/home/kcc/llvm-project/compiler-rt/lib/fuzzer/tests/FuzzerUnittest.cpp:609: Failure
Instead of updating the corpus distribution every time it changes (e.g., FuzzerCorpus.h#L114 and FuzzerCorpus.h#L165), entropic schedules that update by setting a flag. For efficiency, only when (and just before) a new input is chosen, the corpus distribution is actually updated. I had this update in ChooseUnitToMutate which calls ChooseUnitIdxToMutate. Now moved the call to UpdateCorpusDistribution to ChooseUnitIdxToMutate (which is used by the test case).

All 40 fuzzer unit tests pass.


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  https://reviews.llvm.org/D73776/new/

https://reviews.llvm.org/D73776