1 files changed, 4 insertions, 27 deletions

diff --git a/llvm/lib/Fuzzer/FuzzerLoop.cpp b/llvm/lib/Fuzzer/FuzzerLoop.cpp
index b68185ba3b5..0edc21db3ac 100644
--- a/llvm/lib/Fuzzer/FuzzerLoop.cpp
+++ b/llvm/lib/Fuzzer/FuzzerLoop.cpp
@@ -374,7 +374,6 @@ void Fuzzer::RereadOutputCorpus(size_t MaxSize) {
     if (!Corpus.HasUnit(X)) {
       if (RunOne(X)) {
         Corpus.push_back(X);
-        UpdateCorpusDistribution();
         PrintStats("RELOAD");
       }
     }
@@ -404,7 +403,6 @@ void Fuzzer::ShuffleAndMinimize(UnitVector *InitialCorpus) {
     TryDetectingAMemoryLeak(U.data(), U.size(),
                             /*DuringInitialCorpusExecution*/ true);
   }
-  UpdateCorpusDistribution();
   PrintStats("INITED");
   if (Corpus.empty()) {
     Printf("ERROR: no interesting inputs were found. "
@@ -543,7 +541,6 @@ void Fuzzer::PrintNewPCs() {
 
 void Fuzzer::ReportNewCoverage(const Unit &U) {
   Corpus.push_back(U);
-  UpdateCorpusDistribution();
   MD.RecordSuccessfulMutationSequence();
   PrintStatusForNewUnit(U);
   WriteToOutputCorpus(U);
@@ -656,8 +653,9 @@ void Fuzzer::MutateAndTestOne() {
   LazyAllocateCurrentUnitData();
   MD.StartMutationSequence();
 
-  auto &U = ChooseUnitToMutate();
-  ComputeSHA1(U.data(), U.size(), BaseSha1);  // Remember where we started.
+  const auto &II = Corpus.ChooseUnitToMutate(MD.GetRand());
+  const auto &U = II.U;
+  memcpy(BaseSha1, II.Sha1, sizeof(BaseSha1));
   assert(CurrentUnitData);
   size_t Size = U.size();
   assert(Size <= Options.MaxLen && "Oversized Unit");
@@ -667,8 +665,7 @@ void Fuzzer::MutateAndTestOne() {
     size_t NewSize = 0;
     NewSize = MD.Mutate(CurrentUnitData, Size, Options.MaxLen);
     assert(NewSize > 0 && "Mutator returned empty unit");
-    assert(NewSize <= Options.MaxLen &&
-           "Mutator return overisized unit");
+    assert(NewSize <= Options.MaxLen && "Mutator return overisized unit");
     Size = NewSize;
     if (i == 0)
       StartTraceRecording();
@@ -679,16 +676,6 @@ void Fuzzer::MutateAndTestOne() {
   }
 }
 
-// Returns an index of random unit from the corpus to mutate.
-// Hypothesis: units added to the corpus last are more likely to be interesting.
-// This function gives more weight to the more recent units.
-size_t Fuzzer::ChooseUnitIdxToMutate() {
-  size_t Idx =
-      static_cast<size_t>(CorpusDistribution(MD.GetRand().Get_mt19937()));
-  assert(Idx < Corpus.size());
-  return Idx;
-}
-
 void Fuzzer::ResetCoverage() {
   ResetEdgeCoverage();
   MaxCoverage.Reset();
@@ -720,16 +707,6 @@ void Fuzzer::Loop() {
   MD.PrintRecommendedDictionary();
 }
 
-void Fuzzer::UpdateCorpusDistribution() {
-  size_t N = Corpus.size();
-  std::vector<double> Intervals(N + 1);
-  std::vector<double> Weights(N);
-  std::iota(Intervals.begin(), Intervals.end(), 0);
-  std::iota(Weights.begin(), Weights.end(), 1);
-  CorpusDistribution = std::piecewise_constant_distribution<double>(
-      Intervals.begin(), Intervals.end(), Weights.begin());
-}
-
 } // namespace fuzzer
 
 extern "C" {