[libFuzzer] change the strategy for -experimental_len_control to grow max_len slower

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@320531 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 4 insertions, 8 deletions

diff --git a/lib/fuzzer/FuzzerLoop.cpp b/lib/fuzzer/FuzzerLoop.cpp
index 6ed48e08b..5b451ca12 100644
--- a/lib/fuzzer/FuzzerLoop.cpp
+++ b/lib/fuzzer/FuzzerLoop.cpp
@@ -567,7 +567,6 @@ void Fuzzer::ReportNewCoverage(InputInfo *II, const Unit &U) {
   NumberOfNewUnitsAdded++;
   CheckExitOnSrcPosOrItem(); // Check only after the unit is saved to corpus.
   LastCorpusUpdateRun = TotalNumberOfRuns;
-  LastCorpusUpdateTime = system_clock::now();
 }
 
 // Tries detecting a memory leak on the particular input that we have just
@@ -758,18 +757,15 @@ void Fuzzer::Loop(const Vector<std::string> &CorpusDirs) {
     // Update TmpMaxMutationLen
     if (Options.ExperimentalLenControl) {
       if (TmpMaxMutationLen < MaxMutationLen &&
-          (TotalNumberOfRuns - LastCorpusUpdateRun >
-               Options.ExperimentalLenControl &&
-           duration_cast<seconds>(Now - LastCorpusUpdateTime).count() >= 1)) {
-        LastCorpusUpdateRun = TotalNumberOfRuns;
-        LastCorpusUpdateTime = Now;
+          TotalNumberOfRuns - LastCorpusUpdateRun >
+              Options.ExperimentalLenControl * Log(TmpMaxMutationLen)) {
         TmpMaxMutationLen =
-            Min(MaxMutationLen,
-                TmpMaxMutationLen + Max(size_t(4), TmpMaxMutationLen / 8));
+            Min(MaxMutationLen, TmpMaxMutationLen + Log(TmpMaxMutationLen));
         if (TmpMaxMutationLen <= MaxMutationLen)
           Printf("#%zd\tTEMP_MAX_LEN: %zd (%zd %zd)\n", TotalNumberOfRuns,
                  TmpMaxMutationLen, Options.ExperimentalLenControl,
                  LastCorpusUpdateRun);
+        LastCorpusUpdateRun = TotalNumberOfRuns;
       }
     } else {
       TmpMaxMutationLen = MaxMutationLen;