Index: lib/fuzzer/FuzzerDriver.cpp
===================================================================
--- lib/fuzzer/FuzzerDriver.cpp
+++ lib/fuzzer/FuzzerDriver.cpp
@@ -614,6 +614,7 @@
   Options.PrintNewCovFuncs = Flags.print_funcs;
   Options.PrintFinalStats = Flags.print_final_stats;
   Options.PrintMutationStats = Flags.print_mutation_stats;
+  Options.PrintMutationUsefulness = Flags.print_mutation_usefulness;
   Options.PrintCorpusStats = Flags.print_corpus_stats;
   Options.PrintCoverage = Flags.print_coverage;
   Options.DumpCoverage = Flags.dump_coverage;
@@ -715,6 +716,8 @@
            "***       executed the target code on a fixed set of inputs.\n"
            "***\n");
     F->PrintFinalStats();
+    F->PrintMutationStats();
+    F->PrintMutationUsefulness();
     exit(0);
   }
 
@@ -762,6 +765,8 @@
     Printf("Done %zd runs in %zd second(s)\n", F->getTotalNumberOfRuns(),
            F->secondsSinceProcessStartUp());
   F->PrintFinalStats();
+  F->PrintMutationStats();
+  F->PrintMutationUsefulness();
 
   exit(0);  // Don't let F destroy itself.
 }
Index: lib/fuzzer/FuzzerFlags.def
===================================================================
--- lib/fuzzer/FuzzerFlags.def
+++ lib/fuzzer/FuzzerFlags.def
@@ -154,3 +154,4 @@
 FUZZER_DEPRECATED_FLAG(use_clang_coverage)
 FUZZER_FLAG_STRING(data_flow_trace, "Experimental: use the data flow trace")
 FUZZER_FLAG_INT(print_mutation_stats, 0, "Experimental")
+FUZZER_FLAG_INT(print_mutation_usefulness, 0, "Experimental")
Index: lib/fuzzer/FuzzerInternal.h
===================================================================
--- lib/fuzzer/FuzzerInternal.h
+++ lib/fuzzer/FuzzerInternal.h
@@ -80,6 +80,8 @@
   void CrashResistantMergeInternalStep(const std::string &ControlFilePath);
   MutationDispatcher &GetMD() { return MD; }
   void PrintFinalStats();
+  void PrintMutationStats();
+  void PrintMutationUsefulness();
   void SetMaxInputLen(size_t MaxInputLen);
   void SetMaxMutationLen(size_t MaxMutationLen);
   void RssLimitCallback();
Index: lib/fuzzer/FuzzerLoop.cpp
===================================================================
--- lib/fuzzer/FuzzerLoop.cpp
+++ lib/fuzzer/FuzzerLoop.cpp
@@ -134,6 +134,8 @@
   DumpCurrentUnit("oom-");
   Printf("SUMMARY: libFuzzer: out-of-memory\n");
   PrintFinalStats();
+  PrintMutationStats();
+  PrintMutationUsefulness();
   _Exit(Options.ErrorExitCode); // Stop right now.
 }
 
@@ -195,6 +197,8 @@
 void Fuzzer::DeathCallback() {
   DumpCurrentUnit("crash-");
   PrintFinalStats();
+  PrintMutationStats();
+  PrintMutationUsefulness();
 }
 
 void Fuzzer::StaticAlarmCallback() {
@@ -239,6 +243,8 @@
   Printf("SUMMARY: libFuzzer: deadly signal\n");
   DumpCurrentUnit("crash-");
   PrintFinalStats();
+  PrintMutationStats();
+  PrintMutationUsefulness();
   _Exit(Options.ErrorExitCode); // Stop right now.
 }
 
@@ -253,6 +259,8 @@
   Printf("SUMMARY: libFuzzer: fuzz target exited\n");
   DumpCurrentUnit("crash-");
   PrintFinalStats();
+  PrintMutationStats();
+  PrintMutationUsefulness();
   _Exit(Options.ErrorExitCode);
 }
 
@@ -260,12 +268,16 @@
   if (!GracefulExitRequested) return;
   Printf("==%lu== INFO: libFuzzer: exiting as requested\n", GetPid());
   PrintFinalStats();
+  PrintMutationStats();
+  PrintMutationUsefulness();
   _Exit(0);
 }
 
 void Fuzzer::InterruptCallback() {
   Printf("==%lu== libFuzzer: run interrupted; exiting\n", GetPid());
   PrintFinalStats();
+  PrintMutationStats();
+  PrintMutationUsefulness();
   _Exit(0); // Stop right now, don't perform any at-exit actions.
 }
 
@@ -298,6 +310,8 @@
     PrintStackTrace();
     Printf("SUMMARY: libFuzzer: timeout\n");
     PrintFinalStats();
+    PrintMutationStats();
+    PrintMutationUsefulness();
     _Exit(Options.TimeoutExitCode); // Stop right now.
   }
 }
@@ -314,6 +328,8 @@
   DumpCurrentUnit("oom-");
   Printf("SUMMARY: libFuzzer: out-of-memory\n");
   PrintFinalStats();
+  PrintMutationStats();
+  PrintMutationUsefulness();
   _Exit(Options.ErrorExitCode); // Stop right now.
 }
 
@@ -364,11 +380,18 @@
   Printf("stat::new_units_added:          %zd\n", NumberOfNewUnitsAdded);
   Printf("stat::slowest_unit_time_sec:    %zd\n", TimeOfLongestUnitInSeconds);
   Printf("stat::peak_rss_mb:              %zd\n", GetPeakRSSMb());
+}
 
+void Fuzzer::PrintMutationStats() {
   if (Options.PrintMutationStats)
     MStats->PrintMutationCounts();
 }
 
+void Fuzzer::PrintMutationUsefulness() {
+  if (Options.PrintMutationUsefulness)
+    MStats->PrintMutationUsefulness();
+}
+
 void Fuzzer::SetMaxInputLen(size_t MaxInputLen) {
   assert(this->MaxInputLen == 0); // Can only reset MaxInputLen from 0 to non-0.
   assert(MaxInputLen);
@@ -625,6 +648,8 @@
     CurrentUnitSize = Size;
     DumpCurrentUnit("leak-");
     PrintFinalStats();
+    PrintMutationStats();
+    PrintMutationUsefulness();
     _Exit(Options.ErrorExitCode); // not exit() to disable lsan further on.
   }
 }
@@ -835,6 +860,8 @@
       DumpCurrentUnit("mismatch-");
       Printf("SUMMARY: libFuzzer: equivalence-mismatch\n");
       PrintFinalStats();
+      PrintMutationStats();
+      PrintMutationUsefulness();
       _Exit(Options.ErrorExitCode);
     }
   }
Index: lib/fuzzer/FuzzerMutationStats.h
===================================================================
--- lib/fuzzer/FuzzerMutationStats.h
+++ lib/fuzzer/FuzzerMutationStats.h
@@ -19,6 +19,7 @@
   void PrintMutationCounts();
   void IncTotalMutationCount(MutationType MType);
   void IncUsefulMutationCount(MutationType MType);
+  void PrintMutationUsefulness();
 
 private:
   // A total count of each mutation used in the fuzzing process.
Index: lib/fuzzer/FuzzerMutationStats.cpp
===================================================================
--- lib/fuzzer/FuzzerMutationStats.cpp
+++ lib/fuzzer/FuzzerMutationStats.cpp
@@ -9,31 +9,50 @@
 // Mutate a test input.
 //===----------------------------------------------------------------------===//
 
-#include "FuzzerMutate.h"
 #include "FuzzerMutationStats.h"
 #include "FuzzerIO.h"
+#include "FuzzerMutate.h"
 
 namespace fuzzer {
 
-MutationStats* MStats = new MutationStats();
+MutationStats *MStats = new MutationStats();
 
 void MutationStats::PrintMutationCounts() {
   // Outputs the number of each mutation used
-  Printf("\nTotal Mutations ----------\n");
+  Printf("\nstat::total_mutations:          ");
+  for (int i = 0; i < MaxNumberOfMutationTypes; i++) {
+    if (i < MaxNumberOfMutationTypes-1)
+      Printf("%zd, ", TotalMutations.at(i));
+    else
+      Printf("%zd", TotalMutations.at(i));
+  }
+
+  Printf("\nstat::useful_mutations:         ");
   for (int i = 0; i < MaxNumberOfMutationTypes; i++) {
-    auto current = kMutationNames.find((MutationType) i);
-    Printf("%s: %d\n", current->second.c_str(), TotalMutations.at(i));
+    if (i < MaxNumberOfMutationTypes-1)
+      Printf("%zd, ", UsefulMutations.at(i));
+    else
+      Printf("%zd", UsefulMutations.at(i));
   }
+}
 
-  Printf("\nUseful Mutations ----------\n");
+void MutationStats::PrintMutationUsefulness() {
+  Printf("\nstat::mutation_usefulness:      ");
   for (int i = 0; i < MaxNumberOfMutationTypes; i++) {
-    auto current = kMutationNames.find((MutationType) i);
-    Printf("%s: %d\n", current->second.c_str(), UsefulMutations.at(i));
+    auto Current = kMutationNames.find((MutationType)i);
+    double CurrentRatio =
+        (TotalMutations.at(i) != 0)
+            ? (UsefulMutations.at(i) /
+               static_cast<double>(TotalMutations.at(i)) * 100)
+            : 0;
+    if (i < MaxNumberOfMutationTypes-1)
+      Printf("%.3f, ", Current->second.c_str(), CurrentRatio);
+    else
+      Printf("%.3f", Current->second.c_str(), CurrentRatio);
   }
+  Printf("\n\n");
 }
 
-// Updates the count of mutations (total/useful) depending on type.
-// Types: (0) Total, (1) Useful
 void MutationStats::IncTotalMutationCount(MutationType MType) {
   if ((MType < 0) || MType >= MaxNumberOfMutationTypes)
     return;
@@ -48,4 +67,4 @@
     UsefulMutations[MType]++;
 }
 
-}  // namespace fuzzer
+} // namespace fuzzer
Index: lib/fuzzer/FuzzerOptions.h
===================================================================
--- lib/fuzzer/FuzzerOptions.h
+++ lib/fuzzer/FuzzerOptions.h
@@ -53,6 +53,7 @@
   int PrintNewCovFuncs = 0;
   bool PrintFinalStats = false;
   bool PrintMutationStats = false;
+  bool PrintMutationUsefulness = false;
   bool PrintCorpusStats = false;
   bool PrintCoverage = false;
   bool DumpCoverage = false;