[libFuzzer] Implement stat::stability_rate based on the percentage of unstable edges.

Summary:
Created a -print_unstable_stats flag.
When -print_unstable_stats=1, we run it 2 more times on interesting inputs poisoning unstable edges in an array.
On program termination, we run PrintUnstableStats() which will print a line with a stability percentage like AFL does.

Patch by Kyungtak Woo (@kevinwkt).

Reviewers: metzman, Dor1s, kcc, morehouse

Reviewed By: metzman, Dor1s, morehouse

Subscribers: delcypher, llvm-commits, #sanitizers, kcc, morehouse, Dor1s

Differential Revision: https://reviews.llvm.org/D49212

llvm-svn: 337187

1 files changed, 1 insertions, 0 deletions

diff --git a/compiler-rt/lib/fuzzer/FuzzerDriver.cpp b/compiler-rt/lib/fuzzer/FuzzerDriver.cpp
index ff2a639ac4a..9375925b2c9 100644
--- a/compiler-rt/lib/fuzzer/FuzzerDriver.cpp
+++ b/compiler-rt/lib/fuzzer/FuzzerDriver.cpp
@@ -617,6 +617,7 @@ int FuzzerDriver(int *argc, char ***argv, UserCallback Callback) {
   Options.PrintFinalStats = Flags.print_final_stats;
   Options.PrintCorpusStats = Flags.print_corpus_stats;
   Options.PrintCoverage = Flags.print_coverage;
+  Options.PrintUnstableStats = Flags.print_unstable_stats;
   Options.DumpCoverage = Flags.dump_coverage;
   if (Flags.exit_on_src_pos)
     Options.ExitOnSrcPos = Flags.exit_on_src_pos;