[libFuzzer] Handle unstable edges by disregarding unstable edges

Summary:
Added a new mode within flag -handle_unstable for new unstable handling algorithm that does the following:
    When an edge is shown as unstable, copy to UnstableCounters the value 0.
    During ApplyUnstableCounters we copy back the value 0 to ModuleInline8bitCounters if the edge was unstable.

This way we would be ignoring completely features that were collected through non-determinism.
Unstable hits would be counted as if it never hit.

Reviewers: metzman, Dor1s, kcc, morehouse

Reviewed By: metzman, morehouse

Subscribers: delcypher, llvm-commits, #sanitizers

Differential Revision: https://reviews.llvm.org/D49684

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@337853 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 2 insertions, 1 deletions

diff --git a/lib/fuzzer/FuzzerDriver.cpp b/lib/fuzzer/FuzzerDriver.cpp
index 4f40d6abf..783474a39 100644
--- a/lib/fuzzer/FuzzerDriver.cpp
+++ b/lib/fuzzer/FuzzerDriver.cpp
@@ -619,7 +619,8 @@ int FuzzerDriver(int *argc, char ***argv, UserCallback Callback) {
   Options.PrintCorpusStats = Flags.print_corpus_stats;
   Options.PrintCoverage = Flags.print_coverage;
   Options.PrintUnstableStats = Flags.print_unstable_stats;
-  if (Flags.handle_unstable)
+  if (Flags.handle_unstable == TracePC::MinUnstable ||
+      Flags.handle_unstable == TracePC::ZeroUnstable)
     Options.HandleUnstable = Flags.handle_unstable;
   Options.DumpCoverage = Flags.dump_coverage;
   if (Flags.exit_on_src_pos)