[libFuzzer] prototype implementation of recursion-depth coverage features (commented out; real implementation needs to use inlined instrumentation)

llvm-svn: 308577
diff --git a/llvm/lib/Fuzzer/FuzzerTracePC.cpp b/llvm/lib/Fuzzer/FuzzerTracePC.cpp
index ced0a21..07be441 100644
--- a/llvm/lib/Fuzzer/FuzzerTracePC.cpp
+++ b/llvm/lib/Fuzzer/FuzzerTracePC.cpp
@@ -319,6 +319,8 @@
   uint32_t Idx = *Guard;
   __sancov_trace_pc_pcs[Idx] = PC;
   __sancov_trace_pc_guard_8bit_counters[Idx]++;
+  // Uncomment the following line to get stack-depth profiling.
+  // fuzzer::TPC.RecordCurrentStack();
 }
 
 // Best-effort support for -fsanitize-coverage=trace-pc, which is available