[libFuzzer] Fix denominator in the "inputs have DFT" log line.

[Dor1s]

Summary

The number of "inputs have the Data Flow Trace" cannot be greater than
the number of inputs touching the focus function. The existing message is rather
confusing as the same log would mention a greater total number of traces a few
lines above.

[Dor1s]

Small change. PTAL, or I'll land it myself it a day or so :)

[Dor1s]

TBR

[metzman]

Sorry I didn't review this. LGTM

compiler-rt/lib/fuzzer/FuzzerLoop.cpp

for (auto &SF : CorporaFiles) {
       RunOne(U.data(), U.size());
       CheckExitOnSrcPosOrItem();
       TryDetectingAMemoryLeak(U.data(), U.size(),
                               /*DuringInitialCorpusExecution*/ true);
     }
   }
 
   PrintStats("INITED");
-  if (!Options.FocusFunction.empty())
+  if (!Options.FocusFunction.empty()) {
     Printf("INFO: %zd/%zd inputs touch the focus function\n",
            Corpus.NumInputsThatTouchFocusFunction(), Corpus.size());
     if (!Options.DataFlowTrace.empty())
       Printf("INFO: %zd/%zd inputs have the Data Flow Trace\n",
-           Corpus.NumInputsWithDataFlowTrace(), Corpus.size());
+             Corpus.NumInputsWithDataFlowTrace(),
+             Corpus.NumInputsThatTouchFocusFunction());
+  }
 
   if (Corpus.empty() && Options.MaxNumberOfRuns) {
     Printf("ERROR: no interesting inputs were found. "
            "Is the code instrumented for coverage? Exiting.\n");
     exit(1);
   }
 }
 

compiler-rt/test/fuzzer/dataflow.test

 IN_FUZZMU: F1 000010
 IN_FUZZMU: F2 000001
 
 # Test that we can run collect_data_flow on the entire corpus dir
 RUN: rm -rf %t/OUT
 RUN: %t-ThreeFunctionsTest  -collect_data_flow=%t-ThreeFunctionsTestDF -data_flow_trace=%t/OUT %t/IN
 RUN: %t-ThreeFunctionsTest -data_flow_trace=%t/OUT -runs=0 -focus_function=Func2 %t/IN 2>&1 | FileCheck %s --check-prefix=USE_DATA_FLOW_TRACE
 
-
 USE_DATA_FLOW_TRACE: INFO: DataFlowTrace: reading from {{.*}}/OUT
 USE_DATA_FLOW_TRACE: d28cb407e8e1a702c72d25473f0553d3ec172262 => |000001|
 USE_DATA_FLOW_TRACE: INFO: DataFlowTrace: 6 trace files, 3 functions, 1 traces with focus function
 USE_DATA_FLOW_TRACE: INFO: Focus function is set to 'Func2'
+USE_DATA_FLOW_TRACE: INITED
+USE_DATA_FLOW_TRACE: INFO: 2/6 inputs touch the focus function
+USE_DATA_FLOW_TRACE: INFO: 1/2 inputs have the Data Flow Trace
 
 # Test that we can run collect_data_flow on a long input (>2**16 bytes)
 RUN: printf "%0.sA" {1..150001} > %t/IN/very_long_input
 RUN: rm -rf %t/OUT
 RUN: %t-ThreeFunctionsTest  -collect_data_flow=%t-ThreeFunctionsTestDF -data_flow_trace=%t/OUT %t/IN/very_long_input
 RUN: rm %t/IN/very_long_input
 
 # Test that it fails explicitly when an empty corpus is provided.
 RUN: rm -rf %t/IN && mkdir %t/IN
 RUN: not %t-ThreeFunctionsTest  -collect_data_flow=%t-ThreeFunctionsTestDF -data_flow_trace=%t/OUT %t/IN 2>&1 | FileCheck %s --check-prefix=EMPTY_CORPUS
 
 EMPTY_CORPUS: ERROR: can't collect data flow without corpus provided