Reland "[Coverage][llvm-cov] Enable MC/DC Support in LLVM Source-based Code Coverage (2/3)"

Part 2 of 3. This includes the Visualization and Evaluation components.

Differential Revision: https://reviews.llvm.org/D138847

Author: evodius96

clang/lib/CodeGen/CoverageMappingGen.cpp

@@ -1623,8 +1623,12 @@ static void dump(llvm::raw_ostream &OS, StringRef FunctionName,
       OS << "Gap,";
       break;
     case CounterMappingRegion::BranchRegion:
+    case CounterMappingRegion::MCDCBranchRegion:
       OS << "Branch,";
       break;
+    case CounterMappingRegion::MCDCDecisionRegion:
+      OS << "Decision,";
+      break;
     }
 
     OS << "File " << R.FileID << ", " << R.LineStart << ":" << R.ColumnStart

llvm/docs/CommandGuide/llvm-cov.rst

@@ -222,6 +222,11 @@ OPTIONS
  Show coverage for branch conditions in terms of either count or percentage.
  The supported views are: "count", "percent".
 
+.. option:: -show-mcdc
+
+ Show modified condition/decision coverage (MC/DC) for each applicable boolean
+ expression.
+
 .. option:: -show-line-counts
 
  Show the execution counts for each line. Defaults to true, unless another
@@ -426,6 +431,10 @@ OPTIONS
 
  Show statistics for all branch conditions. Defaults to true.
 
+.. option:: -show-mcdc-summary
+
+ Show MC/DC statistics. Defaults to false.
+
 .. option:: -show-functions
 
  Show coverage summaries for each function. Defaults to false.