diff --git a/clang/lib/CodeGen/CoverageMappingGen.cpp b/clang/lib/CodeGen/CoverageMappingGen.cpp
diff --git a/clang/lib/CodeGen/CoverageMappingGen.h b/clang/lib/CodeGen/CoverageMappingGen.h
@@ -95,6 +95,7 @@ class CoverageSourceInfo : public PPCallbacks,
 namespace CodeGen {
 
 class CodeGenModule;
+class CounterPair;
 
 namespace MCDC {
 struct State;
@@ -158,7 +159,7 @@ class CoverageMappingGen {
   CoverageMappingModuleGen &CVM;
   SourceManager &SM;
   const LangOptions &LangOpts;
-  llvm::DenseMap<const Stmt *, unsigned> *CounterMap;
+  llvm::DenseMap<const Stmt *, CounterPair> *CounterMap;
   MCDC::State *MCDCState;
 
 public:
@@ -169,7 +170,7 @@ class CoverageMappingGen {
 
   CoverageMappingGen(CoverageMappingModuleGen &CVM, SourceManager &SM,
                      const LangOptions &LangOpts,
-                     llvm::DenseMap<const Stmt *, unsigned> *CounterMap,
+                     llvm::DenseMap<const Stmt *, CounterPair> *CounterMap,
                      MCDC::State *MCDCState)
       : CVM(CVM), SM(SM), LangOpts(LangOpts), CounterMap(CounterMap),
         MCDCState(MCDCState) {}

diff --git a/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h b/llvm/include/llvm/ProfileData/Coverage/CoverageMapping.h
@@ -34,6 +34,7 @@
 #include <cassert>
 #include <cstdint>
 #include <iterator>
+#include <map>
 #include <memory>
 #include <sstream>
 #include <string>
@@ -213,6 +214,9 @@ class CounterExpressionBuilder {
   /// Return a counter that represents the expression that subtracts RHS from
   /// LHS.
   Counter subtract(Counter LHS, Counter RHS, bool Simplify = true);
+
+  using ReplaceMap = std::map<Counter, Counter>;
+  Counter replace(Counter C, const ReplaceMap &Map);
 };
 
 using LineColPair = std::pair<unsigned, unsigned>;

diff --git a/llvm/lib/ProfileData/Coverage/CoverageMapping.cpp b/llvm/lib/ProfileData/Coverage/CoverageMapping.cpp
@@ -135,6 +135,32 @@ Counter CounterExpressionBuilder::subtract(Counter LHS, Counter RHS,
   return Simplify ? simplify(Cnt) : Cnt;
 }
 
+Counter CounterExpressionBuilder::replace(Counter C, const ReplaceMap &Map) {
+  auto I = Map.find(C);
+  if (I != Map.end())
+    return I->second;
+
+  if (!C.isExpression())
+    return C;
+
+  auto CE = Expressions[C.getExpressionID()];
+  auto NewLHS = replace(CE.LHS, Map);
+  auto NewRHS = replace(CE.RHS, Map);
+  switch (CE.Kind) {
+  case CounterExpression::Subtract:
+    C = subtract(NewLHS, NewRHS);
+    break;
+  case CounterExpression::Add:
+    C = add(NewLHS, NewRHS);
+    break;
+  }
+
+  if ((I = Map.find(C)) != Map.end())
+    return I->second;
+
+  return C;
+}
+
 void CounterMappingContext::dump(const Counter &C, raw_ostream &OS) const {
   switch (C.getKind()) {
   case Counter::Zero:
@@ -608,6 +634,10 @@ static unsigned getMaxCounterID(const CounterMappingContext &Ctx,
   unsigned MaxCounterID = 0;
   for (const auto &Region : Record.MappingRegions) {
     MaxCounterID = std::max(MaxCounterID, Ctx.getMaxCounterID(Region.Count));
+    if (Region.Kind == CounterMappingRegion::BranchRegion ||
+        Region.Kind == CounterMappingRegion::MCDCBranchRegion)
+      MaxCounterID =
+          std::max(MaxCounterID, Ctx.getMaxCounterID(Region.FalseCount));
   }
   return MaxCounterID;
 }