Index: tools/llvm-cov/CodeCoverage.cpp
===================================================================
--- tools/llvm-cov/CodeCoverage.cpp
+++ tools/llvm-cov/CodeCoverage.cpp
@@ -32,8 +32,8 @@
 #include "llvm/Support/Process.h"
 #include "llvm/Support/Program.h"
 #include "llvm/Support/ScopedPrinter.h"
-#include "llvm/Support/Threading.h"
 #include "llvm/Support/ThreadPool.h"
+#include "llvm/Support/Threading.h"
 #include "llvm/Support/ToolOutputFile.h"
 
 #include <functional>
@@ -826,6 +826,7 @@
   ViewOpts.ShowOutputDirectory = ShowOutputDirectory;
   ViewOpts.TabSize = TabSize;
   ViewOpts.ProjectTitle = ProjectTitle;
+  ViewOpts.NumThreads = NumThreads;
 
   if (ViewOpts.hasOutputDirectory()) {
     if (auto E = sys::fs::create_directories(ViewOpts.ShowOutputDirectory)) {
Index: tools/llvm-cov/CoverageReport.h
===================================================================
--- tools/llvm-cov/CoverageReport.h
+++ tools/llvm-cov/CoverageReport.h
@@ -44,6 +44,14 @@
                      const CoverageViewOptions &Options,
                      const CoverageFilter &Filters = CoverageFiltersMatchAll());
 
+  static void
+  prepareSingleFileReport(const StringRef &Filename,
+                          const coverage::CoverageMapping *Coverage,
+                          const CoverageViewOptions &Options,
+                          const unsigned LCP,
+                          FileCoverageSummary *FileReport,
+                          const CoverageFilter &Filters);
+
   /// Render file reports for every unique file in the coverage mapping.
   void renderFileReports(raw_ostream &OS) const;
 
Index: tools/llvm-cov/CoverageReport.cpp
===================================================================
--- tools/llvm-cov/CoverageReport.cpp
+++ tools/llvm-cov/CoverageReport.cpp
@@ -16,6 +16,8 @@
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/Support/Format.h"
 #include "llvm/Support/Path.h"
+#include "llvm/Support/ThreadPool.h"
+#include "llvm/Support/Threading.h"
 #include <numeric>
 
 using namespace llvm;
@@ -319,42 +321,60 @@
   }
 }
 
+void CoverageReport::prepareSingleFileReport(const StringRef &Filename,
+    const coverage::CoverageMapping *Coverage,
+    const CoverageViewOptions &Options, const unsigned LCP,
+    FileCoverageSummary *FileReport, const CoverageFilter &Filters) {
+  for (const auto &Group : Coverage->getInstantiationGroups(Filename)) {
+    std::vector<FunctionCoverageSummary> InstantiationSummaries;
+    for (const coverage::FunctionRecord *F : Group.getInstantiations()) {
+      if (!Filters.matches(*Coverage, *F))
+        continue;
+      auto InstantiationSummary = FunctionCoverageSummary::get(*Coverage, *F);
+      FileReport->addInstantiation(InstantiationSummary);
+      InstantiationSummaries.push_back(InstantiationSummary);
+    }
+    if (InstantiationSummaries.empty())
+      continue;
+
+    auto GroupSummary =
+        FunctionCoverageSummary::get(Group, InstantiationSummaries);
+
+    if (Options.Debug)
+      outs() << "InstantiationGroup: " << GroupSummary.Name << " with "
+             << "size = " << Group.size() << "\n";
+
+    FileReport->addFunction(GroupSummary);
+  }
+}
+
 std::vector<FileCoverageSummary> CoverageReport::prepareFileReports(
     const coverage::CoverageMapping &Coverage, FileCoverageSummary &Totals,
     ArrayRef<std::string> Files, const CoverageViewOptions &Options,
     const CoverageFilter &Filters) {
-  std::vector<FileCoverageSummary> FileReports;
   unsigned LCP = getRedundantPrefixLen(Files);
+  auto NumThreads = Options.NumThreads;
 
-  for (StringRef Filename : Files) {
-    FileCoverageSummary Summary(Filename.drop_front(LCP));
-
-    for (const auto &Group : Coverage.getInstantiationGroups(Filename)) {
-      std::vector<FunctionCoverageSummary> InstantiationSummaries;
-      for (const coverage::FunctionRecord *F : Group.getInstantiations()) {
-        if (!Filters.matches(Coverage, *F))
-          continue;
-        auto InstantiationSummary = FunctionCoverageSummary::get(Coverage, *F);
-        Summary.addInstantiation(InstantiationSummary);
-        Totals.addInstantiation(InstantiationSummary);
-        InstantiationSummaries.push_back(InstantiationSummary);
-      }
-      if (InstantiationSummaries.empty())
-        continue;
-
-      auto GroupSummary =
-          FunctionCoverageSummary::get(Group, InstantiationSummaries);
+  // If NumThreads is not specified, auto-detect a good default.
+  if (NumThreads == 0)
+    NumThreads =
+        std::max(1U, std::min(llvm::heavyweight_hardware_concurrency(),
+                              unsigned(Files.size())));
 
-      if (Options.Debug)
-        outs() << "InstantiationGroup: " << GroupSummary.Name << " with "
-               << "size = " << Group.size() << "\n";
+  ThreadPool Pool(NumThreads);
 
-      Summary.addFunction(GroupSummary);
-      Totals.addFunction(GroupSummary);
-    }
+  std::vector<FileCoverageSummary> FileReports;
+  FileReports.reserve(Files.size());
 
-    FileReports.push_back(Summary);
+  for (StringRef Filename : Files) {
+    FileReports.emplace_back(Filename.drop_front(LCP));
+    Pool.async(&CoverageReport::prepareSingleFileReport, Filename,
+               &Coverage, Options, LCP, &FileReports.back(), Filters);
   }
+  Pool.wait();
+
+  for (const auto &FileReport : FileReports)
+    Totals += FileReport;
 
   return FileReports;
 }
Index: tools/llvm-cov/CoverageSummaryInfo.h
===================================================================
--- tools/llvm-cov/CoverageSummaryInfo.h
+++ tools/llvm-cov/CoverageSummaryInfo.h
@@ -116,6 +116,12 @@
   FunctionCoverageInfo(size_t Executed, size_t NumFunctions)
       : Executed(Executed), NumFunctions(NumFunctions) {}
 
+  FunctionCoverageInfo &operator+=(const FunctionCoverageInfo &RHS) {
+    Executed += RHS.Executed;
+    NumFunctions += RHS.NumFunctions;
+    return *this;
+  }
+
   void addFunction(bool Covered) {
     if (Covered)
       ++Executed;
@@ -176,6 +182,14 @@
       : Name(Name), RegionCoverage(), LineCoverage(), FunctionCoverage(),
         InstantiationCoverage() {}
 
+  FileCoverageSummary &operator+=(const FileCoverageSummary &RHS) {
+    RegionCoverage += RHS.RegionCoverage;
+    LineCoverage += RHS.LineCoverage;
+    FunctionCoverage += RHS.FunctionCoverage;
+    InstantiationCoverage += RHS.InstantiationCoverage;
+    return *this;
+  }
+
   void addFunction(const FunctionCoverageSummary &Function) {
     RegionCoverage += Function.RegionCoverage;
     LineCoverage += Function.LineCoverage;
Index: tools/llvm-cov/CoverageViewOptions.h
===================================================================
--- tools/llvm-cov/CoverageViewOptions.h
+++ tools/llvm-cov/CoverageViewOptions.h
@@ -39,6 +39,7 @@
   uint32_t TabSize;
   std::string ProjectTitle;
   std::string CreatedTimeStr;
+  unsigned NumThreads;
 
   /// \brief Change the output's stream color if the colors are enabled.
   ColoredRawOstream colored_ostream(raw_ostream &OS,