Index: docs/CommandGuide/llvm-cov.rst
===================================================================
--- docs/CommandGuide/llvm-cov.rst
+++ docs/CommandGuide/llvm-cov.rst
@@ -419,3 +419,16 @@
 .. option:: -ignore-filename-regex=<PATTERN>
 
  Skip source code files with file paths that match the given regular expression.
+
+ .. option:: -skip-expansions
+
+ Skip exporting macro expansion coverage data.
+
+ .. option:: -skip-functions
+
+ Skip exporting per-function coverage data.
+
+ .. option:: -num-threads=N, -j=N
+
+ Use N threads to export coverage data. When N=0, llvm-cov auto-detects an
+ appropriate number of threads to use. This is the default.
Index: test/tools/llvm-cov/export_functions.test
===================================================================
--- /dev/null
+++ test/tools/llvm-cov/export_functions.test
@@ -0,0 +1,10 @@
+# Test that llvm-cov export produces function data by default and that it can be
+# turned off with a flag.
+
+RUN: llvm-cov export %S/Inputs/report.covmapping -instr-profile %S/Inputs/report.profdata 2>&1 | FileCheck %s
+RUN: llvm-cov export %S/Inputs/report.covmapping -instr-profile %S/Inputs/report.profdata -skip-functions 2>&1 | FileCheck -check-prefix=SKIP-FUNCTIONS %s
+
+CHECK: "functions":[
+SKIP-FUNCTIONS-NOT: "functions":[
+
+
Index: test/tools/llvm-cov/showExpansions.cpp
===================================================================
--- test/tools/llvm-cov/showExpansions.cpp
+++ test/tools/llvm-cov/showExpansions.cpp
@@ -25,3 +25,6 @@
   return 0;
 }
 // RUN: llvm-cov export %S/Inputs/showExpansions.covmapping -instr-profile %S/Inputs/showExpansions.profdata 2>&1 | FileCheck %S/Inputs/showExpansions.json
+
+// RUN: llvm-cov export %S/Inputs/showExpansions.covmapping -instr-profile %S/Inputs/showExpansions.profdata -skip-expansions 2>&1 | FileCheck %s -check-prefix=SKIP-EXPANSIONS
+// SKIP-EXPANSIONS-NOT: "expansions"
Index: tools/llvm-cov/CodeCoverage.cpp
===================================================================
--- tools/llvm-cov/CodeCoverage.cpp
+++ tools/llvm-cov/CodeCoverage.cpp
@@ -1006,10 +1006,23 @@
 int CodeCoverageTool::doExport(int argc, const char **argv,
                                CommandLineParserType commandLineParser) {
 
+  cl::OptionCategory ExportCategory("Exporting options");
+
+  cl::opt<bool> SkipExpansions("skip-expansions", cl::Optional,
+                               cl::desc("Don't export expanded source regions"),
+                               cl::cat(ExportCategory));
+
+  cl::opt<bool> SkipFunctions("skip-functions", cl::Optional,
+                              cl::desc("Don't export per-function data"),
+                              cl::cat(ExportCategory));
+
   auto Err = commandLineParser(argc, argv);
   if (Err)
     return Err;
 
+  ViewOpts.SkipExpansions = SkipExpansions;
+  ViewOpts.SkipFunctions = SkipFunctions;
+
   if (ViewOpts.Format != CoverageViewOptions::OutputFormat::Text &&
       ViewOpts.Format != CoverageViewOptions::OutputFormat::Lcov) {
     error("Coverage data can only be exported as textual JSON or an "
Index: tools/llvm-cov/CoverageExporterJson.cpp
===================================================================
--- tools/llvm-cov/CoverageExporterJson.cpp
+++ tools/llvm-cov/CoverageExporterJson.cpp
@@ -42,7 +42,14 @@
 
 #include "CoverageExporterJson.h"
 #include "CoverageReport.h"
+#include "llvm/ADT/Optional.h"
+#include "llvm/ADT/StringRef.h"
 #include "llvm/Support/JSON.h"
+#include "llvm/Support/ThreadPool.h"
+#include "llvm/Support/Threading.h"
+#include <algorithm>
+#include <mutex>
+#include <utility>
 
 /// The semantic version combined as a string.
 #define LLVM_COVERAGE_EXPORT_JSON_STR "2.0.0"
@@ -127,13 +134,15 @@
 json::Object renderFile(const coverage::CoverageMapping &Coverage,
                         const std::string &Filename,
                         const FileCoverageSummary &FileReport,
-                        bool ExportSummaryOnly) {
+                        const CoverageViewOptions &Options) {
   json::Object File({{"filename", Filename}});
-  if (!ExportSummaryOnly) {
+  if (!Options.ExportSummaryOnly) {
     // Calculate and render detailed coverage information for given file.
     auto FileCoverage = Coverage.getCoverageForFile(Filename);
     File["segments"] = renderFileSegments(FileCoverage, FileReport);
-    File["expansions"] = renderFileExpansions(FileCoverage, FileReport);
+    if (!Options.SkipExpansions) {
+      File["expansions"] = renderFileExpansions(FileCoverage, FileReport);
+    }
   }
   File["summary"] = renderSummary(FileReport);
   return File;
@@ -142,11 +151,28 @@
 json::Array renderFiles(const coverage::CoverageMapping &Coverage,
                         ArrayRef<std::string> SourceFiles,
                         ArrayRef<FileCoverageSummary> FileReports,
-                        bool ExportSummaryOnly) {
+                        const CoverageViewOptions &Options) {
+  auto NumThreads = Options.NumThreads;
+  if (NumThreads == 0) {
+    NumThreads = std::max(1U, std::min(llvm::heavyweight_hardware_concurrency(),
+                                       unsigned(SourceFiles.size())));
+  }
+  ThreadPool Pool(NumThreads);
   json::Array FileArray;
-  for (unsigned I = 0, E = SourceFiles.size(); I < E; ++I)
-    FileArray.push_back(renderFile(Coverage, SourceFiles[I], FileReports[I],
-                                   ExportSummaryOnly));
+  std::mutex FileArrayMutex;
+
+  for (unsigned I = 0, E = SourceFiles.size(); I < E; ++I) {
+    auto &SourceFile = SourceFiles[I];
+    auto &FileReport = FileReports[I];
+    Pool.async([&] {
+      auto File = renderFile(Coverage, SourceFile, FileReport, Options);
+      {
+        std::lock_guard<std::mutex> Lock(FileArrayMutex);
+        FileArray.push_back(std::move(File));
+      }
+    });
+  }
+  Pool.wait();
   return FileArray;
 }
 
@@ -177,12 +203,22 @@
   FileCoverageSummary Totals = FileCoverageSummary("Totals");
   auto FileReports = CoverageReport::prepareFileReports(Coverage, Totals,
                                                         SourceFiles, Options);
-  auto Export =
-      json::Object({{"files", renderFiles(Coverage, SourceFiles, FileReports,
-                                          Options.ExportSummaryOnly)},
-                    {"totals", renderSummary(Totals)}});
-  // Skip functions-level information for summary-only export mode.
-  if (!Options.ExportSummaryOnly)
+  auto Files = renderFiles(Coverage, SourceFiles, FileReports, Options);
+  // Sort files in order of their names.
+  std::sort(Files.begin(), Files.end(),
+    [](const json::Value &A, const json::Value &B) {
+      const json::Object *ObjA = A.getAsObject();
+      const json::Object *ObjB = B.getAsObject();
+      assert(ObjA != nullptr && "Value A was not an Object");
+      assert(ObjB != nullptr && "Value B was not an Object");
+      const StringRef FilenameA = ObjA->getString("filename").getValue();
+      const StringRef FilenameB = ObjB->getString("filename").getValue();
+      return FilenameA.compare(FilenameB) < 0;
+    });
+  auto Export = json::Object(
+      {{"files", std::move(Files)}, {"totals", renderSummary(Totals)}});
+  // Skip functions-level information  if necessary.
+  if (!Options.ExportSummaryOnly && !Options.SkipFunctions)
     Export["functions"] = renderFunctions(Coverage.getCoveredFunctions());
 
   auto ExportArray = json::Array({std::move(Export)});
Index: tools/llvm-cov/CoverageViewOptions.h
===================================================================
--- tools/llvm-cov/CoverageViewOptions.h
+++ tools/llvm-cov/CoverageViewOptions.h
@@ -34,6 +34,8 @@
   bool ShowRegionSummary;
   bool ShowInstantiationSummary;
   bool ExportSummaryOnly;
+  bool SkipExpansions;
+  bool SkipFunctions;
   OutputFormat Format;
   std::string ShowOutputDirectory;
   std::vector<std::string> DemanglerOpts;