diff --git a/llvm/test/tools/sancov/merge.test b/llvm/test/tools/sancov/merge.test
--- a/llvm/test/tools/sancov/merge.test
+++ b/llvm/test/tools/sancov/merge.test
@@ -3,62 +3,81 @@
 RUN: sancov -merge %p/Inputs/test-linux_x86_64.0.symcov %p/Inputs/test-linux_x86_64.1.symcov| FileCheck --check-prefix=MERGE2 %s
 
 MERGE1: {
-MERGE1-NEXT:   "covered-points" : ["4e132b", "4e1472", "4e1520", "4e1553", "4e1586"],
-MERGE1-NEXT:   "binary-hash" : "BB3CDD5045AED83906F6ADCC1C4DAF7E2596A6B5",
-MERGE1-NEXT:   "point-symbol-info" : {
-MERGE1-NEXT:     "test/tools/sancov/Inputs/foo.cpp" : {
-MERGE1-NEXT:       "foo()" : {
-MERGE1-NEXT:         "4e178c" : "5:0"
+MERGE1-NEXT:   "covered-points": [
+MERGE1-NEXT:     "4e132b",
+MERGE1-NEXT:     "4e1472",
+MERGE1-NEXT:     "4e1520",
+MERGE1-NEXT:     "4e1553",
+MERGE1-NEXT:     "4e1586"
+MERGE1-NEXT:   ],
+MERGE1-NEXT:   "binary-hash": "BB3CDD5045AED83906F6ADCC1C4DAF7E2596A6B5",
+MERGE1-NEXT:   "point-symbol-info": {
+MERGE1-NEXT:     "test/tools/sancov/Inputs/foo.cpp": {
+MERGE1-NEXT:       "foo()": {
+MERGE1-NEXT:         "4e178c": "5:0"
 MERGE1-NEXT:       }
 MERGE1-NEXT:     },
-MERGE1-NEXT:     "test/tools/sancov/Inputs/test.cpp" : {
-MERGE1-NEXT:       "bar(std::string)" : {
-MERGE1-NEXT:         "4e132b" : "12:0"
+MERGE1-NEXT:     "test/tools/sancov/Inputs/test.cpp": {
+MERGE1-NEXT:       "bar(std::string)": {
+MERGE1-NEXT:         "4e132b": "12:0"
 MERGE1-NEXT:       },
-MERGE1-NEXT:       "main" : {
-MERGE1-NEXT:         "4e1472" : "14:0",
-MERGE1-NEXT:         "4e14c2" : "16:9",
-MERGE1-NEXT:         "4e1520" : "17:5",
-MERGE1-NEXT:         "4e1553" : "17:5",
-MERGE1-NEXT:         "4e1586" : "17:5",
-MERGE1-NEXT:         "4e1635" : "19:1",
-MERGE1-NEXT:         "4e1690" : "17:5"
+MERGE1-NEXT:       "main": {
+MERGE1-NEXT:         "4e1472": "14:0",
+MERGE1-NEXT:         "4e14c2": "16:9",
+MERGE1-NEXT:         "4e1520": "17:5",
+MERGE1-NEXT:         "4e1553": "17:5",
+MERGE1-NEXT:         "4e1586": "17:5",
+MERGE1-NEXT:         "4e1635": "19:1",
+MERGE1-NEXT:         "4e1690": "17:5"
 MERGE1-NEXT:       }
 MERGE1-NEXT:     }
 MERGE1-NEXT:   }
 MERGE1-NEXT: }
 
 MERGE2: {
-MERGE2-NEXT:   "covered-points" : ["04e132b", "04e1472", "04e1520", "04e1553", "04e1586", "14e132b", "14e1472", "14e14c2", "14e1520", "14e1553", "14e1586", "14e178c"],
-MERGE2-NEXT:   "point-symbol-info" : {
-MERGE2-NEXT:     "test/tools/sancov/Inputs/foo.cpp" : {
-MERGE2-NEXT:      "foo()" : {
-MERGE2-NEXT:         "04e178c" : "5:0",
-MERGE2-NEXT:         "14e178c" : "5:0"
+MERGE2-NEXT:   "covered-points": [
+MERGE2-NEXT:     "04e132b",
+MERGE2-NEXT:     "04e1472",
+MERGE2-NEXT:     "04e1520",
+MERGE2-NEXT:     "04e1553",
+MERGE2-NEXT:     "04e1586",
+MERGE2-NEXT:     "14e132b",
+MERGE2-NEXT:     "14e1472",
+MERGE2-NEXT:     "14e14c2",
+MERGE2-NEXT:     "14e1520",
+MERGE2-NEXT:     "14e1553",
+MERGE2-NEXT:     "14e1586",
+MERGE2-NEXT:     "14e178c"
+MERGE2-NEXT:   ],
+MERGE2-NEXT:   "binary-hash": "",
+MERGE2-NEXT:   "point-symbol-info": {
+MERGE2-NEXT:     "test/tools/sancov/Inputs/foo.cpp": {
+MERGE2-NEXT:       "foo()": {
+MERGE2-NEXT:         "04e178c": "5:0",
+MERGE2-NEXT:         "14e178c": "5:0"
 MERGE2-NEXT:       }
 MERGE2-NEXT:     },
-MERGE2-NEXT:     "test/tools/sancov/Inputs/test.cpp" : {
-MERGE2-NEXT:       "bar(std::string)" : {
-MERGE2-NEXT:         "04e132b" : "12:0",
-MERGE2-NEXT:         "14e132b" : "12:0"
+MERGE2-NEXT:     "test/tools/sancov/Inputs/test.cpp": {
+MERGE2-NEXT:       "bar(std::string)": {
+MERGE2-NEXT:         "04e132b": "12:0",
+MERGE2-NEXT:         "14e132b": "12:0"
 MERGE2-NEXT:       },
-MERGE2-NEXT:       "main" : {
-MERGE2-NEXT:         "04e1472" : "14:0",
-MERGE2-NEXT:         "04e14c2" : "16:9",
-MERGE2-NEXT:         "04e1520" : "17:5",
-MERGE2-NEXT:         "04e1553" : "17:5",
-MERGE2-NEXT:         "04e1586" : "17:5",
-MERGE2-NEXT:         "04e1635" : "19:1",
-MERGE2-NEXT:         "04e1690" : "17:5",
-MERGE2-NEXT:         "14e1472" : "14:0",
-MERGE2-NEXT:         "14e14c2" : "16:9",
-MERGE2-NEXT:         "14e1520" : "17:5",
-MERGE2-NEXT:         "14e1553" : "17:5",
-MERGE2-NEXT:         "14e1586" : "17:5",
-MERGE2-NEXT:         "14e1635" : "19:1",
-MERGE2-NEXT:         "14e1690" : "17:5"
+MERGE2-NEXT:       "main": {
+MERGE2-NEXT:         "04e1472": "14:0",
+MERGE2-NEXT:         "04e14c2": "16:9",
+MERGE2-NEXT:         "04e1520": "17:5",
+MERGE2-NEXT:         "04e1553": "17:5",
+MERGE2-NEXT:         "04e1586": "17:5",
+MERGE2-NEXT:         "04e1635": "19:1",
+MERGE2-NEXT:         "04e1690": "17:5",
+MERGE2-NEXT:         "14e1472": "14:0",
+MERGE2-NEXT:         "14e14c2": "16:9",
+MERGE2-NEXT:         "14e1520": "17:5",
+MERGE2-NEXT:         "14e1553": "17:5",
+MERGE2-NEXT:         "14e1586": "17:5",
+MERGE2-NEXT:         "14e1635": "19:1",
+MERGE2-NEXT:         "14e1690": "17:5"
 MERGE2-NEXT:       }
 MERGE2-NEXT:     }
 MERGE2-NEXT:   }
 MERGE2-NEXT: }
-
diff --git a/llvm/test/tools/sancov/symbolize.test b/llvm/test/tools/sancov/symbolize.test
--- a/llvm/test/tools/sancov/symbolize.test
+++ b/llvm/test/tools/sancov/symbolize.test
@@ -2,23 +2,28 @@
 RUN: sancov -symbolize -strip_path_prefix="llvm/" %p/Inputs/test-linux_x86_64 %p/Inputs/test-linux_x86_64.0.sancov | FileCheck %s
 
 CHECK: {
-CHECK-NEXT:  "covered-points" : ["4e132b", "4e1472", "4e1520", "4e1553", "4e1586"],
-CHECK-NEXT:  "binary-hash" : "BB3CDD5045AED83906F6ADCC1C4DAF7E2596A6B5",
-CHECK-NEXT:  "point-symbol-info" : {
-CHECK-NEXT:   "test/tools/sancov/Inputs/test.cpp" : {
-CHECK-NEXT:     "bar(std::string)" : {
-CHECK-NEXT:       "4e132b" : "12:0"
+CHECK-NEXT:  "covered-points": [
+CHECK-NEXT:    "4e132b",
+CHECK-NEXT:    "4e1472",
+CHECK-NEXT:    "4e1520",
+CHECK-NEXT:    "4e1553",
+CHECK-NEXT:    "4e1586"
+CHECK-NEXT:  ],
+CHECK-NEXT:  "binary-hash": "BB3CDD5045AED83906F6ADCC1C4DAF7E2596A6B5",
+CHECK-NEXT:  "point-symbol-info": {
+CHECK-NEXT:    "test/tools/sancov/Inputs/test.cpp": {
+CHECK-NEXT:      "bar(std::string)": {
+CHECK-NEXT:        "4e132b": "12:0"
 CHECK-NEXT:      },
-CHECK-NEXT:      "main" : {
-CHECK-NEXT:        "4e1472" : "14:0",
-CHECK-NEXT:        "4e14c2" : "16:9",
-CHECK-NEXT:        "4e1520" : "17:5",
-CHECK-NEXT:        "4e1553" : "17:5",
-CHECK-NEXT:        "4e1586" : "17:5",
-CHECK-NEXT:        "4e1635" : "19:1",
-CHECK-NEXT:        "4e1690" : "17:5"
+CHECK-NEXT:      "main": {
+CHECK-NEXT:        "4e1472": "14:0",
+CHECK-NEXT:        "4e14c2": "16:9",
+CHECK-NEXT:        "4e1520": "17:5",
+CHECK-NEXT:        "4e1553": "17:5",
+CHECK-NEXT:        "4e1586": "17:5",
+CHECK-NEXT:        "4e1635": "19:1",
+CHECK-NEXT:        "4e1690": "17:5"
 CHECK-NEXT:      }
 CHECK-NEXT:    }
 CHECK-NEXT:  }
 CHECK-NEXT:}
-
diff --git a/llvm/test/tools/sancov/symbolize_noskip_dead_files.test b/llvm/test/tools/sancov/symbolize_noskip_dead_files.test
--- a/llvm/test/tools/sancov/symbolize_noskip_dead_files.test
+++ b/llvm/test/tools/sancov/symbolize_noskip_dead_files.test
@@ -2,28 +2,33 @@
 RUN: sancov -symbolize -skip-dead-files=0 -strip_path_prefix="llvm/" %p/Inputs/test-linux_x86_64 %p/Inputs/test-linux_x86_64.0.sancov | FileCheck %s
 
 CHECK: {
-CHECK-NEXT:  "covered-points" : ["4e132b", "4e1472", "4e1520", "4e1553", "4e1586"],
-CHECK-NEXT:  "binary-hash" : "BB3CDD5045AED83906F6ADCC1C4DAF7E2596A6B5",
-CHECK-NEXT:  "point-symbol-info" : {
-CHECK-NEXT:    "test/tools/sancov/Inputs/foo.cpp" : {
-CHECK-NEXT:      "foo()" : {
-CHECK-NEXT:        "4e178c" : "5:0"
-CHECK-NEXT:     }
-CHECK-NEXT:   },
-CHECK-NEXT:   "test/tools/sancov/Inputs/test.cpp" : {
-CHECK-NEXT:     "bar(std::string)" : {
-CHECK-NEXT:       "4e132b" : "12:0"
+CHECK-NEXT:  "covered-points": [
+CHECK-NEXT:    "4e132b",
+CHECK-NEXT:    "4e1472",
+CHECK-NEXT:    "4e1520",
+CHECK-NEXT:    "4e1553",
+CHECK-NEXT:    "4e1586"
+CHECK-NEXT:  ],
+CHECK-NEXT:  "binary-hash": "BB3CDD5045AED83906F6ADCC1C4DAF7E2596A6B5",
+CHECK-NEXT:  "point-symbol-info": {
+CHECK-NEXT:    "test/tools/sancov/Inputs/foo.cpp": {
+CHECK-NEXT:      "foo()": {
+CHECK-NEXT:        "4e178c": "5:0"
+CHECK-NEXT:      }
+CHECK-NEXT:    },
+CHECK-NEXT:    "test/tools/sancov/Inputs/test.cpp": {
+CHECK-NEXT:      "bar(std::string)": {
+CHECK-NEXT:        "4e132b": "12:0"
 CHECK-NEXT:      },
-CHECK-NEXT:      "main" : {
-CHECK-NEXT:        "4e1472" : "14:0",
-CHECK-NEXT:        "4e14c2" : "16:9",
-CHECK-NEXT:        "4e1520" : "17:5",
-CHECK-NEXT:        "4e1553" : "17:5",
-CHECK-NEXT:        "4e1586" : "17:5",
-CHECK-NEXT:        "4e1635" : "19:1",
-CHECK-NEXT:        "4e1690" : "17:5"
+CHECK-NEXT:      "main": {
+CHECK-NEXT:        "4e1472": "14:0",
+CHECK-NEXT:        "4e14c2": "16:9",
+CHECK-NEXT:        "4e1520": "17:5",
+CHECK-NEXT:        "4e1553": "17:5",
+CHECK-NEXT:        "4e1586": "17:5",
+CHECK-NEXT:        "4e1635": "19:1",
+CHECK-NEXT:        "4e1690": "17:5"
 CHECK-NEXT:      }
 CHECK-NEXT:    }
 CHECK-NEXT:  }
 CHECK-NEXT:}
-
diff --git a/llvm/tools/sancov/sancov.cpp b/llvm/tools/sancov/sancov.cpp
--- a/llvm/tools/sancov/sancov.cpp
+++ b/llvm/tools/sancov/sancov.cpp
@@ -31,6 +31,7 @@
 #include "llvm/Support/Errc.h"
 #include "llvm/Support/ErrorOr.h"
 #include "llvm/Support/FileSystem.h"
+#include "llvm/Support/JSON.h"
 #include "llvm/Support/MD5.h"
 #include "llvm/Support/ManagedStatic.h"
 #include "llvm/Support/MemoryBuffer.h"
@@ -284,87 +285,6 @@
   return OS;
 }
 
-// Helper for writing out JSON. Handles indents and commas using
-// scope variables for objects and arrays.
-class JSONWriter {
-public:
-  JSONWriter(raw_ostream &Out) : OS(Out) {}
-  JSONWriter(const JSONWriter &) = delete;
-  ~JSONWriter() { OS << "\n"; }
-
-  void operator<<(StringRef S) { printJSONStringLiteral(S, OS); }
-
-  // Helper RAII class to output JSON objects.
-  class Object {
-  public:
-    Object(JSONWriter *W, raw_ostream &OS) : W(W), OS(OS) {
-      OS << "{";
-      W->Indent++;
-    }
-    ~Object() {
-      W->Indent--;
-      OS << "\n";
-      W->indent();
-      OS << "}";
-    }
-
-    void key(StringRef Key) {
-      Index++;
-      if (Index > 0)
-        OS << ",";
-      OS << "\n";
-      W->indent();
-      printJSONStringLiteral(Key, OS);
-      OS << " : ";
-    }
-
-  private:
-    JSONWriter *W;
-    raw_ostream &OS;
-    int Index = -1;
-  };
-
-  Object object() { return {this, OS}; }
-
-  // Helper RAII class to output JSON arrays.
-  class Array {
-  public:
-    Array(raw_ostream &OS) : OS(OS) { OS << "["; }
-    ~Array() { OS << "]"; }
-    void next() {
-      Index++;
-      if (Index > 0)
-        OS << ", ";
-    }
-
-  private:
-    raw_ostream &OS;
-    int Index = -1;
-  };
-
-  Array array() { return {OS}; }
-
-private:
-  void indent() { OS.indent(Indent * 2); }
-
-  static void printJSONStringLiteral(StringRef S, raw_ostream &OS) {
-    if (S.find('"') == std::string::npos) {
-      OS << "\"" << S << "\"";
-      return;
-    }
-    OS << "\"";
-    for (char Ch : S.bytes()) {
-      if (Ch == '"')
-        OS << "\\";
-      OS << Ch;
-    }
-    OS << "\"";
-  }
-
-  raw_ostream &OS;
-  int Indent = 0;
-};
-
 // Output symbolized information for coverage points in JSON.
 // Format:
 // {
@@ -375,10 +295,9 @@
 //       }
 //    }
 // }
-static void operator<<(JSONWriter &W,
+static void operator<<(json::OStream &W,
                        const std::vector<CoveragePoint> &Points) {
   // Group points by file.
-  auto ByFile(W.object());
   std::map<std::string, std::vector<const CoveragePoint *>> PointsByFile;
   for (const auto &Point : Points) {
     for (const DILineInfo &Loc : Point.Locs) {
@@ -388,10 +307,6 @@
 
   for (const auto &P : PointsByFile) {
     std::string FileName = P.first;
-    ByFile.key(FileName);
-
-    // Group points by function.
-    auto ByFn(W.object());
     std::map<std::string, std::vector<const CoveragePoint *>> PointsByFn;
     for (auto PointPtr : P.second) {
       for (const DILineInfo &Loc : PointPtr->Locs) {
@@ -399,54 +314,42 @@
       }
     }
 
-    for (const auto &P : PointsByFn) {
-      std::string FunctionName = P.first;
-      std::set<std::string> WrittenIds;
-
-      ByFn.key(FunctionName);
-
-      // Output <point_id> : "<line>:<col>".
-      auto ById(W.object());
-      for (const CoveragePoint *Point : P.second) {
-        for (const auto &Loc : Point->Locs) {
-          if (Loc.FileName != FileName || Loc.FunctionName != FunctionName)
-            continue;
-          if (WrittenIds.find(Point->Id) != WrittenIds.end())
-            continue;
-
-          WrittenIds.insert(Point->Id);
-          ById.key(Point->Id);
-          W << (utostr(Loc.Line) + ":" + utostr(Loc.Column));
-        }
+    W.attributeObject(P.first, [&] {
+      // Group points by function.
+      for (const auto &P : PointsByFn) {
+        std::string FunctionName = P.first;
+        std::set<std::string> WrittenIds;
+
+        W.attributeObject(FunctionName, [&] {
+          for (const CoveragePoint *Point : P.second) {
+            for (const auto &Loc : Point->Locs) {
+              if (Loc.FileName != FileName || Loc.FunctionName != FunctionName)
+                continue;
+              if (WrittenIds.find(Point->Id) != WrittenIds.end())
+                continue;
+
+              // Output <point_id> : "<line>:<col>".
+              WrittenIds.insert(Point->Id);
+              W.attribute(Point->Id,
+                          (utostr(Loc.Line) + ":" + utostr(Loc.Column)));
+            }
+          }
+        });
       }
-    }
+    });
   }
 }
 
-static void operator<<(JSONWriter &W, const SymbolizedCoverage &C) {
-  auto O(W.object());
-
-  {
-    O.key("covered-points");
-    auto PointsArray(W.array());
-
-    for (const std::string &P : C.CoveredIds) {
-      PointsArray.next();
-      W << P;
-    }
-  }
-
-  {
-    if (!C.BinaryHash.empty()) {
-      O.key("binary-hash");
-      W << C.BinaryHash;
-    }
-  }
-
-  {
-    O.key("point-symbol-info");
-    W << C.Points;
-  }
+static void operator<<(json::OStream &W, const SymbolizedCoverage &C) {
+  W.object([&] {
+    W.attributeArray("covered-points", [&] {
+      for (const std::string &P : C.CoveredIds) {
+        W.value(P);
+      }
+    });
+    W.attribute("binary-hash", C.BinaryHash);
+    W.attributeObject("point-symbol-info", [&] { W << C.Points; });
+  });
 }
 
 static std::string parseScalarString(yaml::Node *N) {
@@ -1275,7 +1178,7 @@
   }
   case MergeAction:
   case SymbolizeAction: { // merge & symbolize are synonims.
-    JSONWriter W(outs());
+    json::OStream W(outs(), 2);
     W << *Coverage;
     return 0;
   }