diff --git a/llvm/lib/ProfileData/SampleProfWriter.cpp b/llvm/lib/ProfileData/SampleProfWriter.cpp
--- a/llvm/lib/ProfileData/SampleProfWriter.cpp
+++ b/llvm/lib/ProfileData/SampleProfWriter.cpp
@@ -361,7 +361,7 @@
 std::error_code SampleProfileWriterText::writeSample(const FunctionSamples &S) {
   auto &OS = *OutputStream;
   if (FunctionSamples::ProfileIsCS)
-    OS << "[" << S.getNameWithContext() << "]:" << S.getTotalSamples();
+    OS << S.getNameWithContext(true) << ":" << S.getTotalSamples();
   else
     OS << S.getName() << ":" << S.getTotalSamples();
   if (Indent == 0)
diff --git a/llvm/test/tools/llvm-profgen/cs-extbinary.test b/llvm/test/tools/llvm-profgen/cs-extbinary.test
new file mode 100644
--- /dev/null
+++ b/llvm/test/tools/llvm-profgen/cs-extbinary.test
@@ -0,0 +1,14 @@
+; test for dwarf-based cs profile
+; RUN: llvm-profgen --format=extbinary --perfscript=%S/Inputs/recursion-compression-noprobe.perfscript --binary=%S/Inputs/recursion-compression-noprobe.perfbin --output=%t1 --csprof-cold-thres=0
+; RUN: llvm-profdata merge --sample --text --output=%t2 %t1
+; RUN: FileCheck %S/recursion-compression-noprobe.test --input-file %t2
+; RUN: llvm-profdata merge --sample --extbinary --output=%t3 %t2 && llvm-profdata merge --sample --text --output=%t4 %t3
+; RUN: diff -b %t2 %t4
+
+
+; test for probe-based cs profile
+; RUN: llvm-profgen --format=extbinary --perfscript=%S/Inputs/recursion-compression-pseudoprobe.perfscript --binary=%S/Inputs/recursion-compression-pseudoprobe.perfbin --output=%t5 --csprof-cold-thres=0
+; RUN: llvm-profdata merge --sample --text --output=%t6 %t5
+; RUN: FileCheck %S/recursion-compression-pseudoprobe.test --input-file %t6
+; RUN: llvm-profdata merge --sample --extbinary --output=%t7 %t6 && llvm-profdata merge --sample --text --output=%t8 %t7
+; RUN: diff -b %t6 %t8
diff --git a/llvm/test/tools/llvm-profgen/inline-cs-noprobe.test b/llvm/test/tools/llvm-profgen/inline-cs-noprobe.test
--- a/llvm/test/tools/llvm-profgen/inline-cs-noprobe.test
+++ b/llvm/test/tools/llvm-profgen/inline-cs-noprobe.test
@@ -10,17 +10,16 @@
 ; CHECK: 1: 14
 
 ; CHECK-UNWINDER: Binary(inline-cs-noprobe.perfbin)'s Range Counter:
-; CHECK-UNWINDER: main:1 @ foo
+; CHECK-UNWINDER: [main:1 @ foo:3.2 @ bar]
+; CHECK-UNWINDER:   (6af, 6bb): 14
+; CHECK-UNWINDER: [main:1 @ foo]
 ; CHECK-UNWINDER:   (670, 6ad): 1
 ; CHECK-UNWINDER:   (67e, 69b): 1
 ; CHECK-UNWINDER:   (67e, 6ad): 13
 ; CHECK-UNWINDER:   (6bd, 6c8): 14
-; CHECK-UNWINDER: main:1 @ foo:3.2 @ bar
-; CHECK-UNWINDER:   (6af, 6bb): 14
-
 
 ; CHECK-UNWINDER: Binary(inline-cs-noprobe.perfbin)'s Branch Counter:
-; CHECK-UNWINDER: main:1 @ foo
+; CHECK-UNWINDER: [main:1 @ foo]
 ; CHECK-UNWINDER:   (69b, 670): 1
 ; CHECK-UNWINDER:   (6c8, 67e): 15
 
diff --git a/llvm/test/tools/llvm-profgen/noinline-cs-noprobe.test b/llvm/test/tools/llvm-profgen/noinline-cs-noprobe.test
--- a/llvm/test/tools/llvm-profgen/noinline-cs-noprobe.test
+++ b/llvm/test/tools/llvm-profgen/noinline-cs-noprobe.test
@@ -12,25 +12,27 @@
 ; CHECK: 3: 3 bar:3
 
 ; CHECK-UNWINDER: Binary(noinline-cs-noprobe.perfbin)'s Range Counter:
-; CHECK-UNWINDER: main:1 @ foo
-; CHECK-UNWINDER:   (5ff, 62f): 3
-; CHECK-UNWINDER:   (634, 637): 3
-; CHECK-UNWINDER:   (645, 645): 3
-; CHECK-UNWINDER: main:1 @ foo:3 @ bar
+; CHECK-UNWINDER: [main:1 @ foo:3 @ bar]
 ; CHECK-UNWINDER:   (5b0, 5c8): 1
 ; CHECK-UNWINDER:   (5b0, 5d7): 2
 ; CHECK-UNWINDER:   (5dc, 5e9): 1
 ; CHECK-UNWINDER:   (5e5, 5e9): 2
+; CHECK-UNWINDER: [main:1 @ foo]
+; CHECK-UNWINDER:   (5ff, 62f): 3
+; CHECK-UNWINDER:   (634, 637): 3
+; CHECK-UNWINDER:   (645, 645): 3
+
 
 ; CHECK-UNWINDER: Binary(noinline-cs-noprobe.perfbin)'s Branch Counter:
-; CHECK-UNWINDER: main:1 @ foo
-; CHECK-UNWINDER:   (62f, 5b0): 3
-; CHECK-UNWINDER:   (637, 645): 3
-; CHECK-UNWINDER:   (645, 5ff): 3
-; CHECK-UNWINDER: main:1 @ foo:3 @ bar
+; CHECK-UNWINDER: [main:1 @ foo:3 @ bar]
 ; CHECK-UNWINDER:   (5c8, 5dc): 2
 ; CHECK-UNWINDER:   (5d7, 5e5): 2
 ; CHECK-UNWINDER:   (5e9, 634): 3
+; CHECK-UNWINDER: [main:1 @ foo]
+; CHECK-UNWINDER:   (62f, 5b0): 3
+; CHECK-UNWINDER:   (637, 645): 3
+; CHECK-UNWINDER:   (645, 5ff): 3
+
 
 
 
diff --git a/llvm/test/tools/llvm-profgen/recursion-compression-noprobe.test b/llvm/test/tools/llvm-profgen/recursion-compression-noprobe.test
--- a/llvm/test/tools/llvm-profgen/recursion-compression-noprobe.test
+++ b/llvm/test/tools/llvm-profgen/recursion-compression-noprobe.test
@@ -10,16 +10,17 @@
 ; CHECK-UNCOMPRESS:[main:1 @ foo:3 @ fa:2 @ fb]:12:0
 ; CHECK-UNCOMPRESS: 1: 11
 ; CHECK-UNCOMPRESS: 2: 1 fa:1
-; CHECK-UNCOMPRESS:[main:1 @ foo:3 @ fa:2 @ fb:2 @ fa]:3:0
-; CHECK-UNCOMPRESS: 1: 1
-; CHECK-UNCOMPRESS: 2: 2 fb:1
 ; CHECK-UNCOMPRESS:[main:1 @ foo]:3:0
 ; CHECK-UNCOMPRESS: 2: 1
 ; CHECK-UNCOMPRESS: 3: 2 fa:1
-; CHECK-UNCOMPRESS:[main:1 @ foo:3 @ fa:2 @ fb:2 @ fa:2 @ fb:2 @ fa]:1:0
-; CHECK-UNCOMPRESS: 4: 1
+; CHECK-UNCOMPRESS:[main:1 @ foo:3 @ fa:2 @ fb:2 @ fa]:3:0
+; CHECK-UNCOMPRESS: 1: 1
+; CHECK-UNCOMPRESS: 2: 2 fb:1
 ; CHECK-UNCOMPRESS:[main:1 @ foo:3 @ fa:2 @ fb:2 @ fa:2 @ fb]:1:0
 ; CHECK-UNCOMPRESS: 2: 1 fa:1
+; CHECK-UNCOMPRESS:[main:1 @ foo:3 @ fa:2 @ fb:2 @ fa:2 @ fb:2 @ fa]:1:0
+; CHECK-UNCOMPRESS: 4: 1
+
 
 ; CHECK: [main:1 @ foo:3 @ fa]:14:0
 ; CHECK:  1: 1
diff --git a/llvm/test/tools/llvm-profgen/recursion-compression-pseudoprobe.test b/llvm/test/tools/llvm-profgen/recursion-compression-pseudoprobe.test
--- a/llvm/test/tools/llvm-profgen/recursion-compression-pseudoprobe.test
+++ b/llvm/test/tools/llvm-profgen/recursion-compression-pseudoprobe.test
@@ -4,11 +4,11 @@
 ; RUN: llvm-profgen --perfscript=%S/Inputs/recursion-compression-pseudoprobe.perfscript --binary=%S/Inputs/recursion-compression-pseudoprobe.perfbin --output=%t --show-unwinder-output --csprof-cold-thres=0 | FileCheck %s --check-prefix=CHECK-UNWINDER
 ; RUN: FileCheck %s --input-file %t
 
-; CHECK-UNCOMPRESS: [main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:6 @ fa:8 @ fa:7 @ fb:6 @ fa]:4:1
+; CHECK-UNCOMPRESS: [main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:6 @ fa]:4:1
 ; CHECK-UNCOMPRESS:  1: 1
 ; CHECK-UNCOMPRESS:  3: 1
-; CHECK-UNCOMPRESS:  4: 1
-; CHECK-UNCOMPRESS:  7: 1 fb:1
+; CHECK-UNCOMPRESS:  5: 1
+; CHECK-UNCOMPRESS:  8: 1 fa:1
 ; CHECK-UNCOMPRESS:  !CFGChecksum: 120515930909
 ; CHECK-UNCOMPRESS: [main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:6 @ fa:8 @ fa]:4:1
 ; CHECK-UNCOMPRESS:  1: 1
@@ -16,28 +16,13 @@
 ; CHECK-UNCOMPRESS:  4: 1
 ; CHECK-UNCOMPRESS:  7: 1 fb:1
 ; CHECK-UNCOMPRESS:  !CFGChecksum: 120515930909
-; CHECK-UNCOMPRESS: [main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:6 @ fa]:4:1
+; CHECK-UNCOMPRESS: [main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:6 @ fa:8 @ fa:7 @ fb:6 @ fa]:4:1
 ; CHECK-UNCOMPRESS:  1: 1
 ; CHECK-UNCOMPRESS:  3: 1
-; CHECK-UNCOMPRESS:  5: 1
-; CHECK-UNCOMPRESS:  8: 1 fa:1
+; CHECK-UNCOMPRESS:  4: 1
+; CHECK-UNCOMPRESS:  7: 1 fb:1
 ; CHECK-UNCOMPRESS:  !CFGChecksum: 120515930909
-; CHECK-UNCOMPRESS: [main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:6 @ fa:8 @ fa:7 @ fb:6 @ fa:7 @ fb]:3:1
-; CHECK-UNCOMPRESS:  1: 1
-; CHECK-UNCOMPRESS:  3: 1
-; CHECK-UNCOMPRESS:  6: 1 fa:1
-; CHECK-UNCOMPRESS:  !CFGChecksum: 72617220756
-; CHECK-UNCOMPRESS: [main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:6 @ fa:8 @ fa:7 @ fb]:3:1
-; CHECK-UNCOMPRESS:  1: 1
-; CHECK-UNCOMPRESS:  3: 1
-; CHECK-UNCOMPRESS:  6: 1 fa:1
-; CHECK-UNCOMPRESS:  !CFGChecksum: 72617220756
-; CHECK-UNCOMPRESS: [main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb]:3:1
-; CHECK-UNCOMPRESS:  1: 1
-; CHECK-UNCOMPRESS:  3: 1
-; CHECK-UNCOMPRESS:  6: 1 fa:1
-; CHECK-UNCOMPRESS:  !CFGChecksum: 72617220756
-; CHECK-UNCOMPRESS: [main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb]:3:1
+; CHECK-UNCOMPRESS: [main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb]:3:1
 ; CHECK-UNCOMPRESS:  1: 1
 ; CHECK-UNCOMPRESS:  2: 1
 ; CHECK-UNCOMPRESS:  5: 1 fb:1
@@ -47,11 +32,26 @@
 ; CHECK-UNCOMPRESS:  2: 1
 ; CHECK-UNCOMPRESS:  5: 1 fb:1
 ; CHECK-UNCOMPRESS:  !CFGChecksum: 72617220756
-; CHECK-UNCOMPRESS: [main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb]:3:1
+; CHECK-UNCOMPRESS: [main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb]:3:1
 ; CHECK-UNCOMPRESS:  1: 1
 ; CHECK-UNCOMPRESS:  2: 1
 ; CHECK-UNCOMPRESS:  5: 1 fb:1
 ; CHECK-UNCOMPRESS:  !CFGChecksum: 72617220756
+; CHECK-UNCOMPRESS: [main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb]:3:1
+; CHECK-UNCOMPRESS:  1: 1
+; CHECK-UNCOMPRESS:  3: 1
+; CHECK-UNCOMPRESS:  6: 1 fa:1
+; CHECK-UNCOMPRESS:  !CFGChecksum: 72617220756
+; CHECK-UNCOMPRESS: [main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:6 @ fa:8 @ fa:7 @ fb]:3:1
+; CHECK-UNCOMPRESS:  1: 1
+; CHECK-UNCOMPRESS:  3: 1
+; CHECK-UNCOMPRESS:  6: 1 fa:1
+; CHECK-UNCOMPRESS:  !CFGChecksum: 72617220756
+; CHECK-UNCOMPRESS: [main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:6 @ fa:8 @ fa:7 @ fb:6 @ fa:7 @ fb]:3:1
+; CHECK-UNCOMPRESS:  1: 1
+; CHECK-UNCOMPRESS:  3: 1
+; CHECK-UNCOMPRESS:  6: 1 fa:1
+; CHECK-UNCOMPRESS:  !CFGChecksum: 72617220756
 ; CHECK-UNCOMPRESS: [main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:5 @ fb:6 @ fa:8 @ fa:7 @ fb:6 @ fa:7 @ fb:6 @ fa]:2:1
 ; CHECK-UNCOMPRESS:  1: 1
 ; CHECK-UNCOMPRESS:  3: 1
@@ -74,30 +74,31 @@
 ; CHECK:  4: 1
 ; CHECK:  7: 1 fb:1
 ; CHECK:  !CFGChecksum: 120515930909
-; CHECK: [main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5 @ fb:6 @ fa:8 @ fa]:4:1
-; CHECK:  1: 1
-; CHECK:  3: 1
-; CHECK:  4: 1
-; CHECK:  7: 1 fb:1
-; CHECK:  !CFGChecksum: 120515930909
 ; CHECK: [main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5 @ fb:6 @ fa]:4:1
 ; CHECK:  1: 1
 ; CHECK:  3: 1
 ; CHECK:  5: 1
 ; CHECK:  8: 1 fa:1
 ; CHECK:  !CFGChecksum: 120515930909
-; CHECK: [main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5 @ fb:6 @ fa:8 @ fa:7 @ fb:6 @ fa:7 @ fb]:3:1
+; CHECK: [main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5 @ fb:6 @ fa:8 @ fa]:4:1
+; CHECK:  1: 1
+; CHECK:  3: 1
+; CHECK:  4: 1
+; CHECK:  7: 1 fb:1
+; CHECK:  !CFGChecksum: 120515930909
+; CHECK: [main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5 @ fb:6 @ fa:8 @ fa:7 @ fb]:3:1
 ; CHECK:  1: 1
 ; CHECK:  3: 1
 ; CHECK:  6: 1 fa:1
 ; CHECK:  !CFGChecksum: 72617220756
-; CHECK: [main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5 @ fb:6 @ fa:8 @ fa:7 @ fb]:3:1
+; CHECK: [main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5 @ fb:6 @ fa:8 @ fa:7 @ fb:6 @ fa:7 @ fb]:3:1
 ; CHECK:  1: 1
 ; CHECK:  3: 1
 ; CHECK:  6: 1 fa:1
 ; CHECK:  !CFGChecksum: 72617220756
 
 
+
 ; CHECK-UNWINDER: Binary(recursion-compression-pseudoprobe.perfbin)'s Range Counter:
 ; CHECK-UNWINDER: main:2 @ foo:5 @ fa:8 @ fa:7 @ fb:5
 ; CHECK-UNWINDER:   (7a0, 7a7): 1
diff --git a/llvm/tools/llvm-profgen/ProfileGenerator.cpp b/llvm/tools/llvm-profgen/ProfileGenerator.cpp
--- a/llvm/tools/llvm-profgen/ProfileGenerator.cpp
+++ b/llvm/tools/llvm-profgen/ProfileGenerator.cpp
@@ -268,16 +268,18 @@
                                            CalleeName, Count);
 
     // Record head sample for called target(callee)
-    // TODO: Cleanup ' @ '
-    std::string CalleeContextId =
-        getCallSite(LeafLoc) + " @ " + CalleeName.str();
+    std::ostringstream OCalleeCtxStr;
     if (ContextId.find(" @ ") != StringRef::npos) {
-      CalleeContextId =
-          ContextId.rsplit(" @ ").first.str() + " @ " + CalleeContextId;
+      OCalleeCtxStr << ContextId.rsplit(" @ ").first.str();
+      OCalleeCtxStr << " @ ";
+    } else {
+      OCalleeCtxStr << "[";
     }
+    OCalleeCtxStr << getCallSite(LeafLoc) << " @ " << CalleeName.str();
+    OCalleeCtxStr << "]";
 
     FunctionSamples &CalleeProfile =
-        getFunctionProfileForContext(CalleeContextId);
+        getFunctionProfileForContext(OCalleeCtxStr.str());
     assert(Count != 0 && "Unexpected zero weight branch");
     CalleeProfile.addHeadSamples(Count);
   }
@@ -285,6 +287,7 @@
 
 static FrameLocation getCallerContext(StringRef CalleeContext,
                                       StringRef &CallerNameWithContext) {
+  CalleeContext = CalleeContext.substr(1, CalleeContext.size() - 2);
   StringRef CallerContext = CalleeContext.rsplit(" @ ").first;
   CallerNameWithContext = CallerContext.rsplit(':').first;
   auto ContextSplit = CallerContext.rsplit(" @ ");
@@ -314,9 +317,10 @@
       continue;
 
     // Infer Caller's frame loc and context ID through string splitting
-    StringRef CallerContextId;
+    StringRef CxtWithoutBracket;
     FrameLocation &&CallerLeafFrameLoc =
-        getCallerContext(CalleeContext, CallerContextId);
+        getCallerContext(CalleeContext, CxtWithoutBracket);
+    std::string CallerContextId = "[" + CxtWithoutBracket.str() + "]";
 
     // It's possible that we haven't seen any sample directly in the caller,
     // in which case CallerProfile will not exist. But we can't modify
@@ -362,8 +366,8 @@
   // Remove the code profile from ProfileMap and merge them into BaseProileMap
   StringMap<FunctionSamples> BaseProfileMap;
   for (const auto &I : ToRemoveVec) {
-    auto Ret =
-        BaseProfileMap.try_emplace(I.second->getName(), FunctionSamples());
+    auto Ret = BaseProfileMap.try_emplace("[" + I.second->getName().str() + "]",
+                                          FunctionSamples());
     FunctionSamples &BaseProfile = Ret.first->second;
     BaseProfile.merge(*I.second);
     ProfileMap.erase(I.first);
@@ -483,10 +487,11 @@
         // context id to infer caller's context id to ensure they share the
         // same context prefix.
         StringRef CalleeContextId =
-            FunctionProfile.getContext().getNameWithContext();
-        StringRef CallerContextId;
+            FunctionProfile.getContext().getNameWithContext(true);
+        StringRef CxtWithoutBracket;
         FrameLocation &&CallerLeafFrameLoc =
-            getCallerContext(CalleeContextId, CallerContextId);
+            getCallerContext(CalleeContextId, CxtWithoutBracket);
+        std::string CallerContextId = "[" + CxtWithoutBracket.str() + "]";
         uint64_t CallerIndex = CallerLeafFrameLoc.second.LineOffset;
         FunctionSamples &CallerProfile =
             getFunctionProfileForContext(CallerContextId);
@@ -534,18 +539,19 @@
   CSProfileGenerator::compressRecursionContext(ContextStrStack);
 
   std::ostringstream OContextStr;
+  OContextStr << "[";
   for (uint32_t I = 0; I < ContextStrStack.size(); I++) {
-    if (OContextStr.str().size())
+    if (OContextStr.str().size() > 1)
       OContextStr << " @ ";
     OContextStr << ContextStrStack[I];
   }
   // For leaf inlined context with the top frame, we should strip off the top
   // frame's probe id, like:
   // Inlined stack: [foo:1, bar:2], the ContextId will be "foo:1 @ bar"
-  if (OContextStr.str().size())
+  if (OContextStr.str().size() > 1)
     OContextStr << " @ ";
   OContextStr << StringRef(LeafFrame).split(":").first.str();
-
+  OContextStr << "]";
   FunctionSamples &FunctionProile =
       getFunctionProfileForContext(OContextStr.str());
   FunctionProile.setFunctionHash(LeafFuncDesc->FuncHash);
diff --git a/llvm/tools/llvm-profgen/ProfiledBinary.cpp b/llvm/tools/llvm-profgen/ProfiledBinary.cpp
--- a/llvm/tools/llvm-profgen/ProfiledBinary.cpp
+++ b/llvm/tools/llvm-profgen/ProfiledBinary.cpp
@@ -146,16 +146,18 @@
   CSProfileGenerator::compressRecursionContext<std::string>(ContextVec);
 
   std::ostringstream OContextStr;
+  OContextStr << "[";
   for (uint32_t I = 0; I < (uint32_t)ContextVec.size(); I++) {
-    if (OContextStr.str().size()) {
+    if (OContextStr.str().size() > 1) {
       OContextStr << " @ ";
     }
     OContextStr << ContextVec[I];
   }
   // Only keep the function name for the leaf frame
-  if (OContextStr.str().size())
+  if (OContextStr.str().size() > 1)
     OContextStr << " @ ";
   OContextStr << StringRef(LeafFrame).split(":").first.str();
+  OContextStr << "]";
   return OContextStr.str();
 }