diff --git a/llvm/include/llvm/ProfileData/SampleProf.h b/llvm/include/llvm/ProfileData/SampleProf.h
--- a/llvm/include/llvm/ProfileData/SampleProf.h
+++ b/llvm/include/llvm/ProfileData/SampleProf.h
@@ -473,9 +473,10 @@
 
   static SampleProfileFormat Format;
   /// GUIDToFuncNameMap saves the mapping from GUID to the symbol name, for
-  /// all the function symbols defined or declared in CurrentModule.
-  static DenseMap<uint64_t, StringRef> GUIDToFuncNameMap;
-  static Module *CurrentModule;
+  /// all the function symbols defined or declared in CurrentModule. These
+  /// need to be thread_local because we can have parallel ThinLTO backends.
+  thread_local static DenseMap<uint64_t, StringRef> GUIDToFuncNameMap;
+  thread_local static Module *CurrentModule;
 
   class GUIDToFuncNameMapper {
   public:
diff --git a/llvm/lib/ProfileData/SampleProf.cpp b/llvm/lib/ProfileData/SampleProf.cpp
--- a/llvm/lib/ProfileData/SampleProf.cpp
+++ b/llvm/lib/ProfileData/SampleProf.cpp
@@ -28,8 +28,8 @@
 namespace llvm {
 namespace sampleprof {
 SampleProfileFormat FunctionSamples::Format;
-DenseMap<uint64_t, StringRef> FunctionSamples::GUIDToFuncNameMap;
-Module *FunctionSamples::CurrentModule;
+thread_local DenseMap<uint64_t, StringRef> FunctionSamples::GUIDToFuncNameMap;
+thread_local Module *FunctionSamples::CurrentModule;
 } // namespace sampleprof
 } // namespace llvm