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
@@ -104,10 +104,10 @@
 /// current Format uses MD5 to represent the string.
 static inline StringRef getRepInFormat(StringRef Name, bool UseMD5,
                                        std::string &GUIDBuf) {
-  if (Name.empty())
+  if (Name.empty() || !UseMD5)
     return Name;
   GUIDBuf = std::to_string(Function::getGUID(Name));
-  return UseMD5 ? StringRef(GUIDBuf) : Name;
+  return GUIDBuf;
 }
 
 static inline uint64_t SPVersion() { return 103; }
diff --git a/llvm/include/llvm/ProfileData/SampleProfReader.h b/llvm/include/llvm/ProfileData/SampleProfReader.h
--- a/llvm/include/llvm/ProfileData/SampleProfReader.h
+++ b/llvm/include/llvm/ProfileData/SampleProfReader.h
@@ -407,7 +407,15 @@
     std::string FGUID;
     StringRef CanonName = FunctionSamples::getCanonicalFnName(F);
     CanonName = getRepInFormat(CanonName, useMD5(), FGUID);
-    return &Profiles[CanonName];
+    auto It = Profiles.find(CanonName);
+    if (It == Profiles.end()) {
+      if (!FGUID.empty()) {
+        assert(useMD5());
+        CanonName = *MD5NameBuffer.insert(FGUID).first;
+      }
+      return &Profiles[CanonName];
+    }
+    return &It->second;
   }
 
   /// Return the samples collected for function \p F.
@@ -503,6 +511,10 @@
   /// Memory buffer holding the profile file.
   std::unique_ptr<MemoryBuffer> Buffer;
 
+  /// Extra name buffer holding names created on demand.
+  /// This should only be needed for md5 profiles.
+  std::set<std::string> MD5NameBuffer;
+
   /// Profile summary information.
   std::unique_ptr<ProfileSummary> Summary;