diff --git a/tools/clang/include/clang/Frontend/ASTUnit.h b/tools/clang/include/clang/Frontend/ASTUnit.h
index 04e6dce511..3eaf054139 100644
--- a/tools/clang/include/clang/Frontend/ASTUnit.h
+++ b/tools/clang/include/clang/Frontend/ASTUnit.h
@@ -184,6 +184,14 @@ private:
   /// some number of calls.
   unsigned PreambleRebuildCounter;
 
+  /// \brief Cache pairs "filename - source location"
+  ///
+  /// Cache contains only source locations from preamble so it is
+  /// guaranteed that they stay valid when the SourceManager is recreated.
+  /// This cache is used when loading preambule to increase performance
+  /// of that loading. It must be cleared when preamble is recreated.
+  llvm::StringMap<SourceLocation> PreambleSrcLocCache;
+
 public:
   class PreambleData {
     const FileEntry *File;
diff --git a/tools/clang/lib/Frontend/ASTUnit.cpp b/tools/clang/lib/Frontend/ASTUnit.cpp
index 76fd00a132..c1c2680dcd 100644
--- a/tools/clang/lib/Frontend/ASTUnit.cpp
+++ b/tools/clang/lib/Frontend/ASTUnit.cpp
@@ -1142,6 +1142,8 @@ bool ASTUnit::Parse(std::shared_ptr<PCHContainerOperations> PCHContainerOps,
   if (SavedMainFileBuffer)
     TranslateStoredDiagnostics(getFileManager(), getSourceManager(),
                                PreambleDiagnostics, StoredDiagnostics);
+  else
+    PreambleSrcLocCache.clear();
 
   if (!Act->Execute())
     goto error;
@@ -2544,8 +2546,16 @@ void ASTUnit::TranslateStoredDiagnostics(
     const FileEntry *FE = FileMgr.getFile(SD.Filename);
     if (!FE)
       continue;
-    FileID FID = SrcMgr.translateFile(FE);
-    SourceLocation FileLoc = SrcMgr.getLocForStartOfFile(FID);
+    SourceLocation FileLoc;
+    auto ItFileID = PreambleSrcLocCache.find(SD.Filename);
+    if (ItFileID == PreambleSrcLocCache.end()) {
+      FileID FID = SrcMgr.translateFile(FE);
+      FileLoc = SrcMgr.getLocForStartOfFile(FID);
+      PreambleSrcLocCache[SD.Filename] = FileLoc;
+    } else {
+      FileLoc = ItFileID->getValue();
+    }
+
     if (FileLoc.isInvalid())
       continue;
     SourceLocation L = FileLoc.getLocWithOffset(SD.LocOffset);