Index: include/clang/Basic/SourceManager.h
===================================================================
--- include/clang/Basic/SourceManager.h
+++ include/clang/Basic/SourceManager.h
@@ -1525,6 +1525,24 @@
   /// first inclusion.
   FileID translateFile(const FileEntry *SourceFile) const;
 
+  /// Looks through all the local and imported source locations to find the set
+  /// of FileIDs that correspond to the given entry.
+  ///
+  /// \returns the set of FileIDs for the given file, in the order of inclusion.
+  llvm::SmallVector<FileID, 2>
+  findFileIDsForFile(const FileEntry *SourceFile) const;
+
+private:
+  /// Looks through all the local and imported source locations to find the set
+  /// of FileIDs that correspond to the given entry.
+  ///
+  /// \param Callback should return true to exit the search.
+  ///
+  /// \returns true if the callback returned true, false otherwise.
+  bool findFileIDsForFile(const FileEntry *SourceFile,
+                          llvm::function_ref<bool(FileID)> Callback) const;
+
+public:
   /// Get the source location in \p FID for the given line:col.
   /// Returns null location if \p FID is not a file SLocEntry.
   SourceLocation translateLineCol(FileID FID,
Index: lib/Basic/SourceManager.cpp
===================================================================
--- lib/Basic/SourceManager.cpp
+++ lib/Basic/SourceManager.cpp
@@ -1602,6 +1602,47 @@
   return translateLineCol(FirstFID, Line, Col);
 }
 
+bool SourceManager::findFileIDsForFile(
+    const FileEntry *SourceFile,
+    llvm::function_ref<bool(FileID)> Callback) const {
+  assert(SourceFile && "Null source file!");
+
+  // Look through all of the local source locations.
+  for (unsigned I = 0, N = local_sloc_entry_size(); I != N; ++I) {
+    bool Invalid = false;
+    const SLocEntry &SLoc = getLocalSLocEntry(I, &Invalid);
+    if (Invalid)
+      return false;
+
+    if (SLoc.isFile() && SLoc.getFile().getContentCache() &&
+        SLoc.getFile().getContentCache()->OrigEntry == SourceFile) {
+      if (Callback(FileID::get(I)))
+        return true;
+    }
+  }
+
+  // If that still didn't help, try the modules.
+  for (unsigned I = 0, N = loaded_sloc_entry_size(); I != N; ++I) {
+    const SLocEntry &SLoc = getLoadedSLocEntry(I);
+    if (SLoc.isFile() && SLoc.getFile().getContentCache() &&
+        SLoc.getFile().getContentCache()->OrigEntry == SourceFile) {
+      if (Callback(FileID::get(-int(I) - 2)))
+        return true;
+    }
+  }
+  return false;
+}
+
+llvm::SmallVector<FileID, 2>
+SourceManager::findFileIDsForFile(const FileEntry *SourceFile) const {
+  llvm::SmallVector<FileID, 2> Result;
+  findFileIDsForFile(SourceFile, [&](FileID F) {
+    Result.push_back(F);
+    return false;
+  });
+  return Result;
+}
+
 /// Get the FileID for the given file.
 ///
 /// If the source file is included multiple times, the FileID will be the
@@ -1650,35 +1691,16 @@
     }
   }
 
-  if (FirstFID.isInvalid()) {
-    // The location we're looking for isn't in the main file; look
-    // through all of the local source locations.
-    for (unsigned I = 0, N = local_sloc_entry_size(); I != N; ++I) {
-      bool Invalid = false;
-      const SLocEntry &SLoc = getLocalSLocEntry(I, &Invalid);
-      if (Invalid)
-        return FileID();
+  if (FirstFID.isValid())
+    return FirstFID;
 
-      if (SLoc.isFile() &&
-          SLoc.getFile().getContentCache() &&
-          SLoc.getFile().getContentCache()->OrigEntry == SourceFile) {
-        FirstFID = FileID::get(I);
-        break;
-      }
-    }
-    // If that still didn't help, try the modules.
-    if (FirstFID.isInvalid()) {
-      for (unsigned I = 0, N = loaded_sloc_entry_size(); I != N; ++I) {
-        const SLocEntry &SLoc = getLoadedSLocEntry(I);
-        if (SLoc.isFile() &&
-            SLoc.getFile().getContentCache() &&
-            SLoc.getFile().getContentCache()->OrigEntry == SourceFile) {
-          FirstFID = FileID::get(-int(I) - 2);
-          break;
-        }
-      }
-    }
-  }
+  // The location we're looking for isn't in the main file; look
+  // through all of the local and the imported source locations.
+  if (findFileIDsForFile(SourceFile, [&](FileID F) {
+        FirstFID = F;
+        return true;
+      }))
+    return FirstFID;
 
   // If we haven't found what we want yet, try again, but this time stat()
   // each of the files in case the files have changed since we originally
Index: unittests/Basic/SourceManagerTest.cpp
===================================================================
--- unittests/Basic/SourceManagerTest.cpp
+++ unittests/Basic/SourceManagerTest.cpp
@@ -377,6 +377,60 @@
   EXPECT_TRUE(SourceMgr.isBeforeInTranslationUnit(Macros[10].Loc, Macros[11].Loc));
 }
 
+TEST_F(SourceManagerTest, findFileIDsForFile) {
+  const char *header = "int x;";
+
+  const char *main = "#include </test-header.h>\n"
+                     "#include </test-header.h>\n";
+
+  std::unique_ptr<llvm::MemoryBuffer> HeaderBuf =
+      llvm::MemoryBuffer::getMemBuffer(header);
+  std::unique_ptr<llvm::MemoryBuffer> MainBuf =
+      llvm::MemoryBuffer::getMemBuffer(main);
+
+  const FileEntry *HeaderFile =
+      FileMgr.getVirtualFile("/test-header.h", HeaderBuf->getBufferSize(), 0);
+  SourceMgr.overrideFileContents(HeaderFile, std::move(HeaderBuf));
+  const FileEntry *MainFile =
+      FileMgr.getVirtualFile("main.cpp", MainBuf->getBufferSize(), 0);
+  SourceMgr.overrideFileContents(MainFile, std::move(MainBuf));
+  SourceMgr.setMainFileID(
+      SourceMgr.createFileID(MainFile, SourceLocation(), SrcMgr::C_User));
+
+  TrivialModuleLoader ModLoader;
+  MemoryBufferCache PCMCache;
+  HeaderSearch HeaderInfo(std::make_shared<HeaderSearchOptions>(), SourceMgr,
+                          Diags, LangOpts, &*Target);
+  Preprocessor PP(std::make_shared<PreprocessorOptions>(), Diags, LangOpts,
+                  SourceMgr, PCMCache, HeaderInfo, ModLoader,
+                  /*IILookup =*/nullptr,
+                  /*OwnsHeaderSearch =*/false);
+  PP.Initialize(*Target);
+
+  PP.EnterMainSourceFile();
+
+  while (1) {
+    Token tok;
+    PP.Lex(tok);
+    if (tok.is(tok::eof))
+      break;
+  }
+
+  llvm::SmallVector<FileID, 2> MainFileID =
+      SourceMgr.findFileIDsForFile(MainFile);
+  ASSERT_EQ(1U, MainFileID.size());
+  ASSERT_EQ(MainFileID[0], SourceMgr.getMainFileID());
+
+  llvm::SmallVector<FileID, 2> Files = SourceMgr.findFileIDsForFile(HeaderFile);
+
+  ASSERT_EQ(2U, Files.size());
+  ASSERT_NE(Files[0], Files[1]);
+  SourceLocation Loc1 = SourceMgr.translateLineCol(Files[0], 1, 1);
+  SourceLocation Loc2 = SourceMgr.translateLineCol(Files[1], 1, 1);
+  ASSERT_NE(Loc1, Loc2);
+  ASSERT_TRUE(SourceMgr.isBeforeInTranslationUnit(Loc1, Loc2));
+}
+
 #endif
 
 } // anonymous namespace