--- a/tools/dsymutil/NonRelocatableStringpool.h	Sun Dec 23 19:23:36 2018 +0900
+++ b/tools/dsymutil/NonRelocatableStringpool.h	Wed Aug 14 19:46:37 2019 +0900
@@ -1,21 +1,22 @@
 //===- NonRelocatableStringpool.h - A simple stringpool  --------*- C++ -*-===//
 //
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_TOOLS_DSYMUTIL_NONRELOCATABLESTRINGPOOL_H
 #define LLVM_TOOLS_DSYMUTIL_NONRELOCATABLESTRINGPOOL_H
 
+#include "SymbolMap.h"
+
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/CodeGen/DwarfStringPoolEntry.h"
 #include "llvm/Support/Allocator.h"
 #include <cstdint>
-#include <utility>
+#include <vector>
 
 namespace llvm {
 namespace dsymutil {
@@ -23,8 +24,8 @@
 /// A string table that doesn't need relocations.
 ///
 /// We are doing a final link, no need for a string table that has relocation
-/// entries for every reference to it. This class provides this ablitity by
-/// just associating offsets with strings.
+/// entries for every reference to it. This class provides this ability by just
+/// associating offsets with strings.
 class NonRelocatableStringpool {
 public:
   /// Entries are stored into the StringMap and simply linked together through
@@ -32,35 +33,56 @@
   /// order.
   using MapTy = StringMap<DwarfStringPoolEntry, BumpPtrAllocator>;
 
-  NonRelocatableStringpool() {
-    // Legacy dsymutil puts an empty string at the start of the line
-    // table.
+  NonRelocatableStringpool(
+      SymbolMapTranslator Translator = SymbolMapTranslator())
+      : Translator(Translator) {
+    // Legacy dsymutil puts an empty string at the start of the line table.
     EmptyString = getEntry("");
   }
 
   DwarfStringPoolEntryRef getEntry(StringRef S);
 
   /// Get the offset of string \p S in the string table. This can insert a new
-  /// element or return the offset of a pre-exisitng one.
-  uint32_t getStringOffset(StringRef S);
+  /// element or return the offset of a pre-existing one.
+  uint32_t getStringOffset(StringRef S) { return getEntry(S).getOffset(); }
 
   /// Get permanent storage for \p S (but do not necessarily emit \p S in the
-  /// output section).
+  /// output section). A latter call to getStringOffset() with the same string
+  /// will chain it though.
+  ///
   /// \returns The StringRef that points to permanent storage to use
   /// in place of \p S.
   StringRef internString(StringRef S);
 
   uint64_t getSize() { return CurrentEndOffset; }
 
-  std::vector<DwarfStringPoolEntryRef> getEntries() const;
+  /// Return the list of strings to be emitted. This does not contain the
+  /// strings which were added via internString only.
+  std::vector<DwarfStringPoolEntryRef> getEntriesForEmission() const;
 
 private:
   MapTy Strings;
   uint32_t CurrentEndOffset = 0;
   unsigned NumEntries = 0;
   DwarfStringPoolEntryRef EmptyString;
+  SymbolMapTranslator Translator;
 };
 
+/// Helper for making strong types.
+template <typename T, typename S> class StrongType : public T {
+public:
+  template <typename... Args>
+  explicit StrongType(Args... A) : T(std::forward<Args>(A)...) {}
+};
+
+/// It's very easy to introduce bugs by passing the wrong string pool in the
+/// dwarf linker. By using strong types the interface enforces that the right
+/// kind of pool is used.
+struct UniqueTag {};
+struct OffsetsTag {};
+using UniquingStringPool = StrongType<NonRelocatableStringpool, UniqueTag>;
+using OffsetsStringPool = StrongType<NonRelocatableStringpool, OffsetsTag>;
+
 } // end namespace dsymutil
 } // end namespace llvm