Index: llvm/include/llvm/Object/IRSymtab.h
===================================================================
--- llvm/include/llvm/Object/IRSymtab.h
+++ llvm/include/llvm/Object/IRSymtab.h
@@ -38,6 +38,7 @@
 namespace llvm {
 
 struct BitcodeFileContents;
+class StringTableBuilder;
 
 namespace irsymtab {
 
@@ -136,9 +137,10 @@
 
 } // end namespace storage
 
-/// Fills in Symtab and Strtab with a valid symbol and string table for Mods.
+/// Fills in Symtab and StrtabBuilder with a valid symbol and string table for
+/// Mods.
 Error build(ArrayRef<Module *> Mods, SmallVector<char, 0> &Symtab,
-            SmallVector<char, 0> &Strtab);
+            StringTableBuilder &StrtabBuilder, BumpPtrAllocator &Alloc);
 
 /// This represents a symbol that has been read from a storage::Symbol and
 /// possibly a storage::Uncommon.
Index: llvm/lib/Object/IRSymtab.cpp
===================================================================
--- llvm/lib/Object/IRSymtab.cpp
+++ llvm/lib/Object/IRSymtab.cpp
@@ -46,15 +46,13 @@
 /// Stores the temporary state that is required to build an IR symbol table.
 struct Builder {
   SmallVector<char, 0> &Symtab;
-  SmallVector<char, 0> &Strtab;
+  StringTableBuilder &StrtabBuilder;
 
-  Builder(SmallVector<char, 0> &Symtab, SmallVector<char, 0> &Strtab)
-      : Symtab(Symtab), Strtab(Strtab) {}
+  Builder(SmallVector<char, 0> &Symtab, StringTableBuilder &StrtabBuilder,
+          BumpPtrAllocator &Alloc)
+      : Symtab(Symtab), StrtabBuilder(StrtabBuilder), Saver(Alloc) {}
 
-  StringTableBuilder StrtabBuilder{StringTableBuilder::RAW};
-
-  BumpPtrAllocator Alloc;
-  StringSaver Saver{Alloc};
+  StringSaver Saver;
 
   DenseMap<const Comdat *, unsigned> ComdatMap;
   Mangler Mang;
@@ -240,7 +238,7 @@
       return Err;
 
   COFFLinkerOptsOS.flush();
-  setStr(Hdr.COFFLinkerOpts, COFFLinkerOpts);
+  setStr(Hdr.COFFLinkerOpts, Saver.save(COFFLinkerOpts));
 
   // We are about to fill in the header's range fields, so reserve space for it
   // and copy it in afterwards.
@@ -251,19 +249,15 @@
   writeRange(Hdr.Uncommons, Uncommons);
 
   *reinterpret_cast<storage::Header *>(Symtab.data()) = Hdr;
-
-  raw_svector_ostream OS(Strtab);
-  StrtabBuilder.finalizeInOrder();
-  StrtabBuilder.write(OS);
-
   return Error::success();
 }
 
 } // end anonymous namespace
 
 Error irsymtab::build(ArrayRef<Module *> Mods, SmallVector<char, 0> &Symtab,
-                      SmallVector<char, 0> &Strtab) {
-  return Builder(Symtab, Strtab).build(Mods);
+                      StringTableBuilder &StrtabBuilder,
+                      BumpPtrAllocator &Alloc) {
+  return Builder(Symtab, StrtabBuilder, Alloc).build(Mods);
 }
 
 // Upgrade a vector of bitcode modules created by an old version of LLVM by
@@ -285,9 +279,15 @@
     OwnedMods.push_back(std::move(*MOrErr));
   }
 
-  if (Error E = build(Mods, FC.Symtab, FC.Strtab))
+  StringTableBuilder StrtabBuilder(StringTableBuilder::RAW);
+  BumpPtrAllocator Alloc;
+  if (Error E = build(Mods, FC.Symtab, StrtabBuilder, Alloc))
     return std::move(E);
 
+  StrtabBuilder.finalizeInOrder();
+  FC.Strtab.resize(StrtabBuilder.getSize());
+  StrtabBuilder.write((uint8_t *)FC.Strtab.data());
+
   FC.TheReader = {{FC.Symtab.data(), FC.Symtab.size()},
                   {FC.Strtab.data(), FC.Strtab.size()}};
   return std::move(FC);