Index: llvm/trunk/include/llvm/Object/IRObjectFile.h
===================================================================
--- llvm/trunk/include/llvm/Object/IRObjectFile.h
+++ llvm/trunk/include/llvm/Object/IRObjectFile.h
@@ -15,6 +15,7 @@
 #define LLVM_OBJECT_IROBJECTFILE_H
 
 #include "llvm/ADT/PointerUnion.h"
+#include "llvm/Object/IRSymtab.h"
 #include "llvm/Object/ModuleSymbolTable.h"
 #include "llvm/Object/SymbolicFile.h"
 
@@ -61,7 +62,20 @@
   static Expected<std::unique_ptr<IRObjectFile>> create(MemoryBufferRef Object,
                                                         LLVMContext &Context);
 };
+
+/// The contents of a bitcode file and its irsymtab. Any underlying data
+/// for the irsymtab are owned by Symtab and Strtab.
+struct IRSymtabFile {
+  std::vector<BitcodeModule> Mods;
+  SmallVector<char, 0> Symtab, Strtab;
+  irsymtab::Reader TheReader;
+};
+
+/// Reads a bitcode file, creating its irsymtab if necessary.
+Expected<IRSymtabFile> readIRSymtab(MemoryBufferRef MBRef);
+
 }
+
 }
 
 #endif
Index: llvm/trunk/include/llvm/Object/IRSymtab.h
===================================================================
--- llvm/trunk/include/llvm/Object/IRSymtab.h
+++ llvm/trunk/include/llvm/Object/IRSymtab.h
@@ -36,6 +36,9 @@
 #include <vector>
 
 namespace llvm {
+
+class BitcodeModule;
+
 namespace irsymtab {
 
 namespace storage {
@@ -314,6 +317,16 @@
           SymbolRef(MEnd, MEnd, nullptr, this)};
 }
 
+/// The contents of the irsymtab in a bitcode file. Any underlying data for the
+/// irsymtab are owned by Symtab and Strtab.
+struct FileContents {
+  SmallVector<char, 0> Symtab, Strtab;
+  Reader TheReader;
+};
+
+/// Reads the contents of a bitcode file, creating its irsymtab if necessary.
+Expected<FileContents> readBitcode(ArrayRef<BitcodeModule> Mods);
+
 } // end namespace irsymtab
 } // end namespace llvm
 
Index: llvm/trunk/lib/LTO/LTO.cpp
===================================================================
--- llvm/trunk/lib/LTO/LTO.cpp
+++ llvm/trunk/lib/LTO/LTO.cpp
@@ -315,54 +315,19 @@
 Expected<std::unique_ptr<InputFile>> InputFile::create(MemoryBufferRef Object) {
   std::unique_ptr<InputFile> File(new InputFile);
 
-  ErrorOr<MemoryBufferRef> BCOrErr =
-      IRObjectFile::findBitcodeInMemBuffer(Object);
-  if (!BCOrErr)
-    return errorCodeToError(BCOrErr.getError());
-
-  Expected<std::vector<BitcodeModule>> BMsOrErr =
-      getBitcodeModuleList(*BCOrErr);
-  if (!BMsOrErr)
-    return BMsOrErr.takeError();
-
-  if (BMsOrErr->empty())
-    return make_error<StringError>("Bitcode file does not contain any modules",
-                                   inconvertibleErrorCode());
-
-  File->Mods = *BMsOrErr;
-
-  LLVMContext Ctx;
-  std::vector<Module *> Mods;
-  std::vector<std::unique_ptr<Module>> OwnedMods;
-  for (auto BM : *BMsOrErr) {
-    Expected<std::unique_ptr<Module>> MOrErr =
-        BM.getLazyModule(Ctx, /*ShouldLazyLoadMetadata*/ true,
-                         /*IsImporting*/ false);
-    if (!MOrErr)
-      return MOrErr.takeError();
-
-    if ((*MOrErr)->getDataLayoutStr().empty())
-      return make_error<StringError>("input module has no datalayout",
-                                     inconvertibleErrorCode());
-
-    Mods.push_back(MOrErr->get());
-    OwnedMods.push_back(std::move(*MOrErr));
-  }
-
-  SmallVector<char, 0> Symtab;
-  if (Error E = irsymtab::build(Mods, Symtab, File->Strtab))
-    return std::move(E);
-
-  irsymtab::Reader R({Symtab.data(), Symtab.size()},
-                     {File->Strtab.data(), File->Strtab.size()});
-  File->TargetTriple = R.getTargetTriple();
-  File->SourceFileName = R.getSourceFileName();
-  File->COFFLinkerOpts = R.getCOFFLinkerOpts();
-  File->ComdatTable = R.getComdatTable();
+  Expected<IRSymtabFile> FOrErr = readIRSymtab(Object);
+  if (!FOrErr)
+    return FOrErr.takeError();
+
+  File->TargetTriple = FOrErr->TheReader.getTargetTriple();
+  File->SourceFileName = FOrErr->TheReader.getSourceFileName();
+  File->COFFLinkerOpts = FOrErr->TheReader.getCOFFLinkerOpts();
+  File->ComdatTable = FOrErr->TheReader.getComdatTable();
 
-  for (unsigned I = 0; I != Mods.size(); ++I) {
+  for (unsigned I = 0; I != FOrErr->Mods.size(); ++I) {
     size_t Begin = File->Symbols.size();
-    for (const irsymtab::Reader::SymbolRef &Sym : R.module_symbols(I))
+    for (const irsymtab::Reader::SymbolRef &Sym :
+         FOrErr->TheReader.module_symbols(I))
       // Skip symbols that are irrelevant to LTO. Note that this condition needs
       // to match the one in Skip() in LTO::addRegularLTO().
       if (Sym.isGlobal() && !Sym.isFormatSpecific())
@@ -370,6 +335,8 @@
     File->ModuleSymIndices.push_back({Begin, File->Symbols.size()});
   }
 
+  File->Mods = FOrErr->Mods;
+  File->Strtab = std::move(FOrErr->Strtab);
   return std::move(File);
 }
 
Index: llvm/trunk/lib/Object/IRObjectFile.cpp
===================================================================
--- llvm/trunk/lib/Object/IRObjectFile.cpp
+++ llvm/trunk/lib/Object/IRObjectFile.cpp
@@ -139,3 +139,26 @@
   return std::unique_ptr<IRObjectFile>(
       new IRObjectFile(*BCOrErr, std::move(Mods)));
 }
+
+Expected<IRSymtabFile> object::readIRSymtab(MemoryBufferRef MBRef) {
+  IRSymtabFile F;
+  ErrorOr<MemoryBufferRef> BCOrErr =
+      IRObjectFile::findBitcodeInMemBuffer(MBRef);
+  if (!BCOrErr)
+    return errorCodeToError(BCOrErr.getError());
+
+  Expected<std::vector<BitcodeModule>> BMsOrErr =
+      getBitcodeModuleList(*BCOrErr);
+  if (!BMsOrErr)
+    return BMsOrErr.takeError();
+
+  Expected<irsymtab::FileContents> FCOrErr = irsymtab::readBitcode(*BMsOrErr);
+  if (!FCOrErr)
+    return FCOrErr.takeError();
+
+  F.Mods = std::move(*BMsOrErr);
+  F.Symtab = std::move(FCOrErr->Symtab);
+  F.Strtab = std::move(FCOrErr->Strtab);
+  F.TheReader = std::move(FCOrErr->TheReader);
+  return std::move(F);
+}
Index: llvm/trunk/lib/Object/IRSymtab.cpp
===================================================================
--- llvm/trunk/lib/Object/IRSymtab.cpp
+++ llvm/trunk/lib/Object/IRSymtab.cpp
@@ -23,7 +23,9 @@
 #include "llvm/IR/Mangler.h"
 #include "llvm/IR/Metadata.h"
 #include "llvm/IR/Module.h"
+#include "llvm/Bitcode/BitcodeReader.h"
 #include "llvm/MC/StringTableBuilder.h"
+#include "llvm/Object/IRObjectFile.h"
 #include "llvm/Object/ModuleSymbolTable.h"
 #include "llvm/Object/SymbolicFile.h"
 #include "llvm/Support/Allocator.h"
@@ -259,3 +261,35 @@
                       SmallVector<char, 0> &Strtab) {
   return Builder(Symtab, Strtab).build(Mods);
 }
+
+Expected<FileContents> irsymtab::readBitcode(ArrayRef<BitcodeModule> BMs) {
+  FileContents FC;
+  if (BMs.empty())
+    return make_error<StringError>("Bitcode file does not contain any modules",
+                                   inconvertibleErrorCode());
+
+  LLVMContext Ctx;
+  std::vector<Module *> Mods;
+  std::vector<std::unique_ptr<Module>> OwnedMods;
+  for (auto BM : BMs) {
+    Expected<std::unique_ptr<Module>> MOrErr =
+        BM.getLazyModule(Ctx, /*ShouldLazyLoadMetadata*/ true,
+                         /*IsImporting*/ false);
+    if (!MOrErr)
+      return MOrErr.takeError();
+
+    if ((*MOrErr)->getDataLayoutStr().empty())
+      return make_error<StringError>("input module has no datalayout",
+                                     inconvertibleErrorCode());
+
+    Mods.push_back(MOrErr->get());
+    OwnedMods.push_back(std::move(*MOrErr));
+  }
+
+  if (Error E = build(Mods, FC.Symtab, FC.Strtab))
+    return std::move(E);
+
+  FC.TheReader = {{FC.Symtab.data(), FC.Symtab.size()},
+                  {FC.Strtab.data(), FC.Strtab.size()}};
+  return std::move(FC);
+}