[ThinLTO] Refactor module loader handling into new LTO file (NFC)

Moved the ModuleLoader and supporting helper loadModuleFromBuffer out of
ThinLTOCodeGenerator and into new LTO.h/LTO.cpp files. This is in
preparation for a patch that will utilize these in the gold-plugin.

Note that there are some other pending patches (D20268 and D20290) that
also plan to refactor common interfaces and functionality into this same
pair of new files.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@270509 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 96 insertions, 43 deletions

diff --git a/include/llvm/LTO/LTO.h b/include/llvm/LTO/LTO.h
new file mode 100644
index 00000000000..34c20f2074d
--- /dev/null
+++ b/include/llvm/LTO/LTO.h
@@ -0,0 +1,52 @@
+//===-LTO.h - LLVM Link Time Optimizer ------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares functions and classes used to support LTO. It is intended
+// to be used both by LTO classes as well as by clients (gold-plugin) that
+// don't utilize the LTO code generator interfaces.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LTO_LTO_H
+#define LLVM_LTO_LTO_H
+
+#include "llvm/ADT/StringMap.h"
+
+namespace llvm {
+
+class LLVMContext;
+class MemoryBufferRef;
+class Module;
+
+/// Helper to load a module from bitcode.
+std::unique_ptr<Module> loadModuleFromBuffer(const MemoryBufferRef &Buffer,
+                                             LLVMContext &Context, bool Lazy);
+
+/// Provide a "loader" for the FunctionImporter to access function from other
+/// modules.
+class ModuleLoader {
+  /// The context that will be used for importing.
+  LLVMContext &Context;
+
+  /// Map from Module identifier to MemoryBuffer. Used by clients like the
+  /// FunctionImported to request loading a Module.
+  StringMap<MemoryBufferRef> &ModuleMap;
+
+public:
+  ModuleLoader(LLVMContext &Context, StringMap<MemoryBufferRef> &ModuleMap)
+      : Context(Context), ModuleMap(ModuleMap) {}
+
+  /// Load a module on demand.
+  std::unique_ptr<Module> operator()(StringRef Identifier) {
+    return loadModuleFromBuffer(ModuleMap[Identifier], Context, /*Lazy*/ true);
+  }
+};
+}
+
+#endif
diff --git a/lib/LTO/CMakeLists.txt b/lib/LTO/CMakeLists.txt
index cf6a7d16d20..2007ef21a61 100644
--- a/lib/LTO/CMakeLists.txt
+++ b/lib/LTO/CMakeLists.txt
@@ -48,6 +48,7 @@ endif()
 
 
 add_llvm_library(LLVMLTO
+  LTO.cpp
   LTOModule.cpp
   LTOCodeGenerator.cpp
   UpdateCompilerUsed.cpp
diff --git a/lib/LTO/LTO.cpp b/lib/LTO/LTO.cpp
new file mode 100644
index 00000000000..5f89e5c95a7
--- /dev/null
+++ b/lib/LTO/LTO.cpp
@@ -0,0 +1,42 @@
+//===-LTO.cpp - LLVM Link Time Optimizer ----------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements functions and classes used to support LTO.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/LTO/LTO.h"
+#include "llvm/Bitcode/ReaderWriter.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/SourceMgr.h"
+#include "llvm/Support/raw_ostream.h"
+
+namespace llvm {
+
+// Simple helper to load a module from bitcode
+std::unique_ptr<Module> loadModuleFromBuffer(const MemoryBufferRef &Buffer,
+                                             LLVMContext &Context, bool Lazy) {
+  SMDiagnostic Err;
+  ErrorOr<std::unique_ptr<Module>> ModuleOrErr(nullptr);
+  if (Lazy) {
+    ModuleOrErr =
+        getLazyBitcodeModule(MemoryBuffer::getMemBuffer(Buffer, false), Context,
+                             /* ShouldLazyLoadMetadata */ Lazy);
+  } else {
+    ModuleOrErr = parseBitcodeFile(Buffer, Context);
+  }
+  if (std::error_code EC = ModuleOrErr.getError()) {
+    Err = SMDiagnostic(Buffer.getBufferIdentifier(), SourceMgr::DK_Error,
+                       EC.message());
+    Err.print("ThinLTO", errs());
+    report_fatal_error("Can't load module, abort.");
+  }
+  return std::move(ModuleOrErr.get());
+}
+}
diff --git a/lib/LTO/ThinLTOCodeGenerator.cpp b/lib/LTO/ThinLTOCodeGenerator.cpp
index 83eb14c1faf..b90d0d81b60 100644
--- a/lib/LTO/ThinLTOCodeGenerator.cpp
+++ b/lib/LTO/ThinLTOCodeGenerator.cpp
@@ -32,6 +32,7 @@
 #include "llvm/IR/LegacyPassManager.h"
 #include "llvm/IR/Mangler.h"
 #include "llvm/IRReader/IRReader.h"
+#include "llvm/LTO/LTO.h"
 #include "llvm/Linker/Linker.h"
 #include "llvm/MC/SubtargetFeature.h"
 #include "llvm/Object/IRObjectFile.h"
@@ -41,7 +42,6 @@
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Path.h"
 #include "llvm/Support/SHA1.h"
-#include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Support/ThreadPool.h"
 #include "llvm/Target/TargetMachine.h"
@@ -74,28 +74,6 @@ static void diagnosticHandler(const DiagnosticInfo &DI) {
   errs() << '\n';
 }
 
-// Simple helper to load a module from bitcode
-static std::unique_ptr<Module>
-loadModuleFromBuffer(const MemoryBufferRef &Buffer, LLVMContext &Context,
-                     bool Lazy) {
-  SMDiagnostic Err;
-  ErrorOr<std::unique_ptr<Module>> ModuleOrErr(nullptr);
-  if (Lazy) {
-    ModuleOrErr =
-        getLazyBitcodeModule(MemoryBuffer::getMemBuffer(Buffer, false), Context,
-                             /* ShouldLazyLoadMetadata */ Lazy);
-  } else {
-    ModuleOrErr = parseBitcodeFile(Buffer, Context);
-  }
-  if (std::error_code EC = ModuleOrErr.getError()) {
-    Err = SMDiagnostic(Buffer.getBufferIdentifier(), SourceMgr::DK_Error,
-                       EC.message());
-    Err.print("ThinLTO", errs());
-    report_fatal_error("Can't load module, abort.");
-  }
-  return std::move(ModuleOrErr.get());
-}
-
 // Simple helper to save temporary files for debug.
 static void saveTempBitcode(const Module &TheModule, StringRef TempDir,
                             unsigned count, StringRef Suffix) {
@@ -260,26 +238,6 @@ generateModuleMap(const std::vector<MemoryBufferRef> &Modules) {
   return ModuleMap;
 }
 
-/// Provide a "loader" for the FunctionImporter to access function from other
-/// modules.
-class ModuleLoader {
-  /// The context that will be used for importing.
-  LLVMContext &Context;
-
-  /// Map from Module identifier to MemoryBuffer. Used by clients like the
-  /// FunctionImported to request loading a Module.
-  StringMap<MemoryBufferRef> &ModuleMap;
-
-public:
-  ModuleLoader(LLVMContext &Context, StringMap<MemoryBufferRef> &ModuleMap)
-      : Context(Context), ModuleMap(ModuleMap) {}
-
-  /// Load a module on demand.
-  std::unique_ptr<Module> operator()(StringRef Identifier) {
-    return loadModuleFromBuffer(ModuleMap[Identifier], Context, /*Lazy*/ true);
-  }
-};
-
 static void promoteModule(Module &TheModule, const ModuleSummaryIndex &Index) {
   if (renameModuleForThinLTO(TheModule, Index))
     report_fatal_error("renameModuleForThinLTO failed");