LTO: Remove ModuleLoader, make loadModuleFromBuffer static and move into its only client, ThinLTOCodeGenerator.

[pcc]

Summary

This is no longer the recommended way to load modules for importing, so it should not be public API.

[mehdi_amini]

LGTM.

llvm/include/llvm/LTO/LTO.h

 
 class Error;
 class LLVMContext;
 class MemoryBufferRef;
 class Module;
 class Target;
 class raw_pwrite_stream;
 
-/// 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);
-  }
-};
-
-
 /// Resolve Weak and LinkOnce values in the \p Index. Linkage changes recorded
 /// in the index and the ThinLTO backends must apply the changes to the Module
 /// via thinLTOResolveWeakForLinkerModule.
 ///
 /// This is done for correctness (if value exported, ensure we always
 /// emit a copy), and compile-time optimization (allow drop of duplicates).
 void thinLTOResolveWeakForLinkerInIndex(
     ModuleSummaryIndex &Index,

llvm/lib/LTO/LTO.cpp

for (auto &GS : DefinedGlobals) {
     GlobalValue::LinkageTypes Linkage = GS.second->linkage();
     Hasher.update(
         ArrayRef<uint8_t>((const uint8_t *)&Linkage, sizeof(Linkage)));
   }
 
   Key = toHex(Hasher.result());
 }
 
-// Simple helper to load a module from bitcode
-std::unique_ptr<Module>
-llvm::loadModuleFromBuffer(const MemoryBufferRef &Buffer, LLVMContext &Context,
-                           bool Lazy) {
-  SMDiagnostic Err;
-  Expected<std::unique_ptr<Module>> ModuleOrErr =
-      Lazy ? getLazyBitcodeModule(Buffer, Context,
-                                  /* ShouldLazyLoadMetadata */ true)
-           : parseBitcodeFile(Buffer, Context);
-  if (!ModuleOrErr) {
-    handleAllErrors(ModuleOrErr.takeError(), [&](ErrorInfoBase &EIB) {
-      SMDiagnostic Err = SMDiagnostic(Buffer.getBufferIdentifier(),
-                                      SourceMgr::DK_Error, EIB.message());
-      Err.print("ThinLTO", errs());
-    });
-    report_fatal_error("Can't load module, abort.");
-  }
-  return std::move(ModuleOrErr.get());
-}
-
 static void thinLTOResolveWeakForLinkerGUID(
     GlobalValueSummaryList &GVSummaryList, GlobalValue::GUID GUID,
     DenseSet<GlobalValueSummary *> &GlobalInvolvedWithAlias,
     function_ref<bool(GlobalValue::GUID, const GlobalValueSummary *)>
         isPrevailing,
     function_ref<void(StringRef, GlobalValue::GUID, GlobalValue::LinkageTypes)>
         recordNewLinkage) {
   for (auto &S : GVSummaryList) {

llvm/lib/LTO/ThinLTOCodeGenerator.cpp

generateModuleMap(const std::vector<MemoryBufferRef> &Modules) {
   return ModuleMap;
 }
 
 static void promoteModule(Module &TheModule, const ModuleSummaryIndex &Index) {
   if (renameModuleForThinLTO(TheModule, Index))
     report_fatal_error("renameModuleForThinLTO failed");
 }
 
+static std::unique_ptr<Module>
+loadModuleFromBuffer(const MemoryBufferRef &Buffer, LLVMContext &Context,
+                     bool Lazy) {
+  SMDiagnostic Err;
+  Expected<std::unique_ptr<Module>> ModuleOrErr =
+      Lazy ? getLazyBitcodeModule(Buffer, Context,
+                                  /* ShouldLazyLoadMetadata */ true)
+           : parseBitcodeFile(Buffer, Context);
+  if (!ModuleOrErr) {
+    handleAllErrors(ModuleOrErr.takeError(), [&](ErrorInfoBase &EIB) {
+      SMDiagnostic Err = SMDiagnostic(Buffer.getBufferIdentifier(),
+                                      SourceMgr::DK_Error, EIB.message());
+      Err.print("ThinLTO", errs());
+    });
+    report_fatal_error("Can't load module, abort.");
+  }
+  return std::move(ModuleOrErr.get());
+}
+
 static void
 crossImportIntoModule(Module &TheModule, const ModuleSummaryIndex &Index,
                       StringMap<MemoryBufferRef> &ModuleMap,
                       const FunctionImporter::ImportMapTy &ImportList) {
-  ModuleLoader Loader(TheModule.getContext(), ModuleMap);
+  auto Loader = [&](StringRef Identifier) {
+    return loadModuleFromBuffer(ModuleMap[Identifier], TheModule.getContext(),
+                                /*Lazy=*/true);
+  };
+
   FunctionImporter Importer(Index, Loader);
   if (!Importer.importFunctions(TheModule, ImportList))
     report_fatal_error("importFunctions failed");
 }
 
 static void optimizeModule(Module &TheModule, TargetMachine &TM) {
   // Populate the PassManager
   PassManagerBuilder PMB;