[ThinLTO] Fix ThinLTOCodegenerator to export llvm.used symbols

Summary:
ThinLTOCodeGenerator currently does not preserve llvm.used symbols and
it can internalize them. In order to pass the necessary information to the
legacy ThinLTOCodeGenerator, the input to the code generator is
rewritten to be based on lto::InputFile.

This fixes: PR41236
rdar://problem/49293439

Reviewers: tejohnson, pcc, dexonsmith

Reviewed By: tejohnson

Subscribers: mehdi_amini, inglorion, eraman, hiraditya, jkorous, dang, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D60226

llvm-svn: 357931

7 files changed, 184 insertions, 99 deletions

diff --git a/llvm/include/llvm/LTO/LTO.h b/llvm/include/llvm/LTO/LTO.h
index be37dbd0c59..24e80fbd09e 100644
--- a/llvm/include/llvm/LTO/LTO.h
+++ b/llvm/include/llvm/LTO/LTO.h
@@ -131,6 +131,7 @@ public:
     using irsymtab::Symbol::isWeak;
     using irsymtab::Symbol::isIndirect;
     using irsymtab::Symbol::getName;
+    using irsymtab::Symbol::getIRName;
     using irsymtab::Symbol::getVisibility;
     using irsymtab::Symbol::canBeOmittedFromSymbolTable;
     using irsymtab::Symbol::isTLS;
@@ -161,6 +162,9 @@ public:
   // Returns a table with all the comdats used by this file.
   ArrayRef<StringRef> getComdatTable() const { return ComdatTable; }
 
+  // Returns the only BitcodeModule from InputFile.
+  BitcodeModule &getSingleBitcodeModule();
+
 private:
   ArrayRef<Symbol> module_symbols(unsigned I) const {
     const auto &Indices = ModuleSymIndices[I];
diff --git a/llvm/include/llvm/LTO/legacy/ThinLTOCodeGenerator.h b/llvm/include/llvm/LTO/legacy/ThinLTOCodeGenerator.h
index 1730e83628d..28a85f03427 100644
--- a/llvm/include/llvm/LTO/legacy/ThinLTOCodeGenerator.h
+++ b/llvm/include/llvm/LTO/legacy/ThinLTOCodeGenerator.h
@@ -19,6 +19,7 @@
 #include "llvm/ADT/StringSet.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/IR/ModuleSummaryIndex.h"
+#include "llvm/LTO/LTO.h"
 #include "llvm/Support/CachePruning.h"
 #include "llvm/Support/CodeGen.h"
 #include "llvm/Support/MemoryBuffer.h"
@@ -31,23 +32,6 @@ class StringRef;
 class LLVMContext;
 class TargetMachine;
 
-/// Wrapper around MemoryBufferRef, owning the identifier
-class ThinLTOBuffer {
-  std::string OwnedIdentifier;
-  StringRef Buffer;
-
-public:
-  ThinLTOBuffer(StringRef Buffer, StringRef Identifier)
-      : OwnedIdentifier(Identifier), Buffer(Buffer) {}
-
-  MemoryBufferRef getMemBuffer() const {
-    return MemoryBufferRef(Buffer,
-                           {OwnedIdentifier.c_str(), OwnedIdentifier.size()});
-  }
-  StringRef getBuffer() const { return Buffer; }
-  StringRef getBufferIdentifier() const { return OwnedIdentifier; }
-};
-
 /// Helper to gather options relevant to the target machine creation
 struct TargetMachineBuilder {
   Triple TheTriple;
@@ -267,31 +251,36 @@ public:
    * and additionally resolve weak and linkonce symbols.
    * Index is updated to reflect linkage changes from weak resolution.
    */
-  void promote(Module &Module, ModuleSummaryIndex &Index);
+  void promote(Module &Module, ModuleSummaryIndex &Index,
+               const lto::InputFile &File);
 
   /**
    * Compute and emit the imported files for module at \p ModulePath.
    */
   void emitImports(Module &Module, StringRef OutputName,
-                   ModuleSummaryIndex &Index);
+                   ModuleSummaryIndex &Index,
+                   const lto::InputFile &File);
 
   /**
    * Perform cross-module importing for the module identified by
    * ModuleIdentifier.
    */
-  void crossModuleImport(Module &Module, ModuleSummaryIndex &Index);
+  void crossModuleImport(Module &Module, ModuleSummaryIndex &Index,
+                         const lto::InputFile &File);
 
   /**
    * Compute the list of summaries needed for importing into module.
    */
   void gatherImportedSummariesForModule(
       Module &Module, ModuleSummaryIndex &Index,
-      std::map<std::string, GVSummaryMapTy> &ModuleToSummariesForIndex);
+      std::map<std::string, GVSummaryMapTy> &ModuleToSummariesForIndex,
+      const lto::InputFile &File);
 
   /**
    * Perform internalization. Index is updated to reflect linkage changes.
    */
-  void internalize(Module &Module, ModuleSummaryIndex &Index);
+  void internalize(Module &Module, ModuleSummaryIndex &Index,
+                   const lto::InputFile &File);
 
   /**
    * Perform post-importing ThinLTO optimizations.
@@ -313,7 +302,7 @@ private:
 
   /// Vector holding the input buffers containing the bitcode modules to
   /// process.
-  std::vector<ThinLTOBuffer> Modules;
+  std::vector<std::unique_ptr<lto::InputFile>> Modules;
 
   /// Set of symbols that need to be preserved outside of the set of bitcode
   /// files.
diff --git a/llvm/lib/LTO/LTO.cpp b/llvm/lib/LTO/LTO.cpp
index 99318c19a89..1accbf40b96 100644
--- a/llvm/lib/LTO/LTO.cpp
+++ b/llvm/lib/LTO/LTO.cpp
@@ -420,6 +420,11 @@ StringRef InputFile::getName() const {
   return Mods[0].getModuleIdentifier();
 }
 
+BitcodeModule &InputFile::getSingleBitcodeModule() {
+  assert(Mods.size() == 1 && "Expect only one bitcode module");
+  return Mods[0];
+}
+
 LTO::RegularLTOState::RegularLTOState(unsigned ParallelCodeGenParallelismLevel,
                                       Config &Conf)
     : ParallelCodeGenParallelismLevel(ParallelCodeGenParallelismLevel),
diff --git a/llvm/lib/LTO/ThinLTOCodeGenerator.cpp b/llvm/lib/LTO/ThinLTOCodeGenerator.cpp
index d4ee66a53e0..0423db85b81 100644
--- a/llvm/lib/LTO/ThinLTOCodeGenerator.cpp
+++ b/llvm/lib/LTO/ThinLTOCodeGenerator.cpp
@@ -135,14 +135,13 @@ static void computePrevailingCopies(
   }
 }
 
-static StringMap<MemoryBufferRef>
-generateModuleMap(const std::vector<ThinLTOBuffer> &Modules) {
-  StringMap<MemoryBufferRef> ModuleMap;
-  for (auto &ModuleBuffer : Modules) {
-    assert(ModuleMap.find(ModuleBuffer.getBufferIdentifier()) ==
-               ModuleMap.end() &&
+static StringMap<lto::InputFile *>
+generateModuleMap(std::vector<std::unique_ptr<lto::InputFile>> &Modules) {
+  StringMap<lto::InputFile *> ModuleMap;
+  for (auto &M : Modules) {
+    assert(ModuleMap.find(M->getName()) == ModuleMap.end() &&
            "Expect unique Buffer Identifier");
-    ModuleMap[ModuleBuffer.getBufferIdentifier()] = ModuleBuffer.getMemBuffer();
+    ModuleMap[M->getName()] = M.get();
   }
   return ModuleMap;
 }
@@ -175,18 +174,19 @@ static void verifyLoadedModule(Module &TheModule) {
   }
 }
 
-static std::unique_ptr<Module>
-loadModuleFromBuffer(const MemoryBufferRef &Buffer, LLVMContext &Context,
-                     bool Lazy, bool IsImporting) {
+static std::unique_ptr<Module> loadModuleFromInput(lto::InputFile *Input,
+                                                   LLVMContext &Context,
+                                                   bool Lazy,
+                                                   bool IsImporting) {
+  auto &Mod = Input->getSingleBitcodeModule();
   SMDiagnostic Err;
   Expected<std::unique_ptr<Module>> ModuleOrErr =
-      Lazy
-          ? getLazyBitcodeModule(Buffer, Context,
-                                 /* ShouldLazyLoadMetadata */ true, IsImporting)
-          : parseBitcodeFile(Buffer, Context);
+      Lazy ? Mod.getLazyModule(Context,
+                               /* ShouldLazyLoadMetadata */ true, IsImporting)
+           : Mod.parseModule(Context);
   if (!ModuleOrErr) {
     handleAllErrors(ModuleOrErr.takeError(), [&](ErrorInfoBase &EIB) {
-      SMDiagnostic Err = SMDiagnostic(Buffer.getBufferIdentifier(),
+      SMDiagnostic Err = SMDiagnostic(Mod.getModuleIdentifier(),
                                       SourceMgr::DK_Error, EIB.message());
       Err.print("ThinLTO", errs());
     });
@@ -194,16 +194,17 @@ loadModuleFromBuffer(const MemoryBufferRef &Buffer, LLVMContext &Context,
   }
   if (!Lazy)
     verifyLoadedModule(*ModuleOrErr.get());
-  return std::move(ModuleOrErr.get());
+  return std::move(*ModuleOrErr);
 }
 
 static void
 crossImportIntoModule(Module &TheModule, const ModuleSummaryIndex &Index,
-                      StringMap<MemoryBufferRef> &ModuleMap,
+                      StringMap<lto::InputFile*> &ModuleMap,
                       const FunctionImporter::ImportMapTy &ImportList) {
   auto Loader = [&](StringRef Identifier) {
-    return loadModuleFromBuffer(ModuleMap[Identifier], TheModule.getContext(),
-                                /*Lazy=*/true, /*IsImporting*/ true);
+    auto &Input = ModuleMap[Identifier];
+    return loadModuleFromInput(Input, TheModule.getContext(),
+                               /*Lazy=*/true, /*IsImporting*/ true);
   };
 
   FunctionImporter Importer(Index, Loader);
@@ -248,6 +249,15 @@ static void optimizeModule(Module &TheModule, TargetMachine &TM,
   PM.run(TheModule);
 }
 
+static void
+addUsedSymbolToPreservedGUID(const lto::InputFile &File,
+                             DenseSet<GlobalValue::GUID> &PreservedGUID) {
+  for (const auto &Sym : File.symbols()) {
+    if (Sym.isUsed())
+      PreservedGUID.insert(GlobalValue::getGUID(Sym.getIRName()));
+  }
+}
+
 // Convert the PreservedSymbols map from "Name" based to "GUID" based.
 static DenseSet<GlobalValue::GUID>
 computeGUIDPreservedSymbols(const StringSet<> &PreservedSymbols,
@@ -381,7 +391,7 @@ public:
 
 static std::unique_ptr<MemoryBuffer>
 ProcessThinLTOModule(Module &TheModule, ModuleSummaryIndex &Index,
-                     StringMap<MemoryBufferRef> &ModuleMap, TargetMachine &TM,
+                     StringMap<lto::InputFile *> &ModuleMap, TargetMachine &TM,
                      const FunctionImporter::ImportMapTy &ImportList,
                      const FunctionImporter::ExportSetTy &ExportList,
                      const DenseSet<GlobalValue::GUID> &GUIDPreservedSymbols,
@@ -488,15 +498,13 @@ static void initTMBuilder(TargetMachineBuilder &TMBuilder,
 } // end anonymous namespace
 
 void ThinLTOCodeGenerator::addModule(StringRef Identifier, StringRef Data) {
-  ThinLTOBuffer Buffer(Data, Identifier);
-  LLVMContext Context;
-  StringRef TripleStr;
-  ErrorOr<std::string> TripleOrErr = expectedToErrorOrAndEmitErrors(
-      Context, getBitcodeTargetTriple(Buffer.getMemBuffer()));
+  MemoryBufferRef Buffer(Data, Identifier);
 
-  if (TripleOrErr)
-    TripleStr = *TripleOrErr;
+  auto InputOrError = lto::InputFile::create(Buffer);
+  if (!InputOrError)
+    report_fatal_error("ThinLTO cannot create input file");
 
+  auto TripleStr = (*InputOrError)->getTargetTriple();
   Triple TheTriple(TripleStr);
 
   if (Modules.empty())
@@ -508,7 +516,7 @@ void ThinLTOCodeGenerator::addModule(StringRef Identifier, StringRef Data) {
     initTMBuilder(TMBuilder, Triple(TMBuilder.TheTriple.merge(TheTriple)));
   }
 
-  Modules.push_back(Buffer);
+  Modules.emplace_back(std::move(*InputOrError));
 }
 
 void ThinLTOCodeGenerator::preserveSymbol(StringRef Name) {
@@ -549,9 +557,10 @@ std::unique_ptr<ModuleSummaryIndex> ThinLTOCodeGenerator::linkCombinedIndex() {
   std::unique_ptr<ModuleSummaryIndex> CombinedIndex =
       llvm::make_unique<ModuleSummaryIndex>(/*HaveGVs=*/false);
   uint64_t NextModuleId = 0;
-  for (auto &ModuleBuffer : Modules) {
-    if (Error Err = readModuleSummaryIndex(ModuleBuffer.getMemBuffer(),
-                                           *CombinedIndex, NextModuleId++)) {
+  for (auto &Mod : Modules) {
+    auto &M = Mod->getSingleBitcodeModule();
+    if (Error Err =
+            M.readSummary(*CombinedIndex, Mod->getName(), NextModuleId++)) {
       // FIXME diagnose
       logAllUnhandledErrors(
           std::move(Err), errs(),
@@ -593,8 +602,8 @@ static void computeDeadSymbolsInIndex(
  * Perform promotion and renaming of exported internal functions.
  * Index is updated to reflect linkage changes from weak resolution.
  */
-void ThinLTOCodeGenerator::promote(Module &TheModule,
-                                   ModuleSummaryIndex &Index) {
+void ThinLTOCodeGenerator::promote(Module &TheModule, ModuleSummaryIndex &Index,
+                                   const lto::InputFile &File) {
   auto ModuleCount = Index.modulePaths().size();
   auto ModuleIdentifier = TheModule.getModuleIdentifier();
 
@@ -606,6 +615,9 @@ void ThinLTOCodeGenerator::promote(Module &TheModule,
   auto GUIDPreservedSymbols = computeGUIDPreservedSymbols(
       PreservedSymbols, Triple(TheModule.getTargetTriple()));
 
+  // Add used symbol to the preserved symbols.
+  addUsedSymbolToPreservedGUID(File, GUIDPreservedSymbols);
+
   // Compute "dead" symbols, we don't want to import/export these!
   computeDeadSymbolsInIndex(Index, GUIDPreservedSymbols);
 
@@ -619,21 +631,22 @@ void ThinLTOCodeGenerator::promote(Module &TheModule,
   StringMap<std::map<GlobalValue::GUID, GlobalValue::LinkageTypes>> ResolvedODR;
   resolvePrevailingInIndex(Index, ResolvedODR);
 
-  thinLTOResolvePrevailingInModule(
-      TheModule, ModuleToDefinedGVSummaries[ModuleIdentifier]);
-
   // Promote the exported values in the index, so that they are promoted
   // in the module.
   internalizeAndPromoteInIndex(ExportLists, GUIDPreservedSymbols, Index);
 
   promoteModule(TheModule, Index);
+
+  thinLTOResolvePrevailingInModule(
+      TheModule, ModuleToDefinedGVSummaries[ModuleIdentifier]);
 }
 
 /**
  * Perform cross-module importing for the module identified by ModuleIdentifier.
  */
 void ThinLTOCodeGenerator::crossModuleImport(Module &TheModule,
-                                             ModuleSummaryIndex &Index) {
+                                             ModuleSummaryIndex &Index,
+                                             const lto::InputFile &File) {
   auto ModuleMap = generateModuleMap(Modules);
   auto ModuleCount = Index.modulePaths().size();
 
@@ -645,6 +658,8 @@ void ThinLTOCodeGenerator::crossModuleImport(Module &TheModule,
   auto GUIDPreservedSymbols = computeGUIDPreservedSymbols(
       PreservedSymbols, Triple(TheModule.getTargetTriple()));
 
+  addUsedSymbolToPreservedGUID(File, GUIDPreservedSymbols);
+
   // Compute "dead" symbols, we don't want to import/export these!
   computeDeadSymbolsInIndex(Index, GUIDPreservedSymbols);
 
@@ -663,7 +678,8 @@ void ThinLTOCodeGenerator::crossModuleImport(Module &TheModule,
  */
 void ThinLTOCodeGenerator::gatherImportedSummariesForModule(
     Module &TheModule, ModuleSummaryIndex &Index,
-    std::map<std::string, GVSummaryMapTy> &ModuleToSummariesForIndex) {
+    std::map<std::string, GVSummaryMapTy> &ModuleToSummariesForIndex,
+    const lto::InputFile &File) {
   auto ModuleCount = Index.modulePaths().size();
   auto ModuleIdentifier = TheModule.getModuleIdentifier();
 
@@ -675,6 +691,8 @@ void ThinLTOCodeGenerator::gatherImportedSummariesForModule(
   auto GUIDPreservedSymbols = computeGUIDPreservedSymbols(
       PreservedSymbols, Triple(TheModule.getTargetTriple()));
 
+  addUsedSymbolToPreservedGUID(File, GUIDPreservedSymbols);
+
   // Compute "dead" symbols, we don't want to import/export these!
   computeDeadSymbolsInIndex(Index, GUIDPreservedSymbols);
 
@@ -693,7 +711,8 @@ void ThinLTOCodeGenerator::gatherImportedSummariesForModule(
  * Emit the list of files needed for importing into module.
  */
 void ThinLTOCodeGenerator::emitImports(Module &TheModule, StringRef OutputName,
-                                       ModuleSummaryIndex &Index) {
+                                       ModuleSummaryIndex &Index,
+                                       const lto::InputFile &File) {
   auto ModuleCount = Index.modulePaths().size();
   auto ModuleIdentifier = TheModule.getModuleIdentifier();
 
@@ -705,6 +724,8 @@ void ThinLTOCodeGenerator::emitImports(Module &TheModule, StringRef OutputName,
   auto GUIDPreservedSymbols = computeGUIDPreservedSymbols(
       PreservedSymbols, Triple(TheModule.getTargetTriple()));
 
+  addUsedSymbolToPreservedGUID(File, GUIDPreservedSymbols);
+
   // Compute "dead" symbols, we don't want to import/export these!
   computeDeadSymbolsInIndex(Index, GUIDPreservedSymbols);
 
@@ -730,7 +751,8 @@ void ThinLTOCodeGenerator::emitImports(Module &TheModule, StringRef OutputName,
  * Perform internalization. Index is updated to reflect linkage changes.
  */
 void ThinLTOCodeGenerator::internalize(Module &TheModule,
-                                       ModuleSummaryIndex &Index) {
+                                       ModuleSummaryIndex &Index,
+                                       const lto::InputFile &File) {
   initTMBuilder(TMBuilder, Triple(TheModule.getTargetTriple()));
   auto ModuleCount = Index.modulePaths().size();
   auto ModuleIdentifier = TheModule.getModuleIdentifier();
@@ -739,6 +761,8 @@ void ThinLTOCodeGenerator::internalize(Module &TheModule,
   auto GUIDPreservedSymbols =
       computeGUIDPreservedSymbols(PreservedSymbols, TMBuilder.TheTriple);
 
+  addUsedSymbolToPreservedGUID(File, GUIDPreservedSymbols);
+
   // Collect for each module the list of function it defines (GUID -> Summary).
   StringMap<GVSummaryMapTy> ModuleToDefinedGVSummaries(ModuleCount);
   Index.collectDefinedGVSummariesPerModule(ModuleToDefinedGVSummaries);
@@ -830,15 +854,14 @@ void ThinLTOCodeGenerator::run() {
     // Perform only parallel codegen and return.
     ThreadPool Pool;
     int count = 0;
-    for (auto &ModuleBuffer : Modules) {
+    for (auto &Mod : Modules) {
       Pool.async([&](int count) {
         LLVMContext Context;
         Context.setDiscardValueNames(LTODiscardValueNames);
 
         // Parse module now
-        auto TheModule =
-            loadModuleFromBuffer(ModuleBuffer.getMemBuffer(), Context, false,
-                                 /*IsImporting*/ false);
+        auto TheModule = loadModuleFromInput(Mod.get(), Context, false,
+                                             /*IsImporting*/ false);
 
         // CodeGen
         auto OutputBuffer = codegenModule(*TheModule, *TMBuilder.create());
@@ -881,6 +904,10 @@ void ThinLTOCodeGenerator::run() {
   auto GUIDPreservedSymbols =
       computeGUIDPreservedSymbols(PreservedSymbols, TMBuilder.TheTriple);
 
+  // Add used symbol from inputs to the preserved symbols.
+  for (const auto &M : Modules)
+    addUsedSymbolToPreservedGUID(*M, GUIDPreservedSymbols);
+
   // Compute "dead" symbols, we don't want to import/export these!
   computeDeadSymbolsInIndex(*Index, GUIDPreservedSymbols);
 
@@ -913,7 +940,7 @@ void ThinLTOCodeGenerator::run() {
   // GVSummary and ResolvedODR maps to enable threaded access to these maps
   // below.
   for (auto &Module : Modules) {
-    auto ModuleIdentifier = Module.getBufferIdentifier();
+    auto ModuleIdentifier = Module->getName();
     ExportLists[ModuleIdentifier];
     ImportLists[ModuleIdentifier];
     ResolvedODR[ModuleIdentifier];
@@ -927,8 +954,10 @@ void ThinLTOCodeGenerator::run() {
   ModulesOrdering.resize(Modules.size());
   std::iota(ModulesOrdering.begin(), ModulesOrdering.end(), 0);
   llvm::sort(ModulesOrdering, [&](int LeftIndex, int RightIndex) {
-    auto LSize = Modules[LeftIndex].getBuffer().size();
-    auto RSize = Modules[RightIndex].getBuffer().size();
+    auto LSize =
+        Modules[LeftIndex]->getSingleBitcodeModule().getBuffer().size();
+    auto RSize =
+        Modules[RightIndex]->getSingleBitcodeModule().getBuffer().size();
     return LSize > RSize;
   });
 
@@ -936,9 +965,9 @@ void ThinLTOCodeGenerator::run() {
   {
     ThreadPool Pool(ThreadCount);
     for (auto IndexCount : ModulesOrdering) {
-      auto &ModuleBuffer = Modules[IndexCount];
+      auto &Mod = Modules[IndexCount];
       Pool.async([&](int count) {
-        auto ModuleIdentifier = ModuleBuffer.getBufferIdentifier();
+        auto ModuleIdentifier = Mod->getName();
         auto &ExportList = ExportLists[ModuleIdentifier];
 
         auto &DefinedGVSummaries = ModuleToDefinedGVSummaries[ModuleIdentifier];
@@ -982,9 +1011,8 @@ void ThinLTOCodeGenerator::run() {
         }
 
         // Parse module now
-        auto TheModule =
-            loadModuleFromBuffer(ModuleBuffer.getMemBuffer(), Context, false,
-                                 /*IsImporting*/ false);
+        auto TheModule = loadModuleFromInput(Mod.get(), Context, false,
+                                             /*IsImporting*/ false);
 
         // Save temps: original file.
         saveTempBitcode(*TheModule, SaveTempsDir, count, ".0.original.bc");
diff --git a/llvm/test/LTO/X86/Inputs/thinlto-internalize-used2.ll b/llvm/test/LTO/X86/Inputs/thinlto-internalize-used2.ll
new file mode 100644
index 00000000000..225685d931b
--- /dev/null
+++ b/llvm/test/LTO/X86/Inputs/thinlto-internalize-used2.ll
@@ -0,0 +1,10 @@
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.15.0"
+
+define i32 @main() {
+entry:
+  %call = call i32 @bar()
+  ret i32 0
+}
+
+declare i32 @bar()
diff --git a/llvm/test/LTO/X86/thinlto-internalize-used.ll b/llvm/test/LTO/X86/thinlto-internalize-used.ll
new file mode 100644
index 00000000000..0fc095056f0
--- /dev/null
+++ b/llvm/test/LTO/X86/thinlto-internalize-used.ll
@@ -0,0 +1,21 @@
+; RUN: opt -module-summary -o %t.bc %s
+; RUN: opt -module-summary -o %t-main.bc %S/Inputs/thinlto-internalize-used2.ll
+; RUN: llvm-lto -thinlto-action=thinlink %t.bc %t-main.bc -o %t-index.bc
+; RUN: llvm-lto -thinlto-action=promote -thinlto-index %t-index.bc %t.bc -o %t.promote.bc
+; RUN: llvm-dis %t.promote.bc -o - | FileCheck %s
+
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.15.0"
+
+@llvm.used = appending global [1 x i8*] [i8* bitcast (i32 ()* @foo to i8*)], section "llvm.metadata"
+
+; Make sure foo is not internalized.
+; CHECK: define i32 @foo()
+define i32 @foo() {
+  ret i32 0
+}
+
+define hidden i32 @bar() {
+  ret i32 0
+}
+
diff --git a/llvm/tools/llvm-lto/llvm-lto.cpp b/llvm/tools/llvm-lto/llvm-lto.cpp
index a71c3dd445c..57a867aa53e 100644
--- a/llvm/tools/llvm-lto/llvm-lto.cpp
+++ b/llvm/tools/llvm-lto/llvm-lto.cpp
@@ -449,22 +449,37 @@ std::unique_ptr<ModuleSummaryIndex> loadCombinedIndex() {
   return ExitOnErr(getModuleSummaryIndexForFile(ThinLTOIndex));
 }
 
-static std::unique_ptr<Module> loadModule(StringRef Filename,
-                                          LLVMContext &Ctx) {
-  SMDiagnostic Err;
-  std::unique_ptr<Module> M(parseIRFile(Filename, Err, Ctx));
-  if (!M) {
-    Err.print("llvm-lto", errs());
-    report_fatal_error("Can't load module for file " + Filename);
-  }
-  maybeVerifyModule(*M);
+static std::unique_ptr<MemoryBuffer> loadFile(StringRef Filename) {
+  ExitOnError ExitOnErr("llvm-lto: error loading file '" + Filename.str() +
+                        "': ");
+  return ExitOnErr(errorOrToExpected(MemoryBuffer::getFileOrSTDIN(Filename)));
+}
 
+static std::unique_ptr<lto::InputFile> loadInputFile(MemoryBufferRef Buffer) {
+  ExitOnError ExitOnErr("llvm-lto: error loading input '" +
+                        Buffer.getBufferIdentifier().str() + "': ");
+  return ExitOnErr(lto::InputFile::create(Buffer));
+}
+
+static std::unique_ptr<Module> loadModuleFromInput(lto::InputFile &File,
+                                                   LLVMContext &CTX) {
+  auto &Mod = File.getSingleBitcodeModule();
+  auto ModuleOrErr = Mod.parseModule(CTX);
+  if (!ModuleOrErr) {
+    handleAllErrors(ModuleOrErr.takeError(), [&](ErrorInfoBase &EIB) {
+      SMDiagnostic Err = SMDiagnostic(Mod.getModuleIdentifier(),
+                                      SourceMgr::DK_Error, EIB.message());
+      Err.print("llvm-lto", errs());
+    });
+    report_fatal_error("Can't load module, abort.");
+  }
+  maybeVerifyModule(**ModuleOrErr);
   if (ThinLTOModuleId.getNumOccurrences()) {
     if (InputFilenames.size() != 1)
       report_fatal_error("Can't override the module id for multiple files");
-    M->setModuleIdentifier(ThinLTOModuleId);
+    (*ModuleOrErr)->setModuleIdentifier(ThinLTOModuleId);
   }
-  return M;
+  return std::move(*ModuleOrErr);
 }
 
 static void writeModuleToFile(Module &TheModule, StringRef Filename) {
@@ -562,13 +577,15 @@ private:
     auto Index = loadCombinedIndex();
     for (auto &Filename : InputFilenames) {
       LLVMContext Ctx;
-      auto TheModule = loadModule(Filename, Ctx);
+      auto Buffer = loadFile(Filename);
+      auto Input = loadInputFile(Buffer->getMemBufferRef());
+      auto TheModule = loadModuleFromInput(*Input, Ctx);
 
       // Build a map of module to the GUIDs and summary objects that should
       // be written to its index.
       std::map<std::string, GVSummaryMapTy> ModuleToSummariesForIndex;
-      ThinGenerator.gatherImportedSummariesForModule(*TheModule, *Index,
-                                                     ModuleToSummariesForIndex);
+      ThinGenerator.gatherImportedSummariesForModule(
+          *TheModule, *Index, ModuleToSummariesForIndex, *Input);
 
       std::string OutputName = OutputFilename;
       if (OutputName.empty()) {
@@ -597,13 +614,16 @@ private:
     auto Index = loadCombinedIndex();
     for (auto &Filename : InputFilenames) {
       LLVMContext Ctx;
-      auto TheModule = loadModule(Filename, Ctx);
+      auto Buffer = loadFile(Filename);
+      auto Input = loadInputFile(Buffer->getMemBufferRef());
+      auto TheModule = loadModuleFromInput(*Input, Ctx);
       std::string OutputName = OutputFilename;
       if (OutputName.empty()) {
         OutputName = Filename + ".imports";
       }
-      OutputName = getThinLTOOutputFile(OutputName, OldPrefix, NewPrefix);
-      ThinGenerator.emitImports(*TheModule, OutputName, *Index);
+      OutputName =
+          getThinLTOOutputFile(OutputName, OldPrefix, NewPrefix);
+      ThinGenerator.emitImports(*TheModule, OutputName, *Index, *Input);
     }
   }
 
@@ -621,9 +641,11 @@ private:
     auto Index = loadCombinedIndex();
     for (auto &Filename : InputFilenames) {
       LLVMContext Ctx;
-      auto TheModule = loadModule(Filename, Ctx);
+      auto Buffer = loadFile(Filename);
+      auto Input = loadInputFile(Buffer->getMemBufferRef());
+      auto TheModule = loadModuleFromInput(*Input, Ctx);
 
-      ThinGenerator.promote(*TheModule, *Index);
+      ThinGenerator.promote(*TheModule, *Index, *Input);
 
       std::string OutputName = OutputFilename;
       if (OutputName.empty()) {
@@ -652,9 +674,11 @@ private:
 
     for (auto &Filename : InputFilenames) {
       LLVMContext Ctx;
-      auto TheModule = loadModule(Filename, Ctx);
+      auto Buffer = loadFile(Filename);
+      auto Input = loadInputFile(Buffer->getMemBufferRef());
+      auto TheModule = loadModuleFromInput(*Input, Ctx);
 
-      ThinGenerator.crossModuleImport(*TheModule, *Index);
+      ThinGenerator.crossModuleImport(*TheModule, *Index, *Input);
 
       std::string OutputName = OutputFilename;
       if (OutputName.empty()) {
@@ -683,9 +707,11 @@ private:
 
     for (auto &Filename : InputFilenames) {
       LLVMContext Ctx;
-      auto TheModule = loadModule(Filename, Ctx);
+      auto Buffer = loadFile(Filename);
+      auto Input = loadInputFile(Buffer->getMemBufferRef());
+      auto TheModule = loadModuleFromInput(*Input, Ctx);
 
-      ThinGenerator.internalize(*TheModule, *Index);
+      ThinGenerator.internalize(*TheModule, *Index, *Input);
 
       std::string OutputName = OutputFilename;
       if (OutputName.empty()) {
@@ -706,7 +732,9 @@ private:
 
     for (auto &Filename : InputFilenames) {
       LLVMContext Ctx;
-      auto TheModule = loadModule(Filename, Ctx);
+      auto Buffer = loadFile(Filename);
+      auto Input = loadInputFile(Buffer->getMemBufferRef());
+      auto TheModule = loadModuleFromInput(*Input, Ctx);
 
       ThinGenerator.optimize(*TheModule);