Remove "ExportingModule" from ThinLTO Index (NFC)

There is no real reason the index has to have the concept of an
exporting Module. We should be able to have one single unique
instance of the Index, and it should be read-only after creation
for the whole ThinLTO processing.
The linker plugin should be able to process multiple modules (in
parallel or in sequence) with the same index.

The only reason the ExportingModule was present seems to be to
implement hasExportedFunctions() that is used by the Module linker
to decide what to do with the current Module.
For now I replaced it with a query to the map of Modules path to
see if this module was declared in the Index and consider that if
it is the case then it is probably exporting function.
On the long term the Linker interface needs to evolve and this
call should not be needed anymore.

From: Mehdi Amini <mehdi.amini@apple.com>
llvm-svn: 254581

llvm/include/llvm/Bitcode/ReaderWriter.h

@@ -71,15 +71,13 @@ namespace llvm {
                           DiagnosticHandlerFunction DiagnosticHandler);
 
   /// Parse the specified bitcode buffer, returning the function info index.
-  /// If ExportingModule is true, check for functions in the index from this
-  /// module when the combined index is built during parsing and set flag.
   /// If IsLazy is true, parse the entire function summary into
   /// the index. Otherwise skip the function summary section, and only create
   /// an index object with a map from function name to function summary offset.
   /// The index is used to perform lazy function summary reading later.
   ErrorOr<std::unique_ptr<FunctionInfoIndex>> getFunctionInfoIndex(
       MemoryBufferRef Buffer, DiagnosticHandlerFunction DiagnosticHandler,
-      const Module *ExportingModule = nullptr, bool IsLazy = false);
+      bool IsLazy = false);
 
   /// This method supports lazy reading of function summary data from the
   /// combined index during function importing. When reading the combined index

llvm/include/llvm/IR/FunctionInfo.h

@@ -165,19 +165,8 @@ private:
   /// Holds strings for combined index, mapping to the corresponding module ID.
   ModulePathStringTableTy ModulePathStringTable;
 
-  /// The main module being compiled, that we are importing into, if applicable.
-  /// Used to check if any of its functions are in the index and therefore
-  /// potentially exported.
-  const Module *ExportingModule;
-
-  /// Flag indicating whether the exporting module has any functions in the
-  /// index and therefore potentially exported (imported into another module).
-  bool HasExportedFunctions;
-
 public:
-  FunctionInfoIndex(const Module *M = nullptr)
-      : ExportingModule(M), HasExportedFunctions(false){};
-  ~FunctionInfoIndex() = default;
+  FunctionInfoIndex() = default;
 
   // Disable the copy constructor and assignment operators, so
   // no unexpected copying/moving occurs.
@@ -201,14 +190,6 @@ public:
 
   /// Add a function info for a function of the given name.
   void addFunctionInfo(StringRef FuncName, std::unique_ptr<FunctionInfo> Info) {
-    // Update the HasExportedFunctions flag, but only if we had a function
-    // summary (i.e. we aren't parsing them lazily or have a bitcode file
-    // without a function summary section).
-    if (ExportingModule && Info->functionSummary()) {
-      if (ExportingModule->getModuleIdentifier() ==
-          Info->functionSummary()->modulePath())
-        HasExportedFunctions = true;
-    }
     FunctionMap[FuncName].push_back(std::move(Info));
   }
 
@@ -248,11 +229,10 @@ public:
   }
 
   /// Check if the given Module has any functions available for exporting
-  /// in the index.
-  bool hasExportedFunctions(const Module *M) const {
-    assert(M == ExportingModule &&
-           "Checking for exported functions on unexpected module");
-    return HasExportedFunctions;
+  /// in the index. We consider any module present in the ModulePathStringTable
+  /// to have exported functions.
+  bool hasExportedFunctions(const Module &M) const {
+    return ModulePathStringTable.count(M.getModuleIdentifier());
   }
 };
 

llvm/include/llvm/Object/FunctionIndexObjectFile.h

@@ -88,7 +88,7 @@ public:
   /// summary/index.
   static ErrorOr<std::unique_ptr<FunctionIndexObjectFile>>
   create(MemoryBufferRef Object, DiagnosticHandlerFunction DiagnosticHandler,
-         const Module *ExportingModule = nullptr, bool IsLazy = false);
+         bool IsLazy = false);
 
   /// \brief Parse the function summary information for function with the
   /// given name out of the given buffer. Parsed information is
@@ -104,8 +104,7 @@ public:
 /// index object if found, or nullptr if not.
 ErrorOr<std::unique_ptr<FunctionInfoIndex>>
 getFunctionIndexForFile(StringRef Path,
-                        DiagnosticHandlerFunction DiagnosticHandler,
-                        const Module *ExportingModule = nullptr);
+                        DiagnosticHandlerFunction DiagnosticHandler);
 }
 
 #endif

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

@@ -5991,12 +5991,11 @@ llvm::getBitcodeProducerString(MemoryBufferRef Buffer, LLVMContext &Context,
 ErrorOr<std::unique_ptr<FunctionInfoIndex>>
 llvm::getFunctionInfoIndex(MemoryBufferRef Buffer,
                            DiagnosticHandlerFunction DiagnosticHandler,
-                           const Module *ExportingModule, bool IsLazy) {
+                           bool IsLazy) {
   std::unique_ptr<MemoryBuffer> Buf = MemoryBuffer::getMemBuffer(Buffer, false);
   FunctionIndexBitcodeReader R(Buf.get(), DiagnosticHandler, IsLazy);
 
-  std::unique_ptr<FunctionInfoIndex> Index =
-      llvm::make_unique<FunctionInfoIndex>(ExportingModule);
+  auto Index = llvm::make_unique<FunctionInfoIndex>();
 
   auto cleanupOnError = [&](std::error_code EC) {
     R.releaseBuffer(); // Never take ownership on error.

llvm/lib/Linker/LinkModules.cpp

@@ -435,7 +435,7 @@ public:
     // backend compilation, and we need to see if it has functions that
     // may be exported to another backend compilation.
     if (ImportIndex && !ImportFunction)
-      HasExportedFunctions = ImportIndex->hasExportedFunctions(&SrcM);
+      HasExportedFunctions = ImportIndex->hasExportedFunctions(SrcM);
   }
 
   bool run();

llvm/lib/Object/FunctionIndexObjectFile.cpp

@@ -86,7 +86,7 @@ bool FunctionIndexObjectFile::hasFunctionSummaryInMemBuffer(
 ErrorOr<std::unique_ptr<FunctionIndexObjectFile>>
 FunctionIndexObjectFile::create(MemoryBufferRef Object,
                                 DiagnosticHandlerFunction DiagnosticHandler,
-                                const Module *ExportingModule, bool IsLazy) {
+                                bool IsLazy) {
   std::unique_ptr<FunctionInfoIndex> Index;
 
   ErrorOr<MemoryBufferRef> BCOrErr = findBitcodeInMemBuffer(Object);
@@ -94,7 +94,7 @@ FunctionIndexObjectFile::create(MemoryBufferRef Object,
     return BCOrErr.getError();
 
   ErrorOr<std::unique_ptr<FunctionInfoIndex>> IOrErr = getFunctionInfoIndex(
-      BCOrErr.get(), DiagnosticHandler, ExportingModule, IsLazy);
+      BCOrErr.get(), DiagnosticHandler, IsLazy);
 
   if (std::error_code EC = IOrErr.getError())
     return EC;
@@ -125,8 +125,7 @@ std::error_code FunctionIndexObjectFile::findFunctionSummaryInMemBuffer(
 // index object if found, or nullptr if not.
 ErrorOr<std::unique_ptr<FunctionInfoIndex>>
 llvm::getFunctionIndexForFile(StringRef Path,
-                              DiagnosticHandlerFunction DiagnosticHandler,
-                              const Module *ExportingModule) {
+                              DiagnosticHandlerFunction DiagnosticHandler) {
   ErrorOr<std::unique_ptr<MemoryBuffer>> FileOrErr =
       MemoryBuffer::getFileOrSTDIN(Path);
   std::error_code EC = FileOrErr.getError();
@@ -134,8 +133,7 @@ llvm::getFunctionIndexForFile(StringRef Path,
     return EC;
   MemoryBufferRef BufferRef = (FileOrErr.get())->getMemBufferRef();
   ErrorOr<std::unique_ptr<object::FunctionIndexObjectFile>> ObjOrErr =
-      object::FunctionIndexObjectFile::create(BufferRef, DiagnosticHandler,
-                                              ExportingModule);
+      object::FunctionIndexObjectFile::create(BufferRef, DiagnosticHandler);
   EC = ObjOrErr.getError();
   if (EC)
     return EC;

llvm/tools/llvm-link/llvm-link.cpp

@@ -229,7 +229,7 @@ static bool linkFiles(const char *argv0, LLVMContext &Context, Linker &L,
     std::unique_ptr<FunctionInfoIndex> Index;
     if (!FunctionIndex.empty()) {
       ErrorOr<std::unique_ptr<FunctionInfoIndex>> IndexOrErr =
-          llvm::getFunctionIndexForFile(FunctionIndex, diagnosticHandler, &*M);
+          llvm::getFunctionIndexForFile(FunctionIndex, diagnosticHandler);
       std::error_code EC = IndexOrErr.getError();
       if (EC) {
         errs() << EC.message() << '\n';