[NFC][ThinLTO] Change command line passing to EmbedBitcodeInModule

[mtrofin]

Summary

Changing to pass by ref - less null checks to worry about.

[tejohnson]

lgtm except for the part that should go back into D90278 as noted below.

llvm/include/llvm/Bitcode/BitcodeWriter.h

166

The change of the parameter name and comment here should go back in D90278

clang/lib/CodeGen/BackendUtil.cpp

case Backend_EmitBC:
     break;
   default:
     Conf.CGFileType = getCodeGenFileType(Action);
     break;
   }
   if (Error E =
           thinBackend(Conf, -1, AddStream, *M, *CombinedIndex, ImportList,
                       ModuleToDefinedGVSummaries[M->getModuleIdentifier()],
-                      ModuleMap, &CGOpts.CmdArgs)) {
+                      ModuleMap, CGOpts.CmdArgs)) {
     handleAllErrors(std::move(E), [&](ErrorInfoBase &EIB) {
       errs() << "Error running ThinLTO backend: " << EIB.message() << '\n';
     });
   }
 }
 
 void clang::EmitBackendOutput(DiagnosticsEngine &Diags,
                               const HeaderSearchOptions &HeaderOpts,

 // __LLVM,__bitcode section.
 void clang::EmbedBitcode(llvm::Module *M, const CodeGenOptions &CGOpts,
                          llvm::MemoryBufferRef Buf) {
   if (CGOpts.getEmbedBitcode() == CodeGenOptions::Embed_Off)
     return;
   llvm::EmbedBitcodeInModule(
       *M, Buf, CGOpts.getEmbedBitcode() != CodeGenOptions::Embed_Marker,
       CGOpts.getEmbedBitcode() != CodeGenOptions::Embed_Bitcode,
-      &CGOpts.CmdArgs);
+      CGOpts.CmdArgs);
 }

llvm/include/llvm/Bitcode/BitcodeWriter.h

class raw_ostream;
   /// where it will be written in a new bitcode block. This is used when
   /// writing the combined index file for ThinLTO. When writing a subset of the
   /// index for a distributed backend, provide the \p ModuleToSummariesForIndex
   /// map.
   void WriteIndexToFile(const ModuleSummaryIndex &Index, raw_ostream &Out,
                         const std::map<std::string, GVSummaryMapTy>
                             *ModuleToSummariesForIndex = nullptr);
 
-  /// Save a copy of the llvm IR as data in the __LLVM,__bitcode section.
+  /// If EmbedBitcode is set, save a copy of the llvm IR as data in the
+  ///  __LLVM,__bitcode section (.llvmbc on non-MacOS).
   /// If available, pass the serialized module via the Buf parameter. If not,
   /// pass an empty (default-initialized) MemoryBufferRef, and the serialization
   /// will be handled by this API. The same behavior happens if the provided Buf
   /// is not bitcode (i.e. if it's invalid data or even textual LLVM assembly).
+  /// If EmbedMarker is set, the command line is also exported in
+  /// the corresponding section (__LLVM,_cmdline / .llvmcmd) - even if CmdArgs
+  /// were empty.
   void EmbedBitcodeInModule(Module &M, MemoryBufferRef Buf, bool EmbedBitcode,
                             bool EmbedMarker,
-                            const std::vector<uint8_t> *CmdArgs);
+                            const std::vector<uint8_t> &CmdArgs);
 
 } // end namespace llvm
 
 #endif // LLVM_BITCODE_BITCODEWRITER_H

llvm/include/llvm/LTO/LTOBackend.h

Error backend(const Config &C, AddStreamFn AddStream,
               std::unique_ptr<Module> M, ModuleSummaryIndex &CombinedIndex);
 
 /// Runs a ThinLTO backend.
 Error thinBackend(const Config &C, unsigned Task, AddStreamFn AddStream,
                   Module &M, const ModuleSummaryIndex &CombinedIndex,
                   const FunctionImporter::ImportMapTy &ImportList,
                   const GVSummaryMapTy &DefinedGlobals,
                   MapVector<StringRef, BitcodeModule> &ModuleMap,
-                  const std::vector<uint8_t> *CmdArgs = nullptr);
+                  const std::vector<uint8_t> &CmdArgs = std::vector<uint8_t>());
 
 Error finalizeOptimizationRemarks(
     std::unique_ptr<ToolOutputFile> DiagOutputFile);
 
 /// Returns the BitcodeModule that is ThinLTO.
 BitcodeModule *findThinLTOModule(MutableArrayRef<BitcodeModule> BMs);
 
 /// Variant of the above.

llvm/lib/Bitcode/Writer/BitcodeWriter.cpp

case Triple::XCOFF:
     llvm_unreachable("XCOFF is not yet implemented");
     break;
   }
   llvm_unreachable("Unimplemented ObjectFormatType");
 }
 
 void llvm::EmbedBitcodeInModule(llvm::Module &M, llvm::MemoryBufferRef Buf,
                                 bool EmbedBitcode, bool EmbedMarker,
-                                const std::vector<uint8_t> *CmdArgs) {
+                                const std::vector<uint8_t> &CmdArgs) {
   // Save llvm.compiler.used and remove it.
   SmallVector<Constant *, 2> UsedArray;
   SmallPtrSet<GlobalValue *, 4> UsedGlobals;
   Type *UsedElementType = Type::getInt8Ty(M.getContext())->getPointerTo(0);
   GlobalVariable *Used = collectUsedGlobalVariables(M, UsedGlobals, true);
   for (auto *GV : UsedGlobals) {
     if (GV->getName() != "llvm.embedded.module" &&
         GV->getName() != "llvm.cmdline")
if (llvm::GlobalVariable *Old =
     Old->eraseFromParent();
   } else {
     GV->setName("llvm.embedded.module");
   }
 
   // Skip if only bitcode needs to be embedded.
   if (EmbedMarker) {
     // Embed command-line options.
-    ArrayRef<uint8_t> CmdData(const_cast<uint8_t *>(CmdArgs->data()),
-                              CmdArgs->size());
+    ArrayRef<uint8_t> CmdData(const_cast<uint8_t *>(CmdArgs.data()),
+                              CmdArgs.size());
     llvm::Constant *CmdConstant =
         llvm::ConstantDataArray::get(M.getContext(), CmdData);
     GV = new llvm::GlobalVariable(M, CmdConstant->getType(), true,
                                   llvm::GlobalValue::PrivateLinkage,
                                   CmdConstant);
     GV->setSection(getSectionNameForCommandline(T));
     GV->setAlignment(Align(1));
     UsedArray.push_back(

llvm/lib/LTO/LTOBackend.cpp

static void runOldPMPasses(const Config &Conf, Module &Mod, TargetMachine *TM,
   else
     PMB.populateLTOPassManager(passes);
   passes.run(Mod);
 }
 
 bool opt(const Config &Conf, TargetMachine *TM, unsigned Task, Module &Mod,
          bool IsThinLTO, ModuleSummaryIndex *ExportSummary,
          const ModuleSummaryIndex *ImportSummary,
-         const std::vector<uint8_t> *CmdArgs = nullptr) {
+         const std::vector<uint8_t> &CmdArgs) {
   if (EmbedBitcode == LTOBitcodeEmbedding::EmbedPostMergePreOptimized) {
     // FIXME: the motivation for capturing post-merge bitcode and command line
     // is replicating the compilation environment from bitcode, without needing
     // to understand the dependencies (the functions to be imported). This
     // assumes a clang - based invocation, case in which we have the command
     // line.
     // It's not very clear how the above motivation would map in the
     // linker-based case, so we currently don't plumb the command line args in
     // that case.
-    if (CmdArgs == nullptr)
+    if (CmdArgs.empty())
       LLVM_DEBUG(
           dbgs() << "Post-(Thin)LTO merge bitcode embedding was requested, but "
                     "command line arguments are not available");
     llvm::EmbedBitcodeInModule(Mod, llvm::MemoryBufferRef(),
                                /*EmbedBitcode*/ true,
-                               /*EmbedMarker*/ false, CmdArgs);
+                               /*EmbedMarker*/ false,
+                               /*Cmdline*/ CmdArgs);
   }
   // FIXME: Plumb the combined index into the new pass manager.
   if (!Conf.OptPipeline.empty())
     runNewPMCustomPasses(Conf, Mod, TM, Conf.OptPipeline, Conf.AAPipeline,
                          Conf.DisableVerify);
   else if (Conf.UseNewPM)
     runNewPMPasses(Conf, Mod, TM, Conf.OptLevel, IsThinLTO, ExportSummary,
                    ImportSummary);
   else
     runOldPMPasses(Conf, Mod, TM, IsThinLTO, ExportSummary, ImportSummary);
   return !Conf.PostOptModuleHook || Conf.PostOptModuleHook(Task, Mod);
 }
 
 void codegen(const Config &Conf, TargetMachine *TM, AddStreamFn AddStream,
              unsigned Task, Module &Mod,
              const ModuleSummaryIndex &CombinedIndex) {
   if (Conf.PreCodeGenModuleHook && !Conf.PreCodeGenModuleHook(Task, Mod))
     return;
 
   if (EmbedBitcode == LTOBitcodeEmbedding::EmbedOptimized)
     llvm::EmbedBitcodeInModule(Mod, llvm::MemoryBufferRef(),
                                /*EmbedBitcode*/ true,
-                               /*EmbedMarker*/ false, /*CmdArgs*/ nullptr);
+                               /*EmbedMarker*/ false,
+                               /*CmdArgs*/ std::vector<uint8_t>());
 
   std::unique_ptr<ToolOutputFile> DwoOut;
   SmallString<1024> DwoFile(Conf.SplitDwarfOutput);
   if (!Conf.DwoDir.empty()) {
     std::error_code EC;
     if (auto EC = llvm::sys::fs::create_directories(Conf.DwoDir))
       report_fatal_error("Failed to create directory " + Conf.DwoDir + ": " +
                          EC.message());
Error lto::backend(const Config &C, AddStreamFn AddStream,
   Expected<const Target *> TOrErr = initAndLookupTarget(C, *Mod);
   if (!TOrErr)
     return TOrErr.takeError();
 
   std::unique_ptr<TargetMachine> TM = createTargetMachine(C, *TOrErr, *Mod);
 
   if (!C.CodeGenOnly) {
     if (!opt(C, TM.get(), 0, *Mod, /*IsThinLTO=*/false,
-             /*ExportSummary=*/&CombinedIndex, /*ImportSummary=*/nullptr))
+             /*ExportSummary=*/&CombinedIndex, /*ImportSummary=*/nullptr,
+             /*CmdArgs*/ std::vector<uint8_t>()))
       return Error::success();
   }
 
   if (ParallelCodeGenParallelismLevel == 1) {
     codegen(C, TM.get(), AddStream, 0, *Mod, CombinedIndex);
   } else {
     splitCodeGen(C, TM.get(), AddStream, ParallelCodeGenParallelismLevel,
                  std::move(Mod), CombinedIndex);
static void dropDeadSymbols(Module &Mod, const GVSummaryMapTy &DefinedGlobals,
   }
 }
 
 Error lto::thinBackend(const Config &Conf, unsigned Task, AddStreamFn AddStream,
                        Module &Mod, const ModuleSummaryIndex &CombinedIndex,
                        const FunctionImporter::ImportMapTy &ImportList,
                        const GVSummaryMapTy &DefinedGlobals,
                        MapVector<StringRef, BitcodeModule> &ModuleMap,
-                       const std::vector<uint8_t> *CmdArgs) {
+                       const std::vector<uint8_t> &CmdArgs) {
   Expected<const Target *> TOrErr = initAndLookupTarget(Conf, Mod);
   if (!TOrErr)
     return TOrErr.takeError();
 
   std::unique_ptr<TargetMachine> TM = createTargetMachine(Conf, *TOrErr, Mod);
 
   // Setup optimization remarks.
   auto DiagFileOrErr = lto::setupLLVMOptimizationRemarks(
if (!BMOrErr) {
       });
       return false;
     }
     ModuleMap.insert({I.first(), *BMOrErr});
     OwnedImportsLifetimeManager.push_back(std::move(*MBOrErr));
   }
   return true;
 }
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