clang/lib/CodeGen/ObjectFilePCHContainerWriter.cpp

   1 //===--- ObjectFilePCHContainerWriter.cpp -----------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #include "clang/CodeGen/ObjectFilePCHContainerWriter.h"
  10 #include "CGDebugInfo.h"
  11 #include "CodeGenModule.h"
  12 #include "clang/AST/ASTContext.h"
  13 #include "clang/AST/DeclObjC.h"
  14 #include "clang/AST/Expr.h"
  15 #include "clang/AST/RecursiveASTVisitor.h"
  16 #include "clang/Basic/CodeGenOptions.h"
  17 #include "clang/Basic/Diagnostic.h"
  18 #include "clang/Basic/TargetInfo.h"
  19 #include "clang/CodeGen/BackendUtil.h"
  20 #include "clang/Frontend/CompilerInstance.h"
  21 #include "clang/Lex/HeaderSearch.h"
  22 #include "clang/Lex/Preprocessor.h"
  23 #include "llvm/ADT/StringRef.h"
  24 #include "llvm/Bitstream/BitstreamReader.h"
  25 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
  26 #include "llvm/IR/Constants.h"
  27 #include "llvm/IR/DataLayout.h"
  28 #include "llvm/IR/LLVMContext.h"
  29 #include "llvm/IR/Module.h"
  30 #include "llvm/MC/TargetRegistry.h"
  31 #include "llvm/Object/COFF.h"
  32 #include "llvm/Object/ObjectFile.h"
  33 #include "llvm/Support/Path.h"
  34 #include <memory>
  35 #include <utility>
  36
  37 using namespace clang;
  38
  39 #define DEBUG_TYPE "pchcontainer"
  40
  41 namespace {
  42 class PCHContainerGenerator : public ASTConsumer {
  43   DiagnosticsEngine &Diags;
  44   const std::string MainFileName;
  45   const std::string OutputFileName;
  46   ASTContext *Ctx;
  47   ModuleMap &MMap;
  48   IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS;
  49   const HeaderSearchOptions &HeaderSearchOpts;
  50   const PreprocessorOptions &PreprocessorOpts;
  51   CodeGenOptions CodeGenOpts;
  52   const TargetOptions TargetOpts;
  53   LangOptions LangOpts;
  54   std::unique_ptr<llvm::LLVMContext> VMContext;
  55   std::unique_ptr<llvm::Module> M;
  56   std::unique_ptr<CodeGen::CodeGenModule> Builder;
  57   std::unique_ptr<raw_pwrite_stream> OS;
  58   std::shared_ptr<PCHBuffer> Buffer;
  59
  60   /// Visit every type and emit debug info for it.
  61   struct DebugTypeVisitor : public RecursiveASTVisitor<DebugTypeVisitor> {
  62     clang::CodeGen::CGDebugInfo &DI;
  63     ASTContext &Ctx;
  64     DebugTypeVisitor(clang::CodeGen::CGDebugInfo &DI, ASTContext &Ctx)
  65         : DI(DI), Ctx(Ctx) {}
  66
  67     /// Determine whether this type can be represented in DWARF.
  68     static bool CanRepresent(const Type *Ty) {
  69       return !Ty->isDependentType() && !Ty->isUndeducedType();
  70     }
  71
  72     bool VisitImportDecl(ImportDecl *D) {
  73       if (!D->getImportedOwningModule())
  74         DI.EmitImportDecl(*D);
  75       return true;
  76     }
  77
  78     bool VisitTypeDecl(TypeDecl *D) {
  79       // TagDecls may be deferred until after all decls have been merged and we
  80       // know the complete type. Pure forward declarations will be skipped, but
  81       // they don't need to be emitted into the module anyway.
  82       if (auto *TD = dyn_cast<TagDecl>(D))
  83         if (!TD->isCompleteDefinition())
  84           return true;
  85
  86       QualType QualTy = Ctx.getTypeDeclType(D);
  87       if (!QualTy.isNull() && CanRepresent(QualTy.getTypePtr()))
  88         DI.getOrCreateStandaloneType(QualTy, D->getLocation());
  89       return true;
  90     }
  91
  92     bool VisitObjCInterfaceDecl(ObjCInterfaceDecl *D) {
  93       QualType QualTy(D->getTypeForDecl(), 0);
  94       if (!QualTy.isNull() && CanRepresent(QualTy.getTypePtr()))
  95         DI.getOrCreateStandaloneType(QualTy, D->getLocation());
  96       return true;
  97     }
  98
  99     bool VisitFunctionDecl(FunctionDecl *D) {
 100       // Skip deduction guides.
 101       if (isa<CXXDeductionGuideDecl>(D))
 102         return true;
 103
 104       if (isa<CXXMethodDecl>(D))
 105         // This is not yet supported. Constructing the `this' argument
 106         // mandates a CodeGenFunction.
 107         return true;
 108
 109       SmallVector<QualType, 16> ArgTypes;
 110       for (auto *i : D->parameters())
 111         ArgTypes.push_back(i->getType());
 112       QualType RetTy = D->getReturnType();
 113       QualType FnTy = Ctx.getFunctionType(RetTy, ArgTypes,
 114                                           FunctionProtoType::ExtProtoInfo());
 115       if (CanRepresent(FnTy.getTypePtr()))
 116         DI.EmitFunctionDecl(D, D->getLocation(), FnTy);
 117       return true;
 118     }
 119
 120     bool VisitObjCMethodDecl(ObjCMethodDecl *D) {
 121       if (!D->getClassInterface())
 122         return true;
 123
 124       bool selfIsPseudoStrong, selfIsConsumed;
 125       SmallVector<QualType, 16> ArgTypes;
 126       ArgTypes.push_back(D->getSelfType(Ctx, D->getClassInterface(),
 127                                         selfIsPseudoStrong, selfIsConsumed));
 128       ArgTypes.push_back(Ctx.getObjCSelType());
 129       for (auto *i : D->parameters())
 130         ArgTypes.push_back(i->getType());
 131       QualType RetTy = D->getReturnType();
 132       QualType FnTy = Ctx.getFunctionType(RetTy, ArgTypes,
 133                                           FunctionProtoType::ExtProtoInfo());
 134       if (CanRepresent(FnTy.getTypePtr()))
 135         DI.EmitFunctionDecl(D, D->getLocation(), FnTy);
 136       return true;
 137     }
 138   };
 139
 140 public:
 141   PCHContainerGenerator(CompilerInstance &CI, const std::string &MainFileName,
 142                         const std::string &OutputFileName,
 143                         std::unique_ptr<raw_pwrite_stream> OS,
 144                         std::shared_ptr<PCHBuffer> Buffer)
 145       : Diags(CI.getDiagnostics()), MainFileName(MainFileName),
 146         OutputFileName(OutputFileName), Ctx(nullptr),
 147         MMap(CI.getPreprocessor().getHeaderSearchInfo().getModuleMap()),
 148         FS(&CI.getVirtualFileSystem()),
 149         HeaderSearchOpts(CI.getHeaderSearchOpts()),
 150         PreprocessorOpts(CI.getPreprocessorOpts()),
 151         TargetOpts(CI.getTargetOpts()), LangOpts(CI.getLangOpts()),
 152         OS(std::move(OS)), Buffer(std::move(Buffer)) {
 153     // The debug info output isn't affected by CodeModel and
 154     // ThreadModel, but the backend expects them to be nonempty.
 155     CodeGenOpts.CodeModel = "default";
 156     LangOpts.setThreadModel(LangOptions::ThreadModelKind::Single);
 157     CodeGenOpts.DebugTypeExtRefs = true;
 158     // When building a module MainFileName is the name of the modulemap file.
 159     CodeGenOpts.MainFileName =
 160         LangOpts.CurrentModule.empty() ? MainFileName : LangOpts.CurrentModule;
 161     CodeGenOpts.setDebugInfo(llvm::codegenoptions::FullDebugInfo);
 162     CodeGenOpts.setDebuggerTuning(CI.getCodeGenOpts().getDebuggerTuning());
 163     CodeGenOpts.DwarfVersion = CI.getCodeGenOpts().DwarfVersion;
 164     CodeGenOpts.DebugCompilationDir =
 165         CI.getInvocation().getCodeGenOpts().DebugCompilationDir;
 166     CodeGenOpts.DebugPrefixMap =
 167         CI.getInvocation().getCodeGenOpts().DebugPrefixMap;
 168     CodeGenOpts.DebugStrictDwarf = CI.getCodeGenOpts().DebugStrictDwarf;
 169   }
 170
 171   ~PCHContainerGenerator() override = default;
 172
 173   void Initialize(ASTContext &Context) override {
 174     assert(!Ctx && "initialized multiple times");
 175
 176     Ctx = &Context;
 177     VMContext.reset(new llvm::LLVMContext());
 178     M.reset(new llvm::Module(MainFileName, *VMContext));
 179     M->setDataLayout(Ctx->getTargetInfo().getDataLayoutString());
 180     Builder.reset(new CodeGen::CodeGenModule(
 181         *Ctx, FS, HeaderSearchOpts, PreprocessorOpts, CodeGenOpts, *M, Diags));
 182
 183     // Prepare CGDebugInfo to emit debug info for a clang module.
 184     auto *DI = Builder->getModuleDebugInfo();
 185     StringRef ModuleName = llvm::sys::path::filename(MainFileName);
 186     DI->setPCHDescriptor(
 187         {ModuleName, "", OutputFileName, ASTFileSignature::createDISentinel()});
 188     DI->setModuleMap(MMap);
 189   }
 190
 191   bool HandleTopLevelDecl(DeclGroupRef D) override {
 192     if (Diags.hasErrorOccurred())
 193       return true;
 194
 195     // Collect debug info for all decls in this group.
 196     for (auto *I : D)
 197       if (!I->isFromASTFile()) {
 198         DebugTypeVisitor DTV(*Builder->getModuleDebugInfo(), *Ctx);
 199         DTV.TraverseDecl(I);
 200       }
 201     return true;
 202   }
 203
 204   void HandleTopLevelDeclInObjCContainer(DeclGroupRef D) override {
 205     HandleTopLevelDecl(D);
 206   }
 207
 208   void HandleTagDeclDefinition(TagDecl *D) override {
 209     if (Diags.hasErrorOccurred())
 210       return;
 211
 212     if (D->isFromASTFile())
 213       return;
 214
 215     // Anonymous tag decls are deferred until we are building their declcontext.
 216     if (D->getName().empty())
 217       return;
 218
 219     // Defer tag decls until their declcontext is complete.
 220     auto *DeclCtx = D->getDeclContext();
 221     while (DeclCtx) {
 222       if (auto *D = dyn_cast<TagDecl>(DeclCtx))
 223         if (!D->isCompleteDefinition())
 224           return;
 225       DeclCtx = DeclCtx->getParent();
 226     }
 227
 228     DebugTypeVisitor DTV(*Builder->getModuleDebugInfo(), *Ctx);
 229     DTV.TraverseDecl(D);
 230     Builder->UpdateCompletedType(D);
 231   }
 232
 233   void HandleTagDeclRequiredDefinition(const TagDecl *D) override {
 234     if (Diags.hasErrorOccurred())
 235       return;
 236
 237     if (const RecordDecl *RD = dyn_cast<RecordDecl>(D))
 238       Builder->getModuleDebugInfo()->completeRequiredType(RD);
 239   }
 240
 241   void HandleImplicitImportDecl(ImportDecl *D) override {
 242     if (!D->getImportedOwningModule())
 243       Builder->getModuleDebugInfo()->EmitImportDecl(*D);
 244   }
 245
 246   /// Emit a container holding the serialized AST.
 247   void HandleTranslationUnit(ASTContext &Ctx) override {
 248     assert(M && VMContext && Builder);
 249     // Delete these on function exit.
 250     std::unique_ptr<llvm::LLVMContext> VMContext = std::move(this->VMContext);
 251     std::unique_ptr<llvm::Module> M = std::move(this->M);
 252     std::unique_ptr<CodeGen::CodeGenModule> Builder = std::move(this->Builder);
 253
 254     if (Diags.hasErrorOccurred())
 255       return;
 256
 257     M->setTargetTriple(Ctx.getTargetInfo().getTriple().getTriple());
 258     M->setDataLayout(Ctx.getTargetInfo().getDataLayoutString());
 259
 260     // PCH files don't have a signature field in the control block,
 261     // but LLVM detects DWO CUs by looking for a non-zero DWO id.
 262     // We use the lower 64 bits for debug info.
 263
 264     uint64_t Signature =
 265         Buffer->Signature ? Buffer->Signature.truncatedValue() : ~1ULL;
 266
 267     Builder->getModuleDebugInfo()->setDwoId(Signature);
 268
 269     // Finalize the Builder.
 270     if (Builder)
 271       Builder->Release();
 272
 273     // Ensure the target exists.
 274     std::string Error;
 275     auto Triple = Ctx.getTargetInfo().getTriple();
 276     if (!llvm::TargetRegistry::lookupTarget(Triple.getTriple(), Error))
 277       llvm::report_fatal_error(llvm::Twine(Error));
 278
 279     // Emit the serialized Clang AST into its own section.
 280     assert(Buffer->IsComplete && "serialization did not complete");
 281     auto &SerializedAST = Buffer->Data;
 282     auto Size = SerializedAST.size();
 283
 284     if (Triple.isOSBinFormatWasm()) {
 285       // Emit __clangast in custom section instead of named data segment
 286       // to find it while iterating sections.
 287       // This could be avoided if all data segements (the wasm sense) were
 288       // represented as their own sections (in the llvm sense).
 289       // TODO: https://github.com/WebAssembly/tool-conventions/issues/138
 290       llvm::NamedMDNode *MD =
 291           M->getOrInsertNamedMetadata("wasm.custom_sections");
 292       llvm::Metadata *Ops[2] = {
 293           llvm::MDString::get(*VMContext, "__clangast"),
 294           llvm::MDString::get(*VMContext,
 295                               StringRef(SerializedAST.data(), Size))};
 296       auto *NameAndContent = llvm::MDTuple::get(*VMContext, Ops);
 297       MD->addOperand(NameAndContent);
 298     } else {
 299       auto Int8Ty = llvm::Type::getInt8Ty(*VMContext);
 300       auto *Ty = llvm::ArrayType::get(Int8Ty, Size);
 301       auto *Data = llvm::ConstantDataArray::getString(
 302           *VMContext, StringRef(SerializedAST.data(), Size),
 303           /*AddNull=*/false);
 304       auto *ASTSym = new llvm::GlobalVariable(
 305           *M, Ty, /*constant*/ true, llvm::GlobalVariable::InternalLinkage,
 306           Data, "__clang_ast");
 307       // The on-disk hashtable needs to be aligned.
 308       ASTSym->setAlignment(llvm::Align(8));
 309
 310       // Mach-O also needs a segment name.
 311       if (Triple.isOSBinFormatMachO())
 312         ASTSym->setSection("__CLANG,__clangast");
 313       // COFF has an eight character length limit.
 314       else if (Triple.isOSBinFormatCOFF())
 315         ASTSym->setSection("clangast");
 316       else
 317         ASTSym->setSection("__clangast");
 318     }
 319
 320     LLVM_DEBUG({
 321       // Print the IR for the PCH container to the debug output.
 322       llvm::SmallString<0> Buffer;
 323       clang::EmitBackendOutput(
 324           Diags, HeaderSearchOpts, CodeGenOpts, TargetOpts, LangOpts,
 325           Ctx.getTargetInfo().getDataLayoutString(), M.get(),
 326           BackendAction::Backend_EmitLL, FS,
 327           std::make_unique<llvm::raw_svector_ostream>(Buffer));
 328       llvm::dbgs() << Buffer;
 329     });
 330
 331     // Use the LLVM backend to emit the pch container.
 332     clang::EmitBackendOutput(Diags, HeaderSearchOpts, CodeGenOpts, TargetOpts,
 333                              LangOpts,
 334                              Ctx.getTargetInfo().getDataLayoutString(), M.get(),
 335                              BackendAction::Backend_EmitObj, FS, std::move(OS));
 336
 337     // Free the memory for the temporary buffer.
 338     llvm::SmallVector<char, 0> Empty;
 339     SerializedAST = std::move(Empty);
 340   }
 341 };
 342
 343 } // anonymous namespace
 344
 345 std::unique_ptr<ASTConsumer>
 346 ObjectFilePCHContainerWriter::CreatePCHContainerGenerator(
 347     CompilerInstance &CI, const std::string &MainFileName,
 348     const std::string &OutputFileName,
 349     std::unique_ptr<llvm::raw_pwrite_stream> OS,
 350     std::shared_ptr<PCHBuffer> Buffer) const {
 351   return std::make_unique<PCHContainerGenerator>(
 352       CI, MainFileName, OutputFileName, std::move(OS), Buffer);
 353 }