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