1//===--- ObjectFilePCHContainerOperations.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/ObjectFilePCHContainerOperations.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/Object/COFF.h"
31#include "llvm/Object/ObjectFile.h"
32#include "llvm/Support/Path.h"
33#include "llvm/Support/TargetRegistry.h"
34#include <memory>
35#include <utility>
36
37using namespace clang;
38
39#define DEBUG_TYPE "pchcontainer"
40
41namespace {
42class PCHContainerGenerator : public ASTConsumer {
43  DiagnosticsEngine &Diags;
44  const std::string MainFileName;
45  const std::string OutputFileName;
46  ASTContext *Ctx;
47  ModuleMap &MMap;
48  const HeaderSearchOptions &HeaderSearchOpts;
49  const PreprocessorOptions &PreprocessorOpts;
50  CodeGenOptions CodeGenOpts;
51  const TargetOptions TargetOpts;
52  const LangOptions LangOpts;
53  std::unique_ptr<llvm::LLVMContext> VMContext;
54  std::unique_ptr<llvm::Module> M;
55  std::unique_ptr<CodeGen::CodeGenModule> Builder;
56  std::unique_ptr<raw_pwrite_stream> OS;
57  std::shared_ptr<PCHBuffer> Buffer;
58
59  /// Visit every type and emit debug info for it.
60  struct DebugTypeVisitor : public RecursiveASTVisitor<DebugTypeVisitor> {
61    clang::CodeGen::CGDebugInfo &DI;
62    ASTContext &Ctx;
63    DebugTypeVisitor(clang::CodeGen::CGDebugInfo &DI, ASTContext &Ctx)
64        : DI(DI), Ctx(Ctx) {}
65
66    /// Determine whether this type can be represented in DWARF.
67    static bool CanRepresent(const Type *Ty) {
68      return !Ty->isDependentType() && !Ty->isUndeducedType();
69    }
70
71    bool VisitImportDecl(ImportDecl *D) {
72      if (!D->getImportedOwningModule())
73        DI.EmitImportDecl(*D);
74      return true;
75    }
76
77    bool VisitTypeDecl(TypeDecl *D) {
78      // TagDecls may be deferred until after all decls have been merged and we
79      // know the complete type. Pure forward declarations will be skipped, but
80      // they don't need to be emitted into the module anyway.
81      if (auto *TD = dyn_cast<TagDecl>(D))
82        if (!TD->isCompleteDefinition())
83          return true;
84
85      QualType QualTy = Ctx.getTypeDeclType(D);
86      if (!QualTy.isNull() && CanRepresent(QualTy.getTypePtr()))
87        DI.getOrCreateStandaloneType(QualTy, D->getLocation());
88      return true;
89    }
90
91    bool VisitObjCInterfaceDecl(ObjCInterfaceDecl *D) {
92      QualType QualTy(D->getTypeForDecl(), 0);
93      if (!QualTy.isNull() && CanRepresent(QualTy.getTypePtr()))
94        DI.getOrCreateStandaloneType(QualTy, D->getLocation());
95      return true;
96    }
97
98    bool VisitFunctionDecl(FunctionDecl *D) {
99      if (isa<CXXMethodDecl>(D))
100        // This is not yet supported. Constructing the `this' argument
101        // mandates a CodeGenFunction.
102        return true;
103
104      SmallVector<QualType, 16> ArgTypes;
105      for (auto i : D->parameters())
106        ArgTypes.push_back(i->getType());
107      QualType RetTy = D->getReturnType();
108      QualType FnTy = Ctx.getFunctionType(RetTy, ArgTypes,
109                                          FunctionProtoType::ExtProtoInfo());
110      if (CanRepresent(FnTy.getTypePtr()))
111        DI.EmitFunctionDecl(D, D->getLocation(), FnTy);
112      return true;
113    }
114
115    bool VisitObjCMethodDecl(ObjCMethodDecl *D) {
116      if (!D->getClassInterface())
117        return true;
118
119      bool selfIsPseudoStrong, selfIsConsumed;
120      SmallVector<QualType, 16> ArgTypes;
121      ArgTypes.push_back(D->getSelfType(Ctx, D->getClassInterface(),
122                                        selfIsPseudoStrong, selfIsConsumed));
123      ArgTypes.push_back(Ctx.getObjCSelType());
124      for (auto i : D->parameters())
125        ArgTypes.push_back(i->getType());
126      QualType RetTy = D->getReturnType();
127      QualType FnTy = Ctx.getFunctionType(RetTy, ArgTypes,
128                                          FunctionProtoType::ExtProtoInfo());
129      if (CanRepresent(FnTy.getTypePtr()))
130        DI.EmitFunctionDecl(D, D->getLocation(), FnTy);
131      return true;
132    }
133  };
134
135public:
136  PCHContainerGenerator(CompilerInstance &CI, const std::string &MainFileName,
137                        const std::string &OutputFileName,
138                        std::unique_ptr<raw_pwrite_stream> OS,
139                        std::shared_ptr<PCHBuffer> Buffer)
140      : Diags(CI.getDiagnostics()), MainFileName(MainFileName),
141        OutputFileName(OutputFileName), Ctx(nullptr),
142        MMap(CI.getPreprocessor().getHeaderSearchInfo().getModuleMap()),
143        HeaderSearchOpts(CI.getHeaderSearchOpts()),
144        PreprocessorOpts(CI.getPreprocessorOpts()),
145        TargetOpts(CI.getTargetOpts()), LangOpts(CI.getLangOpts()),
146        OS(std::move(OS)), Buffer(std::move(Buffer)) {
147    // The debug info output isn't affected by CodeModel and
148    // ThreadModel, but the backend expects them to be nonempty.
149    CodeGenOpts.CodeModel = "default";
150    CodeGenOpts.ThreadModel = "single";
151    CodeGenOpts.DebugTypeExtRefs = true;
152    // When building a module MainFileName is the name of the modulemap file.
153    CodeGenOpts.MainFileName =
154        LangOpts.CurrentModule.empty() ? MainFileName : LangOpts.CurrentModule;
155    CodeGenOpts.setDebugInfo(codegenoptions::FullDebugInfo);
156    CodeGenOpts.setDebuggerTuning(CI.getCodeGenOpts().getDebuggerTuning());
157    CodeGenOpts.DebugPrefixMap =
158        CI.getInvocation().getCodeGenOpts().DebugPrefixMap;
159  }
160
161  ~PCHContainerGenerator() override = default;
162
163  void Initialize(ASTContext &Context) override {
164    assert(!Ctx && "initialized multiple times");
165
166    Ctx = &Context;
167    VMContext.reset(new llvm::LLVMContext());
168    M.reset(new llvm::Module(MainFileName, *VMContext));
169    M->setDataLayout(Ctx->getTargetInfo().getDataLayout());
170    Builder.reset(new CodeGen::CodeGenModule(
171        *Ctx, HeaderSearchOpts, PreprocessorOpts, CodeGenOpts, *M, Diags));
172
173    // Prepare CGDebugInfo to emit debug info for a clang module.
174    auto *DI = Builder->getModuleDebugInfo();
175    StringRef ModuleName = llvm::sys::path::filename(MainFileName);
176    DI->setPCHDescriptor({ModuleName, "", OutputFileName,
177                          ASTFileSignature{{{~0U, ~0U, ~0U, ~0U, ~1U}}}});
178    DI->setModuleMap(MMap);
179  }
180
181  bool HandleTopLevelDecl(DeclGroupRef D) override {
182    if (Diags.hasErrorOccurred())
183      return true;
184
185    // Collect debug info for all decls in this group.
186    for (auto *I : D)
187      if (!I->isFromASTFile()) {
188        DebugTypeVisitor DTV(*Builder->getModuleDebugInfo(), *Ctx);
189        DTV.TraverseDecl(I);
190      }
191    return true;
192  }
193
194  void HandleTopLevelDeclInObjCContainer(DeclGroupRef D) override {
195    HandleTopLevelDecl(D);
196  }
197
198  void HandleTagDeclDefinition(TagDecl *D) override {
199    if (Diags.hasErrorOccurred())
200      return;
201
202    if (D->isFromASTFile())
203      return;
204
205    // Anonymous tag decls are deferred until we are building their declcontext.
206    if (D->getName().empty())
207      return;
208
209    // Defer tag decls until their declcontext is complete.
210    auto *DeclCtx = D->getDeclContext();
211    while (DeclCtx) {
212      if (auto *D = dyn_cast<TagDecl>(DeclCtx))
213        if (!D->isCompleteDefinition())
214          return;
215      DeclCtx = DeclCtx->getParent();
216    }
217
218    DebugTypeVisitor DTV(*Builder->getModuleDebugInfo(), *Ctx);
219    DTV.TraverseDecl(D);
220    Builder->UpdateCompletedType(D);
221  }
222
223  void HandleTagDeclRequiredDefinition(const TagDecl *D) override {
224    if (Diags.hasErrorOccurred())
225      return;
226
227    if (const RecordDecl *RD = dyn_cast<RecordDecl>(D))
228      Builder->getModuleDebugInfo()->completeRequiredType(RD);
229  }
230
231  void HandleImplicitImportDecl(ImportDecl *D) override {
232    if (!D->getImportedOwningModule())
233      Builder->getModuleDebugInfo()->EmitImportDecl(*D);
234  }
235
236  /// Emit a container holding the serialized AST.
237  void HandleTranslationUnit(ASTContext &Ctx) override {
238    assert(M && VMContext && Builder);
239    // Delete these on function exit.
240    std::unique_ptr<llvm::LLVMContext> VMContext = std::move(this->VMContext);
241    std::unique_ptr<llvm::Module> M = std::move(this->M);
242    std::unique_ptr<CodeGen::CodeGenModule> Builder = std::move(this->Builder);
243
244    if (Diags.hasErrorOccurred())
245      return;
246
247    M->setTargetTriple(Ctx.getTargetInfo().getTriple().getTriple());
248    M->setDataLayout(Ctx.getTargetInfo().getDataLayout());
249
250    // PCH files don't have a signature field in the control block,
251    // but LLVM detects DWO CUs by looking for a non-zero DWO id.
252    // We use the lower 64 bits for debug info.
253    uint64_t Signature =
254        Buffer->Signature
255            ? (uint64_t)Buffer->Signature[1] << 32 | Buffer->Signature[0]
256            : ~1ULL;
257    Builder->getModuleDebugInfo()->setDwoId(Signature);
258
259    // Finalize the Builder.
260    if (Builder)
261      Builder->Release();
262
263    // Ensure the target exists.
264    std::string Error;
265    auto Triple = Ctx.getTargetInfo().getTriple();
266    if (!llvm::TargetRegistry::lookupTarget(Triple.getTriple(), Error))
267      llvm::report_fatal_error(Error);
268
269    // Emit the serialized Clang AST into its own section.
270    assert(Buffer->IsComplete && "serialization did not complete");
271    auto &SerializedAST = Buffer->Data;
272    auto Size = SerializedAST.size();
273    auto Int8Ty = llvm::Type::getInt8Ty(*VMContext);
274    auto *Ty = llvm::ArrayType::get(Int8Ty, Size);
275    auto *Data = llvm::ConstantDataArray::getString(
276        *VMContext, StringRef(SerializedAST.data(), Size),
277        /*AddNull=*/false);
278    auto *ASTSym = new llvm::GlobalVariable(
279        *M, Ty, /*constant*/ true, llvm::GlobalVariable::InternalLinkage, Data,
280        "__clang_ast");
281    // The on-disk hashtable needs to be aligned.
282    ASTSym->setAlignment(llvm::Align(8));
283
284    // Mach-O also needs a segment name.
285    if (Triple.isOSBinFormatMachO())
286      ASTSym->setSection("__CLANG,__clangast");
287    // COFF has an eight character length limit.
288    else if (Triple.isOSBinFormatCOFF())
289      ASTSym->setSection("clangast");
290    else
291      ASTSym->setSection("__clangast");
292
293    LLVM_DEBUG({
294      // Print the IR for the PCH container to the debug output.
295      llvm::SmallString<0> Buffer;
296      clang::EmitBackendOutput(
297          Diags, HeaderSearchOpts, CodeGenOpts, TargetOpts, LangOpts,
298          Ctx.getTargetInfo().getDataLayout(), M.get(),
299          BackendAction::Backend_EmitLL,
300          std::make_unique<llvm::raw_svector_ostream>(Buffer));
301      llvm::dbgs() << Buffer;
302    });
303
304    // Use the LLVM backend to emit the pch container.
305    clang::EmitBackendOutput(Diags, HeaderSearchOpts, CodeGenOpts, TargetOpts,
306                             LangOpts, Ctx.getTargetInfo().getDataLayout(),
307                             M.get(), BackendAction::Backend_EmitObj,
308                             std::move(OS));
309
310    // Free the memory for the temporary buffer.
311    llvm::SmallVector<char, 0> Empty;
312    SerializedAST = std::move(Empty);
313  }
314};
315
316} // anonymous namespace
317
318std::unique_ptr<ASTConsumer>
319ObjectFilePCHContainerWriter::CreatePCHContainerGenerator(
320    CompilerInstance &CI, const std::string &MainFileName,
321    const std::string &OutputFileName,
322    std::unique_ptr<llvm::raw_pwrite_stream> OS,
323    std::shared_ptr<PCHBuffer> Buffer) const {
324  return std::make_unique<PCHContainerGenerator>(
325      CI, MainFileName, OutputFileName, std::move(OS), Buffer);
326}
327
328StringRef
329ObjectFilePCHContainerReader::ExtractPCH(llvm::MemoryBufferRef Buffer) const {
330  StringRef PCH;
331  auto OFOrErr = llvm::object::ObjectFile::createObjectFile(Buffer);
332  if (OFOrErr) {
333    auto &OF = OFOrErr.get();
334    bool IsCOFF = isa<llvm::object::COFFObjectFile>(*OF);
335    // Find the clang AST section in the container.
336    for (auto &Section : OF->sections()) {
337      StringRef Name;
338      if (Expected<StringRef> NameOrErr = Section.getName())
339        Name = *NameOrErr;
340      else
341        consumeError(NameOrErr.takeError());
342
343      if ((!IsCOFF && Name == "__clangast") || (IsCOFF && Name == "clangast")) {
344        if (Expected<StringRef> E = Section.getContents())
345          return *E;
346        else {
347          handleAllErrors(E.takeError(), [&](const llvm::ErrorInfoBase &EIB) {
348            EIB.log(llvm::errs());
349          });
350          return "";
351        }
352      }
353    }
354  }
355  handleAllErrors(OFOrErr.takeError(), [&](const llvm::ErrorInfoBase &EIB) {
356    if (EIB.convertToErrorCode() ==
357        llvm::object::object_error::invalid_file_type)
358      // As a fallback, treat the buffer as a raw AST.
359      PCH = Buffer.getBuffer();
360    else
361      EIB.log(llvm::errs());
362  });
363  return PCH;
364}
365