1 //===--- ObjectFilePCHContainerOperations.cpp -----------------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #include "clang/CodeGen/ObjectFilePCHContainerOperations.h"
11 #include "CGDebugInfo.h"
12 #include "CodeGenModule.h"
13 #include "clang/AST/ASTContext.h"
14 #include "clang/AST/DeclObjC.h"
15 #include "clang/AST/Expr.h"
16 #include "clang/AST/RecursiveASTVisitor.h"
17 #include "clang/Basic/Diagnostic.h"
18 #include "clang/Basic/TargetInfo.h"
19 #include "clang/CodeGen/BackendUtil.h"
20 #include "clang/Frontend/CodeGenOptions.h"
21 #include "clang/Serialization/ASTWriter.h"
22 #include "llvm/ADT/StringRef.h"
23 #include "llvm/Bitcode/BitstreamReader.h"
24 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
25 #include "llvm/IR/Constants.h"
26 #include "llvm/IR/DataLayout.h"
27 #include "llvm/IR/LLVMContext.h"
28 #include "llvm/IR/Module.h"
29 #include "llvm/Object/COFF.h"
30 #include "llvm/Object/ObjectFile.h"
31 #include "llvm/Support/TargetRegistry.h"
32 #include <memory>
33 using namespace clang;
34 
35 #define DEBUG_TYPE "pchcontainer"
36 
37 namespace {
38 class PCHContainerGenerator : public ASTConsumer {
39   DiagnosticsEngine &Diags;
40   const std::string MainFileName;
41   ASTContext *Ctx;
42   const HeaderSearchOptions &HeaderSearchOpts;
43   const PreprocessorOptions &PreprocessorOpts;
44   CodeGenOptions CodeGenOpts;
45   const TargetOptions TargetOpts;
46   const LangOptions LangOpts;
47   std::unique_ptr<llvm::LLVMContext> VMContext;
48   std::unique_ptr<llvm::Module> M;
49   std::unique_ptr<CodeGen::CodeGenModule> Builder;
50   raw_pwrite_stream *OS;
51   std::shared_ptr<PCHBuffer> Buffer;
52 
53 public:
54   PCHContainerGenerator(DiagnosticsEngine &diags,
55                         const HeaderSearchOptions &HSO,
56                         const PreprocessorOptions &PPO, const TargetOptions &TO,
57                         const LangOptions &LO, const std::string &MainFileName,
58                         const std::string &OutputFileName,
59                         raw_pwrite_stream *OS,
60                         std::shared_ptr<PCHBuffer> Buffer)
61       : Diags(diags), Ctx(nullptr), HeaderSearchOpts(HSO), PreprocessorOpts(PPO),
62         TargetOpts(TO), LangOpts(LO), OS(OS), Buffer(Buffer) {
63     // The debug info output isn't affected by CodeModel and
64     // ThreadModel, but the backend expects them to be nonempty.
65     CodeGenOpts.CodeModel = "default";
66     CodeGenOpts.ThreadModel = "single";
67     CodeGenOpts.setDebugInfo(CodeGenOptions::FullDebugInfo);
68     CodeGenOpts.SplitDwarfFile = OutputFileName;
69   }
70 
71   virtual ~PCHContainerGenerator() {}
72 
73   void Initialize(ASTContext &Context) override {
74     if (Ctx) {
75       assert(Ctx == &Context);
76       return;
77     }
78 
79     Ctx = &Context;
80     VMContext.reset(new llvm::LLVMContext());
81     M.reset(new llvm::Module(MainFileName, *VMContext));
82     M->setDataLayout(Ctx->getTargetInfo().getDataLayoutString());
83     Builder.reset(new CodeGen::CodeGenModule(
84         *Ctx, HeaderSearchOpts, PreprocessorOpts, CodeGenOpts, *M, Diags));
85   }
86 
87   /// Emit a container holding the serialized AST.
88   void HandleTranslationUnit(ASTContext &Ctx) override {
89     assert(M && VMContext && Builder);
90     // Delete these on function exit.
91     std::unique_ptr<llvm::LLVMContext> VMContext = std::move(this->VMContext);
92     std::unique_ptr<llvm::Module> M = std::move(this->M);
93     std::unique_ptr<CodeGen::CodeGenModule> Builder = std::move(this->Builder);
94 
95     if (Diags.hasErrorOccurred())
96       return;
97 
98     M->setTargetTriple(Ctx.getTargetInfo().getTriple().getTriple());
99     M->setDataLayout(Ctx.getTargetInfo().getDataLayoutString());
100 
101     // Finalize the Builder.
102     if (Builder)
103       Builder->Release();
104 
105     // Ensure the target exists.
106     std::string Error;
107     auto Triple = Ctx.getTargetInfo().getTriple();
108     if (!llvm::TargetRegistry::lookupTarget(Triple.getTriple(), Error))
109       llvm::report_fatal_error(Error);
110 
111     // Emit the serialized Clang AST into its own section.
112     assert(Buffer->IsComplete && "serialization did not complete");
113     auto &SerializedAST = Buffer->Data;
114     auto Size = SerializedAST.size();
115     auto Int8Ty = llvm::Type::getInt8Ty(*VMContext);
116     auto *Ty = llvm::ArrayType::get(Int8Ty, Size);
117     auto *Data = llvm::ConstantDataArray::getString(
118         *VMContext, StringRef(SerializedAST.data(), Size),
119         /*AddNull=*/false);
120     auto *ASTSym = new llvm::GlobalVariable(
121         *M, Ty, /*constant*/ true, llvm::GlobalVariable::InternalLinkage, Data,
122         "__clang_ast");
123     // The on-disk hashtable needs to be aligned.
124     ASTSym->setAlignment(8);
125 
126     // Mach-O also needs a segment name.
127     if (Triple.isOSBinFormatMachO())
128       ASTSym->setSection("__CLANG,__clangast");
129     // COFF has an eight character length limit.
130     else if (Triple.isOSBinFormatCOFF())
131       ASTSym->setSection("clangast");
132     else
133       ASTSym->setSection("__clangast");
134 
135     DEBUG({
136       // Print the IR for the PCH container to the debug output.
137       llvm::SmallString<0> Buffer;
138       llvm::raw_svector_ostream OS(Buffer);
139       clang::EmitBackendOutput(Diags, CodeGenOpts, TargetOpts, LangOpts,
140                                Ctx.getTargetInfo().getDataLayoutString(),
141                                M.get(), BackendAction::Backend_EmitLL, &OS);
142       OS.flush();
143       llvm::dbgs() << Buffer;
144     });
145 
146     // Use the LLVM backend to emit the pch container.
147     clang::EmitBackendOutput(Diags, CodeGenOpts, TargetOpts, LangOpts,
148                              Ctx.getTargetInfo().getDataLayoutString(),
149                              M.get(), BackendAction::Backend_EmitObj, OS);
150 
151     // Make sure the pch container hits disk.
152     OS->flush();
153 
154     // Free the memory for the temporary buffer.
155     llvm::SmallVector<char, 0> Empty;
156     SerializedAST = std::move(Empty);
157   }
158 };
159 
160 } // namespace
161 
162 std::unique_ptr<ASTConsumer>
163 ObjectFilePCHContainerWriter::CreatePCHContainerGenerator(
164     DiagnosticsEngine &Diags, const HeaderSearchOptions &HSO,
165     const PreprocessorOptions &PPO, const TargetOptions &TO,
166     const LangOptions &LO, const std::string &MainFileName,
167     const std::string &OutputFileName, llvm::raw_pwrite_stream *OS,
168     std::shared_ptr<PCHBuffer> Buffer) const {
169   return llvm::make_unique<PCHContainerGenerator>(
170       Diags, HSO, PPO, TO, LO, MainFileName, OutputFileName, OS, Buffer);
171 }
172 
173 void ObjectFilePCHContainerReader::ExtractPCH(
174     llvm::MemoryBufferRef Buffer, llvm::BitstreamReader &StreamFile) const {
175   if (auto OF = llvm::object::ObjectFile::createObjectFile(Buffer)) {
176     auto *Obj = OF.get().get();
177     bool IsCOFF = isa<llvm::object::COFFObjectFile>(Obj);
178     // Find the clang AST section in the container.
179     for (auto &Section : OF->get()->sections()) {
180       StringRef Name;
181       Section.getName(Name);
182       if ((!IsCOFF && Name == "__clangast") ||
183           ( IsCOFF && Name ==   "clangast")) {
184         StringRef Buf;
185         Section.getContents(Buf);
186         StreamFile.init((const unsigned char *)Buf.begin(),
187                         (const unsigned char *)Buf.end());
188         return;
189       }
190     }
191   }
192 
193   // As a fallback, treat the buffer as a raw AST.
194   StreamFile.init((const unsigned char *)Buffer.getBufferStart(),
195                   (const unsigned char *)Buffer.getBufferEnd());
196   return;
197 }
198