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), 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     Ctx = &Context;
75     VMContext.reset(new llvm::LLVMContext());
76     M.reset(new llvm::Module(MainFileName, *VMContext));
77     M->setDataLayout(Ctx->getTargetInfo().getTargetDescription());
78     Builder.reset(new CodeGen::CodeGenModule(
79         *Ctx, HeaderSearchOpts, PreprocessorOpts, CodeGenOpts, *M, Diags));
80   }
81 
82   /// Emit a container holding the serialized AST.
83   void HandleTranslationUnit(ASTContext &Ctx) override {
84     assert(M && VMContext && Builder);
85     // Delete these on function exit.
86     std::unique_ptr<llvm::LLVMContext> VMContext = std::move(this->VMContext);
87     std::unique_ptr<llvm::Module> M = std::move(this->M);
88     std::unique_ptr<CodeGen::CodeGenModule> Builder = std::move(this->Builder);
89 
90     if (Diags.hasErrorOccurred())
91       return;
92 
93     M->setTargetTriple(Ctx.getTargetInfo().getTriple().getTriple());
94     M->setDataLayout(Ctx.getTargetInfo().getTargetDescription());
95 
96     // Finalize the Builder.
97     if (Builder)
98       Builder->Release();
99 
100     // Ensure the target exists.
101     std::string Error;
102     auto Triple = Ctx.getTargetInfo().getTriple();
103     if (!llvm::TargetRegistry::lookupTarget(Triple.getTriple(), Error))
104       llvm::report_fatal_error(Error);
105 
106     // Emit the serialized Clang AST into its own section.
107     assert(Buffer->IsComplete && "serialization did not complete");
108     auto &SerializedAST = Buffer->Data;
109     auto Size = SerializedAST.size();
110     auto Int8Ty = llvm::Type::getInt8Ty(*VMContext);
111     auto *Ty = llvm::ArrayType::get(Int8Ty, Size);
112     auto *Data = llvm::ConstantDataArray::getString(
113         *VMContext, StringRef(SerializedAST.data(), Size),
114         /*AddNull=*/false);
115     auto *ASTSym = new llvm::GlobalVariable(
116         *M, Ty, /*constant*/ true, llvm::GlobalVariable::InternalLinkage, Data,
117         "__clang_ast");
118     // The on-disk hashtable needs to be aligned.
119     ASTSym->setAlignment(8);
120 
121     // Mach-O also needs a segment name.
122     if (Triple.isOSBinFormatMachO())
123       ASTSym->setSection("__CLANG,__clangast");
124     // COFF has an eight character length limit.
125     else if (Triple.isOSBinFormatCOFF())
126       ASTSym->setSection("clangast");
127     else
128       ASTSym->setSection("__clangast");
129 
130     DEBUG({
131       // Print the IR for the PCH container to the debug output.
132       llvm::SmallString<0> Buffer;
133       llvm::raw_svector_ostream OS(Buffer);
134       clang::EmitBackendOutput(Diags, CodeGenOpts, TargetOpts, LangOpts,
135                                Ctx.getTargetInfo().getTargetDescription(),
136                                M.get(), BackendAction::Backend_EmitLL, &OS);
137       OS.flush();
138       llvm::dbgs() << Buffer;
139     });
140 
141     // Use the LLVM backend to emit the pch container.
142     clang::EmitBackendOutput(Diags, CodeGenOpts, TargetOpts, LangOpts,
143                              Ctx.getTargetInfo().getTargetDescription(),
144                              M.get(), BackendAction::Backend_EmitObj, OS);
145 
146     // Make sure the pch container hits disk.
147     OS->flush();
148 
149     // Free the memory for the temporary buffer.
150     llvm::SmallVector<char, 0> Empty;
151     SerializedAST = std::move(Empty);
152   }
153 };
154 
155 } // namespace
156 
157 std::unique_ptr<ASTConsumer>
158 ObjectFilePCHContainerWriter::CreatePCHContainerGenerator(
159     DiagnosticsEngine &Diags, const HeaderSearchOptions &HSO,
160     const PreprocessorOptions &PPO, const TargetOptions &TO,
161     const LangOptions &LO, const std::string &MainFileName,
162     const std::string &OutputFileName, llvm::raw_pwrite_stream *OS,
163     std::shared_ptr<PCHBuffer> Buffer) const {
164   return llvm::make_unique<PCHContainerGenerator>(
165       Diags, HSO, PPO, TO, LO, MainFileName, OutputFileName, OS, Buffer);
166 }
167 
168 void ObjectFilePCHContainerReader::ExtractPCH(
169     llvm::MemoryBufferRef Buffer, llvm::BitstreamReader &StreamFile) const {
170   if (auto OF = llvm::object::ObjectFile::createObjectFile(Buffer)) {
171     auto *Obj = OF.get().get();
172     bool IsCOFF = isa<llvm::object::COFFObjectFile>(Obj);
173     // Find the clang AST section in the container.
174     for (auto &Section : OF->get()->sections()) {
175       StringRef Name;
176       Section.getName(Name);
177       if ((!IsCOFF && Name == "__clangast") ||
178           ( IsCOFF && Name ==   "clangast")) {
179         StringRef Buf;
180         Section.getContents(Buf);
181         StreamFile.init((const unsigned char *)Buf.begin(),
182                         (const unsigned char *)Buf.end());
183         return;
184       }
185     }
186   }
187 
188   // As a fallback, treat the buffer as a raw AST.
189   StreamFile.init((const unsigned char *)Buffer.getBufferStart(),
190                   (const unsigned char *)Buffer.getBufferEnd());
191   return;
192 }
193