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(*Ctx, HeaderSearchOpts,
79                                              PreprocessorOpts, CodeGenOpts, *M,
80                                              M->getDataLayout(), Diags));
81   }
82 
83   /// Emit a container holding the serialized AST.
84   void HandleTranslationUnit(ASTContext &Ctx) override {
85     assert(M && VMContext && Builder);
86     // Delete these on function exit.
87     std::unique_ptr<llvm::LLVMContext> VMContext = std::move(this->VMContext);
88     std::unique_ptr<llvm::Module> M = std::move(this->M);
89     std::unique_ptr<CodeGen::CodeGenModule> Builder = std::move(this->Builder);
90 
91     if (Diags.hasErrorOccurred())
92       return;
93 
94     M->setTargetTriple(Ctx.getTargetInfo().getTriple().getTriple());
95     M->setDataLayout(Ctx.getTargetInfo().getTargetDescription());
96 
97     // Finalize the Builder.
98     if (Builder)
99       Builder->Release();
100 
101     // Ensure the target exists.
102     std::string Error;
103     auto Triple = Ctx.getTargetInfo().getTriple();
104     if (!llvm::TargetRegistry::lookupTarget(Triple.getTriple(), Error))
105       llvm::report_fatal_error(Error);
106 
107     // Emit the serialized Clang AST into its own section.
108     assert(Buffer->IsComplete && "serialization did not complete");
109     auto &SerializedAST = Buffer->Data;
110     auto Size = SerializedAST.size();
111     auto Int8Ty = llvm::Type::getInt8Ty(*VMContext);
112     auto *Ty = llvm::ArrayType::get(Int8Ty, Size);
113     auto *Data = llvm::ConstantDataArray::getString(
114         *VMContext, StringRef(SerializedAST.data(), Size),
115         /*AddNull=*/false);
116     auto *ASTSym = new llvm::GlobalVariable(
117         *M, Ty, /*constant*/ true, llvm::GlobalVariable::InternalLinkage, Data,
118         "__clang_ast");
119     // The on-disk hashtable needs to be aligned.
120     ASTSym->setAlignment(8);
121 
122     // Mach-O also needs a segment name.
123     if (Triple.isOSBinFormatMachO())
124       ASTSym->setSection("__CLANG,__clangast");
125     // COFF has an eight character length limit.
126     else if (Triple.isOSBinFormatCOFF())
127       ASTSym->setSection("clangast");
128     else
129       ASTSym->setSection("__clangast");
130 
131     DEBUG({
132       // Print the IR for the PCH container to the debug output.
133       llvm::SmallString<0> Buffer;
134       llvm::raw_svector_ostream OS(Buffer);
135       clang::EmitBackendOutput(Diags, CodeGenOpts, TargetOpts, LangOpts,
136                                Ctx.getTargetInfo().getTargetDescription(),
137                                M.get(), BackendAction::Backend_EmitLL, &OS);
138       OS.flush();
139       llvm::dbgs() << Buffer;
140     });
141 
142     // Use the LLVM backend to emit the pch container.
143     clang::EmitBackendOutput(Diags, CodeGenOpts, TargetOpts, LangOpts,
144                              Ctx.getTargetInfo().getTargetDescription(),
145                              M.get(), BackendAction::Backend_EmitObj, OS);
146 
147     // Make sure the pch container hits disk.
148     OS->flush();
149 
150     // Free the memory for the temporary buffer.
151     llvm::SmallVector<char, 0> Empty;
152     SerializedAST = std::move(Empty);
153   }
154 };
155 
156 } // namespace
157 
158 std::unique_ptr<ASTConsumer>
159 ObjectFilePCHContainerWriter::CreatePCHContainerGenerator(
160     DiagnosticsEngine &Diags, const HeaderSearchOptions &HSO,
161     const PreprocessorOptions &PPO, const TargetOptions &TO,
162     const LangOptions &LO, const std::string &MainFileName,
163     const std::string &OutputFileName, llvm::raw_pwrite_stream *OS,
164     std::shared_ptr<PCHBuffer> Buffer) const {
165   return llvm::make_unique<PCHContainerGenerator>(
166       Diags, HSO, PPO, TO, LO, MainFileName, OutputFileName, OS, Buffer);
167 }
168 
169 void ObjectFilePCHContainerReader::ExtractPCH(
170     llvm::MemoryBufferRef Buffer, llvm::BitstreamReader &StreamFile) const {
171   if (auto OF = llvm::object::ObjectFile::createObjectFile(Buffer)) {
172     auto *Obj = OF.get().get();
173     bool IsCOFF = isa<llvm::object::COFFObjectFile>(Obj);
174     // Find the clang AST section in the container.
175     for (auto &Section : OF->get()->sections()) {
176       StringRef Name;
177       Section.getName(Name);
178       if ((!IsCOFF && Name == "__clangast") ||
179           ( IsCOFF && Name ==   "clangast")) {
180         StringRef Buf;
181         Section.getContents(Buf);
182         StreamFile.init((const unsigned char *)Buf.begin(),
183                         (const unsigned char *)Buf.end());
184         return;
185       }
186     }
187   }
188 
189   // As a fallback, treat the buffer as a raw AST.
190   StreamFile.init((const unsigned char *)Buffer.getBufferStart(),
191                   (const unsigned char *)Buffer.getBufferEnd());
192   return;
193 }
194