1 //===--- ModuleBuilder.cpp - Emit LLVM Code from ASTs ---------------------===//
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 // This builds an AST and converts it to LLVM Code.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "clang/CodeGen/ModuleBuilder.h"
14 #include "CGDebugInfo.h"
15 #include "CodeGenModule.h"
16 #include "clang/AST/ASTContext.h"
17 #include "clang/AST/DeclObjC.h"
18 #include "clang/AST/Expr.h"
19 #include "clang/Basic/CodeGenOptions.h"
20 #include "clang/Basic/Diagnostic.h"
21 #include "clang/Basic/TargetInfo.h"
22 #include "llvm/ADT/StringRef.h"
23 #include "llvm/IR/DataLayout.h"
24 #include "llvm/IR/LLVMContext.h"
25 #include "llvm/IR/Module.h"
26 #include "llvm/Support/VirtualFileSystem.h"
27 #include <memory>
28 
29 using namespace clang;
30 using namespace CodeGen;
31 
32 namespace {
33   class CodeGeneratorImpl : public CodeGenerator {
34     DiagnosticsEngine &Diags;
35     ASTContext *Ctx;
36     IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS; // Only used for debug info.
37     const HeaderSearchOptions &HeaderSearchOpts; // Only used for debug info.
38     const PreprocessorOptions &PreprocessorOpts; // Only used for debug info.
39     const CodeGenOptions CodeGenOpts;  // Intentionally copied in.
40 
41     unsigned HandlingTopLevelDecls;
42 
43     /// Use this when emitting decls to block re-entrant decl emission. It will
44     /// emit all deferred decls on scope exit. Set EmitDeferred to false if decl
45     /// emission must be deferred longer, like at the end of a tag definition.
46     struct HandlingTopLevelDeclRAII {
47       CodeGeneratorImpl &Self;
48       bool EmitDeferred;
49       HandlingTopLevelDeclRAII(CodeGeneratorImpl &Self,
50                                bool EmitDeferred = true)
51           : Self(Self), EmitDeferred(EmitDeferred) {
52         ++Self.HandlingTopLevelDecls;
53       }
54       ~HandlingTopLevelDeclRAII() {
55         unsigned Level = --Self.HandlingTopLevelDecls;
56         if (Level == 0 && EmitDeferred)
57           Self.EmitDeferredDecls();
58       }
59     };
60 
61     CoverageSourceInfo *CoverageInfo;
62 
63   protected:
64     std::unique_ptr<llvm::Module> M;
65     std::unique_ptr<CodeGen::CodeGenModule> Builder;
66 
67   private:
68     SmallVector<FunctionDecl *, 8> DeferredInlineMemberFuncDefs;
69 
70     static llvm::StringRef ExpandModuleName(llvm::StringRef ModuleName,
71                                             const CodeGenOptions &CGO) {
72       if (ModuleName == "-" && !CGO.MainFileName.empty())
73         return CGO.MainFileName;
74       return ModuleName;
75     }
76 
77   public:
78     CodeGeneratorImpl(DiagnosticsEngine &diags, llvm::StringRef ModuleName,
79                       IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS,
80                       const HeaderSearchOptions &HSO,
81                       const PreprocessorOptions &PPO, const CodeGenOptions &CGO,
82                       llvm::LLVMContext &C,
83                       CoverageSourceInfo *CoverageInfo = nullptr)
84         : Diags(diags), Ctx(nullptr), FS(std::move(FS)), HeaderSearchOpts(HSO),
85           PreprocessorOpts(PPO), CodeGenOpts(CGO), HandlingTopLevelDecls(0),
86           CoverageInfo(CoverageInfo),
87           M(new llvm::Module(ExpandModuleName(ModuleName, CGO), C)) {
88       C.setDiscardValueNames(CGO.DiscardValueNames);
89     }
90 
91     ~CodeGeneratorImpl() override {
92       // There should normally not be any leftover inline method definitions.
93       assert(DeferredInlineMemberFuncDefs.empty() ||
94              Diags.hasErrorOccurred());
95     }
96 
97     CodeGenModule &CGM() {
98       return *Builder;
99     }
100 
101     llvm::Module *GetModule() {
102       return M.get();
103     }
104 
105     CGDebugInfo *getCGDebugInfo() {
106       return Builder->getModuleDebugInfo();
107     }
108 
109     llvm::Module *ReleaseModule() {
110       return M.release();
111     }
112 
113     const Decl *GetDeclForMangledName(StringRef MangledName) {
114       GlobalDecl Result;
115       if (!Builder->lookupRepresentativeDecl(MangledName, Result))
116         return nullptr;
117       const Decl *D = Result.getCanonicalDecl().getDecl();
118       if (auto FD = dyn_cast<FunctionDecl>(D)) {
119         if (FD->hasBody(FD))
120           return FD;
121       } else if (auto TD = dyn_cast<TagDecl>(D)) {
122         if (auto Def = TD->getDefinition())
123           return Def;
124       }
125       return D;
126     }
127 
128     llvm::StringRef GetMangledName(GlobalDecl GD) {
129       return Builder->getMangledName(GD);
130     }
131 
132     llvm::Constant *GetAddrOfGlobal(GlobalDecl global, bool isForDefinition) {
133       return Builder->GetAddrOfGlobal(global, ForDefinition_t(isForDefinition));
134     }
135 
136     llvm::Module *StartModule(llvm::StringRef ModuleName,
137                               llvm::LLVMContext &C) {
138       assert(!M && "Replacing existing Module?");
139       M.reset(new llvm::Module(ExpandModuleName(ModuleName, CodeGenOpts), C));
140 
141       std::unique_ptr<CodeGenModule> OldBuilder = std::move(Builder);
142 
143       Initialize(*Ctx);
144 
145       if (OldBuilder)
146         OldBuilder->moveLazyEmissionStates(Builder.get());
147 
148       return M.get();
149     }
150 
151     void Initialize(ASTContext &Context) override {
152       Ctx = &Context;
153 
154       M->setTargetTriple(Ctx->getTargetInfo().getTriple().getTriple());
155       M->setDataLayout(Ctx->getTargetInfo().getDataLayoutString());
156       const auto &SDKVersion = Ctx->getTargetInfo().getSDKVersion();
157       if (!SDKVersion.empty())
158         M->setSDKVersion(SDKVersion);
159       if (const auto *TVT = Ctx->getTargetInfo().getDarwinTargetVariantTriple())
160         M->setDarwinTargetVariantTriple(TVT->getTriple());
161       if (auto TVSDKVersion =
162               Ctx->getTargetInfo().getDarwinTargetVariantSDKVersion())
163         M->setDarwinTargetVariantSDKVersion(*TVSDKVersion);
164       Builder.reset(new CodeGen::CodeGenModule(Context, FS, HeaderSearchOpts,
165                                                PreprocessorOpts, CodeGenOpts,
166                                                *M, Diags, CoverageInfo));
167 
168       for (auto &&Lib : CodeGenOpts.DependentLibraries)
169         Builder->AddDependentLib(Lib);
170       for (auto &&Opt : CodeGenOpts.LinkerOptions)
171         Builder->AppendLinkerOptions(Opt);
172     }
173 
174     void HandleCXXStaticMemberVarInstantiation(VarDecl *VD) override {
175       if (Diags.hasErrorOccurred())
176         return;
177 
178       Builder->HandleCXXStaticMemberVarInstantiation(VD);
179     }
180 
181     bool HandleTopLevelDecl(DeclGroupRef DG) override {
182       if (Diags.hasErrorOccurred())
183         return true;
184 
185       HandlingTopLevelDeclRAII HandlingDecl(*this);
186 
187       // Make sure to emit all elements of a Decl.
188       for (DeclGroupRef::iterator I = DG.begin(), E = DG.end(); I != E; ++I)
189         Builder->EmitTopLevelDecl(*I);
190 
191       return true;
192     }
193 
194     void EmitDeferredDecls() {
195       if (DeferredInlineMemberFuncDefs.empty())
196         return;
197 
198       // Emit any deferred inline method definitions. Note that more deferred
199       // methods may be added during this loop, since ASTConsumer callbacks
200       // can be invoked if AST inspection results in declarations being added.
201       HandlingTopLevelDeclRAII HandlingDecl(*this);
202       for (unsigned I = 0; I != DeferredInlineMemberFuncDefs.size(); ++I)
203         Builder->EmitTopLevelDecl(DeferredInlineMemberFuncDefs[I]);
204       DeferredInlineMemberFuncDefs.clear();
205     }
206 
207     void HandleInlineFunctionDefinition(FunctionDecl *D) override {
208       if (Diags.hasErrorOccurred())
209         return;
210 
211       assert(D->doesThisDeclarationHaveABody());
212 
213       // We may want to emit this definition. However, that decision might be
214       // based on computing the linkage, and we have to defer that in case we
215       // are inside of something that will change the method's final linkage,
216       // e.g.
217       //   typedef struct {
218       //     void bar();
219       //     void foo() { bar(); }
220       //   } A;
221       DeferredInlineMemberFuncDefs.push_back(D);
222 
223       // Provide some coverage mapping even for methods that aren't emitted.
224       // Don't do this for templated classes though, as they may not be
225       // instantiable.
226       if (!D->getLexicalDeclContext()->isDependentContext())
227         Builder->AddDeferredUnusedCoverageMapping(D);
228     }
229 
230     /// HandleTagDeclDefinition - This callback is invoked each time a TagDecl
231     /// to (e.g. struct, union, enum, class) is completed. This allows the
232     /// client hack on the type, which can occur at any point in the file
233     /// (because these can be defined in declspecs).
234     void HandleTagDeclDefinition(TagDecl *D) override {
235       if (Diags.hasErrorOccurred())
236         return;
237 
238       // Don't allow re-entrant calls to CodeGen triggered by PCH
239       // deserialization to emit deferred decls.
240       HandlingTopLevelDeclRAII HandlingDecl(*this, /*EmitDeferred=*/false);
241 
242       Builder->UpdateCompletedType(D);
243 
244       // For MSVC compatibility, treat declarations of static data members with
245       // inline initializers as definitions.
246       if (Ctx->getTargetInfo().getCXXABI().isMicrosoft()) {
247         for (Decl *Member : D->decls()) {
248           if (VarDecl *VD = dyn_cast<VarDecl>(Member)) {
249             if (Ctx->isMSStaticDataMemberInlineDefinition(VD) &&
250                 Ctx->DeclMustBeEmitted(VD)) {
251               Builder->EmitGlobal(VD);
252             }
253           }
254         }
255       }
256       // For OpenMP emit declare reduction functions, if required.
257       if (Ctx->getLangOpts().OpenMP) {
258         for (Decl *Member : D->decls()) {
259           if (auto *DRD = dyn_cast<OMPDeclareReductionDecl>(Member)) {
260             if (Ctx->DeclMustBeEmitted(DRD))
261               Builder->EmitGlobal(DRD);
262           } else if (auto *DMD = dyn_cast<OMPDeclareMapperDecl>(Member)) {
263             if (Ctx->DeclMustBeEmitted(DMD))
264               Builder->EmitGlobal(DMD);
265           }
266         }
267       }
268     }
269 
270     void HandleTagDeclRequiredDefinition(const TagDecl *D) override {
271       if (Diags.hasErrorOccurred())
272         return;
273 
274       // Don't allow re-entrant calls to CodeGen triggered by PCH
275       // deserialization to emit deferred decls.
276       HandlingTopLevelDeclRAII HandlingDecl(*this, /*EmitDeferred=*/false);
277 
278       if (CodeGen::CGDebugInfo *DI = Builder->getModuleDebugInfo())
279         if (const RecordDecl *RD = dyn_cast<RecordDecl>(D))
280           DI->completeRequiredType(RD);
281     }
282 
283     void HandleTranslationUnit(ASTContext &Ctx) override {
284       // Release the Builder when there is no error.
285       if (!Diags.hasErrorOccurred() && Builder)
286         Builder->Release();
287 
288       // If there are errors before or when releasing the Builder, reset
289       // the module to stop here before invoking the backend.
290       if (Diags.hasErrorOccurred()) {
291         if (Builder)
292           Builder->clear();
293         M.reset();
294         return;
295       }
296     }
297 
298     void AssignInheritanceModel(CXXRecordDecl *RD) override {
299       if (Diags.hasErrorOccurred())
300         return;
301 
302       Builder->RefreshTypeCacheForClass(RD);
303     }
304 
305     void CompleteTentativeDefinition(VarDecl *D) override {
306       if (Diags.hasErrorOccurred())
307         return;
308 
309       Builder->EmitTentativeDefinition(D);
310     }
311 
312     void CompleteExternalDeclaration(VarDecl *D) override {
313       Builder->EmitExternalDeclaration(D);
314     }
315 
316     void HandleVTable(CXXRecordDecl *RD) override {
317       if (Diags.hasErrorOccurred())
318         return;
319 
320       Builder->EmitVTable(RD);
321     }
322   };
323 }
324 
325 void CodeGenerator::anchor() { }
326 
327 CodeGenModule &CodeGenerator::CGM() {
328   return static_cast<CodeGeneratorImpl*>(this)->CGM();
329 }
330 
331 llvm::Module *CodeGenerator::GetModule() {
332   return static_cast<CodeGeneratorImpl*>(this)->GetModule();
333 }
334 
335 llvm::Module *CodeGenerator::ReleaseModule() {
336   return static_cast<CodeGeneratorImpl*>(this)->ReleaseModule();
337 }
338 
339 CGDebugInfo *CodeGenerator::getCGDebugInfo() {
340   return static_cast<CodeGeneratorImpl*>(this)->getCGDebugInfo();
341 }
342 
343 const Decl *CodeGenerator::GetDeclForMangledName(llvm::StringRef name) {
344   return static_cast<CodeGeneratorImpl*>(this)->GetDeclForMangledName(name);
345 }
346 
347 llvm::StringRef CodeGenerator::GetMangledName(GlobalDecl GD) {
348   return static_cast<CodeGeneratorImpl *>(this)->GetMangledName(GD);
349 }
350 
351 llvm::Constant *CodeGenerator::GetAddrOfGlobal(GlobalDecl global,
352                                                bool isForDefinition) {
353   return static_cast<CodeGeneratorImpl*>(this)
354            ->GetAddrOfGlobal(global, isForDefinition);
355 }
356 
357 llvm::Module *CodeGenerator::StartModule(llvm::StringRef ModuleName,
358                                          llvm::LLVMContext &C) {
359   return static_cast<CodeGeneratorImpl*>(this)->StartModule(ModuleName, C);
360 }
361 
362 CodeGenerator *
363 clang::CreateLLVMCodeGen(DiagnosticsEngine &Diags, llvm::StringRef ModuleName,
364                          IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS,
365                          const HeaderSearchOptions &HeaderSearchOpts,
366                          const PreprocessorOptions &PreprocessorOpts,
367                          const CodeGenOptions &CGO, llvm::LLVMContext &C,
368                          CoverageSourceInfo *CoverageInfo) {
369   return new CodeGeneratorImpl(Diags, ModuleName, std::move(FS),
370                                HeaderSearchOpts, PreprocessorOpts, CGO, C,
371                                CoverageInfo);
372 }
373