CGDeclCXX.cpp revision 203955 
1//===--- CGDeclCXX.cpp - Emit LLVM Code for C++ declarations --------------===//
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// This contains code dealing with code generation of C++ declarations
11//
12//===----------------------------------------------------------------------===//
13
14#include "CodeGenFunction.h"
15using namespace clang;
16using namespace CodeGen;
17
18static void EmitDeclInit(CodeGenFunction &CGF, const VarDecl &D,
19                         llvm::Constant *DeclPtr) {
20  assert(D.hasGlobalStorage() && "VarDecl must have global storage!");
21  assert(!D.getType()->isReferenceType() &&
22         "Should not call EmitDeclInit on a reference!");
23
24  CodeGenModule &CGM = CGF.CGM;
25  ASTContext &Context = CGF.getContext();
26
27  const Expr *Init = D.getInit();
28  QualType T = D.getType();
29  bool isVolatile = Context.getCanonicalType(T).isVolatileQualified();
30
31  if (!CGF.hasAggregateLLVMType(T)) {
32    llvm::Value *V = CGF.EmitScalarExpr(Init);
33    CGF.EmitStoreOfScalar(V, DeclPtr, isVolatile, T);
34  } else if (T->isAnyComplexType()) {
35    CGF.EmitComplexExprIntoAddr(Init, DeclPtr, isVolatile);
36  } else {
37    CGF.EmitAggExpr(Init, DeclPtr, isVolatile);
38
39    // Avoid generating destructor(s) for initialized objects.
40    if (!isa<CXXConstructExpr>(Init))
41      return;
42
43    const ConstantArrayType *Array = Context.getAsConstantArrayType(T);
44    if (Array)
45      T = Context.getBaseElementType(Array);
46
47    const RecordType *RT = T->getAs<RecordType>();
48    if (!RT)
49      return;
50
51    CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
52    if (RD->hasTrivialDestructor())
53      return;
54
55    CXXDestructorDecl *Dtor = RD->getDestructor(Context);
56
57    llvm::Constant *DtorFn;
58    if (Array) {
59      DtorFn =
60        CodeGenFunction(CGM).GenerateCXXAggrDestructorHelper(Dtor,
61                                                             Array,
62                                                             DeclPtr);
63      const llvm::Type *Int8PtrTy =
64        llvm::Type::getInt8PtrTy(CGM.getLLVMContext());
65      DeclPtr = llvm::Constant::getNullValue(Int8PtrTy);
66     } else
67      DtorFn = CGM.GetAddrOfCXXDestructor(Dtor, Dtor_Complete);
68
69    CGF.EmitCXXGlobalDtorRegistration(DtorFn, DeclPtr);
70  }
71}
72
73void CodeGenFunction::EmitCXXGlobalVarDeclInit(const VarDecl &D,
74                                               llvm::Constant *DeclPtr) {
75
76  const Expr *Init = D.getInit();
77  QualType T = D.getType();
78
79  if (!T->isReferenceType()) {
80    EmitDeclInit(*this, D, DeclPtr);
81    return;
82  }
83  if (Init->isLvalue(getContext()) == Expr::LV_Valid) {
84    RValue RV = EmitReferenceBindingToExpr(Init, /*IsInitializer=*/true);
85    EmitStoreOfScalar(RV.getScalarVal(), DeclPtr, false, T);
86    return;
87  }
88  ErrorUnsupported(Init,
89                   "global variable that binds reference to a non-lvalue");
90}
91
92void
93CodeGenFunction::EmitCXXGlobalDtorRegistration(llvm::Constant *DtorFn,
94                                               llvm::Constant *DeclPtr) {
95  const llvm::Type *Int8PtrTy =
96    llvm::Type::getInt8Ty(VMContext)->getPointerTo();
97
98  std::vector<const llvm::Type *> Params;
99  Params.push_back(Int8PtrTy);
100
101  // Get the destructor function type
102  const llvm::Type *DtorFnTy =
103    llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext), Params, false);
104  DtorFnTy = llvm::PointerType::getUnqual(DtorFnTy);
105
106  Params.clear();
107  Params.push_back(DtorFnTy);
108  Params.push_back(Int8PtrTy);
109  Params.push_back(Int8PtrTy);
110
111  // Get the __cxa_atexit function type
112  // extern "C" int __cxa_atexit ( void (*f)(void *), void *p, void *d );
113  const llvm::FunctionType *AtExitFnTy =
114    llvm::FunctionType::get(ConvertType(getContext().IntTy), Params, false);
115
116  llvm::Constant *AtExitFn = CGM.CreateRuntimeFunction(AtExitFnTy,
117                                                       "__cxa_atexit");
118
119  llvm::Constant *Handle = CGM.CreateRuntimeVariable(Int8PtrTy,
120                                                     "__dso_handle");
121  llvm::Value *Args[3] = { llvm::ConstantExpr::getBitCast(DtorFn, DtorFnTy),
122                           llvm::ConstantExpr::getBitCast(DeclPtr, Int8PtrTy),
123                           llvm::ConstantExpr::getBitCast(Handle, Int8PtrTy) };
124  Builder.CreateCall(AtExitFn, &Args[0], llvm::array_endof(Args));
125}
126
127void
128CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D) {
129  const llvm::FunctionType *FTy
130    = llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext),
131                              false);
132
133  // Create a variable initialization function.
134  llvm::Function *Fn =
135    llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage,
136                           "__cxx_global_var_init", &TheModule);
137
138  CodeGenFunction(*this).GenerateCXXGlobalVarDeclInitFunc(Fn, D);
139
140  CXXGlobalInits.push_back(Fn);
141}
142
143void
144CodeGenModule::EmitCXXGlobalInitFunc() {
145  if (CXXGlobalInits.empty())
146    return;
147
148  const llvm::FunctionType *FTy
149    = llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext),
150                              false);
151
152  // Create our global initialization function.
153  // FIXME: Should this be tweakable by targets?
154  llvm::Function *Fn =
155    llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage,
156                           "__cxx_global_initialization", &TheModule);
157
158  CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn,
159                                                   &CXXGlobalInits[0],
160                                                   CXXGlobalInits.size());
161  AddGlobalCtor(Fn);
162}
163
164void CodeGenFunction::GenerateCXXGlobalVarDeclInitFunc(llvm::Function *Fn,
165                                                       const VarDecl *D) {
166  StartFunction(GlobalDecl(), getContext().VoidTy, Fn, FunctionArgList(),
167                SourceLocation());
168
169  llvm::Constant *DeclPtr = CGM.GetAddrOfGlobalVar(D);
170  EmitCXXGlobalVarDeclInit(*D, DeclPtr);
171
172  FinishFunction();
173}
174
175void CodeGenFunction::GenerateCXXGlobalInitFunc(llvm::Function *Fn,
176                                                llvm::Constant **Decls,
177                                                unsigned NumDecls) {
178  StartFunction(GlobalDecl(), getContext().VoidTy, Fn, FunctionArgList(),
179                SourceLocation());
180
181  for (unsigned i = 0; i != NumDecls; ++i)
182    Builder.CreateCall(Decls[i]);
183
184  FinishFunction();
185}
186
187static llvm::Constant *getGuardAcquireFn(CodeGenFunction &CGF) {
188  // int __cxa_guard_acquire(__int64_t *guard_object);
189
190  const llvm::Type *Int64PtrTy =
191    llvm::Type::getInt64PtrTy(CGF.getLLVMContext());
192
193  std::vector<const llvm::Type*> Args(1, Int64PtrTy);
194
195  const llvm::FunctionType *FTy =
196    llvm::FunctionType::get(CGF.ConvertType(CGF.getContext().IntTy),
197                            Args, /*isVarArg=*/false);
198
199  return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_guard_acquire");
200}
201
202static llvm::Constant *getGuardReleaseFn(CodeGenFunction &CGF) {
203  // void __cxa_guard_release(__int64_t *guard_object);
204
205  const llvm::Type *Int64PtrTy =
206    llvm::Type::getInt64PtrTy(CGF.getLLVMContext());
207
208  std::vector<const llvm::Type*> Args(1, Int64PtrTy);
209
210  const llvm::FunctionType *FTy =
211  llvm::FunctionType::get(llvm::Type::getVoidTy(CGF.getLLVMContext()),
212                          Args, /*isVarArg=*/false);
213
214  return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_guard_release");
215}
216
217static llvm::Constant *getGuardAbortFn(CodeGenFunction &CGF) {
218  // void __cxa_guard_abort(__int64_t *guard_object);
219
220  const llvm::Type *Int64PtrTy =
221    llvm::Type::getInt64PtrTy(CGF.getLLVMContext());
222
223  std::vector<const llvm::Type*> Args(1, Int64PtrTy);
224
225  const llvm::FunctionType *FTy =
226  llvm::FunctionType::get(llvm::Type::getVoidTy(CGF.getLLVMContext()),
227                          Args, /*isVarArg=*/false);
228
229  return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_guard_abort");
230}
231
232void
233CodeGenFunction::EmitStaticCXXBlockVarDeclInit(const VarDecl &D,
234                                               llvm::GlobalVariable *GV) {
235  bool ThreadsafeStatics = getContext().getLangOptions().ThreadsafeStatics;
236
237  llvm::SmallString<256> GuardVName;
238  CGM.getMangleContext().mangleGuardVariable(&D, GuardVName);
239
240  // Create the guard variable.
241  const llvm::Type *Int64Ty = llvm::Type::getInt64Ty(VMContext);
242  llvm::GlobalValue *GuardVariable =
243    new llvm::GlobalVariable(CGM.getModule(), Int64Ty,
244                             false, GV->getLinkage(),
245                             llvm::Constant::getNullValue(Int64Ty),
246                             GuardVName.str());
247
248  // Load the first byte of the guard variable.
249  const llvm::Type *PtrTy
250    = llvm::PointerType::get(llvm::Type::getInt8Ty(VMContext), 0);
251  llvm::Value *V =
252    Builder.CreateLoad(Builder.CreateBitCast(GuardVariable, PtrTy), "tmp");
253
254  llvm::BasicBlock *InitCheckBlock = createBasicBlock("init.check");
255  llvm::BasicBlock *EndBlock = createBasicBlock("init.end");
256
257  // Check if the first byte of the guard variable is zero.
258  Builder.CreateCondBr(Builder.CreateIsNull(V, "tobool"),
259                       InitCheckBlock, EndBlock);
260
261  EmitBlock(InitCheckBlock);
262
263  if (ThreadsafeStatics) {
264    // Call __cxa_guard_acquire.
265    V = Builder.CreateCall(getGuardAcquireFn(*this), GuardVariable);
266
267    llvm::BasicBlock *InitBlock = createBasicBlock("init");
268
269    Builder.CreateCondBr(Builder.CreateIsNotNull(V, "tobool"),
270                         InitBlock, EndBlock);
271
272    EmitBlock(InitBlock);
273
274    if (Exceptions) {
275      EHCleanupBlock Cleanup(*this);
276
277      // Call __cxa_guard_abort.
278      Builder.CreateCall(getGuardAbortFn(*this), GuardVariable);
279    }
280  }
281
282  if (D.getType()->isReferenceType()) {
283    QualType T = D.getType();
284    // We don't want to pass true for IsInitializer here, because a static
285    // reference to a temporary does not extend its lifetime.
286    RValue RV = EmitReferenceBindingToExpr(D.getInit(),
287                                           /*IsInitializer=*/false);
288    EmitStoreOfScalar(RV.getScalarVal(), GV, /*Volatile=*/false, T);
289
290  } else
291    EmitDeclInit(*this, D, GV);
292
293  if (ThreadsafeStatics) {
294    // Call __cxa_guard_release.
295    Builder.CreateCall(getGuardReleaseFn(*this), GuardVariable);
296  } else {
297    llvm::Value *One =
298      llvm::ConstantInt::get(llvm::Type::getInt8Ty(VMContext), 1);
299    Builder.CreateStore(One, Builder.CreateBitCast(GuardVariable, PtrTy));
300  }
301
302  EmitBlock(EndBlock);
303}
304