CGDeclCXX.cpp revision 205408 
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"
15#include "clang/CodeGen/CodeGenOptions.h"
16using namespace clang;
17using namespace CodeGen;
18
19static void EmitDeclInit(CodeGenFunction &CGF, const VarDecl &D,
20                         llvm::Constant *DeclPtr) {
21  assert(D.hasGlobalStorage() && "VarDecl must have global storage!");
22  assert(!D.getType()->isReferenceType() &&
23         "Should not call EmitDeclInit on a reference!");
24
25  CodeGenModule &CGM = CGF.CGM;
26  ASTContext &Context = CGF.getContext();
27
28  const Expr *Init = D.getInit();
29  QualType T = D.getType();
30  bool isVolatile = Context.getCanonicalType(T).isVolatileQualified();
31
32  if (!CGF.hasAggregateLLVMType(T)) {
33    llvm::Value *V = CGF.EmitScalarExpr(Init);
34    CGF.EmitStoreOfScalar(V, DeclPtr, isVolatile, T);
35  } else if (T->isAnyComplexType()) {
36    CGF.EmitComplexExprIntoAddr(Init, DeclPtr, isVolatile);
37  } else {
38    CGF.EmitAggExpr(Init, DeclPtr, isVolatile);
39
40    // Avoid generating destructor(s) for initialized objects.
41    if (!isa<CXXConstructExpr>(Init))
42      return;
43
44    const ConstantArrayType *Array = Context.getAsConstantArrayType(T);
45    if (Array)
46      T = Context.getBaseElementType(Array);
47
48    const RecordType *RT = T->getAs<RecordType>();
49    if (!RT)
50      return;
51
52    CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
53    if (RD->hasTrivialDestructor())
54      return;
55
56    CXXDestructorDecl *Dtor = RD->getDestructor(Context);
57
58    llvm::Constant *DtorFn;
59    if (Array) {
60      DtorFn =
61        CodeGenFunction(CGM).GenerateCXXAggrDestructorHelper(Dtor,
62                                                             Array,
63                                                             DeclPtr);
64      const llvm::Type *Int8PtrTy =
65        llvm::Type::getInt8PtrTy(CGM.getLLVMContext());
66      DeclPtr = llvm::Constant::getNullValue(Int8PtrTy);
67     } else
68      DtorFn = CGM.GetAddrOfCXXDestructor(Dtor, Dtor_Complete);
69
70    CGF.EmitCXXGlobalDtorRegistration(DtorFn, DeclPtr);
71  }
72}
73
74void CodeGenFunction::EmitCXXGlobalVarDeclInit(const VarDecl &D,
75                                               llvm::Constant *DeclPtr) {
76
77  const Expr *Init = D.getInit();
78  QualType T = D.getType();
79
80  if (!T->isReferenceType()) {
81    EmitDeclInit(*this, D, DeclPtr);
82    return;
83  }
84  if (Init->isLvalue(getContext()) == Expr::LV_Valid) {
85    RValue RV = EmitReferenceBindingToExpr(Init, /*IsInitializer=*/true);
86    EmitStoreOfScalar(RV.getScalarVal(), DeclPtr, false, T);
87    return;
88  }
89  ErrorUnsupported(Init,
90                   "global variable that binds reference to a non-lvalue");
91}
92
93void
94CodeGenFunction::EmitCXXGlobalDtorRegistration(llvm::Constant *DtorFn,
95                                               llvm::Constant *DeclPtr) {
96  // Generate a global destructor entry if not using __cxa_atexit.
97  if (!CGM.getCodeGenOpts().CXAAtExit) {
98    CGM.AddCXXDtorEntry(DtorFn, DeclPtr);
99    return;
100  }
101
102  const llvm::Type *Int8PtrTy =
103    llvm::Type::getInt8Ty(VMContext)->getPointerTo();
104
105  std::vector<const llvm::Type *> Params;
106  Params.push_back(Int8PtrTy);
107
108  // Get the destructor function type
109  const llvm::Type *DtorFnTy =
110    llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext), Params, false);
111  DtorFnTy = llvm::PointerType::getUnqual(DtorFnTy);
112
113  Params.clear();
114  Params.push_back(DtorFnTy);
115  Params.push_back(Int8PtrTy);
116  Params.push_back(Int8PtrTy);
117
118  // Get the __cxa_atexit function type
119  // extern "C" int __cxa_atexit ( void (*f)(void *), void *p, void *d );
120  const llvm::FunctionType *AtExitFnTy =
121    llvm::FunctionType::get(ConvertType(getContext().IntTy), Params, false);
122
123  llvm::Constant *AtExitFn = CGM.CreateRuntimeFunction(AtExitFnTy,
124                                                       "__cxa_atexit");
125
126  llvm::Constant *Handle = CGM.CreateRuntimeVariable(Int8PtrTy,
127                                                     "__dso_handle");
128  llvm::Value *Args[3] = { llvm::ConstantExpr::getBitCast(DtorFn, DtorFnTy),
129                           llvm::ConstantExpr::getBitCast(DeclPtr, Int8PtrTy),
130                           llvm::ConstantExpr::getBitCast(Handle, Int8PtrTy) };
131  Builder.CreateCall(AtExitFn, &Args[0], llvm::array_endof(Args));
132}
133
134void
135CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D) {
136  const llvm::FunctionType *FTy
137    = llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext),
138                              false);
139
140  // Create a variable initialization function.
141  llvm::Function *Fn =
142    llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage,
143                           "__cxx_global_var_init", &TheModule);
144
145  CodeGenFunction(*this).GenerateCXXGlobalVarDeclInitFunc(Fn, D);
146
147  CXXGlobalInits.push_back(Fn);
148}
149
150void
151CodeGenModule::EmitCXXGlobalInitFunc() {
152  if (CXXGlobalInits.empty())
153    return;
154
155  const llvm::FunctionType *FTy
156    = llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext),
157                              false);
158
159  // Create our global initialization function.
160  llvm::Function *Fn =
161    llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage,
162                           "_GLOBAL__I_a", &TheModule);
163
164  CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn,
165                                                   &CXXGlobalInits[0],
166                                                   CXXGlobalInits.size());
167  AddGlobalCtor(Fn);
168}
169
170void CodeGenModule::AddCXXDtorEntry(llvm::Constant *DtorFn,
171                                    llvm::Constant *Object) {
172  CXXGlobalDtors.push_back(std::make_pair(DtorFn, Object));
173}
174
175void CodeGenModule::EmitCXXGlobalDtorFunc() {
176  if (CXXGlobalDtors.empty())
177    return;
178
179  const llvm::FunctionType *FTy
180    = llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext),
181                              false);
182
183  // Create our global destructor function.
184  llvm::Function *Fn =
185    llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage,
186                           "_GLOBAL__D_a", &TheModule);
187
188  CodeGenFunction(*this).GenerateCXXGlobalDtorFunc(Fn, CXXGlobalDtors);
189  AddGlobalDtor(Fn);
190}
191
192void CodeGenFunction::GenerateCXXGlobalVarDeclInitFunc(llvm::Function *Fn,
193                                                       const VarDecl *D) {
194  StartFunction(GlobalDecl(), getContext().VoidTy, Fn, FunctionArgList(),
195                SourceLocation());
196
197  llvm::Constant *DeclPtr = CGM.GetAddrOfGlobalVar(D);
198  EmitCXXGlobalVarDeclInit(*D, DeclPtr);
199
200  FinishFunction();
201}
202
203void CodeGenFunction::GenerateCXXGlobalInitFunc(llvm::Function *Fn,
204                                                llvm::Constant **Decls,
205                                                unsigned NumDecls) {
206  StartFunction(GlobalDecl(), getContext().VoidTy, Fn, FunctionArgList(),
207                SourceLocation());
208
209  for (unsigned i = 0; i != NumDecls; ++i)
210    Builder.CreateCall(Decls[i]);
211
212  FinishFunction();
213}
214
215void CodeGenFunction::GenerateCXXGlobalDtorFunc(llvm::Function *Fn,
216                const std::vector<std::pair<llvm::Constant*, llvm::Constant*> >
217                                                &DtorsAndObjects) {
218  StartFunction(GlobalDecl(), getContext().VoidTy, Fn, FunctionArgList(),
219                SourceLocation());
220
221  // Emit the dtors, in reverse order from construction.
222  for (unsigned i = 0, e = DtorsAndObjects.size(); i != e; ++i)
223    Builder.CreateCall(DtorsAndObjects[e - i - 1].first,
224                       DtorsAndObjects[e - i - 1].second);
225
226  FinishFunction();
227}
228
229static llvm::Constant *getGuardAcquireFn(CodeGenFunction &CGF) {
230  // int __cxa_guard_acquire(__int64_t *guard_object);
231
232  const llvm::Type *Int64PtrTy =
233    llvm::Type::getInt64PtrTy(CGF.getLLVMContext());
234
235  std::vector<const llvm::Type*> Args(1, Int64PtrTy);
236
237  const llvm::FunctionType *FTy =
238    llvm::FunctionType::get(CGF.ConvertType(CGF.getContext().IntTy),
239                            Args, /*isVarArg=*/false);
240
241  return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_guard_acquire");
242}
243
244static llvm::Constant *getGuardReleaseFn(CodeGenFunction &CGF) {
245  // void __cxa_guard_release(__int64_t *guard_object);
246
247  const llvm::Type *Int64PtrTy =
248    llvm::Type::getInt64PtrTy(CGF.getLLVMContext());
249
250  std::vector<const llvm::Type*> Args(1, Int64PtrTy);
251
252  const llvm::FunctionType *FTy =
253  llvm::FunctionType::get(llvm::Type::getVoidTy(CGF.getLLVMContext()),
254                          Args, /*isVarArg=*/false);
255
256  return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_guard_release");
257}
258
259static llvm::Constant *getGuardAbortFn(CodeGenFunction &CGF) {
260  // void __cxa_guard_abort(__int64_t *guard_object);
261
262  const llvm::Type *Int64PtrTy =
263    llvm::Type::getInt64PtrTy(CGF.getLLVMContext());
264
265  std::vector<const llvm::Type*> Args(1, Int64PtrTy);
266
267  const llvm::FunctionType *FTy =
268  llvm::FunctionType::get(llvm::Type::getVoidTy(CGF.getLLVMContext()),
269                          Args, /*isVarArg=*/false);
270
271  return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_guard_abort");
272}
273
274void
275CodeGenFunction::EmitStaticCXXBlockVarDeclInit(const VarDecl &D,
276                                               llvm::GlobalVariable *GV) {
277  bool ThreadsafeStatics = getContext().getLangOptions().ThreadsafeStatics;
278
279  llvm::SmallString<256> GuardVName;
280  CGM.getMangleContext().mangleGuardVariable(&D, GuardVName);
281
282  // Create the guard variable.
283  const llvm::Type *Int64Ty = llvm::Type::getInt64Ty(VMContext);
284  llvm::GlobalValue *GuardVariable =
285    new llvm::GlobalVariable(CGM.getModule(), Int64Ty,
286                             false, GV->getLinkage(),
287                             llvm::Constant::getNullValue(Int64Ty),
288                             GuardVName.str());
289
290  // Load the first byte of the guard variable.
291  const llvm::Type *PtrTy
292    = llvm::PointerType::get(llvm::Type::getInt8Ty(VMContext), 0);
293  llvm::Value *V =
294    Builder.CreateLoad(Builder.CreateBitCast(GuardVariable, PtrTy), "tmp");
295
296  llvm::BasicBlock *InitCheckBlock = createBasicBlock("init.check");
297  llvm::BasicBlock *EndBlock = createBasicBlock("init.end");
298
299  // Check if the first byte of the guard variable is zero.
300  Builder.CreateCondBr(Builder.CreateIsNull(V, "tobool"),
301                       InitCheckBlock, EndBlock);
302
303  EmitBlock(InitCheckBlock);
304
305  if (ThreadsafeStatics) {
306    // Call __cxa_guard_acquire.
307    V = Builder.CreateCall(getGuardAcquireFn(*this), GuardVariable);
308
309    llvm::BasicBlock *InitBlock = createBasicBlock("init");
310
311    Builder.CreateCondBr(Builder.CreateIsNotNull(V, "tobool"),
312                         InitBlock, EndBlock);
313
314    EmitBlock(InitBlock);
315
316    if (Exceptions) {
317      EHCleanupBlock Cleanup(*this);
318
319      // Call __cxa_guard_abort.
320      Builder.CreateCall(getGuardAbortFn(*this), GuardVariable);
321    }
322  }
323
324  if (D.getType()->isReferenceType()) {
325    QualType T = D.getType();
326    // We don't want to pass true for IsInitializer here, because a static
327    // reference to a temporary does not extend its lifetime.
328    RValue RV = EmitReferenceBindingToExpr(D.getInit(),
329                                           /*IsInitializer=*/false);
330    EmitStoreOfScalar(RV.getScalarVal(), GV, /*Volatile=*/false, T);
331
332  } else
333    EmitDeclInit(*this, D, GV);
334
335  if (ThreadsafeStatics) {
336    // Call __cxa_guard_release.
337    Builder.CreateCall(getGuardReleaseFn(*this), GuardVariable);
338  } else {
339    llvm::Value *One =
340      llvm::ConstantInt::get(llvm::Type::getInt8Ty(VMContext), 1);
341    Builder.CreateStore(One, Builder.CreateBitCast(GuardVariable, PtrTy));
342  }
343
344  EmitBlock(EndBlock);
345}
346