CGDeclCXX.cpp revision 223017 
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 "CGObjCRuntime.h"
16#include "CGCXXABI.h"
17#include "clang/Frontend/CodeGenOptions.h"
18#include "llvm/Intrinsics.h"
19
20using namespace clang;
21using namespace CodeGen;
22
23static void EmitDeclInit(CodeGenFunction &CGF, const VarDecl &D,
24                         llvm::Constant *DeclPtr) {
25  assert(D.hasGlobalStorage() && "VarDecl must have global storage!");
26  assert(!D.getType()->isReferenceType() &&
27         "Should not call EmitDeclInit on a reference!");
28
29  ASTContext &Context = CGF.getContext();
30
31  const Expr *Init = D.getInit();
32  QualType T = D.getType();
33  bool isVolatile = Context.getCanonicalType(T).isVolatileQualified();
34
35  unsigned Alignment = Context.getDeclAlign(&D).getQuantity();
36  if (!CGF.hasAggregateLLVMType(T)) {
37    llvm::Value *V = CGF.EmitScalarExpr(Init);
38    CodeGenModule &CGM = CGF.CGM;
39    Qualifiers::GC GCAttr = CGM.getContext().getObjCGCAttrKind(T);
40    if (GCAttr == Qualifiers::Strong)
41      CGM.getObjCRuntime().EmitObjCGlobalAssign(CGF, V, DeclPtr,
42                                                D.isThreadSpecified());
43    else if (GCAttr == Qualifiers::Weak)
44      CGM.getObjCRuntime().EmitObjCWeakAssign(CGF, V, DeclPtr);
45    else
46      CGF.EmitStoreOfScalar(V, DeclPtr, isVolatile, Alignment, T);
47  } else if (T->isAnyComplexType()) {
48    CGF.EmitComplexExprIntoAddr(Init, DeclPtr, isVolatile);
49  } else {
50    CGF.EmitAggExpr(Init, AggValueSlot::forAddr(DeclPtr, isVolatile, true));
51  }
52}
53
54/// Emit code to cause the destruction of the given variable with
55/// static storage duration.
56static void EmitDeclDestroy(CodeGenFunction &CGF, const VarDecl &D,
57                            llvm::Constant *DeclPtr) {
58  CodeGenModule &CGM = CGF.CGM;
59  ASTContext &Context = CGF.getContext();
60
61  QualType T = D.getType();
62
63  // Drill down past array types.
64  const ConstantArrayType *Array = Context.getAsConstantArrayType(T);
65  if (Array)
66    T = Context.getBaseElementType(Array);
67
68  /// If that's not a record, we're done.
69  /// FIXME:  __attribute__((cleanup)) ?
70  const RecordType *RT = T->getAs<RecordType>();
71  if (!RT)
72    return;
73
74  CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
75  if (RD->hasTrivialDestructor())
76    return;
77
78  CXXDestructorDecl *Dtor = RD->getDestructor();
79
80  llvm::Constant *DtorFn;
81  if (Array) {
82    DtorFn =
83      CodeGenFunction(CGM).GenerateCXXAggrDestructorHelper(Dtor, Array,
84                                                           DeclPtr);
85    const llvm::Type *Int8PtrTy =
86      llvm::Type::getInt8PtrTy(CGM.getLLVMContext());
87    DeclPtr = llvm::Constant::getNullValue(Int8PtrTy);
88  } else
89    DtorFn = CGM.GetAddrOfCXXDestructor(Dtor, Dtor_Complete);
90
91  CGF.EmitCXXGlobalDtorRegistration(DtorFn, DeclPtr);
92}
93
94void CodeGenFunction::EmitCXXGlobalVarDeclInit(const VarDecl &D,
95                                               llvm::Constant *DeclPtr) {
96
97  const Expr *Init = D.getInit();
98  QualType T = D.getType();
99
100  if (!T->isReferenceType()) {
101    EmitDeclInit(*this, D, DeclPtr);
102    EmitDeclDestroy(*this, D, DeclPtr);
103    return;
104  }
105
106  unsigned Alignment = getContext().getDeclAlign(&D).getQuantity();
107  RValue RV = EmitReferenceBindingToExpr(Init, &D);
108  EmitStoreOfScalar(RV.getScalarVal(), DeclPtr, false, Alignment, T);
109}
110
111void
112CodeGenFunction::EmitCXXGlobalDtorRegistration(llvm::Constant *DtorFn,
113                                               llvm::Constant *DeclPtr) {
114  // Generate a global destructor entry if not using __cxa_atexit.
115  if (!CGM.getCodeGenOpts().CXAAtExit) {
116    CGM.AddCXXDtorEntry(DtorFn, DeclPtr);
117    return;
118  }
119
120  // Get the destructor function type
121  const llvm::Type *DtorFnTy =
122    llvm::FunctionType::get(llvm::Type::getVoidTy(getLLVMContext()),
123                            Int8PtrTy, false);
124  DtorFnTy = llvm::PointerType::getUnqual(DtorFnTy);
125
126  const llvm::Type *Params[] = { DtorFnTy, Int8PtrTy, Int8PtrTy };
127
128  // Get the __cxa_atexit function type
129  // extern "C" int __cxa_atexit ( void (*f)(void *), void *p, void *d );
130  const llvm::FunctionType *AtExitFnTy =
131    llvm::FunctionType::get(ConvertType(getContext().IntTy), Params, false);
132
133  llvm::Constant *AtExitFn = CGM.CreateRuntimeFunction(AtExitFnTy,
134                                                       "__cxa_atexit");
135  if (llvm::Function *Fn = dyn_cast<llvm::Function>(AtExitFn))
136    Fn->setDoesNotThrow();
137
138  llvm::Constant *Handle = CGM.CreateRuntimeVariable(Int8PtrTy,
139                                                     "__dso_handle");
140  llvm::Value *Args[3] = { llvm::ConstantExpr::getBitCast(DtorFn, DtorFnTy),
141                           llvm::ConstantExpr::getBitCast(DeclPtr, Int8PtrTy),
142                           llvm::ConstantExpr::getBitCast(Handle, Int8PtrTy) };
143  Builder.CreateCall(AtExitFn, &Args[0], llvm::array_endof(Args));
144}
145
146void CodeGenFunction::EmitCXXGuardedInit(const VarDecl &D,
147                                         llvm::GlobalVariable *DeclPtr) {
148  // If we've been asked to forbid guard variables, emit an error now.
149  // This diagnostic is hard-coded for Darwin's use case;  we can find
150  // better phrasing if someone else needs it.
151  if (CGM.getCodeGenOpts().ForbidGuardVariables)
152    CGM.Error(D.getLocation(),
153              "this initialization requires a guard variable, which "
154              "the kernel does not support");
155
156  CGM.getCXXABI().EmitGuardedInit(*this, D, DeclPtr);
157}
158
159static llvm::Function *
160CreateGlobalInitOrDestructFunction(CodeGenModule &CGM,
161                                   const llvm::FunctionType *FTy,
162                                   llvm::StringRef Name) {
163  llvm::Function *Fn =
164    llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage,
165                           Name, &CGM.getModule());
166  if (!CGM.getContext().getLangOptions().AppleKext) {
167    // Set the section if needed.
168    if (const char *Section =
169          CGM.getContext().Target.getStaticInitSectionSpecifier())
170      Fn->setSection(Section);
171  }
172
173  if (!CGM.getLangOptions().Exceptions)
174    Fn->setDoesNotThrow();
175
176  return Fn;
177}
178
179void
180CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D,
181                                            llvm::GlobalVariable *Addr) {
182  const llvm::FunctionType *FTy
183    = llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext),
184                              false);
185
186  // Create a variable initialization function.
187  llvm::Function *Fn =
188    CreateGlobalInitOrDestructFunction(*this, FTy, "__cxx_global_var_init");
189
190  CodeGenFunction(*this).GenerateCXXGlobalVarDeclInitFunc(Fn, D, Addr);
191
192  if (D->hasAttr<InitPriorityAttr>()) {
193    unsigned int order = D->getAttr<InitPriorityAttr>()->getPriority();
194    OrderGlobalInits Key(order, PrioritizedCXXGlobalInits.size());
195    PrioritizedCXXGlobalInits.push_back(std::make_pair(Key, Fn));
196    DelayedCXXInitPosition.erase(D);
197  }
198  else {
199    llvm::DenseMap<const Decl *, unsigned>::iterator I =
200      DelayedCXXInitPosition.find(D);
201    if (I == DelayedCXXInitPosition.end()) {
202      CXXGlobalInits.push_back(Fn);
203    } else {
204      assert(CXXGlobalInits[I->second] == 0);
205      CXXGlobalInits[I->second] = Fn;
206      DelayedCXXInitPosition.erase(I);
207    }
208  }
209}
210
211void
212CodeGenModule::EmitCXXGlobalInitFunc() {
213  while (!CXXGlobalInits.empty() && !CXXGlobalInits.back())
214    CXXGlobalInits.pop_back();
215
216  if (CXXGlobalInits.empty() && PrioritizedCXXGlobalInits.empty())
217    return;
218
219  const llvm::FunctionType *FTy
220    = llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext),
221                              false);
222
223  // Create our global initialization function.
224  llvm::Function *Fn =
225    CreateGlobalInitOrDestructFunction(*this, FTy, "_GLOBAL__I_a");
226
227  if (!PrioritizedCXXGlobalInits.empty()) {
228    llvm::SmallVector<llvm::Constant*, 8> LocalCXXGlobalInits;
229    llvm::array_pod_sort(PrioritizedCXXGlobalInits.begin(),
230                         PrioritizedCXXGlobalInits.end());
231    for (unsigned i = 0; i < PrioritizedCXXGlobalInits.size(); i++) {
232      llvm::Function *Fn = PrioritizedCXXGlobalInits[i].second;
233      LocalCXXGlobalInits.push_back(Fn);
234    }
235    LocalCXXGlobalInits.append(CXXGlobalInits.begin(), CXXGlobalInits.end());
236    CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn,
237                                                    &LocalCXXGlobalInits[0],
238                                                    LocalCXXGlobalInits.size());
239  }
240  else
241    CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn,
242                                                     &CXXGlobalInits[0],
243                                                     CXXGlobalInits.size());
244  AddGlobalCtor(Fn);
245  CXXGlobalInits.clear();
246  PrioritizedCXXGlobalInits.clear();
247}
248
249void CodeGenModule::EmitCXXGlobalDtorFunc() {
250  if (CXXGlobalDtors.empty())
251    return;
252
253  const llvm::FunctionType *FTy
254    = llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext),
255                              false);
256
257  // Create our global destructor function.
258  llvm::Function *Fn =
259    CreateGlobalInitOrDestructFunction(*this, FTy, "_GLOBAL__D_a");
260
261  CodeGenFunction(*this).GenerateCXXGlobalDtorFunc(Fn, CXXGlobalDtors);
262  AddGlobalDtor(Fn);
263}
264
265/// Emit the code necessary to initialize the given global variable.
266void CodeGenFunction::GenerateCXXGlobalVarDeclInitFunc(llvm::Function *Fn,
267                                                       const VarDecl *D,
268                                                 llvm::GlobalVariable *Addr) {
269  StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
270                getTypes().getNullaryFunctionInfo(),
271                FunctionArgList(), SourceLocation());
272
273  // Use guarded initialization if the global variable is weak due to
274  // being a class template's static data member.  These will always
275  // have weak_odr linkage.
276  if (Addr->getLinkage() == llvm::GlobalValue::WeakODRLinkage &&
277      D->isStaticDataMember() &&
278      D->getInstantiatedFromStaticDataMember()) {
279    EmitCXXGuardedInit(*D, Addr);
280  } else {
281    EmitCXXGlobalVarDeclInit(*D, Addr);
282  }
283
284  FinishFunction();
285}
286
287void CodeGenFunction::GenerateCXXGlobalInitFunc(llvm::Function *Fn,
288                                                llvm::Constant **Decls,
289                                                unsigned NumDecls) {
290  StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
291                getTypes().getNullaryFunctionInfo(),
292                FunctionArgList(), SourceLocation());
293
294  for (unsigned i = 0; i != NumDecls; ++i)
295    if (Decls[i])
296      Builder.CreateCall(Decls[i]);
297
298  FinishFunction();
299}
300
301void CodeGenFunction::GenerateCXXGlobalDtorFunc(llvm::Function *Fn,
302                  const std::vector<std::pair<llvm::WeakVH, llvm::Constant*> >
303                                                &DtorsAndObjects) {
304  StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
305                getTypes().getNullaryFunctionInfo(),
306                FunctionArgList(), SourceLocation());
307
308  // Emit the dtors, in reverse order from construction.
309  for (unsigned i = 0, e = DtorsAndObjects.size(); i != e; ++i) {
310    llvm::Value *Callee = DtorsAndObjects[e - i - 1].first;
311    llvm::CallInst *CI = Builder.CreateCall(Callee,
312                                            DtorsAndObjects[e - i - 1].second);
313    // Make sure the call and the callee agree on calling convention.
314    if (llvm::Function *F = dyn_cast<llvm::Function>(Callee))
315      CI->setCallingConv(F->getCallingConv());
316  }
317
318  FinishFunction();
319}
320
321/// GenerateCXXAggrDestructorHelper - Generates a helper function which when
322/// invoked, calls the default destructor on array elements in reverse order of
323/// construction.
324llvm::Function *
325CodeGenFunction::GenerateCXXAggrDestructorHelper(const CXXDestructorDecl *D,
326                                                 const ArrayType *Array,
327                                                 llvm::Value *This) {
328  FunctionArgList args;
329  ImplicitParamDecl dst(0, SourceLocation(), 0, getContext().VoidPtrTy);
330  args.push_back(&dst);
331
332  const CGFunctionInfo &FI =
333    CGM.getTypes().getFunctionInfo(getContext().VoidTy, args,
334                                   FunctionType::ExtInfo());
335  const llvm::FunctionType *FTy = CGM.getTypes().GetFunctionType(FI, false);
336  llvm::Function *Fn =
337    CreateGlobalInitOrDestructFunction(CGM, FTy, "__cxx_global_array_dtor");
338
339  StartFunction(GlobalDecl(), getContext().VoidTy, Fn, FI, args,
340                SourceLocation());
341
342  QualType BaseElementTy = getContext().getBaseElementType(Array);
343  const llvm::Type *BasePtr = ConvertType(BaseElementTy)->getPointerTo();
344  llvm::Value *BaseAddrPtr = Builder.CreateBitCast(This, BasePtr);
345
346  EmitCXXAggrDestructorCall(D, Array, BaseAddrPtr);
347
348  FinishFunction();
349
350  return Fn;
351}
352