CGDeclCXX.cpp revision 221345 
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  std::vector<const llvm::Type *> Params;
121  Params.push_back(Int8PtrTy);
122
123  // Get the destructor function type
124  const llvm::Type *DtorFnTy =
125    llvm::FunctionType::get(llvm::Type::getVoidTy(getLLVMContext()),
126                            Params, false);
127  DtorFnTy = llvm::PointerType::getUnqual(DtorFnTy);
128
129  Params.clear();
130  Params.push_back(DtorFnTy);
131  Params.push_back(Int8PtrTy);
132  Params.push_back(Int8PtrTy);
133
134  // Get the __cxa_atexit function type
135  // extern "C" int __cxa_atexit ( void (*f)(void *), void *p, void *d );
136  const llvm::FunctionType *AtExitFnTy =
137    llvm::FunctionType::get(ConvertType(getContext().IntTy), Params, false);
138
139  llvm::Constant *AtExitFn = CGM.CreateRuntimeFunction(AtExitFnTy,
140                                                       "__cxa_atexit");
141  if (llvm::Function *Fn = dyn_cast<llvm::Function>(AtExitFn))
142    Fn->setDoesNotThrow();
143
144  llvm::Constant *Handle = CGM.CreateRuntimeVariable(Int8PtrTy,
145                                                     "__dso_handle");
146  llvm::Value *Args[3] = { llvm::ConstantExpr::getBitCast(DtorFn, DtorFnTy),
147                           llvm::ConstantExpr::getBitCast(DeclPtr, Int8PtrTy),
148                           llvm::ConstantExpr::getBitCast(Handle, Int8PtrTy) };
149  Builder.CreateCall(AtExitFn, &Args[0], llvm::array_endof(Args));
150}
151
152void CodeGenFunction::EmitCXXGuardedInit(const VarDecl &D,
153                                         llvm::GlobalVariable *DeclPtr) {
154  // If we've been asked to forbid guard variables, emit an error now.
155  // This diagnostic is hard-coded for Darwin's use case;  we can find
156  // better phrasing if someone else needs it.
157  if (CGM.getCodeGenOpts().ForbidGuardVariables)
158    CGM.Error(D.getLocation(),
159              "this initialization requires a guard variable, which "
160              "the kernel does not support");
161
162  CGM.getCXXABI().EmitGuardedInit(*this, D, DeclPtr);
163}
164
165static llvm::Function *
166CreateGlobalInitOrDestructFunction(CodeGenModule &CGM,
167                                   const llvm::FunctionType *FTy,
168                                   llvm::StringRef Name) {
169  llvm::Function *Fn =
170    llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage,
171                           Name, &CGM.getModule());
172  if (!CGM.getContext().getLangOptions().AppleKext) {
173    // Set the section if needed.
174    if (const char *Section =
175          CGM.getContext().Target.getStaticInitSectionSpecifier())
176      Fn->setSection(Section);
177  }
178
179  if (!CGM.getLangOptions().Exceptions)
180    Fn->setDoesNotThrow();
181
182  return Fn;
183}
184
185void
186CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D,
187                                            llvm::GlobalVariable *Addr) {
188  const llvm::FunctionType *FTy
189    = llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext),
190                              false);
191
192  // Create a variable initialization function.
193  llvm::Function *Fn =
194    CreateGlobalInitOrDestructFunction(*this, FTy, "__cxx_global_var_init");
195
196  CodeGenFunction(*this).GenerateCXXGlobalVarDeclInitFunc(Fn, D, Addr);
197
198  if (D->hasAttr<InitPriorityAttr>()) {
199    unsigned int order = D->getAttr<InitPriorityAttr>()->getPriority();
200    OrderGlobalInits Key(order, PrioritizedCXXGlobalInits.size());
201    PrioritizedCXXGlobalInits.push_back(std::make_pair(Key, Fn));
202    DelayedCXXInitPosition.erase(D);
203  }
204  else {
205    llvm::DenseMap<const Decl *, unsigned>::iterator I =
206      DelayedCXXInitPosition.find(D);
207    if (I == DelayedCXXInitPosition.end()) {
208      CXXGlobalInits.push_back(Fn);
209    } else {
210      assert(CXXGlobalInits[I->second] == 0);
211      CXXGlobalInits[I->second] = Fn;
212      DelayedCXXInitPosition.erase(I);
213    }
214  }
215}
216
217void
218CodeGenModule::EmitCXXGlobalInitFunc() {
219  while (!CXXGlobalInits.empty() && !CXXGlobalInits.back())
220    CXXGlobalInits.pop_back();
221
222  if (CXXGlobalInits.empty() && PrioritizedCXXGlobalInits.empty())
223    return;
224
225  const llvm::FunctionType *FTy
226    = llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext),
227                              false);
228
229  // Create our global initialization function.
230  llvm::Function *Fn =
231    CreateGlobalInitOrDestructFunction(*this, FTy, "_GLOBAL__I_a");
232
233  if (!PrioritizedCXXGlobalInits.empty()) {
234    llvm::SmallVector<llvm::Constant*, 8> LocalCXXGlobalInits;
235    llvm::array_pod_sort(PrioritizedCXXGlobalInits.begin(),
236                         PrioritizedCXXGlobalInits.end());
237    for (unsigned i = 0; i < PrioritizedCXXGlobalInits.size(); i++) {
238      llvm::Function *Fn = PrioritizedCXXGlobalInits[i].second;
239      LocalCXXGlobalInits.push_back(Fn);
240    }
241    LocalCXXGlobalInits.append(CXXGlobalInits.begin(), CXXGlobalInits.end());
242    CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn,
243                                                    &LocalCXXGlobalInits[0],
244                                                    LocalCXXGlobalInits.size());
245  }
246  else
247    CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn,
248                                                     &CXXGlobalInits[0],
249                                                     CXXGlobalInits.size());
250  AddGlobalCtor(Fn);
251}
252
253void CodeGenModule::EmitCXXGlobalDtorFunc() {
254  if (CXXGlobalDtors.empty())
255    return;
256
257  const llvm::FunctionType *FTy
258    = llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext),
259                              false);
260
261  // Create our global destructor function.
262  llvm::Function *Fn =
263    CreateGlobalInitOrDestructFunction(*this, FTy, "_GLOBAL__D_a");
264
265  CodeGenFunction(*this).GenerateCXXGlobalDtorFunc(Fn, CXXGlobalDtors);
266  AddGlobalDtor(Fn);
267}
268
269/// Emit the code necessary to initialize the given global variable.
270void CodeGenFunction::GenerateCXXGlobalVarDeclInitFunc(llvm::Function *Fn,
271                                                       const VarDecl *D,
272                                                 llvm::GlobalVariable *Addr) {
273  StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
274                getTypes().getNullaryFunctionInfo(),
275                FunctionArgList(), SourceLocation());
276
277  // Use guarded initialization if the global variable is weak due to
278  // being a class template's static data member.  These will always
279  // have weak_odr linkage.
280  if (Addr->getLinkage() == llvm::GlobalValue::WeakODRLinkage &&
281      D->isStaticDataMember() &&
282      D->getInstantiatedFromStaticDataMember()) {
283    EmitCXXGuardedInit(*D, Addr);
284  } else {
285    EmitCXXGlobalVarDeclInit(*D, Addr);
286  }
287
288  FinishFunction();
289}
290
291void CodeGenFunction::GenerateCXXGlobalInitFunc(llvm::Function *Fn,
292                                                llvm::Constant **Decls,
293                                                unsigned NumDecls) {
294  StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
295                getTypes().getNullaryFunctionInfo(),
296                FunctionArgList(), SourceLocation());
297
298  for (unsigned i = 0; i != NumDecls; ++i)
299    if (Decls[i])
300      Builder.CreateCall(Decls[i]);
301
302  FinishFunction();
303}
304
305void CodeGenFunction::GenerateCXXGlobalDtorFunc(llvm::Function *Fn,
306                  const std::vector<std::pair<llvm::WeakVH, llvm::Constant*> >
307                                                &DtorsAndObjects) {
308  StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
309                getTypes().getNullaryFunctionInfo(),
310                FunctionArgList(), SourceLocation());
311
312  // Emit the dtors, in reverse order from construction.
313  for (unsigned i = 0, e = DtorsAndObjects.size(); i != e; ++i) {
314    llvm::Value *Callee = DtorsAndObjects[e - i - 1].first;
315    llvm::CallInst *CI = Builder.CreateCall(Callee,
316                                            DtorsAndObjects[e - i - 1].second);
317    // Make sure the call and the callee agree on calling convention.
318    if (llvm::Function *F = dyn_cast<llvm::Function>(Callee))
319      CI->setCallingConv(F->getCallingConv());
320  }
321
322  FinishFunction();
323}
324
325/// GenerateCXXAggrDestructorHelper - Generates a helper function which when
326/// invoked, calls the default destructor on array elements in reverse order of
327/// construction.
328llvm::Function *
329CodeGenFunction::GenerateCXXAggrDestructorHelper(const CXXDestructorDecl *D,
330                                                 const ArrayType *Array,
331                                                 llvm::Value *This) {
332  FunctionArgList args;
333  ImplicitParamDecl dst(0, SourceLocation(), 0, getContext().VoidPtrTy);
334  args.push_back(&dst);
335
336  const CGFunctionInfo &FI =
337    CGM.getTypes().getFunctionInfo(getContext().VoidTy, args,
338                                   FunctionType::ExtInfo());
339  const llvm::FunctionType *FTy = CGM.getTypes().GetFunctionType(FI, false);
340  llvm::Function *Fn =
341    CreateGlobalInitOrDestructFunction(CGM, FTy, "__cxx_global_array_dtor");
342
343  StartFunction(GlobalDecl(), getContext().VoidTy, Fn, FI, args,
344                SourceLocation());
345
346  QualType BaseElementTy = getContext().getBaseElementType(Array);
347  const llvm::Type *BasePtr = ConvertType(BaseElementTy)->getPointerTo();
348  llvm::Value *BaseAddrPtr = Builder.CreateBitCast(This, BasePtr);
349
350  EmitCXXAggrDestructorCall(D, Array, BaseAddrPtr);
351
352  FinishFunction();
353
354  return Fn;
355}
356