CGDeclCXX.cpp revision 210299 
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/Frontend/CodeGenOptions.h"
16#include "llvm/Intrinsics.h"
17
18using namespace clang;
19using namespace CodeGen;
20
21static void EmitDeclInit(CodeGenFunction &CGF, const VarDecl &D,
22                         llvm::Constant *DeclPtr) {
23  assert(D.hasGlobalStorage() && "VarDecl must have global storage!");
24  assert(!D.getType()->isReferenceType() &&
25         "Should not call EmitDeclInit on a reference!");
26
27  ASTContext &Context = CGF.getContext();
28
29  const Expr *Init = D.getInit();
30  QualType T = D.getType();
31  bool isVolatile = Context.getCanonicalType(T).isVolatileQualified();
32
33  if (!CGF.hasAggregateLLVMType(T)) {
34    llvm::Value *V = CGF.EmitScalarExpr(Init);
35    CGF.EmitStoreOfScalar(V, DeclPtr, isVolatile, T);
36  } else if (T->isAnyComplexType()) {
37    CGF.EmitComplexExprIntoAddr(Init, DeclPtr, isVolatile);
38  } else {
39    CGF.EmitAggExpr(Init, DeclPtr, isVolatile);
40  }
41}
42
43static void EmitDeclDestroy(CodeGenFunction &CGF, const VarDecl &D,
44                            llvm::Constant *DeclPtr) {
45  CodeGenModule &CGM = CGF.CGM;
46  ASTContext &Context = CGF.getContext();
47
48  const Expr *Init = D.getInit();
49  QualType T = D.getType();
50  if (!CGF.hasAggregateLLVMType(T) || T->isAnyComplexType())
51    return;
52
53  // Avoid generating destructor(s) for initialized objects.
54  if (!isa<CXXConstructExpr>(Init))
55    return;
56
57  const ConstantArrayType *Array = Context.getAsConstantArrayType(T);
58  if (Array)
59    T = Context.getBaseElementType(Array);
60
61  const RecordType *RT = T->getAs<RecordType>();
62  if (!RT)
63    return;
64
65  CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
66  if (RD->hasTrivialDestructor())
67    return;
68
69  CXXDestructorDecl *Dtor = RD->getDestructor();
70
71  llvm::Constant *DtorFn;
72  if (Array) {
73    DtorFn =
74      CodeGenFunction(CGM).GenerateCXXAggrDestructorHelper(Dtor, Array,
75                                                           DeclPtr);
76    const llvm::Type *Int8PtrTy =
77      llvm::Type::getInt8PtrTy(CGM.getLLVMContext());
78    DeclPtr = llvm::Constant::getNullValue(Int8PtrTy);
79  } else
80    DtorFn = CGM.GetAddrOfCXXDestructor(Dtor, Dtor_Complete);
81
82  CGF.EmitCXXGlobalDtorRegistration(DtorFn, DeclPtr);
83}
84
85void CodeGenFunction::EmitCXXGlobalVarDeclInit(const VarDecl &D,
86                                               llvm::Constant *DeclPtr) {
87
88  const Expr *Init = D.getInit();
89  QualType T = D.getType();
90
91  if (!T->isReferenceType()) {
92    EmitDeclInit(*this, D, DeclPtr);
93    EmitDeclDestroy(*this, D, DeclPtr);
94    return;
95  }
96
97  RValue RV = EmitReferenceBindingToExpr(Init, &D);
98  EmitStoreOfScalar(RV.getScalarVal(), DeclPtr, false, T);
99}
100
101void
102CodeGenFunction::EmitCXXGlobalDtorRegistration(llvm::Constant *DtorFn,
103                                               llvm::Constant *DeclPtr) {
104  // Generate a global destructor entry if not using __cxa_atexit.
105  if (!CGM.getCodeGenOpts().CXAAtExit) {
106    CGM.AddCXXDtorEntry(DtorFn, DeclPtr);
107    return;
108  }
109
110  const llvm::Type *Int8PtrTy =
111    llvm::Type::getInt8Ty(VMContext)->getPointerTo();
112
113  std::vector<const llvm::Type *> Params;
114  Params.push_back(Int8PtrTy);
115
116  // Get the destructor function type
117  const llvm::Type *DtorFnTy =
118    llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext), Params, false);
119  DtorFnTy = llvm::PointerType::getUnqual(DtorFnTy);
120
121  Params.clear();
122  Params.push_back(DtorFnTy);
123  Params.push_back(Int8PtrTy);
124  Params.push_back(Int8PtrTy);
125
126  // Get the __cxa_atexit function type
127  // extern "C" int __cxa_atexit ( void (*f)(void *), void *p, void *d );
128  const llvm::FunctionType *AtExitFnTy =
129    llvm::FunctionType::get(ConvertType(getContext().IntTy), Params, false);
130
131  llvm::Constant *AtExitFn = CGM.CreateRuntimeFunction(AtExitFnTy,
132                                                       "__cxa_atexit");
133
134  llvm::Constant *Handle = CGM.CreateRuntimeVariable(Int8PtrTy,
135                                                     "__dso_handle");
136  llvm::Value *Args[3] = { llvm::ConstantExpr::getBitCast(DtorFn, DtorFnTy),
137                           llvm::ConstantExpr::getBitCast(DeclPtr, Int8PtrTy),
138                           llvm::ConstantExpr::getBitCast(Handle, Int8PtrTy) };
139  Builder.CreateCall(AtExitFn, &Args[0], llvm::array_endof(Args));
140}
141
142static llvm::Function *
143CreateGlobalInitOrDestructFunction(CodeGenModule &CGM,
144                                   const llvm::FunctionType *FTy,
145                                   llvm::StringRef Name) {
146  llvm::Function *Fn =
147    llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage,
148                           Name, &CGM.getModule());
149
150  // Set the section if needed.
151  if (const char *Section =
152        CGM.getContext().Target.getStaticInitSectionSpecifier())
153    Fn->setSection(Section);
154
155  if (!CGM.getLangOptions().Exceptions)
156    Fn->setDoesNotThrow();
157
158  return Fn;
159}
160
161void
162CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D) {
163  const llvm::FunctionType *FTy
164    = llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext),
165                              false);
166
167  // Create a variable initialization function.
168  llvm::Function *Fn =
169    CreateGlobalInitOrDestructFunction(*this, FTy, "__cxx_global_var_init");
170
171  CodeGenFunction(*this).GenerateCXXGlobalVarDeclInitFunc(Fn, D);
172
173  if (D->hasAttr<InitPriorityAttr>()) {
174    unsigned int order = D->getAttr<InitPriorityAttr>()->getPriority();
175    OrderGlobalInits Key(order, PrioritizedCXXGlobalInits.size());
176    PrioritizedCXXGlobalInits.push_back(std::make_pair(Key, Fn));
177  }
178  else
179    CXXGlobalInits.push_back(Fn);
180}
181
182void
183CodeGenModule::EmitCXXGlobalInitFunc() {
184  if (CXXGlobalInits.empty() && PrioritizedCXXGlobalInits.empty())
185    return;
186
187  const llvm::FunctionType *FTy
188    = llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext),
189                              false);
190
191  // Create our global initialization function.
192  llvm::Function *Fn =
193    CreateGlobalInitOrDestructFunction(*this, FTy, "_GLOBAL__I_a");
194
195  if (!PrioritizedCXXGlobalInits.empty()) {
196    llvm::SmallVector<llvm::Constant*, 8> LocalCXXGlobalInits;
197    llvm::array_pod_sort(PrioritizedCXXGlobalInits.begin(),
198                         PrioritizedCXXGlobalInits.end());
199    for (unsigned i = 0; i < PrioritizedCXXGlobalInits.size(); i++) {
200      llvm::Function *Fn = PrioritizedCXXGlobalInits[i].second;
201      LocalCXXGlobalInits.push_back(Fn);
202    }
203    for (unsigned i = 0; i < CXXGlobalInits.size(); i++)
204      LocalCXXGlobalInits.push_back(CXXGlobalInits[i]);
205    CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn,
206                                                    &LocalCXXGlobalInits[0],
207                                                    LocalCXXGlobalInits.size());
208  }
209  else
210    CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn,
211                                                     &CXXGlobalInits[0],
212                                                     CXXGlobalInits.size());
213  AddGlobalCtor(Fn);
214}
215
216void CodeGenModule::EmitCXXGlobalDtorFunc() {
217  if (CXXGlobalDtors.empty())
218    return;
219
220  const llvm::FunctionType *FTy
221    = llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext),
222                              false);
223
224  // Create our global destructor function.
225  llvm::Function *Fn =
226    CreateGlobalInitOrDestructFunction(*this, FTy, "_GLOBAL__D_a");
227
228  CodeGenFunction(*this).GenerateCXXGlobalDtorFunc(Fn, CXXGlobalDtors);
229  AddGlobalDtor(Fn);
230}
231
232void CodeGenFunction::GenerateCXXGlobalVarDeclInitFunc(llvm::Function *Fn,
233                                                       const VarDecl *D) {
234  StartFunction(GlobalDecl(), getContext().VoidTy, Fn, FunctionArgList(),
235                SourceLocation());
236
237  llvm::Constant *DeclPtr = CGM.GetAddrOfGlobalVar(D);
238  EmitCXXGlobalVarDeclInit(*D, DeclPtr);
239
240  FinishFunction();
241}
242
243void CodeGenFunction::GenerateCXXGlobalInitFunc(llvm::Function *Fn,
244                                                llvm::Constant **Decls,
245                                                unsigned NumDecls) {
246  StartFunction(GlobalDecl(), getContext().VoidTy, Fn, FunctionArgList(),
247                SourceLocation());
248
249  for (unsigned i = 0; i != NumDecls; ++i)
250    Builder.CreateCall(Decls[i]);
251
252  FinishFunction();
253}
254
255void CodeGenFunction::GenerateCXXGlobalDtorFunc(llvm::Function *Fn,
256                  const std::vector<std::pair<llvm::WeakVH, llvm::Constant*> >
257                                                &DtorsAndObjects) {
258  StartFunction(GlobalDecl(), getContext().VoidTy, Fn, FunctionArgList(),
259                SourceLocation());
260
261  // Emit the dtors, in reverse order from construction.
262  for (unsigned i = 0, e = DtorsAndObjects.size(); i != e; ++i) {
263    llvm::Value *Callee = DtorsAndObjects[e - i - 1].first;
264    llvm::CallInst *CI = Builder.CreateCall(Callee,
265                                            DtorsAndObjects[e - i - 1].second);
266    // Make sure the call and the callee agree on calling convention.
267    if (llvm::Function *F = dyn_cast<llvm::Function>(Callee))
268      CI->setCallingConv(F->getCallingConv());
269  }
270
271  FinishFunction();
272}
273
274static llvm::Constant *getGuardAcquireFn(CodeGenFunction &CGF) {
275  // int __cxa_guard_acquire(__int64_t *guard_object);
276
277  const llvm::Type *Int64PtrTy =
278    llvm::Type::getInt64PtrTy(CGF.getLLVMContext());
279
280  std::vector<const llvm::Type*> Args(1, Int64PtrTy);
281
282  const llvm::FunctionType *FTy =
283    llvm::FunctionType::get(CGF.ConvertType(CGF.getContext().IntTy),
284                            Args, /*isVarArg=*/false);
285
286  return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_guard_acquire");
287}
288
289static llvm::Constant *getGuardReleaseFn(CodeGenFunction &CGF) {
290  // void __cxa_guard_release(__int64_t *guard_object);
291
292  const llvm::Type *Int64PtrTy =
293    llvm::Type::getInt64PtrTy(CGF.getLLVMContext());
294
295  std::vector<const llvm::Type*> Args(1, Int64PtrTy);
296
297  const llvm::FunctionType *FTy =
298  llvm::FunctionType::get(llvm::Type::getVoidTy(CGF.getLLVMContext()),
299                          Args, /*isVarArg=*/false);
300
301  return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_guard_release");
302}
303
304static llvm::Constant *getGuardAbortFn(CodeGenFunction &CGF) {
305  // void __cxa_guard_abort(__int64_t *guard_object);
306
307  const llvm::Type *Int64PtrTy =
308    llvm::Type::getInt64PtrTy(CGF.getLLVMContext());
309
310  std::vector<const llvm::Type*> Args(1, Int64PtrTy);
311
312  const llvm::FunctionType *FTy =
313  llvm::FunctionType::get(llvm::Type::getVoidTy(CGF.getLLVMContext()),
314                          Args, /*isVarArg=*/false);
315
316  return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_guard_abort");
317}
318
319void
320CodeGenFunction::EmitStaticCXXBlockVarDeclInit(const VarDecl &D,
321                                               llvm::GlobalVariable *GV) {
322  // Bail out early if this initializer isn't reachable.
323  if (!Builder.GetInsertBlock()) return;
324
325  bool ThreadsafeStatics = getContext().getLangOptions().ThreadsafeStatics;
326
327  llvm::SmallString<256> GuardVName;
328  CGM.getMangleContext().mangleGuardVariable(&D, GuardVName);
329
330  // Create the guard variable.
331  llvm::GlobalValue *GuardVariable =
332    new llvm::GlobalVariable(CGM.getModule(), Int64Ty,
333                             false, GV->getLinkage(),
334                             llvm::Constant::getNullValue(Int64Ty),
335                             GuardVName.str());
336
337  // Load the first byte of the guard variable.
338  const llvm::Type *PtrTy
339    = llvm::PointerType::get(llvm::Type::getInt8Ty(VMContext), 0);
340  llvm::Value *V =
341    Builder.CreateLoad(Builder.CreateBitCast(GuardVariable, PtrTy), "tmp");
342
343  llvm::BasicBlock *InitCheckBlock = createBasicBlock("init.check");
344  llvm::BasicBlock *EndBlock = createBasicBlock("init.end");
345
346  // Check if the first byte of the guard variable is zero.
347  Builder.CreateCondBr(Builder.CreateIsNull(V, "tobool"),
348                       InitCheckBlock, EndBlock);
349
350  EmitBlock(InitCheckBlock);
351
352  // Variables used when coping with thread-safe statics and exceptions.
353  if (ThreadsafeStatics) {
354    // Call __cxa_guard_acquire.
355    V = Builder.CreateCall(getGuardAcquireFn(*this), GuardVariable);
356
357    llvm::BasicBlock *InitBlock = createBasicBlock("init");
358
359    Builder.CreateCondBr(Builder.CreateIsNotNull(V, "tobool"),
360                         InitBlock, EndBlock);
361
362    // Call __cxa_guard_abort along the exceptional edge.
363    if (Exceptions) {
364      CleanupBlock Cleanup(*this, EHCleanup);
365      Builder.CreateCall(getGuardAbortFn(*this), GuardVariable);
366    }
367
368    EmitBlock(InitBlock);
369  }
370
371  if (D.getType()->isReferenceType()) {
372    QualType T = D.getType();
373    RValue RV = EmitReferenceBindingToExpr(D.getInit(), &D);
374    EmitStoreOfScalar(RV.getScalarVal(), GV, /*Volatile=*/false, T);
375
376  } else
377    EmitDeclInit(*this, D, GV);
378
379  if (ThreadsafeStatics) {
380    // Call __cxa_guard_release.  This cannot throw.
381    Builder.CreateCall(getGuardReleaseFn(*this), GuardVariable);
382  } else {
383    llvm::Value *One =
384      llvm::ConstantInt::get(llvm::Type::getInt8Ty(VMContext), 1);
385    Builder.CreateStore(One, Builder.CreateBitCast(GuardVariable, PtrTy));
386  }
387
388  // Register the call to the destructor.
389  if (!D.getType()->isReferenceType())
390    EmitDeclDestroy(*this, D, GV);
391
392  EmitBlock(EndBlock);
393}
394
395/// GenerateCXXAggrDestructorHelper - Generates a helper function which when
396/// invoked, calls the default destructor on array elements in reverse order of
397/// construction.
398llvm::Function *
399CodeGenFunction::GenerateCXXAggrDestructorHelper(const CXXDestructorDecl *D,
400                                                 const ArrayType *Array,
401                                                 llvm::Value *This) {
402  FunctionArgList Args;
403  ImplicitParamDecl *Dst =
404    ImplicitParamDecl::Create(getContext(), 0,
405                              SourceLocation(), 0,
406                              getContext().getPointerType(getContext().VoidTy));
407  Args.push_back(std::make_pair(Dst, Dst->getType()));
408
409  const CGFunctionInfo &FI =
410    CGM.getTypes().getFunctionInfo(getContext().VoidTy, Args,
411                                   FunctionType::ExtInfo());
412  const llvm::FunctionType *FTy = CGM.getTypes().GetFunctionType(FI, false);
413  llvm::Function *Fn =
414    CreateGlobalInitOrDestructFunction(CGM, FTy, "__cxx_global_array_dtor");
415
416  StartFunction(GlobalDecl(), getContext().VoidTy, Fn, Args, SourceLocation());
417
418  QualType BaseElementTy = getContext().getBaseElementType(Array);
419  const llvm::Type *BasePtr = ConvertType(BaseElementTy)->getPointerTo();
420  llvm::Value *BaseAddrPtr = Builder.CreateBitCast(This, BasePtr);
421
422  EmitCXXAggrDestructorCall(D, Array, BaseAddrPtr);
423
424  FinishFunction();
425
426  return Fn;
427}
428