CGDeclCXX.cpp revision 06057cef0bcd7804e80f3ce2bbe352178396c715 
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(Context);
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  if (Init->isLvalue(getContext()) == Expr::LV_Valid) {
97    RValue RV = EmitReferenceBindingToExpr(Init, /*IsInitializer=*/true);
98    EmitStoreOfScalar(RV.getScalarVal(), DeclPtr, false, T);
99    return;
100  }
101  ErrorUnsupported(Init,
102                   "global variable that binds reference to a non-lvalue");
103}
104
105void
106CodeGenFunction::EmitCXXGlobalDtorRegistration(llvm::Constant *DtorFn,
107                                               llvm::Constant *DeclPtr) {
108  // Generate a global destructor entry if not using __cxa_atexit.
109  if (!CGM.getCodeGenOpts().CXAAtExit) {
110    CGM.AddCXXDtorEntry(DtorFn, DeclPtr);
111    return;
112  }
113
114  const llvm::Type *Int8PtrTy =
115    llvm::Type::getInt8Ty(VMContext)->getPointerTo();
116
117  std::vector<const llvm::Type *> Params;
118  Params.push_back(Int8PtrTy);
119
120  // Get the destructor function type
121  const llvm::Type *DtorFnTy =
122    llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext), Params, false);
123  DtorFnTy = llvm::PointerType::getUnqual(DtorFnTy);
124
125  Params.clear();
126  Params.push_back(DtorFnTy);
127  Params.push_back(Int8PtrTy);
128  Params.push_back(Int8PtrTy);
129
130  // Get the __cxa_atexit function type
131  // extern "C" int __cxa_atexit ( void (*f)(void *), void *p, void *d );
132  const llvm::FunctionType *AtExitFnTy =
133    llvm::FunctionType::get(ConvertType(getContext().IntTy), Params, false);
134
135  llvm::Constant *AtExitFn = CGM.CreateRuntimeFunction(AtExitFnTy,
136                                                       "__cxa_atexit");
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
146static llvm::Function *
147CreateGlobalInitOrDestructFunction(CodeGenModule &CGM,
148                                   const llvm::FunctionType *FTy,
149                                   llvm::StringRef Name) {
150  llvm::Function *Fn =
151    llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage,
152                           Name, &CGM.getModule());
153
154  // Set the section if needed.
155  if (const char *Section =
156        CGM.getContext().Target.getStaticInitSectionSpecifier())
157    Fn->setSection(Section);
158
159  return Fn;
160}
161
162void
163CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D) {
164  const llvm::FunctionType *FTy
165    = llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext),
166                              false);
167
168  // Create a variable initialization function.
169  llvm::Function *Fn =
170    CreateGlobalInitOrDestructFunction(*this, FTy, "__cxx_global_var_init");
171
172  CodeGenFunction(*this).GenerateCXXGlobalVarDeclInitFunc(Fn, D);
173
174  CXXGlobalInits.push_back(Fn);
175}
176
177void
178CodeGenModule::EmitCXXGlobalInitFunc() {
179  if (CXXGlobalInits.empty())
180    return;
181
182  const llvm::FunctionType *FTy
183    = llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext),
184                              false);
185
186  // Create our global initialization function.
187  llvm::Function *Fn =
188    CreateGlobalInitOrDestructFunction(*this, FTy, "_GLOBAL__I_a");
189
190  CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn,
191                                                   &CXXGlobalInits[0],
192                                                   CXXGlobalInits.size());
193  AddGlobalCtor(Fn);
194}
195
196void CodeGenModule::AddCXXDtorEntry(llvm::Constant *DtorFn,
197                                    llvm::Constant *Object) {
198  CXXGlobalDtors.push_back(std::make_pair(DtorFn, Object));
199}
200
201void CodeGenModule::EmitCXXGlobalDtorFunc() {
202  if (CXXGlobalDtors.empty())
203    return;
204
205  const llvm::FunctionType *FTy
206    = llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext),
207                              false);
208
209  // Create our global destructor function.
210  llvm::Function *Fn =
211    CreateGlobalInitOrDestructFunction(*this, FTy, "_GLOBAL__D_a");
212
213  CodeGenFunction(*this).GenerateCXXGlobalDtorFunc(Fn, CXXGlobalDtors);
214  AddGlobalDtor(Fn);
215}
216
217void CodeGenFunction::GenerateCXXGlobalVarDeclInitFunc(llvm::Function *Fn,
218                                                       const VarDecl *D) {
219  StartFunction(GlobalDecl(), getContext().VoidTy, Fn, FunctionArgList(),
220                SourceLocation());
221
222  llvm::Constant *DeclPtr = CGM.GetAddrOfGlobalVar(D);
223  EmitCXXGlobalVarDeclInit(*D, DeclPtr);
224
225  FinishFunction();
226}
227
228void CodeGenFunction::GenerateCXXGlobalInitFunc(llvm::Function *Fn,
229                                                llvm::Constant **Decls,
230                                                unsigned NumDecls) {
231  StartFunction(GlobalDecl(), getContext().VoidTy, Fn, FunctionArgList(),
232                SourceLocation());
233
234  for (unsigned i = 0; i != NumDecls; ++i)
235    Builder.CreateCall(Decls[i]);
236
237  FinishFunction();
238}
239
240void CodeGenFunction::GenerateCXXGlobalDtorFunc(llvm::Function *Fn,
241                const std::vector<std::pair<llvm::Constant*, llvm::Constant*> >
242                                                &DtorsAndObjects) {
243  StartFunction(GlobalDecl(), getContext().VoidTy, Fn, FunctionArgList(),
244                SourceLocation());
245
246  // Emit the dtors, in reverse order from construction.
247  for (unsigned i = 0, e = DtorsAndObjects.size(); i != e; ++i) {
248    llvm::Constant *Callee = DtorsAndObjects[e - i - 1].first;
249    llvm::CallInst *CI = Builder.CreateCall(Callee,
250                                            DtorsAndObjects[e - i - 1].second);
251    // Make sure the call and the callee agree on calling convention.
252    if (llvm::Function *F = dyn_cast<llvm::Function>(Callee))
253      CI->setCallingConv(F->getCallingConv());
254  }
255
256  FinishFunction();
257}
258
259static llvm::Constant *getGuardAcquireFn(CodeGenFunction &CGF) {
260  // int __cxa_guard_acquire(__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(CGF.ConvertType(CGF.getContext().IntTy),
269                            Args, /*isVarArg=*/false);
270
271  return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_guard_acquire");
272}
273
274static llvm::Constant *getGuardReleaseFn(CodeGenFunction &CGF) {
275  // void __cxa_guard_release(__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(llvm::Type::getVoidTy(CGF.getLLVMContext()),
284                          Args, /*isVarArg=*/false);
285
286  return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_guard_release");
287}
288
289static llvm::Constant *getGuardAbortFn(CodeGenFunction &CGF) {
290  // void __cxa_guard_abort(__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_abort");
302}
303
304void
305CodeGenFunction::EmitStaticCXXBlockVarDeclInit(const VarDecl &D,
306                                               llvm::GlobalVariable *GV) {
307  // Bail out early if this initializer isn't reachable.
308  if (!Builder.GetInsertBlock()) return;
309
310  bool ThreadsafeStatics = getContext().getLangOptions().ThreadsafeStatics;
311
312  llvm::SmallString<256> GuardVName;
313  CGM.getMangleContext().mangleGuardVariable(&D, GuardVName);
314
315  // Create the guard variable.
316  const llvm::Type *Int64Ty = llvm::Type::getInt64Ty(VMContext);
317  llvm::GlobalValue *GuardVariable =
318    new llvm::GlobalVariable(CGM.getModule(), Int64Ty,
319                             false, GV->getLinkage(),
320                             llvm::Constant::getNullValue(Int64Ty),
321                             GuardVName.str());
322
323  // Load the first byte of the guard variable.
324  const llvm::Type *PtrTy
325    = llvm::PointerType::get(llvm::Type::getInt8Ty(VMContext), 0);
326  llvm::Value *V =
327    Builder.CreateLoad(Builder.CreateBitCast(GuardVariable, PtrTy), "tmp");
328
329  llvm::BasicBlock *InitCheckBlock = createBasicBlock("init.check");
330  llvm::BasicBlock *EndBlock = createBasicBlock("init.end");
331
332  // Check if the first byte of the guard variable is zero.
333  Builder.CreateCondBr(Builder.CreateIsNull(V, "tobool"),
334                       InitCheckBlock, EndBlock);
335
336  EmitBlock(InitCheckBlock);
337
338  // Variables used when coping with thread-safe statics and exceptions.
339  llvm::BasicBlock *SavedLandingPad = 0;
340  llvm::BasicBlock *LandingPad = 0;
341  if (ThreadsafeStatics) {
342    // Call __cxa_guard_acquire.
343    V = Builder.CreateCall(getGuardAcquireFn(*this), GuardVariable);
344
345    llvm::BasicBlock *InitBlock = createBasicBlock("init");
346
347    Builder.CreateCondBr(Builder.CreateIsNotNull(V, "tobool"),
348                         InitBlock, EndBlock);
349
350    if (Exceptions) {
351      SavedLandingPad = getInvokeDest();
352      LandingPad = createBasicBlock("guard.lpad");
353      setInvokeDest(LandingPad);
354    }
355
356    EmitBlock(InitBlock);
357  }
358
359  if (D.getType()->isReferenceType()) {
360    QualType T = D.getType();
361    // We don't want to pass true for IsInitializer here, because a static
362    // reference to a temporary does not extend its lifetime.
363    RValue RV = EmitReferenceBindingToExpr(D.getInit(),
364                                           /*IsInitializer=*/false);
365    EmitStoreOfScalar(RV.getScalarVal(), GV, /*Volatile=*/false, T);
366
367  } else
368    EmitDeclInit(*this, D, GV);
369
370  if (ThreadsafeStatics) {
371    // Call __cxa_guard_release.
372    Builder.CreateCall(getGuardReleaseFn(*this), GuardVariable);
373  } else {
374    llvm::Value *One =
375      llvm::ConstantInt::get(llvm::Type::getInt8Ty(VMContext), 1);
376    Builder.CreateStore(One, Builder.CreateBitCast(GuardVariable, PtrTy));
377  }
378
379  // Register the call to the destructor.
380  if (!D.getType()->isReferenceType())
381    EmitDeclDestroy(*this, D, GV);
382
383  if (ThreadsafeStatics && Exceptions) {
384    // If an exception is thrown during initialization, call __cxa_guard_abort
385    // along the exceptional edge.
386    EmitBranch(EndBlock);
387
388    // Construct the landing pad.
389    EmitBlock(LandingPad);
390
391    // Personality function and LLVM intrinsics.
392    llvm::Constant *Personality =
393      CGM.CreateRuntimeFunction(llvm::FunctionType::get(llvm::Type::getInt32Ty
394                                                        (VMContext),
395                                                        true),
396                                "__gxx_personality_v0");
397    Personality = llvm::ConstantExpr::getBitCast(Personality, PtrToInt8Ty);
398    llvm::Value *llvm_eh_exception =
399      CGM.getIntrinsic(llvm::Intrinsic::eh_exception);
400    llvm::Value *llvm_eh_selector =
401      CGM.getIntrinsic(llvm::Intrinsic::eh_selector);
402
403    // Exception object
404    llvm::Value *Exc = Builder.CreateCall(llvm_eh_exception, "exc");
405    llvm::Value *RethrowPtr = CreateTempAlloca(Exc->getType(), "_rethrow");
406
407    // Call the selector function.
408    const llvm::PointerType *PtrToInt8Ty
409      = llvm::PointerType::getUnqual(llvm::Type::getInt8Ty(VMContext));
410    llvm::Constant *Null = llvm::ConstantPointerNull::get(PtrToInt8Ty);
411    llvm::Value* SelectorArgs[3] = { Exc, Personality, Null };
412    Builder.CreateCall(llvm_eh_selector, SelectorArgs, SelectorArgs + 3,
413                           "selector");
414    Builder.CreateStore(Exc, RethrowPtr);
415
416    // Call __cxa_guard_abort along the exceptional edge.
417    Builder.CreateCall(getGuardAbortFn(*this), GuardVariable);
418
419    setInvokeDest(SavedLandingPad);
420
421    // Rethrow the current exception.
422    if (getInvokeDest()) {
423      llvm::BasicBlock *Cont = createBasicBlock("invoke.cont");
424      Builder.CreateInvoke(getUnwindResumeOrRethrowFn(), Cont,
425                           getInvokeDest(),
426                           Builder.CreateLoad(RethrowPtr));
427      EmitBlock(Cont);
428    } else
429      Builder.CreateCall(getUnwindResumeOrRethrowFn(),
430                         Builder.CreateLoad(RethrowPtr));
431
432    Builder.CreateUnreachable();
433  }
434
435  EmitBlock(EndBlock);
436}
437
438/// GenerateCXXAggrDestructorHelper - Generates a helper function which when
439/// invoked, calls the default destructor on array elements in reverse order of
440/// construction.
441llvm::Function *
442CodeGenFunction::GenerateCXXAggrDestructorHelper(const CXXDestructorDecl *D,
443                                                 const ArrayType *Array,
444                                                 llvm::Value *This) {
445  FunctionArgList Args;
446  ImplicitParamDecl *Dst =
447    ImplicitParamDecl::Create(getContext(), 0,
448                              SourceLocation(), 0,
449                              getContext().getPointerType(getContext().VoidTy));
450  Args.push_back(std::make_pair(Dst, Dst->getType()));
451
452  const CGFunctionInfo &FI =
453    CGM.getTypes().getFunctionInfo(getContext().VoidTy, Args,
454                                   FunctionType::ExtInfo());
455  const llvm::FunctionType *FTy = CGM.getTypes().GetFunctionType(FI, false);
456  llvm::Function *Fn =
457    CreateGlobalInitOrDestructFunction(CGM, FTy, "__cxx_global_array_dtor");
458
459  StartFunction(GlobalDecl(), getContext().VoidTy, Fn, Args, SourceLocation());
460
461  QualType BaseElementTy = getContext().getBaseElementType(Array);
462  const llvm::Type *BasePtr = ConvertType(BaseElementTy)->getPointerTo();
463  llvm::Value *BaseAddrPtr = Builder.CreateBitCast(This, BasePtr);
464
465  EmitCXXAggrDestructorCall(D, Array, BaseAddrPtr);
466
467  FinishFunction();
468
469  return Fn;
470}
471