CGDeclCXX.cpp revision 208954 
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"
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,
75                                                         Array,
76                                                         DeclPtr);
77    const llvm::Type *Int8PtrTy =
78    llvm::Type::getInt8PtrTy(CGM.getLLVMContext());
79    DeclPtr = llvm::Constant::getNullValue(Int8PtrTy);
80  } else
81    DtorFn = CGM.GetAddrOfCXXDestructor(Dtor, Dtor_Complete);
82
83  CGF.EmitCXXGlobalDtorRegistration(DtorFn, DeclPtr);
84}
85
86void CodeGenFunction::EmitCXXGlobalVarDeclInit(const VarDecl &D,
87                                               llvm::Constant *DeclPtr) {
88
89  const Expr *Init = D.getInit();
90  QualType T = D.getType();
91
92  if (!T->isReferenceType()) {
93    EmitDeclInit(*this, D, DeclPtr);
94    EmitDeclDestroy(*this, D, DeclPtr);
95    return;
96  }
97  if (Init->isLvalue(getContext()) == Expr::LV_Valid) {
98    RValue RV = EmitReferenceBindingToExpr(Init, /*IsInitializer=*/true);
99    EmitStoreOfScalar(RV.getScalarVal(), DeclPtr, false, T);
100    return;
101  }
102  ErrorUnsupported(Init,
103                   "global variable that binds reference to a non-lvalue");
104}
105
106void
107CodeGenFunction::EmitCXXGlobalDtorRegistration(llvm::Constant *DtorFn,
108                                               llvm::Constant *DeclPtr) {
109  // Generate a global destructor entry if not using __cxa_atexit.
110  if (!CGM.getCodeGenOpts().CXAAtExit) {
111    CGM.AddCXXDtorEntry(DtorFn, DeclPtr);
112    return;
113  }
114
115  const llvm::Type *Int8PtrTy =
116    llvm::Type::getInt8Ty(VMContext)->getPointerTo();
117
118  std::vector<const llvm::Type *> Params;
119  Params.push_back(Int8PtrTy);
120
121  // Get the destructor function type
122  const llvm::Type *DtorFnTy =
123    llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext), Params, false);
124  DtorFnTy = llvm::PointerType::getUnqual(DtorFnTy);
125
126  Params.clear();
127  Params.push_back(DtorFnTy);
128  Params.push_back(Int8PtrTy);
129  Params.push_back(Int8PtrTy);
130
131  // Get the __cxa_atexit function type
132  // extern "C" int __cxa_atexit ( void (*f)(void *), void *p, void *d );
133  const llvm::FunctionType *AtExitFnTy =
134    llvm::FunctionType::get(ConvertType(getContext().IntTy), Params, false);
135
136  llvm::Constant *AtExitFn = CGM.CreateRuntimeFunction(AtExitFnTy,
137                                                       "__cxa_atexit");
138
139  llvm::Constant *Handle = CGM.CreateRuntimeVariable(Int8PtrTy,
140                                                     "__dso_handle");
141  llvm::Value *Args[3] = { llvm::ConstantExpr::getBitCast(DtorFn, DtorFnTy),
142                           llvm::ConstantExpr::getBitCast(DeclPtr, Int8PtrTy),
143                           llvm::ConstantExpr::getBitCast(Handle, Int8PtrTy) };
144  Builder.CreateCall(AtExitFn, &Args[0], llvm::array_endof(Args));
145}
146
147void
148CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D) {
149  const llvm::FunctionType *FTy
150    = llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext),
151                              false);
152
153  // Create a variable initialization function.
154  llvm::Function *Fn =
155    llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage,
156                           "__cxx_global_var_init", &TheModule);
157
158  CodeGenFunction(*this).GenerateCXXGlobalVarDeclInitFunc(Fn, D);
159
160  CXXGlobalInits.push_back(Fn);
161}
162
163void
164CodeGenModule::EmitCXXGlobalInitFunc() {
165  if (CXXGlobalInits.empty())
166    return;
167
168  const llvm::FunctionType *FTy
169    = llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext),
170                              false);
171
172  // Create our global initialization function.
173  llvm::Function *Fn =
174    llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage,
175                           "_GLOBAL__I_a", &TheModule);
176
177  CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn,
178                                                   &CXXGlobalInits[0],
179                                                   CXXGlobalInits.size());
180  AddGlobalCtor(Fn);
181}
182
183void CodeGenModule::AddCXXDtorEntry(llvm::Constant *DtorFn,
184                                    llvm::Constant *Object) {
185  CXXGlobalDtors.push_back(std::make_pair(DtorFn, Object));
186}
187
188void CodeGenModule::EmitCXXGlobalDtorFunc() {
189  if (CXXGlobalDtors.empty())
190    return;
191
192  const llvm::FunctionType *FTy
193    = llvm::FunctionType::get(llvm::Type::getVoidTy(VMContext),
194                              false);
195
196  // Create our global destructor function.
197  llvm::Function *Fn =
198    llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage,
199                           "_GLOBAL__D_a", &TheModule);
200
201  CodeGenFunction(*this).GenerateCXXGlobalDtorFunc(Fn, CXXGlobalDtors);
202  AddGlobalDtor(Fn);
203}
204
205void CodeGenFunction::GenerateCXXGlobalVarDeclInitFunc(llvm::Function *Fn,
206                                                       const VarDecl *D) {
207  StartFunction(GlobalDecl(), getContext().VoidTy, Fn, FunctionArgList(),
208                SourceLocation());
209
210  llvm::Constant *DeclPtr = CGM.GetAddrOfGlobalVar(D);
211  EmitCXXGlobalVarDeclInit(*D, DeclPtr);
212
213  FinishFunction();
214}
215
216void CodeGenFunction::GenerateCXXGlobalInitFunc(llvm::Function *Fn,
217                                                llvm::Constant **Decls,
218                                                unsigned NumDecls) {
219  StartFunction(GlobalDecl(), getContext().VoidTy, Fn, FunctionArgList(),
220                SourceLocation());
221
222  for (unsigned i = 0; i != NumDecls; ++i)
223    Builder.CreateCall(Decls[i]);
224
225  FinishFunction();
226}
227
228void CodeGenFunction::GenerateCXXGlobalDtorFunc(llvm::Function *Fn,
229                const std::vector<std::pair<llvm::Constant*, llvm::Constant*> >
230                                                &DtorsAndObjects) {
231  StartFunction(GlobalDecl(), getContext().VoidTy, Fn, FunctionArgList(),
232                SourceLocation());
233
234  // Emit the dtors, in reverse order from construction.
235  for (unsigned i = 0, e = DtorsAndObjects.size(); i != e; ++i) {
236    llvm::Constant *Callee = DtorsAndObjects[e - i - 1].first;
237    llvm::CallInst *CI = Builder.CreateCall(Callee,
238                                            DtorsAndObjects[e - i - 1].second);
239    // Make sure the call and the callee agree on calling convention.
240    if (llvm::Function *F = dyn_cast<llvm::Function>(Callee))
241      CI->setCallingConv(F->getCallingConv());
242  }
243
244  FinishFunction();
245}
246
247static llvm::Constant *getGuardAcquireFn(CodeGenFunction &CGF) {
248  // int __cxa_guard_acquire(__int64_t *guard_object);
249
250  const llvm::Type *Int64PtrTy =
251    llvm::Type::getInt64PtrTy(CGF.getLLVMContext());
252
253  std::vector<const llvm::Type*> Args(1, Int64PtrTy);
254
255  const llvm::FunctionType *FTy =
256    llvm::FunctionType::get(CGF.ConvertType(CGF.getContext().IntTy),
257                            Args, /*isVarArg=*/false);
258
259  return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_guard_acquire");
260}
261
262static llvm::Constant *getGuardReleaseFn(CodeGenFunction &CGF) {
263  // void __cxa_guard_release(__int64_t *guard_object);
264
265  const llvm::Type *Int64PtrTy =
266    llvm::Type::getInt64PtrTy(CGF.getLLVMContext());
267
268  std::vector<const llvm::Type*> Args(1, Int64PtrTy);
269
270  const llvm::FunctionType *FTy =
271  llvm::FunctionType::get(llvm::Type::getVoidTy(CGF.getLLVMContext()),
272                          Args, /*isVarArg=*/false);
273
274  return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_guard_release");
275}
276
277static llvm::Constant *getGuardAbortFn(CodeGenFunction &CGF) {
278  // void __cxa_guard_abort(__int64_t *guard_object);
279
280  const llvm::Type *Int64PtrTy =
281    llvm::Type::getInt64PtrTy(CGF.getLLVMContext());
282
283  std::vector<const llvm::Type*> Args(1, Int64PtrTy);
284
285  const llvm::FunctionType *FTy =
286  llvm::FunctionType::get(llvm::Type::getVoidTy(CGF.getLLVMContext()),
287                          Args, /*isVarArg=*/false);
288
289  return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_guard_abort");
290}
291
292void
293CodeGenFunction::EmitStaticCXXBlockVarDeclInit(const VarDecl &D,
294                                               llvm::GlobalVariable *GV) {
295  // Bail out early if this initializer isn't reachable.
296  if (!Builder.GetInsertBlock()) return;
297
298  bool ThreadsafeStatics = getContext().getLangOptions().ThreadsafeStatics;
299
300  llvm::SmallString<256> GuardVName;
301  CGM.getMangleContext().mangleGuardVariable(&D, GuardVName);
302
303  // Create the guard variable.
304  const llvm::Type *Int64Ty = llvm::Type::getInt64Ty(VMContext);
305  llvm::GlobalValue *GuardVariable =
306    new llvm::GlobalVariable(CGM.getModule(), Int64Ty,
307                             false, GV->getLinkage(),
308                             llvm::Constant::getNullValue(Int64Ty),
309                             GuardVName.str());
310
311  // Load the first byte of the guard variable.
312  const llvm::Type *PtrTy
313    = llvm::PointerType::get(llvm::Type::getInt8Ty(VMContext), 0);
314  llvm::Value *V =
315    Builder.CreateLoad(Builder.CreateBitCast(GuardVariable, PtrTy), "tmp");
316
317  llvm::BasicBlock *InitCheckBlock = createBasicBlock("init.check");
318  llvm::BasicBlock *EndBlock = createBasicBlock("init.end");
319
320  // Check if the first byte of the guard variable is zero.
321  Builder.CreateCondBr(Builder.CreateIsNull(V, "tobool"),
322                       InitCheckBlock, EndBlock);
323
324  EmitBlock(InitCheckBlock);
325
326  // Variables used when coping with thread-safe statics and exceptions.
327  llvm::BasicBlock *SavedLandingPad = 0;
328  llvm::BasicBlock *LandingPad = 0;
329  if (ThreadsafeStatics) {
330    // Call __cxa_guard_acquire.
331    V = Builder.CreateCall(getGuardAcquireFn(*this), GuardVariable);
332
333    llvm::BasicBlock *InitBlock = createBasicBlock("init");
334
335    Builder.CreateCondBr(Builder.CreateIsNotNull(V, "tobool"),
336                         InitBlock, EndBlock);
337
338    if (Exceptions) {
339      SavedLandingPad = getInvokeDest();
340      LandingPad = createBasicBlock("guard.lpad");
341      setInvokeDest(LandingPad);
342    }
343
344    EmitBlock(InitBlock);
345  }
346
347  if (D.getType()->isReferenceType()) {
348    QualType T = D.getType();
349    // We don't want to pass true for IsInitializer here, because a static
350    // reference to a temporary does not extend its lifetime.
351    RValue RV = EmitReferenceBindingToExpr(D.getInit(),
352                                           /*IsInitializer=*/false);
353    EmitStoreOfScalar(RV.getScalarVal(), GV, /*Volatile=*/false, T);
354
355  } else
356    EmitDeclInit(*this, D, GV);
357
358  if (ThreadsafeStatics) {
359    // Call __cxa_guard_release.
360    Builder.CreateCall(getGuardReleaseFn(*this), GuardVariable);
361  } else {
362    llvm::Value *One =
363      llvm::ConstantInt::get(llvm::Type::getInt8Ty(VMContext), 1);
364    Builder.CreateStore(One, Builder.CreateBitCast(GuardVariable, PtrTy));
365  }
366
367  // Register the call to the destructor.
368  if (!D.getType()->isReferenceType())
369    EmitDeclDestroy(*this, D, GV);
370
371  if (ThreadsafeStatics && Exceptions) {
372    // If an exception is thrown during initialization, call __cxa_guard_abort
373    // along the exceptional edge.
374    EmitBranch(EndBlock);
375
376    // Construct the landing pad.
377    EmitBlock(LandingPad);
378
379    // Personality function and LLVM intrinsics.
380    llvm::Constant *Personality =
381      CGM.CreateRuntimeFunction(llvm::FunctionType::get(llvm::Type::getInt32Ty
382                                                        (VMContext),
383                                                        true),
384                                "__gxx_personality_v0");
385    Personality = llvm::ConstantExpr::getBitCast(Personality, PtrToInt8Ty);
386    llvm::Value *llvm_eh_exception =
387      CGM.getIntrinsic(llvm::Intrinsic::eh_exception);
388    llvm::Value *llvm_eh_selector =
389      CGM.getIntrinsic(llvm::Intrinsic::eh_selector);
390
391    // Exception object
392    llvm::Value *Exc = Builder.CreateCall(llvm_eh_exception, "exc");
393    llvm::Value *RethrowPtr = CreateTempAlloca(Exc->getType(), "_rethrow");
394
395    // Call the selector function.
396    const llvm::PointerType *PtrToInt8Ty
397      = llvm::PointerType::getUnqual(llvm::Type::getInt8Ty(VMContext));
398    llvm::Constant *Null = llvm::ConstantPointerNull::get(PtrToInt8Ty);
399    llvm::Value* SelectorArgs[3] = { Exc, Personality, Null };
400    Builder.CreateCall(llvm_eh_selector, SelectorArgs, SelectorArgs + 3,
401                           "selector");
402    Builder.CreateStore(Exc, RethrowPtr);
403
404    // Call __cxa_guard_abort along the exceptional edge.
405    Builder.CreateCall(getGuardAbortFn(*this), GuardVariable);
406
407    setInvokeDest(SavedLandingPad);
408
409    // Rethrow the current exception.
410    if (getInvokeDest()) {
411      llvm::BasicBlock *Cont = createBasicBlock("invoke.cont");
412      Builder.CreateInvoke(getUnwindResumeOrRethrowFn(), Cont,
413                           getInvokeDest(),
414                           Builder.CreateLoad(RethrowPtr));
415      EmitBlock(Cont);
416    } else
417      Builder.CreateCall(getUnwindResumeOrRethrowFn(),
418                         Builder.CreateLoad(RethrowPtr));
419
420    Builder.CreateUnreachable();
421  }
422
423  EmitBlock(EndBlock);
424}
425