CGDeclCXX.cpp revision 243830 
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#include "llvm/ADT/StringExtras.h"
20
21using namespace clang;
22using namespace CodeGen;
23
24static void EmitDeclInit(CodeGenFunction &CGF, const VarDecl &D,
25                         llvm::Constant *DeclPtr) {
26  assert(D.hasGlobalStorage() && "VarDecl must have global storage!");
27  assert(!D.getType()->isReferenceType() &&
28         "Should not call EmitDeclInit on a reference!");
29
30  ASTContext &Context = CGF.getContext();
31
32  CharUnits alignment = Context.getDeclAlign(&D);
33  QualType type = D.getType();
34  LValue lv = CGF.MakeAddrLValue(DeclPtr, type, alignment);
35
36  const Expr *Init = D.getInit();
37  if (!CGF.hasAggregateLLVMType(type)) {
38    CodeGenModule &CGM = CGF.CGM;
39    if (lv.isObjCStrong())
40      CGM.getObjCRuntime().EmitObjCGlobalAssign(CGF, CGF.EmitScalarExpr(Init),
41                                                DeclPtr, D.isThreadSpecified());
42    else if (lv.isObjCWeak())
43      CGM.getObjCRuntime().EmitObjCWeakAssign(CGF, CGF.EmitScalarExpr(Init),
44                                              DeclPtr);
45    else
46      CGF.EmitScalarInit(Init, &D, lv, false);
47  } else if (type->isAnyComplexType()) {
48    CGF.EmitComplexExprIntoAddr(Init, DeclPtr, lv.isVolatile());
49  } else {
50    CGF.EmitAggExpr(Init, AggValueSlot::forLValue(lv,AggValueSlot::IsDestructed,
51                                          AggValueSlot::DoesNotNeedGCBarriers,
52                                                  AggValueSlot::IsNotAliased));
53  }
54}
55
56/// Emit code to cause the destruction of the given variable with
57/// static storage duration.
58static void EmitDeclDestroy(CodeGenFunction &CGF, const VarDecl &D,
59                            llvm::Constant *addr) {
60  CodeGenModule &CGM = CGF.CGM;
61
62  // FIXME:  __attribute__((cleanup)) ?
63
64  QualType type = D.getType();
65  QualType::DestructionKind dtorKind = type.isDestructedType();
66
67  switch (dtorKind) {
68  case QualType::DK_none:
69    return;
70
71  case QualType::DK_cxx_destructor:
72    break;
73
74  case QualType::DK_objc_strong_lifetime:
75  case QualType::DK_objc_weak_lifetime:
76    // We don't care about releasing objects during process teardown.
77    return;
78  }
79
80  llvm::Constant *function;
81  llvm::Constant *argument;
82
83  // Special-case non-array C++ destructors, where there's a function
84  // with the right signature that we can just call.
85  const CXXRecordDecl *record = 0;
86  if (dtorKind == QualType::DK_cxx_destructor &&
87      (record = type->getAsCXXRecordDecl())) {
88    assert(!record->hasTrivialDestructor());
89    CXXDestructorDecl *dtor = record->getDestructor();
90
91    function = CGM.GetAddrOfCXXDestructor(dtor, Dtor_Complete);
92    argument = addr;
93
94  // Otherwise, the standard logic requires a helper function.
95  } else {
96    function = CodeGenFunction(CGM).generateDestroyHelper(addr, type,
97                                                  CGF.getDestroyer(dtorKind),
98                                                  CGF.needsEHCleanup(dtorKind));
99    argument = llvm::Constant::getNullValue(CGF.Int8PtrTy);
100  }
101
102  CGM.getCXXABI().registerGlobalDtor(CGF, function, argument);
103}
104
105/// Emit code to cause the variable at the given address to be considered as
106/// constant from this point onwards.
107static void EmitDeclInvariant(CodeGenFunction &CGF, const VarDecl &D,
108                              llvm::Constant *Addr) {
109  // Don't emit the intrinsic if we're not optimizing.
110  if (!CGF.CGM.getCodeGenOpts().OptimizationLevel)
111    return;
112
113  // Grab the llvm.invariant.start intrinsic.
114  llvm::Intrinsic::ID InvStartID = llvm::Intrinsic::invariant_start;
115  llvm::Constant *InvariantStart = CGF.CGM.getIntrinsic(InvStartID);
116
117  // Emit a call with the size in bytes of the object.
118  CharUnits WidthChars = CGF.getContext().getTypeSizeInChars(D.getType());
119  uint64_t Width = WidthChars.getQuantity();
120  llvm::Value *Args[2] = { llvm::ConstantInt::getSigned(CGF.Int64Ty, Width),
121                           llvm::ConstantExpr::getBitCast(Addr, CGF.Int8PtrTy)};
122  CGF.Builder.CreateCall(InvariantStart, Args);
123}
124
125void CodeGenFunction::EmitCXXGlobalVarDeclInit(const VarDecl &D,
126                                               llvm::Constant *DeclPtr,
127                                               bool PerformInit) {
128
129  const Expr *Init = D.getInit();
130  QualType T = D.getType();
131
132  if (!T->isReferenceType()) {
133    if (PerformInit)
134      EmitDeclInit(*this, D, DeclPtr);
135    if (CGM.isTypeConstant(D.getType(), true))
136      EmitDeclInvariant(*this, D, DeclPtr);
137    else
138      EmitDeclDestroy(*this, D, DeclPtr);
139    return;
140  }
141
142  assert(PerformInit && "cannot have constant initializer which needs "
143         "destruction for reference");
144  unsigned Alignment = getContext().getDeclAlign(&D).getQuantity();
145  RValue RV = EmitReferenceBindingToExpr(Init, &D);
146  EmitStoreOfScalar(RV.getScalarVal(), DeclPtr, false, Alignment, T);
147}
148
149static llvm::Function *
150CreateGlobalInitOrDestructFunction(CodeGenModule &CGM,
151                                   llvm::FunctionType *ty,
152                                   const Twine &name);
153
154/// Create a stub function, suitable for being passed to atexit,
155/// which passes the given address to the given destructor function.
156static llvm::Constant *createAtExitStub(CodeGenModule &CGM,
157                                        llvm::Constant *dtor,
158                                        llvm::Constant *addr) {
159  // Get the destructor function type, void(*)(void).
160  llvm::FunctionType *ty = llvm::FunctionType::get(CGM.VoidTy, false);
161  llvm::Function *fn =
162    CreateGlobalInitOrDestructFunction(CGM, ty,
163                                       Twine("__dtor_", addr->getName()));
164
165  CodeGenFunction CGF(CGM);
166
167  // Initialize debug info if needed.
168  CGF.maybeInitializeDebugInfo();
169
170  CGF.StartFunction(GlobalDecl(), CGM.getContext().VoidTy, fn,
171                    CGM.getTypes().arrangeNullaryFunction(),
172                    FunctionArgList(), SourceLocation());
173
174  llvm::CallInst *call = CGF.Builder.CreateCall(dtor, addr);
175
176 // Make sure the call and the callee agree on calling convention.
177  if (llvm::Function *dtorFn =
178        dyn_cast<llvm::Function>(dtor->stripPointerCasts()))
179    call->setCallingConv(dtorFn->getCallingConv());
180
181  CGF.FinishFunction();
182
183  return fn;
184}
185
186/// Register a global destructor using the C atexit runtime function.
187void CodeGenFunction::registerGlobalDtorWithAtExit(llvm::Constant *dtor,
188                                                   llvm::Constant *addr) {
189  // Create a function which calls the destructor.
190  llvm::Constant *dtorStub = createAtExitStub(CGM, dtor, addr);
191
192  // extern "C" int atexit(void (*f)(void));
193  llvm::FunctionType *atexitTy =
194    llvm::FunctionType::get(IntTy, dtorStub->getType(), false);
195
196  llvm::Constant *atexit =
197    CGM.CreateRuntimeFunction(atexitTy, "atexit");
198  if (llvm::Function *atexitFn = dyn_cast<llvm::Function>(atexit))
199    atexitFn->setDoesNotThrow();
200
201  Builder.CreateCall(atexit, dtorStub)->setDoesNotThrow();
202}
203
204void CodeGenFunction::EmitCXXGuardedInit(const VarDecl &D,
205                                         llvm::GlobalVariable *DeclPtr,
206                                         bool PerformInit) {
207  // If we've been asked to forbid guard variables, emit an error now.
208  // This diagnostic is hard-coded for Darwin's use case;  we can find
209  // better phrasing if someone else needs it.
210  if (CGM.getCodeGenOpts().ForbidGuardVariables)
211    CGM.Error(D.getLocation(),
212              "this initialization requires a guard variable, which "
213              "the kernel does not support");
214
215  CGM.getCXXABI().EmitGuardedInit(*this, D, DeclPtr, PerformInit);
216}
217
218static llvm::Function *
219CreateGlobalInitOrDestructFunction(CodeGenModule &CGM,
220                                   llvm::FunctionType *FTy,
221                                   const Twine &Name) {
222  llvm::Function *Fn =
223    llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage,
224                           Name, &CGM.getModule());
225  if (!CGM.getLangOpts().AppleKext) {
226    // Set the section if needed.
227    if (const char *Section =
228          CGM.getContext().getTargetInfo().getStaticInitSectionSpecifier())
229      Fn->setSection(Section);
230  }
231
232  if (!CGM.getLangOpts().Exceptions)
233    Fn->setDoesNotThrow();
234
235  if (CGM.getLangOpts().SanitizeAddress)
236    Fn->addFnAttr(llvm::Attributes::AddressSafety);
237
238  return Fn;
239}
240
241void
242CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D,
243                                            llvm::GlobalVariable *Addr,
244                                            bool PerformInit) {
245  llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
246
247  // Create a variable initialization function.
248  llvm::Function *Fn =
249    CreateGlobalInitOrDestructFunction(*this, FTy, "__cxx_global_var_init");
250
251  CodeGenFunction(*this).GenerateCXXGlobalVarDeclInitFunc(Fn, D, Addr,
252                                                          PerformInit);
253
254  if (D->hasAttr<InitPriorityAttr>()) {
255    unsigned int order = D->getAttr<InitPriorityAttr>()->getPriority();
256    OrderGlobalInits Key(order, PrioritizedCXXGlobalInits.size());
257    PrioritizedCXXGlobalInits.push_back(std::make_pair(Key, Fn));
258    DelayedCXXInitPosition.erase(D);
259  }  else {
260    llvm::DenseMap<const Decl *, unsigned>::iterator I =
261      DelayedCXXInitPosition.find(D);
262    if (I == DelayedCXXInitPosition.end()) {
263      CXXGlobalInits.push_back(Fn);
264    } else {
265      assert(CXXGlobalInits[I->second] == 0);
266      CXXGlobalInits[I->second] = Fn;
267      DelayedCXXInitPosition.erase(I);
268    }
269  }
270}
271
272void
273CodeGenModule::EmitCXXGlobalInitFunc() {
274  while (!CXXGlobalInits.empty() && !CXXGlobalInits.back())
275    CXXGlobalInits.pop_back();
276
277  if (CXXGlobalInits.empty() && PrioritizedCXXGlobalInits.empty())
278    return;
279
280  llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
281
282
283  // Create our global initialization function.
284  if (!PrioritizedCXXGlobalInits.empty()) {
285    SmallVector<llvm::Constant*, 8> LocalCXXGlobalInits;
286    llvm::array_pod_sort(PrioritizedCXXGlobalInits.begin(),
287                         PrioritizedCXXGlobalInits.end());
288    // Iterate over "chunks" of ctors with same priority and emit each chunk
289    // into separate function. Note - everything is sorted first by priority,
290    // second - by lex order, so we emit ctor functions in proper order.
291    for (SmallVectorImpl<GlobalInitData >::iterator
292           I = PrioritizedCXXGlobalInits.begin(),
293           E = PrioritizedCXXGlobalInits.end(); I != E; ) {
294      SmallVectorImpl<GlobalInitData >::iterator
295        PrioE = std::upper_bound(I + 1, E, *I, GlobalInitPriorityCmp());
296
297      LocalCXXGlobalInits.clear();
298      unsigned Priority = I->first.priority;
299      // Compute the function suffix from priority. Prepend with zeroes to make
300      // sure the function names are also ordered as priorities.
301      std::string PrioritySuffix = llvm::utostr(Priority);
302      // Priority is always <= 65535 (enforced by sema)..
303      PrioritySuffix = std::string(6-PrioritySuffix.size(), '0')+PrioritySuffix;
304      llvm::Function *Fn =
305        CreateGlobalInitOrDestructFunction(*this, FTy,
306                                           "_GLOBAL__I_" + PrioritySuffix);
307
308      for (; I < PrioE; ++I)
309        LocalCXXGlobalInits.push_back(I->second);
310
311      CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn,
312                                                    &LocalCXXGlobalInits[0],
313                                                    LocalCXXGlobalInits.size());
314      AddGlobalCtor(Fn, Priority);
315    }
316  }
317
318  llvm::Function *Fn =
319    CreateGlobalInitOrDestructFunction(*this, FTy, "_GLOBAL__I_a");
320
321  CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn,
322                                                   &CXXGlobalInits[0],
323                                                   CXXGlobalInits.size());
324  AddGlobalCtor(Fn);
325
326  CXXGlobalInits.clear();
327  PrioritizedCXXGlobalInits.clear();
328}
329
330void CodeGenModule::EmitCXXGlobalDtorFunc() {
331  if (CXXGlobalDtors.empty())
332    return;
333
334  llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
335
336  // Create our global destructor function.
337  llvm::Function *Fn =
338    CreateGlobalInitOrDestructFunction(*this, FTy, "_GLOBAL__D_a");
339
340  CodeGenFunction(*this).GenerateCXXGlobalDtorsFunc(Fn, CXXGlobalDtors);
341  AddGlobalDtor(Fn);
342}
343
344/// Emit the code necessary to initialize the given global variable.
345void CodeGenFunction::GenerateCXXGlobalVarDeclInitFunc(llvm::Function *Fn,
346                                                       const VarDecl *D,
347                                                 llvm::GlobalVariable *Addr,
348                                                       bool PerformInit) {
349  // Check if we need to emit debug info for variable initializer.
350  if (!D->hasAttr<NoDebugAttr>())
351    maybeInitializeDebugInfo();
352
353  StartFunction(GlobalDecl(D), getContext().VoidTy, Fn,
354                getTypes().arrangeNullaryFunction(),
355                FunctionArgList(), D->getInit()->getExprLoc());
356
357  // Use guarded initialization if the global variable is weak. This
358  // occurs for, e.g., instantiated static data members and
359  // definitions explicitly marked weak.
360  if (Addr->getLinkage() == llvm::GlobalValue::WeakODRLinkage ||
361      Addr->getLinkage() == llvm::GlobalValue::WeakAnyLinkage) {
362    EmitCXXGuardedInit(*D, Addr, PerformInit);
363  } else {
364    EmitCXXGlobalVarDeclInit(*D, Addr, PerformInit);
365  }
366
367  FinishFunction();
368}
369
370void CodeGenFunction::GenerateCXXGlobalInitFunc(llvm::Function *Fn,
371                                                llvm::Constant **Decls,
372                                                unsigned NumDecls) {
373  // Initialize debug info if needed.
374  maybeInitializeDebugInfo();
375
376  StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
377                getTypes().arrangeNullaryFunction(),
378                FunctionArgList(), SourceLocation());
379
380  RunCleanupsScope Scope(*this);
381
382  // When building in Objective-C++ ARC mode, create an autorelease pool
383  // around the global initializers.
384  if (getLangOpts().ObjCAutoRefCount && getLangOpts().CPlusPlus) {
385    llvm::Value *token = EmitObjCAutoreleasePoolPush();
386    EmitObjCAutoreleasePoolCleanup(token);
387  }
388
389  for (unsigned i = 0; i != NumDecls; ++i)
390    if (Decls[i])
391      Builder.CreateCall(Decls[i]);
392
393  Scope.ForceCleanup();
394
395  FinishFunction();
396}
397
398void CodeGenFunction::GenerateCXXGlobalDtorsFunc(llvm::Function *Fn,
399                  const std::vector<std::pair<llvm::WeakVH, llvm::Constant*> >
400                                                &DtorsAndObjects) {
401  // Initialize debug info if needed.
402  maybeInitializeDebugInfo();
403
404  StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
405                getTypes().arrangeNullaryFunction(),
406                FunctionArgList(), SourceLocation());
407
408  // Emit the dtors, in reverse order from construction.
409  for (unsigned i = 0, e = DtorsAndObjects.size(); i != e; ++i) {
410    llvm::Value *Callee = DtorsAndObjects[e - i - 1].first;
411    llvm::CallInst *CI = Builder.CreateCall(Callee,
412                                            DtorsAndObjects[e - i - 1].second);
413    // Make sure the call and the callee agree on calling convention.
414    if (llvm::Function *F = dyn_cast<llvm::Function>(Callee))
415      CI->setCallingConv(F->getCallingConv());
416  }
417
418  FinishFunction();
419}
420
421/// generateDestroyHelper - Generates a helper function which, when
422/// invoked, destroys the given object.
423llvm::Function *
424CodeGenFunction::generateDestroyHelper(llvm::Constant *addr,
425                                       QualType type,
426                                       Destroyer *destroyer,
427                                       bool useEHCleanupForArray) {
428  FunctionArgList args;
429  ImplicitParamDecl dst(0, SourceLocation(), 0, getContext().VoidPtrTy);
430  args.push_back(&dst);
431
432  const CGFunctionInfo &FI =
433    CGM.getTypes().arrangeFunctionDeclaration(getContext().VoidTy, args,
434                                              FunctionType::ExtInfo(),
435                                              /*variadic*/ false);
436  llvm::FunctionType *FTy = CGM.getTypes().GetFunctionType(FI);
437  llvm::Function *fn =
438    CreateGlobalInitOrDestructFunction(CGM, FTy, "__cxx_global_array_dtor");
439
440  // Initialize debug info if needed.
441  maybeInitializeDebugInfo();
442
443  StartFunction(GlobalDecl(), getContext().VoidTy, fn, FI, args,
444                SourceLocation());
445
446  emitDestroy(addr, type, destroyer, useEHCleanupForArray);
447
448  FinishFunction();
449
450  return fn;
451}
452