CGDeclCXX.cpp revision 249423 
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 "CGCXXABI.h"
16#include "CGObjCRuntime.h"
17#include "clang/Frontend/CodeGenOptions.h"
18#include "llvm/ADT/StringExtras.h"
19#include "llvm/IR/Intrinsics.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  switch (CGF.getEvaluationKind(type)) {
38  case TEK_Scalar: {
39    CodeGenModule &CGM = CGF.CGM;
40    if (lv.isObjCStrong())
41      CGM.getObjCRuntime().EmitObjCGlobalAssign(CGF, CGF.EmitScalarExpr(Init),
42                                                DeclPtr, D.isThreadSpecified());
43    else if (lv.isObjCWeak())
44      CGM.getObjCRuntime().EmitObjCWeakAssign(CGF, CGF.EmitScalarExpr(Init),
45                                              DeclPtr);
46    else
47      CGF.EmitScalarInit(Init, &D, lv, false);
48    return;
49  }
50  case TEK_Complex:
51    CGF.EmitComplexExprIntoLValue(Init, lv, /*isInit*/ true);
52    return;
53  case TEK_Aggregate:
54    CGF.EmitAggExpr(Init, AggValueSlot::forLValue(lv,AggValueSlot::IsDestructed,
55                                          AggValueSlot::DoesNotNeedGCBarriers,
56                                                  AggValueSlot::IsNotAliased));
57    return;
58  }
59  llvm_unreachable("bad evaluation kind");
60}
61
62/// Emit code to cause the destruction of the given variable with
63/// static storage duration.
64static void EmitDeclDestroy(CodeGenFunction &CGF, const VarDecl &D,
65                            llvm::Constant *addr) {
66  CodeGenModule &CGM = CGF.CGM;
67
68  // FIXME:  __attribute__((cleanup)) ?
69
70  QualType type = D.getType();
71  QualType::DestructionKind dtorKind = type.isDestructedType();
72
73  switch (dtorKind) {
74  case QualType::DK_none:
75    return;
76
77  case QualType::DK_cxx_destructor:
78    break;
79
80  case QualType::DK_objc_strong_lifetime:
81  case QualType::DK_objc_weak_lifetime:
82    // We don't care about releasing objects during process teardown.
83    return;
84  }
85
86  llvm::Constant *function;
87  llvm::Constant *argument;
88
89  // Special-case non-array C++ destructors, where there's a function
90  // with the right signature that we can just call.
91  const CXXRecordDecl *record = 0;
92  if (dtorKind == QualType::DK_cxx_destructor &&
93      (record = type->getAsCXXRecordDecl())) {
94    assert(!record->hasTrivialDestructor());
95    CXXDestructorDecl *dtor = record->getDestructor();
96
97    function = CGM.GetAddrOfCXXDestructor(dtor, Dtor_Complete);
98    argument = addr;
99
100  // Otherwise, the standard logic requires a helper function.
101  } else {
102    function = CodeGenFunction(CGM).generateDestroyHelper(addr, type,
103                                                  CGF.getDestroyer(dtorKind),
104                                                  CGF.needsEHCleanup(dtorKind));
105    argument = llvm::Constant::getNullValue(CGF.Int8PtrTy);
106  }
107
108  CGM.getCXXABI().registerGlobalDtor(CGF, function, argument);
109}
110
111/// Emit code to cause the variable at the given address to be considered as
112/// constant from this point onwards.
113static void EmitDeclInvariant(CodeGenFunction &CGF, const VarDecl &D,
114                              llvm::Constant *Addr) {
115  // Don't emit the intrinsic if we're not optimizing.
116  if (!CGF.CGM.getCodeGenOpts().OptimizationLevel)
117    return;
118
119  // Grab the llvm.invariant.start intrinsic.
120  llvm::Intrinsic::ID InvStartID = llvm::Intrinsic::invariant_start;
121  llvm::Constant *InvariantStart = CGF.CGM.getIntrinsic(InvStartID);
122
123  // Emit a call with the size in bytes of the object.
124  CharUnits WidthChars = CGF.getContext().getTypeSizeInChars(D.getType());
125  uint64_t Width = WidthChars.getQuantity();
126  llvm::Value *Args[2] = { llvm::ConstantInt::getSigned(CGF.Int64Ty, Width),
127                           llvm::ConstantExpr::getBitCast(Addr, CGF.Int8PtrTy)};
128  CGF.Builder.CreateCall(InvariantStart, Args);
129}
130
131void CodeGenFunction::EmitCXXGlobalVarDeclInit(const VarDecl &D,
132                                               llvm::Constant *DeclPtr,
133                                               bool PerformInit) {
134
135  const Expr *Init = D.getInit();
136  QualType T = D.getType();
137
138  if (!T->isReferenceType()) {
139    if (PerformInit)
140      EmitDeclInit(*this, D, DeclPtr);
141    if (CGM.isTypeConstant(D.getType(), true))
142      EmitDeclInvariant(*this, D, DeclPtr);
143    else
144      EmitDeclDestroy(*this, D, DeclPtr);
145    return;
146  }
147
148  assert(PerformInit && "cannot have constant initializer which needs "
149         "destruction for reference");
150  unsigned Alignment = getContext().getDeclAlign(&D).getQuantity();
151  RValue RV = EmitReferenceBindingToExpr(Init, &D);
152  EmitStoreOfScalar(RV.getScalarVal(), DeclPtr, false, Alignment, T);
153}
154
155static llvm::Function *
156CreateGlobalInitOrDestructFunction(CodeGenModule &CGM,
157                                   llvm::FunctionType *ty,
158                                   const Twine &name);
159
160/// Create a stub function, suitable for being passed to atexit,
161/// which passes the given address to the given destructor function.
162static llvm::Constant *createAtExitStub(CodeGenModule &CGM,
163                                        llvm::Constant *dtor,
164                                        llvm::Constant *addr) {
165  // Get the destructor function type, void(*)(void).
166  llvm::FunctionType *ty = llvm::FunctionType::get(CGM.VoidTy, false);
167  llvm::Function *fn =
168    CreateGlobalInitOrDestructFunction(CGM, ty,
169                                       Twine("__dtor_", addr->getName()));
170
171  CodeGenFunction CGF(CGM);
172
173  // Initialize debug info if needed.
174  CGF.maybeInitializeDebugInfo();
175
176  CGF.StartFunction(GlobalDecl(), CGM.getContext().VoidTy, fn,
177                    CGM.getTypes().arrangeNullaryFunction(),
178                    FunctionArgList(), SourceLocation());
179
180  llvm::CallInst *call = CGF.Builder.CreateCall(dtor, addr);
181
182 // Make sure the call and the callee agree on calling convention.
183  if (llvm::Function *dtorFn =
184        dyn_cast<llvm::Function>(dtor->stripPointerCasts()))
185    call->setCallingConv(dtorFn->getCallingConv());
186
187  CGF.FinishFunction();
188
189  return fn;
190}
191
192/// Register a global destructor using the C atexit runtime function.
193void CodeGenFunction::registerGlobalDtorWithAtExit(llvm::Constant *dtor,
194                                                   llvm::Constant *addr) {
195  // Create a function which calls the destructor.
196  llvm::Constant *dtorStub = createAtExitStub(CGM, dtor, addr);
197
198  // extern "C" int atexit(void (*f)(void));
199  llvm::FunctionType *atexitTy =
200    llvm::FunctionType::get(IntTy, dtorStub->getType(), false);
201
202  llvm::Constant *atexit =
203    CGM.CreateRuntimeFunction(atexitTy, "atexit");
204  if (llvm::Function *atexitFn = dyn_cast<llvm::Function>(atexit))
205    atexitFn->setDoesNotThrow();
206
207  EmitNounwindRuntimeCall(atexit, dtorStub);
208}
209
210void CodeGenFunction::EmitCXXGuardedInit(const VarDecl &D,
211                                         llvm::GlobalVariable *DeclPtr,
212                                         bool PerformInit) {
213  // If we've been asked to forbid guard variables, emit an error now.
214  // This diagnostic is hard-coded for Darwin's use case;  we can find
215  // better phrasing if someone else needs it.
216  if (CGM.getCodeGenOpts().ForbidGuardVariables)
217    CGM.Error(D.getLocation(),
218              "this initialization requires a guard variable, which "
219              "the kernel does not support");
220
221  CGM.getCXXABI().EmitGuardedInit(*this, D, DeclPtr, PerformInit);
222}
223
224static llvm::Function *
225CreateGlobalInitOrDestructFunction(CodeGenModule &CGM,
226                                   llvm::FunctionType *FTy,
227                                   const Twine &Name) {
228  llvm::Function *Fn =
229    llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage,
230                           Name, &CGM.getModule());
231  if (!CGM.getLangOpts().AppleKext) {
232    // Set the section if needed.
233    if (const char *Section =
234          CGM.getContext().getTargetInfo().getStaticInitSectionSpecifier())
235      Fn->setSection(Section);
236  }
237
238  Fn->setCallingConv(CGM.getRuntimeCC());
239
240  if (!CGM.getLangOpts().Exceptions)
241    Fn->setDoesNotThrow();
242
243  if (CGM.getSanOpts().Address)
244    Fn->addFnAttr(llvm::Attribute::SanitizeAddress);
245  if (CGM.getSanOpts().Thread)
246    Fn->addFnAttr(llvm::Attribute::SanitizeThread);
247  if (CGM.getSanOpts().Memory)
248    Fn->addFnAttr(llvm::Attribute::SanitizeMemory);
249
250  return Fn;
251}
252
253void
254CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D,
255                                            llvm::GlobalVariable *Addr,
256                                            bool PerformInit) {
257  llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
258
259  // Create a variable initialization function.
260  llvm::Function *Fn =
261    CreateGlobalInitOrDestructFunction(*this, FTy, "__cxx_global_var_init");
262
263  CodeGenFunction(*this).GenerateCXXGlobalVarDeclInitFunc(Fn, D, Addr,
264                                                          PerformInit);
265
266  if (D->hasAttr<InitPriorityAttr>()) {
267    unsigned int order = D->getAttr<InitPriorityAttr>()->getPriority();
268    OrderGlobalInits Key(order, PrioritizedCXXGlobalInits.size());
269    PrioritizedCXXGlobalInits.push_back(std::make_pair(Key, Fn));
270    DelayedCXXInitPosition.erase(D);
271  }  else {
272    llvm::DenseMap<const Decl *, unsigned>::iterator I =
273      DelayedCXXInitPosition.find(D);
274    if (I == DelayedCXXInitPosition.end()) {
275      CXXGlobalInits.push_back(Fn);
276    } else {
277      assert(CXXGlobalInits[I->second] == 0);
278      CXXGlobalInits[I->second] = Fn;
279      DelayedCXXInitPosition.erase(I);
280    }
281  }
282}
283
284void
285CodeGenModule::EmitCXXGlobalInitFunc() {
286  while (!CXXGlobalInits.empty() && !CXXGlobalInits.back())
287    CXXGlobalInits.pop_back();
288
289  if (CXXGlobalInits.empty() && PrioritizedCXXGlobalInits.empty())
290    return;
291
292  llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
293
294
295  // Create our global initialization function.
296  if (!PrioritizedCXXGlobalInits.empty()) {
297    SmallVector<llvm::Constant*, 8> LocalCXXGlobalInits;
298    llvm::array_pod_sort(PrioritizedCXXGlobalInits.begin(),
299                         PrioritizedCXXGlobalInits.end());
300    // Iterate over "chunks" of ctors with same priority and emit each chunk
301    // into separate function. Note - everything is sorted first by priority,
302    // second - by lex order, so we emit ctor functions in proper order.
303    for (SmallVectorImpl<GlobalInitData >::iterator
304           I = PrioritizedCXXGlobalInits.begin(),
305           E = PrioritizedCXXGlobalInits.end(); I != E; ) {
306      SmallVectorImpl<GlobalInitData >::iterator
307        PrioE = std::upper_bound(I + 1, E, *I, GlobalInitPriorityCmp());
308
309      LocalCXXGlobalInits.clear();
310      unsigned Priority = I->first.priority;
311      // Compute the function suffix from priority. Prepend with zeroes to make
312      // sure the function names are also ordered as priorities.
313      std::string PrioritySuffix = llvm::utostr(Priority);
314      // Priority is always <= 65535 (enforced by sema)..
315      PrioritySuffix = std::string(6-PrioritySuffix.size(), '0')+PrioritySuffix;
316      llvm::Function *Fn =
317        CreateGlobalInitOrDestructFunction(*this, FTy,
318                                           "_GLOBAL__I_" + PrioritySuffix);
319
320      for (; I < PrioE; ++I)
321        LocalCXXGlobalInits.push_back(I->second);
322
323      CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn,
324                                                    &LocalCXXGlobalInits[0],
325                                                    LocalCXXGlobalInits.size());
326      AddGlobalCtor(Fn, Priority);
327    }
328  }
329
330  llvm::Function *Fn =
331    CreateGlobalInitOrDestructFunction(*this, FTy, "_GLOBAL__I_a");
332
333  CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn,
334                                                   &CXXGlobalInits[0],
335                                                   CXXGlobalInits.size());
336  AddGlobalCtor(Fn);
337
338  CXXGlobalInits.clear();
339  PrioritizedCXXGlobalInits.clear();
340}
341
342void CodeGenModule::EmitCXXGlobalDtorFunc() {
343  if (CXXGlobalDtors.empty())
344    return;
345
346  llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
347
348  // Create our global destructor function.
349  llvm::Function *Fn =
350    CreateGlobalInitOrDestructFunction(*this, FTy, "_GLOBAL__D_a");
351
352  CodeGenFunction(*this).GenerateCXXGlobalDtorsFunc(Fn, CXXGlobalDtors);
353  AddGlobalDtor(Fn);
354}
355
356/// Emit the code necessary to initialize the given global variable.
357void CodeGenFunction::GenerateCXXGlobalVarDeclInitFunc(llvm::Function *Fn,
358                                                       const VarDecl *D,
359                                                 llvm::GlobalVariable *Addr,
360                                                       bool PerformInit) {
361  // Check if we need to emit debug info for variable initializer.
362  if (!D->hasAttr<NoDebugAttr>())
363    maybeInitializeDebugInfo();
364
365  StartFunction(GlobalDecl(D), getContext().VoidTy, Fn,
366                getTypes().arrangeNullaryFunction(),
367                FunctionArgList(), D->getInit()->getExprLoc());
368
369  // Use guarded initialization if the global variable is weak. This
370  // occurs for, e.g., instantiated static data members and
371  // definitions explicitly marked weak.
372  if (Addr->getLinkage() == llvm::GlobalValue::WeakODRLinkage ||
373      Addr->getLinkage() == llvm::GlobalValue::WeakAnyLinkage) {
374    EmitCXXGuardedInit(*D, Addr, PerformInit);
375  } else {
376    EmitCXXGlobalVarDeclInit(*D, Addr, PerformInit);
377  }
378
379  FinishFunction();
380}
381
382void CodeGenFunction::GenerateCXXGlobalInitFunc(llvm::Function *Fn,
383                                                llvm::Constant **Decls,
384                                                unsigned NumDecls) {
385  // Initialize debug info if needed.
386  maybeInitializeDebugInfo();
387
388  StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
389                getTypes().arrangeNullaryFunction(),
390                FunctionArgList(), SourceLocation());
391
392  RunCleanupsScope Scope(*this);
393
394  // When building in Objective-C++ ARC mode, create an autorelease pool
395  // around the global initializers.
396  if (getLangOpts().ObjCAutoRefCount && getLangOpts().CPlusPlus) {
397    llvm::Value *token = EmitObjCAutoreleasePoolPush();
398    EmitObjCAutoreleasePoolCleanup(token);
399  }
400
401  for (unsigned i = 0; i != NumDecls; ++i)
402    if (Decls[i])
403      EmitRuntimeCall(Decls[i]);
404
405  Scope.ForceCleanup();
406
407  FinishFunction();
408}
409
410void CodeGenFunction::GenerateCXXGlobalDtorsFunc(llvm::Function *Fn,
411                  const std::vector<std::pair<llvm::WeakVH, llvm::Constant*> >
412                                                &DtorsAndObjects) {
413  // Initialize debug info if needed.
414  maybeInitializeDebugInfo();
415
416  StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
417                getTypes().arrangeNullaryFunction(),
418                FunctionArgList(), SourceLocation());
419
420  // Emit the dtors, in reverse order from construction.
421  for (unsigned i = 0, e = DtorsAndObjects.size(); i != e; ++i) {
422    llvm::Value *Callee = DtorsAndObjects[e - i - 1].first;
423    llvm::CallInst *CI = Builder.CreateCall(Callee,
424                                            DtorsAndObjects[e - i - 1].second);
425    // Make sure the call and the callee agree on calling convention.
426    if (llvm::Function *F = dyn_cast<llvm::Function>(Callee))
427      CI->setCallingConv(F->getCallingConv());
428  }
429
430  FinishFunction();
431}
432
433/// generateDestroyHelper - Generates a helper function which, when
434/// invoked, destroys the given object.
435llvm::Function *
436CodeGenFunction::generateDestroyHelper(llvm::Constant *addr,
437                                       QualType type,
438                                       Destroyer *destroyer,
439                                       bool useEHCleanupForArray) {
440  FunctionArgList args;
441  ImplicitParamDecl dst(0, SourceLocation(), 0, getContext().VoidPtrTy);
442  args.push_back(&dst);
443
444  const CGFunctionInfo &FI =
445    CGM.getTypes().arrangeFunctionDeclaration(getContext().VoidTy, args,
446                                              FunctionType::ExtInfo(),
447                                              /*variadic*/ false);
448  llvm::FunctionType *FTy = CGM.getTypes().GetFunctionType(FI);
449  llvm::Function *fn =
450    CreateGlobalInitOrDestructFunction(CGM, FTy, "__cxx_global_array_dtor");
451
452  // Initialize debug info if needed.
453  maybeInitializeDebugInfo();
454
455  StartFunction(GlobalDecl(), getContext().VoidTy, fn, FI, args,
456                SourceLocation());
457
458  emitDestroy(addr, type, destroyer, useEHCleanupForArray);
459
460  FinishFunction();
461
462  return fn;
463}
464