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.getTLSKind());
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    assert(!D.getTLSKind() && "should have rejected this");
84    return;
85  }
86
87  llvm::Constant *function;
88  llvm::Constant *argument;
89
90  // Special-case non-array C++ destructors, where there's a function
91  // with the right signature that we can just call.
92  const CXXRecordDecl *record = 0;
93  if (dtorKind == QualType::DK_cxx_destructor &&
94      (record = type->getAsCXXRecordDecl())) {
95    assert(!record->hasTrivialDestructor());
96    CXXDestructorDecl *dtor = record->getDestructor();
97
98    function = CGM.GetAddrOfCXXDestructor(dtor, Dtor_Complete);
99    argument = addr;
100
101  // Otherwise, the standard logic requires a helper function.
102  } else {
103    function = CodeGenFunction(CGM).generateDestroyHelper(addr, type,
104                                                  CGF.getDestroyer(dtorKind),
105                                                  CGF.needsEHCleanup(dtorKind));
106    argument = llvm::Constant::getNullValue(CGF.Int8PtrTy);
107  }
108
109  CGM.getCXXABI().registerGlobalDtor(CGF, D, function, argument);
110}
111
112/// Emit code to cause the variable at the given address to be considered as
113/// constant from this point onwards.
114static void EmitDeclInvariant(CodeGenFunction &CGF, const VarDecl &D,
115                              llvm::Constant *Addr) {
116  // Don't emit the intrinsic if we're not optimizing.
117  if (!CGF.CGM.getCodeGenOpts().OptimizationLevel)
118    return;
119
120  // Grab the llvm.invariant.start intrinsic.
121  llvm::Intrinsic::ID InvStartID = llvm::Intrinsic::invariant_start;
122  llvm::Constant *InvariantStart = CGF.CGM.getIntrinsic(InvStartID);
123
124  // Emit a call with the size in bytes of the object.
125  CharUnits WidthChars = CGF.getContext().getTypeSizeInChars(D.getType());
126  uint64_t Width = WidthChars.getQuantity();
127  llvm::Value *Args[2] = { llvm::ConstantInt::getSigned(CGF.Int64Ty, Width),
128                           llvm::ConstantExpr::getBitCast(Addr, CGF.Int8PtrTy)};
129  CGF.Builder.CreateCall(InvariantStart, Args);
130}
131
132void CodeGenFunction::EmitCXXGlobalVarDeclInit(const VarDecl &D,
133                                               llvm::Constant *DeclPtr,
134                                               bool PerformInit) {
135
136  const Expr *Init = D.getInit();
137  QualType T = D.getType();
138
139  if (!T->isReferenceType()) {
140    if (PerformInit)
141      EmitDeclInit(*this, D, DeclPtr);
142    if (CGM.isTypeConstant(D.getType(), true))
143      EmitDeclInvariant(*this, D, DeclPtr);
144    else
145      EmitDeclDestroy(*this, D, DeclPtr);
146    return;
147  }
148
149  assert(PerformInit && "cannot have constant initializer which needs "
150         "destruction for reference");
151  unsigned Alignment = getContext().getDeclAlign(&D).getQuantity();
152  RValue RV = EmitReferenceBindingToExpr(Init);
153  EmitStoreOfScalar(RV.getScalarVal(), DeclPtr, false, Alignment, T);
154}
155
156static llvm::Function *
157CreateGlobalInitOrDestructFunction(CodeGenModule &CGM,
158                                   llvm::FunctionType *ty,
159                                   const Twine &name,
160                                   bool TLS = false);
161
162/// Create a stub function, suitable for being passed to atexit,
163/// which passes the given address to the given destructor function.
164static llvm::Constant *createAtExitStub(CodeGenModule &CGM,
165                                        llvm::Constant *dtor,
166                                        llvm::Constant *addr) {
167  // Get the destructor function type, void(*)(void).
168  llvm::FunctionType *ty = llvm::FunctionType::get(CGM.VoidTy, false);
169  llvm::Function *fn =
170    CreateGlobalInitOrDestructFunction(CGM, ty,
171                                       Twine("__dtor_", addr->getName()));
172
173  CodeGenFunction CGF(CGM);
174
175  // Initialize debug info if needed.
176  CGF.maybeInitializeDebugInfo();
177
178  CGF.StartFunction(GlobalDecl(), CGM.getContext().VoidTy, fn,
179                    CGM.getTypes().arrangeNullaryFunction(),
180                    FunctionArgList(), SourceLocation());
181
182  llvm::CallInst *call = CGF.Builder.CreateCall(dtor, addr);
183
184 // Make sure the call and the callee agree on calling convention.
185  if (llvm::Function *dtorFn =
186        dyn_cast<llvm::Function>(dtor->stripPointerCasts()))
187    call->setCallingConv(dtorFn->getCallingConv());
188
189  CGF.FinishFunction();
190
191  return fn;
192}
193
194/// Register a global destructor using the C atexit runtime function.
195void CodeGenFunction::registerGlobalDtorWithAtExit(llvm::Constant *dtor,
196                                                   llvm::Constant *addr) {
197  // Create a function which calls the destructor.
198  llvm::Constant *dtorStub = createAtExitStub(CGM, dtor, addr);
199
200  // extern "C" int atexit(void (*f)(void));
201  llvm::FunctionType *atexitTy =
202    llvm::FunctionType::get(IntTy, dtorStub->getType(), false);
203
204  llvm::Constant *atexit =
205    CGM.CreateRuntimeFunction(atexitTy, "atexit");
206  if (llvm::Function *atexitFn = dyn_cast<llvm::Function>(atexit))
207    atexitFn->setDoesNotThrow();
208
209  EmitNounwindRuntimeCall(atexit, dtorStub);
210}
211
212void CodeGenFunction::EmitCXXGuardedInit(const VarDecl &D,
213                                         llvm::GlobalVariable *DeclPtr,
214                                         bool PerformInit) {
215  // If we've been asked to forbid guard variables, emit an error now.
216  // This diagnostic is hard-coded for Darwin's use case;  we can find
217  // better phrasing if someone else needs it.
218  if (CGM.getCodeGenOpts().ForbidGuardVariables)
219    CGM.Error(D.getLocation(),
220              "this initialization requires a guard variable, which "
221              "the kernel does not support");
222
223  CGM.getCXXABI().EmitGuardedInit(*this, D, DeclPtr, PerformInit);
224}
225
226static llvm::Function *
227CreateGlobalInitOrDestructFunction(CodeGenModule &CGM,
228                                   llvm::FunctionType *FTy,
229                                   const Twine &Name, bool TLS) {
230  llvm::Function *Fn =
231    llvm::Function::Create(FTy, llvm::GlobalValue::InternalLinkage,
232                           Name, &CGM.getModule());
233  if (!CGM.getLangOpts().AppleKext && !TLS) {
234    // Set the section if needed.
235    if (const char *Section =
236          CGM.getTarget().getStaticInitSectionSpecifier())
237      Fn->setSection(Section);
238  }
239
240  Fn->setCallingConv(CGM.getRuntimeCC());
241
242  if (!CGM.getLangOpts().Exceptions)
243    Fn->setDoesNotThrow();
244
245  if (CGM.getSanOpts().Address)
246    Fn->addFnAttr(llvm::Attribute::SanitizeAddress);
247  if (CGM.getSanOpts().Thread)
248    Fn->addFnAttr(llvm::Attribute::SanitizeThread);
249  if (CGM.getSanOpts().Memory)
250    Fn->addFnAttr(llvm::Attribute::SanitizeMemory);
251
252  return Fn;
253}
254
255void
256CodeGenModule::EmitCXXGlobalVarDeclInitFunc(const VarDecl *D,
257                                            llvm::GlobalVariable *Addr,
258                                            bool PerformInit) {
259  llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
260
261  // Create a variable initialization function.
262  llvm::Function *Fn =
263    CreateGlobalInitOrDestructFunction(*this, FTy, "__cxx_global_var_init");
264
265  CodeGenFunction(*this).GenerateCXXGlobalVarDeclInitFunc(Fn, D, Addr,
266                                                          PerformInit);
267
268  if (D->getTLSKind()) {
269    // FIXME: Should we support init_priority for thread_local?
270    // FIXME: Ideally, initialization of instantiated thread_local static data
271    // members of class templates should not trigger initialization of other
272    // entities in the TU.
273    // FIXME: We only need to register one __cxa_thread_atexit function for the
274    // entire TU.
275    CXXThreadLocalInits.push_back(Fn);
276  } else if (D->hasAttr<InitPriorityAttr>()) {
277    unsigned int order = D->getAttr<InitPriorityAttr>()->getPriority();
278    OrderGlobalInits Key(order, PrioritizedCXXGlobalInits.size());
279    PrioritizedCXXGlobalInits.push_back(std::make_pair(Key, Fn));
280    DelayedCXXInitPosition.erase(D);
281  } else {
282    llvm::DenseMap<const Decl *, unsigned>::iterator I =
283      DelayedCXXInitPosition.find(D);
284    if (I == DelayedCXXInitPosition.end()) {
285      CXXGlobalInits.push_back(Fn);
286    } else {
287      assert(CXXGlobalInits[I->second] == 0);
288      CXXGlobalInits[I->second] = Fn;
289      DelayedCXXInitPosition.erase(I);
290    }
291  }
292}
293
294void CodeGenModule::EmitCXXThreadLocalInitFunc() {
295  llvm::Function *InitFn = 0;
296  if (!CXXThreadLocalInits.empty()) {
297    // Generate a guarded initialization function.
298    llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
299    InitFn = CreateGlobalInitOrDestructFunction(*this, FTy, "__tls_init",
300                                                /*TLS*/ true);
301    llvm::GlobalVariable *Guard = new llvm::GlobalVariable(
302        getModule(), Int8Ty, false, llvm::GlobalVariable::InternalLinkage,
303        llvm::ConstantInt::get(Int8Ty, 0), "__tls_guard");
304    Guard->setThreadLocal(true);
305    CodeGenFunction(*this)
306        .GenerateCXXGlobalInitFunc(InitFn, CXXThreadLocalInits, Guard);
307  }
308
309  getCXXABI().EmitThreadLocalInitFuncs(CXXThreadLocals, InitFn);
310
311  CXXThreadLocalInits.clear();
312  CXXThreadLocals.clear();
313}
314
315void
316CodeGenModule::EmitCXXGlobalInitFunc() {
317  while (!CXXGlobalInits.empty() && !CXXGlobalInits.back())
318    CXXGlobalInits.pop_back();
319
320  if (CXXGlobalInits.empty() && PrioritizedCXXGlobalInits.empty())
321    return;
322
323  llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
324
325
326  // Create our global initialization function.
327  if (!PrioritizedCXXGlobalInits.empty()) {
328    SmallVector<llvm::Constant*, 8> LocalCXXGlobalInits;
329    llvm::array_pod_sort(PrioritizedCXXGlobalInits.begin(),
330                         PrioritizedCXXGlobalInits.end());
331    // Iterate over "chunks" of ctors with same priority and emit each chunk
332    // into separate function. Note - everything is sorted first by priority,
333    // second - by lex order, so we emit ctor functions in proper order.
334    for (SmallVectorImpl<GlobalInitData >::iterator
335           I = PrioritizedCXXGlobalInits.begin(),
336           E = PrioritizedCXXGlobalInits.end(); I != E; ) {
337      SmallVectorImpl<GlobalInitData >::iterator
338        PrioE = std::upper_bound(I + 1, E, *I, GlobalInitPriorityCmp());
339
340      LocalCXXGlobalInits.clear();
341      unsigned Priority = I->first.priority;
342      // Compute the function suffix from priority. Prepend with zeroes to make
343      // sure the function names are also ordered as priorities.
344      std::string PrioritySuffix = llvm::utostr(Priority);
345      // Priority is always <= 65535 (enforced by sema)..
346      PrioritySuffix = std::string(6-PrioritySuffix.size(), '0')+PrioritySuffix;
347      llvm::Function *Fn =
348        CreateGlobalInitOrDestructFunction(*this, FTy,
349                                           "_GLOBAL__I_" + PrioritySuffix);
350
351      for (; I < PrioE; ++I)
352        LocalCXXGlobalInits.push_back(I->second);
353
354      CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn, LocalCXXGlobalInits);
355      AddGlobalCtor(Fn, Priority);
356    }
357  }
358
359  llvm::Function *Fn =
360    CreateGlobalInitOrDestructFunction(*this, FTy, "_GLOBAL__I_a");
361
362  CodeGenFunction(*this).GenerateCXXGlobalInitFunc(Fn, CXXGlobalInits);
363  AddGlobalCtor(Fn);
364
365  CXXGlobalInits.clear();
366  PrioritizedCXXGlobalInits.clear();
367}
368
369void CodeGenModule::EmitCXXGlobalDtorFunc() {
370  if (CXXGlobalDtors.empty())
371    return;
372
373  llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, false);
374
375  // Create our global destructor function.
376  llvm::Function *Fn =
377    CreateGlobalInitOrDestructFunction(*this, FTy, "_GLOBAL__D_a");
378
379  CodeGenFunction(*this).GenerateCXXGlobalDtorsFunc(Fn, CXXGlobalDtors);
380  AddGlobalDtor(Fn);
381}
382
383/// Emit the code necessary to initialize the given global variable.
384void CodeGenFunction::GenerateCXXGlobalVarDeclInitFunc(llvm::Function *Fn,
385                                                       const VarDecl *D,
386                                                 llvm::GlobalVariable *Addr,
387                                                       bool PerformInit) {
388  // Check if we need to emit debug info for variable initializer.
389  if (!D->hasAttr<NoDebugAttr>())
390    maybeInitializeDebugInfo();
391
392  StartFunction(GlobalDecl(D), getContext().VoidTy, Fn,
393                getTypes().arrangeNullaryFunction(),
394                FunctionArgList(), D->getInit()->getExprLoc());
395
396  // Use guarded initialization if the global variable is weak. This
397  // occurs for, e.g., instantiated static data members and
398  // definitions explicitly marked weak.
399  if (Addr->getLinkage() == llvm::GlobalValue::WeakODRLinkage ||
400      Addr->getLinkage() == llvm::GlobalValue::WeakAnyLinkage) {
401    EmitCXXGuardedInit(*D, Addr, PerformInit);
402  } else {
403    EmitCXXGlobalVarDeclInit(*D, Addr, PerformInit);
404  }
405
406  FinishFunction();
407}
408
409void
410CodeGenFunction::GenerateCXXGlobalInitFunc(llvm::Function *Fn,
411                                           ArrayRef<llvm::Constant *> Decls,
412                                           llvm::GlobalVariable *Guard) {
413  // Initialize debug info if needed.
414  maybeInitializeDebugInfo();
415
416  StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
417                getTypes().arrangeNullaryFunction(),
418                FunctionArgList(), SourceLocation());
419
420  llvm::BasicBlock *ExitBlock = 0;
421  if (Guard) {
422    // If we have a guard variable, check whether we've already performed these
423    // initializations. This happens for TLS initialization functions.
424    llvm::Value *GuardVal = Builder.CreateLoad(Guard);
425    llvm::Value *Uninit = Builder.CreateIsNull(GuardVal, "guard.uninitialized");
426    // Mark as initialized before initializing anything else. If the
427    // initializers use previously-initialized thread_local vars, that's
428    // probably supposed to be OK, but the standard doesn't say.
429    Builder.CreateStore(llvm::ConstantInt::get(GuardVal->getType(), 1), Guard);
430    llvm::BasicBlock *InitBlock = createBasicBlock("init");
431    ExitBlock = createBasicBlock("exit");
432    Builder.CreateCondBr(Uninit, InitBlock, ExitBlock);
433    EmitBlock(InitBlock);
434  }
435
436  RunCleanupsScope Scope(*this);
437
438  // When building in Objective-C++ ARC mode, create an autorelease pool
439  // around the global initializers.
440  if (getLangOpts().ObjCAutoRefCount && getLangOpts().CPlusPlus) {
441    llvm::Value *token = EmitObjCAutoreleasePoolPush();
442    EmitObjCAutoreleasePoolCleanup(token);
443  }
444
445  for (unsigned i = 0, e = Decls.size(); i != e; ++i)
446    if (Decls[i])
447      EmitRuntimeCall(Decls[i]);
448
449  Scope.ForceCleanup();
450
451  if (ExitBlock) {
452    Builder.CreateBr(ExitBlock);
453    EmitBlock(ExitBlock);
454  }
455
456  FinishFunction();
457}
458
459void CodeGenFunction::GenerateCXXGlobalDtorsFunc(llvm::Function *Fn,
460                  const std::vector<std::pair<llvm::WeakVH, llvm::Constant*> >
461                                                &DtorsAndObjects) {
462  // Initialize debug info if needed.
463  maybeInitializeDebugInfo();
464
465  StartFunction(GlobalDecl(), getContext().VoidTy, Fn,
466                getTypes().arrangeNullaryFunction(),
467                FunctionArgList(), SourceLocation());
468
469  // Emit the dtors, in reverse order from construction.
470  for (unsigned i = 0, e = DtorsAndObjects.size(); i != e; ++i) {
471    llvm::Value *Callee = DtorsAndObjects[e - i - 1].first;
472    llvm::CallInst *CI = Builder.CreateCall(Callee,
473                                            DtorsAndObjects[e - i - 1].second);
474    // Make sure the call and the callee agree on calling convention.
475    if (llvm::Function *F = dyn_cast<llvm::Function>(Callee))
476      CI->setCallingConv(F->getCallingConv());
477  }
478
479  FinishFunction();
480}
481
482/// generateDestroyHelper - Generates a helper function which, when
483/// invoked, destroys the given object.
484llvm::Function *
485CodeGenFunction::generateDestroyHelper(llvm::Constant *addr,
486                                       QualType type,
487                                       Destroyer *destroyer,
488                                       bool useEHCleanupForArray) {
489  FunctionArgList args;
490  ImplicitParamDecl dst(0, SourceLocation(), 0, getContext().VoidPtrTy);
491  args.push_back(&dst);
492
493  const CGFunctionInfo &FI =
494    CGM.getTypes().arrangeFunctionDeclaration(getContext().VoidTy, args,
495                                              FunctionType::ExtInfo(),
496                                              /*variadic*/ false);
497  llvm::FunctionType *FTy = CGM.getTypes().GetFunctionType(FI);
498  llvm::Function *fn =
499    CreateGlobalInitOrDestructFunction(CGM, FTy, "__cxx_global_array_dtor");
500
501  // Initialize debug info if needed.
502  maybeInitializeDebugInfo();
503
504  StartFunction(GlobalDecl(), getContext().VoidTy, fn, FI, args,
505                SourceLocation());
506
507  emitDestroy(addr, type, destroyer, useEHCleanupForArray);
508
509  FinishFunction();
510
511  return fn;
512}
513