CGVTables.cpp revision 8b418685e9e4f02f4eb2a76e1ec063e07552b68d 
1//===--- CGVTables.cpp - Emit LLVM Code for C++ vtables -------------------===//
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 C++ code generation of virtual tables.
11//
12//===----------------------------------------------------------------------===//
13
14#include "CodeGenModule.h"
15#include "CodeGenFunction.h"
16#include "CGCXXABI.h"
17#include "clang/AST/CXXInheritance.h"
18#include "clang/AST/RecordLayout.h"
19#include "clang/Frontend/CodeGenOptions.h"
20#include "llvm/ADT/DenseSet.h"
21#include "llvm/ADT/SetVector.h"
22#include "llvm/Support/Compiler.h"
23#include "llvm/Support/Format.h"
24#include "llvm/Transforms/Utils/Cloning.h"
25#include <algorithm>
26#include <cstdio>
27
28using namespace clang;
29using namespace CodeGen;
30
31CodeGenVTables::CodeGenVTables(CodeGenModule &CGM)
32  : CGM(CGM), VTContext(CGM.getContext()) { }
33
34bool CodeGenVTables::ShouldEmitVTableInThisTU(const CXXRecordDecl *RD) {
35  assert(RD->isDynamicClass() && "Non dynamic classes have no VTable.");
36
37  TemplateSpecializationKind TSK = RD->getTemplateSpecializationKind();
38  if (TSK == TSK_ExplicitInstantiationDeclaration)
39    return false;
40
41  const CXXMethodDecl *KeyFunction = CGM.getContext().getKeyFunction(RD);
42  if (!KeyFunction)
43    return true;
44
45  // Itanium C++ ABI, 5.2.6 Instantiated Templates:
46  //    An instantiation of a class template requires:
47  //        - In the object where instantiated, the virtual table...
48  if (TSK == TSK_ImplicitInstantiation ||
49      TSK == TSK_ExplicitInstantiationDefinition)
50    return true;
51
52  // If we're building with optimization, we always emit VTables since that
53  // allows for virtual function calls to be devirtualized.
54  // (We don't want to do this in -fapple-kext mode however).
55  if (CGM.getCodeGenOpts().OptimizationLevel && !CGM.getLangOptions().AppleKext)
56    return true;
57
58  return KeyFunction->hasBody();
59}
60
61llvm::Constant *CodeGenModule::GetAddrOfThunk(GlobalDecl GD,
62                                              const ThunkInfo &Thunk) {
63  const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
64
65  // Compute the mangled name.
66  SmallString<256> Name;
67  llvm::raw_svector_ostream Out(Name);
68  if (const CXXDestructorDecl* DD = dyn_cast<CXXDestructorDecl>(MD))
69    getCXXABI().getMangleContext().mangleCXXDtorThunk(DD, GD.getDtorType(),
70                                                      Thunk.This, Out);
71  else
72    getCXXABI().getMangleContext().mangleThunk(MD, Thunk, Out);
73  Out.flush();
74
75  llvm::Type *Ty = getTypes().GetFunctionTypeForVTable(GD);
76  return GetOrCreateLLVMFunction(Name, Ty, GD, /*ForVTable=*/true);
77}
78
79static llvm::Value *PerformTypeAdjustment(CodeGenFunction &CGF,
80                                          llvm::Value *Ptr,
81                                          int64_t NonVirtualAdjustment,
82                                          int64_t VirtualAdjustment) {
83  if (!NonVirtualAdjustment && !VirtualAdjustment)
84    return Ptr;
85
86  llvm::Type *Int8PtrTy = CGF.Int8PtrTy;
87  llvm::Value *V = CGF.Builder.CreateBitCast(Ptr, Int8PtrTy);
88
89  if (NonVirtualAdjustment) {
90    // Do the non-virtual adjustment.
91    V = CGF.Builder.CreateConstInBoundsGEP1_64(V, NonVirtualAdjustment);
92  }
93
94  if (VirtualAdjustment) {
95    llvm::Type *PtrDiffTy =
96      CGF.ConvertType(CGF.getContext().getPointerDiffType());
97
98    // Do the virtual adjustment.
99    llvm::Value *VTablePtrPtr =
100      CGF.Builder.CreateBitCast(V, Int8PtrTy->getPointerTo());
101
102    llvm::Value *VTablePtr = CGF.Builder.CreateLoad(VTablePtrPtr);
103
104    llvm::Value *OffsetPtr =
105      CGF.Builder.CreateConstInBoundsGEP1_64(VTablePtr, VirtualAdjustment);
106
107    OffsetPtr = CGF.Builder.CreateBitCast(OffsetPtr, PtrDiffTy->getPointerTo());
108
109    // Load the adjustment offset from the vtable.
110    llvm::Value *Offset = CGF.Builder.CreateLoad(OffsetPtr);
111
112    // Adjust our pointer.
113    V = CGF.Builder.CreateInBoundsGEP(V, Offset);
114  }
115
116  // Cast back to the original type.
117  return CGF.Builder.CreateBitCast(V, Ptr->getType());
118}
119
120static void setThunkVisibility(CodeGenModule &CGM, const CXXMethodDecl *MD,
121                               const ThunkInfo &Thunk, llvm::Function *Fn) {
122  CGM.setGlobalVisibility(Fn, MD);
123
124  if (!CGM.getCodeGenOpts().HiddenWeakVTables)
125    return;
126
127  // If the thunk has weak/linkonce linkage, but the function must be
128  // emitted in every translation unit that references it, then we can
129  // emit its thunks with hidden visibility, since its thunks must be
130  // emitted when the function is.
131
132  // This follows CodeGenModule::setTypeVisibility; see the comments
133  // there for explanation.
134
135  if ((Fn->getLinkage() != llvm::GlobalVariable::LinkOnceODRLinkage &&
136       Fn->getLinkage() != llvm::GlobalVariable::WeakODRLinkage) ||
137      Fn->getVisibility() != llvm::GlobalVariable::DefaultVisibility)
138    return;
139
140  if (MD->getExplicitVisibility())
141    return;
142
143  switch (MD->getTemplateSpecializationKind()) {
144  case TSK_ExplicitInstantiationDefinition:
145  case TSK_ExplicitInstantiationDeclaration:
146    return;
147
148  case TSK_Undeclared:
149    break;
150
151  case TSK_ExplicitSpecialization:
152  case TSK_ImplicitInstantiation:
153    if (!CGM.getCodeGenOpts().HiddenWeakTemplateVTables)
154      return;
155    break;
156  }
157
158  // If there's an explicit definition, and that definition is
159  // out-of-line, then we can't assume that all users will have a
160  // definition to emit.
161  const FunctionDecl *Def = 0;
162  if (MD->hasBody(Def) && Def->isOutOfLine())
163    return;
164
165  Fn->setVisibility(llvm::GlobalValue::HiddenVisibility);
166}
167
168#ifndef NDEBUG
169static bool similar(const ABIArgInfo &infoL, CanQualType typeL,
170                    const ABIArgInfo &infoR, CanQualType typeR) {
171  return (infoL.getKind() == infoR.getKind() &&
172          (typeL == typeR ||
173           (isa<PointerType>(typeL) && isa<PointerType>(typeR)) ||
174           (isa<ReferenceType>(typeL) && isa<ReferenceType>(typeR))));
175}
176#endif
177
178static RValue PerformReturnAdjustment(CodeGenFunction &CGF,
179                                      QualType ResultType, RValue RV,
180                                      const ThunkInfo &Thunk) {
181  // Emit the return adjustment.
182  bool NullCheckValue = !ResultType->isReferenceType();
183
184  llvm::BasicBlock *AdjustNull = 0;
185  llvm::BasicBlock *AdjustNotNull = 0;
186  llvm::BasicBlock *AdjustEnd = 0;
187
188  llvm::Value *ReturnValue = RV.getScalarVal();
189
190  if (NullCheckValue) {
191    AdjustNull = CGF.createBasicBlock("adjust.null");
192    AdjustNotNull = CGF.createBasicBlock("adjust.notnull");
193    AdjustEnd = CGF.createBasicBlock("adjust.end");
194
195    llvm::Value *IsNull = CGF.Builder.CreateIsNull(ReturnValue);
196    CGF.Builder.CreateCondBr(IsNull, AdjustNull, AdjustNotNull);
197    CGF.EmitBlock(AdjustNotNull);
198  }
199
200  ReturnValue = PerformTypeAdjustment(CGF, ReturnValue,
201                                      Thunk.Return.NonVirtual,
202                                      Thunk.Return.VBaseOffsetOffset);
203
204  if (NullCheckValue) {
205    CGF.Builder.CreateBr(AdjustEnd);
206    CGF.EmitBlock(AdjustNull);
207    CGF.Builder.CreateBr(AdjustEnd);
208    CGF.EmitBlock(AdjustEnd);
209
210    llvm::PHINode *PHI = CGF.Builder.CreatePHI(ReturnValue->getType(), 2);
211    PHI->addIncoming(ReturnValue, AdjustNotNull);
212    PHI->addIncoming(llvm::Constant::getNullValue(ReturnValue->getType()),
213                     AdjustNull);
214    ReturnValue = PHI;
215  }
216
217  return RValue::get(ReturnValue);
218}
219
220// This function does roughly the same thing as GenerateThunk, but in a
221// very different way, so that va_start and va_end work correctly.
222// FIXME: This function assumes "this" is the first non-sret LLVM argument of
223//        a function, and that there is an alloca built in the entry block
224//        for all accesses to "this".
225// FIXME: This function assumes there is only one "ret" statement per function.
226// FIXME: Cloning isn't correct in the presence of indirect goto!
227// FIXME: This implementation of thunks bloats codesize by duplicating the
228//        function definition.  There are alternatives:
229//        1. Add some sort of stub support to LLVM for cases where we can
230//           do a this adjustment, then a sibcall.
231//        2. We could transform the definition to take a va_list instead of an
232//           actual variable argument list, then have the thunks (including a
233//           no-op thunk for the regular definition) call va_start/va_end.
234//           There's a bit of per-call overhead for this solution, but it's
235//           better for codesize if the definition is long.
236void CodeGenFunction::GenerateVarArgsThunk(
237                                      llvm::Function *Fn,
238                                      const CGFunctionInfo &FnInfo,
239                                      GlobalDecl GD, const ThunkInfo &Thunk) {
240  const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
241  const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
242  QualType ResultType = FPT->getResultType();
243
244  // Get the original function
245  llvm::Type *Ty =
246    CGM.getTypes().GetFunctionType(FnInfo, /*IsVariadic*/true);
247  llvm::Value *Callee = CGM.GetAddrOfFunction(GD, Ty, /*ForVTable=*/true);
248  llvm::Function *BaseFn = cast<llvm::Function>(Callee);
249
250  // Clone to thunk.
251  llvm::Function *NewFn = llvm::CloneFunction(BaseFn);
252  CGM.getModule().getFunctionList().push_back(NewFn);
253  Fn->replaceAllUsesWith(NewFn);
254  NewFn->takeName(Fn);
255  Fn->eraseFromParent();
256  Fn = NewFn;
257
258  // "Initialize" CGF (minimally).
259  CurFn = Fn;
260
261  // Get the "this" value
262  llvm::Function::arg_iterator AI = Fn->arg_begin();
263  if (CGM.ReturnTypeUsesSRet(FnInfo))
264    ++AI;
265
266  // Find the first store of "this", which will be to the alloca associated
267  // with "this".
268  llvm::Value *ThisPtr = &*AI;
269  llvm::BasicBlock *EntryBB = Fn->begin();
270  llvm::Instruction *ThisStore = 0;
271  for (llvm::BasicBlock::iterator I = EntryBB->begin(), E = EntryBB->end();
272       I != E; I++) {
273    if (isa<llvm::StoreInst>(I) && I->getOperand(0) == ThisPtr) {
274      ThisStore = cast<llvm::StoreInst>(I);
275      break;
276    }
277  }
278  assert(ThisStore && "Store of this should be in entry block?");
279  // Adjust "this", if necessary.
280  Builder.SetInsertPoint(ThisStore);
281  llvm::Value *AdjustedThisPtr =
282    PerformTypeAdjustment(*this, ThisPtr,
283                          Thunk.This.NonVirtual,
284                          Thunk.This.VCallOffsetOffset);
285  ThisStore->setOperand(0, AdjustedThisPtr);
286
287  if (!Thunk.Return.isEmpty()) {
288    // Fix up the returned value, if necessary.
289    for (llvm::Function::iterator I = Fn->begin(), E = Fn->end(); I != E; I++) {
290      llvm::Instruction *T = I->getTerminator();
291      if (isa<llvm::ReturnInst>(T)) {
292        RValue RV = RValue::get(T->getOperand(0));
293        T->eraseFromParent();
294        Builder.SetInsertPoint(&*I);
295        RV = PerformReturnAdjustment(*this, ResultType, RV, Thunk);
296        Builder.CreateRet(RV.getScalarVal());
297        break;
298      }
299    }
300  }
301}
302
303void CodeGenFunction::GenerateThunk(llvm::Function *Fn,
304                                    const CGFunctionInfo &FnInfo,
305                                    GlobalDecl GD, const ThunkInfo &Thunk) {
306  const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
307  const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
308  QualType ResultType = FPT->getResultType();
309  QualType ThisType = MD->getThisType(getContext());
310
311  FunctionArgList FunctionArgs;
312
313  // FIXME: It would be nice if more of this code could be shared with
314  // CodeGenFunction::GenerateCode.
315
316  // Create the implicit 'this' parameter declaration.
317  CurGD = GD;
318  CGM.getCXXABI().BuildInstanceFunctionParams(*this, ResultType, FunctionArgs);
319
320  // Add the rest of the parameters.
321  for (FunctionDecl::param_const_iterator I = MD->param_begin(),
322       E = MD->param_end(); I != E; ++I) {
323    ParmVarDecl *Param = *I;
324
325    FunctionArgs.push_back(Param);
326  }
327
328  StartFunction(GlobalDecl(), ResultType, Fn, FnInfo, FunctionArgs,
329                SourceLocation());
330
331  CGM.getCXXABI().EmitInstanceFunctionProlog(*this);
332
333  // Adjust the 'this' pointer if necessary.
334  llvm::Value *AdjustedThisPtr =
335    PerformTypeAdjustment(*this, LoadCXXThis(),
336                          Thunk.This.NonVirtual,
337                          Thunk.This.VCallOffsetOffset);
338
339  CallArgList CallArgs;
340
341  // Add our adjusted 'this' pointer.
342  CallArgs.add(RValue::get(AdjustedThisPtr), ThisType);
343
344  // Add the rest of the parameters.
345  for (FunctionDecl::param_const_iterator I = MD->param_begin(),
346       E = MD->param_end(); I != E; ++I) {
347    ParmVarDecl *param = *I;
348    EmitDelegateCallArg(CallArgs, param);
349  }
350
351  // Get our callee.
352  llvm::Type *Ty =
353    CGM.getTypes().GetFunctionType(CGM.getTypes().getFunctionInfo(GD),
354                                   FPT->isVariadic());
355  llvm::Value *Callee = CGM.GetAddrOfFunction(GD, Ty, /*ForVTable=*/true);
356
357#ifndef NDEBUG
358  const CGFunctionInfo &CallFnInfo =
359    CGM.getTypes().getFunctionInfo(ResultType, CallArgs, FPT->getExtInfo());
360  assert(CallFnInfo.getRegParm() == FnInfo.getRegParm() &&
361         CallFnInfo.isNoReturn() == FnInfo.isNoReturn() &&
362         CallFnInfo.getCallingConvention() == FnInfo.getCallingConvention());
363  assert(similar(CallFnInfo.getReturnInfo(), CallFnInfo.getReturnType(),
364                 FnInfo.getReturnInfo(), FnInfo.getReturnType()));
365  assert(CallFnInfo.arg_size() == FnInfo.arg_size());
366  for (unsigned i = 0, e = FnInfo.arg_size(); i != e; ++i)
367    assert(similar(CallFnInfo.arg_begin()[i].info,
368                   CallFnInfo.arg_begin()[i].type,
369                   FnInfo.arg_begin()[i].info, FnInfo.arg_begin()[i].type));
370#endif
371
372  // Determine whether we have a return value slot to use.
373  ReturnValueSlot Slot;
374  if (!ResultType->isVoidType() &&
375      FnInfo.getReturnInfo().getKind() == ABIArgInfo::Indirect &&
376      hasAggregateLLVMType(CurFnInfo->getReturnType()))
377    Slot = ReturnValueSlot(ReturnValue, ResultType.isVolatileQualified());
378
379  // Now emit our call.
380  RValue RV = EmitCall(FnInfo, Callee, Slot, CallArgs, MD);
381
382  if (!Thunk.Return.isEmpty())
383    RV = PerformReturnAdjustment(*this, ResultType, RV, Thunk);
384
385  if (!ResultType->isVoidType() && Slot.isNull())
386    CGM.getCXXABI().EmitReturnFromThunk(*this, RV, ResultType);
387
388  FinishFunction();
389
390  // Set the right linkage.
391  CGM.setFunctionLinkage(MD, Fn);
392
393  // Set the right visibility.
394  setThunkVisibility(CGM, MD, Thunk, Fn);
395}
396
397void CodeGenVTables::EmitThunk(GlobalDecl GD, const ThunkInfo &Thunk,
398                               bool UseAvailableExternallyLinkage)
399{
400  const CGFunctionInfo &FnInfo = CGM.getTypes().getFunctionInfo(GD);
401
402  // FIXME: re-use FnInfo in this computation.
403  llvm::Constant *Entry = CGM.GetAddrOfThunk(GD, Thunk);
404
405  // Strip off a bitcast if we got one back.
406  if (llvm::ConstantExpr *CE = dyn_cast<llvm::ConstantExpr>(Entry)) {
407    assert(CE->getOpcode() == llvm::Instruction::BitCast);
408    Entry = CE->getOperand(0);
409  }
410
411  // There's already a declaration with the same name, check if it has the same
412  // type or if we need to replace it.
413  if (cast<llvm::GlobalValue>(Entry)->getType()->getElementType() !=
414      CGM.getTypes().GetFunctionTypeForVTable(GD)) {
415    llvm::GlobalValue *OldThunkFn = cast<llvm::GlobalValue>(Entry);
416
417    // If the types mismatch then we have to rewrite the definition.
418    assert(OldThunkFn->isDeclaration() &&
419           "Shouldn't replace non-declaration");
420
421    // Remove the name from the old thunk function and get a new thunk.
422    OldThunkFn->setName(StringRef());
423    Entry = CGM.GetAddrOfThunk(GD, Thunk);
424
425    // If needed, replace the old thunk with a bitcast.
426    if (!OldThunkFn->use_empty()) {
427      llvm::Constant *NewPtrForOldDecl =
428        llvm::ConstantExpr::getBitCast(Entry, OldThunkFn->getType());
429      OldThunkFn->replaceAllUsesWith(NewPtrForOldDecl);
430    }
431
432    // Remove the old thunk.
433    OldThunkFn->eraseFromParent();
434  }
435
436  llvm::Function *ThunkFn = cast<llvm::Function>(Entry);
437
438  if (!ThunkFn->isDeclaration()) {
439    if (UseAvailableExternallyLinkage) {
440      // There is already a thunk emitted for this function, do nothing.
441      return;
442    }
443
444    // If a function has a body, it should have available_externally linkage.
445    assert(ThunkFn->hasAvailableExternallyLinkage() &&
446           "Function should have available_externally linkage!");
447
448    // Change the linkage.
449    CGM.setFunctionLinkage(cast<CXXMethodDecl>(GD.getDecl()), ThunkFn);
450    return;
451  }
452
453  if (ThunkFn->isVarArg()) {
454    // Varargs thunks are special; we can't just generate a call because
455    // we can't copy the varargs.  Our implementation is rather
456    // expensive/sucky at the moment, so don't generate the thunk unless
457    // we have to.
458    // FIXME: Do something better here; GenerateVarArgsThunk is extremely ugly.
459    if (!UseAvailableExternallyLinkage)
460      CodeGenFunction(CGM).GenerateVarArgsThunk(ThunkFn, FnInfo, GD, Thunk);
461  } else {
462    // Normal thunk body generation.
463    CodeGenFunction(CGM).GenerateThunk(ThunkFn, FnInfo, GD, Thunk);
464  }
465
466  if (UseAvailableExternallyLinkage)
467    ThunkFn->setLinkage(llvm::GlobalValue::AvailableExternallyLinkage);
468}
469
470void CodeGenVTables::MaybeEmitThunkAvailableExternally(GlobalDecl GD,
471                                                       const ThunkInfo &Thunk) {
472  // We only want to do this when building with optimizations.
473  if (!CGM.getCodeGenOpts().OptimizationLevel)
474    return;
475
476  // We can't emit thunks for member functions with incomplete types.
477  const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
478  if (!CGM.getTypes().isFuncTypeConvertible(
479                                cast<FunctionType>(MD->getType().getTypePtr())))
480    return;
481
482  EmitThunk(GD, Thunk, /*UseAvailableExternallyLinkage=*/true);
483}
484
485void CodeGenVTables::EmitThunks(GlobalDecl GD)
486{
487  const CXXMethodDecl *MD =
488    cast<CXXMethodDecl>(GD.getDecl())->getCanonicalDecl();
489
490  // We don't need to generate thunks for the base destructor.
491  if (isa<CXXDestructorDecl>(MD) && GD.getDtorType() == Dtor_Base)
492    return;
493
494  const VTableContext::ThunkInfoVectorTy *ThunkInfoVector =
495    VTContext.getThunkInfo(MD);
496  if (!ThunkInfoVector)
497    return;
498
499  for (unsigned I = 0, E = ThunkInfoVector->size(); I != E; ++I)
500    EmitThunk(GD, (*ThunkInfoVector)[I],
501              /*UseAvailableExternallyLinkage=*/false);
502}
503
504llvm::Constant *
505CodeGenVTables::CreateVTableInitializer(const CXXRecordDecl *RD,
506                                        const VTableComponent *Components,
507                                        unsigned NumComponents,
508                                const VTableLayout::VTableThunkTy *VTableThunks,
509                                        unsigned NumVTableThunks) {
510  SmallVector<llvm::Constant *, 64> Inits;
511
512  llvm::Type *Int8PtrTy = CGM.Int8PtrTy;
513
514  llvm::Type *PtrDiffTy =
515    CGM.getTypes().ConvertType(CGM.getContext().getPointerDiffType());
516
517  QualType ClassType = CGM.getContext().getTagDeclType(RD);
518  llvm::Constant *RTTI = CGM.GetAddrOfRTTIDescriptor(ClassType);
519
520  unsigned NextVTableThunkIndex = 0;
521
522  llvm::Constant* PureVirtualFn = 0;
523
524  for (unsigned I = 0; I != NumComponents; ++I) {
525    VTableComponent Component = Components[I];
526
527    llvm::Constant *Init = 0;
528
529    switch (Component.getKind()) {
530    case VTableComponent::CK_VCallOffset:
531      Init = llvm::ConstantInt::get(PtrDiffTy,
532                                    Component.getVCallOffset().getQuantity());
533      Init = llvm::ConstantExpr::getIntToPtr(Init, Int8PtrTy);
534      break;
535    case VTableComponent::CK_VBaseOffset:
536      Init = llvm::ConstantInt::get(PtrDiffTy,
537                                    Component.getVBaseOffset().getQuantity());
538      Init = llvm::ConstantExpr::getIntToPtr(Init, Int8PtrTy);
539      break;
540    case VTableComponent::CK_OffsetToTop:
541      Init = llvm::ConstantInt::get(PtrDiffTy,
542                                    Component.getOffsetToTop().getQuantity());
543      Init = llvm::ConstantExpr::getIntToPtr(Init, Int8PtrTy);
544      break;
545    case VTableComponent::CK_RTTI:
546      Init = llvm::ConstantExpr::getBitCast(RTTI, Int8PtrTy);
547      break;
548    case VTableComponent::CK_FunctionPointer:
549    case VTableComponent::CK_CompleteDtorPointer:
550    case VTableComponent::CK_DeletingDtorPointer: {
551      GlobalDecl GD;
552
553      // Get the right global decl.
554      switch (Component.getKind()) {
555      default:
556        llvm_unreachable("Unexpected vtable component kind");
557      case VTableComponent::CK_FunctionPointer:
558        GD = Component.getFunctionDecl();
559        break;
560      case VTableComponent::CK_CompleteDtorPointer:
561        GD = GlobalDecl(Component.getDestructorDecl(), Dtor_Complete);
562        break;
563      case VTableComponent::CK_DeletingDtorPointer:
564        GD = GlobalDecl(Component.getDestructorDecl(), Dtor_Deleting);
565        break;
566      }
567
568      if (cast<CXXMethodDecl>(GD.getDecl())->isPure()) {
569        // We have a pure virtual member function.
570        if (!PureVirtualFn) {
571          llvm::FunctionType *Ty =
572            llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false);
573          PureVirtualFn =
574            CGM.CreateRuntimeFunction(Ty, "__cxa_pure_virtual");
575          PureVirtualFn = llvm::ConstantExpr::getBitCast(PureVirtualFn,
576                                                         Int8PtrTy);
577        }
578
579        Init = PureVirtualFn;
580      } else {
581        // Check if we should use a thunk.
582        if (NextVTableThunkIndex < NumVTableThunks &&
583            VTableThunks[NextVTableThunkIndex].first == I) {
584          const ThunkInfo &Thunk = VTableThunks[NextVTableThunkIndex].second;
585
586          Init = CGM.GetAddrOfThunk(GD, Thunk);
587          MaybeEmitThunkAvailableExternally(GD, Thunk);
588
589          NextVTableThunkIndex++;
590        } else {
591          llvm::Type *Ty = CGM.getTypes().GetFunctionTypeForVTable(GD);
592
593          Init = CGM.GetAddrOfFunction(GD, Ty, /*ForVTable=*/true);
594        }
595
596        Init = llvm::ConstantExpr::getBitCast(Init, Int8PtrTy);
597      }
598      break;
599    }
600
601    case VTableComponent::CK_UnusedFunctionPointer:
602      Init = llvm::ConstantExpr::getNullValue(Int8PtrTy);
603      break;
604    };
605
606    Inits.push_back(Init);
607  }
608
609  llvm::ArrayType *ArrayType = llvm::ArrayType::get(Int8PtrTy, NumComponents);
610  return llvm::ConstantArray::get(ArrayType, Inits);
611}
612
613llvm::GlobalVariable *CodeGenVTables::GetAddrOfVTable(const CXXRecordDecl *RD) {
614  llvm::GlobalVariable *&VTable = VTables[RD];
615  if (VTable)
616    return VTable;
617
618  // We may need to generate a definition for this vtable.
619  if (ShouldEmitVTableInThisTU(RD))
620    CGM.DeferredVTables.push_back(RD);
621
622  SmallString<256> OutName;
623  llvm::raw_svector_ostream Out(OutName);
624  CGM.getCXXABI().getMangleContext().mangleCXXVTable(RD, Out);
625  Out.flush();
626  StringRef Name = OutName.str();
627
628  llvm::ArrayType *ArrayType =
629    llvm::ArrayType::get(CGM.Int8PtrTy,
630                        VTContext.getVTableLayout(RD).getNumVTableComponents());
631
632  VTable =
633    CGM.CreateOrReplaceCXXRuntimeVariable(Name, ArrayType,
634                                          llvm::GlobalValue::ExternalLinkage);
635  VTable->setUnnamedAddr(true);
636  return VTable;
637}
638
639void
640CodeGenVTables::EmitVTableDefinition(llvm::GlobalVariable *VTable,
641                                     llvm::GlobalVariable::LinkageTypes Linkage,
642                                     const CXXRecordDecl *RD) {
643  const VTableLayout &VTLayout = VTContext.getVTableLayout(RD);
644
645  // Create and set the initializer.
646  llvm::Constant *Init =
647    CreateVTableInitializer(RD,
648                            VTLayout.vtable_component_begin(),
649                            VTLayout.getNumVTableComponents(),
650                            VTLayout.vtable_thunk_begin(),
651                            VTLayout.getNumVTableThunks());
652  VTable->setInitializer(Init);
653
654  // Set the correct linkage.
655  VTable->setLinkage(Linkage);
656
657  // Set the right visibility.
658  CGM.setTypeVisibility(VTable, RD, CodeGenModule::TVK_ForVTable);
659}
660
661llvm::GlobalVariable *
662CodeGenVTables::GenerateConstructionVTable(const CXXRecordDecl *RD,
663                                      const BaseSubobject &Base,
664                                      bool BaseIsVirtual,
665                                   llvm::GlobalVariable::LinkageTypes Linkage,
666                                      VTableAddressPointsMapTy& AddressPoints) {
667  OwningPtr<VTableLayout> VTLayout(
668    VTContext.createConstructionVTableLayout(Base.getBase(),
669                                             Base.getBaseOffset(),
670                                             BaseIsVirtual, RD));
671
672  // Add the address points.
673  AddressPoints = VTLayout->getAddressPoints();
674
675  // Get the mangled construction vtable name.
676  SmallString<256> OutName;
677  llvm::raw_svector_ostream Out(OutName);
678  CGM.getCXXABI().getMangleContext().
679    mangleCXXCtorVTable(RD, Base.getBaseOffset().getQuantity(), Base.getBase(),
680                        Out);
681  Out.flush();
682  StringRef Name = OutName.str();
683
684  llvm::ArrayType *ArrayType =
685    llvm::ArrayType::get(CGM.Int8PtrTy, VTLayout->getNumVTableComponents());
686
687  // Create the variable that will hold the construction vtable.
688  llvm::GlobalVariable *VTable =
689    CGM.CreateOrReplaceCXXRuntimeVariable(Name, ArrayType, Linkage);
690  CGM.setTypeVisibility(VTable, RD, CodeGenModule::TVK_ForConstructionVTable);
691
692  // V-tables are always unnamed_addr.
693  VTable->setUnnamedAddr(true);
694
695  // Create and set the initializer.
696  llvm::Constant *Init =
697    CreateVTableInitializer(Base.getBase(),
698                            VTLayout->vtable_component_begin(),
699                            VTLayout->getNumVTableComponents(),
700                            VTLayout->vtable_thunk_begin(),
701                            VTLayout->getNumVTableThunks());
702  VTable->setInitializer(Init);
703
704  return VTable;
705}
706
707void
708CodeGenVTables::GenerateClassData(llvm::GlobalVariable::LinkageTypes Linkage,
709                                  const CXXRecordDecl *RD) {
710  llvm::GlobalVariable *VTable = GetAddrOfVTable(RD);
711  if (VTable->hasInitializer())
712    return;
713
714  EmitVTableDefinition(VTable, Linkage, RD);
715
716  if (RD->getNumVBases()) {
717    llvm::GlobalVariable *VTT = GetAddrOfVTT(RD);
718    EmitVTTDefinition(VTT, Linkage, RD);
719  }
720
721  // If this is the magic class __cxxabiv1::__fundamental_type_info,
722  // we will emit the typeinfo for the fundamental types. This is the
723  // same behaviour as GCC.
724  const DeclContext *DC = RD->getDeclContext();
725  if (RD->getIdentifier() &&
726      RD->getIdentifier()->isStr("__fundamental_type_info") &&
727      isa<NamespaceDecl>(DC) &&
728      cast<NamespaceDecl>(DC)->getIdentifier() &&
729      cast<NamespaceDecl>(DC)->getIdentifier()->isStr("__cxxabiv1") &&
730      DC->getParent()->isTranslationUnit())
731    CGM.EmitFundamentalRTTIDescriptors();
732}
733