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 "CodeGenFunction.h"
15#include "CGCXXABI.h"
16#include "CodeGenModule.h"
17#include "clang/AST/CXXInheritance.h"
18#include "clang/AST/RecordLayout.h"
19#include "clang/CodeGen/CGFunctionInfo.h"
20#include "clang/Frontend/CodeGenOptions.h"
21#include "llvm/ADT/DenseSet.h"
22#include "llvm/ADT/SetVector.h"
23#include "llvm/Support/Compiler.h"
24#include "llvm/Support/Format.h"
25#include "llvm/Transforms/Utils/Cloning.h"
26#include <algorithm>
27#include <cstdio>
28
29using namespace clang;
30using namespace CodeGen;
31
32CodeGenVTables::CodeGenVTables(CodeGenModule &CGM)
33    : CGM(CGM), VTContext(CGM.getContext().getVTableContext()) {}
34
35llvm::Constant *CodeGenModule::GetAddrOfThunk(GlobalDecl GD,
36                                              const ThunkInfo &Thunk) {
37  const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
38
39  // Compute the mangled name.
40  SmallString<256> Name;
41  llvm::raw_svector_ostream Out(Name);
42  if (const CXXDestructorDecl* DD = dyn_cast<CXXDestructorDecl>(MD))
43    getCXXABI().getMangleContext().mangleCXXDtorThunk(DD, GD.getDtorType(),
44                                                      Thunk.This, Out);
45  else
46    getCXXABI().getMangleContext().mangleThunk(MD, Thunk, Out);
47
48  llvm::Type *Ty = getTypes().GetFunctionTypeForVTable(GD);
49  return GetOrCreateLLVMFunction(Name, Ty, GD, /*ForVTable=*/true,
50                                 /*DontDefer=*/true, /*IsThunk=*/true);
51}
52
53static void setThunkVisibility(CodeGenModule &CGM, const CXXMethodDecl *MD,
54                               const ThunkInfo &Thunk, llvm::Function *Fn) {
55  CGM.setGlobalVisibility(Fn, MD);
56}
57
58static void setThunkProperties(CodeGenModule &CGM, const ThunkInfo &Thunk,
59                               llvm::Function *ThunkFn, bool ForVTable,
60                               GlobalDecl GD) {
61  CGM.setFunctionLinkage(GD, ThunkFn);
62  CGM.getCXXABI().setThunkLinkage(ThunkFn, ForVTable, GD,
63                                  !Thunk.Return.isEmpty());
64
65  // Set the right visibility.
66  const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
67  setThunkVisibility(CGM, MD, Thunk, ThunkFn);
68
69  if (CGM.supportsCOMDAT() && ThunkFn->isWeakForLinker())
70    ThunkFn->setComdat(CGM.getModule().getOrInsertComdat(ThunkFn->getName()));
71}
72
73#ifndef NDEBUG
74static bool similar(const ABIArgInfo &infoL, CanQualType typeL,
75                    const ABIArgInfo &infoR, CanQualType typeR) {
76  return (infoL.getKind() == infoR.getKind() &&
77          (typeL == typeR ||
78           (isa<PointerType>(typeL) && isa<PointerType>(typeR)) ||
79           (isa<ReferenceType>(typeL) && isa<ReferenceType>(typeR))));
80}
81#endif
82
83static RValue PerformReturnAdjustment(CodeGenFunction &CGF,
84                                      QualType ResultType, RValue RV,
85                                      const ThunkInfo &Thunk) {
86  // Emit the return adjustment.
87  bool NullCheckValue = !ResultType->isReferenceType();
88
89  llvm::BasicBlock *AdjustNull = nullptr;
90  llvm::BasicBlock *AdjustNotNull = nullptr;
91  llvm::BasicBlock *AdjustEnd = nullptr;
92
93  llvm::Value *ReturnValue = RV.getScalarVal();
94
95  if (NullCheckValue) {
96    AdjustNull = CGF.createBasicBlock("adjust.null");
97    AdjustNotNull = CGF.createBasicBlock("adjust.notnull");
98    AdjustEnd = CGF.createBasicBlock("adjust.end");
99
100    llvm::Value *IsNull = CGF.Builder.CreateIsNull(ReturnValue);
101    CGF.Builder.CreateCondBr(IsNull, AdjustNull, AdjustNotNull);
102    CGF.EmitBlock(AdjustNotNull);
103  }
104
105  auto ClassDecl = ResultType->getPointeeType()->getAsCXXRecordDecl();
106  auto ClassAlign = CGF.CGM.getClassPointerAlignment(ClassDecl);
107  ReturnValue = CGF.CGM.getCXXABI().performReturnAdjustment(CGF,
108                                            Address(ReturnValue, ClassAlign),
109                                            Thunk.Return);
110
111  if (NullCheckValue) {
112    CGF.Builder.CreateBr(AdjustEnd);
113    CGF.EmitBlock(AdjustNull);
114    CGF.Builder.CreateBr(AdjustEnd);
115    CGF.EmitBlock(AdjustEnd);
116
117    llvm::PHINode *PHI = CGF.Builder.CreatePHI(ReturnValue->getType(), 2);
118    PHI->addIncoming(ReturnValue, AdjustNotNull);
119    PHI->addIncoming(llvm::Constant::getNullValue(ReturnValue->getType()),
120                     AdjustNull);
121    ReturnValue = PHI;
122  }
123
124  return RValue::get(ReturnValue);
125}
126
127// This function does roughly the same thing as GenerateThunk, but in a
128// very different way, so that va_start and va_end work correctly.
129// FIXME: This function assumes "this" is the first non-sret LLVM argument of
130//        a function, and that there is an alloca built in the entry block
131//        for all accesses to "this".
132// FIXME: This function assumes there is only one "ret" statement per function.
133// FIXME: Cloning isn't correct in the presence of indirect goto!
134// FIXME: This implementation of thunks bloats codesize by duplicating the
135//        function definition.  There are alternatives:
136//        1. Add some sort of stub support to LLVM for cases where we can
137//           do a this adjustment, then a sibcall.
138//        2. We could transform the definition to take a va_list instead of an
139//           actual variable argument list, then have the thunks (including a
140//           no-op thunk for the regular definition) call va_start/va_end.
141//           There's a bit of per-call overhead for this solution, but it's
142//           better for codesize if the definition is long.
143llvm::Function *
144CodeGenFunction::GenerateVarArgsThunk(llvm::Function *Fn,
145                                      const CGFunctionInfo &FnInfo,
146                                      GlobalDecl GD, const ThunkInfo &Thunk) {
147  const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
148  const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
149  QualType ResultType = FPT->getReturnType();
150
151  // Get the original function
152  assert(FnInfo.isVariadic());
153  llvm::Type *Ty = CGM.getTypes().GetFunctionType(FnInfo);
154  llvm::Value *Callee = CGM.GetAddrOfFunction(GD, Ty, /*ForVTable=*/true);
155  llvm::Function *BaseFn = cast<llvm::Function>(Callee);
156
157  // Clone to thunk.
158  llvm::ValueToValueMapTy VMap;
159  llvm::Function *NewFn = llvm::CloneFunction(BaseFn, VMap,
160                                              /*ModuleLevelChanges=*/false);
161  CGM.getModule().getFunctionList().push_back(NewFn);
162  Fn->replaceAllUsesWith(NewFn);
163  NewFn->takeName(Fn);
164  Fn->eraseFromParent();
165  Fn = NewFn;
166
167  // "Initialize" CGF (minimally).
168  CurFn = Fn;
169
170  // Get the "this" value
171  llvm::Function::arg_iterator AI = Fn->arg_begin();
172  if (CGM.ReturnTypeUsesSRet(FnInfo))
173    ++AI;
174
175  // Find the first store of "this", which will be to the alloca associated
176  // with "this".
177  Address ThisPtr(&*AI, CGM.getClassPointerAlignment(MD->getParent()));
178  llvm::BasicBlock *EntryBB = &Fn->front();
179  llvm::BasicBlock::iterator ThisStore =
180      std::find_if(EntryBB->begin(), EntryBB->end(), [&](llvm::Instruction &I) {
181        return isa<llvm::StoreInst>(I) &&
182               I.getOperand(0) == ThisPtr.getPointer();
183      });
184  assert(ThisStore != EntryBB->end() &&
185         "Store of this should be in entry block?");
186  // Adjust "this", if necessary.
187  Builder.SetInsertPoint(&*ThisStore);
188  llvm::Value *AdjustedThisPtr =
189      CGM.getCXXABI().performThisAdjustment(*this, ThisPtr, Thunk.This);
190  ThisStore->setOperand(0, AdjustedThisPtr);
191
192  if (!Thunk.Return.isEmpty()) {
193    // Fix up the returned value, if necessary.
194    for (llvm::BasicBlock &BB : *Fn) {
195      llvm::Instruction *T = BB.getTerminator();
196      if (isa<llvm::ReturnInst>(T)) {
197        RValue RV = RValue::get(T->getOperand(0));
198        T->eraseFromParent();
199        Builder.SetInsertPoint(&BB);
200        RV = PerformReturnAdjustment(*this, ResultType, RV, Thunk);
201        Builder.CreateRet(RV.getScalarVal());
202        break;
203      }
204    }
205  }
206
207  return Fn;
208}
209
210void CodeGenFunction::StartThunk(llvm::Function *Fn, GlobalDecl GD,
211                                 const CGFunctionInfo &FnInfo) {
212  assert(!CurGD.getDecl() && "CurGD was already set!");
213  CurGD = GD;
214  CurFuncIsThunk = true;
215
216  // Build FunctionArgs.
217  const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
218  QualType ThisType = MD->getThisType(getContext());
219  const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
220  QualType ResultType = CGM.getCXXABI().HasThisReturn(GD)
221                            ? ThisType
222                            : CGM.getCXXABI().hasMostDerivedReturn(GD)
223                                  ? CGM.getContext().VoidPtrTy
224                                  : FPT->getReturnType();
225  FunctionArgList FunctionArgs;
226
227  // Create the implicit 'this' parameter declaration.
228  CGM.getCXXABI().buildThisParam(*this, FunctionArgs);
229
230  // Add the rest of the parameters.
231  FunctionArgs.append(MD->param_begin(), MD->param_end());
232
233  if (isa<CXXDestructorDecl>(MD))
234    CGM.getCXXABI().addImplicitStructorParams(*this, ResultType, FunctionArgs);
235
236  // Start defining the function.
237  StartFunction(GlobalDecl(), ResultType, Fn, FnInfo, FunctionArgs,
238                MD->getLocation(), MD->getLocation());
239
240  // Since we didn't pass a GlobalDecl to StartFunction, do this ourselves.
241  CGM.getCXXABI().EmitInstanceFunctionProlog(*this);
242  CXXThisValue = CXXABIThisValue;
243  CurCodeDecl = MD;
244  CurFuncDecl = MD;
245}
246
247void CodeGenFunction::FinishThunk() {
248  // Clear these to restore the invariants expected by
249  // StartFunction/FinishFunction.
250  CurCodeDecl = nullptr;
251  CurFuncDecl = nullptr;
252
253  FinishFunction();
254}
255
256void CodeGenFunction::EmitCallAndReturnForThunk(llvm::Value *Callee,
257                                                const ThunkInfo *Thunk) {
258  assert(isa<CXXMethodDecl>(CurGD.getDecl()) &&
259         "Please use a new CGF for this thunk");
260  const CXXMethodDecl *MD = cast<CXXMethodDecl>(CurGD.getDecl());
261
262  // Adjust the 'this' pointer if necessary
263  llvm::Value *AdjustedThisPtr =
264    Thunk ? CGM.getCXXABI().performThisAdjustment(
265                          *this, LoadCXXThisAddress(), Thunk->This)
266          : LoadCXXThis();
267
268  if (CurFnInfo->usesInAlloca()) {
269    // We don't handle return adjusting thunks, because they require us to call
270    // the copy constructor.  For now, fall through and pretend the return
271    // adjustment was empty so we don't crash.
272    if (Thunk && !Thunk->Return.isEmpty()) {
273      CGM.ErrorUnsupported(
274          MD, "non-trivial argument copy for return-adjusting thunk");
275    }
276    EmitMustTailThunk(MD, AdjustedThisPtr, Callee);
277    return;
278  }
279
280  // Start building CallArgs.
281  CallArgList CallArgs;
282  QualType ThisType = MD->getThisType(getContext());
283  CallArgs.add(RValue::get(AdjustedThisPtr), ThisType);
284
285  if (isa<CXXDestructorDecl>(MD))
286    CGM.getCXXABI().adjustCallArgsForDestructorThunk(*this, CurGD, CallArgs);
287
288  // Add the rest of the arguments.
289  for (const ParmVarDecl *PD : MD->params())
290    EmitDelegateCallArg(CallArgs, PD, PD->getLocStart());
291
292  const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
293
294#ifndef NDEBUG
295  const CGFunctionInfo &CallFnInfo =
296    CGM.getTypes().arrangeCXXMethodCall(CallArgs, FPT,
297                                       RequiredArgs::forPrototypePlus(FPT, 1));
298  assert(CallFnInfo.getRegParm() == CurFnInfo->getRegParm() &&
299         CallFnInfo.isNoReturn() == CurFnInfo->isNoReturn() &&
300         CallFnInfo.getCallingConvention() == CurFnInfo->getCallingConvention());
301  assert(isa<CXXDestructorDecl>(MD) || // ignore dtor return types
302         similar(CallFnInfo.getReturnInfo(), CallFnInfo.getReturnType(),
303                 CurFnInfo->getReturnInfo(), CurFnInfo->getReturnType()));
304  assert(CallFnInfo.arg_size() == CurFnInfo->arg_size());
305  for (unsigned i = 0, e = CurFnInfo->arg_size(); i != e; ++i)
306    assert(similar(CallFnInfo.arg_begin()[i].info,
307                   CallFnInfo.arg_begin()[i].type,
308                   CurFnInfo->arg_begin()[i].info,
309                   CurFnInfo->arg_begin()[i].type));
310#endif
311
312  // Determine whether we have a return value slot to use.
313  QualType ResultType = CGM.getCXXABI().HasThisReturn(CurGD)
314                            ? ThisType
315                            : CGM.getCXXABI().hasMostDerivedReturn(CurGD)
316                                  ? CGM.getContext().VoidPtrTy
317                                  : FPT->getReturnType();
318  ReturnValueSlot Slot;
319  if (!ResultType->isVoidType() &&
320      CurFnInfo->getReturnInfo().getKind() == ABIArgInfo::Indirect &&
321      !hasScalarEvaluationKind(CurFnInfo->getReturnType()))
322    Slot = ReturnValueSlot(ReturnValue, ResultType.isVolatileQualified());
323
324  // Now emit our call.
325  llvm::Instruction *CallOrInvoke;
326  RValue RV = EmitCall(*CurFnInfo, Callee, Slot, CallArgs, MD, &CallOrInvoke);
327
328  // Consider return adjustment if we have ThunkInfo.
329  if (Thunk && !Thunk->Return.isEmpty())
330    RV = PerformReturnAdjustment(*this, ResultType, RV, *Thunk);
331  else if (llvm::CallInst* Call = dyn_cast<llvm::CallInst>(CallOrInvoke))
332    Call->setTailCallKind(llvm::CallInst::TCK_Tail);
333
334  // Emit return.
335  if (!ResultType->isVoidType() && Slot.isNull())
336    CGM.getCXXABI().EmitReturnFromThunk(*this, RV, ResultType);
337
338  // Disable the final ARC autorelease.
339  AutoreleaseResult = false;
340
341  FinishThunk();
342}
343
344void CodeGenFunction::EmitMustTailThunk(const CXXMethodDecl *MD,
345                                        llvm::Value *AdjustedThisPtr,
346                                        llvm::Value *Callee) {
347  // Emitting a musttail call thunk doesn't use any of the CGCall.cpp machinery
348  // to translate AST arguments into LLVM IR arguments.  For thunks, we know
349  // that the caller prototype more or less matches the callee prototype with
350  // the exception of 'this'.
351  SmallVector<llvm::Value *, 8> Args;
352  for (llvm::Argument &A : CurFn->args())
353    Args.push_back(&A);
354
355  // Set the adjusted 'this' pointer.
356  const ABIArgInfo &ThisAI = CurFnInfo->arg_begin()->info;
357  if (ThisAI.isDirect()) {
358    const ABIArgInfo &RetAI = CurFnInfo->getReturnInfo();
359    int ThisArgNo = RetAI.isIndirect() && !RetAI.isSRetAfterThis() ? 1 : 0;
360    llvm::Type *ThisType = Args[ThisArgNo]->getType();
361    if (ThisType != AdjustedThisPtr->getType())
362      AdjustedThisPtr = Builder.CreateBitCast(AdjustedThisPtr, ThisType);
363    Args[ThisArgNo] = AdjustedThisPtr;
364  } else {
365    assert(ThisAI.isInAlloca() && "this is passed directly or inalloca");
366    Address ThisAddr = GetAddrOfLocalVar(CXXABIThisDecl);
367    llvm::Type *ThisType = ThisAddr.getElementType();
368    if (ThisType != AdjustedThisPtr->getType())
369      AdjustedThisPtr = Builder.CreateBitCast(AdjustedThisPtr, ThisType);
370    Builder.CreateStore(AdjustedThisPtr, ThisAddr);
371  }
372
373  // Emit the musttail call manually.  Even if the prologue pushed cleanups, we
374  // don't actually want to run them.
375  llvm::CallInst *Call = Builder.CreateCall(Callee, Args);
376  Call->setTailCallKind(llvm::CallInst::TCK_MustTail);
377
378  // Apply the standard set of call attributes.
379  unsigned CallingConv;
380  CodeGen::AttributeListType AttributeList;
381  CGM.ConstructAttributeList(Callee->getName(), *CurFnInfo, MD, AttributeList,
382                             CallingConv, /*AttrOnCallSite=*/true);
383  llvm::AttributeSet Attrs =
384      llvm::AttributeSet::get(getLLVMContext(), AttributeList);
385  Call->setAttributes(Attrs);
386  Call->setCallingConv(static_cast<llvm::CallingConv::ID>(CallingConv));
387
388  if (Call->getType()->isVoidTy())
389    Builder.CreateRetVoid();
390  else
391    Builder.CreateRet(Call);
392
393  // Finish the function to maintain CodeGenFunction invariants.
394  // FIXME: Don't emit unreachable code.
395  EmitBlock(createBasicBlock());
396  FinishFunction();
397}
398
399void CodeGenFunction::generateThunk(llvm::Function *Fn,
400                                    const CGFunctionInfo &FnInfo,
401                                    GlobalDecl GD, const ThunkInfo &Thunk) {
402  StartThunk(Fn, GD, FnInfo);
403
404  // Get our callee.
405  llvm::Type *Ty =
406    CGM.getTypes().GetFunctionType(CGM.getTypes().arrangeGlobalDeclaration(GD));
407  llvm::Value *Callee = CGM.GetAddrOfFunction(GD, Ty, /*ForVTable=*/true);
408
409  // Make the call and return the result.
410  EmitCallAndReturnForThunk(Callee, &Thunk);
411}
412
413void CodeGenVTables::emitThunk(GlobalDecl GD, const ThunkInfo &Thunk,
414                               bool ForVTable) {
415  const CGFunctionInfo &FnInfo = CGM.getTypes().arrangeGlobalDeclaration(GD);
416
417  // FIXME: re-use FnInfo in this computation.
418  llvm::Constant *C = CGM.GetAddrOfThunk(GD, Thunk);
419  llvm::GlobalValue *Entry;
420
421  // Strip off a bitcast if we got one back.
422  if (llvm::ConstantExpr *CE = dyn_cast<llvm::ConstantExpr>(C)) {
423    assert(CE->getOpcode() == llvm::Instruction::BitCast);
424    Entry = cast<llvm::GlobalValue>(CE->getOperand(0));
425  } else {
426    Entry = cast<llvm::GlobalValue>(C);
427  }
428
429  // There's already a declaration with the same name, check if it has the same
430  // type or if we need to replace it.
431  if (Entry->getType()->getElementType() !=
432      CGM.getTypes().GetFunctionTypeForVTable(GD)) {
433    llvm::GlobalValue *OldThunkFn = Entry;
434
435    // If the types mismatch then we have to rewrite the definition.
436    assert(OldThunkFn->isDeclaration() &&
437           "Shouldn't replace non-declaration");
438
439    // Remove the name from the old thunk function and get a new thunk.
440    OldThunkFn->setName(StringRef());
441    Entry = cast<llvm::GlobalValue>(CGM.GetAddrOfThunk(GD, Thunk));
442
443    // If needed, replace the old thunk with a bitcast.
444    if (!OldThunkFn->use_empty()) {
445      llvm::Constant *NewPtrForOldDecl =
446        llvm::ConstantExpr::getBitCast(Entry, OldThunkFn->getType());
447      OldThunkFn->replaceAllUsesWith(NewPtrForOldDecl);
448    }
449
450    // Remove the old thunk.
451    OldThunkFn->eraseFromParent();
452  }
453
454  llvm::Function *ThunkFn = cast<llvm::Function>(Entry);
455  bool ABIHasKeyFunctions = CGM.getTarget().getCXXABI().hasKeyFunctions();
456  bool UseAvailableExternallyLinkage = ForVTable && ABIHasKeyFunctions;
457
458  if (!ThunkFn->isDeclaration()) {
459    if (!ABIHasKeyFunctions || UseAvailableExternallyLinkage) {
460      // There is already a thunk emitted for this function, do nothing.
461      return;
462    }
463
464    setThunkProperties(CGM, Thunk, ThunkFn, ForVTable, GD);
465    return;
466  }
467
468  CGM.SetLLVMFunctionAttributesForDefinition(GD.getDecl(), ThunkFn);
469
470  if (ThunkFn->isVarArg()) {
471    // Varargs thunks are special; we can't just generate a call because
472    // we can't copy the varargs.  Our implementation is rather
473    // expensive/sucky at the moment, so don't generate the thunk unless
474    // we have to.
475    // FIXME: Do something better here; GenerateVarArgsThunk is extremely ugly.
476    if (UseAvailableExternallyLinkage)
477      return;
478    ThunkFn =
479        CodeGenFunction(CGM).GenerateVarArgsThunk(ThunkFn, FnInfo, GD, Thunk);
480  } else {
481    // Normal thunk body generation.
482    CodeGenFunction(CGM).generateThunk(ThunkFn, FnInfo, GD, Thunk);
483  }
484
485  setThunkProperties(CGM, Thunk, ThunkFn, ForVTable, GD);
486}
487
488void CodeGenVTables::maybeEmitThunkForVTable(GlobalDecl GD,
489                                             const ThunkInfo &Thunk) {
490  // If the ABI has key functions, only the TU with the key function should emit
491  // the thunk. However, we can allow inlining of thunks if we emit them with
492  // available_externally linkage together with vtables when optimizations are
493  // enabled.
494  if (CGM.getTarget().getCXXABI().hasKeyFunctions() &&
495      !CGM.getCodeGenOpts().OptimizationLevel)
496    return;
497
498  // We can't emit thunks for member functions with incomplete types.
499  const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
500  if (!CGM.getTypes().isFuncTypeConvertible(
501           MD->getType()->castAs<FunctionType>()))
502    return;
503
504  emitThunk(GD, Thunk, /*ForVTable=*/true);
505}
506
507void CodeGenVTables::EmitThunks(GlobalDecl GD)
508{
509  const CXXMethodDecl *MD =
510    cast<CXXMethodDecl>(GD.getDecl())->getCanonicalDecl();
511
512  // We don't need to generate thunks for the base destructor.
513  if (isa<CXXDestructorDecl>(MD) && GD.getDtorType() == Dtor_Base)
514    return;
515
516  const VTableContextBase::ThunkInfoVectorTy *ThunkInfoVector =
517      VTContext->getThunkInfo(GD);
518
519  if (!ThunkInfoVector)
520    return;
521
522  for (const ThunkInfo& Thunk : *ThunkInfoVector)
523    emitThunk(GD, Thunk, /*ForVTable=*/false);
524}
525
526llvm::Constant *CodeGenVTables::CreateVTableInitializer(
527    const CXXRecordDecl *RD, const VTableComponent *Components,
528    unsigned NumComponents, const VTableLayout::VTableThunkTy *VTableThunks,
529    unsigned NumVTableThunks, llvm::Constant *RTTI) {
530  SmallVector<llvm::Constant *, 64> Inits;
531
532  llvm::Type *Int8PtrTy = CGM.Int8PtrTy;
533
534  llvm::Type *PtrDiffTy =
535    CGM.getTypes().ConvertType(CGM.getContext().getPointerDiffType());
536
537  unsigned NextVTableThunkIndex = 0;
538
539  llvm::Constant *PureVirtualFn = nullptr, *DeletedVirtualFn = nullptr;
540
541  for (unsigned I = 0; I != NumComponents; ++I) {
542    VTableComponent Component = Components[I];
543
544    llvm::Constant *Init = nullptr;
545
546    switch (Component.getKind()) {
547    case VTableComponent::CK_VCallOffset:
548      Init = llvm::ConstantInt::get(PtrDiffTy,
549                                    Component.getVCallOffset().getQuantity());
550      Init = llvm::ConstantExpr::getIntToPtr(Init, Int8PtrTy);
551      break;
552    case VTableComponent::CK_VBaseOffset:
553      Init = llvm::ConstantInt::get(PtrDiffTy,
554                                    Component.getVBaseOffset().getQuantity());
555      Init = llvm::ConstantExpr::getIntToPtr(Init, Int8PtrTy);
556      break;
557    case VTableComponent::CK_OffsetToTop:
558      Init = llvm::ConstantInt::get(PtrDiffTy,
559                                    Component.getOffsetToTop().getQuantity());
560      Init = llvm::ConstantExpr::getIntToPtr(Init, Int8PtrTy);
561      break;
562    case VTableComponent::CK_RTTI:
563      Init = llvm::ConstantExpr::getBitCast(RTTI, Int8PtrTy);
564      break;
565    case VTableComponent::CK_FunctionPointer:
566    case VTableComponent::CK_CompleteDtorPointer:
567    case VTableComponent::CK_DeletingDtorPointer: {
568      GlobalDecl GD;
569
570      // Get the right global decl.
571      switch (Component.getKind()) {
572      default:
573        llvm_unreachable("Unexpected vtable component kind");
574      case VTableComponent::CK_FunctionPointer:
575        GD = Component.getFunctionDecl();
576        break;
577      case VTableComponent::CK_CompleteDtorPointer:
578        GD = GlobalDecl(Component.getDestructorDecl(), Dtor_Complete);
579        break;
580      case VTableComponent::CK_DeletingDtorPointer:
581        GD = GlobalDecl(Component.getDestructorDecl(), Dtor_Deleting);
582        break;
583      }
584
585      if (CGM.getLangOpts().CUDA) {
586        // Emit NULL for methods we can't codegen on this
587        // side. Otherwise we'd end up with vtable with unresolved
588        // references.
589        const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
590        // OK on device side: functions w/ __device__ attribute
591        // OK on host side: anything except __device__-only functions.
592        bool CanEmitMethod = CGM.getLangOpts().CUDAIsDevice
593                                 ? MD->hasAttr<CUDADeviceAttr>()
594                                 : (MD->hasAttr<CUDAHostAttr>() ||
595                                    !MD->hasAttr<CUDADeviceAttr>());
596        if (!CanEmitMethod) {
597          Init = llvm::ConstantExpr::getNullValue(Int8PtrTy);
598          break;
599        }
600        // Method is acceptable, continue processing as usual.
601      }
602
603      if (cast<CXXMethodDecl>(GD.getDecl())->isPure()) {
604        // We have a pure virtual member function.
605        if (!PureVirtualFn) {
606          llvm::FunctionType *Ty =
607            llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false);
608          StringRef PureCallName = CGM.getCXXABI().GetPureVirtualCallName();
609          PureVirtualFn = CGM.CreateRuntimeFunction(Ty, PureCallName);
610          PureVirtualFn = llvm::ConstantExpr::getBitCast(PureVirtualFn,
611                                                         CGM.Int8PtrTy);
612        }
613        Init = PureVirtualFn;
614      } else if (cast<CXXMethodDecl>(GD.getDecl())->isDeleted()) {
615        if (!DeletedVirtualFn) {
616          llvm::FunctionType *Ty =
617            llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false);
618          StringRef DeletedCallName =
619            CGM.getCXXABI().GetDeletedVirtualCallName();
620          DeletedVirtualFn = CGM.CreateRuntimeFunction(Ty, DeletedCallName);
621          DeletedVirtualFn = llvm::ConstantExpr::getBitCast(DeletedVirtualFn,
622                                                         CGM.Int8PtrTy);
623        }
624        Init = DeletedVirtualFn;
625      } else {
626        // Check if we should use a thunk.
627        if (NextVTableThunkIndex < NumVTableThunks &&
628            VTableThunks[NextVTableThunkIndex].first == I) {
629          const ThunkInfo &Thunk = VTableThunks[NextVTableThunkIndex].second;
630
631          maybeEmitThunkForVTable(GD, Thunk);
632          Init = CGM.GetAddrOfThunk(GD, Thunk);
633
634          NextVTableThunkIndex++;
635        } else {
636          llvm::Type *Ty = CGM.getTypes().GetFunctionTypeForVTable(GD);
637
638          Init = CGM.GetAddrOfFunction(GD, Ty, /*ForVTable=*/true);
639        }
640
641        Init = llvm::ConstantExpr::getBitCast(Init, Int8PtrTy);
642      }
643      break;
644    }
645
646    case VTableComponent::CK_UnusedFunctionPointer:
647      Init = llvm::ConstantExpr::getNullValue(Int8PtrTy);
648      break;
649    };
650
651    Inits.push_back(Init);
652  }
653
654  llvm::ArrayType *ArrayType = llvm::ArrayType::get(Int8PtrTy, NumComponents);
655  return llvm::ConstantArray::get(ArrayType, Inits);
656}
657
658llvm::GlobalVariable *
659CodeGenVTables::GenerateConstructionVTable(const CXXRecordDecl *RD,
660                                      const BaseSubobject &Base,
661                                      bool BaseIsVirtual,
662                                   llvm::GlobalVariable::LinkageTypes Linkage,
663                                      VTableAddressPointsMapTy& AddressPoints) {
664  if (CGDebugInfo *DI = CGM.getModuleDebugInfo())
665    DI->completeClassData(Base.getBase());
666
667  std::unique_ptr<VTableLayout> VTLayout(
668      getItaniumVTableContext().createConstructionVTableLayout(
669          Base.getBase(), Base.getBaseOffset(), BaseIsVirtual, RD));
670
671  // Add the address points.
672  AddressPoints = VTLayout->getAddressPoints();
673
674  // Get the mangled construction vtable name.
675  SmallString<256> OutName;
676  llvm::raw_svector_ostream Out(OutName);
677  cast<ItaniumMangleContext>(CGM.getCXXABI().getMangleContext())
678      .mangleCXXCtorVTable(RD, Base.getBaseOffset().getQuantity(),
679                           Base.getBase(), Out);
680  StringRef Name = OutName.str();
681
682  llvm::ArrayType *ArrayType =
683    llvm::ArrayType::get(CGM.Int8PtrTy, VTLayout->getNumVTableComponents());
684
685  // Construction vtable symbols are not part of the Itanium ABI, so we cannot
686  // guarantee that they actually will be available externally. Instead, when
687  // emitting an available_externally VTT, we provide references to an internal
688  // linkage construction vtable. The ABI only requires complete-object vtables
689  // to be the same for all instances of a type, not construction vtables.
690  if (Linkage == llvm::GlobalVariable::AvailableExternallyLinkage)
691    Linkage = llvm::GlobalVariable::InternalLinkage;
692
693  // Create the variable that will hold the construction vtable.
694  llvm::GlobalVariable *VTable =
695    CGM.CreateOrReplaceCXXRuntimeVariable(Name, ArrayType, Linkage);
696  CGM.setGlobalVisibility(VTable, RD);
697
698  // V-tables are always unnamed_addr.
699  VTable->setUnnamedAddr(true);
700
701  llvm::Constant *RTTI = CGM.GetAddrOfRTTIDescriptor(
702      CGM.getContext().getTagDeclType(Base.getBase()));
703
704  // Create and set the initializer.
705  llvm::Constant *Init = CreateVTableInitializer(
706      Base.getBase(), VTLayout->vtable_component_begin(),
707      VTLayout->getNumVTableComponents(), VTLayout->vtable_thunk_begin(),
708      VTLayout->getNumVTableThunks(), RTTI);
709  VTable->setInitializer(Init);
710
711  CGM.EmitVTableBitSetEntries(VTable, *VTLayout.get());
712
713  return VTable;
714}
715
716static bool shouldEmitAvailableExternallyVTable(const CodeGenModule &CGM,
717                                                const CXXRecordDecl *RD) {
718  return CGM.getCodeGenOpts().OptimizationLevel > 0 &&
719         CGM.getCXXABI().canSpeculativelyEmitVTable(RD);
720}
721
722/// Compute the required linkage of the v-table for the given class.
723///
724/// Note that we only call this at the end of the translation unit.
725llvm::GlobalVariable::LinkageTypes
726CodeGenModule::getVTableLinkage(const CXXRecordDecl *RD) {
727  if (!RD->isExternallyVisible())
728    return llvm::GlobalVariable::InternalLinkage;
729
730  // We're at the end of the translation unit, so the current key
731  // function is fully correct.
732  const CXXMethodDecl *keyFunction = Context.getCurrentKeyFunction(RD);
733  if (keyFunction && !RD->hasAttr<DLLImportAttr>()) {
734    // If this class has a key function, use that to determine the
735    // linkage of the vtable.
736    const FunctionDecl *def = nullptr;
737    if (keyFunction->hasBody(def))
738      keyFunction = cast<CXXMethodDecl>(def);
739
740    switch (keyFunction->getTemplateSpecializationKind()) {
741      case TSK_Undeclared:
742      case TSK_ExplicitSpecialization:
743        assert((def || CodeGenOpts.OptimizationLevel > 0) &&
744               "Shouldn't query vtable linkage without key function or "
745               "optimizations");
746        if (!def && CodeGenOpts.OptimizationLevel > 0)
747          return llvm::GlobalVariable::AvailableExternallyLinkage;
748
749        if (keyFunction->isInlined())
750          return !Context.getLangOpts().AppleKext ?
751                   llvm::GlobalVariable::LinkOnceODRLinkage :
752                   llvm::Function::InternalLinkage;
753
754        return llvm::GlobalVariable::ExternalLinkage;
755
756      case TSK_ImplicitInstantiation:
757        return !Context.getLangOpts().AppleKext ?
758                 llvm::GlobalVariable::LinkOnceODRLinkage :
759                 llvm::Function::InternalLinkage;
760
761      case TSK_ExplicitInstantiationDefinition:
762        return !Context.getLangOpts().AppleKext ?
763                 llvm::GlobalVariable::WeakODRLinkage :
764                 llvm::Function::InternalLinkage;
765
766      case TSK_ExplicitInstantiationDeclaration:
767        llvm_unreachable("Should not have been asked to emit this");
768    }
769  }
770
771  // -fapple-kext mode does not support weak linkage, so we must use
772  // internal linkage.
773  if (Context.getLangOpts().AppleKext)
774    return llvm::Function::InternalLinkage;
775
776  llvm::GlobalVariable::LinkageTypes DiscardableODRLinkage =
777      llvm::GlobalValue::LinkOnceODRLinkage;
778  llvm::GlobalVariable::LinkageTypes NonDiscardableODRLinkage =
779      llvm::GlobalValue::WeakODRLinkage;
780  if (RD->hasAttr<DLLExportAttr>()) {
781    // Cannot discard exported vtables.
782    DiscardableODRLinkage = NonDiscardableODRLinkage;
783  } else if (RD->hasAttr<DLLImportAttr>()) {
784    // Imported vtables are available externally.
785    DiscardableODRLinkage = llvm::GlobalVariable::AvailableExternallyLinkage;
786    NonDiscardableODRLinkage = llvm::GlobalVariable::AvailableExternallyLinkage;
787  }
788
789  switch (RD->getTemplateSpecializationKind()) {
790    case TSK_Undeclared:
791    case TSK_ExplicitSpecialization:
792    case TSK_ImplicitInstantiation:
793      return DiscardableODRLinkage;
794
795    case TSK_ExplicitInstantiationDeclaration:
796      return shouldEmitAvailableExternallyVTable(*this, RD)
797                 ? llvm::GlobalVariable::AvailableExternallyLinkage
798                 : llvm::GlobalVariable::ExternalLinkage;
799
800    case TSK_ExplicitInstantiationDefinition:
801      return NonDiscardableODRLinkage;
802  }
803
804  llvm_unreachable("Invalid TemplateSpecializationKind!");
805}
806
807/// This is a callback from Sema to tell us that that a particular v-table is
808/// required to be emitted in this translation unit.
809///
810/// This is only called for vtables that _must_ be emitted (mainly due to key
811/// functions).  For weak vtables, CodeGen tracks when they are needed and
812/// emits them as-needed.
813void CodeGenModule::EmitVTable(CXXRecordDecl *theClass) {
814  VTables.GenerateClassData(theClass);
815}
816
817void
818CodeGenVTables::GenerateClassData(const CXXRecordDecl *RD) {
819  if (CGDebugInfo *DI = CGM.getModuleDebugInfo())
820    DI->completeClassData(RD);
821
822  if (RD->getNumVBases())
823    CGM.getCXXABI().emitVirtualInheritanceTables(RD);
824
825  CGM.getCXXABI().emitVTableDefinitions(*this, RD);
826}
827
828/// At this point in the translation unit, does it appear that can we
829/// rely on the vtable being defined elsewhere in the program?
830///
831/// The response is really only definitive when called at the end of
832/// the translation unit.
833///
834/// The only semantic restriction here is that the object file should
835/// not contain a v-table definition when that v-table is defined
836/// strongly elsewhere.  Otherwise, we'd just like to avoid emitting
837/// v-tables when unnecessary.
838bool CodeGenVTables::isVTableExternal(const CXXRecordDecl *RD) {
839  assert(RD->isDynamicClass() && "Non-dynamic classes have no VTable.");
840
841  // If we have an explicit instantiation declaration (and not a
842  // definition), the v-table is defined elsewhere.
843  TemplateSpecializationKind TSK = RD->getTemplateSpecializationKind();
844  if (TSK == TSK_ExplicitInstantiationDeclaration)
845    return true;
846
847  // Otherwise, if the class is an instantiated template, the
848  // v-table must be defined here.
849  if (TSK == TSK_ImplicitInstantiation ||
850      TSK == TSK_ExplicitInstantiationDefinition)
851    return false;
852
853  // Otherwise, if the class doesn't have a key function (possibly
854  // anymore), the v-table must be defined here.
855  const CXXMethodDecl *keyFunction = CGM.getContext().getCurrentKeyFunction(RD);
856  if (!keyFunction)
857    return false;
858
859  // Otherwise, if we don't have a definition of the key function, the
860  // v-table must be defined somewhere else.
861  return !keyFunction->hasBody();
862}
863
864/// Given that we're currently at the end of the translation unit, and
865/// we've emitted a reference to the v-table for this class, should
866/// we define that v-table?
867static bool shouldEmitVTableAtEndOfTranslationUnit(CodeGenModule &CGM,
868                                                   const CXXRecordDecl *RD) {
869  // If vtable is internal then it has to be done.
870  if (!CGM.getVTables().isVTableExternal(RD))
871    return true;
872
873  // If it's external then maybe we will need it as available_externally.
874  return shouldEmitAvailableExternallyVTable(CGM, RD);
875}
876
877/// Given that at some point we emitted a reference to one or more
878/// v-tables, and that we are now at the end of the translation unit,
879/// decide whether we should emit them.
880void CodeGenModule::EmitDeferredVTables() {
881#ifndef NDEBUG
882  // Remember the size of DeferredVTables, because we're going to assume
883  // that this entire operation doesn't modify it.
884  size_t savedSize = DeferredVTables.size();
885#endif
886
887  for (const CXXRecordDecl *RD : DeferredVTables)
888    if (shouldEmitVTableAtEndOfTranslationUnit(*this, RD))
889      VTables.GenerateClassData(RD);
890
891  assert(savedSize == DeferredVTables.size() &&
892         "deferred extra v-tables during v-table emission?");
893  DeferredVTables.clear();
894}
895
896bool CodeGenModule::IsCFIBlacklistedRecord(const CXXRecordDecl *RD) {
897  if (RD->hasAttr<UuidAttr>() &&
898      getContext().getSanitizerBlacklist().isBlacklistedType("attr:uuid"))
899    return true;
900
901  return getContext().getSanitizerBlacklist().isBlacklistedType(
902      RD->getQualifiedNameAsString());
903}
904
905void CodeGenModule::EmitVTableBitSetEntries(llvm::GlobalVariable *VTable,
906                                            const VTableLayout &VTLayout) {
907  if (!LangOpts.Sanitize.has(SanitizerKind::CFIVCall) &&
908      !LangOpts.Sanitize.has(SanitizerKind::CFINVCall) &&
909      !LangOpts.Sanitize.has(SanitizerKind::CFIDerivedCast) &&
910      !LangOpts.Sanitize.has(SanitizerKind::CFIUnrelatedCast))
911    return;
912
913  CharUnits PointerWidth =
914      Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
915
916  typedef std::pair<const CXXRecordDecl *, unsigned> BSEntry;
917  std::vector<BSEntry> BitsetEntries;
918  // Create a bit set entry for each address point.
919  for (auto &&AP : VTLayout.getAddressPoints()) {
920    if (IsCFIBlacklistedRecord(AP.first.getBase()))
921      continue;
922
923    BitsetEntries.push_back(std::make_pair(AP.first.getBase(), AP.second));
924  }
925
926  // Sort the bit set entries for determinism.
927  std::sort(BitsetEntries.begin(), BitsetEntries.end(),
928            [this](const BSEntry &E1, const BSEntry &E2) {
929    if (&E1 == &E2)
930      return false;
931
932    std::string S1;
933    llvm::raw_string_ostream O1(S1);
934    getCXXABI().getMangleContext().mangleTypeName(
935        QualType(E1.first->getTypeForDecl(), 0), O1);
936    O1.flush();
937
938    std::string S2;
939    llvm::raw_string_ostream O2(S2);
940    getCXXABI().getMangleContext().mangleTypeName(
941        QualType(E2.first->getTypeForDecl(), 0), O2);
942    O2.flush();
943
944    if (S1 < S2)
945      return true;
946    if (S1 != S2)
947      return false;
948
949    return E1.second < E2.second;
950  });
951
952  llvm::NamedMDNode *BitsetsMD =
953      getModule().getOrInsertNamedMetadata("llvm.bitsets");
954  for (auto BitsetEntry : BitsetEntries)
955    CreateVTableBitSetEntry(BitsetsMD, VTable,
956                            PointerWidth * BitsetEntry.second,
957                            BitsetEntry.first);
958}
959