1 //===--- CGVTables.cpp - Emit LLVM Code for C++ vtables -------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This contains code dealing with C++ code generation of virtual tables.
12 //===----------------------------------------------------------------------===//
15 #include "CodeGenFunction.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/CodeGen/ConstantInitBuilder.h"
21 #include "clang/Frontend/CodeGenOptions.h"
22 #include "llvm/IR/IntrinsicInst.h"
23 #include "llvm/Support/Format.h"
24 #include "llvm/Transforms/Utils/Cloning.h"
28 using namespace clang;
29 using namespace CodeGen;
31 CodeGenVTables::CodeGenVTables(CodeGenModule &CGM)
32 : CGM(CGM), VTContext(CGM.getContext().getVTableContext()) {}
34 llvm::Constant *CodeGenModule::GetAddrOfThunk(StringRef Name, llvm::Type *FnTy,
36 return GetOrCreateLLVMFunction(Name, FnTy, GD, /*ForVTable=*/true,
37 /*DontDefer=*/true, /*IsThunk=*/true);
40 static void setThunkProperties(CodeGenModule &CGM, const ThunkInfo &Thunk,
41 llvm::Function *ThunkFn, bool ForVTable,
43 CGM.setFunctionLinkage(GD, ThunkFn);
44 CGM.getCXXABI().setThunkLinkage(ThunkFn, ForVTable, GD,
45 !Thunk.Return.isEmpty());
47 // Set the right visibility.
48 CGM.setGVProperties(ThunkFn, GD);
50 if (!CGM.getCXXABI().exportThunk()) {
51 ThunkFn->setDLLStorageClass(llvm::GlobalValue::DefaultStorageClass);
52 ThunkFn->setDSOLocal(true);
55 if (CGM.supportsCOMDAT() && ThunkFn->isWeakForLinker())
56 ThunkFn->setComdat(CGM.getModule().getOrInsertComdat(ThunkFn->getName()));
60 static bool similar(const ABIArgInfo &infoL, CanQualType typeL,
61 const ABIArgInfo &infoR, CanQualType typeR) {
62 return (infoL.getKind() == infoR.getKind() &&
64 (isa<PointerType>(typeL) && isa<PointerType>(typeR)) ||
65 (isa<ReferenceType>(typeL) && isa<ReferenceType>(typeR))));
69 static RValue PerformReturnAdjustment(CodeGenFunction &CGF,
70 QualType ResultType, RValue RV,
71 const ThunkInfo &Thunk) {
72 // Emit the return adjustment.
73 bool NullCheckValue = !ResultType->isReferenceType();
75 llvm::BasicBlock *AdjustNull = nullptr;
76 llvm::BasicBlock *AdjustNotNull = nullptr;
77 llvm::BasicBlock *AdjustEnd = nullptr;
79 llvm::Value *ReturnValue = RV.getScalarVal();
82 AdjustNull = CGF.createBasicBlock("adjust.null");
83 AdjustNotNull = CGF.createBasicBlock("adjust.notnull");
84 AdjustEnd = CGF.createBasicBlock("adjust.end");
86 llvm::Value *IsNull = CGF.Builder.CreateIsNull(ReturnValue);
87 CGF.Builder.CreateCondBr(IsNull, AdjustNull, AdjustNotNull);
88 CGF.EmitBlock(AdjustNotNull);
91 auto ClassDecl = ResultType->getPointeeType()->getAsCXXRecordDecl();
92 auto ClassAlign = CGF.CGM.getClassPointerAlignment(ClassDecl);
93 ReturnValue = CGF.CGM.getCXXABI().performReturnAdjustment(CGF,
94 Address(ReturnValue, ClassAlign),
98 CGF.Builder.CreateBr(AdjustEnd);
99 CGF.EmitBlock(AdjustNull);
100 CGF.Builder.CreateBr(AdjustEnd);
101 CGF.EmitBlock(AdjustEnd);
103 llvm::PHINode *PHI = CGF.Builder.CreatePHI(ReturnValue->getType(), 2);
104 PHI->addIncoming(ReturnValue, AdjustNotNull);
105 PHI->addIncoming(llvm::Constant::getNullValue(ReturnValue->getType()),
110 return RValue::get(ReturnValue);
113 /// This function clones a function's DISubprogram node and enters it into
114 /// a value map with the intent that the map can be utilized by the cloner
115 /// to short-circuit Metadata node mapping.
116 /// Furthermore, the function resolves any DILocalVariable nodes referenced
117 /// by dbg.value intrinsics so they can be properly mapped during cloning.
118 static void resolveTopLevelMetadata(llvm::Function *Fn,
119 llvm::ValueToValueMapTy &VMap) {
120 // Clone the DISubprogram node and put it into the Value map.
121 auto *DIS = Fn->getSubprogram();
124 auto *NewDIS = DIS->replaceWithDistinct(DIS->clone());
125 VMap.MD()[DIS].reset(NewDIS);
127 // Find all llvm.dbg.declare intrinsics and resolve the DILocalVariable nodes
128 // they are referencing.
129 for (auto &BB : Fn->getBasicBlockList()) {
131 if (auto *DII = dyn_cast<llvm::DbgInfoIntrinsic>(&I)) {
132 auto *DILocal = DII->getVariable();
133 if (!DILocal->isResolved())
140 // This function does roughly the same thing as GenerateThunk, but in a
141 // very different way, so that va_start and va_end work correctly.
142 // FIXME: This function assumes "this" is the first non-sret LLVM argument of
143 // a function, and that there is an alloca built in the entry block
144 // for all accesses to "this".
145 // FIXME: This function assumes there is only one "ret" statement per function.
146 // FIXME: Cloning isn't correct in the presence of indirect goto!
147 // FIXME: This implementation of thunks bloats codesize by duplicating the
148 // function definition. There are alternatives:
149 // 1. Add some sort of stub support to LLVM for cases where we can
150 // do a this adjustment, then a sibcall.
151 // 2. We could transform the definition to take a va_list instead of an
152 // actual variable argument list, then have the thunks (including a
153 // no-op thunk for the regular definition) call va_start/va_end.
154 // There's a bit of per-call overhead for this solution, but it's
155 // better for codesize if the definition is long.
157 CodeGenFunction::GenerateVarArgsThunk(llvm::Function *Fn,
158 const CGFunctionInfo &FnInfo,
159 GlobalDecl GD, const ThunkInfo &Thunk) {
160 const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
161 const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
162 QualType ResultType = FPT->getReturnType();
164 // Get the original function
165 assert(FnInfo.isVariadic());
166 llvm::Type *Ty = CGM.getTypes().GetFunctionType(FnInfo);
167 llvm::Value *Callee = CGM.GetAddrOfFunction(GD, Ty, /*ForVTable=*/true);
168 llvm::Function *BaseFn = cast<llvm::Function>(Callee);
171 llvm::ValueToValueMapTy VMap;
173 // We are cloning a function while some Metadata nodes are still unresolved.
174 // Ensure that the value mapper does not encounter any of them.
175 resolveTopLevelMetadata(BaseFn, VMap);
176 llvm::Function *NewFn = llvm::CloneFunction(BaseFn, VMap);
177 Fn->replaceAllUsesWith(NewFn);
179 Fn->eraseFromParent();
182 // "Initialize" CGF (minimally).
185 // Get the "this" value
186 llvm::Function::arg_iterator AI = Fn->arg_begin();
187 if (CGM.ReturnTypeUsesSRet(FnInfo))
190 // Find the first store of "this", which will be to the alloca associated
192 Address ThisPtr(&*AI, CGM.getClassPointerAlignment(MD->getParent()));
193 llvm::BasicBlock *EntryBB = &Fn->front();
194 llvm::BasicBlock::iterator ThisStore =
195 std::find_if(EntryBB->begin(), EntryBB->end(), [&](llvm::Instruction &I) {
196 return isa<llvm::StoreInst>(I) &&
197 I.getOperand(0) == ThisPtr.getPointer();
199 assert(ThisStore != EntryBB->end() &&
200 "Store of this should be in entry block?");
201 // Adjust "this", if necessary.
202 Builder.SetInsertPoint(&*ThisStore);
203 llvm::Value *AdjustedThisPtr =
204 CGM.getCXXABI().performThisAdjustment(*this, ThisPtr, Thunk.This);
205 ThisStore->setOperand(0, AdjustedThisPtr);
207 if (!Thunk.Return.isEmpty()) {
208 // Fix up the returned value, if necessary.
209 for (llvm::BasicBlock &BB : *Fn) {
210 llvm::Instruction *T = BB.getTerminator();
211 if (isa<llvm::ReturnInst>(T)) {
212 RValue RV = RValue::get(T->getOperand(0));
213 T->eraseFromParent();
214 Builder.SetInsertPoint(&BB);
215 RV = PerformReturnAdjustment(*this, ResultType, RV, Thunk);
216 Builder.CreateRet(RV.getScalarVal());
225 void CodeGenFunction::StartThunk(llvm::Function *Fn, GlobalDecl GD,
226 const CGFunctionInfo &FnInfo,
227 bool IsUnprototyped) {
228 assert(!CurGD.getDecl() && "CurGD was already set!");
230 CurFuncIsThunk = true;
232 // Build FunctionArgs.
233 const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
234 QualType ThisType = MD->getThisType(getContext());
235 const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
238 ResultType = CGM.getContext().VoidTy;
239 else if (CGM.getCXXABI().HasThisReturn(GD))
240 ResultType = ThisType;
241 else if (CGM.getCXXABI().hasMostDerivedReturn(GD))
242 ResultType = CGM.getContext().VoidPtrTy;
244 ResultType = FPT->getReturnType();
245 FunctionArgList FunctionArgs;
247 // Create the implicit 'this' parameter declaration.
248 CGM.getCXXABI().buildThisParam(*this, FunctionArgs);
250 // Add the rest of the parameters, if we have a prototype to work with.
251 if (!IsUnprototyped) {
252 FunctionArgs.append(MD->param_begin(), MD->param_end());
254 if (isa<CXXDestructorDecl>(MD))
255 CGM.getCXXABI().addImplicitStructorParams(*this, ResultType,
259 // Start defining the function.
260 auto NL = ApplyDebugLocation::CreateEmpty(*this);
261 StartFunction(GlobalDecl(), ResultType, Fn, FnInfo, FunctionArgs,
263 // Create a scope with an artificial location for the body of this function.
264 auto AL = ApplyDebugLocation::CreateArtificial(*this);
266 // Since we didn't pass a GlobalDecl to StartFunction, do this ourselves.
267 CGM.getCXXABI().EmitInstanceFunctionProlog(*this);
268 CXXThisValue = CXXABIThisValue;
273 void CodeGenFunction::FinishThunk() {
274 // Clear these to restore the invariants expected by
275 // StartFunction/FinishFunction.
276 CurCodeDecl = nullptr;
277 CurFuncDecl = nullptr;
282 void CodeGenFunction::EmitCallAndReturnForThunk(llvm::Constant *CalleePtr,
283 const ThunkInfo *Thunk,
284 bool IsUnprototyped) {
285 assert(isa<CXXMethodDecl>(CurGD.getDecl()) &&
286 "Please use a new CGF for this thunk");
287 const CXXMethodDecl *MD = cast<CXXMethodDecl>(CurGD.getDecl());
289 // Adjust the 'this' pointer if necessary
290 llvm::Value *AdjustedThisPtr =
291 Thunk ? CGM.getCXXABI().performThisAdjustment(
292 *this, LoadCXXThisAddress(), Thunk->This)
295 if (CurFnInfo->usesInAlloca() || IsUnprototyped) {
296 // We don't handle return adjusting thunks, because they require us to call
297 // the copy constructor. For now, fall through and pretend the return
298 // adjustment was empty so we don't crash.
299 if (Thunk && !Thunk->Return.isEmpty()) {
301 CGM.ErrorUnsupported(
302 MD, "return-adjusting thunk with incomplete parameter type");
304 CGM.ErrorUnsupported(
305 MD, "non-trivial argument copy for return-adjusting thunk");
307 EmitMustTailThunk(MD, AdjustedThisPtr, CalleePtr);
311 // Start building CallArgs.
312 CallArgList CallArgs;
313 QualType ThisType = MD->getThisType(getContext());
314 CallArgs.add(RValue::get(AdjustedThisPtr), ThisType);
316 if (isa<CXXDestructorDecl>(MD))
317 CGM.getCXXABI().adjustCallArgsForDestructorThunk(*this, CurGD, CallArgs);
320 unsigned PrefixArgs = CallArgs.size() - 1;
322 // Add the rest of the arguments.
323 for (const ParmVarDecl *PD : MD->parameters())
324 EmitDelegateCallArg(CallArgs, PD, SourceLocation());
326 const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
329 const CGFunctionInfo &CallFnInfo = CGM.getTypes().arrangeCXXMethodCall(
330 CallArgs, FPT, RequiredArgs::forPrototypePlus(FPT, 1, MD), PrefixArgs);
331 assert(CallFnInfo.getRegParm() == CurFnInfo->getRegParm() &&
332 CallFnInfo.isNoReturn() == CurFnInfo->isNoReturn() &&
333 CallFnInfo.getCallingConvention() == CurFnInfo->getCallingConvention());
334 assert(isa<CXXDestructorDecl>(MD) || // ignore dtor return types
335 similar(CallFnInfo.getReturnInfo(), CallFnInfo.getReturnType(),
336 CurFnInfo->getReturnInfo(), CurFnInfo->getReturnType()));
337 assert(CallFnInfo.arg_size() == CurFnInfo->arg_size());
338 for (unsigned i = 0, e = CurFnInfo->arg_size(); i != e; ++i)
339 assert(similar(CallFnInfo.arg_begin()[i].info,
340 CallFnInfo.arg_begin()[i].type,
341 CurFnInfo->arg_begin()[i].info,
342 CurFnInfo->arg_begin()[i].type));
345 // Determine whether we have a return value slot to use.
346 QualType ResultType = CGM.getCXXABI().HasThisReturn(CurGD)
348 : CGM.getCXXABI().hasMostDerivedReturn(CurGD)
349 ? CGM.getContext().VoidPtrTy
350 : FPT->getReturnType();
351 ReturnValueSlot Slot;
352 if (!ResultType->isVoidType() &&
353 CurFnInfo->getReturnInfo().getKind() == ABIArgInfo::Indirect &&
354 !hasScalarEvaluationKind(CurFnInfo->getReturnType()))
355 Slot = ReturnValueSlot(ReturnValue, ResultType.isVolatileQualified());
357 // Now emit our call.
358 llvm::Instruction *CallOrInvoke;
359 CGCallee Callee = CGCallee::forDirect(CalleePtr, MD);
360 RValue RV = EmitCall(*CurFnInfo, Callee, Slot, CallArgs, &CallOrInvoke);
362 // Consider return adjustment if we have ThunkInfo.
363 if (Thunk && !Thunk->Return.isEmpty())
364 RV = PerformReturnAdjustment(*this, ResultType, RV, *Thunk);
365 else if (llvm::CallInst* Call = dyn_cast<llvm::CallInst>(CallOrInvoke))
366 Call->setTailCallKind(llvm::CallInst::TCK_Tail);
369 if (!ResultType->isVoidType() && Slot.isNull())
370 CGM.getCXXABI().EmitReturnFromThunk(*this, RV, ResultType);
372 // Disable the final ARC autorelease.
373 AutoreleaseResult = false;
378 void CodeGenFunction::EmitMustTailThunk(const CXXMethodDecl *MD,
379 llvm::Value *AdjustedThisPtr,
380 llvm::Value *CalleePtr) {
381 // Emitting a musttail call thunk doesn't use any of the CGCall.cpp machinery
382 // to translate AST arguments into LLVM IR arguments. For thunks, we know
383 // that the caller prototype more or less matches the callee prototype with
384 // the exception of 'this'.
385 SmallVector<llvm::Value *, 8> Args;
386 for (llvm::Argument &A : CurFn->args())
389 // Set the adjusted 'this' pointer.
390 const ABIArgInfo &ThisAI = CurFnInfo->arg_begin()->info;
391 if (ThisAI.isDirect()) {
392 const ABIArgInfo &RetAI = CurFnInfo->getReturnInfo();
393 int ThisArgNo = RetAI.isIndirect() && !RetAI.isSRetAfterThis() ? 1 : 0;
394 llvm::Type *ThisType = Args[ThisArgNo]->getType();
395 if (ThisType != AdjustedThisPtr->getType())
396 AdjustedThisPtr = Builder.CreateBitCast(AdjustedThisPtr, ThisType);
397 Args[ThisArgNo] = AdjustedThisPtr;
399 assert(ThisAI.isInAlloca() && "this is passed directly or inalloca");
400 Address ThisAddr = GetAddrOfLocalVar(CXXABIThisDecl);
401 llvm::Type *ThisType = ThisAddr.getElementType();
402 if (ThisType != AdjustedThisPtr->getType())
403 AdjustedThisPtr = Builder.CreateBitCast(AdjustedThisPtr, ThisType);
404 Builder.CreateStore(AdjustedThisPtr, ThisAddr);
407 // Emit the musttail call manually. Even if the prologue pushed cleanups, we
408 // don't actually want to run them.
409 llvm::CallInst *Call = Builder.CreateCall(CalleePtr, Args);
410 Call->setTailCallKind(llvm::CallInst::TCK_MustTail);
412 // Apply the standard set of call attributes.
413 unsigned CallingConv;
414 llvm::AttributeList Attrs;
415 CGM.ConstructAttributeList(CalleePtr->getName(), *CurFnInfo, MD, Attrs,
416 CallingConv, /*AttrOnCallSite=*/true);
417 Call->setAttributes(Attrs);
418 Call->setCallingConv(static_cast<llvm::CallingConv::ID>(CallingConv));
420 if (Call->getType()->isVoidTy())
421 Builder.CreateRetVoid();
423 Builder.CreateRet(Call);
425 // Finish the function to maintain CodeGenFunction invariants.
426 // FIXME: Don't emit unreachable code.
427 EmitBlock(createBasicBlock());
431 void CodeGenFunction::generateThunk(llvm::Function *Fn,
432 const CGFunctionInfo &FnInfo, GlobalDecl GD,
433 const ThunkInfo &Thunk,
434 bool IsUnprototyped) {
435 StartThunk(Fn, GD, FnInfo, IsUnprototyped);
436 // Create a scope with an artificial location for the body of this function.
437 auto AL = ApplyDebugLocation::CreateArtificial(*this);
439 // Get our callee. Use a placeholder type if this method is unprototyped so
440 // that CodeGenModule doesn't try to set attributes.
443 Ty = llvm::StructType::get(getLLVMContext());
445 Ty = CGM.getTypes().GetFunctionType(FnInfo);
447 llvm::Constant *Callee = CGM.GetAddrOfFunction(GD, Ty, /*ForVTable=*/true);
449 // Fix up the function type for an unprototyped musttail call.
451 Callee = llvm::ConstantExpr::getBitCast(Callee, Fn->getType());
453 // Make the call and return the result.
454 EmitCallAndReturnForThunk(Callee, &Thunk, IsUnprototyped);
457 static bool shouldEmitVTableThunk(CodeGenModule &CGM, const CXXMethodDecl *MD,
458 bool IsUnprototyped, bool ForVTable) {
459 // Always emit thunks in the MS C++ ABI. We cannot rely on other TUs to
460 // provide thunks for us.
461 if (CGM.getTarget().getCXXABI().isMicrosoft())
464 // In the Itanium C++ ABI, vtable thunks are provided by TUs that provide
465 // definitions of the main method. Therefore, emitting thunks with the vtable
466 // is purely an optimization. Emit the thunk if optimizations are enabled and
467 // all of the parameter types are complete.
469 return CGM.getCodeGenOpts().OptimizationLevel && !IsUnprototyped;
471 // Always emit thunks along with the method definition.
475 llvm::Constant *CodeGenVTables::maybeEmitThunk(GlobalDecl GD,
478 const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
480 // First, get a declaration. Compute the mangled name. Don't worry about
481 // getting the function prototype right, since we may only need this
482 // declaration to fill in a vtable slot.
483 SmallString<256> Name;
484 MangleContext &MCtx = CGM.getCXXABI().getMangleContext();
485 llvm::raw_svector_ostream Out(Name);
486 if (const CXXDestructorDecl *DD = dyn_cast<CXXDestructorDecl>(MD))
487 MCtx.mangleCXXDtorThunk(DD, GD.getDtorType(), TI.This, Out);
489 MCtx.mangleThunk(MD, TI, Out);
490 llvm::Type *ThunkVTableTy = CGM.getTypes().GetFunctionTypeForVTable(GD);
491 llvm::Constant *Thunk = CGM.GetAddrOfThunk(Name, ThunkVTableTy, GD);
493 // If we don't need to emit a definition, return this declaration as is.
494 bool IsUnprototyped = !CGM.getTypes().isFuncTypeConvertible(
495 MD->getType()->castAs<FunctionType>());
496 if (!shouldEmitVTableThunk(CGM, MD, IsUnprototyped, ForVTable))
499 // Arrange a function prototype appropriate for a function definition. In some
500 // cases in the MS ABI, we may need to build an unprototyped musttail thunk.
501 const CGFunctionInfo &FnInfo =
502 IsUnprototyped ? CGM.getTypes().arrangeUnprototypedMustTailThunk(MD)
503 : CGM.getTypes().arrangeGlobalDeclaration(GD);
504 llvm::FunctionType *ThunkFnTy = CGM.getTypes().GetFunctionType(FnInfo);
506 // If the type of the underlying GlobalValue is wrong, we'll have to replace
507 // it. It should be a declaration.
508 llvm::Function *ThunkFn = cast<llvm::Function>(Thunk->stripPointerCasts());
509 if (ThunkFn->getFunctionType() != ThunkFnTy) {
510 llvm::GlobalValue *OldThunkFn = ThunkFn;
512 assert(OldThunkFn->isDeclaration() && "Shouldn't replace non-declaration");
514 // Remove the name from the old thunk function and get a new thunk.
515 OldThunkFn->setName(StringRef());
516 ThunkFn = llvm::Function::Create(ThunkFnTy, llvm::Function::ExternalLinkage,
517 Name.str(), &CGM.getModule());
518 CGM.SetLLVMFunctionAttributes(MD, FnInfo, ThunkFn);
520 // If needed, replace the old thunk with a bitcast.
521 if (!OldThunkFn->use_empty()) {
522 llvm::Constant *NewPtrForOldDecl =
523 llvm::ConstantExpr::getBitCast(ThunkFn, OldThunkFn->getType());
524 OldThunkFn->replaceAllUsesWith(NewPtrForOldDecl);
527 // Remove the old thunk.
528 OldThunkFn->eraseFromParent();
531 bool ABIHasKeyFunctions = CGM.getTarget().getCXXABI().hasKeyFunctions();
532 bool UseAvailableExternallyLinkage = ForVTable && ABIHasKeyFunctions;
534 if (!ThunkFn->isDeclaration()) {
535 if (!ABIHasKeyFunctions || UseAvailableExternallyLinkage) {
536 // There is already a thunk emitted for this function, do nothing.
540 setThunkProperties(CGM, TI, ThunkFn, ForVTable, GD);
544 // If this will be unprototyped, add the "thunk" attribute so that LLVM knows
545 // that the return type is meaningless. These thunks can be used to call
546 // functions with differing return types, and the caller is required to cast
547 // the prototype appropriately to extract the correct value.
549 ThunkFn->addFnAttr("thunk");
551 CGM.SetLLVMFunctionAttributesForDefinition(GD.getDecl(), ThunkFn);
553 if (!IsUnprototyped && ThunkFn->isVarArg()) {
554 // Varargs thunks are special; we can't just generate a call because
555 // we can't copy the varargs. Our implementation is rather
556 // expensive/sucky at the moment, so don't generate the thunk unless
558 // FIXME: Do something better here; GenerateVarArgsThunk is extremely ugly.
559 if (UseAvailableExternallyLinkage)
561 ThunkFn = CodeGenFunction(CGM).GenerateVarArgsThunk(ThunkFn, FnInfo, GD,
564 // Normal thunk body generation.
565 CodeGenFunction(CGM).generateThunk(ThunkFn, FnInfo, GD, TI, IsUnprototyped);
568 setThunkProperties(CGM, TI, ThunkFn, ForVTable, GD);
572 void CodeGenVTables::EmitThunks(GlobalDecl GD) {
573 const CXXMethodDecl *MD =
574 cast<CXXMethodDecl>(GD.getDecl())->getCanonicalDecl();
576 // We don't need to generate thunks for the base destructor.
577 if (isa<CXXDestructorDecl>(MD) && GD.getDtorType() == Dtor_Base)
580 const VTableContextBase::ThunkInfoVectorTy *ThunkInfoVector =
581 VTContext->getThunkInfo(GD);
583 if (!ThunkInfoVector)
586 for (const ThunkInfo& Thunk : *ThunkInfoVector)
587 maybeEmitThunk(GD, Thunk, /*ForVTable=*/false);
590 void CodeGenVTables::addVTableComponent(
591 ConstantArrayBuilder &builder, const VTableLayout &layout,
592 unsigned idx, llvm::Constant *rtti, unsigned &nextVTableThunkIndex) {
593 auto &component = layout.vtable_components()[idx];
595 auto addOffsetConstant = [&](CharUnits offset) {
596 builder.add(llvm::ConstantExpr::getIntToPtr(
597 llvm::ConstantInt::get(CGM.PtrDiffTy, offset.getQuantity()),
601 switch (component.getKind()) {
602 case VTableComponent::CK_VCallOffset:
603 return addOffsetConstant(component.getVCallOffset());
605 case VTableComponent::CK_VBaseOffset:
606 return addOffsetConstant(component.getVBaseOffset());
608 case VTableComponent::CK_OffsetToTop:
609 return addOffsetConstant(component.getOffsetToTop());
611 case VTableComponent::CK_RTTI:
612 return builder.add(llvm::ConstantExpr::getBitCast(rtti, CGM.Int8PtrTy));
614 case VTableComponent::CK_FunctionPointer:
615 case VTableComponent::CK_CompleteDtorPointer:
616 case VTableComponent::CK_DeletingDtorPointer: {
619 // Get the right global decl.
620 switch (component.getKind()) {
622 llvm_unreachable("Unexpected vtable component kind");
623 case VTableComponent::CK_FunctionPointer:
624 GD = component.getFunctionDecl();
626 case VTableComponent::CK_CompleteDtorPointer:
627 GD = GlobalDecl(component.getDestructorDecl(), Dtor_Complete);
629 case VTableComponent::CK_DeletingDtorPointer:
630 GD = GlobalDecl(component.getDestructorDecl(), Dtor_Deleting);
634 if (CGM.getLangOpts().CUDA) {
635 // Emit NULL for methods we can't codegen on this
636 // side. Otherwise we'd end up with vtable with unresolved
638 const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
639 // OK on device side: functions w/ __device__ attribute
640 // OK on host side: anything except __device__-only functions.
642 CGM.getLangOpts().CUDAIsDevice
643 ? MD->hasAttr<CUDADeviceAttr>()
644 : (MD->hasAttr<CUDAHostAttr>() || !MD->hasAttr<CUDADeviceAttr>());
646 return builder.addNullPointer(CGM.Int8PtrTy);
647 // Method is acceptable, continue processing as usual.
650 auto getSpecialVirtualFn = [&](StringRef name) {
651 llvm::FunctionType *fnTy =
652 llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false);
653 llvm::Constant *fn = CGM.CreateRuntimeFunction(fnTy, name);
654 if (auto f = dyn_cast<llvm::Function>(fn))
655 f->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
656 return llvm::ConstantExpr::getBitCast(fn, CGM.Int8PtrTy);
659 llvm::Constant *fnPtr;
661 // Pure virtual member functions.
662 if (cast<CXXMethodDecl>(GD.getDecl())->isPure()) {
665 getSpecialVirtualFn(CGM.getCXXABI().GetPureVirtualCallName());
666 fnPtr = PureVirtualFn;
668 // Deleted virtual member functions.
669 } else if (cast<CXXMethodDecl>(GD.getDecl())->isDeleted()) {
670 if (!DeletedVirtualFn)
672 getSpecialVirtualFn(CGM.getCXXABI().GetDeletedVirtualCallName());
673 fnPtr = DeletedVirtualFn;
676 } else if (nextVTableThunkIndex < layout.vtable_thunks().size() &&
677 layout.vtable_thunks()[nextVTableThunkIndex].first == idx) {
678 auto &thunkInfo = layout.vtable_thunks()[nextVTableThunkIndex].second;
680 nextVTableThunkIndex++;
681 fnPtr = maybeEmitThunk(GD, thunkInfo, /*ForVTable=*/true);
683 // Otherwise we can use the method definition directly.
685 llvm::Type *fnTy = CGM.getTypes().GetFunctionTypeForVTable(GD);
686 fnPtr = CGM.GetAddrOfFunction(GD, fnTy, /*ForVTable=*/true);
689 fnPtr = llvm::ConstantExpr::getBitCast(fnPtr, CGM.Int8PtrTy);
694 case VTableComponent::CK_UnusedFunctionPointer:
695 return builder.addNullPointer(CGM.Int8PtrTy);
698 llvm_unreachable("Unexpected vtable component kind");
701 llvm::Type *CodeGenVTables::getVTableType(const VTableLayout &layout) {
702 SmallVector<llvm::Type *, 4> tys;
703 for (unsigned i = 0, e = layout.getNumVTables(); i != e; ++i) {
704 tys.push_back(llvm::ArrayType::get(CGM.Int8PtrTy, layout.getVTableSize(i)));
707 return llvm::StructType::get(CGM.getLLVMContext(), tys);
710 void CodeGenVTables::createVTableInitializer(ConstantStructBuilder &builder,
711 const VTableLayout &layout,
712 llvm::Constant *rtti) {
713 unsigned nextVTableThunkIndex = 0;
714 for (unsigned i = 0, e = layout.getNumVTables(); i != e; ++i) {
715 auto vtableElem = builder.beginArray(CGM.Int8PtrTy);
716 size_t thisIndex = layout.getVTableOffset(i);
717 size_t nextIndex = thisIndex + layout.getVTableSize(i);
718 for (unsigned i = thisIndex; i != nextIndex; ++i) {
719 addVTableComponent(vtableElem, layout, i, rtti, nextVTableThunkIndex);
721 vtableElem.finishAndAddTo(builder);
725 llvm::GlobalVariable *
726 CodeGenVTables::GenerateConstructionVTable(const CXXRecordDecl *RD,
727 const BaseSubobject &Base,
729 llvm::GlobalVariable::LinkageTypes Linkage,
730 VTableAddressPointsMapTy& AddressPoints) {
731 if (CGDebugInfo *DI = CGM.getModuleDebugInfo())
732 DI->completeClassData(Base.getBase());
734 std::unique_ptr<VTableLayout> VTLayout(
735 getItaniumVTableContext().createConstructionVTableLayout(
736 Base.getBase(), Base.getBaseOffset(), BaseIsVirtual, RD));
738 // Add the address points.
739 AddressPoints = VTLayout->getAddressPoints();
741 // Get the mangled construction vtable name.
742 SmallString<256> OutName;
743 llvm::raw_svector_ostream Out(OutName);
744 cast<ItaniumMangleContext>(CGM.getCXXABI().getMangleContext())
745 .mangleCXXCtorVTable(RD, Base.getBaseOffset().getQuantity(),
746 Base.getBase(), Out);
747 StringRef Name = OutName.str();
749 llvm::Type *VTType = getVTableType(*VTLayout);
751 // Construction vtable symbols are not part of the Itanium ABI, so we cannot
752 // guarantee that they actually will be available externally. Instead, when
753 // emitting an available_externally VTT, we provide references to an internal
754 // linkage construction vtable. The ABI only requires complete-object vtables
755 // to be the same for all instances of a type, not construction vtables.
756 if (Linkage == llvm::GlobalVariable::AvailableExternallyLinkage)
757 Linkage = llvm::GlobalVariable::InternalLinkage;
759 // Create the variable that will hold the construction vtable.
760 llvm::GlobalVariable *VTable =
761 CGM.CreateOrReplaceCXXRuntimeVariable(Name, VTType, Linkage);
762 CGM.setGVProperties(VTable, RD);
764 // V-tables are always unnamed_addr.
765 VTable->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
767 llvm::Constant *RTTI = CGM.GetAddrOfRTTIDescriptor(
768 CGM.getContext().getTagDeclType(Base.getBase()));
770 // Create and set the initializer.
771 ConstantInitBuilder builder(CGM);
772 auto components = builder.beginStruct();
773 createVTableInitializer(components, *VTLayout, RTTI);
774 components.finishAndSetAsInitializer(VTable);
776 CGM.EmitVTableTypeMetadata(VTable, *VTLayout.get());
781 static bool shouldEmitAvailableExternallyVTable(const CodeGenModule &CGM,
782 const CXXRecordDecl *RD) {
783 return CGM.getCodeGenOpts().OptimizationLevel > 0 &&
784 CGM.getCXXABI().canSpeculativelyEmitVTable(RD);
787 /// Compute the required linkage of the vtable for the given class.
789 /// Note that we only call this at the end of the translation unit.
790 llvm::GlobalVariable::LinkageTypes
791 CodeGenModule::getVTableLinkage(const CXXRecordDecl *RD) {
792 if (!RD->isExternallyVisible())
793 return llvm::GlobalVariable::InternalLinkage;
795 // We're at the end of the translation unit, so the current key
796 // function is fully correct.
797 const CXXMethodDecl *keyFunction = Context.getCurrentKeyFunction(RD);
798 if (keyFunction && !RD->hasAttr<DLLImportAttr>()) {
799 // If this class has a key function, use that to determine the
800 // linkage of the vtable.
801 const FunctionDecl *def = nullptr;
802 if (keyFunction->hasBody(def))
803 keyFunction = cast<CXXMethodDecl>(def);
805 switch (keyFunction->getTemplateSpecializationKind()) {
807 case TSK_ExplicitSpecialization:
808 assert((def || CodeGenOpts.OptimizationLevel > 0 ||
809 CodeGenOpts.getDebugInfo() != codegenoptions::NoDebugInfo) &&
810 "Shouldn't query vtable linkage without key function, "
811 "optimizations, or debug info");
812 if (!def && CodeGenOpts.OptimizationLevel > 0)
813 return llvm::GlobalVariable::AvailableExternallyLinkage;
815 if (keyFunction->isInlined())
816 return !Context.getLangOpts().AppleKext ?
817 llvm::GlobalVariable::LinkOnceODRLinkage :
818 llvm::Function::InternalLinkage;
820 return llvm::GlobalVariable::ExternalLinkage;
822 case TSK_ImplicitInstantiation:
823 return !Context.getLangOpts().AppleKext ?
824 llvm::GlobalVariable::LinkOnceODRLinkage :
825 llvm::Function::InternalLinkage;
827 case TSK_ExplicitInstantiationDefinition:
828 return !Context.getLangOpts().AppleKext ?
829 llvm::GlobalVariable::WeakODRLinkage :
830 llvm::Function::InternalLinkage;
832 case TSK_ExplicitInstantiationDeclaration:
833 llvm_unreachable("Should not have been asked to emit this");
837 // -fapple-kext mode does not support weak linkage, so we must use
839 if (Context.getLangOpts().AppleKext)
840 return llvm::Function::InternalLinkage;
842 llvm::GlobalVariable::LinkageTypes DiscardableODRLinkage =
843 llvm::GlobalValue::LinkOnceODRLinkage;
844 llvm::GlobalVariable::LinkageTypes NonDiscardableODRLinkage =
845 llvm::GlobalValue::WeakODRLinkage;
846 if (RD->hasAttr<DLLExportAttr>()) {
847 // Cannot discard exported vtables.
848 DiscardableODRLinkage = NonDiscardableODRLinkage;
849 } else if (RD->hasAttr<DLLImportAttr>()) {
850 // Imported vtables are available externally.
851 DiscardableODRLinkage = llvm::GlobalVariable::AvailableExternallyLinkage;
852 NonDiscardableODRLinkage = llvm::GlobalVariable::AvailableExternallyLinkage;
855 switch (RD->getTemplateSpecializationKind()) {
857 case TSK_ExplicitSpecialization:
858 case TSK_ImplicitInstantiation:
859 return DiscardableODRLinkage;
861 case TSK_ExplicitInstantiationDeclaration:
862 // Explicit instantiations in MSVC do not provide vtables, so we must emit
864 if (getTarget().getCXXABI().isMicrosoft())
865 return DiscardableODRLinkage;
866 return shouldEmitAvailableExternallyVTable(*this, RD)
867 ? llvm::GlobalVariable::AvailableExternallyLinkage
868 : llvm::GlobalVariable::ExternalLinkage;
870 case TSK_ExplicitInstantiationDefinition:
871 return NonDiscardableODRLinkage;
874 llvm_unreachable("Invalid TemplateSpecializationKind!");
877 /// This is a callback from Sema to tell us that a particular vtable is
878 /// required to be emitted in this translation unit.
880 /// This is only called for vtables that _must_ be emitted (mainly due to key
881 /// functions). For weak vtables, CodeGen tracks when they are needed and
882 /// emits them as-needed.
883 void CodeGenModule::EmitVTable(CXXRecordDecl *theClass) {
884 VTables.GenerateClassData(theClass);
888 CodeGenVTables::GenerateClassData(const CXXRecordDecl *RD) {
889 if (CGDebugInfo *DI = CGM.getModuleDebugInfo())
890 DI->completeClassData(RD);
892 if (RD->getNumVBases())
893 CGM.getCXXABI().emitVirtualInheritanceTables(RD);
895 CGM.getCXXABI().emitVTableDefinitions(*this, RD);
898 /// At this point in the translation unit, does it appear that can we
899 /// rely on the vtable being defined elsewhere in the program?
901 /// The response is really only definitive when called at the end of
902 /// the translation unit.
904 /// The only semantic restriction here is that the object file should
905 /// not contain a vtable definition when that vtable is defined
906 /// strongly elsewhere. Otherwise, we'd just like to avoid emitting
907 /// vtables when unnecessary.
908 bool CodeGenVTables::isVTableExternal(const CXXRecordDecl *RD) {
909 assert(RD->isDynamicClass() && "Non-dynamic classes have no VTable.");
911 // We always synthesize vtables if they are needed in the MS ABI. MSVC doesn't
912 // emit them even if there is an explicit template instantiation.
913 if (CGM.getTarget().getCXXABI().isMicrosoft())
916 // If we have an explicit instantiation declaration (and not a
917 // definition), the vtable is defined elsewhere.
918 TemplateSpecializationKind TSK = RD->getTemplateSpecializationKind();
919 if (TSK == TSK_ExplicitInstantiationDeclaration)
922 // Otherwise, if the class is an instantiated template, the
923 // vtable must be defined here.
924 if (TSK == TSK_ImplicitInstantiation ||
925 TSK == TSK_ExplicitInstantiationDefinition)
928 // Otherwise, if the class doesn't have a key function (possibly
929 // anymore), the vtable must be defined here.
930 const CXXMethodDecl *keyFunction = CGM.getContext().getCurrentKeyFunction(RD);
934 // Otherwise, if we don't have a definition of the key function, the
935 // vtable must be defined somewhere else.
936 return !keyFunction->hasBody();
939 /// Given that we're currently at the end of the translation unit, and
940 /// we've emitted a reference to the vtable for this class, should
941 /// we define that vtable?
942 static bool shouldEmitVTableAtEndOfTranslationUnit(CodeGenModule &CGM,
943 const CXXRecordDecl *RD) {
944 // If vtable is internal then it has to be done.
945 if (!CGM.getVTables().isVTableExternal(RD))
948 // If it's external then maybe we will need it as available_externally.
949 return shouldEmitAvailableExternallyVTable(CGM, RD);
952 /// Given that at some point we emitted a reference to one or more
953 /// vtables, and that we are now at the end of the translation unit,
954 /// decide whether we should emit them.
955 void CodeGenModule::EmitDeferredVTables() {
957 // Remember the size of DeferredVTables, because we're going to assume
958 // that this entire operation doesn't modify it.
959 size_t savedSize = DeferredVTables.size();
962 for (const CXXRecordDecl *RD : DeferredVTables)
963 if (shouldEmitVTableAtEndOfTranslationUnit(*this, RD))
964 VTables.GenerateClassData(RD);
965 else if (shouldOpportunisticallyEmitVTables())
966 OpportunisticVTables.push_back(RD);
968 assert(savedSize == DeferredVTables.size() &&
969 "deferred extra vtables during vtable emission?");
970 DeferredVTables.clear();
973 bool CodeGenModule::HasHiddenLTOVisibility(const CXXRecordDecl *RD) {
974 LinkageInfo LV = RD->getLinkageAndVisibility();
975 if (!isExternallyVisible(LV.getLinkage()))
978 if (RD->hasAttr<LTOVisibilityPublicAttr>() || RD->hasAttr<UuidAttr>())
981 if (getTriple().isOSBinFormatCOFF()) {
982 if (RD->hasAttr<DLLExportAttr>() || RD->hasAttr<DLLImportAttr>())
985 if (LV.getVisibility() != HiddenVisibility)
989 if (getCodeGenOpts().LTOVisibilityPublicStd) {
990 const DeclContext *DC = RD;
992 auto *D = cast<Decl>(DC);
993 DC = DC->getParent();
994 if (isa<TranslationUnitDecl>(DC->getRedeclContext())) {
995 if (auto *ND = dyn_cast<NamespaceDecl>(D))
996 if (const IdentifierInfo *II = ND->getIdentifier())
997 if (II->isStr("std") || II->isStr("stdext"))
1007 void CodeGenModule::EmitVTableTypeMetadata(llvm::GlobalVariable *VTable,
1008 const VTableLayout &VTLayout) {
1009 if (!getCodeGenOpts().LTOUnit)
1012 CharUnits PointerWidth =
1013 Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
1015 typedef std::pair<const CXXRecordDecl *, unsigned> AddressPoint;
1016 std::vector<AddressPoint> AddressPoints;
1017 for (auto &&AP : VTLayout.getAddressPoints())
1018 AddressPoints.push_back(std::make_pair(
1019 AP.first.getBase(), VTLayout.getVTableOffset(AP.second.VTableIndex) +
1020 AP.second.AddressPointIndex));
1022 // Sort the address points for determinism.
1023 llvm::sort(AddressPoints.begin(), AddressPoints.end(),
1024 [this](const AddressPoint &AP1, const AddressPoint &AP2) {
1029 llvm::raw_string_ostream O1(S1);
1030 getCXXABI().getMangleContext().mangleTypeName(
1031 QualType(AP1.first->getTypeForDecl(), 0), O1);
1035 llvm::raw_string_ostream O2(S2);
1036 getCXXABI().getMangleContext().mangleTypeName(
1037 QualType(AP2.first->getTypeForDecl(), 0), O2);
1045 return AP1.second < AP2.second;
1048 ArrayRef<VTableComponent> Comps = VTLayout.vtable_components();
1049 for (auto AP : AddressPoints) {
1050 // Create type metadata for the address point.
1051 AddVTableTypeMetadata(VTable, PointerWidth * AP.second, AP.first);
1053 // The class associated with each address point could also potentially be
1054 // used for indirect calls via a member function pointer, so we need to
1055 // annotate the address of each function pointer with the appropriate member
1056 // function pointer type.
1057 for (unsigned I = 0; I != Comps.size(); ++I) {
1058 if (Comps[I].getKind() != VTableComponent::CK_FunctionPointer)
1060 llvm::Metadata *MD = CreateMetadataIdentifierForVirtualMemPtrType(
1061 Context.getMemberPointerType(
1062 Comps[I].getFunctionDecl()->getType(),
1063 Context.getRecordType(AP.first).getTypePtr()));
1064 VTable->addTypeMetadata((PointerWidth * I).getQuantity(), MD);