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llvm-project/clang/lib/CodeGen/CGVTables.cpp
Hans Wennborg 853ae94660 Start adding support for dllimport/dllexport on classes (PR11170) 
This implements the central part of support for dllimport/dllexport on
classes: allowing the attribute on class declarations, inheriting it
to class members, and forcing emission of exported members. It's based
on Nico Rieck's patch from http://reviews.llvm.org/D1099.

This patch doesn't propagate dllexport to bases that are template
specializations, which is an interesting problem. It also doesn't
look at the rules when redeclaring classes with different attributes,
I'd like to do that separately.

Differential Revision: http://reviews.llvm.org/D3877

llvm-svn: 209908
2014-05-30 16:59:42 +00:00

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//===--- CGVTables.cpp - Emit LLVM Code for C++ vtables -------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This contains code dealing with C++ code generation of virtual tables.
//
//===----------------------------------------------------------------------===//
#include "CodeGenFunction.h"
#include "CGCXXABI.h"
#include "CodeGenModule.h"
#include "clang/AST/CXXInheritance.h"
#include "clang/AST/RecordLayout.h"
#include "clang/CodeGen/CGFunctionInfo.h"
#include "clang/Frontend/CodeGenOptions.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/SetVector.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Format.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include <algorithm>
#include <cstdio>
using namespace clang;
using namespace CodeGen;
CodeGenVTables::CodeGenVTables(CodeGenModule &CGM)
: CGM(CGM), VTContext(CGM.getContext().getVTableContext()) {}
llvm::Constant *CodeGenModule::GetAddrOfThunk(GlobalDecl GD,
const ThunkInfo &Thunk) {
const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
// Compute the mangled name.
SmallString<256> Name;
llvm::raw_svector_ostream Out(Name);
if (const CXXDestructorDecl* DD = dyn_cast<CXXDestructorDecl>(MD))
getCXXABI().getMangleContext().mangleCXXDtorThunk(DD, GD.getDtorType(),
Thunk.This, Out);
else
getCXXABI().getMangleContext().mangleThunk(MD, Thunk, Out);
Out.flush();
llvm::Type *Ty = getTypes().GetFunctionTypeForVTable(GD);
return GetOrCreateLLVMFunction(Name, Ty, GD, /*ForVTable=*/true,
/*DontDefer*/ true);
}
static void setThunkVisibility(CodeGenModule &CGM, const CXXMethodDecl *MD,
const ThunkInfo &Thunk, llvm::Function *Fn) {
CGM.setGlobalVisibility(Fn, MD);
}
#ifndef NDEBUG
static bool similar(const ABIArgInfo &infoL, CanQualType typeL,
const ABIArgInfo &infoR, CanQualType typeR) {
return (infoL.getKind() == infoR.getKind() &&
(typeL == typeR ||
(isa<PointerType>(typeL) && isa<PointerType>(typeR)) ||
(isa<ReferenceType>(typeL) && isa<ReferenceType>(typeR))));
}
#endif
static RValue PerformReturnAdjustment(CodeGenFunction &CGF,
QualType ResultType, RValue RV,
const ThunkInfo &Thunk) {
// Emit the return adjustment.
bool NullCheckValue = !ResultType->isReferenceType();
llvm::BasicBlock *AdjustNull = nullptr;
llvm::BasicBlock *AdjustNotNull = nullptr;
llvm::BasicBlock *AdjustEnd = nullptr;
llvm::Value *ReturnValue = RV.getScalarVal();
if (NullCheckValue) {
AdjustNull = CGF.createBasicBlock("adjust.null");
AdjustNotNull = CGF.createBasicBlock("adjust.notnull");
AdjustEnd = CGF.createBasicBlock("adjust.end");
llvm::Value *IsNull = CGF.Builder.CreateIsNull(ReturnValue);
CGF.Builder.CreateCondBr(IsNull, AdjustNull, AdjustNotNull);
CGF.EmitBlock(AdjustNotNull);
}
ReturnValue = CGF.CGM.getCXXABI().performReturnAdjustment(CGF, ReturnValue,
Thunk.Return);
if (NullCheckValue) {
CGF.Builder.CreateBr(AdjustEnd);
CGF.EmitBlock(AdjustNull);
CGF.Builder.CreateBr(AdjustEnd);
CGF.EmitBlock(AdjustEnd);
llvm::PHINode *PHI = CGF.Builder.CreatePHI(ReturnValue->getType(), 2);
PHI->addIncoming(ReturnValue, AdjustNotNull);
PHI->addIncoming(llvm::Constant::getNullValue(ReturnValue->getType()),
AdjustNull);
ReturnValue = PHI;
}
return RValue::get(ReturnValue);
}
// This function does roughly the same thing as GenerateThunk, but in a
// very different way, so that va_start and va_end work correctly.
// FIXME: This function assumes "this" is the first non-sret LLVM argument of
// a function, and that there is an alloca built in the entry block
// for all accesses to "this".
// FIXME: This function assumes there is only one "ret" statement per function.
// FIXME: Cloning isn't correct in the presence of indirect goto!
// FIXME: This implementation of thunks bloats codesize by duplicating the
// function definition. There are alternatives:
// 1. Add some sort of stub support to LLVM for cases where we can
// do a this adjustment, then a sibcall.
// 2. We could transform the definition to take a va_list instead of an
// actual variable argument list, then have the thunks (including a
// no-op thunk for the regular definition) call va_start/va_end.
// There's a bit of per-call overhead for this solution, but it's
// better for codesize if the definition is long.
void CodeGenFunction::GenerateVarArgsThunk(
llvm::Function *Fn,
const CGFunctionInfo &FnInfo,
GlobalDecl GD, const ThunkInfo &Thunk) {
const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
QualType ResultType = FPT->getReturnType();
// Get the original function
assert(FnInfo.isVariadic());
llvm::Type *Ty = CGM.getTypes().GetFunctionType(FnInfo);
llvm::Value *Callee = CGM.GetAddrOfFunction(GD, Ty, /*ForVTable=*/true);
llvm::Function *BaseFn = cast<llvm::Function>(Callee);
// Clone to thunk.
llvm::ValueToValueMapTy VMap;
llvm::Function *NewFn = llvm::CloneFunction(BaseFn, VMap,
/*ModuleLevelChanges=*/false);
CGM.getModule().getFunctionList().push_back(NewFn);
Fn->replaceAllUsesWith(NewFn);
NewFn->takeName(Fn);
Fn->eraseFromParent();
Fn = NewFn;
// "Initialize" CGF (minimally).
CurFn = Fn;
// Get the "this" value
llvm::Function::arg_iterator AI = Fn->arg_begin();
if (CGM.ReturnTypeUsesSRet(FnInfo))
++AI;
// Find the first store of "this", which will be to the alloca associated
// with "this".
llvm::Value *ThisPtr = &*AI;
llvm::BasicBlock *EntryBB = Fn->begin();
llvm::Instruction *ThisStore = nullptr;
for (llvm::BasicBlock::iterator I = EntryBB->begin(), E = EntryBB->end();
I != E; I++) {
if (isa<llvm::StoreInst>(I) && I->getOperand(0) == ThisPtr) {
ThisStore = cast<llvm::StoreInst>(I);
break;
}
}
assert(ThisStore && "Store of this should be in entry block?");
// Adjust "this", if necessary.
Builder.SetInsertPoint(ThisStore);
llvm::Value *AdjustedThisPtr =
CGM.getCXXABI().performThisAdjustment(*this, ThisPtr, Thunk.This);
ThisStore->setOperand(0, AdjustedThisPtr);
if (!Thunk.Return.isEmpty()) {
// Fix up the returned value, if necessary.
for (llvm::Function::iterator I = Fn->begin(), E = Fn->end(); I != E; I++) {
llvm::Instruction *T = I->getTerminator();
if (isa<llvm::ReturnInst>(T)) {
RValue RV = RValue::get(T->getOperand(0));
T->eraseFromParent();
Builder.SetInsertPoint(&*I);
RV = PerformReturnAdjustment(*this, ResultType, RV, Thunk);
Builder.CreateRet(RV.getScalarVal());
break;
}
}
}
}
void CodeGenFunction::StartThunk(llvm::Function *Fn, GlobalDecl GD,
const CGFunctionInfo &FnInfo) {
assert(!CurGD.getDecl() && "CurGD was already set!");
CurGD = GD;
// Build FunctionArgs.
const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
QualType ThisType = MD->getThisType(getContext());
const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
QualType ResultType =
CGM.getCXXABI().HasThisReturn(GD) ? ThisType : FPT->getReturnType();
FunctionArgList FunctionArgs;
// Create the implicit 'this' parameter declaration.
CGM.getCXXABI().buildThisParam(*this, FunctionArgs);
// Add the rest of the parameters.
for (FunctionDecl::param_const_iterator I = MD->param_begin(),
E = MD->param_end();
I != E; ++I)
FunctionArgs.push_back(*I);
if (isa<CXXDestructorDecl>(MD))
CGM.getCXXABI().addImplicitStructorParams(*this, ResultType, FunctionArgs);
// Start defining the function.
StartFunction(GlobalDecl(), ResultType, Fn, FnInfo, FunctionArgs,
MD->getLocation(), SourceLocation());
// Since we didn't pass a GlobalDecl to StartFunction, do this ourselves.
CGM.getCXXABI().EmitInstanceFunctionProlog(*this);
CXXThisValue = CXXABIThisValue;
}
void CodeGenFunction::EmitCallAndReturnForThunk(GlobalDecl GD,
llvm::Value *Callee,
const ThunkInfo *Thunk) {
assert(isa<CXXMethodDecl>(CurGD.getDecl()) &&
"Please use a new CGF for this thunk");
const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
// Adjust the 'this' pointer if necessary
llvm::Value *AdjustedThisPtr = Thunk ? CGM.getCXXABI().performThisAdjustment(
*this, LoadCXXThis(), Thunk->This)
: LoadCXXThis();
// Start building CallArgs.
CallArgList CallArgs;
QualType ThisType = MD->getThisType(getContext());
CallArgs.add(RValue::get(AdjustedThisPtr), ThisType);
if (isa<CXXDestructorDecl>(MD))
CGM.getCXXABI().adjustCallArgsForDestructorThunk(*this, GD, CallArgs);
// Add the rest of the arguments.
for (FunctionDecl::param_const_iterator I = MD->param_begin(),
E = MD->param_end(); I != E; ++I)
EmitDelegateCallArg(CallArgs, *I, (*I)->getLocStart());
const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
#ifndef NDEBUG
const CGFunctionInfo &CallFnInfo =
CGM.getTypes().arrangeCXXMethodCall(CallArgs, FPT,
RequiredArgs::forPrototypePlus(FPT, 1));
assert(CallFnInfo.getRegParm() == CurFnInfo->getRegParm() &&
CallFnInfo.isNoReturn() == CurFnInfo->isNoReturn() &&
CallFnInfo.getCallingConvention() == CurFnInfo->getCallingConvention());
assert(isa<CXXDestructorDecl>(MD) || // ignore dtor return types
similar(CallFnInfo.getReturnInfo(), CallFnInfo.getReturnType(),
CurFnInfo->getReturnInfo(), CurFnInfo->getReturnType()));
assert(CallFnInfo.arg_size() == CurFnInfo->arg_size());
for (unsigned i = 0, e = CurFnInfo->arg_size(); i != e; ++i)
assert(similar(CallFnInfo.arg_begin()[i].info,
CallFnInfo.arg_begin()[i].type,
CurFnInfo->arg_begin()[i].info,
CurFnInfo->arg_begin()[i].type));
#endif
// Determine whether we have a return value slot to use.
QualType ResultType =
CGM.getCXXABI().HasThisReturn(GD) ? ThisType : FPT->getReturnType();
ReturnValueSlot Slot;
if (!ResultType->isVoidType() &&
CurFnInfo->getReturnInfo().getKind() == ABIArgInfo::Indirect &&
!hasScalarEvaluationKind(CurFnInfo->getReturnType()))
Slot = ReturnValueSlot(ReturnValue, ResultType.isVolatileQualified());
// Now emit our call.
RValue RV = EmitCall(*CurFnInfo, Callee, Slot, CallArgs, MD);
// Consider return adjustment if we have ThunkInfo.
if (Thunk && !Thunk->Return.isEmpty())
RV = PerformReturnAdjustment(*this, ResultType, RV, *Thunk);
// Emit return.
if (!ResultType->isVoidType() && Slot.isNull())
CGM.getCXXABI().EmitReturnFromThunk(*this, RV, ResultType);
// Disable the final ARC autorelease.
AutoreleaseResult = false;
FinishFunction();
}
void CodeGenFunction::GenerateThunk(llvm::Function *Fn,
const CGFunctionInfo &FnInfo,
GlobalDecl GD, const ThunkInfo &Thunk) {
StartThunk(Fn, GD, FnInfo);
// Get our callee.
llvm::Type *Ty =
CGM.getTypes().GetFunctionType(CGM.getTypes().arrangeGlobalDeclaration(GD));
llvm::Value *Callee = CGM.GetAddrOfFunction(GD, Ty, /*ForVTable=*/true);
// Make the call and return the result.
EmitCallAndReturnForThunk(GD, Callee, &Thunk);
// Set the right linkage.
CGM.setFunctionLinkage(GD, Fn);
// Set the right visibility.
const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
setThunkVisibility(CGM, MD, Thunk, Fn);
}
void CodeGenVTables::emitThunk(GlobalDecl GD, const ThunkInfo &Thunk,
bool ForVTable) {
const CGFunctionInfo &FnInfo = CGM.getTypes().arrangeGlobalDeclaration(GD);
// FIXME: re-use FnInfo in this computation.
llvm::Constant *C = CGM.GetAddrOfThunk(GD, Thunk);
llvm::GlobalValue *Entry;
// Strip off a bitcast if we got one back.
if (llvm::ConstantExpr *CE = dyn_cast<llvm::ConstantExpr>(C)) {
assert(CE->getOpcode() == llvm::Instruction::BitCast);
Entry = cast<llvm::GlobalValue>(CE->getOperand(0));
} else {
Entry = cast<llvm::GlobalValue>(C);
}
// There's already a declaration with the same name, check if it has the same
// type or if we need to replace it.
if (Entry->getType()->getElementType() !=
CGM.getTypes().GetFunctionTypeForVTable(GD)) {
llvm::GlobalValue *OldThunkFn = Entry;
// If the types mismatch then we have to rewrite the definition.
assert(OldThunkFn->isDeclaration() &&
"Shouldn't replace non-declaration");
// Remove the name from the old thunk function and get a new thunk.
OldThunkFn->setName(StringRef());
Entry = cast<llvm::GlobalValue>(CGM.GetAddrOfThunk(GD, Thunk));
// If needed, replace the old thunk with a bitcast.
if (!OldThunkFn->use_empty()) {
llvm::Constant *NewPtrForOldDecl =
llvm::ConstantExpr::getBitCast(Entry, OldThunkFn->getType());
OldThunkFn->replaceAllUsesWith(NewPtrForOldDecl);
}
// Remove the old thunk.
OldThunkFn->eraseFromParent();
}
llvm::Function *ThunkFn = cast<llvm::Function>(Entry);
bool ABIHasKeyFunctions = CGM.getTarget().getCXXABI().hasKeyFunctions();
bool UseAvailableExternallyLinkage = ForVTable && ABIHasKeyFunctions;
if (!ThunkFn->isDeclaration()) {
if (!ABIHasKeyFunctions || UseAvailableExternallyLinkage) {
// There is already a thunk emitted for this function, do nothing.
return;
}
// Change the linkage.
CGM.setFunctionLinkage(GD, ThunkFn);
return;
}
CGM.SetLLVMFunctionAttributesForDefinition(GD.getDecl(), ThunkFn);
if (ThunkFn->isVarArg()) {
// Varargs thunks are special; we can't just generate a call because
// we can't copy the varargs. Our implementation is rather
// expensive/sucky at the moment, so don't generate the thunk unless
// we have to.
// FIXME: Do something better here; GenerateVarArgsThunk is extremely ugly.
if (!UseAvailableExternallyLinkage) {
CodeGenFunction(CGM).GenerateVarArgsThunk(ThunkFn, FnInfo, GD, Thunk);
CGM.getCXXABI().setThunkLinkage(ThunkFn, ForVTable);
}
} else {
// Normal thunk body generation.
CodeGenFunction(CGM).GenerateThunk(ThunkFn, FnInfo, GD, Thunk);
CGM.getCXXABI().setThunkLinkage(ThunkFn, ForVTable);
}
}
void CodeGenVTables::maybeEmitThunkForVTable(GlobalDecl GD,
const ThunkInfo &Thunk) {
// If the ABI has key functions, only the TU with the key function should emit
// the thunk. However, we can allow inlining of thunks if we emit them with
// available_externally linkage together with vtables when optimizations are
// enabled.
if (CGM.getTarget().getCXXABI().hasKeyFunctions() &&
!CGM.getCodeGenOpts().OptimizationLevel)
return;
// We can't emit thunks for member functions with incomplete types.
const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
if (!CGM.getTypes().isFuncTypeConvertible(
MD->getType()->castAs<FunctionType>()))
return;
emitThunk(GD, Thunk, /*ForVTable=*/true);
}
void CodeGenVTables::EmitThunks(GlobalDecl GD)
{
const CXXMethodDecl *MD =
cast<CXXMethodDecl>(GD.getDecl())->getCanonicalDecl();
// We don't need to generate thunks for the base destructor.
if (isa<CXXDestructorDecl>(MD) && GD.getDtorType() == Dtor_Base)
return;
const VTableContextBase::ThunkInfoVectorTy *ThunkInfoVector =
VTContext->getThunkInfo(GD);
if (!ThunkInfoVector)
return;
for (unsigned I = 0, E = ThunkInfoVector->size(); I != E; ++I)
emitThunk(GD, (*ThunkInfoVector)[I], /*ForVTable=*/false);
}
llvm::Constant *
CodeGenVTables::CreateVTableInitializer(const CXXRecordDecl *RD,
const VTableComponent *Components,
unsigned NumComponents,
const VTableLayout::VTableThunkTy *VTableThunks,
unsigned NumVTableThunks) {
SmallVector<llvm::Constant *, 64> Inits;
llvm::Type *Int8PtrTy = CGM.Int8PtrTy;
llvm::Type *PtrDiffTy =
CGM.getTypes().ConvertType(CGM.getContext().getPointerDiffType());
QualType ClassType = CGM.getContext().getTagDeclType(RD);
llvm::Constant *RTTI = CGM.GetAddrOfRTTIDescriptor(ClassType);
unsigned NextVTableThunkIndex = 0;
llvm::Constant *PureVirtualFn = nullptr, *DeletedVirtualFn = nullptr;
for (unsigned I = 0; I != NumComponents; ++I) {
VTableComponent Component = Components[I];
llvm::Constant *Init = nullptr;
switch (Component.getKind()) {
case VTableComponent::CK_VCallOffset:
Init = llvm::ConstantInt::get(PtrDiffTy,
Component.getVCallOffset().getQuantity());
Init = llvm::ConstantExpr::getIntToPtr(Init, Int8PtrTy);
break;
case VTableComponent::CK_VBaseOffset:
Init = llvm::ConstantInt::get(PtrDiffTy,
Component.getVBaseOffset().getQuantity());
Init = llvm::ConstantExpr::getIntToPtr(Init, Int8PtrTy);
break;
case VTableComponent::CK_OffsetToTop:
Init = llvm::ConstantInt::get(PtrDiffTy,
Component.getOffsetToTop().getQuantity());
Init = llvm::ConstantExpr::getIntToPtr(Init, Int8PtrTy);
break;
case VTableComponent::CK_RTTI:
Init = llvm::ConstantExpr::getBitCast(RTTI, Int8PtrTy);
break;
case VTableComponent::CK_FunctionPointer:
case VTableComponent::CK_CompleteDtorPointer:
case VTableComponent::CK_DeletingDtorPointer: {
GlobalDecl GD;
// Get the right global decl.
switch (Component.getKind()) {
default:
llvm_unreachable("Unexpected vtable component kind");
case VTableComponent::CK_FunctionPointer:
GD = Component.getFunctionDecl();
break;
case VTableComponent::CK_CompleteDtorPointer:
GD = GlobalDecl(Component.getDestructorDecl(), Dtor_Complete);
break;
case VTableComponent::CK_DeletingDtorPointer:
GD = GlobalDecl(Component.getDestructorDecl(), Dtor_Deleting);
break;
}
if (cast<CXXMethodDecl>(GD.getDecl())->isPure()) {
// We have a pure virtual member function.
if (!PureVirtualFn) {
llvm::FunctionType *Ty =
llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false);
StringRef PureCallName = CGM.getCXXABI().GetPureVirtualCallName();
PureVirtualFn = CGM.CreateRuntimeFunction(Ty, PureCallName);
PureVirtualFn = llvm::ConstantExpr::getBitCast(PureVirtualFn,
CGM.Int8PtrTy);
}
Init = PureVirtualFn;
} else if (cast<CXXMethodDecl>(GD.getDecl())->isDeleted()) {
if (!DeletedVirtualFn) {
llvm::FunctionType *Ty =
llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false);
StringRef DeletedCallName =
CGM.getCXXABI().GetDeletedVirtualCallName();
DeletedVirtualFn = CGM.CreateRuntimeFunction(Ty, DeletedCallName);
DeletedVirtualFn = llvm::ConstantExpr::getBitCast(DeletedVirtualFn,
CGM.Int8PtrTy);
}
Init = DeletedVirtualFn;
} else {
// Check if we should use a thunk.
if (NextVTableThunkIndex < NumVTableThunks &&
VTableThunks[NextVTableThunkIndex].first == I) {
const ThunkInfo &Thunk = VTableThunks[NextVTableThunkIndex].second;
maybeEmitThunkForVTable(GD, Thunk);
Init = CGM.GetAddrOfThunk(GD, Thunk);
NextVTableThunkIndex++;
} else {
llvm::Type *Ty = CGM.getTypes().GetFunctionTypeForVTable(GD);
Init = CGM.GetAddrOfFunction(GD, Ty, /*ForVTable=*/true);
}
Init = llvm::ConstantExpr::getBitCast(Init, Int8PtrTy);
}
break;
}
case VTableComponent::CK_UnusedFunctionPointer:
Init = llvm::ConstantExpr::getNullValue(Int8PtrTy);
break;
};
Inits.push_back(Init);
}
llvm::ArrayType *ArrayType = llvm::ArrayType::get(Int8PtrTy, NumComponents);
return llvm::ConstantArray::get(ArrayType, Inits);
}
llvm::GlobalVariable *
CodeGenVTables::GenerateConstructionVTable(const CXXRecordDecl *RD,
const BaseSubobject &Base,
bool BaseIsVirtual,
llvm::GlobalVariable::LinkageTypes Linkage,
VTableAddressPointsMapTy& AddressPoints) {
if (CGDebugInfo *DI = CGM.getModuleDebugInfo())
DI->completeClassData(Base.getBase());
std::unique_ptr<VTableLayout> VTLayout(
getItaniumVTableContext().createConstructionVTableLayout(
Base.getBase(), Base.getBaseOffset(), BaseIsVirtual, RD));
// Add the address points.
AddressPoints = VTLayout->getAddressPoints();
// Get the mangled construction vtable name.
SmallString<256> OutName;
llvm::raw_svector_ostream Out(OutName);
cast<ItaniumMangleContext>(CGM.getCXXABI().getMangleContext())
.mangleCXXCtorVTable(RD, Base.getBaseOffset().getQuantity(),
Base.getBase(), Out);
Out.flush();
StringRef Name = OutName.str();
llvm::ArrayType *ArrayType =
llvm::ArrayType::get(CGM.Int8PtrTy, VTLayout->getNumVTableComponents());
// Construction vtable symbols are not part of the Itanium ABI, so we cannot
// guarantee that they actually will be available externally. Instead, when
// emitting an available_externally VTT, we provide references to an internal
// linkage construction vtable. The ABI only requires complete-object vtables
// to be the same for all instances of a type, not construction vtables.
if (Linkage == llvm::GlobalVariable::AvailableExternallyLinkage)
Linkage = llvm::GlobalVariable::InternalLinkage;
// Create the variable that will hold the construction vtable.
llvm::GlobalVariable *VTable =
CGM.CreateOrReplaceCXXRuntimeVariable(Name, ArrayType, Linkage);
CGM.setGlobalVisibility(VTable, RD);
// V-tables are always unnamed_addr.
VTable->setUnnamedAddr(true);
// Create and set the initializer.
llvm::Constant *Init =
CreateVTableInitializer(Base.getBase(),
VTLayout->vtable_component_begin(),
VTLayout->getNumVTableComponents(),
VTLayout->vtable_thunk_begin(),
VTLayout->getNumVTableThunks());
VTable->setInitializer(Init);
return VTable;
}
/// Compute the required linkage of the v-table for the given class.
///
/// Note that we only call this at the end of the translation unit.
llvm::GlobalVariable::LinkageTypes
CodeGenModule::getVTableLinkage(const CXXRecordDecl *RD) {
if (!RD->isExternallyVisible())
return llvm::GlobalVariable::InternalLinkage;
// We're at the end of the translation unit, so the current key
// function is fully correct.
if (const CXXMethodDecl *keyFunction = Context.getCurrentKeyFunction(RD)) {
// If this class has a key function, use that to determine the
// linkage of the vtable.
const FunctionDecl *def = nullptr;
if (keyFunction->hasBody(def))
keyFunction = cast<CXXMethodDecl>(def);
switch (keyFunction->getTemplateSpecializationKind()) {
case TSK_Undeclared:
case TSK_ExplicitSpecialization:
assert(def && "Should not have been asked to emit this");
if (keyFunction->isInlined())
return !Context.getLangOpts().AppleKext ?
llvm::GlobalVariable::LinkOnceODRLinkage :
llvm::Function::InternalLinkage;
return llvm::GlobalVariable::ExternalLinkage;
case TSK_ImplicitInstantiation:
return !Context.getLangOpts().AppleKext ?
llvm::GlobalVariable::LinkOnceODRLinkage :
llvm::Function::InternalLinkage;
case TSK_ExplicitInstantiationDefinition:
return !Context.getLangOpts().AppleKext ?
llvm::GlobalVariable::WeakODRLinkage :
llvm::Function::InternalLinkage;
case TSK_ExplicitInstantiationDeclaration:
llvm_unreachable("Should not have been asked to emit this");
}
}
// -fapple-kext mode does not support weak linkage, so we must use
// internal linkage.
if (Context.getLangOpts().AppleKext)
return llvm::Function::InternalLinkage;
llvm::GlobalVariable::LinkageTypes DiscardableODRLinkage =
llvm::GlobalValue::LinkOnceODRLinkage;
llvm::GlobalVariable::LinkageTypes NonDiscardableODRLinkage =
llvm::GlobalValue::WeakODRLinkage;
if (RD->hasAttr<DLLExportAttr>()) {
// Cannot discard exported vtables.
DiscardableODRLinkage = NonDiscardableODRLinkage;
} else if (RD->hasAttr<DLLImportAttr>()) {
// Imported vtables are available externally.
DiscardableODRLinkage = llvm::GlobalVariable::AvailableExternallyLinkage;
NonDiscardableODRLinkage = llvm::GlobalVariable::AvailableExternallyLinkage;
}
switch (RD->getTemplateSpecializationKind()) {
case TSK_Undeclared:
case TSK_ExplicitSpecialization:
case TSK_ImplicitInstantiation:
return DiscardableODRLinkage;
case TSK_ExplicitInstantiationDeclaration:
llvm_unreachable("Should not have been asked to emit this");
case TSK_ExplicitInstantiationDefinition:
return NonDiscardableODRLinkage;
}
llvm_unreachable("Invalid TemplateSpecializationKind!");
}
/// This is a callback from Sema to tell us that it believes that a
/// particular v-table is required to be emitted in this translation
/// unit.
///
/// The reason we don't simply trust this callback is because Sema
/// will happily report that something is used even when it's used
/// only in code that we don't actually have to emit.
///
/// \param isRequired - if true, the v-table is mandatory, e.g.
/// because the translation unit defines the key function
void CodeGenModule::EmitVTable(CXXRecordDecl *theClass, bool isRequired) {
if (!isRequired) return;
VTables.GenerateClassData(theClass);
}
void
CodeGenVTables::GenerateClassData(const CXXRecordDecl *RD) {
if (CGDebugInfo *DI = CGM.getModuleDebugInfo())
DI->completeClassData(RD);
if (RD->getNumVBases())
CGM.getCXXABI().emitVirtualInheritanceTables(RD);
CGM.getCXXABI().emitVTableDefinitions(*this, RD);
}
/// At this point in the translation unit, does it appear that can we
/// rely on the vtable being defined elsewhere in the program?
///
/// The response is really only definitive when called at the end of
/// the translation unit.
///
/// The only semantic restriction here is that the object file should
/// not contain a v-table definition when that v-table is defined
/// strongly elsewhere. Otherwise, we'd just like to avoid emitting
/// v-tables when unnecessary.
bool CodeGenVTables::isVTableExternal(const CXXRecordDecl *RD) {
assert(RD->isDynamicClass() && "Non-dynamic classes have no VTable.");
// If we have an explicit instantiation declaration (and not a
// definition), the v-table is defined elsewhere.
TemplateSpecializationKind TSK = RD->getTemplateSpecializationKind();
if (TSK == TSK_ExplicitInstantiationDeclaration)
return true;
// Otherwise, if the class is an instantiated template, the
// v-table must be defined here.
if (TSK == TSK_ImplicitInstantiation ||
TSK == TSK_ExplicitInstantiationDefinition)
return false;
// Otherwise, if the class doesn't have a key function (possibly
// anymore), the v-table must be defined here.
const CXXMethodDecl *keyFunction = CGM.getContext().getCurrentKeyFunction(RD);
if (!keyFunction)
return false;
// Otherwise, if we don't have a definition of the key function, the
// v-table must be defined somewhere else.
return !keyFunction->hasBody();
}
/// Given that we're currently at the end of the translation unit, and
/// we've emitted a reference to the v-table for this class, should
/// we define that v-table?
static bool shouldEmitVTableAtEndOfTranslationUnit(CodeGenModule &CGM,
const CXXRecordDecl *RD) {
return !CGM.getVTables().isVTableExternal(RD);
}
/// Given that at some point we emitted a reference to one or more
/// v-tables, and that we are now at the end of the translation unit,
/// decide whether we should emit them.
void CodeGenModule::EmitDeferredVTables() {
#ifndef NDEBUG
// Remember the size of DeferredVTables, because we're going to assume
// that this entire operation doesn't modify it.
size_t savedSize = DeferredVTables.size();
#endif
typedef std::vector<const CXXRecordDecl *>::const_iterator const_iterator;
for (const_iterator i = DeferredVTables.begin(),
e = DeferredVTables.end(); i != e; ++i) {
const CXXRecordDecl *RD = *i;
if (shouldEmitVTableAtEndOfTranslationUnit(*this, RD))
VTables.GenerateClassData(RD);
}
assert(savedSize == DeferredVTables.size() &&
"deferred extra v-tables during v-table emission?");
DeferredVTables.clear();
}
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