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llvm-project/clang/lib/CodeGen/CGVTables.cpp
Peter Collingbourne 2c7f7e31c4 CFI: Introduce -fsanitize=cfi-icall flag. 
This flag causes the compiler to emit bit set entries for functions as well
as runtime bitset checks at indirect call sites. Depends on the new function
bitset mechanism.

Differential Revision: http://reviews.llvm.org/D11857

llvm-svn: 247238
2015-09-10 02:17:40 +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);
llvm::Type *Ty = getTypes().GetFunctionTypeForVTable(GD);
return GetOrCreateLLVMFunction(Name, Ty, GD, /*ForVTable=*/true,
/*DontDefer=*/true, /*IsThunk=*/true);
}
static void setThunkVisibility(CodeGenModule &CGM, const CXXMethodDecl *MD,
const ThunkInfo &Thunk, llvm::Function *Fn) {
CGM.setGlobalVisibility(Fn, MD);
}
static void setThunkProperties(CodeGenModule &CGM, const ThunkInfo &Thunk,
llvm::Function *ThunkFn, bool ForVTable,
GlobalDecl GD) {
CGM.setFunctionLinkage(GD, ThunkFn);
CGM.getCXXABI().setThunkLinkage(ThunkFn, ForVTable, GD,
!Thunk.Return.isEmpty());
// Set the right visibility.
const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
setThunkVisibility(CGM, MD, Thunk, ThunkFn);
if (CGM.supportsCOMDAT() && ThunkFn->isWeakForLinker())
ThunkFn->setComdat(CGM.getModule().getOrInsertComdat(ThunkFn->getName()));
}
#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);
}
auto ClassDecl = ResultType->getPointeeType()->getAsCXXRecordDecl();
auto ClassAlign = CGF.CGM.getClassPointerAlignment(ClassDecl);
ReturnValue = CGF.CGM.getCXXABI().performReturnAdjustment(CGF,
Address(ReturnValue, ClassAlign),
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.
llvm::Function *
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".
Address ThisPtr(&*AI, CGM.getClassPointerAlignment(MD->getParent()));
llvm::BasicBlock *EntryBB = Fn->begin();
llvm::Instruction *ThisStore =
std::find_if(EntryBB->begin(), EntryBB->end(), [&](llvm::Instruction &I) {
return isa<llvm::StoreInst>(I) && I.getOperand(0) == ThisPtr.getPointer();
});
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::BasicBlock &BB : *Fn) {
llvm::Instruction *T = BB.getTerminator();
if (isa<llvm::ReturnInst>(T)) {
RValue RV = RValue::get(T->getOperand(0));
T->eraseFromParent();
Builder.SetInsertPoint(&BB);
RV = PerformReturnAdjustment(*this, ResultType, RV, Thunk);
Builder.CreateRet(RV.getScalarVal());
break;
}
}
}
return Fn;
}
void CodeGenFunction::StartThunk(llvm::Function *Fn, GlobalDecl GD,
const CGFunctionInfo &FnInfo) {
assert(!CurGD.getDecl() && "CurGD was already set!");
CurGD = GD;
CurFuncIsThunk = true;
// 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
: CGM.getCXXABI().hasMostDerivedReturn(GD)
? CGM.getContext().VoidPtrTy
: FPT->getReturnType();
FunctionArgList FunctionArgs;
// Create the implicit 'this' parameter declaration.
CGM.getCXXABI().buildThisParam(*this, FunctionArgs);
// Add the rest of the parameters.
FunctionArgs.append(MD->param_begin(), MD->param_end());
if (isa<CXXDestructorDecl>(MD))
CGM.getCXXABI().addImplicitStructorParams(*this, ResultType, FunctionArgs);
// Start defining the function.
StartFunction(GlobalDecl(), ResultType, Fn, FnInfo, FunctionArgs,
MD->getLocation(), MD->getLocation());
// Since we didn't pass a GlobalDecl to StartFunction, do this ourselves.
CGM.getCXXABI().EmitInstanceFunctionProlog(*this);
CXXThisValue = CXXABIThisValue;
CurCodeDecl = MD;
CurFuncDecl = MD;
}
void CodeGenFunction::FinishThunk() {
// Clear these to restore the invariants expected by
// StartFunction/FinishFunction.
CurCodeDecl = nullptr;
CurFuncDecl = nullptr;
FinishFunction();
}
void CodeGenFunction::EmitCallAndReturnForThunk(llvm::Value *Callee,
const ThunkInfo *Thunk) {
assert(isa<CXXMethodDecl>(CurGD.getDecl()) &&
"Please use a new CGF for this thunk");
const CXXMethodDecl *MD = cast<CXXMethodDecl>(CurGD.getDecl());
// Adjust the 'this' pointer if necessary
llvm::Value *AdjustedThisPtr =
Thunk ? CGM.getCXXABI().performThisAdjustment(
*this, LoadCXXThisAddress(), Thunk->This)
: LoadCXXThis();
if (CurFnInfo->usesInAlloca()) {
// We don't handle return adjusting thunks, because they require us to call
// the copy constructor. For now, fall through and pretend the return
// adjustment was empty so we don't crash.
if (Thunk && !Thunk->Return.isEmpty()) {
CGM.ErrorUnsupported(
MD, "non-trivial argument copy for return-adjusting thunk");
}
EmitMustTailThunk(MD, AdjustedThisPtr, Callee);
return;
}
// Start building CallArgs.
CallArgList CallArgs;
QualType ThisType = MD->getThisType(getContext());
CallArgs.add(RValue::get(AdjustedThisPtr), ThisType);
if (isa<CXXDestructorDecl>(MD))
CGM.getCXXABI().adjustCallArgsForDestructorThunk(*this, CurGD, CallArgs);
// Add the rest of the arguments.
for (const ParmVarDecl *PD : MD->params())
EmitDelegateCallArg(CallArgs, PD, PD->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(CurGD)
? ThisType
: CGM.getCXXABI().hasMostDerivedReturn(CurGD)
? CGM.getContext().VoidPtrTy
: FPT->getReturnType();
ReturnValueSlot Slot;
if (!ResultType->isVoidType() &&
CurFnInfo->getReturnInfo().getKind() == ABIArgInfo::Indirect &&
!hasScalarEvaluationKind(CurFnInfo->getReturnType()))
Slot = ReturnValueSlot(ReturnValue, ResultType.isVolatileQualified());
// Now emit our call.
llvm::Instruction *CallOrInvoke;
RValue RV = EmitCall(*CurFnInfo, Callee, Slot, CallArgs, MD, &CallOrInvoke);
// Consider return adjustment if we have ThunkInfo.
if (Thunk && !Thunk->Return.isEmpty())
RV = PerformReturnAdjustment(*this, ResultType, RV, *Thunk);
else if (llvm::CallInst* Call = dyn_cast<llvm::CallInst>(CallOrInvoke))
Call->setTailCallKind(llvm::CallInst::TCK_Tail);
// Emit return.
if (!ResultType->isVoidType() && Slot.isNull())
CGM.getCXXABI().EmitReturnFromThunk(*this, RV, ResultType);
// Disable the final ARC autorelease.
AutoreleaseResult = false;
FinishThunk();
}
void CodeGenFunction::EmitMustTailThunk(const CXXMethodDecl *MD,
llvm::Value *AdjustedThisPtr,
llvm::Value *Callee) {
// Emitting a musttail call thunk doesn't use any of the CGCall.cpp machinery
// to translate AST arguments into LLVM IR arguments. For thunks, we know
// that the caller prototype more or less matches the callee prototype with
// the exception of 'this'.
SmallVector<llvm::Value *, 8> Args;
for (llvm::Argument &A : CurFn->args())
Args.push_back(&A);
// Set the adjusted 'this' pointer.
const ABIArgInfo &ThisAI = CurFnInfo->arg_begin()->info;
if (ThisAI.isDirect()) {
const ABIArgInfo &RetAI = CurFnInfo->getReturnInfo();
int ThisArgNo = RetAI.isIndirect() && !RetAI.isSRetAfterThis() ? 1 : 0;
llvm::Type *ThisType = Args[ThisArgNo]->getType();
if (ThisType != AdjustedThisPtr->getType())
AdjustedThisPtr = Builder.CreateBitCast(AdjustedThisPtr, ThisType);
Args[ThisArgNo] = AdjustedThisPtr;
} else {
assert(ThisAI.isInAlloca() && "this is passed directly or inalloca");
Address ThisAddr = GetAddrOfLocalVar(CXXABIThisDecl);
llvm::Type *ThisType = ThisAddr.getElementType();
if (ThisType != AdjustedThisPtr->getType())
AdjustedThisPtr = Builder.CreateBitCast(AdjustedThisPtr, ThisType);
Builder.CreateStore(AdjustedThisPtr, ThisAddr);
}
// Emit the musttail call manually. Even if the prologue pushed cleanups, we
// don't actually want to run them.
llvm::CallInst *Call = Builder.CreateCall(Callee, Args);
Call->setTailCallKind(llvm::CallInst::TCK_MustTail);
// Apply the standard set of call attributes.
unsigned CallingConv;
CodeGen::AttributeListType AttributeList;
CGM.ConstructAttributeList(*CurFnInfo, MD, AttributeList, CallingConv,
/*AttrOnCallSite=*/true);
llvm::AttributeSet Attrs =
llvm::AttributeSet::get(getLLVMContext(), AttributeList);
Call->setAttributes(Attrs);
Call->setCallingConv(static_cast<llvm::CallingConv::ID>(CallingConv));
if (Call->getType()->isVoidTy())
Builder.CreateRetVoid();
else
Builder.CreateRet(Call);
// Finish the function to maintain CodeGenFunction invariants.
// FIXME: Don't emit unreachable code.
EmitBlock(createBasicBlock());
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(Callee, &Thunk);
}
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;
}
setThunkProperties(CGM, Thunk, ThunkFn, ForVTable, GD);
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)
return;
ThunkFn =
CodeGenFunction(CGM).GenerateVarArgsThunk(ThunkFn, FnInfo, GD, Thunk);
} else {
// Normal thunk body generation.
CodeGenFunction(CGM).generateThunk(ThunkFn, FnInfo, GD, Thunk);
}
setThunkProperties(CGM, Thunk, ThunkFn, ForVTable, GD);
}
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 (const ThunkInfo& Thunk : *ThunkInfoVector)
emitThunk(GD, Thunk, /*ForVTable=*/false);
}
llvm::Constant *CodeGenVTables::CreateVTableInitializer(
const CXXRecordDecl *RD, const VTableComponent *Components,
unsigned NumComponents, const VTableLayout::VTableThunkTy *VTableThunks,
unsigned NumVTableThunks, llvm::Constant *RTTI) {
SmallVector<llvm::Constant *, 64> Inits;
llvm::Type *Int8PtrTy = CGM.Int8PtrTy;
llvm::Type *PtrDiffTy =
CGM.getTypes().ConvertType(CGM.getContext().getPointerDiffType());
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);
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);
llvm::Constant *RTTI = CGM.GetAddrOfRTTIDescriptor(
CGM.getContext().getTagDeclType(Base.getBase()));
// Create and set the initializer.
llvm::Constant *Init = CreateVTableInitializer(
Base.getBase(), VTLayout->vtable_component_begin(),
VTLayout->getNumVTableComponents(), VTLayout->vtable_thunk_begin(),
VTLayout->getNumVTableThunks(), RTTI);
VTable->setInitializer(Init);
CGM.EmitVTableBitSetEntries(VTable, *VTLayout.get());
return VTable;
}
static bool shouldEmitAvailableExternallyVTable(const CodeGenModule &CGM,
const CXXRecordDecl *RD) {
return CGM.getCodeGenOpts().OptimizationLevel > 0 &&
CGM.getCXXABI().canSpeculativelyEmitVTable(RD);
}
/// 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.
const CXXMethodDecl *keyFunction = Context.getCurrentKeyFunction(RD);
if (keyFunction && !RD->hasAttr<DLLImportAttr>()) {
// 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 || CodeGenOpts.OptimizationLevel > 0) &&
"Shouldn't query vtable linkage without key function or "
"optimizations");
if (!def && CodeGenOpts.OptimizationLevel > 0)
return llvm::GlobalVariable::AvailableExternallyLinkage;
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:
return shouldEmitAvailableExternallyVTable(*this, RD)
? llvm::GlobalVariable::AvailableExternallyLinkage
: llvm::GlobalVariable::ExternalLinkage;
case TSK_ExplicitInstantiationDefinition:
return NonDiscardableODRLinkage;
}
llvm_unreachable("Invalid TemplateSpecializationKind!");
}
/// This is a callback from Sema to tell us that that a particular v-table is
/// required to be emitted in this translation unit.
///
/// This is only called for vtables that _must_ be emitted (mainly due to key
/// functions). For weak vtables, CodeGen tracks when they are needed and
/// emits them as-needed.
void CodeGenModule::EmitVTable(CXXRecordDecl *theClass) {
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) {
// If vtable is internal then it has to be done.
if (!CGM.getVTables().isVTableExternal(RD))
return true;
// If it's external then maybe we will need it as available_externally.
return shouldEmitAvailableExternallyVTable(CGM, 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
for (const CXXRecordDecl *RD : DeferredVTables)
if (shouldEmitVTableAtEndOfTranslationUnit(*this, RD))
VTables.GenerateClassData(RD);
assert(savedSize == DeferredVTables.size() &&
"deferred extra v-tables during v-table emission?");
DeferredVTables.clear();
}
bool CodeGenModule::IsCFIBlacklistedRecord(const CXXRecordDecl *RD) {
if (RD->hasAttr<UuidAttr>() &&
getContext().getSanitizerBlacklist().isBlacklistedType("attr:uuid"))
return true;
return getContext().getSanitizerBlacklist().isBlacklistedType(
RD->getQualifiedNameAsString());
}
void CodeGenModule::EmitVTableBitSetEntries(llvm::GlobalVariable *VTable,
const VTableLayout &VTLayout) {
if (!LangOpts.Sanitize.has(SanitizerKind::CFIVCall) &&
!LangOpts.Sanitize.has(SanitizerKind::CFINVCall) &&
!LangOpts.Sanitize.has(SanitizerKind::CFIDerivedCast) &&
!LangOpts.Sanitize.has(SanitizerKind::CFIUnrelatedCast))
return;
CharUnits PointerWidth =
Context.toCharUnitsFromBits(Context.getTargetInfo().getPointerWidth(0));
typedef std::pair<const CXXRecordDecl *, unsigned> BSEntry;
std::vector<BSEntry> BitsetEntries;
// Create a bit set entry for each address point.
for (auto &&AP : VTLayout.getAddressPoints()) {
if (IsCFIBlacklistedRecord(AP.first.getBase()))
continue;
BitsetEntries.push_back(std::make_pair(AP.first.getBase(), AP.second));
}
// Sort the bit set entries for determinism.
std::sort(BitsetEntries.begin(), BitsetEntries.end(),
[this](const BSEntry &E1, const BSEntry &E2) {
if (&E1 == &E2)
return false;
std::string S1;
llvm::raw_string_ostream O1(S1);
getCXXABI().getMangleContext().mangleTypeName(
QualType(E1.first->getTypeForDecl(), 0), O1);
O1.flush();
std::string S2;
llvm::raw_string_ostream O2(S2);
getCXXABI().getMangleContext().mangleTypeName(
QualType(E2.first->getTypeForDecl(), 0), O2);
O2.flush();
if (S1 < S2)
return true;
if (S1 != S2)
return false;
return E1.second < E2.second;
});
llvm::NamedMDNode *BitsetsMD =
getModule().getOrInsertNamedMetadata("llvm.bitsets");
for (auto BitsetEntry : BitsetEntries)
BitsetsMD->addOperand(CreateVTableBitSetEntry(
VTable, PointerWidth * BitsetEntry.second, BitsetEntry.first));
}
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