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CodeGen: Kill FillInNullDataMemberPointers 

It exists to handle the case where base subobjects are character arrays.
This never happens.

llvm-svn: 220006
This commit is contained in:
David Majnemer 2014-10-17 01:00:43 +00:00
parent f707f0f6bb
commit 2213bfe352
1 changed files with 3 additions and 106 deletions
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109
clang/lib/CodeGen/CGExprConstant.cpp
View File

@ -1270,83 +1270,6 @@ CodeGenModule::getMemberPointerConstant(const UnaryOperator *uo) {
return getCXXABI().EmitMemberDataPointer(type, chars);
}
static void
FillInNullDataMemberPointers(CodeGenModule &CGM, QualType T,
SmallVectorImpl<llvm::Constant *> &Elements,
uint64_t StartOffset) {
assert(StartOffset % CGM.getContext().getCharWidth() == 0 &&
"StartOffset not byte aligned!");
if (CGM.getTypes().isZeroInitializable(T))
return;
if (const ConstantArrayType *CAT =
CGM.getContext().getAsConstantArrayType(T)) {
QualType ElementTy = CAT->getElementType();
uint64_t ElementSize = CGM.getContext().getTypeSize(ElementTy);
for (uint64_t I = 0, E = CAT->getSize().getZExtValue(); I != E; ++I) {
FillInNullDataMemberPointers(CGM, ElementTy, Elements,
StartOffset + I * ElementSize);
}
} else if (const RecordType *RT = T->getAs<RecordType>()) {
const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
// Go through all bases and fill in any null pointer to data members.
for (const auto &I : RD->bases()) {
if (I.isVirtual()) {
// Ignore virtual bases.
continue;
}
const CXXRecordDecl *BaseDecl =
cast<CXXRecordDecl>(I.getType()->getAs<RecordType>()->getDecl());
// Ignore empty bases.
if (BaseDecl->isEmpty())
continue;
// Ignore bases that don't have any pointer to data members.
if (CGM.getTypes().isZeroInitializable(BaseDecl))
continue;
uint64_t BaseOffset =
CGM.getContext().toBits(Layout.getBaseClassOffset(BaseDecl));
FillInNullDataMemberPointers(CGM, I.getType(),
Elements, StartOffset + BaseOffset);
}
// Visit all fields.
unsigned FieldNo = 0;
for (RecordDecl::field_iterator I = RD->field_begin(),
E = RD->field_end(); I != E; ++I, ++FieldNo) {
QualType FieldType = I->getType();
if (CGM.getTypes().isZeroInitializable(FieldType))
continue;
uint64_t FieldOffset = StartOffset + Layout.getFieldOffset(FieldNo);
FillInNullDataMemberPointers(CGM, FieldType, Elements, FieldOffset);
}
} else {
assert(T->isMemberPointerType() && "Should only see member pointers here!");
assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() &&
"Should only see pointers to data members here!");
CharUnits StartIndex = CGM.getContext().toCharUnitsFromBits(StartOffset);
CharUnits EndIndex = StartIndex + CGM.getContext().getTypeSizeInChars(T);
// FIXME: hardcodes Itanium member pointer representation!
llvm::Constant *NegativeOne =
llvm::ConstantInt::get(CGM.Int8Ty, -1ULL, /*isSigned*/true);
// Fill in the null data member pointer.
for (CharUnits I = StartIndex; I != EndIndex; ++I)
Elements[I.getQuantity()] = NegativeOne;
}
}
static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM,
llvm::Type *baseType,
const CXXRecordDecl *base);
@ -1435,32 +1358,8 @@ static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM,
if (baseLayout.isZeroInitializableAsBase())
return llvm::Constant::getNullValue(baseType);
// If the base type is a struct, we can just use its null constant.
if (isa<llvm::StructType>(baseType)) {
return EmitNullConstant(CGM, base, /*complete*/ false);
}
// Otherwise, some bases are represented as arrays of i8 if the size
// of the base is smaller than its corresponding LLVM type. Figure
// out how many elements this base array has.
llvm::ArrayType *baseArrayType = cast<llvm::ArrayType>(baseType);
unsigned numBaseElements = baseArrayType->getNumElements();
// Fill in null data member pointers.
SmallVector<llvm::Constant *, 16> baseElements(numBaseElements);
FillInNullDataMemberPointers(CGM, CGM.getContext().getTypeDeclType(base),
baseElements, 0);
// Now go through all other elements and zero them out.
if (numBaseElements) {
llvm::Constant *i8_zero = llvm::Constant::getNullValue(CGM.Int8Ty);
for (unsigned i = 0; i != numBaseElements; ++i) {
if (!baseElements[i])
baseElements[i] = i8_zero;
}
}
return llvm::ConstantArray::get(baseArrayType, baseElements);
// Otherwise, we can just use its null constant.
return EmitNullConstant(CGM, base, /*asCompleteObject=*/false);
}
llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) {
@ -1491,9 +1390,7 @@ llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) {
assert(T->isMemberPointerType() && "Should only see member pointers here!");
assert(!T->getAs<MemberPointerType>()->getPointeeType()->isFunctionType() &&
"Should only see pointers to data members here!");
// Itanium C++ ABI 2.3:
// A NULL pointer is represented as -1.
return getCXXABI().EmitNullMemberPointer(T->castAs<MemberPointerType>());
}