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Clang: Fix elementtype attribute mismatch in thunk generation #336

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Clang: Fix elementtype attribute mismatch in thunk generation #336

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33 changes: 20 additions & 13 deletions clang/lib/CodeGen/CGVTables.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -586,31 +586,37 @@ llvm::Constant *CodeGenVTables::maybeEmitThunk(GlobalDecl GD,
// CHEERP: If there are virtual bases it is possible that the type of `this` mismatches
// between the existing and new think, but one is directbase of the other.
// We keep the thunk with the most basic `this` type

if (!ThunkFn->hasParamAttribute(thisIndex, llvm::Attribute::ElementType))
ThunkFn->addParamAttr(thisIndex, llvm::Attribute::get(CGM.getLLVMContext(), llvm::Attribute::ElementType, CurrentThisTy));

bool NewIsDirectBase = false;
bool CurrentIsDirectBase = false;
if (!CGM.getTarget().isByteAddressable()) {
// Geth the `this` type. It can be the first or second parameter (if there is a
// Get the `this` type. It can be the first or second parameter (if there is a
// struct return pointer)
llvm::StructType* CurrentThisStructTy = cast<llvm::StructType>(CurrentThisTy);
llvm::StructType* NewThisTy = cast<llvm::StructType>(ThunkFn->getParamAttribute(thisIndex, llvm::Attribute::ElementType).getValueAsType());

// Check if one of the types is directbase of the other (check all the directbase hierarchy)
for (llvm::StructType* I = NewThisTy; I != nullptr; I = I->getDirectBase()) {
if (I == CurrentThisTy) {
NewIsDirectBase = true;
break;
// If the attribute type is the same as current, or doesn't exist, skip the directbase check
if (NewThisTy && NewThisTy != CurrentThisTy) {
// Check if one of the types is directbase of the other (check all the directbase hierarchy)
for (llvm::StructType* I = NewThisTy; I != nullptr; I = I->getDirectBase()) {
if (I == CurrentThisTy) {
NewIsDirectBase = true;
break;
}
}
}
for (llvm::StructType* I = CurrentThisStructTy; I != nullptr; I = I->getDirectBase()) {
if (I == NewThisTy) {
CurrentIsDirectBase = true;
break;
for (llvm::StructType* I = CurrentThisStructTy; I != nullptr; I = I->getDirectBase()) {
if (I == NewThisTy) {
CurrentIsDirectBase = true;
break;
}
}
}
}

if (ThunkFn->getFunctionType() != ThunkFnTy && !NewIsDirectBase) {
llvm::GlobalValue *OldThunkFn = ThunkFn;

// If the types mismatch then we have to rewrite the definition.
assert((OldThunkFn->isDeclaration() || CurrentIsDirectBase) &&
"Shouldn't replace non-declaration");
Expand All @@ -634,6 +640,7 @@ llvm::Constant *CodeGenVTables::maybeEmitThunk(GlobalDecl GD,
OldThunkFn->eraseFromParent();
}


bool ABIHasKeyFunctions = CGM.getTarget().getCXXABI().hasKeyFunctions();
bool UseAvailableExternallyLinkage = ForVTable && ABIHasKeyFunctions;

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