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[clang][bytecode] Use stack offsets for This/RVO ptrs #160285

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Sep 24, 2025
Merged

[clang][bytecode] Use stack offsets for This/RVO ptrs #160285

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db4f054
[clang][bytecode] Use stack offsets for This/RVO ptrs
tbaederr Sep 23, 2025
d59c1fe
Clarify comment
tbaederr Sep 24, 2025
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8 changes: 4 additions & 4 deletions clang/lib/AST/ByteCode/Interp.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1027,8 +1027,8 @@ static bool CheckCallDepth(InterpState &S, CodePtr OpPC) {
return true;
}

bool CheckThis(InterpState &S, CodePtr OpPC, const Pointer &This) {
if (!This.isZero())
bool CheckThis(InterpState &S, CodePtr OpPC) {
if (S.Current->hasThisPointer())
return true;

const Expr *E = S.Current->getExpr(OpPC);
Expand Down Expand Up @@ -1198,8 +1198,8 @@ static bool runRecordDestructor(InterpState &S, CodePtr OpPC,
const Record *R = Desc->ElemRecord;
assert(R);

if (Pointer::pointToSameBlock(BasePtr, S.Current->getThis()) &&
S.Current->getFunction()->isDestructor()) {
if (S.Current->hasThisPointer() && S.Current->getFunction()->isDestructor() &&
Pointer::pointToSameBlock(BasePtr, S.Current->getThis())) {
const SourceInfo &Loc = S.Current->getSource(OpPC);
S.FFDiag(Loc, diag::note_constexpr_double_destroy);
return false;
Expand Down
50 changes: 25 additions & 25 deletions clang/lib/AST/ByteCode/Interp.h
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Original file line number Diff line number Diff line change
Expand Up @@ -104,7 +104,7 @@ bool CheckStore(InterpState &S, CodePtr OpPC, const Pointer &Ptr);
bool CheckInit(InterpState &S, CodePtr OpPC, const Pointer &Ptr);

/// Checks the 'this' pointer.
bool CheckThis(InterpState &S, CodePtr OpPC, const Pointer &This);
bool CheckThis(InterpState &S, CodePtr OpPC);

/// Checks if dynamic memory allocation is available in the current
/// language mode.
Expand Down Expand Up @@ -1440,9 +1440,9 @@ template <PrimType Name, class T = typename PrimConv<Name>::T>
bool GetThisField(InterpState &S, CodePtr OpPC, uint32_t I) {
if (S.checkingPotentialConstantExpression())
return false;
const Pointer &This = S.Current->getThis();
if (!CheckThis(S, OpPC, This))
if (!CheckThis(S, OpPC))
return false;
const Pointer &This = S.Current->getThis();
const Pointer &Field = This.atField(I);
if (!CheckLoad(S, OpPC, Field))
return false;
Expand All @@ -1454,10 +1454,10 @@ template <PrimType Name, class T = typename PrimConv<Name>::T>
bool SetThisField(InterpState &S, CodePtr OpPC, uint32_t I) {
if (S.checkingPotentialConstantExpression())
return false;
if (!CheckThis(S, OpPC))
return false;
const T &Value = S.Stk.pop<T>();
const Pointer &This = S.Current->getThis();
if (!CheckThis(S, OpPC, This))
return false;
const Pointer &Field = This.atField(I);
if (!CheckStore(S, OpPC, Field))
return false;
Expand Down Expand Up @@ -1560,9 +1560,9 @@ template <PrimType Name, class T = typename PrimConv<Name>::T>
bool InitThisField(InterpState &S, CodePtr OpPC, uint32_t I) {
if (S.checkingPotentialConstantExpression() && S.Current->getDepth() == 0)
return false;
const Pointer &This = S.Current->getThis();
if (!CheckThis(S, OpPC, This))
if (!CheckThis(S, OpPC))
return false;
const Pointer &This = S.Current->getThis();
const Pointer &Field = This.atField(I);
assert(Field.canBeInitialized());
Field.deref<T>() = S.Stk.pop<T>();
Expand All @@ -1574,9 +1574,9 @@ template <PrimType Name, class T = typename PrimConv<Name>::T>
bool InitThisFieldActivate(InterpState &S, CodePtr OpPC, uint32_t I) {
if (S.checkingPotentialConstantExpression() && S.Current->getDepth() == 0)
return false;
const Pointer &This = S.Current->getThis();
if (!CheckThis(S, OpPC, This))
if (!CheckThis(S, OpPC))
return false;
const Pointer &This = S.Current->getThis();
const Pointer &Field = This.atField(I);
assert(Field.canBeInitialized());
Field.deref<T>() = S.Stk.pop<T>();
Expand All @@ -1593,9 +1593,9 @@ bool InitThisBitField(InterpState &S, CodePtr OpPC, const Record::Field *F,
assert(F->isBitField());
if (S.checkingPotentialConstantExpression() && S.Current->getDepth() == 0)
return false;
const Pointer &This = S.Current->getThis();
if (!CheckThis(S, OpPC, This))
if (!CheckThis(S, OpPC))
return false;
const Pointer &This = S.Current->getThis();
const Pointer &Field = This.atField(FieldOffset);
assert(Field.canBeInitialized());
const auto &Value = S.Stk.pop<T>();
Expand All @@ -1610,9 +1610,9 @@ bool InitThisBitFieldActivate(InterpState &S, CodePtr OpPC,
assert(F->isBitField());
if (S.checkingPotentialConstantExpression() && S.Current->getDepth() == 0)
return false;
const Pointer &This = S.Current->getThis();
if (!CheckThis(S, OpPC, This))
if (!CheckThis(S, OpPC))
return false;
const Pointer &This = S.Current->getThis();
const Pointer &Field = This.atField(FieldOffset);
assert(Field.canBeInitialized());
const auto &Value = S.Stk.pop<T>();
Expand Down Expand Up @@ -1750,9 +1750,9 @@ bool GetPtrFieldPop(InterpState &S, CodePtr OpPC, uint32_t Off);
inline bool GetPtrThisField(InterpState &S, CodePtr OpPC, uint32_t Off) {
if (S.checkingPotentialConstantExpression() && S.Current->getDepth() == 0)
return false;
const Pointer &This = S.Current->getThis();
if (!CheckThis(S, OpPC, This))
if (!CheckThis(S, OpPC))
return false;
const Pointer &This = S.Current->getThis();
S.Stk.push<Pointer>(This.atField(Off));
return true;
}
Expand Down Expand Up @@ -1844,9 +1844,9 @@ inline bool GetMemberPtrBasePop(InterpState &S, CodePtr OpPC, int32_t Off) {
inline bool GetPtrThisBase(InterpState &S, CodePtr OpPC, uint32_t Off) {
if (S.checkingPotentialConstantExpression())
return false;
const Pointer &This = S.Current->getThis();
if (!CheckThis(S, OpPC, This))
if (!CheckThis(S, OpPC))
return false;
const Pointer &This = S.Current->getThis();
S.Stk.push<Pointer>(This.atField(Off));
return true;
}
Expand Down Expand Up @@ -1925,10 +1925,10 @@ inline bool GetPtrThisVirtBase(InterpState &S, CodePtr OpPC,
assert(D);
if (S.checkingPotentialConstantExpression())
return false;
const Pointer &This = S.Current->getThis();
if (!CheckThis(S, OpPC, This))
if (!CheckThis(S, OpPC))
return false;
return VirtBaseHelper(S, OpPC, D, S.Current->getThis());
const Pointer &This = S.Current->getThis();
return VirtBaseHelper(S, OpPC, D, This);
}

//===----------------------------------------------------------------------===//
Expand Down Expand Up @@ -1991,6 +1991,8 @@ static inline bool Activate(InterpState &S, CodePtr OpPC) {
static inline bool ActivateThisField(InterpState &S, CodePtr OpPC, uint32_t I) {
if (S.checkingPotentialConstantExpression())
return false;
if (!S.Current->hasThisPointer())
return false;

const Pointer &Ptr = S.Current->getThis();
assert(Ptr.atField(I).canBeInitialized());
Expand Down Expand Up @@ -2813,13 +2815,11 @@ inline bool IsNonNull(InterpState &S, CodePtr OpPC) {

inline bool This(InterpState &S, CodePtr OpPC) {
// Cannot read 'this' in this mode.
if (S.checkingPotentialConstantExpression()) {
if (S.checkingPotentialConstantExpression())
return false;
}

const Pointer &This = S.Current->getThis();
if (!CheckThis(S, OpPC, This))
if (!CheckThis(S, OpPC))
return false;
const Pointer &This = S.Current->getThis();

// Ensure the This pointer has been cast to the correct base.
if (!This.isDummy()) {
Expand Down
15 changes: 6 additions & 9 deletions clang/lib/AST/ByteCode/InterpFrame.cpp
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Expand Up @@ -58,15 +58,12 @@ InterpFrame::InterpFrame(InterpState &S, const Function *Func, CodePtr RetPC,
// If the fuction has a This pointer, that one is next.
// Then follow the actual arguments (but those are handled
// in getParamPointer()).
if (Func->hasRVO())
RVOPtr = stackRef<Pointer>(0);

if (Func->hasThisPointer()) {
if (Func->hasRVO())
This = stackRef<Pointer>(sizeof(Pointer));
else
This = stackRef<Pointer>(0);
if (Func->hasRVO()) {
// RVO pointer offset is always 0.
}

if (Func->hasThisPointer())
ThisPointerOffset = Func->hasRVO() ? sizeof(Pointer) : 0;
}

InterpFrame::~InterpFrame() {
Expand Down Expand Up @@ -167,7 +164,7 @@ void InterpFrame::describe(llvm::raw_ostream &OS) const {
/*Indentation=*/0);
OS << ".";
} else if (const auto *M = dyn_cast<CXXMethodDecl>(F)) {
print(OS, This, S.getASTContext(),
print(OS, getThis(), S.getASTContext(),
S.getASTContext().getLValueReferenceType(
S.getASTContext().getCanonicalTagType(M->getParent())));
OS << ".";
Expand Down
18 changes: 12 additions & 6 deletions clang/lib/AST/ByteCode/InterpFrame.h
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Expand Up @@ -104,11 +104,19 @@ class InterpFrame final : public Frame {
/// Returns a pointer to an argument - lazily creates a block.
Pointer getParamPointer(unsigned Offset);

bool hasThisPointer() const { return Func && Func->hasThisPointer(); }
/// Returns the 'this' pointer.
const Pointer &getThis() const { return This; }
const Pointer &getThis() const {
assert(hasThisPointer());
return stackRef<Pointer>(ThisPointerOffset);
}

/// Returns the RVO pointer, if the Function has one.
const Pointer &getRVOPtr() const { return RVOPtr; }
const Pointer &getRVOPtr() const {
assert(Func);
assert(Func->hasRVO());
return stackRef<Pointer>(0);
}

/// Checks if the frame is a root frame - return should quit the interpreter.
bool isRoot() const { return !Func; }
Expand Down Expand Up @@ -163,10 +171,8 @@ class InterpFrame final : public Frame {
unsigned Depth;
/// Reference to the function being executed.
const Function *Func;
/// Current object pointer for methods.
Pointer This;
/// Pointer the non-primitive return value gets constructed in.
Pointer RVOPtr;
/// Offset of the instance pointer. Use with stackRef<>().
unsigned ThisPointerOffset;
/// Return address.
CodePtr RetPC;
/// The size of all the arguments.
Expand Down