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[Clang][ItaniumMangle][NFC] Refactor FunctionTypeDepthState #196240

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eiytoq merged 1 commit into from
May 17, 2026
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[Clang][ItaniumMangle][NFC] Refactor FunctionTypeDepthState #196240

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72 changes: 29 additions & 43 deletions clang/lib/AST/ItaniumMangle.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -243,42 +243,34 @@ class CXXNameMangler {
unsigned SeqID = 0;

class FunctionTypeDepthState {
unsigned Bits = 0;

enum { InResultTypeMask = 1 };
unsigned Depth : 31;
unsigned InFunctionDeclSuffix : 1;

public:
FunctionTypeDepthState() = default;

/// The number of function types we're inside.
unsigned getDepth() const {
return Bits >> 1;
}

/// True if we're in the return type of the innermost function type.
bool isInResultType() const {
return Bits & InResultTypeMask;
FunctionTypeDepthState() : Depth(0), InFunctionDeclSuffix(0) {}

unsigned getNestingDepth(unsigned ParmDepth) const {
// ParmDepth does not include the declaring function prototype.
// FunctionTypeDepth does account for that.
assert(ParmDepth < Depth &&
"ParmVarDecl is not visible in current parameter environment");
return Depth - ParmDepth - InFunctionDeclSuffix;
}

FunctionTypeDepthState push() {
FunctionTypeDepthState tmp = *this;
Bits = (Bits & ~InResultTypeMask) + 2;
return tmp;
}

void enterResultType() {
Bits |= InResultTypeMask;
}

void leaveResultType() {
Bits &= ~InResultTypeMask;
FunctionTypeDepthState Saved = *this;
++Depth;
InFunctionDeclSuffix = 0;
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return Saved;
}

void pop(FunctionTypeDepthState saved) {
assert(getDepth() == saved.getDepth() + 1);
Bits = saved.Bits;
void pop(FunctionTypeDepthState Saved) {
assert(Depth == Saved.Depth + 1 && "unbalanced function type depth pop");
*this = Saved;
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}

void enterFunctionDeclSuffix() { InFunctionDeclSuffix = 1; }
void leaveFunctionDeclSuffix() { InFunctionDeclSuffix = 0; }
Comment on lines +272 to +273

@AaronBallman AaronBallman May 18, 2026

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Should we guard against mismatched calls? e.g., assert that we cannot leave if we've not entered, and assert that we cannot enter if we're already entered?

@eiytoq eiytoq May 18, 2026

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I think this makes sense. Because every time FunctionTypeDepth.push() is called, InFunctionDeclSuffix is reset, and at the same depth, enterFunctionDeclSuffix should not be entered repeatedly. However, I'm not entirely sure if I've missed any details.

} FunctionTypeDepth;

// abi_tag is a gcc attribute, taking one or more strings called "tags".
Expand Down Expand Up @@ -3752,9 +3744,9 @@ void CXXNameMangler::mangleType(const FunctionNoProtoType *T) {

FunctionTypeDepthState saved = FunctionTypeDepth.push();

FunctionTypeDepth.enterResultType();
FunctionTypeDepth.enterFunctionDeclSuffix();
mangleType(T->getReturnType());
FunctionTypeDepth.leaveResultType();
FunctionTypeDepth.leaveFunctionDeclSuffix();

FunctionTypeDepth.pop(saved);
Out << 'E';
Expand All @@ -3769,7 +3761,7 @@ void CXXNameMangler::mangleBareFunctionType(const FunctionProtoType *Proto,

// <bare-function-type> ::= <signature type>+
if (MangleReturnType) {
FunctionTypeDepth.enterResultType();
FunctionTypeDepth.enterFunctionDeclSuffix();

// Mangle ns_returns_retained as an order-sensitive qualifier here.
if (Proto->getExtInfo().getProducesResult() && FD == nullptr)
Expand All @@ -3784,7 +3776,7 @@ void CXXNameMangler::mangleBareFunctionType(const FunctionProtoType *Proto,
}
mangleType(ReturnTy);

FunctionTypeDepth.leaveResultType();
FunctionTypeDepth.leaveFunctionDeclSuffix();

@AaronBallman AaronBallman May 18, 2026

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Would it make sense to add an RAII object to do the enter/leave calls? I worry about the possibility of adding a return in here someday that breaks this.

@eiytoq eiytoq May 18, 2026

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We could introduce an RAII object (because the missing leave below is actually omitted), but that might require guarding every call site.

}

if (Proto->getNumParams() == 0 && !Proto->isVariadic()) {
Expand Down Expand Up @@ -3821,7 +3813,7 @@ void CXXNameMangler::mangleBareFunctionType(const FunctionProtoType *Proto,
}

if (FD) {
FunctionTypeDepth.enterResultType();
FunctionTypeDepth.enterFunctionDeclSuffix();

@AaronBallman AaronBallman May 18, 2026

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Ohhh, RAII object might not make sense, what ends up leaving this?

@eiytoq eiytoq May 18, 2026

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The state will be restored by the following FunctionTypeDepth.pop(saved), so leaveFunctionDeclSuffix can be omitted here.

mangleRequiresClause(FD->getTrailingRequiresClause().ConstraintExpr);
}

Expand Down Expand Up @@ -5716,7 +5708,7 @@ void CXXNameMangler::mangleExpression(const Expr *E, unsigned Arity,
Out << '_';

// The rest of the mangling is in the immediate scope of the parameters.
FunctionTypeDepth.enterResultType();
FunctionTypeDepth.enterFunctionDeclSuffix();

@AaronBallman AaronBallman May 18, 2026

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What ends up leaving this?

@eiytoq eiytoq May 18, 2026

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Same as above.

for (const concepts::Requirement *Req : RE->getRequirements())
mangleRequirement(RE->getExprLoc(), Req);
FunctionTypeDepth.pop(saved);
Expand Down Expand Up @@ -6013,14 +6005,8 @@ void CXXNameMangler::mangleFunctionParam(const ParmVarDecl *parm) {
unsigned parmIndex = parm->getFunctionScopeIndex();

// Compute 'L'.
// parmDepth does not include the declaring function prototype.
// FunctionTypeDepth does account for that.
assert(parmDepth < FunctionTypeDepth.getDepth());
unsigned nestingDepth = FunctionTypeDepth.getDepth() - parmDepth;
if (FunctionTypeDepth.isInResultType())
nestingDepth--;

if (nestingDepth == 0) {
if (unsigned nestingDepth = FunctionTypeDepth.getNestingDepth(parmDepth);
nestingDepth == 0) {
Out << "fp";
} else {
Out << "fL" << (nestingDepth - 1) << 'p';
Expand Down Expand Up @@ -7254,9 +7240,9 @@ CXXNameMangler::makeFunctionReturnTypeTags(const FunctionDecl *FD) {
const FunctionProtoType *Proto =
cast<FunctionProtoType>(FD->getType()->getAs<FunctionType>());
FunctionTypeDepthState saved = TrackReturnTypeTags.FunctionTypeDepth.push();
TrackReturnTypeTags.FunctionTypeDepth.enterResultType();
TrackReturnTypeTags.FunctionTypeDepth.enterFunctionDeclSuffix();
TrackReturnTypeTags.mangleType(Proto->getReturnType());
TrackReturnTypeTags.FunctionTypeDepth.leaveResultType();
TrackReturnTypeTags.FunctionTypeDepth.leaveFunctionDeclSuffix();
TrackReturnTypeTags.FunctionTypeDepth.pop(saved);

return TrackReturnTypeTags.AbiTagsRoot.getSortedUniqueUsedAbiTags();
Expand Down