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[Clang] Mangling of pack indexing type and expression for itanium #123513

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ca55a3f
[Clang] Mangling of pack indexing type and expression for itanium
cor3ntin Jan 19, 2025
f17310f
Fix test file
cor3ntin Jan 27, 2025
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1 change: 1 addition & 0 deletions clang/docs/ReleaseNotes.rst
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Expand Up @@ -1003,6 +1003,7 @@ Bug Fixes to C++ Support
lambda functions or inline friend functions defined inside templates (#GH122493).
- Clang now rejects declaring an alias template with the same name as its template parameter. (#GH123423)
- Correctly determine the implicit constexprness of lambdas in dependent contexts. (#GH97958) (#GH114234)
- Implement Itanium mangling for pack indexing. (#GH112003)
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I think it should live in C++2c support section, as this isn't strictly a bug.


Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
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35 changes: 19 additions & 16 deletions clang/lib/AST/ItaniumMangle.cpp
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Expand Up @@ -603,6 +603,7 @@ class CXXNameMangler {
void mangleInitListElements(const InitListExpr *InitList);
void mangleRequirement(SourceLocation RequiresExprLoc,
const concepts::Requirement *Req);
void mangleReferenceToPack(const NamedDecl *ND);
void mangleExpression(const Expr *E, unsigned Arity = UnknownArity,
bool AsTemplateArg = false);
void mangleCXXCtorType(CXXCtorType T, const CXXRecordDecl *InheritedFrom);
Expand Down Expand Up @@ -4348,10 +4349,10 @@ void CXXNameMangler::mangleType(const PackExpansionType *T) {
}

void CXXNameMangler::mangleType(const PackIndexingType *T) {
if (!T->hasSelectedType())
mangleType(T->getPattern());
else
mangleType(T->getSelectedType());
// <type> ::= Dy <type> <expression> # pack indexing type (C++23)
Out << "Dy";
mangleType(T->getPattern());
mangleExpression(T->getIndexExpr());
}

void CXXNameMangler::mangleType(const ObjCInterfaceType *T) {
Expand Down Expand Up @@ -4787,6 +4788,7 @@ void CXXNameMangler::mangleRequirement(SourceLocation RequiresExprLoc,

void CXXNameMangler::mangleExpression(const Expr *E, unsigned Arity,
bool AsTemplateArg) {
// clang-format off
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nit: Why turning it off?

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clang-format initially completely destroy the comment below, which has been neatly aligned

// <expression> ::= <unary operator-name> <expression>
// ::= <binary operator-name> <expression> <expression>
// ::= <trinary operator-name> <expression> <expression> <expression>
Expand All @@ -4806,6 +4808,8 @@ void CXXNameMangler::mangleExpression(const Expr *E, unsigned Arity,
// ::= ds <expression> <expression> # expr.*expr
// ::= sZ <template-param> # size of a parameter pack
// ::= sZ <function-param> # size of a function parameter pack
// ::= sy <template-param> <expression> # pack indexing expression
// ::= sy <function-param> <expression> # pack indexing expression
// ::= u <source-name> <template-arg>* E # vendor extended expression
// ::= <expr-primary>
// <expr-primary> ::= L <type> <value number> E # integer literal
Expand All @@ -4815,6 +4819,7 @@ void CXXNameMangler::mangleExpression(const Expr *E, unsigned Arity,
// ::= L <pointer type> 0 E # null pointer template argument
// ::= L <type> <real-part float> _ <imag-part float> E # complex floating point literal (C99); not used by clang
// ::= L <mangled-name> E # external name
// clang-format on
QualType ImplicitlyConvertedToType;

// A top-level expression that's not <expr-primary> needs to be wrapped in
Expand Down Expand Up @@ -4886,7 +4891,6 @@ void CXXNameMangler::mangleExpression(const Expr *E, unsigned Arity,
case Expr::OMPIteratorExprClass:
case Expr::CXXInheritedCtorInitExprClass:
case Expr::CXXParenListInitExprClass:
case Expr::PackIndexingExprClass:
llvm_unreachable("unexpected statement kind");

case Expr::ConstantExprClass:
Expand Down Expand Up @@ -5788,17 +5792,7 @@ void CXXNameMangler::mangleExpression(const Expr *E, unsigned Arity,
}

Out << "sZ";
const NamedDecl *Pack = SPE->getPack();
if (const TemplateTypeParmDecl *TTP = dyn_cast<TemplateTypeParmDecl>(Pack))
mangleTemplateParameter(TTP->getDepth(), TTP->getIndex());
else if (const NonTypeTemplateParmDecl *NTTP
= dyn_cast<NonTypeTemplateParmDecl>(Pack))
mangleTemplateParameter(NTTP->getDepth(), NTTP->getIndex());
else if (const TemplateTemplateParmDecl *TempTP
= dyn_cast<TemplateTemplateParmDecl>(Pack))
mangleTemplateParameter(TempTP->getDepth(), TempTP->getIndex());
else
mangleFunctionParam(cast<ParmVarDecl>(Pack));
mangleReferenceToPack(SPE->getPack());
break;
}

Expand Down Expand Up @@ -5828,6 +5822,15 @@ void CXXNameMangler::mangleExpression(const Expr *E, unsigned Arity,
break;
}

case Expr::PackIndexingExprClass: {
auto *PE = cast<PackIndexingExpr>(E);
NotPrimaryExpr();
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I am looking at the test cases and I don't see the X, can we make sure we cover that branch in NotPrimaryExpr e.g. if (AsTemplateArg && IsPrimaryExpr). We should make sure we cover that in the demangling as well.

Out << "sy";
mangleReferenceToPack(PE->getPackDecl());
mangleExpression(PE->getIndexExpr());
break;
}

case Expr::CXXThisExprClass:
NotPrimaryExpr();
Out << "fpT";
Expand Down
34 changes: 34 additions & 0 deletions clang/test/CodeGenCXX/mangle-cxx2c.cpp
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@@ -0,0 +1,34 @@
// RUN: %clang_cc1 -emit-llvm %s -o - -triple=x86_64-linux-gnu -std=c++2c | FileCheck %s

namespace GH112003 {

// CHECK-LABEL: define {{.*}} @_ZN8GH1120033fooILi0ETpTnDaJLi0ELi0EEEEDTsyT0_T_Ev
// CHECK-LABEL: define {{.*}} @_ZN8GH1120033fooILi1ETpTnDaJLi0ELi0EEEEDTsyT0_T_Ev
// CHECK-LABEL: define {{.*}} @_ZN8GH1120033fooILi0ETpTnDaJLl1EEEEDTsyT0_T_Ev
template <int I, auto...V>
decltype(V...[I]) foo() {return {};}

// CHECK-LABEL: define {{.*}} @_ZN8GH1120033barILi0EJilEEEDyT0_T_v
// CHECK-LABEL: define {{.*}} @_ZN8GH1120033barILi1EJilEEEDyT0_T_v
template <int I, typename...V>
V...[I] bar() {return {};}


template <int I, typename... T>
using First = T...[0];

// CHECK-LABEL: define {{.*}} @_ZN8GH1120033bazILi0EJiEEEvDy_SUBSTPACK_Li0E
// FIXME: handle indexing of partially substituted packs
template <int I, typename...V>
void baz(First<I, int, V...>){};


void fn() {
foo<0, 0, 0>();
foo<1, 0, 0>();
foo<0, 1L>();
bar<0, int, long>();
bar<1, int, long>();
baz<0, int>(0);
}
}
43 changes: 43 additions & 0 deletions libcxxabi/src/demangle/ItaniumDemangle.h
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Expand Up @@ -1521,6 +1521,27 @@ class ParameterPackExpansion final : public Node {
}
};

class PackIndexing final : public Node {
const Node *Pattern;
const Node *Index;

public:
PackIndexing(const Node *Pattern_, const Node *Index_)
: Node(KPackIndexing), Pattern(Pattern_), Index(Index_) {}

template <typename Fn> void match(Fn F) const { F(Pattern, Index); }

void printLeft(OutputBuffer &OB) const override {
OB.printOpen('(');
ParameterPackExpansion PPE(Pattern);
PPE.printLeft(OB);
OB.printClose(')');
OB.printOpen('[');
Index->printLeft(OB);
OB.printClose(']');
}
};

class TemplateArgs final : public Node {
NodeArray Params;
Node *Requires;
Expand Down Expand Up @@ -4510,6 +4531,18 @@ Node *AbstractManglingParser<Derived, Alloc>::parseType() {
Result = make<ParameterPackExpansion>(Child);
break;
}
// ::= Dy <type> <expression> # pack indexing (C++26)
case 'y': {
First += 2;
Node *Pattern = getDerived().parseType();
if (!Pattern)
return nullptr;
Node *Index = getDerived().parseExpr();
if (!Index)
return nullptr;
Result = make<PackIndexing>(Pattern, Index);
break;
}
// Exception specifier on a function type.
case 'o':
case 'O':
Expand Down Expand Up @@ -5354,6 +5387,16 @@ Node *AbstractManglingParser<Derived, Alloc>::parseExpr() {
return nullptr;
return make<ParameterPackExpansion>(Child);
}
if (consumeIf("sy")) {
Node *Pattern = look() == 'T' ? getDerived().parseTemplateParam()
: getDerived().parseFunctionParam();
if (Pattern == nullptr)
return nullptr;
Node *Index = getDerived().parseExpr();
if (Index == nullptr)
return nullptr;
return make<PackIndexing>(Pattern, Index);
}
if (consumeIf("sZ")) {
if (look() == 'T') {
Node *R = getDerived().parseTemplateParam();
Expand Down
2 changes: 1 addition & 1 deletion libcxxabi/src/demangle/ItaniumNodes.def
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Expand Up @@ -100,5 +100,5 @@ NODE(ExprRequirement)
NODE(TypeRequirement)
NODE(NestedRequirement)
NODE(ExplicitObjectParameter)

NODE(PackIndexing)
#undef NODE
5 changes: 5 additions & 0 deletions libcxxabi/test/test_demangle.pass.cpp
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Expand Up @@ -30220,6 +30220,11 @@ const char* cases[][2] = {
{"_ZZNH3Foo3fooES_iENK4Foo24foo2Ev", "Foo::foo(this Foo, int)::Foo2::foo2() const" },
{"_ZNH3FooclERKS_", "Foo::operator()(this Foo const&)"},


// C++26 pack indexing
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We should add invalid cases as well see invalid_cases and make sure we cover each case that can return a nullptr in AbstractManglingParser (I think)

{"_Z3fooILi0ETpTnDaJLi1ELi2EEEDTsyT0_T_Ev", "decltype((1, 2...)[0]) foo<0, 1, 2>()"},
{"_Z1gILi0EJciEEDyT0_T_v", "(char, int)[0] g<0, char, int>()"},

// fixed-point types as defined in the N1169 draft of ISO/IEC DTR 18037
{"_Z1fDAs", "f(short _Accum)"},
{"_Z1fDAt", "f(unsigned short _Accum)"},
Expand Down
43 changes: 43 additions & 0 deletions llvm/include/llvm/Demangle/ItaniumDemangle.h
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Expand Up @@ -1521,6 +1521,27 @@ class ParameterPackExpansion final : public Node {
}
};

class PackIndexing final : public Node {
const Node *Pattern;
const Node *Index;

public:
PackIndexing(const Node *Pattern_, const Node *Index_)
: Node(KPackIndexing), Pattern(Pattern_), Index(Index_) {}

template <typename Fn> void match(Fn F) const { F(Pattern, Index); }

void printLeft(OutputBuffer &OB) const override {
OB.printOpen('(');
ParameterPackExpansion PPE(Pattern);
PPE.printLeft(OB);
OB.printClose(')');
OB.printOpen('[');
Index->printLeft(OB);
OB.printClose(']');
}
};

class TemplateArgs final : public Node {
NodeArray Params;
Node *Requires;
Expand Down Expand Up @@ -4510,6 +4531,18 @@ Node *AbstractManglingParser<Derived, Alloc>::parseType() {
Result = make<ParameterPackExpansion>(Child);
break;
}
// ::= Dy <type> <expression> # pack indexing (C++26)
case 'y': {
First += 2;
Node *Pattern = getDerived().parseType();
if (!Pattern)
return nullptr;
Node *Index = getDerived().parseExpr();
if (!Index)
return nullptr;
Result = make<PackIndexing>(Pattern, Index);
break;
}
// Exception specifier on a function type.
case 'o':
case 'O':
Expand Down Expand Up @@ -5354,6 +5387,16 @@ Node *AbstractManglingParser<Derived, Alloc>::parseExpr() {
return nullptr;
return make<ParameterPackExpansion>(Child);
}
if (consumeIf("sy")) {
Node *Pattern = look() == 'T' ? getDerived().parseTemplateParam()
: getDerived().parseFunctionParam();
if (Pattern == nullptr)
return nullptr;
Node *Index = getDerived().parseExpr();
if (Index == nullptr)
return nullptr;
return make<PackIndexing>(Pattern, Index);
}
if (consumeIf("sZ")) {
if (look() == 'T') {
Node *R = getDerived().parseTemplateParam();
Expand Down
2 changes: 1 addition & 1 deletion llvm/include/llvm/Demangle/ItaniumNodes.def
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Expand Up @@ -100,5 +100,5 @@ NODE(ExprRequirement)
NODE(TypeRequirement)
NODE(NestedRequirement)
NODE(ExplicitObjectParameter)

NODE(PackIndexing)
#undef NODE
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