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[clang][ASTImporter] Improve structural equivalence of overloadable operators. #72242

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Jan 18, 2024
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[clang][ASTImporter] Improve structural equivalence of overloadable operators. #72242

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[clang][ASTImporter] Improve structural equivalence of overloadable o…
balazske Nov 14, 2023
0c34b2d
updated code comment
balazske Nov 27, 2023
d2b47ae
changed wrong-looking test code
balazske Jan 12, 2024
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57 changes: 57 additions & 0 deletions clang/lib/AST/ASTStructuralEquivalence.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -98,6 +98,8 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
QualType T1, QualType T2);
static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
Decl *D1, Decl *D2);
static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
const Stmt *S1, const Stmt *S2);
static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
const TemplateArgument &Arg1,
const TemplateArgument &Arg2);
Expand Down Expand Up @@ -437,12 +439,67 @@ class StmtComparer {
};
} // namespace

static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
const UnaryOperator *E1,
const CXXOperatorCallExpr *E2) {
return UnaryOperator::getOverloadedOperator(E1->getOpcode()) ==
E2->getOperator() &&
IsStructurallyEquivalent(Context, E1->getSubExpr(), E2->getArg(0));
}

static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
const CXXOperatorCallExpr *E1,
const UnaryOperator *E2) {
return E1->getOperator() ==
UnaryOperator::getOverloadedOperator(E2->getOpcode()) &&
IsStructurallyEquivalent(Context, E1->getArg(0), E2->getSubExpr());
}

static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
const BinaryOperator *E1,
const CXXOperatorCallExpr *E2) {
return BinaryOperator::getOverloadedOperator(E1->getOpcode()) ==
E2->getOperator() &&
IsStructurallyEquivalent(Context, E1->getLHS(), E2->getArg(0)) &&
IsStructurallyEquivalent(Context, E1->getRHS(), E2->getArg(1));
}

static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
const CXXOperatorCallExpr *E1,
const BinaryOperator *E2) {
return E1->getOperator() ==
BinaryOperator::getOverloadedOperator(E2->getOpcode()) &&
IsStructurallyEquivalent(Context, E1->getArg(0), E2->getLHS()) &&
IsStructurallyEquivalent(Context, E1->getArg(1), E2->getRHS());
}

/// Determine structural equivalence of two statements.
static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
const Stmt *S1, const Stmt *S2) {
if (!S1 || !S2)
return S1 == S2;

// Check for statements with similar syntax but different AST.
// The unary and binary operators (like '+', '&') can be parsed as
// CXXOperatorCall too (and UnaryOperator or BinaryOperator).
// This depends on arguments with unresolved type and on the name lookup.
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Could you perhaps elaborate this sentence a bit? Do I understand it correctly that e.g. in CXXOperatorCallExprVsUnaryBinaryOperator the presence of struct Bar in the second TU ensured that all the operators are parsed as CXXOperatorCalls, while in the first TU they are parsed as unary/binary operator expressions?

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@balazske balazske Nov 24, 2023 •
edited
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The idea was coming from this post:
https://discourse.llvm.org/t/different-ast-translations-for-the-same-body-why/22741
The presence of an operator declaration is needed to change the parsed AST from BinaryOperator to CXXOverloadedOperatorCallExpr.

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Thanks for the link, it's really helpful. Perhaps it should be included in the source code comment as well, to help those who'll work on this code in the future.

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Thanks, the updated comment is clear now.

// The lookup results can be different in a "From" and "To" AST even if the
// compared structure is otherwise equivalent. For this reason we must treat
// these operators as equivalent even if they are represented by different AST
// nodes.
if (const auto *E2CXXOperatorCall = dyn_cast<CXXOperatorCallExpr>(S2)) {
if (const auto *E1Unary = dyn_cast<UnaryOperator>(S1))
return IsStructurallyEquivalent(Context, E1Unary, E2CXXOperatorCall);
if (const auto *E1Binary = dyn_cast<BinaryOperator>(S1))
return IsStructurallyEquivalent(Context, E1Binary, E2CXXOperatorCall);
}
if (const auto *E1CXXOperatorCall = dyn_cast<CXXOperatorCallExpr>(S1)) {
if (const auto *E2Unary = dyn_cast<UnaryOperator>(S2))
return IsStructurallyEquivalent(Context, E1CXXOperatorCall, E2Unary);
if (const auto *E2Binary = dyn_cast<BinaryOperator>(S2))
return IsStructurallyEquivalent(Context, E1CXXOperatorCall, E2Binary);
}

// Compare the statements itself.
StmtComparer Comparer(Context);
if (!Comparer.IsEquivalent(S1, S2))
Expand Down
170 changes: 170 additions & 0 deletions clang/unittests/AST/StructuralEquivalenceTest.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2252,6 +2252,176 @@ TEST_F(StructuralEquivalenceStmtTest, UnaryOperatorDifferentOps) {
EXPECT_FALSE(testStructuralMatch(t));
}

TEST_F(StructuralEquivalenceStmtTest,
CXXOperatorCallExprVsUnaryBinaryOperator) {
auto t = makeNamedDecls(
R"(
template <typename T, T x>
class A;
template <typename T, T x, T y>
void foo(
A<T, x + y>,
A<T, x - y>,
A<T, -x>,
A<T, x * y>,
A<T, *x>,
A<T, x / y>,
A<T, x % y>,
A<T, x ^ y>,
A<T, x & y>,
A<T, &x>,
A<T, x | y>,
A<T, ~x>,
A<T, !x>,
A<T, x < y>,
A<T, (x > y)>,
A<T, x << y>,
A<T, (x >> y)>,
A<T, x == y>,
A<T, x != y>,
A<T, x <= y>,
A<T, x >= y>,
A<T, x <=> y>,
A<T, x && y>,
A<T, x || y>,
A<T, ++x>,
A<T, --x>,
A<T, (x , y)>,
A<T, x ->* y>,
A<T, x -> y>
);
)",
R"(
struct Bar {
Bar& operator=(Bar&);
Bar& operator->();
};

Bar& operator+(Bar&, Bar&);
Bar& operator+(Bar&);
Bar& operator-(Bar&, Bar&);
Bar& operator-(Bar&);
Bar& operator*(Bar&, Bar&);
Bar& operator*(Bar&);
Bar& operator/(Bar&, Bar&);
Bar& operator%(Bar&, Bar&);
Bar& operator^(Bar&, Bar&);
Bar& operator&(Bar&, Bar&);
Bar& operator&(Bar&);
Bar& operator|(Bar&, Bar&);
Bar& operator~(Bar&);
Bar& operator!(Bar&);
Bar& operator<(Bar&, Bar&);
Bar& operator>(Bar&, Bar&);
Bar& operator+=(Bar&, Bar&);
Bar& operator-=(Bar&, Bar&);
Bar& operator*=(Bar&, Bar&);
Bar& operator/=(Bar&, Bar&);
Bar& operator%=(Bar&, Bar&);
Bar& operator^=(Bar&, Bar&);
Bar& operator&=(Bar&, Bar&);
Bar& operator|=(Bar&, Bar&);
Bar& operator<<(Bar&, Bar&);
Bar& operator>>(Bar&, Bar&);
Bar& operator<<=(Bar&, Bar&);
Bar& operator>>=(Bar&, Bar&);
Bar& operator==(Bar&, Bar&);
Bar& operator!=(Bar&, Bar&);
Bar& operator<=(Bar&, Bar&);
Bar& operator>=(Bar&, Bar&);
Bar& operator<=>(Bar&, Bar&);
Bar& operator&&(Bar&, Bar&);
Bar& operator||(Bar&, Bar&);
Bar& operator++(Bar&);
Bar& operator--(Bar&);
Bar& operator,(Bar&, Bar&);
Bar& operator->*(Bar&, Bar&);

template <typename T, T x>
class A;
template <typename T, T x, T y>
void foo(
A<T, x + y>,
A<T, x - y>,
A<T, -x>,
A<T, x * y>,
A<T, *x>,
A<T, x / y>,
A<T, x % y>,
A<T, x ^ y>,
A<T, x & y>,
A<T, &x>,
A<T, x | y>,
A<T, ~x>,
A<T, !x>,
A<T, x < y>,
A<T, (x > y)>,
A<T, x << y>,
A<T, (x >> y)>,
A<T, x == y>,
A<T, x != y>,
A<T, x <= y>,
A<T, x >= y>,
A<T, x <=> y>,
A<T, x && y>,
A<T, x || y>,
A<T, ++x>,
A<T, --x>,
A<T, (x , y)>,
A<T, x ->* y>,
A<T, x -> y>
);
)",
Lang_CXX20);
EXPECT_TRUE(testStructuralMatch(t));
}

TEST_F(StructuralEquivalenceStmtTest,
CXXOperatorCallExprVsUnaryBinaryOperatorNe) {
auto t = makeNamedDecls(
R"(
template <typename T, T x>
class A;
template <typename T, T x, T y>
void foo(
A<T, x + y>
);
)",
R"(
struct Bar;

Bar& operator+(Bar&, Bar&);
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Why is the presence of this operator+ relevant if this TU doesn't use operator+ at all?

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I do not know exactly what was the purpose, but likely it should be operator - instead.

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Code is now updated to operator- (the first code should contain an CXXOperatorCallExpr, the second a BinaryOperator in the template arg 2 of A).


template <typename T, T x>
class A;
template <typename T, T x, T y>
void foo(
A<T, x - y>
);
)",
Lang_CXX11);
EXPECT_FALSE(testStructuralMatch(t));
}

TEST_F(StructuralEquivalenceStmtTest, NonTypeTemplateParm) {
auto t = makeNamedDecls(
R"(
template <typename T, T x>
class A;
template <typename T, T x, T y>
void foo(A<T, x>);
)",
R"(
template <typename T, T x>
class A;
template <typename T, T x, T y>
void foo(A<T, y>);
)",
Lang_CXX11);
// FIXME: These should not match,
EXPECT_TRUE(testStructuralMatch(t));
}

TEST_F(StructuralEquivalenceStmtTest, UnresolvedLookupDifferentName) {
auto t = makeStmts(
R"(
Expand Down