[Clang][C++26] Implement "Ordering of constraints involving fold expressions #98160
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@llvm/pr-subscribers-clang Author: cor3ntin (cor3ntin) ChangesImplement https://isocpp.org/files/papers/P2963R3.pdf Patch is 50.57 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/98160.diff 7 Files Affected:
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 838cb69f647ee..7d0b2115f8e53 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -271,6 +271,9 @@ C++2c Feature Support
- Implemented `P3144R2 Deleting a Pointer to an Incomplete Type Should be Ill-formed <https://wg21.link/P3144R2>`_.
+- Implemented `P2963R3 Ordering of constraints involving fold expressions <https://wg21.link/P2963R3>`_.
+
+
Resolutions to C++ Defect Reports
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- Substitute template parameter pack, when it is not explicitly specified
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 75a80540dbcbf..4a07da6b7bfd9 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -14062,6 +14062,11 @@ class Sema final : public SemaBase {
const DeclarationNameInfo &NameInfo,
SmallVectorImpl<UnexpandedParameterPack> &Unexpanded);
+ /// Collect the set of unexpanded parameter packs within the given
+ /// expression.
+ static void collectUnexpandedParameterPacks(
+ Expr *E, SmallVectorImpl<UnexpandedParameterPack> &Unexpanded);
+
/// Invoked when parsing a template argument followed by an
/// ellipsis, which creates a pack expansion.
///
diff --git a/clang/include/clang/Sema/SemaConcept.h b/clang/include/clang/Sema/SemaConcept.h
index 711443505174f..b6327e729768b 100644
--- a/clang/include/clang/Sema/SemaConcept.h
+++ b/clang/include/clang/Sema/SemaConcept.h
@@ -75,6 +75,17 @@ struct AtomicConstraint {
}
};
+struct FoldExpandedConstraint;
+
+using NormalFormConstraint =
+ llvm::PointerUnion<AtomicConstraint *, FoldExpandedConstraint *>;
+struct NormalizedConstraint;
+using NormalForm =
+ llvm::SmallVector<llvm::SmallVector<NormalFormConstraint, 2>, 4>;
+
+NormalForm makeCNF(const NormalizedConstraint &Normalized);
+NormalForm makeDNF(const NormalizedConstraint &Normalized);
+
/// \brief A normalized constraint, as defined in C++ [temp.constr.normal], is
/// either an atomic constraint, a conjunction of normalized constraints or a
/// disjunction of normalized constraints.
@@ -87,26 +98,17 @@ struct NormalizedConstraint {
std::pair<NormalizedConstraint, NormalizedConstraint> *, 1,
CompoundConstraintKind>;
- llvm::PointerUnion<AtomicConstraint *, CompoundConstraint> Constraint;
+ llvm::PointerUnion<AtomicConstraint *, FoldExpandedConstraint *,
+ CompoundConstraint>
+ Constraint;
NormalizedConstraint(AtomicConstraint *C): Constraint{C} { };
+ NormalizedConstraint(FoldExpandedConstraint *C) : Constraint{C} {};
+
NormalizedConstraint(ASTContext &C, NormalizedConstraint LHS,
- NormalizedConstraint RHS, CompoundConstraintKind Kind)
- : Constraint{CompoundConstraint{
- new (C) std::pair<NormalizedConstraint, NormalizedConstraint>{
- std::move(LHS), std::move(RHS)}, Kind}} { };
-
- NormalizedConstraint(ASTContext &C, const NormalizedConstraint &Other) {
- if (Other.isAtomic()) {
- Constraint = new (C) AtomicConstraint(*Other.getAtomicConstraint());
- } else {
- Constraint = CompoundConstraint(
- new (C) std::pair<NormalizedConstraint, NormalizedConstraint>{
- NormalizedConstraint(C, Other.getLHS()),
- NormalizedConstraint(C, Other.getRHS())},
- Other.getCompoundKind());
- }
- }
+ NormalizedConstraint RHS, CompoundConstraintKind Kind);
+
+ NormalizedConstraint(ASTContext &C, const NormalizedConstraint &Other);
NormalizedConstraint(NormalizedConstraint &&Other):
Constraint(Other.Constraint) {
Other.Constraint = nullptr;
@@ -126,6 +128,9 @@ struct NormalizedConstraint {
}
bool isAtomic() const { return Constraint.is<AtomicConstraint *>(); }
+ bool isFoldExpanded() const {
+ return Constraint.is<FoldExpandedConstraint *>();
+ }
NormalizedConstraint &getLHS() const {
assert(!isAtomic() && "getLHS called on atomic constraint.");
@@ -143,6 +148,12 @@ struct NormalizedConstraint {
return Constraint.get<AtomicConstraint *>();
}
+ FoldExpandedConstraint *getFoldExpandedConstraint() const {
+ assert(isFoldExpanded() &&
+ "getFoldExpandedConstraint called on non-fold-expanded constraint.");
+ return Constraint.get<FoldExpandedConstraint *>();
+ }
+
private:
static std::optional<NormalizedConstraint>
fromConstraintExprs(Sema &S, NamedDecl *D, ArrayRef<const Expr *> E);
@@ -150,6 +161,103 @@ struct NormalizedConstraint {
fromConstraintExpr(Sema &S, NamedDecl *D, const Expr *E);
};
+struct FoldExpandedConstraint {
+ enum class FoldOperatorKind { FoAnd, FoOr } Kind;
+ NormalizedConstraint Constraint;
+ const Expr *Pattern;
+
+ FoldExpandedConstraint(FoldOperatorKind K, NormalizedConstraint C,
+ const Expr *Pattern)
+ : Kind(K), Constraint(std::move(C)), Pattern(Pattern) {};
+
+ template <typename AtomicSubsumptionEvaluator>
+ bool subsumes(const FoldExpandedConstraint &Other,
+ AtomicSubsumptionEvaluator E) const;
+
+ static bool AreSubsumptionElligible(const FoldExpandedConstraint &A,
+ const FoldExpandedConstraint &B);
+};
+
+const NormalizedConstraint *getNormalizedAssociatedConstraints(
+ Sema &S, NamedDecl *ConstrainedDecl,
+ ArrayRef<const Expr *> AssociatedConstraints);
+
+template <typename AtomicSubsumptionEvaluator>
+bool subsumes(const NormalForm &PDNF, const NormalForm &QCNF,
+ AtomicSubsumptionEvaluator E) {
+ // C++ [temp.constr.order] p2
+ // Then, P subsumes Q if and only if, for every disjunctive clause Pi in the
+ // disjunctive normal form of P, Pi subsumes every conjunctive clause Qj in
+ // the conjuctive normal form of Q, where [...]
+ for (const auto &Pi : PDNF) {
+ for (const auto &Qj : QCNF) {
+ // C++ [temp.constr.order] p2
+ // - [...] a disjunctive clause Pi subsumes a conjunctive clause Qj if
+ // and only if there exists an atomic constraint Pia in Pi for which
+ // there exists an atomic constraint, Qjb, in Qj such that Pia
+ // subsumes Qjb.
+ bool Found = false;
+ for (NormalFormConstraint Pia : Pi) {
+ for (NormalFormConstraint Qjb : Qj) {
+ if (Pia.is<FoldExpandedConstraint *>() &&
+ Qjb.is<FoldExpandedConstraint *>()) {
+ if (Pia.get<FoldExpandedConstraint *>()->subsumes(
+ *Qjb.get<FoldExpandedConstraint *>(), E)) {
+ Found = true;
+ break;
+ }
+ } else if (Pia.is<AtomicConstraint *>() &&
+ Qjb.is<AtomicConstraint *>()) {
+ if (E(*Pia.get<AtomicConstraint *>(),
+ *Qjb.get<AtomicConstraint *>())) {
+ Found = true;
+ break;
+ }
+ }
+ }
+ if (Found)
+ break;
+ }
+ if (!Found)
+ return false;
+ }
+ }
+ return true;
+}
+
+template <typename AtomicSubsumptionEvaluator>
+bool subsumes(Sema &S, NamedDecl *DP, ArrayRef<const Expr *> P, NamedDecl *DQ,
+ ArrayRef<const Expr *> Q, bool &Subsumes,
+ AtomicSubsumptionEvaluator E) {
+ // C++ [temp.constr.order] p2
+ // In order to determine if a constraint P subsumes a constraint Q, P is
+ // transformed into disjunctive normal form, and Q is transformed into
+ // conjunctive normal form. [...]
+ auto *PNormalized = getNormalizedAssociatedConstraints(S, DP, P);
+ if (!PNormalized)
+ return true;
+ const NormalForm PDNF = makeDNF(*PNormalized);
+
+ auto *QNormalized = getNormalizedAssociatedConstraints(S, DQ, Q);
+ if (!QNormalized)
+ return true;
+ const NormalForm QCNF = makeCNF(*QNormalized);
+
+ Subsumes = subsumes(PDNF, QCNF, E);
+ return false;
+}
+
+template <typename AtomicSubsumptionEvaluator>
+bool FoldExpandedConstraint::subsumes(const FoldExpandedConstraint &Other,
+ AtomicSubsumptionEvaluator E) const {
+ if (Kind != Other.Kind || !AreSubsumptionElligible(*this, Other))
+ return false;
+
+ const NormalForm PDNF = makeDNF(this->Constraint);
+ const NormalForm QCNF = makeCNF(Other.Constraint);
+ return clang::subsumes(PDNF, QCNF, E);
+}
+
} // clang
#endif // LLVM_CLANG_SEMA_SEMACONCEPT_H
diff --git a/clang/lib/Sema/SemaConcept.cpp b/clang/lib/Sema/SemaConcept.cpp
index 202dd86c67f62..b86e2d51e380b 100644
--- a/clang/lib/Sema/SemaConcept.cpp
+++ b/clang/lib/Sema/SemaConcept.cpp
@@ -65,6 +65,7 @@ class LogicalBinOp {
const Expr *getLHS() const { return LHS; }
const Expr *getRHS() const { return RHS; }
+ OverloadedOperatorKind getOp() const { return Op; }
ExprResult recreateBinOp(Sema &SemaRef, ExprResult LHS) const {
return recreateBinOp(SemaRef, LHS, const_cast<Expr *>(getRHS()));
@@ -177,65 +178,160 @@ struct SatisfactionStackRAII {
};
} // namespace
-template <typename AtomicEvaluator>
+template <typename ConstraintEvaluator>
static ExprResult
calculateConstraintSatisfaction(Sema &S, const Expr *ConstraintExpr,
ConstraintSatisfaction &Satisfaction,
- AtomicEvaluator &&Evaluator) {
- ConstraintExpr = ConstraintExpr->IgnoreParenImpCasts();
+ ConstraintEvaluator &&Evaluator);
- if (LogicalBinOp BO = ConstraintExpr) {
- size_t EffectiveDetailEndIndex = Satisfaction.Details.size();
- ExprResult LHSRes = calculateConstraintSatisfaction(
- S, BO.getLHS(), Satisfaction, Evaluator);
+template <typename ConstraintEvaluator>
+static ExprResult calculateConstraintSatisfaction(
+ Sema &S, const Expr *LHS, OverloadedOperatorKind Op, const Expr *RHS,
+ ConstraintSatisfaction &Satisfaction, ConstraintEvaluator &Evaluator) {
+ size_t EffectiveDetailEndIndex = Satisfaction.Details.size();
- if (LHSRes.isInvalid())
- return ExprError();
+ ExprResult LHSRes =
+ calculateConstraintSatisfaction(S, LHS, Satisfaction, Evaluator);
- bool IsLHSSatisfied = Satisfaction.IsSatisfied;
+ if (LHSRes.isInvalid())
+ return ExprError();
- if (BO.isOr() && IsLHSSatisfied)
- // [temp.constr.op] p3
- // A disjunction is a constraint taking two operands. To determine if
- // a disjunction is satisfied, the satisfaction of the first operand
- // is checked. If that is satisfied, the disjunction is satisfied.
- // Otherwise, the disjunction is satisfied if and only if the second
- // operand is satisfied.
- // LHS is instantiated while RHS is not. Skip creating invalid BinaryOp.
- return LHSRes;
-
- if (BO.isAnd() && !IsLHSSatisfied)
- // [temp.constr.op] p2
- // A conjunction is a constraint taking two operands. To determine if
- // a conjunction is satisfied, the satisfaction of the first operand
- // is checked. If that is not satisfied, the conjunction is not
- // satisfied. Otherwise, the conjunction is satisfied if and only if
- // the second operand is satisfied.
- // LHS is instantiated while RHS is not. Skip creating invalid BinaryOp.
- return LHSRes;
-
- ExprResult RHSRes = calculateConstraintSatisfaction(
- S, BO.getRHS(), Satisfaction, std::forward<AtomicEvaluator>(Evaluator));
- if (RHSRes.isInvalid())
- return ExprError();
+ bool IsLHSSatisfied = Satisfaction.IsSatisfied;
+
+ if (Op == clang::OO_PipePipe && IsLHSSatisfied)
+ // [temp.constr.op] p3
+ // A disjunction is a constraint taking two operands. To determine if
+ // a disjunction is satisfied, the satisfaction of the first operand
+ // is checked. If that is satisfied, the disjunction is satisfied.
+ // Otherwise, the disjunction is satisfied if and only if the second
+ // operand is satisfied.
+ // LHS is instantiated while RHS is not. Skip creating invalid BinaryOp.
+ return LHSRes;
+
+ if (Op == clang::OO_AmpAmp && !IsLHSSatisfied)
+ // [temp.constr.op] p2
+ // A conjunction is a constraint taking two operands. To determine if
+ // a conjunction is satisfied, the satisfaction of the first operand
+ // is checked. If that is not satisfied, the conjunction is not
+ // satisfied. Otherwise, the conjunction is satisfied if and only if
+ // the second operand is satisfied.
+ // LHS is instantiated while RHS is not. Skip creating invalid BinaryOp.
+ return LHSRes;
+
+ ExprResult RHSRes = calculateConstraintSatisfaction(
+ S, RHS, Satisfaction, std::forward<ConstraintEvaluator>(Evaluator));
+ if (RHSRes.isInvalid())
+ return ExprError();
+
+ bool IsRHSSatisfied = Satisfaction.IsSatisfied;
+ // Current implementation adds diagnostic information about the falsity
+ // of each false atomic constraint expression when it evaluates them.
+ // When the evaluation results to `false || true`, the information
+ // generated during the evaluation of left-hand side is meaningless
+ // because the whole expression evaluates to true.
+ // The following code removes the irrelevant diagnostic information.
+ // FIXME: We should probably delay the addition of diagnostic information
+ // until we know the entire expression is false.
+ if (Op == clang::OO_PipePipe && IsRHSSatisfied) {
+ auto EffectiveDetailEnd = Satisfaction.Details.begin();
+ std::advance(EffectiveDetailEnd, EffectiveDetailEndIndex);
+ Satisfaction.Details.erase(EffectiveDetailEnd, Satisfaction.Details.end());
+ }
+ if (!LHSRes.isUsable() || !RHSRes.isUsable())
+ return ExprEmpty();
+
+ return BinaryOperator::Create(S.Context, LHSRes.get(), RHSRes.get(),
+ BinaryOperator::getOverloadedOpcode(Op),
+ S.Context.BoolTy, VK_PRValue, OK_Ordinary,
+ LHS->getBeginLoc(), FPOptionsOverride{});
+}
+
+template <typename ConstraintEvaluator>
+static ExprResult
+calculateConstraintSatisfaction(Sema &S, const CXXFoldExpr *FE,
+ ConstraintSatisfaction &Satisfaction,
+ ConstraintEvaluator &&Evaluator) {
+ bool Conjunction = FE->getOperator() == BinaryOperatorKind::BO_LAnd;
+ size_t EffectiveDetailEndIndex = Satisfaction.Details.size();
+
+ ExprResult Out;
+ if (FE->isLeftFold() && FE->getInit()) {
+ Out = calculateConstraintSatisfaction(S, FE->getInit(), Satisfaction,
+ Evaluator);
+ if (Out.isInvalid())
+ return ExprError();
+ bool IsLHSSatisfied = Satisfaction.IsSatisfied;
+ if (Conjunction && !IsLHSSatisfied) {
+ return Out;
+ }
+ if (!Conjunction && IsLHSSatisfied) {
+ return Out;
+ }
+ }
+ std::optional<unsigned> NumExpansions =
+ Evaluator.EvaluateFoldExpandedConstraintSize(FE);
+ if (!NumExpansions)
+ return ExprError();
+ for (unsigned I = 0; I < *NumExpansions; I++) {
+ Sema::ArgumentPackSubstitutionIndexRAII SubstIndex(S, I);
+ ExprResult Res = calculateConstraintSatisfaction(S, FE->getPattern(),
+ Satisfaction, Evaluator);
+ if (Res.isInvalid())
+ return ExprError();
bool IsRHSSatisfied = Satisfaction.IsSatisfied;
- // Current implementation adds diagnostic information about the falsity
- // of each false atomic constraint expression when it evaluates them.
- // When the evaluation results to `false || true`, the information
- // generated during the evaluation of left-hand side is meaningless
- // because the whole expression evaluates to true.
- // The following code removes the irrelevant diagnostic information.
- // FIXME: We should probably delay the addition of diagnostic information
- // until we know the entire expression is false.
- if (BO.isOr() && IsRHSSatisfied) {
+ if (!Conjunction && IsRHSSatisfied) {
auto EffectiveDetailEnd = Satisfaction.Details.begin();
std::advance(EffectiveDetailEnd, EffectiveDetailEndIndex);
Satisfaction.Details.erase(EffectiveDetailEnd,
Satisfaction.Details.end());
}
+ if (Out.isUnset())
+ Out = Res;
+ else if (!Res.isUnset()) {
+ Out = BinaryOperator::Create(
+ S.Context, Out.get(), Res.get(), FE->getOperator(), S.Context.BoolTy,
+ VK_PRValue, OK_Ordinary, FE->getBeginLoc(), FPOptionsOverride{});
+ }
+ if (Conjunction && !IsRHSSatisfied)
+ return Out;
+ if (!Conjunction && IsRHSSatisfied)
+ return Out;
+ }
+
+ if (FE->isRightFold() && FE->getInit()) {
+ ExprResult Res = calculateConstraintSatisfaction(S, FE->getInit(),
+ Satisfaction, Evaluator);
+ if (Out.isInvalid())
+ return ExprError();
+
+ if (Out.isUnset())
+ Out = Res;
+ else if (!Res.isUnset()) {
+ Out = BinaryOperator::Create(
+ S.Context, Out.get(), Res.get(), FE->getOperator(), S.Context.BoolTy,
+ VK_PRValue, OK_Ordinary, FE->getBeginLoc(), FPOptionsOverride{});
+ }
+ }
- return BO.recreateBinOp(S, LHSRes, RHSRes);
+ if (Out.isUnset()) {
+ Satisfaction.IsSatisfied = Conjunction;
+ Out = S.BuildEmptyCXXFoldExpr(FE->getBeginLoc(), FE->getOperator());
+ }
+ return Out;
+}
+
+template <typename ConstraintEvaluator>
+static ExprResult
+calculateConstraintSatisfaction(Sema &S, const Expr *ConstraintExpr,
+ ConstraintSatisfaction &Satisfaction,
+ ConstraintEvaluator &&Evaluator) {
+ ConstraintExpr = ConstraintExpr->IgnoreParenImpCasts();
+
+ if (LogicalBinOp BO = ConstraintExpr) {
+
+ return calculateConstraintSatisfaction(
+ S, BO.getLHS(), BO.getOp(), BO.getRHS(), Satisfaction, Evaluator);
}
if (auto *C = dyn_cast<ExprWithCleanups>(ConstraintExpr)) {
@@ -243,11 +339,19 @@ calculateConstraintSatisfaction(Sema &S, const Expr *ConstraintExpr,
// evaluate these as if the cleanups didn't exist.
return calculateConstraintSatisfaction(
S, C->getSubExpr(), Satisfaction,
- std::forward<AtomicEvaluator>(Evaluator));
+ std::forward<ConstraintEvaluator>(Evaluator));
+ }
+
+ if (auto *FE = dyn_cast<CXXFoldExpr>(ConstraintExpr);
+ FE && S.getLangOpts().CPlusPlus26 &&
+ (FE->getOperator() == BinaryOperatorKind::BO_LAnd ||
+ FE->getOperator() == BinaryOperatorKind::BO_LOr)) {
+ return calculateConstraintSatisfaction(S, FE, Satisfaction, Evaluator);
}
// An atomic constraint expression
- ExprResult SubstitutedAtomicExpr = Evaluator(ConstraintExpr);
+ ExprResult SubstitutedAtomicExpr =
+ Evaluator.EvaluateAtomicConstraint(ConstraintExpr);
if (SubstitutedAtomicExpr.isInvalid())
return ExprError();
@@ -336,92 +440,133 @@ static ExprResult calculateConstraintSatisfaction(
Sema &S, const NamedDecl *Template, SourceLocation TemplateNameLoc,
const MultiLevelTemplateArgumentList &MLTAL, const Expr *ConstraintExpr,
ConstraintSatisfaction &Satisfaction) {
- return calculateConstraintSatisfaction(
- S, ConstraintExpr, Satisfaction, [&](const Expr *AtomicExpr) {
- EnterExpressionEvaluationContext ConstantEvaluated(
- S, Sema::ExpressionEvaluationContext::ConstantEvaluated,
- Sema::ReuseLambdaContextDecl);
-
- // Atomic constraint - substitute arguments and check satisfaction.
- ExprResult SubstitutedExpression;
- {
- TemplateDeductionInfo Info(TemplateNameLoc);
- Sema::InstantiatingTemplate Inst(S, AtomicExpr->getBeginLoc(),
- Sema::InstantiatingTemplate::ConstraintSubstitution{},
- const_cast<NamedDecl *>(Template), Info,
- AtomicExpr->getSourceRange());
- if (Inst.isInvalid())
+
+ struct ConstraintEvaluator {
+ Sema &S;
+ const NamedDecl *Template;
+ SourceLocation TemplateNameLoc;
+ const MultiLevelTemplateArgumentList &MLTAL;
+ ConstraintSatisfaction &Satisfaction;
+
+ ExprResult EvaluateAtomicConstraint(const Expr *AtomicExpr) {
+ EnterExpressionEvaluationContext ConstantEvaluated(
+ S, Sema::ExpressionEvaluationContext::ConstantEvaluated,
+ Sema::ReuseLambdaContextDecl);
+
+ // Atomic constraint - substitute arguments and check satisfaction...
[truncated]
|
AaronBallman
reviewed
Jul 9, 2024
AaronBallman
approved these changes
Jul 10, 2024
There was a problem hiding this comment.
Changes LGTM but this is complicated enough that it would be nice if @hubert-reinterpretcast could also take a look, because @erichkeane isn't back from leave yet.
Comment on lines
274
to
275
| const NormalForm PDNF = makeDNF(this->Constraint); | ||
| const NormalForm QCNF = makeCNF(Other.Constraint); |
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I'll merge that. If there are further feedback I'd be happy to do post commit reviews and additional work on this feature @AaronBallman Thanks for the review! |
|
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/18/builds/877 Here is the relevant piece of the build log for the reference: |
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…old expressions" (#99007) Summary: Reverts #98160 Breaks CI on some architectures Test Plan: Reviewers: Subscribers: Tasks: Tags: Differential Revision: https://phabricator.intern.facebook.com/D60251756
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Implement https://isocpp.org/files/papers/P2963R3.pdf