[clang] 12c90e2 - [clang] NRVO: Improvements and handling of more cases.
Matheus Izvekov via cfe-commits
cfe-commits at lists.llvm.org
Wed Jun 16 16:56:54 PDT 2021
Author: Matheus Izvekov
Date: 2021-06-17T01:56:38+02:00
New Revision: 12c90e2e25dfd1d38250055efc21acb42d158912
URL: https://github.com/llvm/llvm-project/commit/12c90e2e25dfd1d38250055efc21acb42d158912
DIFF: https://github.com/llvm/llvm-project/commit/12c90e2e25dfd1d38250055efc21acb42d158912.diff
LOG: [clang] NRVO: Improvements and handling of more cases.
This expands NRVO propagation for more cases:
Parse analysis improvement:
* Lambdas and Blocks with dependent return type can have their variables
marked as NRVO Candidates.
Variable instantiation improvements:
* Fixes crash when instantiating NRVO variables in Blocks.
* Functions, Lambdas, and Blocks which have auto return type have their
variables' NRVO status propagated. For Blocks with non-auto return type,
as a limitation, this propagation does not consider the actual return
type.
This also implements exclusion of VarDecls which are references to
dependent types.
Signed-off-by: Matheus Izvekov <mizvekov at gmail.com>
Reviewed By: Quuxplusone
Differential Revision: https://reviews.llvm.org/D99696
Added:
clang/test/SemaObjCXX/block-capture.mm
Modified:
clang/include/clang/Sema/Sema.h
clang/lib/Sema/Sema.cpp
clang/lib/Sema/SemaCoroutine.cpp
clang/lib/Sema/SemaExprCXX.cpp
clang/lib/Sema/SemaStmt.cpp
clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
clang/test/CodeGen/nrvo-tracking.cpp
Removed:
################################################################################
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 6ade9d7691266..f7ec89a33e00c 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -3455,12 +3455,6 @@ class Sema final {
bool DiagnoseMultipleUserDefinedConversion(Expr *From, QualType ToType);
bool isSameOrCompatibleFunctionType(CanQualType Param, CanQualType Arg);
- ExprResult PerformMoveOrCopyInitialization(const InitializedEntity &Entity,
- const VarDecl *NRVOCandidate,
- QualType ResultType,
- Expr *Value,
- bool AllowNRVO = true);
-
bool CanPerformAggregateInitializationForOverloadResolution(
const InitializedEntity &Entity, InitListExpr *From);
@@ -4760,28 +4754,30 @@ class Sema final {
SourceLocation Loc,
unsigned NumParams);
- enum CopyElisionSemanticsKind {
- CES_Strict = 0,
- CES_AllowParameters = 1,
- CES_AllowDifferentTypes = 2,
- CES_AllowExceptionVariables = 4,
- CES_AllowRValueReferenceType = 8,
- CES_ImplicitlyMovableCXX11CXX14CXX17 =
- (CES_AllowParameters | CES_AllowDifferentTypes),
- CES_ImplicitlyMovableCXX20 =
- (CES_AllowParameters | CES_AllowDifferentTypes |
- CES_AllowExceptionVariables | CES_AllowRValueReferenceType),
+ struct NamedReturnInfo {
+ const VarDecl *Candidate;
+
+ enum Status : uint8_t { None, MoveEligible, MoveEligibleAndCopyElidable };
+ Status S;
+
+ bool isMoveEligible() const { return S != None; };
+ bool isCopyElidable() const { return S == MoveEligibleAndCopyElidable; }
};
+ NamedReturnInfo getNamedReturnInfo(const Expr *E, bool ForceCXX20 = false);
+ NamedReturnInfo getNamedReturnInfo(const VarDecl *VD,
+ bool ForceCXX20 = false);
+ const VarDecl *getCopyElisionCandidate(NamedReturnInfo &Info,
+ QualType ReturnType);
- VarDecl *getCopyElisionCandidate(QualType ReturnType, Expr *E,
- CopyElisionSemanticsKind CESK);
- bool isCopyElisionCandidate(QualType ReturnType, const VarDecl *VD,
- CopyElisionSemanticsKind CESK);
+ ExprResult PerformMoveOrCopyInitialization(const InitializedEntity &Entity,
+ const NamedReturnInfo &NRInfo,
+ Expr *Value);
StmtResult ActOnReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp,
Scope *CurScope);
StmtResult BuildReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp);
- StmtResult ActOnCapScopeReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp);
+ StmtResult ActOnCapScopeReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp,
+ NamedReturnInfo &NRInfo);
StmtResult ActOnGCCAsmStmt(SourceLocation AsmLoc, bool IsSimple,
bool IsVolatile, unsigned NumOutputs,
diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
index 850c189cc51a3..b87e2c2bea80d 100644
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -1955,6 +1955,9 @@ void Sema::RecordParsingTemplateParameterDepth(unsigned Depth) {
// Check that the type of the VarDecl has an accessible copy constructor and
// resolve its destructor's exception specification.
+// This also performs initialization of block variables when they are moved
+// to the heap. It uses the same rules as applicable for implicit moves
+// according to the C++ standard in effect ([class.copy.elision]p3).
static void checkEscapingByref(VarDecl *VD, Sema &S) {
QualType T = VD->getType();
EnterExpressionEvaluationContext scope(
@@ -1963,8 +1966,9 @@ static void checkEscapingByref(VarDecl *VD, Sema &S) {
Expr *VarRef =
new (S.Context) DeclRefExpr(S.Context, VD, false, T, VK_LValue, Loc);
ExprResult Result = S.PerformMoveOrCopyInitialization(
- InitializedEntity::InitializeBlock(Loc, T, false), VD, VD->getType(),
- VarRef, /*AllowNRVO=*/true);
+ InitializedEntity::InitializeBlock(Loc, T, false),
+ Sema::NamedReturnInfo{VD, Sema::NamedReturnInfo::MoveEligible}, VarRef);
+
if (!Result.isInvalid()) {
Result = S.MaybeCreateExprWithCleanups(Result);
Expr *Init = Result.getAs<Expr>();
diff --git a/clang/lib/Sema/SemaCoroutine.cpp b/clang/lib/Sema/SemaCoroutine.cpp
index 67c64782a0e82..187e7a0516d10 100644
--- a/clang/lib/Sema/SemaCoroutine.cpp
+++ b/clang/lib/Sema/SemaCoroutine.cpp
@@ -995,17 +995,13 @@ StmtResult Sema::BuildCoreturnStmt(SourceLocation Loc, Expr *E,
}
// Move the return value if we can
- if (E) {
- const VarDecl *NRVOCandidate = this->getCopyElisionCandidate(
- E->getType(), E, CES_ImplicitlyMovableCXX20);
- if (NRVOCandidate) {
- InitializedEntity Entity =
- InitializedEntity::InitializeResult(Loc, E->getType(), NRVOCandidate);
- ExprResult MoveResult = this->PerformMoveOrCopyInitialization(
- Entity, NRVOCandidate, E->getType(), E);
- if (MoveResult.get())
- E = MoveResult.get();
- }
+ NamedReturnInfo NRInfo = getNamedReturnInfo(E, /*ForceCXX20=*/true);
+ if (NRInfo.isMoveEligible()) {
+ InitializedEntity Entity = InitializedEntity::InitializeResult(
+ Loc, E->getType(), NRInfo.Candidate);
+ ExprResult MoveResult = PerformMoveOrCopyInitialization(Entity, NRInfo, E);
+ if (MoveResult.get())
+ E = MoveResult.get();
}
// FIXME: If the operand is a reference to a variable that's about to go out
@@ -1570,7 +1566,7 @@ bool CoroutineStmtBuilder::makeGroDeclAndReturnStmt() {
// Trigger a nice error message.
InitializedEntity Entity =
InitializedEntity::InitializeResult(Loc, FnRetType, false);
- S.PerformMoveOrCopyInitialization(Entity, nullptr, FnRetType, ReturnValue);
+ S.PerformCopyInitialization(Entity, SourceLocation(), ReturnValue);
noteMemberDeclaredHere(S, ReturnValue, Fn);
return false;
}
@@ -1586,8 +1582,8 @@ bool CoroutineStmtBuilder::makeGroDeclAndReturnStmt() {
return false;
InitializedEntity Entity = InitializedEntity::InitializeVariable(GroDecl);
- ExprResult Res = S.PerformMoveOrCopyInitialization(Entity, nullptr, GroType,
- this->ReturnValue);
+ ExprResult Res =
+ S.PerformCopyInitialization(Entity, SourceLocation(), ReturnValue);
if (Res.isInvalid())
return false;
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index 2bf575e41a9b1..9d554b5b3a909 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -873,15 +873,13 @@ ExprResult Sema::BuildCXXThrow(SourceLocation OpLoc, Expr *Ex,
// operation from the operand to the exception object (15.1) can be
// omitted by constructing the automatic object directly into the
// exception object
- const VarDecl *NRVOVariable = nullptr;
- if (IsThrownVarInScope)
- NRVOVariable = getCopyElisionCandidate(QualType(), Ex, CES_Strict);
+ NamedReturnInfo NRInfo =
+ IsThrownVarInScope ? getNamedReturnInfo(Ex) : NamedReturnInfo();
InitializedEntity Entity = InitializedEntity::InitializeException(
OpLoc, ExceptionObjectTy,
- /*NRVO=*/NRVOVariable != nullptr);
- ExprResult Res = PerformMoveOrCopyInitialization(
- Entity, NRVOVariable, QualType(), Ex, IsThrownVarInScope);
+ /*NRVO=*/NRInfo.isCopyElidable());
+ ExprResult Res = PerformMoveOrCopyInitialization(Entity, NRInfo, Ex);
if (Res.isInvalid())
return ExprError();
Ex = Res.get();
diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp
index 8bb2e0e8c8633..136e39198c728 100644
--- a/clang/lib/Sema/SemaStmt.cpp
+++ b/clang/lib/Sema/SemaStmt.cpp
@@ -3307,99 +3307,153 @@ Sema::ActOnBreakStmt(SourceLocation BreakLoc, Scope *CurScope) {
return new (Context) BreakStmt(BreakLoc);
}
-/// Determine whether the given expression is a candidate for
-/// copy elision in either a return statement or a throw expression.
+/// Determine whether the given expression might be move-eligible or
+/// copy-elidable in either a (co_)return statement or throw expression,
+/// without considering function return type, if applicable.
///
-/// \param ReturnType If we're determining the copy elision candidate for
-/// a return statement, this is the return type of the function. If we're
-/// determining the copy elision candidate for a throw expression, this will
-/// be a NULL type.
+/// \param E The expression being returned from the function or block,
+/// being thrown, or being co_returned from a coroutine.
///
-/// \param E The expression being returned from the function or block, or
-/// being thrown.
+/// \param ForceCXX20 Overrides detection of current language mode
+/// and uses the rules for C++20.
///
-/// \param CESK Whether we allow function parameters or
-/// id-expressions that could be moved out of the function to be considered NRVO
-/// candidates. C++ prohibits these for NRVO itself, but we re-use this logic to
-/// determine whether we should try to move as part of a return or throw (which
-/// does allow function parameters).
-///
-/// \returns The NRVO candidate variable, if the return statement may use the
-/// NRVO, or NULL if there is no such candidate.
-VarDecl *Sema::getCopyElisionCandidate(QualType ReturnType, Expr *E,
- CopyElisionSemanticsKind CESK) {
+/// \returns An aggregate which contains the Candidate and isMoveEligible
+/// and isCopyElidable methods. If Candidate is non-null, it means
+/// isMoveEligible() would be true under the most permissive language standard.
+Sema::NamedReturnInfo Sema::getNamedReturnInfo(const Expr *E, bool ForceCXX20) {
+ if (!E)
+ return NamedReturnInfo();
// - in a return statement in a function [where] ...
// ... the expression is the name of a non-volatile automatic object ...
- DeclRefExpr *DR = dyn_cast<DeclRefExpr>(E->IgnoreParens());
+ const auto *DR = dyn_cast<DeclRefExpr>(E->IgnoreParens());
if (!DR || DR->refersToEnclosingVariableOrCapture())
- return nullptr;
- VarDecl *VD = dyn_cast<VarDecl>(DR->getDecl());
+ return NamedReturnInfo();
+ const auto *VD = dyn_cast<VarDecl>(DR->getDecl());
if (!VD)
- return nullptr;
+ return NamedReturnInfo();
+ return getNamedReturnInfo(VD, ForceCXX20);
+}
- if (isCopyElisionCandidate(ReturnType, VD, CESK))
- return VD;
- return nullptr;
+/// Updates the status in the given NamedReturnInfo object to disallow
+/// copy elision, and optionally also implicit move.
+///
+/// \param Info The NamedReturnInfo object to update.
+///
+/// \param CanMove If true, disallow only copy elision.
+/// If false, also disallow implcit move.
+static void disallowNRVO(Sema::NamedReturnInfo &Info, bool CanMove) {
+ Info.S = std::min(Info.S, CanMove ? Sema::NamedReturnInfo::MoveEligible
+ : Sema::NamedReturnInfo::None);
}
-bool Sema::isCopyElisionCandidate(QualType ReturnType, const VarDecl *VD,
- CopyElisionSemanticsKind CESK) {
- QualType VDType = VD->getType();
+/// Determine whether the given NRVO candidate variable is move-eligible or
+/// copy-elidable, without considering function return type.
+///
+/// \param VD The NRVO candidate variable.
+///
+/// \param ForceCXX20 Overrides detection of current language mode
+/// and uses the rules for C++20.
+///
+/// \returns An aggregate which contains the Candidate and isMoveEligible
+/// and isCopyElidable methods. If Candidate is non-null, it means
+/// isMoveEligible() would be true under the most permissive language standard.
+Sema::NamedReturnInfo Sema::getNamedReturnInfo(const VarDecl *VD,
+ bool ForceCXX20) {
+ bool hasCXX11 = getLangOpts().CPlusPlus11 || ForceCXX20;
+ bool hasCXX20 = getLangOpts().CPlusPlus20 || ForceCXX20;
+ NamedReturnInfo Info{VD, NamedReturnInfo::MoveEligibleAndCopyElidable};
+
+ // C++20 [class.copy.elision]p3:
// - in a return statement in a function with ...
- // ... a class return type ...
- if (!ReturnType.isNull() && !ReturnType->isDependentType()) {
- if (!ReturnType->isRecordType())
- return false;
- // ... the same cv-unqualified type as the function return type ...
- // When considering moving this expression out, allow dissimilar types.
- if (!(CESK & CES_AllowDifferentTypes) && !VDType->isDependentType() &&
- !Context.hasSameUnqualifiedType(ReturnType, VDType))
- return false;
- }
+ // (other than a function ... parameter)
+ if (VD->getKind() == Decl::ParmVar)
+ disallowNRVO(Info, hasCXX11);
+ else if (VD->getKind() != Decl::Var)
+ return NamedReturnInfo();
- // ...object (other than a function or catch-clause parameter)...
- if (VD->getKind() != Decl::Var &&
- !((CESK & CES_AllowParameters) && VD->getKind() == Decl::ParmVar))
- return false;
- if (!(CESK & CES_AllowExceptionVariables) && VD->isExceptionVariable())
- return false;
+ // (other than ... a catch-clause parameter)
+ if (VD->isExceptionVariable())
+ disallowNRVO(Info, hasCXX20);
// ...automatic...
- if (!VD->hasLocalStorage()) return false;
+ if (!VD->hasLocalStorage())
+ return NamedReturnInfo();
- // Return false if VD is a __block variable. We don't want to implicitly move
- // out of a __block variable during a return because we cannot assume the
- // variable will no longer be used.
+ // We don't want to implicitly move out of a __block variable during a return
+ // because we cannot assume the variable will no longer be used.
if (VD->hasAttr<BlocksAttr>())
- return false;
+ return NamedReturnInfo();
+ QualType VDType = VD->getType();
if (VDType->isObjectType()) {
// C++17 [class.copy.elision]p3:
// ...non-volatile automatic object...
if (VDType.isVolatileQualified())
- return false;
+ return NamedReturnInfo();
} else if (VDType->isRValueReferenceType()) {
// C++20 [class.copy.elision]p3:
- // ...either a non-volatile object or an rvalue reference to a non-volatile object type...
- if (!(CESK & CES_AllowRValueReferenceType))
- return false;
+ // ...either a non-volatile object or an rvalue reference to a non-volatile
+ // object type...
QualType VDReferencedType = VDType.getNonReferenceType();
- if (VDReferencedType.isVolatileQualified() || !VDReferencedType->isObjectType())
- return false;
+ if (VDReferencedType.isVolatileQualified() ||
+ !VDReferencedType->isObjectType())
+ return NamedReturnInfo();
+ disallowNRVO(Info, hasCXX20);
} else {
- return false;
+ return NamedReturnInfo();
}
- if (CESK & CES_AllowDifferentTypes)
- return true;
-
// Variables with higher required alignment than their type's ABI
// alignment cannot use NRVO.
if (!VDType->isDependentType() && VD->hasAttr<AlignedAttr>() &&
Context.getDeclAlign(VD) > Context.getTypeAlignInChars(VDType))
- return false;
+ disallowNRVO(Info, hasCXX11);
- return true;
+ return Info;
+}
+
+/// Updates given NamedReturnInfo's move-eligible and
+/// copy-elidable statuses, considering the function
+/// return type criteria as applicable to return statements.
+///
+/// \param Info The NamedReturnInfo object to update.
+///
+/// \param ReturnType This is the return type of the function.
+/// \returns The copy elision candidate, in case the initial return expression
+/// was copy elidable, or nullptr otherwise.
+const VarDecl *Sema::getCopyElisionCandidate(NamedReturnInfo &Info,
+ QualType ReturnType) {
+ if (!Info.Candidate)
+ return nullptr;
+
+ auto invalidNRVO = [&] {
+ Info = NamedReturnInfo();
+ return nullptr;
+ };
+
+ // If we got a non-deduced auto ReturnType, we are in a dependent context and
+ // there is no point in allowing copy elision since we won't have it deduced
+ // by the point the VardDecl is instantiated, which is the last chance we have
+ // of deciding if the candidate is really copy elidable.
+ if ((ReturnType->getTypeClass() == Type::TypeClass::Auto &&
+ ReturnType->isCanonicalUnqualified()) ||
+ ReturnType->isSpecificBuiltinType(BuiltinType::Dependent))
+ return invalidNRVO();
+
+ if (!ReturnType->isDependentType()) {
+ // - in a return statement in a function with ...
+ // ... a class return type ...
+ if (!ReturnType->isRecordType())
+ return invalidNRVO();
+
+ QualType VDType = Info.Candidate->getType();
+ // ... the same cv-unqualified type as the function return type ...
+ // When considering moving this expression out, allow dissimilar types.
+ if (!VDType->isDependentType() &&
+ !Context.hasSameUnqualifiedType(ReturnType, VDType))
+ disallowNRVO(Info, getLangOpts().CPlusPlus11);
+ }
+ return Info.isCopyElidable() ? Info.Candidate : nullptr;
}
/// Try to perform the initialization of a potentially-movable value,
@@ -3424,8 +3478,7 @@ bool Sema::isCopyElisionCandidate(QualType ReturnType, const VarDecl *VD,
/// the selected constructor/operator doesn't match the additional criteria, we
/// need to do the second overload resolution.
static bool TryMoveInitialization(Sema &S, const InitializedEntity &Entity,
- const VarDecl *NRVOCandidate,
- QualType ResultType, Expr *&Value,
+ const VarDecl *NRVOCandidate, Expr *&Value,
bool ConvertingConstructorsOnly,
bool IsDiagnosticsCheck, ExprResult &Res) {
ImplicitCastExpr AsRvalue(ImplicitCastExpr::OnStack, Value->getType(),
@@ -3508,63 +3561,41 @@ static bool TryMoveInitialization(Sema &S, const InitializedEntity &Entity,
/// This routine implements C++20 [class.copy.elision]p3, which attempts to
/// treat returned lvalues as rvalues in certain cases (to prefer move
/// construction), then falls back to treating them as lvalues if that failed.
-ExprResult Sema::PerformMoveOrCopyInitialization(
- const InitializedEntity &Entity, const VarDecl *NRVOCandidate,
- QualType ResultType, Expr *Value, bool AllowNRVO) {
- ExprResult Res = ExprError();
- bool NeedSecondOverloadResolution = true;
-
- if (AllowNRVO) {
- CopyElisionSemanticsKind CESK = CES_Strict;
- if (getLangOpts().CPlusPlus20) {
- CESK = CES_ImplicitlyMovableCXX20;
- } else if (getLangOpts().CPlusPlus11) {
- CESK = CES_ImplicitlyMovableCXX11CXX14CXX17;
- }
-
- if (!NRVOCandidate) {
- NRVOCandidate = getCopyElisionCandidate(ResultType, Value, CESK);
- }
-
- if (NRVOCandidate) {
- NeedSecondOverloadResolution =
- TryMoveInitialization(*this, Entity, NRVOCandidate, ResultType, Value,
- !getLangOpts().CPlusPlus20, false, Res);
+ExprResult
+Sema::PerformMoveOrCopyInitialization(const InitializedEntity &Entity,
+ const NamedReturnInfo &NRInfo,
+ Expr *Value) {
+
+ if (NRInfo.Candidate) {
+ if (NRInfo.isMoveEligible()) {
+ ExprResult Res;
+ if (!TryMoveInitialization(*this, Entity, NRInfo.Candidate, Value,
+ !getLangOpts().CPlusPlus20, false, Res))
+ return Res;
}
-
- if (!getLangOpts().CPlusPlus20 && NeedSecondOverloadResolution &&
- !getDiagnostics().isIgnored(diag::warn_return_std_move,
+ if (!getDiagnostics().isIgnored(diag::warn_return_std_move,
Value->getExprLoc())) {
- const VarDecl *FakeNRVOCandidate = getCopyElisionCandidate(
- QualType(), Value, CES_ImplicitlyMovableCXX20);
- if (FakeNRVOCandidate) {
- QualType QT = FakeNRVOCandidate->getType();
- if (QT->isLValueReferenceType()) {
- // Adding 'std::move' around an lvalue reference variable's name is
- // dangerous. Don't suggest it.
- } else if (QT.getNonReferenceType()
- .getUnqualifiedType()
- .isTriviallyCopyableType(Context)) {
- // Adding 'std::move' around a trivially copyable variable is probably
- // pointless. Don't suggest it.
- } else {
- ExprResult FakeRes = ExprError();
- Expr *FakeValue = Value;
- TryMoveInitialization(*this, Entity, FakeNRVOCandidate, ResultType,
- FakeValue, false, true, FakeRes);
- if (!FakeRes.isInvalid()) {
- bool IsThrow =
- (Entity.getKind() == InitializedEntity::EK_Exception);
- SmallString<32> Str;
- Str += "std::move(";
- Str += FakeNRVOCandidate->getDeclName().getAsString();
- Str += ")";
- Diag(Value->getExprLoc(), diag::warn_return_std_move)
- << Value->getSourceRange()
- << FakeNRVOCandidate->getDeclName() << IsThrow;
- Diag(Value->getExprLoc(), diag::note_add_std_move)
- << FixItHint::CreateReplacement(Value->getSourceRange(), Str);
- }
+ QualType QT = NRInfo.Candidate->getType();
+ if (QT.getNonReferenceType().getUnqualifiedType().isTriviallyCopyableType(
+ Context)) {
+ // Adding 'std::move' around a trivially copyable variable is probably
+ // pointless. Don't suggest it.
+ } else {
+ ExprResult FakeRes = ExprError();
+ Expr *FakeValue = Value;
+ TryMoveInitialization(*this, Entity, NRInfo.Candidate, FakeValue, false,
+ true, FakeRes);
+ if (!FakeRes.isInvalid()) {
+ bool IsThrow = (Entity.getKind() == InitializedEntity::EK_Exception);
+ SmallString<32> Str;
+ Str += "std::move(";
+ Str += NRInfo.Candidate->getDeclName().getAsString();
+ Str += ")";
+ Diag(Value->getExprLoc(), diag::warn_return_std_move)
+ << Value->getSourceRange() << NRInfo.Candidate->getDeclName()
+ << IsThrow;
+ Diag(Value->getExprLoc(), diag::note_add_std_move)
+ << FixItHint::CreateReplacement(Value->getSourceRange(), Str);
}
}
}
@@ -3573,10 +3604,7 @@ ExprResult Sema::PerformMoveOrCopyInitialization(
// Either we didn't meet the criteria for treating an lvalue as an rvalue,
// above, or overload resolution failed. Either way, we need to try
// (again) now with the return value expression as written.
- if (NeedSecondOverloadResolution)
- Res = PerformCopyInitialization(Entity, SourceLocation(), Value);
-
- return Res;
+ return PerformCopyInitialization(Entity, SourceLocation(), Value);
}
/// Determine whether the declared return type of the specified function
@@ -3590,8 +3618,9 @@ static bool hasDeducedReturnType(FunctionDecl *FD) {
/// ActOnCapScopeReturnStmt - Utility routine to type-check return statements
/// for capturing scopes.
///
-StmtResult
-Sema::ActOnCapScopeReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp) {
+StmtResult Sema::ActOnCapScopeReturnStmt(SourceLocation ReturnLoc,
+ Expr *RetValExp,
+ NamedReturnInfo &NRInfo) {
// If this is the first return we've seen, infer the return type.
// [expr.prim.lambda]p4 in C++11; block literals follow the same rules.
CapturingScopeInfo *CurCap = cast<CapturingScopeInfo>(getCurFunction());
@@ -3670,7 +3699,7 @@ Sema::ActOnCapScopeReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp) {
if (CurCap->ReturnType.isNull())
CurCap->ReturnType = FnRetType;
}
- assert(!FnRetType.isNull());
+ const VarDecl *NRVOCandidate = getCopyElisionCandidate(NRInfo, FnRetType);
if (auto *CurBlock = dyn_cast<BlockScopeInfo>(CurCap)) {
if (CurBlock->FunctionType->castAs<FunctionType>()->getNoReturnAttr()) {
@@ -3693,7 +3722,6 @@ Sema::ActOnCapScopeReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp) {
// Otherwise, verify that this result type matches the previous one. We are
// pickier with blocks than for normal functions because we don't have GCC
// compatibility to worry about here.
- const VarDecl *NRVOCandidate = nullptr;
if (FnRetType->isDependentType()) {
// Delay processing for now. TODO: there are lots of dependent
// types we can conclusively prove aren't void.
@@ -3721,20 +3749,15 @@ Sema::ActOnCapScopeReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp) {
// In C++ the return statement is handled via a copy initialization.
// the C version of which boils down to CheckSingleAssignmentConstraints.
- NRVOCandidate = getCopyElisionCandidate(FnRetType, RetValExp, CES_Strict);
- InitializedEntity Entity = InitializedEntity::InitializeResult(ReturnLoc,
- FnRetType,
- NRVOCandidate != nullptr);
- ExprResult Res = PerformMoveOrCopyInitialization(Entity, NRVOCandidate,
- FnRetType, RetValExp);
+ InitializedEntity Entity = InitializedEntity::InitializeResult(
+ ReturnLoc, FnRetType, NRVOCandidate != nullptr);
+ ExprResult Res = PerformMoveOrCopyInitialization(Entity, NRInfo, RetValExp);
if (Res.isInvalid()) {
// FIXME: Cleanup temporaries here, anyway?
return StmtError();
}
RetValExp = Res.get();
CheckReturnValExpr(RetValExp, FnRetType, ReturnLoc);
- } else {
- NRVOCandidate = getCopyElisionCandidate(FnRetType, RetValExp, CES_Strict);
}
if (RetValExp) {
@@ -3943,8 +3966,10 @@ StmtResult Sema::BuildReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp) {
if (RetValExp && DiagnoseUnexpandedParameterPack(RetValExp))
return StmtError();
+ NamedReturnInfo NRInfo = getNamedReturnInfo(RetValExp);
+
if (isa<CapturingScopeInfo>(getCurFunction()))
- return ActOnCapScopeReturnStmt(ReturnLoc, RetValExp);
+ return ActOnCapScopeReturnStmt(ReturnLoc, RetValExp, NRInfo);
QualType FnRetType;
QualType RelatedRetType;
@@ -4016,6 +4041,7 @@ StmtResult Sema::BuildReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp) {
}
}
}
+ const VarDecl *NRVOCandidate = getCopyElisionCandidate(NRInfo, FnRetType);
bool HasDependentReturnType = FnRetType->isDependentType();
@@ -4122,8 +4148,6 @@ StmtResult Sema::BuildReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp) {
/* NRVOCandidate=*/nullptr);
} else {
assert(RetValExp || HasDependentReturnType);
- const VarDecl *NRVOCandidate = nullptr;
-
QualType RetType = RelatedRetType.isNull() ? FnRetType : RelatedRetType;
// C99 6.8.6.4p3(136): The return statement is not an assignment. The
@@ -4132,15 +4156,12 @@ StmtResult Sema::BuildReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp) {
// In C++ the return statement is handled via a copy initialization,
// the C version of which boils down to CheckSingleAssignmentConstraints.
- if (RetValExp)
- NRVOCandidate = getCopyElisionCandidate(FnRetType, RetValExp, CES_Strict);
if (!HasDependentReturnType && !RetValExp->isTypeDependent()) {
// we have a non-void function with an expression, continue checking
- InitializedEntity Entity = InitializedEntity::InitializeResult(ReturnLoc,
- RetType,
- NRVOCandidate != nullptr);
- ExprResult Res = PerformMoveOrCopyInitialization(Entity, NRVOCandidate,
- RetType, RetValExp);
+ InitializedEntity Entity = InitializedEntity::InitializeResult(
+ ReturnLoc, RetType, NRVOCandidate != nullptr);
+ ExprResult Res =
+ PerformMoveOrCopyInitialization(Entity, NRInfo, RetValExp);
if (Res.isInvalid()) {
// FIXME: Clean up temporaries here anyway?
return StmtError();
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index b2590d3deaad7..0fa42c5494213 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -23,6 +23,7 @@
#include "clang/Basic/TargetInfo.h"
#include "clang/Sema/Initialization.h"
#include "clang/Sema/Lookup.h"
+#include "clang/Sema/ScopeInfo.h"
#include "clang/Sema/SemaInternal.h"
#include "clang/Sema/Template.h"
#include "clang/Sema/TemplateInstCallback.h"
@@ -1085,11 +1086,30 @@ Decl *TemplateDeclInstantiator::VisitVarDecl(VarDecl *D,
SemaRef.BuildVariableInstantiation(Var, D, TemplateArgs, LateAttrs, Owner,
StartingScope, InstantiatingVarTemplate);
-
if (D->isNRVOVariable()) {
- QualType ReturnType = cast<FunctionDecl>(DC)->getReturnType();
- if (SemaRef.isCopyElisionCandidate(ReturnType, Var, Sema::CES_Strict))
- Var->setNRVOVariable(true);
+ QualType RT;
+ if (auto *F = dyn_cast<FunctionDecl>(DC))
+ RT = F->getReturnType();
+ else if (isa<BlockDecl>(DC))
+ RT = cast<FunctionType>(SemaRef.getCurBlock()->FunctionType)
+ ->getReturnType();
+ else
+ llvm_unreachable("Unknown context type");
+
+ // This is the last chance we have of checking copy elision eligibility
+ // for functions in dependent contexts. The sema actions for building
+ // the return statement during template instantiation will have no effect
+ // regarding copy elision, since NRVO propagation runs on the scope exit
+ // actions, and these are not run on instantiation.
+ // This might run through some VarDecls which were returned from non-taken
+ // 'if constexpr' branches, and these will end up being constructed on the
+ // return slot even if they will never be returned, as a sort of accidental
+ // 'optimization'. Notably, functions with 'auto' return types won't have it
+ // deduced by this point. Coupled with the limitation described
+ // previously, this makes it very hard to support copy elision for these.
+ Sema::NamedReturnInfo Info = SemaRef.getNamedReturnInfo(Var);
+ bool NRVO = SemaRef.getCopyElisionCandidate(Info, RT) != nullptr;
+ Var->setNRVOVariable(NRVO);
}
Var->setImplicit(D->isImplicit());
diff --git a/clang/test/CodeGen/nrvo-tracking.cpp b/clang/test/CodeGen/nrvo-tracking.cpp
index db5aa198621ae..7893140e1010a 100644
--- a/clang/test/CodeGen/nrvo-tracking.cpp
+++ b/clang/test/CodeGen/nrvo-tracking.cpp
@@ -29,8 +29,6 @@ L(2, t, X&);
// CHECK-LABEL: define{{.*}} void @_Z2l3v
// CHECK: call {{.*}} @_ZN1XC1Ev
-// CHECK-NEXT: call {{.*}} @_ZN1XC1EOS_
-// CHECK-NEXT: call void @llvm.lifetime.end
// CHECK-NEXT: call void @llvm.lifetime.end
// CHECK-NEXT: ret void
L(3, t, T);
@@ -152,7 +150,11 @@ F(8, (t), decltype(auto));
}; }()(); \
}
-//B(1, X); // Uncomment this line at your own peril ;)
+// CHECK-LABEL: define{{.*}} void @_Z2b1v
+// CHECK: call {{.*}} @_ZN1XC1Ev
+// CHECK-NEXT: call void @llvm.lifetime.end
+// CHECK-NEXT: ret void
+B(1, X);
// CHECK-LABEL: define{{.*}} void @_Z2b2v
// CHECK: call {{.*}} @_ZN1XC1Ev
@@ -164,8 +166,6 @@ B(2, X&);
// CHECK-LABEL: define{{.*}} void @_Z2b3v
// CHECK: call {{.*}} @_ZN1XC1Ev
-// CHECK-NEXT: call {{.*}} @_ZN1XC1EOS_
-// CHECK-NEXT: call void @llvm.lifetime.end
// CHECK-NEXT: call void @llvm.lifetime.end
// CHECK-NEXT: ret void
B(3, T);
@@ -187,3 +187,26 @@ B(4, T&);
B(5, );
#undef B
+
+// CHECK-LABEL: define{{.*}} void @_Z6f_attrv
+// CHECK: call {{.*}} @_ZN1XC1Ev
+// CHECK-NEXT: call void @llvm.lifetime.end
+// CHECK-NEXT: ret void
+template<class T = X> [[gnu::cdecl]] static inline auto tf_attr() -> X {
+ T t;
+ return t;
+}
+void f_attr() { auto t = tf_attr(); }
+
+// CHECK-LABEL: define{{.*}} void @_Z6b_attrv
+// CHECK: call {{.*}} @_ZN1XC1Ev
+// CHECK-NEXT: call void @llvm.lifetime.end
+// CHECK-NEXT: ret void
+void b_attr() {
+ auto t = []<class T = X>() {
+ return ^X() [[clang::vectorcall]] {
+ T t;
+ return t;
+ };
+ }()();
+}
diff --git a/clang/test/SemaObjCXX/block-capture.mm b/clang/test/SemaObjCXX/block-capture.mm
new file mode 100644
index 0000000000000..c2d7967747d88
--- /dev/null
+++ b/clang/test/SemaObjCXX/block-capture.mm
@@ -0,0 +1,66 @@
+// RUN: %clang_cc1 -std=c++20 -fsyntax-only -fobjc-arc -fblocks -verify=cxx98_20,cxx20 %s
+// RUN: %clang_cc1 -std=c++11 -fsyntax-only -fobjc-arc -fblocks -verify=cxx98_20,cxx98_11 %s
+// RUN: %clang_cc1 -std=c++98 -fsyntax-only -fobjc-arc -fblocks -Wno-c++11-extensions -verify=cxx98_20,cxx98_11 %s
+
+#define TEST(T) void test_##T() { \
+ __block T x; \
+ (void)^(void) { (void)x; }; \
+}
+
+struct CopyOnly {
+ CopyOnly();
+ CopyOnly(CopyOnly &);
+};
+TEST(CopyOnly);
+
+struct CopyNoMove {
+ CopyNoMove();
+ CopyNoMove(CopyNoMove &);
+ CopyNoMove(CopyNoMove &&) = delete; // cxx98_20-note {{marked deleted here}}
+};
+TEST(CopyNoMove); // cxx98_20-error {{call to deleted constructor}}
+
+struct MoveOnly {
+ MoveOnly();
+ MoveOnly(MoveOnly &) = delete;
+ MoveOnly(MoveOnly &&);
+};
+TEST(MoveOnly);
+
+struct NoCopyNoMove {
+ NoCopyNoMove();
+ NoCopyNoMove(NoCopyNoMove &) = delete;
+ NoCopyNoMove(NoCopyNoMove &&) = delete; // cxx98_20-note {{marked deleted here}}
+};
+TEST(NoCopyNoMove); // cxx98_20-error {{call to deleted constructor}}
+
+struct ConvertingRVRef {
+ ConvertingRVRef();
+ ConvertingRVRef(ConvertingRVRef &) = delete; // cxx98_11-note {{marked deleted here}}
+
+ struct X {};
+ ConvertingRVRef(X &&);
+ operator X() const & = delete;
+ operator X() &&;
+};
+TEST(ConvertingRVRef); // cxx98_11-error {{call to deleted constructor}}
+
+struct ConvertingCLVRef {
+ ConvertingCLVRef();
+ ConvertingCLVRef(ConvertingCLVRef &);
+
+ struct X {};
+ ConvertingCLVRef(X &&); // cxx20-note {{passing argument to parameter here}}
+ operator X() const &;
+ operator X() && = delete; // cxx20-note {{marked deleted here}}
+};
+TEST(ConvertingCLVRef); // cxx20-error {{invokes a deleted function}}
+
+struct SubSubMove {};
+struct SubMove : SubSubMove {
+ SubMove();
+ SubMove(SubMove &) = delete; // cxx98_11-note {{marked deleted here}}
+
+ SubMove(SubSubMove &&);
+};
+TEST(SubMove); // cxx98_11-error {{call to deleted constructor}}
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