PR19668, PR23034: Fix handling of move constructors and deleted copy
constructors when deciding whether classes should be passed indirectly.
This fixes ABI differences between Clang and GCC:
* Previously, Clang ignored the move constructor when making this
determination. It now takes the move constructor into account, per
https://github.com/itanium-cxx-abi/cxx-abi/pull/17 (this change may
seem recent, but the ABI change was agreed on the Itanium C++ ABI
list a long time ago).
* Previously, Clang's behavior when the copy constructor was deleted
was unstable -- depending on whether the lazy declaration of the
copy constructor had been triggered, you might get different behavior.
We now eagerly declare the copy constructor whenever its deletedness
is unclear, and ignore deleted copy/move constructors when looking for
a trivial such constructor.
This also fixes an ABI difference between Clang and MSVC:
* If the copy constructor would be implicitly deleted (but has not been
lazily declared yet), for instance because the class has an rvalue
reference member, we would pass it directly. We now pass such a class
indirectly, matching MSVC.
Based on a patch by Vassil Vassilev, which was based on a patch by Bernd
Schmidt, which was based on a patch by Reid Kleckner!
This is a re-commit of r310401, which was reverted in r310464 due to ARM
failures (which should now be fixed).
llvm-svn: 310983
diff --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
index 6e33b98..2c0bb11 100644
--- a/clang/lib/AST/ASTImporter.cpp
+++ b/clang/lib/AST/ASTImporter.cpp
@@ -956,12 +956,16 @@
ToData.HasUninitializedFields = FromData.HasUninitializedFields;
ToData.HasInheritedConstructor = FromData.HasInheritedConstructor;
ToData.HasInheritedAssignment = FromData.HasInheritedAssignment;
+ ToData.NeedOverloadResolutionForCopyConstructor
+ = FromData.NeedOverloadResolutionForCopyConstructor;
ToData.NeedOverloadResolutionForMoveConstructor
= FromData.NeedOverloadResolutionForMoveConstructor;
ToData.NeedOverloadResolutionForMoveAssignment
= FromData.NeedOverloadResolutionForMoveAssignment;
ToData.NeedOverloadResolutionForDestructor
= FromData.NeedOverloadResolutionForDestructor;
+ ToData.DefaultedCopyConstructorIsDeleted
+ = FromData.DefaultedCopyConstructorIsDeleted;
ToData.DefaultedMoveConstructorIsDeleted
= FromData.DefaultedMoveConstructorIsDeleted;
ToData.DefaultedMoveAssignmentIsDeleted
@@ -973,6 +977,7 @@
= FromData.HasConstexprNonCopyMoveConstructor;
ToData.HasDefaultedDefaultConstructor
= FromData.HasDefaultedDefaultConstructor;
+ ToData.CanPassInRegisters = FromData.CanPassInRegisters;
ToData.DefaultedDefaultConstructorIsConstexpr
= FromData.DefaultedDefaultConstructorIsConstexpr;
ToData.HasConstexprDefaultConstructor
diff --git a/clang/lib/AST/DeclCXX.cpp b/clang/lib/AST/DeclCXX.cpp
index 1caceab..5782b7b 100644
--- a/clang/lib/AST/DeclCXX.cpp
+++ b/clang/lib/AST/DeclCXX.cpp
@@ -55,15 +55,18 @@
HasOnlyCMembers(true), HasInClassInitializer(false),
HasUninitializedReferenceMember(false), HasUninitializedFields(false),
HasInheritedConstructor(false), HasInheritedAssignment(false),
+ NeedOverloadResolutionForCopyConstructor(false),
NeedOverloadResolutionForMoveConstructor(false),
NeedOverloadResolutionForMoveAssignment(false),
NeedOverloadResolutionForDestructor(false),
+ DefaultedCopyConstructorIsDeleted(false),
DefaultedMoveConstructorIsDeleted(false),
DefaultedMoveAssignmentIsDeleted(false),
DefaultedDestructorIsDeleted(false), HasTrivialSpecialMembers(SMF_All),
DeclaredNonTrivialSpecialMembers(0), HasIrrelevantDestructor(true),
HasConstexprNonCopyMoveConstructor(false),
HasDefaultedDefaultConstructor(false),
+ CanPassInRegisters(true),
DefaultedDefaultConstructorIsConstexpr(true),
HasConstexprDefaultConstructor(false),
HasNonLiteralTypeFieldsOrBases(false), ComputedVisibleConversions(false),
@@ -352,8 +355,10 @@
setHasVolatileMember(true);
// Keep track of the presence of mutable fields.
- if (BaseClassDecl->hasMutableFields())
+ if (BaseClassDecl->hasMutableFields()) {
data().HasMutableFields = true;
+ data().NeedOverloadResolutionForCopyConstructor = true;
+ }
if (BaseClassDecl->hasUninitializedReferenceMember())
data().HasUninitializedReferenceMember = true;
@@ -406,6 +411,8 @@
// -- a direct or virtual base class B that cannot be copied/moved [...]
// -- a non-static data member of class type M (or array thereof)
// that cannot be copied or moved [...]
+ if (!Subobj->hasSimpleCopyConstructor())
+ data().NeedOverloadResolutionForCopyConstructor = true;
if (!Subobj->hasSimpleMoveConstructor())
data().NeedOverloadResolutionForMoveConstructor = true;
@@ -426,6 +433,7 @@
// -- any non-static data member has a type with a destructor
// that is deleted or inaccessible from the defaulted [ctor or dtor].
if (!Subobj->hasSimpleDestructor()) {
+ data().NeedOverloadResolutionForCopyConstructor = true;
data().NeedOverloadResolutionForMoveConstructor = true;
data().NeedOverloadResolutionForDestructor = true;
}
@@ -711,8 +719,10 @@
data().IsStandardLayout = false;
// Keep track of the presence of mutable fields.
- if (Field->isMutable())
+ if (Field->isMutable()) {
data().HasMutableFields = true;
+ data().NeedOverloadResolutionForCopyConstructor = true;
+ }
// C++11 [class.union]p8, DR1460:
// If X is a union, a non-static data member of X that is not an anonymous
@@ -756,6 +766,12 @@
// A standard-layout class is a class that:
// -- has no non-static data members of type [...] reference,
data().IsStandardLayout = false;
+
+ // C++1z [class.copy.ctor]p10:
+ // A defaulted copy constructor for a class X is defined as deleted if X has:
+ // -- a non-static data member of rvalue reference type
+ if (T->isRValueReferenceType())
+ data().DefaultedCopyConstructorIsDeleted = true;
}
if (!Field->hasInClassInitializer() && !Field->isMutable()) {
@@ -809,6 +825,10 @@
// We may need to perform overload resolution to determine whether a
// field can be moved if it's const or volatile qualified.
if (T.getCVRQualifiers() & (Qualifiers::Const | Qualifiers::Volatile)) {
+ // We need to care about 'const' for the copy constructor because an
+ // implicit copy constructor might be declared with a non-const
+ // parameter.
+ data().NeedOverloadResolutionForCopyConstructor = true;
data().NeedOverloadResolutionForMoveConstructor = true;
data().NeedOverloadResolutionForMoveAssignment = true;
}
@@ -819,6 +839,8 @@
// -- X is a union-like class that has a variant member with a
// non-trivial [corresponding special member]
if (isUnion()) {
+ if (FieldRec->hasNonTrivialCopyConstructor())
+ data().DefaultedCopyConstructorIsDeleted = true;
if (FieldRec->hasNonTrivialMoveConstructor())
data().DefaultedMoveConstructorIsDeleted = true;
if (FieldRec->hasNonTrivialMoveAssignment())
@@ -830,6 +852,8 @@
// For an anonymous union member, our overload resolution will perform
// overload resolution for its members.
if (Field->isAnonymousStructOrUnion()) {
+ data().NeedOverloadResolutionForCopyConstructor |=
+ FieldRec->data().NeedOverloadResolutionForCopyConstructor;
data().NeedOverloadResolutionForMoveConstructor |=
FieldRec->data().NeedOverloadResolutionForMoveConstructor;
data().NeedOverloadResolutionForMoveAssignment |=
@@ -915,8 +939,10 @@
}
// Keep track of the presence of mutable fields.
- if (FieldRec->hasMutableFields())
+ if (FieldRec->hasMutableFields()) {
data().HasMutableFields = true;
+ data().NeedOverloadResolutionForCopyConstructor = true;
+ }
// C++11 [class.copy]p13:
// If the implicitly-defined constructor would satisfy the
@@ -1450,7 +1476,7 @@
void CXXRecordDecl::completeDefinition(CXXFinalOverriderMap *FinalOverriders) {
RecordDecl::completeDefinition();
-
+
// If the class may be abstract (but hasn't been marked as such), check for
// any pure final overriders.
if (mayBeAbstract()) {
diff --git a/clang/lib/CodeGen/CGCXXABI.cpp b/clang/lib/CodeGen/CGCXXABI.cpp
index e29e525..0332586 100644
--- a/clang/lib/CodeGen/CGCXXABI.cpp
+++ b/clang/lib/CodeGen/CGCXXABI.cpp
@@ -30,38 +30,9 @@
}
bool CGCXXABI::canCopyArgument(const CXXRecordDecl *RD) const {
- // If RD has a non-trivial move or copy constructor, we cannot copy the
- // argument.
- if (RD->hasNonTrivialCopyConstructor() || RD->hasNonTrivialMoveConstructor())
- return false;
-
- // If RD has a non-trivial destructor, we cannot copy the argument.
- if (RD->hasNonTrivialDestructor())
- return false;
-
// We can only copy the argument if there exists at least one trivial,
// non-deleted copy or move constructor.
- // FIXME: This assumes that all lazily declared copy and move constructors are
- // not deleted. This assumption might not be true in some corner cases.
- bool CopyDeleted = false;
- bool MoveDeleted = false;
- for (const CXXConstructorDecl *CD : RD->ctors()) {
- if (CD->isCopyConstructor() || CD->isMoveConstructor()) {
- assert(CD->isTrivial());
- // We had at least one undeleted trivial copy or move ctor. Return
- // directly.
- if (!CD->isDeleted())
- return true;
- if (CD->isCopyConstructor())
- CopyDeleted = true;
- else
- MoveDeleted = true;
- }
- }
-
- // If all trivial copy and move constructors are deleted, we cannot copy the
- // argument.
- return !(CopyDeleted && MoveDeleted);
+ return RD->canPassInRegisters();
}
llvm::Constant *CGCXXABI::GetBogusMemberPointer(QualType T) {
diff --git a/clang/lib/CodeGen/ItaniumCXXABI.cpp b/clang/lib/CodeGen/ItaniumCXXABI.cpp
index c1f892a..5c33f8c 100644
--- a/clang/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/clang/lib/CodeGen/ItaniumCXXABI.cpp
@@ -63,11 +63,8 @@
bool classifyReturnType(CGFunctionInfo &FI) const override;
RecordArgABI getRecordArgABI(const CXXRecordDecl *RD) const override {
- // Structures with either a non-trivial destructor or a non-trivial
- // copy constructor are always indirect.
- // FIXME: Use canCopyArgument() when it is fixed to handle lazily declared
- // special members.
- if (RD->hasNonTrivialDestructor() || RD->hasNonTrivialCopyConstructor())
+ // If C++ prohibits us from making a copy, pass by address.
+ if (!canCopyArgument(RD))
return RAA_Indirect;
return RAA_Default;
}
@@ -1014,10 +1011,8 @@
if (!RD)
return false;
- // Return indirectly if we have a non-trivial copy ctor or non-trivial dtor.
- // FIXME: Use canCopyArgument() when it is fixed to handle lazily declared
- // special members.
- if (RD->hasNonTrivialDestructor() || RD->hasNonTrivialCopyConstructor()) {
+ // If C++ prohibits us from making a copy, return by address.
+ if (!canCopyArgument(RD)) {
auto Align = CGM.getContext().getTypeAlignInChars(FI.getReturnType());
FI.getReturnInfo() = ABIArgInfo::getIndirect(Align, /*ByVal=*/false);
return true;
diff --git a/clang/lib/CodeGen/MicrosoftCXXABI.cpp b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
index 409bad7..0a3cc30 100644
--- a/clang/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -819,46 +819,44 @@
return RAA_Default;
case llvm::Triple::x86_64:
- // Win64 passes objects with non-trivial copy ctors indirectly.
- if (RD->hasNonTrivialCopyConstructor())
- return RAA_Indirect;
-
- // If an object has a destructor, we'd really like to pass it indirectly
+ // If a class has a destructor, we'd really like to pass it indirectly
// because it allows us to elide copies. Unfortunately, MSVC makes that
// impossible for small types, which it will pass in a single register or
// stack slot. Most objects with dtors are large-ish, so handle that early.
// We can't call out all large objects as being indirect because there are
// multiple x64 calling conventions and the C++ ABI code shouldn't dictate
// how we pass large POD types.
+ //
+ // Note: This permits small classes with nontrivial destructors to be
+ // passed in registers, which is non-conforming.
if (RD->hasNonTrivialDestructor() &&
getContext().getTypeSize(RD->getTypeForDecl()) > 64)
return RAA_Indirect;
- // If this is true, the implicit copy constructor that Sema would have
- // created would not be deleted. FIXME: We should provide a more direct way
- // for CodeGen to ask whether the constructor was deleted.
- if (!RD->hasUserDeclaredCopyConstructor() &&
- !RD->hasUserDeclaredMoveConstructor() &&
- !RD->needsOverloadResolutionForMoveConstructor() &&
- !RD->hasUserDeclaredMoveAssignment() &&
- !RD->needsOverloadResolutionForMoveAssignment())
- return RAA_Default;
-
- // Otherwise, Sema should have created an implicit copy constructor if
- // needed.
- assert(!RD->needsImplicitCopyConstructor());
-
- // We have to make sure the trivial copy constructor isn't deleted.
- for (const CXXConstructorDecl *CD : RD->ctors()) {
- if (CD->isCopyConstructor()) {
- assert(CD->isTrivial());
- // We had at least one undeleted trivial copy ctor. Return directly.
- if (!CD->isDeleted())
- return RAA_Default;
+ // If a class has at least one non-deleted, trivial copy constructor, it
+ // is passed according to the C ABI. Otherwise, it is passed indirectly.
+ //
+ // Note: This permits classes with non-trivial copy or move ctors to be
+ // passed in registers, so long as they *also* have a trivial copy ctor,
+ // which is non-conforming.
+ if (RD->needsImplicitCopyConstructor()) {
+ // If the copy ctor has not yet been declared, we can read its triviality
+ // off the AST.
+ if (!RD->defaultedCopyConstructorIsDeleted() &&
+ RD->hasTrivialCopyConstructor())
+ return RAA_Default;
+ } else {
+ // Otherwise, we need to find the copy constructor(s) and ask.
+ for (const CXXConstructorDecl *CD : RD->ctors()) {
+ if (CD->isCopyConstructor()) {
+ // We had at least one nondeleted trivial copy ctor. Return directly.
+ if (!CD->isDeleted() && CD->isTrivial())
+ return RAA_Default;
+ }
}
}
- // The trivial copy constructor was deleted. Return indirectly.
+ // We have no trivial, non-deleted copy constructor.
return RAA_Indirect;
}
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index e907088..c05e5f0 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -5726,6 +5726,53 @@
}
}
+/// Determine whether a type is permitted to be passed or returned in
+/// registers, per C++ [class.temporary]p3.
+static bool computeCanPassInRegisters(Sema &S, CXXRecordDecl *D) {
+ if (D->isDependentType() || D->isInvalidDecl())
+ return false;
+
+ // Per C++ [class.temporary]p3, the relevant condition is:
+ // each copy constructor, move constructor, and destructor of X is
+ // either trivial or deleted, and X has at least one non-deleted copy
+ // or move constructor
+ bool HasNonDeletedCopyOrMove = false;
+
+ if (D->needsImplicitCopyConstructor() &&
+ !D->defaultedCopyConstructorIsDeleted()) {
+ if (!D->hasTrivialCopyConstructor())
+ return false;
+ HasNonDeletedCopyOrMove = true;
+ }
+
+ if (S.getLangOpts().CPlusPlus11 && D->needsImplicitMoveConstructor() &&
+ !D->defaultedMoveConstructorIsDeleted()) {
+ if (!D->hasTrivialMoveConstructor())
+ return false;
+ HasNonDeletedCopyOrMove = true;
+ }
+
+ if (D->needsImplicitDestructor() && !D->defaultedDestructorIsDeleted() &&
+ !D->hasTrivialDestructor())
+ return false;
+
+ for (const CXXMethodDecl *MD : D->methods()) {
+ if (MD->isDeleted())
+ continue;
+
+ auto *CD = dyn_cast<CXXConstructorDecl>(MD);
+ if (CD && CD->isCopyOrMoveConstructor())
+ HasNonDeletedCopyOrMove = true;
+ else if (!isa<CXXDestructorDecl>(MD))
+ continue;
+
+ if (!MD->isTrivial())
+ return false;
+ }
+
+ return HasNonDeletedCopyOrMove;
+}
+
/// \brief Perform semantic checks on a class definition that has been
/// completing, introducing implicitly-declared members, checking for
/// abstract types, etc.
@@ -5870,6 +5917,8 @@
}
checkClassLevelDLLAttribute(Record);
+
+ Record->setCanPassInRegisters(computeCanPassInRegisters(*this, Record));
}
/// Look up the special member function that would be called by a special
@@ -7496,8 +7545,7 @@
reinterpret_cast<Decl**>(FieldCollector->getCurFields()),
FieldCollector->getCurNumFields()), LBrac, RBrac, AttrList);
- CheckCompletedCXXClass(
- dyn_cast_or_null<CXXRecordDecl>(TagDecl));
+ CheckCompletedCXXClass(dyn_cast_or_null<CXXRecordDecl>(TagDecl));
}
/// AddImplicitlyDeclaredMembersToClass - Adds any implicitly-declared
@@ -11929,8 +11977,10 @@
Scope *S = getScopeForContext(ClassDecl);
CheckImplicitSpecialMemberDeclaration(S, CopyConstructor);
- if (ShouldDeleteSpecialMember(CopyConstructor, CXXCopyConstructor))
+ if (ShouldDeleteSpecialMember(CopyConstructor, CXXCopyConstructor)) {
+ ClassDecl->setImplicitCopyConstructorIsDeleted();
SetDeclDeleted(CopyConstructor, ClassLoc);
+ }
if (S)
PushOnScopeChains(CopyConstructor, S, false);
diff --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index abed258..0853415 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -1559,9 +1559,11 @@
Data.HasUninitializedFields = Record.readInt();
Data.HasInheritedConstructor = Record.readInt();
Data.HasInheritedAssignment = Record.readInt();
+ Data.NeedOverloadResolutionForCopyConstructor = Record.readInt();
Data.NeedOverloadResolutionForMoveConstructor = Record.readInt();
Data.NeedOverloadResolutionForMoveAssignment = Record.readInt();
Data.NeedOverloadResolutionForDestructor = Record.readInt();
+ Data.DefaultedCopyConstructorIsDeleted = Record.readInt();
Data.DefaultedMoveConstructorIsDeleted = Record.readInt();
Data.DefaultedMoveAssignmentIsDeleted = Record.readInt();
Data.DefaultedDestructorIsDeleted = Record.readInt();
@@ -1570,6 +1572,7 @@
Data.HasIrrelevantDestructor = Record.readInt();
Data.HasConstexprNonCopyMoveConstructor = Record.readInt();
Data.HasDefaultedDefaultConstructor = Record.readInt();
+ Data.CanPassInRegisters = Record.readInt();
Data.DefaultedDefaultConstructorIsConstexpr = Record.readInt();
Data.HasConstexprDefaultConstructor = Record.readInt();
Data.HasNonLiteralTypeFieldsOrBases = Record.readInt();
@@ -1697,9 +1700,11 @@
MATCH_FIELD(HasUninitializedFields)
MATCH_FIELD(HasInheritedConstructor)
MATCH_FIELD(HasInheritedAssignment)
+ MATCH_FIELD(NeedOverloadResolutionForCopyConstructor)
MATCH_FIELD(NeedOverloadResolutionForMoveConstructor)
MATCH_FIELD(NeedOverloadResolutionForMoveAssignment)
MATCH_FIELD(NeedOverloadResolutionForDestructor)
+ MATCH_FIELD(DefaultedCopyConstructorIsDeleted)
MATCH_FIELD(DefaultedMoveConstructorIsDeleted)
MATCH_FIELD(DefaultedMoveAssignmentIsDeleted)
MATCH_FIELD(DefaultedDestructorIsDeleted)
@@ -1708,6 +1713,7 @@
MATCH_FIELD(HasIrrelevantDestructor)
OR_FIELD(HasConstexprNonCopyMoveConstructor)
OR_FIELD(HasDefaultedDefaultConstructor)
+ MATCH_FIELD(CanPassInRegisters)
MATCH_FIELD(DefaultedDefaultConstructorIsConstexpr)
OR_FIELD(HasConstexprDefaultConstructor)
MATCH_FIELD(HasNonLiteralTypeFieldsOrBases)
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 9a73957..62c9fb4 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -5875,9 +5875,11 @@
Record->push_back(Data.HasUninitializedFields);
Record->push_back(Data.HasInheritedConstructor);
Record->push_back(Data.HasInheritedAssignment);
+ Record->push_back(Data.NeedOverloadResolutionForCopyConstructor);
Record->push_back(Data.NeedOverloadResolutionForMoveConstructor);
Record->push_back(Data.NeedOverloadResolutionForMoveAssignment);
Record->push_back(Data.NeedOverloadResolutionForDestructor);
+ Record->push_back(Data.DefaultedCopyConstructorIsDeleted);
Record->push_back(Data.DefaultedMoveConstructorIsDeleted);
Record->push_back(Data.DefaultedMoveAssignmentIsDeleted);
Record->push_back(Data.DefaultedDestructorIsDeleted);
@@ -5886,6 +5888,7 @@
Record->push_back(Data.HasIrrelevantDestructor);
Record->push_back(Data.HasConstexprNonCopyMoveConstructor);
Record->push_back(Data.HasDefaultedDefaultConstructor);
+ Record->push_back(Data.CanPassInRegisters);
Record->push_back(Data.DefaultedDefaultConstructorIsConstexpr);
Record->push_back(Data.HasConstexprDefaultConstructor);
Record->push_back(Data.HasNonLiteralTypeFieldsOrBases);