PR23373: A defaulted union copy constructor that is not trivial must still be
emitted as a memcpy.
llvm-svn: 236142
diff --git a/clang/lib/CodeGen/CGClass.cpp b/clang/lib/CodeGen/CGClass.cpp
index e3d4601..1d63512 100644
--- a/clang/lib/CodeGen/CGClass.cpp
+++ b/clang/lib/CodeGen/CGClass.cpp
@@ -540,6 +540,23 @@
CGF.EmitBlock(AfterFor, true);
}
+static bool isMemcpyEquivalentSpecialMember(const CXXMethodDecl *D) {
+ auto *CD = dyn_cast<CXXConstructorDecl>(D);
+ if (!(CD && CD->isCopyOrMoveConstructor()) &&
+ !D->isCopyAssignmentOperator() && !D->isMoveAssignmentOperator())
+ return false;
+
+ // We can emit a memcpy for a trivial copy or move constructor/assignment.
+ if (D->isTrivial() && !D->getParent()->mayInsertExtraPadding())
+ return true;
+
+ // We *must* emit a memcpy for a defaulted union copy or move op.
+ if (D->getParent()->isUnion() && D->isDefaulted())
+ return true;
+
+ return false;
+}
+
static void EmitMemberInitializer(CodeGenFunction &CGF,
const CXXRecordDecl *ClassDecl,
CXXCtorInitializer *MemberInit,
@@ -581,7 +598,7 @@
QualType BaseElementTy = CGF.getContext().getBaseElementType(Array);
CXXConstructExpr *CE = dyn_cast<CXXConstructExpr>(MemberInit->getInit());
if (BaseElementTy.isPODType(CGF.getContext()) ||
- (CE && CE->getConstructor()->isTrivial())) {
+ (CE && isMemcpyEquivalentSpecialMember(CE->getConstructor()))) {
unsigned SrcArgIndex =
CGF.CGM.getCXXABI().getSrcArgforCopyCtor(Constructor, Args);
llvm::Value *SrcPtr
@@ -1021,8 +1038,8 @@
QualType FieldType = Field->getType();
CXXConstructExpr *CE = dyn_cast<CXXConstructExpr>(MemberInit->getInit());
- // Bail out on non-POD, not-trivially-constructable members.
- if (!(CE && CE->getConstructor()->isTrivial()) &&
+ // Bail out on non-memcpyable, not-trivially-copyable members.
+ if (!(CE && isMemcpyEquivalentSpecialMember(CE->getConstructor())) &&
!(FieldType.isTriviallyCopyableType(CGF.getContext()) ||
FieldType->isReferenceType()))
return false;
@@ -1127,9 +1144,7 @@
return Field;
} else if (CXXMemberCallExpr *MCE = dyn_cast<CXXMemberCallExpr>(S)) {
CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(MCE->getCalleeDecl());
- if (!(MD && (MD->isCopyAssignmentOperator() ||
- MD->isMoveAssignmentOperator()) &&
- MD->isTrivial()))
+ if (!(MD && isMemcpyEquivalentSpecialMember(MD)))
return nullptr;
MemberExpr *IOA = dyn_cast<MemberExpr>(MCE->getImplicitObjectArgument());
if (!IOA)
@@ -1732,18 +1747,23 @@
bool ForVirtualBase,
bool Delegating, llvm::Value *This,
const CXXConstructExpr *E) {
- // If this is a trivial constructor, just emit what's needed.
- if (D->isTrivial() && !D->getParent()->mayInsertExtraPadding()) {
- if (E->getNumArgs() == 0) {
- // Trivial default constructor, no codegen required.
- assert(D->isDefaultConstructor() &&
- "trivial 0-arg ctor not a default ctor");
- return;
- }
+ // C++11 [class.mfct.non-static]p2:
+ // If a non-static member function of a class X is called for an object that
+ // is not of type X, or of a type derived from X, the behavior is undefined.
+ // FIXME: Provide a source location here.
+ EmitTypeCheck(CodeGenFunction::TCK_ConstructorCall, SourceLocation(), This,
+ getContext().getRecordType(D->getParent()));
+ if (D->isTrivial() && D->isDefaultConstructor()) {
+ assert(E->getNumArgs() == 0 && "trivial default ctor with args");
+ return;
+ }
+
+ // If this is a trivial constructor, just emit what's needed. If this is a
+ // union copy constructor, we must emit a memcpy, because the AST does not
+ // model that copy.
+ if (isMemcpyEquivalentSpecialMember(D)) {
assert(E->getNumArgs() == 1 && "unexpected argcount for trivial ctor");
- assert(D->isCopyOrMoveConstructor() &&
- "trivial 1-arg ctor not a copy/move ctor");
const Expr *Arg = E->getArg(0);
QualType SrcTy = Arg->getType();
@@ -1753,13 +1773,6 @@
return;
}
- // C++11 [class.mfct.non-static]p2:
- // If a non-static member function of a class X is called for an object that
- // is not of type X, or of a type derived from X, the behavior is undefined.
- // FIXME: Provide a source location here.
- EmitTypeCheck(CodeGenFunction::TCK_ConstructorCall, SourceLocation(), This,
- getContext().getRecordType(D->getParent()));
-
CallArgList Args;
// Push the this ptr.
@@ -1784,8 +1797,7 @@
CodeGenFunction::EmitSynthesizedCXXCopyCtorCall(const CXXConstructorDecl *D,
llvm::Value *This, llvm::Value *Src,
const CXXConstructExpr *E) {
- if (D->isTrivial() &&
- !D->getParent()->mayInsertExtraPadding()) {
+ if (isMemcpyEquivalentSpecialMember(D)) {
assert(E->getNumArgs() == 1 && "unexpected argcount for trivial ctor");
assert(D->isCopyOrMoveConstructor() &&
"trivial 1-arg ctor not a copy/move ctor");
diff --git a/clang/lib/CodeGen/CGExprAgg.cpp b/clang/lib/CodeGen/CGExprAgg.cpp
index b139ef2..2ad5ec3 100644
--- a/clang/lib/CodeGen/CGExprAgg.cpp
+++ b/clang/lib/CodeGen/CGExprAgg.cpp
@@ -1415,7 +1415,8 @@
assert((Record->hasTrivialCopyConstructor() ||
Record->hasTrivialCopyAssignment() ||
Record->hasTrivialMoveConstructor() ||
- Record->hasTrivialMoveAssignment()) &&
+ Record->hasTrivialMoveAssignment() ||
+ Record->isUnion()) &&
"Trying to aggregate-copy a type without a trivial copy/move "
"constructor or assignment operator");
// Ignore empty classes in C++.
diff --git a/clang/lib/CodeGen/CGExprCXX.cpp b/clang/lib/CodeGen/CGExprCXX.cpp
index 4bffad3..c4f509a 100644
--- a/clang/lib/CodeGen/CGExprCXX.cpp
+++ b/clang/lib/CodeGen/CGExprCXX.cpp
@@ -173,7 +173,7 @@
This = EmitLValue(Base).getAddress();
- if (MD->isTrivial()) {
+ if (MD->isTrivial() || (MD->isDefaulted() && MD->getParent()->isUnion())) {
if (isa<CXXDestructorDecl>(MD)) return RValue::get(nullptr);
if (isa<CXXConstructorDecl>(MD) &&
cast<CXXConstructorDecl>(MD)->isDefaultConstructor())