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PR23373: A defaulted union copy constructor that is not trivial must still be 

emitted as a memcpy.

llvm-svn: 236142
This commit is contained in:
Richard Smith 2015-04-29 19:26:57 +00:00
parent ae7e4995ca
commit 419bd09415
6 changed files with 72 additions and 36 deletions
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11
clang/lib/AST/ExprConstant.cpp
View File

@ -3727,8 +3727,9 @@ static bool HandleFunctionCall(SourceLocation CallLoc,
// Skip this for non-union classes with no fields; in that case, the defaulted
// copy/move does not actually read the object.
const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(Callee);
if (MD && MD->isDefaulted() && MD->isTrivial() &&
(MD->getParent()->isUnion() || hasFields(MD->getParent()))) {
if (MD && MD->isDefaulted() &&
(MD->getParent()->isUnion() ||
(MD->isTrivial() && hasFields(MD->getParent())))) {
assert(This &&
(MD->isCopyAssignmentOperator() || MD->isMoveAssignmentOperator()));
LValue RHS;
@ -3792,11 +3793,9 @@ static bool HandleConstructorCall(SourceLocation CallLoc, const LValue &This,
// Skip this for empty non-union classes; we should not perform an
// lvalue-to-rvalue conversion on them because their copy constructor does not
// actually read them.
if (Definition->isDefaulted() &&
((Definition->isCopyConstructor() && Definition->isTrivial()) ||
(Definition->isMoveConstructor() && Definition->isTrivial())) &&
if (Definition->isDefaulted() && Definition->isCopyOrMoveConstructor() &&
(Definition->getParent()->isUnion() ||
hasFields(Definition->getParent()))) {
(Definition->isTrivial() && hasFields(Definition->getParent())))) {
LValue RHS;
RHS.setFrom(Info.Ctx, ArgValues[0]);
return handleLValueToRValueConversion(Info, Args[0], Args[0]->getType(),

62
clang/lib/CodeGen/CGClass.cpp
View File

@ -540,6 +540,23 @@ static void EmitAggMemberInitializer(CodeGenFunction &CGF,
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 @@ static void EmitMemberInitializer(CodeGenFunction &CGF,
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 @@ namespace {
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 @@ namespace {
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 @@ void CodeGenFunction::EmitCXXConstructorCall(const CXXConstructorDecl *D,
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 @@ void CodeGenFunction::EmitCXXConstructorCall(const CXXConstructorDecl *D,
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 @@ void
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");

3
clang/lib/CodeGen/CGExprAgg.cpp
View File

@ -1415,7 +1415,8 @@ void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
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++.

2
clang/lib/CodeGen/CGExprCXX.cpp
View File

@ -173,7 +173,7 @@ RValue CodeGenFunction::EmitCXXMemberOrOperatorMemberCallExpr(
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())

8
clang/lib/Sema/SemaDeclCXX.cpp
View File

@ -10214,7 +10214,9 @@ void Sema::DefineImplicitCopyAssignment(SourceLocation CurrentLocation,
// Assign non-static members.
for (auto *Field : ClassDecl->fields()) {
if (Field->isUnnamedBitfield())
// FIXME: We should form some kind of AST representation for the implied
// memcpy in a union copy operation.
if (Field->isUnnamedBitfield() || Field->getParent()->isUnion())
continue;
if (Field->isInvalidDecl()) {
@ -10644,7 +10646,9 @@ void Sema::DefineImplicitMoveAssignment(SourceLocation CurrentLocation,
// Assign non-static members.
for (auto *Field : ClassDecl->fields()) {
if (Field->isUnnamedBitfield())
// FIXME: We should form some kind of AST representation for the implied
// memcpy in a union copy operation.
if (Field->isUnnamedBitfield() || Field->getParent()->isUnion())
continue;
if (Field->isInvalidDecl()) {

22
clang/test/CodeGenCXX/copy-constructor-synthesis-2.cpp
View File

@ -1,4 +1,24 @@
// RUN: %clang_cc1 -triple %itanium_abi_triple -emit-llvm -o - %s | FileCheck %s
// RUN: %clang_cc1 -triple %itanium_abi_triple -std=c++11 -emit-llvm -o - %s | FileCheck %s
union PR23373 {
PR23373(PR23373&) = default;
PR23373 &operator=(PR23373&) = default;
int n;
float f;
};
extern PR23373 pr23373_a;
PR23373 pr23373_b(pr23373_a);
// CHECK-LABEL: define {{.*}} @__cxx_global_var_init(
// CHECK: call void @llvm.memcpy.p0i8.p0i8.i64({{.*}} @pr23373_b{{.*}}, {{.*}} @pr23373_a{{.*}}, i64 4, i32 4, i1 false)
PR23373 pr23373_f() { return pr23373_a; }
// CHECK-LABEL: define {{.*}} @_Z9pr23373_fv(
// CHECK: call void @llvm.memcpy.p0i8.p0i8.i64({{.*}}, i64 4, i32 4, i1 false)
void pr23373_g(PR23373 &a, PR23373 &b) { a = b; }
// CHECK-LABEL: define {{.*}} @_Z9pr23373_g
// CHECK: call void @llvm.memcpy.p0i8.p0i8.i64({{.*}}, i64 4, i32 4, i1 false)
struct A { virtual void a(); };
A x(A& y) { return y; }