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[Clang] No longer require complete types with __builtin_launder #91070

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[Clang] No longer require complete types with __builtin_launder #91070

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2 changes: 2 additions & 0 deletions clang/docs/ReleaseNotes.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -552,6 +552,8 @@ Bug Fixes in This Version
- Clang will no longer emit a duplicate -Wunused-value warning for an expression
`(A, B)` which evaluates to glvalue `B` that can be converted to non ODR-use. (#GH45783)

- `__builtin_launder` no longer requires a pointer to a complete type. (#GH90949)

Bug Fixes to Compiler Builtins
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

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5 changes: 3 additions & 2 deletions clang/lib/CodeGen/CGBuiltin.cpp
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Expand Up @@ -2487,8 +2487,9 @@ TypeRequiresBuiltinLaunderImp(const ASTContext &Ctx, QualType Ty,
if (!Seen.insert(Record).second)
return false;

assert(Record->hasDefinition() &&
"Incomplete types should already be diagnosed");
// Assume incomplete types need to be laundered
if (!Record->hasDefinition())
return true;

if (Record->isDynamicClass())
return true;
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21 changes: 2 additions & 19 deletions clang/lib/Sema/SemaChecking.cpp
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Expand Up @@ -2164,15 +2164,8 @@ static ExprResult BuiltinLaunder(Sema &S, CallExpr *TheCall) {
// * The type of the argument if it's not an array or function type,
// Otherwise,
// * The decayed argument type.
QualType ParamTy = [&]() {
QualType ArgTy = TheCall->getArg(0)->getType();
if (const ArrayType *Ty = ArgTy->getAsArrayTypeUnsafe())
return S.Context.getPointerType(Ty->getElementType());
if (ArgTy->isFunctionType()) {
return S.Context.getPointerType(ArgTy);
}
return ArgTy;
}();
QualType ParamTy =
S.Context.getAdjustedParameterType(TheCall->getArg(0)->getType());

TheCall->setType(ParamTy);

Expand All @@ -2191,16 +2184,6 @@ static ExprResult BuiltinLaunder(Sema &S, CallExpr *TheCall) {
return ExprError();
}

// We either have an incomplete class type, or we have a class template
// whose instantiation has not been forced. Example:
//
// template <class T> struct Foo { T value; };
// Foo<int> *p = nullptr;
// auto *d = __builtin_launder(p);
if (S.RequireCompleteType(TheCall->getBeginLoc(), ParamTy->getPointeeType(),
diag::err_incomplete_type))
return ExprError();

assert(ParamTy->getPointeeType()->isObjectType() &&
"Unhandled non-object pointer case");

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14 changes: 11 additions & 3 deletions clang/test/AST/Interp/builtin-functions.cpp
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Expand Up @@ -457,16 +457,24 @@ void f() {
static_assert(test_in_constexpr(i), "");
}

struct Incomplete; // both-note {{forward declaration}}
struct Incomplete;
struct IncompleteMember {
Incomplete &i;
};
void test_incomplete(Incomplete *i, IncompleteMember *im) {
// both-error@+1 {{incomplete type 'Incomplete' where a complete type is required}}
__builtin_launder(i);
__builtin_launder(i); // OK
__builtin_launder(&i); // OK
__builtin_launder(im); // OK
}
extern Incomplete incomplete;
extern IncompleteMember incomplete_member;
static_assert(test_constexpr_launder(&incomplete) == &incomplete, "");
static_assert(test_constexpr_launder(&incomplete_member) == &incomplete_member, "");
template<typename> struct X { static_assert(false, ""); };
extern X<void> x;
static_assert(__builtin_launder(__builtin_addressof(x)) == __builtin_addressof(x), "");
static_assert((test_constexpr_launder)(__builtin_addressof(x)) == __builtin_addressof(x), "");
template<> struct X<void> {};

void test_noexcept(int *i) {
static_assert(noexcept(__builtin_launder(i)), "");
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56 changes: 56 additions & 0 deletions clang/test/CodeGenCXX/builtin-launder.cpp
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Expand Up @@ -53,10 +53,66 @@ extern "C" void test_builtin_launder_virtual_base(TestVirtualBase *p) {
TestVirtualBase *d = __builtin_launder(p);
}

struct IncompleteNeedsLaunder;

// CHECK-LABEL: define{{.*}} void @test_builtin_launder_incomplete_later_needs_launder
extern "C" void test_builtin_launder_incomplete_later_needs_launder(IncompleteNeedsLaunder *p) {
// CHECK-STRICT-NOT: ret void
// CHECK-STRICT: @llvm.launder.invariant.group

// CHECK-NONSTRICT-NOT: @llvm.launder.invariant.group

// CHECK: ret void
IncompleteNeedsLaunder *d = __builtin_launder(p);
}

struct IncompleteNeedsLaunder {
virtual void foo() {}
};

// CHECK-LABEL: define{{.*}} void @test_builtin_launder_completed_needs_launder
extern "C" void test_builtin_launder_completed_needs_launder(IncompleteNeedsLaunder *p) {
// CHECK-STRICT-NOT: ret void
// CHECK-STRICT: @llvm.launder.invariant.group

// CHECK-NONSTRICT-NOT: @llvm.launder.invariant.group

// CHECK: ret void
IncompleteNeedsLaunder *d = __builtin_launder(p);
}

struct IncompleteDoesntNeedLaunder;

// CHECK-LABEL: define{{.*}} void @test_builtin_launder_incomplete_later_doesnt_needs_launder
extern "C" void test_builtin_launder_incomplete_later_doesnt_needs_launder(IncompleteDoesntNeedLaunder *p) {
// CHECK-STRICT-NOT: ret void
// CHECK-STRICT: @llvm.launder.invariant.group

// CHECK-NONSTRICT-NOT: @llvm.launder.invariant.group

// CHECK: ret void
IncompleteDoesntNeedLaunder *d = __builtin_launder(p);
}

//===----------------------------------------------------------------------===//
// Negative Cases
//===----------------------------------------------------------------------===//

struct IncompleteDoesntNeedLaunder {};

// CHECK-LABEL: define{{.*}} void @test_builtin_launder_completed_doesnt_need_launder
extern "C" void test_builtin_launder_completed_doesnt_need_launder(IncompleteDoesntNeedLaunder *p) {
// CHECK: entry
// CHECK-NOT: llvm.launder.invariant.group
// CHECK-NEXT: %p.addr = alloca ptr, align 8
// CHECK-NEXT: %d = alloca ptr
// CHECK-NEXT: store ptr %p, ptr %p.addr
// CHECK-NEXT: [[TMP:%.*]] = load ptr, ptr %p.addr
// CHECK-NEXT: store ptr [[TMP]], ptr %d
// CHECK-NEXT: ret void
IncompleteDoesntNeedLaunder *d = __builtin_launder(p);
}

// CHECK-LABEL: define{{.*}} void @test_builtin_launder_ommitted_one
extern "C" void test_builtin_launder_ommitted_one(int *p) {
// CHECK: entry
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14 changes: 11 additions & 3 deletions clang/test/SemaCXX/builtins.cpp
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Expand Up @@ -144,16 +144,24 @@ void f() {
static_assert(test_in_constexpr(i), "");
}

struct Incomplete; // expected-note {{forward declaration}}
struct Incomplete;
struct IncompleteMember {
Incomplete &i;
};
void test_incomplete(Incomplete *i, IncompleteMember *im) {
// expected-error@+1 {{incomplete type 'Incomplete' where a complete type is required}}
__builtin_launder(i);
__builtin_launder(i); // OK
__builtin_launder(&i); // OK
__builtin_launder(im); // OK
}
extern Incomplete incomplete;
extern IncompleteMember incomplete_member;
static_assert(test_constexpr_launder(&incomplete) == &incomplete, "");
static_assert(test_constexpr_launder(&incomplete_member) == &incomplete_member, "");
template<typename> struct X { static_assert(false, ""); };
extern X<void> x;
static_assert(__builtin_launder(__builtin_addressof(x)) == __builtin_addressof(x), "");
static_assert((test_constexpr_launder)(__builtin_addressof(x)) == __builtin_addressof(x), "");
template<> struct X<void> {};

void test_noexcept(int *i) {
static_assert(noexcept(__builtin_launder(i)), "");
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