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[Clang] Add noalias to this pointer in C++ constructors #136792

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[Clang] Add noalias to this pointer in C++ constructors #136792

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79ca26a
[Clang] Add `noalias` to `this` pointer in C++ constructors
guy-david Apr 22, 2025
5098103
Automatically updated tests
guy-david Apr 22, 2025
d8ad192
Manually fixed tests
guy-david Apr 22, 2025
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9 changes: 7 additions & 2 deletions clang/lib/CodeGen/CGCall.cpp
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Expand Up @@ -2731,8 +2731,8 @@ void CodeGenModule::ConstructAttributeList(StringRef Name,
llvm::AttributeSet::get(getLLVMContext(), Attrs);
}

// Apply `nonnull`, `dereferenceable(N)` and `align N` to the `this` argument,
// unless this is a thunk function.
// Apply `nonnull`, `dereferenceable(N)`, `align N` (and `noalias` for
// constructors) to the `this` argument, unless this is a thunk function.
// FIXME: fix this properly, https://reviews.llvm.org/D100388
if (FI.isInstanceMethod() && !IRFunctionArgs.hasInallocaArg() &&
!FI.arg_begin()->type->isVoidPointerType() && !IsThunk) {
Expand All @@ -2744,6 +2744,11 @@ void CodeGenModule::ConstructAttributeList(StringRef Name,

QualType ThisTy = FI.arg_begin()->type.getTypePtr()->getPointeeType();

// According to [class.cdtor]/2, the value of the object is unspecified if
// its elements are accessed not through `this`.
if (isa_and_nonnull<CXXConstructorDecl>(TargetDecl))
Attrs.addAttribute(llvm::Attribute::NoAlias);

if (!CodeGenOpts.NullPointerIsValid &&
getTypes().getTargetAddressSpace(FI.arg_begin()->type) == 0) {
Attrs.addAttribute(llvm::Attribute::NonNull);
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2 changes: 1 addition & 1 deletion clang/test/CodeGen/attr-counted-by-pr88931.cpp
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Expand Up @@ -11,7 +11,7 @@ struct foo {
void init(void * __attribute__((pass_dynamic_object_size(0))));

// CHECK-LABEL: define dso_local void @_ZN3foo3barC1Ev(
// CHECK-SAME: ptr noundef nonnull align 4 dereferenceable(1) [[THIS:%.*]]) unnamed_addr #[[ATTR0:[0-9]+]] align 2 {
// CHECK-SAME: ptr noalias noundef nonnull align 4 dereferenceable(1) [[THIS:%.*]]) unnamed_addr #[[ATTR0:[0-9]+]] align 2 {
// CHECK-NEXT: entry:
// CHECK-NEXT: tail call void @_Z4initPvU25pass_dynamic_object_size0(ptr noundef nonnull align 4 dereferenceable(1) [[THIS]], i64 noundef -1) #[[ATTR2:[0-9]+]]
// CHECK-NEXT: ret void
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303 changes: 152 additions & 151 deletions clang/test/CodeGen/attr-noundef.cpp
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Expand Up @@ -10,157 +10,158 @@
// TODO: No structs may currently be marked noundef

namespace check_structs {
struct Trivial {
int a;
};
Trivial ret_trivial() { return {}; }
void pass_trivial(Trivial e) {}
// CHECK-INTEL: [[DEF:define( dso_local)?]] i32 @{{.*}}ret_trivial
// CHECK-AARCH: [[DEF:define( dso_local)?]] i32 @{{.*}}ret_trivial
// CHECK-INTEL: [[DEF]] void @{{.*}}pass_trivial{{.*}}(i32 %
// CHECK-AARCH: [[DEF]] void @{{.*}}pass_trivial{{.*}}(i64 %

struct NoCopy {
int a;
NoCopy(NoCopy &) = delete;
};
NoCopy ret_nocopy() { return {}; }
void pass_nocopy(NoCopy e) {}
// CHECK: [[DEF]] void @{{.*}}ret_nocopy{{.*}}(ptr dead_on_unwind noalias writable sret({{[^)]+}}) align 4 %
// CHECK: [[DEF]] void @{{.*}}pass_nocopy{{.*}}(ptr noundef %

struct Huge {
int a[1024];
};
Huge ret_huge() { return {}; }
void pass_huge(Huge h) {}
// CHECK: [[DEF]] void @{{.*}}ret_huge{{.*}}(ptr dead_on_unwind noalias writable sret({{[^)]+}}) align 4 %
// CHECK: [[DEF]] void @{{.*}}pass_huge{{.*}}(ptr noundef
} // namespace check_structs

//************ Passing unions by value
// No unions may be marked noundef

namespace check_unions {
union Trivial {
int a;
};
Trivial ret_trivial() { return {}; }
void pass_trivial(Trivial e) {}
// CHECK-INTEL: [[DEF]] i32 @{{.*}}ret_trivial
// CHECK-AARCH: [[DEF]] i32 @{{.*}}ret_trivial
// CHECK-INTEL: [[DEF]] void @{{.*}}pass_trivial{{.*}}(i32 %
// CHECK-AARCH: [[DEF]] void @{{.*}}pass_trivial{{.*}}(i64 %

union NoCopy {
int a;
NoCopy(NoCopy &) = delete;
};
NoCopy ret_nocopy() { return {}; }
void pass_nocopy(NoCopy e) {}
// CHECK: [[DEF]] void @{{.*}}ret_nocopy{{.*}}(ptr dead_on_unwind noalias writable sret({{[^)]+}}) align 4 %
// CHECK: [[DEF]] void @{{.*}}pass_nocopy{{.*}}(ptr noundef %
} // namespace check_unions

//************ Passing `this` pointers
// `this` pointer must always be defined

namespace check_this {
struct Object {
int data[];

Object() {
this->data[0] = 0;
struct Trivial {
int a;
};
Trivial ret_trivial() { return {}; }
void pass_trivial(Trivial e) {}
// CHECK-INTEL: [[DEF:define( dso_local)?]] i32 @{{.*}}ret_trivial
// CHECK-AARCH: [[DEF:define( dso_local)?]] i32 @{{.*}}ret_trivial
// CHECK-INTEL: [[DEF]] void @{{.*}}pass_trivial{{.*}}(i32 %
// CHECK-AARCH: [[DEF]] void @{{.*}}pass_trivial{{.*}}(i64 %

struct NoCopy {
int a;
NoCopy(NoCopy &) = delete;
};
NoCopy ret_nocopy() { return {}; }
void pass_nocopy(NoCopy e) {}
// CHECK: [[DEF]] void @{{.*}}ret_nocopy{{.*}}(ptr dead_on_unwind noalias writable sret({{[^)]+}}) align 4 %
// CHECK: [[DEF]] void @{{.*}}pass_nocopy{{.*}}(ptr noundef %

struct Huge {
int a[1024];
};
Huge ret_huge() { return {}; }
void pass_huge(Huge h) {}
// CHECK: [[DEF]] void @{{.*}}ret_huge{{.*}}(ptr dead_on_unwind noalias writable sret({{[^)]+}}) align 4 %
// CHECK: [[DEF]] void @{{.*}}pass_huge{{.*}}(ptr noundef
} // namespace check_structs

//************ Passing unions by value
// No unions may be marked noundef

namespace check_unions {
union Trivial {
int a;
};
Trivial ret_trivial() { return {}; }
void pass_trivial(Trivial e) {}
// CHECK-INTEL: [[DEF]] i32 @{{.*}}ret_trivial
// CHECK-AARCH: [[DEF]] i32 @{{.*}}ret_trivial
// CHECK-INTEL: [[DEF]] void @{{.*}}pass_trivial{{.*}}(i32 %
// CHECK-AARCH: [[DEF]] void @{{.*}}pass_trivial{{.*}}(i64 %

union NoCopy {
int a;
NoCopy(NoCopy &) = delete;
};
NoCopy ret_nocopy() { return {}; }
void pass_nocopy(NoCopy e) {}
// CHECK: [[DEF]] void @{{.*}}ret_nocopy{{.*}}(ptr dead_on_unwind noalias writable sret({{[^)]+}}) align 4 %
// CHECK: [[DEF]] void @{{.*}}pass_nocopy{{.*}}(ptr noundef %
} // namespace check_unions

//************ Passing `this` pointers
// `this` pointer must always be defined

namespace check_this {
struct Object {
int data[];

Object() {
this->data[0] = 0;
}
int getData() {
return this->data[0];
}
Object *getThis() {
return this;
}
};

void use_object() {
Object obj;
obj.getData();
obj.getThis();
}
int getData() {
return this->data[0];
// CHECK: define linkonce_odr void @{{.*}}Object{{.*}}(ptr noalias noundef nonnull align 4 dereferenceable(1) %
// CHECK: define linkonce_odr noundef i32 @{{.*}}Object{{.*}}getData{{.*}}(ptr noundef nonnull align 4 dereferenceable(1) %
// CHECK: define linkonce_odr noundef ptr @{{.*}}Object{{.*}}getThis{{.*}}(ptr noundef nonnull align 4 dereferenceable(1) %
} // namespace check_this

//************ Passing vector types

namespace check_vecs {
typedef int __attribute__((vector_size(12))) i32x3;
i32x3 ret_vec() {
return {};
}
Object *getThis() {
return this;
void pass_vec(i32x3 v) {
}
};

void use_object() {
Object obj;
obj.getData();
obj.getThis();
}
// CHECK: define linkonce_odr void @{{.*}}Object{{.*}}(ptr noundef nonnull align 4 dereferenceable(1) %
// CHECK: define linkonce_odr noundef i32 @{{.*}}Object{{.*}}getData{{.*}}(ptr noundef nonnull align 4 dereferenceable(1) %
// CHECK: define linkonce_odr noundef ptr @{{.*}}Object{{.*}}getThis{{.*}}(ptr noundef nonnull align 4 dereferenceable(1) %
} // namespace check_this

//************ Passing vector types

namespace check_vecs {
typedef int __attribute__((vector_size(12))) i32x3;
i32x3 ret_vec() {
return {};
}
void pass_vec(i32x3 v) {
}

// CHECK: [[DEF]] noundef <3 x i32> @{{.*}}ret_vec{{.*}}()
// CHECK-INTEL: [[DEF]] void @{{.*}}pass_vec{{.*}}(<3 x i32> noundef %
// CHECK-AARCH: [[DEF]] void @{{.*}}pass_vec{{.*}}(<4 x i32> %
} // namespace check_vecs

//************ Passing exotic types
// Function/Array pointers, Function member / Data member pointers, nullptr_t, ExtInt types

namespace check_exotic {
struct Object {
int mfunc();
int mdata;
};
typedef int Object::*mdptr;
typedef int (Object::*mfptr)();
typedef decltype(nullptr) nullptr_t;
typedef int (*arrptr)[32];
typedef int (*fnptr)(int);

arrptr ret_arrptr() {
return nullptr;
}
fnptr ret_fnptr() {
return nullptr;
}
mdptr ret_mdptr() {
return nullptr;
}
mfptr ret_mfptr() {
return nullptr;
}
nullptr_t ret_npt() {
return nullptr;
}
void pass_npt(nullptr_t t) {
}
_BitInt(3) ret_BitInt() {
return 0;
}
void pass_BitInt(_BitInt(3) e) {
}
void pass_large_BitInt(_BitInt(127) e) {
}

// Pointers to arrays/functions are always noundef
// CHECK: [[DEF]] noundef ptr @{{.*}}ret_arrptr{{.*}}()
// CHECK: [[DEF]] noundef ptr @{{.*}}ret_fnptr{{.*}}()

// Pointers to members are never noundef
// CHECK: [[DEF]] i64 @{{.*}}ret_mdptr{{.*}}()
// CHECK-INTEL: [[DEF]] { i64, i64 } @{{.*}}ret_mfptr{{.*}}()
// CHECK-AARCH: [[DEF]] [2 x i64] @{{.*}}ret_mfptr{{.*}}()

// nullptr_t is never noundef
// CHECK: [[DEF]] ptr @{{.*}}ret_npt{{.*}}()
// CHECK: [[DEF]] void @{{.*}}pass_npt{{.*}}(ptr %

// CHECK-INTEL: [[DEF]] noundef signext i3 @{{.*}}ret_BitInt{{.*}}()
// CHECK-AARCH: [[DEF]] noundef i3 @{{.*}}ret_BitInt{{.*}}()
// CHECK-INTEL: [[DEF]] void @{{.*}}pass_BitInt{{.*}}(i3 noundef signext %
// CHECK-AARCH: [[DEF]] void @{{.*}}pass_BitInt{{.*}}(i3 noundef %
// CHECK-INTEL: [[DEF]] void @{{.*}}pass_large_BitInt{{.*}}(i64 noundef %{{.*}}, i64 noundef %
// CHECK-AARCH: [[DEF]] void @{{.*}}pass_large_BitInt{{.*}}(i127 noundef %
} // namespace check_exotic

// CHECK: [[DEF]] noundef <3 x i32> @{{.*}}ret_vec{{.*}}()
// CHECK-INTEL: [[DEF]] void @{{.*}}pass_vec{{.*}}(<3 x i32> noundef %
// CHECK-AARCH: [[DEF]] void @{{.*}}pass_vec{{.*}}(<4 x i32> %
} // namespace check_vecs

//************ Passing exotic types
// Function/Array pointers, Function member / Data member pointers, nullptr_t, ExtInt types

namespace check_exotic {
struct Object {
int mfunc();
int mdata;
};
typedef int Object::*mdptr;
typedef int (Object::*mfptr)();
typedef decltype(nullptr) nullptr_t;
typedef int (*arrptr)[32];
typedef int (*fnptr)(int);

arrptr ret_arrptr() {
return nullptr;
}
fnptr ret_fnptr() {
return nullptr;
}
mdptr ret_mdptr() {
return nullptr;
}
mfptr ret_mfptr() {
return nullptr;
}
nullptr_t ret_npt() {
return nullptr;
}
void pass_npt(nullptr_t t) {
}
_BitInt(3) ret_BitInt() {
return 0;
}
void pass_BitInt(_BitInt(3) e) {
}
void pass_large_BitInt(_BitInt(127) e) {
}

// Pointers to arrays/functions are always noundef
// CHECK: [[DEF]] noundef ptr @{{.*}}ret_arrptr{{.*}}()
// CHECK: [[DEF]] noundef ptr @{{.*}}ret_fnptr{{.*}}()

// Pointers to members are never noundef
// CHECK: [[DEF]] i64 @{{.*}}ret_mdptr{{.*}}()
// CHECK-INTEL: [[DEF]] { i64, i64 } @{{.*}}ret_mfptr{{.*}}()
// CHECK-AARCH: [[DEF]] [2 x i64] @{{.*}}ret_mfptr{{.*}}()

// nullptr_t is never noundef
// CHECK: [[DEF]] ptr @{{.*}}ret_npt{{.*}}()
// CHECK: [[DEF]] void @{{.*}}pass_npt{{.*}}(ptr %

// CHECK-INTEL: [[DEF]] noundef signext i3 @{{.*}}ret_BitInt{{.*}}()
// CHECK-AARCH: [[DEF]] noundef i3 @{{.*}}ret_BitInt{{.*}}()
// CHECK-INTEL: [[DEF]] void @{{.*}}pass_BitInt{{.*}}(i3 noundef signext %
// CHECK-AARCH: [[DEF]] void @{{.*}}pass_BitInt{{.*}}(i3 noundef %
// CHECK-INTEL: [[DEF]] void @{{.*}}pass_large_BitInt{{.*}}(i64 noundef %{{.*}}, i64 noundef %
// CHECK-AARCH: [[DEF]] void @{{.*}}pass_large_BitInt{{.*}}(i127 noundef %
} // namespace check_exotic

8 changes: 4 additions & 4 deletions clang/test/CodeGen/paren-list-agg-init.cpp
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Expand Up @@ -390,9 +390,9 @@ namespace gh61145 {
// CHECK-NEXT: [[V:%.*v.*]] = alloca [[STRUCT_VEC]], align 1
// CHECK-NEXT: [[AGG_TMP_ENSURED:%.*agg.tmp.ensured.*]] = alloca [[STRUCT_S1]], align 1
// a.k.a. Vec::Vec()
// CHECK-NEXT: call void @_ZN7gh611453VecC1Ev(ptr noundef nonnull align 1 dereferenceable(1) [[V]])
// CHECK-NEXT: call void @_ZN7gh611453VecC1Ev(ptr noalias noundef nonnull align 1 dereferenceable(1) [[V]])
// a.k.a. Vec::Vec(Vec&&)
// CHECK-NEXT: call void @_ZN7gh611453VecC1EOS0_(ptr noundef nonnull align 1 dereferenceable(1) [[AGG_TMP_ENSURED]], ptr noundef nonnull align 1 dereferenceable(1) [[V]])
// CHECK-NEXT: call void @_ZN7gh611453VecC1EOS0_(ptr noalias noundef nonnull align 1 dereferenceable(1) [[AGG_TMP_ENSURED]], ptr noundef nonnull align 1 dereferenceable(1) [[V]])
// a.k.a. S1::~S1()
// CHECK-NEXT: call void @_ZN7gh611452S1D1Ev(ptr noundef nonnull align 1 dereferenceable(1) [[AGG_TMP_ENSURED]])
// a.k.a.Vec::~Vec()
Expand All @@ -410,9 +410,9 @@ namespace gh61145 {
// CHECK-NEXT: [[V:%.*v.*]] = alloca [[STRUCT_VEC]], align 1
// CHECK-NEXT: [[AGG_TMP_ENSURED:%.*agg.tmp.ensured.*]] = alloca [[STRUCT_S2]], align 1
// a.k.a. Vec::Vec()
// CHECK-NEXT: call void @_ZN7gh611453VecC1Ev(ptr noundef nonnull align 1 dereferenceable(1) [[V]])
// CHECK-NEXT: call void @_ZN7gh611453VecC1Ev(ptr noalias noundef nonnull align 1 dereferenceable(1) [[V]])
// a.k.a. Vec::Vec(Vec&&)
// CHECK-NEXT: call void @_ZN7gh611453VecC1EOS0_(ptr noundef nonnull align 1 dereferenceable(1) [[AGG_TMP_ENSURED]], ptr noundef nonnull align 1 dereferenceable(1) [[V]])
// CHECK-NEXT: call void @_ZN7gh611453VecC1EOS0_(ptr noalias noundef nonnull align 1 dereferenceable(1) [[AGG_TMP_ENSURED]], ptr noundef nonnull align 1 dereferenceable(1) [[V]])
// CHECK-NEXT: [[C:%.*c.*]] = getelementptr inbounds nuw [[STRUCT_S2]], ptr [[AGG_TMP_ENSURED]], i32 0, i32
// CHECK-NEXT: store i8 0, ptr [[C]], align 1
// a.k.a. S2::~S2()
Expand Down
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