Put noundef on all scalars that don't allow uninit

Previously, it was only put on scalars with range validity invariants
like bool, was uninit was obviously invalid for those.

Since then, we have normatively declared all uninit primitives to be
undefined behavior and can therefore put `noundef` on them.

The remaining concern was the `mem::uninitialized` function, which cause
quite a lot of UB in the older parts of the ecosystem. This function now
doesn't return uninit values anymore, making users of it safe from this
change.

The only real sources of UB where people could encounter uninit
primitives are `MaybeUninit::uninit().assume_init()`, which has always
be clear in the docs about being UB and from heap allocations (like
reading from the spare capacity of a vec. This is hopefully rare enough
to not break anything.

Author: Noratrieb

compiler/rustc_codegen_llvm/src/builder.rs

@@ -501,7 +501,7 @@ impl<'a, 'll, 'tcx> BuilderMethods<'a, 'tcx> for Builder<'a, 'll, 'tcx> {
             layout: TyAndLayout<'tcx>,
             offset: Size,
         ) {
-            if !scalar.is_always_valid(bx) {
+            if !scalar.is_uninit_valid() {
                 bx.noundef_metadata(load);
             }
 

compiler/rustc_ty_utils/src/abi.rs

@@ -220,7 +220,7 @@ fn adjust_for_rust_scalar<'tcx>(
     }
 
     // Scalars which have invalid values cannot be undef.
-    if !scalar.is_always_valid(&cx) {
+    if !scalar.is_uninit_valid() {
         attrs.set(ArgAttribute::NoUndef);
     }
 

tests/codegen/abi-sysv64.rs

@@ -15,7 +15,7 @@ trait Sized {}
 trait Copy {}
 impl Copy for i64 {}
 
-// CHECK: define x86_64_sysvcc i64 @has_sysv64_abi
+// CHECK: define x86_64_sysvcc noundef i64 @has_sysv64_abi
 #[no_mangle]
 pub extern "sysv64" fn has_sysv64_abi(a: i64) -> i64 {
     a

tests/codegen/abi-x86-interrupt.rs

@@ -15,7 +15,7 @@ trait Sized {}
 trait Copy {}
 impl Copy for i64 {}
 
-// CHECK: define x86_intrcc i64 @has_x86_interrupt_abi
+// CHECK: define x86_intrcc noundef i64 @has_x86_interrupt_abi
 #[no_mangle]
 pub extern "x86-interrupt" fn has_x86_interrupt_abi(a: i64) -> i64 {
     a

tests/codegen/adjustments.rs

@@ -3,7 +3,7 @@
 #![crate_type = "lib"]
 
 // Hack to get the correct size for the length part in slices
-// CHECK: @helper([[USIZE:i[0-9]+]] %_1)
+// CHECK: @helper([[USIZE:i[0-9]+]] noundef %_1)
 #[no_mangle]
 pub fn helper(_: usize) {
 }

tests/codegen/box-maybe-uninit-llvm14.rs

@@ -31,4 +31,4 @@ pub fn box_uninitialized2() -> Box<MaybeUninit<[usize; 1024 * 1024]>> {
 // Hide the LLVM 15+ `allocalign` attribute in the declaration of __rust_alloc
 // from the CHECK-NOT above. We don't check the attributes here because we can't rely
 // on all of them being set until LLVM 15.
-// CHECK: declare noalias{{.*}} @__rust_alloc(i{{[0-9]+}}, i{{[0-9]+.*}})
+// CHECK: declare noalias{{.*}} @__rust_alloc(i{{[0-9]+}} noundef, i{{[0-9]+.*}} noundef)

tests/codegen/box-maybe-uninit.rs

@@ -28,6 +28,6 @@ pub fn box_uninitialized2() -> Box<MaybeUninit<[usize; 1024 * 1024]>> {
 
 // Hide the `allocalign` attribute in the declaration of __rust_alloc
 // from the CHECK-NOT above, and also verify the attributes got set reasonably.
-// CHECK: declare noalias ptr @__rust_alloc(i{{[0-9]+}}, i{{[0-9]+}} allocalign) unnamed_addr [[RUST_ALLOC_ATTRS:#[0-9]+]]
+// CHECK: declare noalias noundef ptr @__rust_alloc(i{{[0-9]+}} noundef, i{{[0-9]+}} allocalign noundef) unnamed_addr [[RUST_ALLOC_ATTRS:#[0-9]+]]
 
 // CHECK-DAG: attributes [[RUST_ALLOC_ATTRS]] = { {{.*}} allockind("alloc,uninitialized,aligned") allocsize(0) uwtable "alloc-family"="__rust_alloc" {{.*}} }

tests/codegen/c-variadic.rs

@@ -15,7 +15,7 @@ extern "C" {
 
 pub unsafe extern "C" fn use_foreign_c_variadic_0() {
     // Ensure that we correctly call foreign C-variadic functions.
-    // CHECK: call void (i32, ...) @foreign_c_variadic_0([[PARAM:i32( signext)?]] 0)
+    // CHECK: call void (i32, ...) @foreign_c_variadic_0([[PARAM:i32 noundef( signext)?]] 0)
     foreign_c_variadic_0(0);
     // CHECK: call void (i32, ...) @foreign_c_variadic_0([[PARAM]] 0, [[PARAM]] 42)
     foreign_c_variadic_0(0, 42i32);
@@ -61,7 +61,7 @@ pub unsafe extern "C" fn c_variadic(n: i32, mut ap: ...) -> i32 {
 // Ensure that we generate the correct `call` signature when calling a Rust
 // defined C-variadic.
 pub unsafe fn test_c_variadic_call() {
-    // CHECK: call [[RET:(signext )?i32]] (i32, ...) @c_variadic([[PARAM]] 0)
+    // CHECK: call [[RET:noundef( signext)? i32]] (i32, ...) @c_variadic([[PARAM]] 0)
     c_variadic(0);
     // CHECK: call [[RET]] (i32, ...) @c_variadic([[PARAM]] 0, [[PARAM]] 42)
     c_variadic(0, 42i32);

tests/codegen/call-llvm-intrinsics.rs

@@ -23,7 +23,7 @@ pub fn do_call() {
 
     unsafe {
         // Ensure that we `call` LLVM intrinsics instead of trying to `invoke` them
-        // CHECK: call float @llvm.sqrt.f32(float 4.000000e+00
+        // CHECK: call noundef float @llvm.sqrt.f32(float noundef 4.000000e+00
         sqrt(4.0);
     }
 }

tests/codegen/comparison-operators-newtype.rs

@@ -13,7 +13,7 @@ use std::cmp::Ordering;
 pub struct Foo(u16);
 
 // CHECK-LABEL: @check_lt
-// CHECK-SAME: (i16 %[[A:.+]], i16 %[[B:.+]])
+// CHECK-SAME: (i16 noundef %[[A:.+]], i16 noundef %[[B:.+]])
 #[no_mangle]
 pub fn check_lt(a: Foo, b: Foo) -> bool {
     // CHECK: %[[R:.+]] = icmp ult i16 %[[A]], %[[B]]
@@ -22,7 +22,7 @@ pub fn check_lt(a: Foo, b: Foo) -> bool {
 }
 
 // CHECK-LABEL: @check_le
-// CHECK-SAME: (i16 %[[A:.+]], i16 %[[B:.+]])
+// CHECK-SAME: (i16 noundef %[[A:.+]], i16 noundef %[[B:.+]])
 #[no_mangle]
 pub fn check_le(a: Foo, b: Foo) -> bool {
     // CHECK: %[[R:.+]] = icmp ule i16 %[[A]], %[[B]]
@@ -31,7 +31,7 @@ pub fn check_le(a: Foo, b: Foo) -> bool {
 }
 
 // CHECK-LABEL: @check_gt
-// CHECK-SAME: (i16 %[[A:.+]], i16 %[[B:.+]])
+// CHECK-SAME: (i16 noundef %[[A:.+]], i16 noundef %[[B:.+]])
 #[no_mangle]
 pub fn check_gt(a: Foo, b: Foo) -> bool {
     // CHECK: %[[R:.+]] = icmp ugt i16 %[[A]], %[[B]]
@@ -40,7 +40,7 @@ pub fn check_gt(a: Foo, b: Foo) -> bool {
 }
 
 // CHECK-LABEL: @check_ge
-// CHECK-SAME: (i16 %[[A:.+]], i16 %[[B:.+]])
+// CHECK-SAME: (i16 noundef %[[A:.+]], i16 noundef %[[B:.+]])
 #[no_mangle]
 pub fn check_ge(a: Foo, b: Foo) -> bool {
     // CHECK: %[[R:.+]] = icmp uge i16 %[[A]], %[[B]]

tests/codegen/enum-match.rs

@@ -11,7 +11,7 @@ pub enum Enum0 {
     B,
 }
 
-// CHECK: define i8 @match0{{.*}}
+// CHECK: define noundef i8 @match0{{.*}}
 // CHECK-NEXT: start:
 // CHECK-NEXT: %1 = icmp eq i8 %0, 2
 // CHECK-NEXT: %2 = and i8 %0, 1
@@ -32,7 +32,7 @@ pub enum Enum1 {
     C,
 }
 
-// CHECK: define i8 @match1{{.*}}
+// CHECK: define noundef i8 @match1{{.*}}
 // CHECK-NEXT: start:
 // CHECK-NEXT: [[DISCR:%.*]] = {{.*}}call i8 @llvm.usub.sat.i8(i8 %0, i8 1)
 // CHECK-NEXT: switch i8 [[DISCR]], label {{.*}} [
@@ -88,7 +88,7 @@ pub enum Enum2 {
     E,
 }
 
-// CHECK: define i8 @match2{{.*}}
+// CHECK: define noundef i8 @match2{{.*}}
 // CHECK-NEXT: start:
 // CHECK-NEXT: %1 = add i8 %0, 2
 // CHECK-NEXT: %2 = zext i8 %1 to i64

tests/codegen/fastcall-inreg.rs

@@ -15,27 +15,27 @@ trait Sized {}
 trait Copy {}
 
 pub mod tests {
-    // CHECK: @f1(i32 inreg %_1, i32 inreg %_2, i32 %_3)
+    // CHECK: @f1(i32 inreg noundef %_1, i32 inreg noundef %_2, i32 noundef %_3)
     #[no_mangle]
     pub extern "fastcall" fn f1(_: i32, _: i32, _: i32) {}
 
-    // CHECK: @f2({{i32\*|ptr}} inreg %_1, {{i32\*|ptr}} inreg %_2, {{i32\*|ptr}} %_3)
+    // CHECK: @f2({{i32\*|ptr}} inreg noundef %_1, {{i32\*|ptr}} inreg noundef %_2, {{i32\*|ptr}} noundef %_3)
     #[no_mangle]
     pub extern "fastcall" fn f2(_: *const i32, _: *const i32, _: *const i32) {}
 
-    // CHECK: @f3(float %_1, i32 inreg %_2, i32 inreg %_3, i32 %_4)
+    // CHECK: @f3(float noundef %_1, i32 inreg noundef %_2, i32 inreg noundef %_3, i32 noundef %_4)
     #[no_mangle]
     pub extern "fastcall" fn f3(_: f32, _: i32, _: i32, _: i32) {}
 
-    // CHECK: @f4(i32 inreg %_1, float %_2, i32 inreg %_3, i32 %_4)
+    // CHECK: @f4(i32 inreg noundef %_1, float noundef %_2, i32 inreg noundef %_3, i32 noundef %_4)
     #[no_mangle]
     pub extern "fastcall" fn f4(_: i32, _: f32, _: i32, _: i32) {}
 
-    // CHECK: @f5(i64 %_1, i32 %_2)
+    // CHECK: @f5(i64 noundef %_1, i32 noundef %_2)
     #[no_mangle]
     pub extern "fastcall" fn f5(_: i64, _: i32) {}
 
-    // CHECK: @f6(i1 inreg noundef zeroext %_1, i32 inreg %_2, i32 %_3)
+    // CHECK: @f6(i1 inreg noundef zeroext %_1, i32 inreg noundef %_2, i32 noundef %_3)
     #[no_mangle]
     pub extern "fastcall" fn f6(_: bool, _: i32, _: i32) {}
 }

tests/codegen/fewer-names.rs

@@ -7,11 +7,11 @@
 
 #[no_mangle]
 pub fn sum(x: u32, y: u32) -> u32 {
-// YES-LABEL: define{{.*}}i32 @sum(i32 %0, i32 %1)
+// YES-LABEL: define{{.*}}i32 @sum(i32 noundef %0, i32 noundef %1)
 // YES-NEXT:    %3 = add i32 %1, %0
 // YES-NEXT:    ret i32 %3
 
-// NO-LABEL: define{{.*}}i32 @sum(i32 %x, i32 %y)
+// NO-LABEL: define{{.*}}i32 @sum(i32 noundef %x, i32 noundef %y)
 // NO-NEXT:  start:
 // NO-NEXT:    %z = add i32 %y, %x
 // NO-NEXT:    ret i32 %z

tests/codegen/frame-pointer.rs

@@ -20,7 +20,7 @@ trait Copy { }
 impl Copy for u32 {}
 
 
-// CHECK: define i32 @peach{{.*}}[[PEACH_ATTRS:\#[0-9]+]] {
+// CHECK: define noundef i32 @peach{{.*}}[[PEACH_ATTRS:\#[0-9]+]] {
 #[no_mangle]
 pub fn peach(x: u32) -> u32 {
     x

tests/codegen/function-arguments.rs

@@ -61,7 +61,7 @@ pub fn maybeuninit_char(x: MaybeUninit<char>) -> MaybeUninit<char> {
   x
 }
 
-// CHECK: i64 @int(i64 %x)
+// CHECK: noundef i64 @int(i64 noundef %x)
 #[no_mangle]
 pub fn int(x: u64) -> u64 {
   x
@@ -73,7 +73,7 @@ pub fn nonzero_int(x: NonZeroU64) -> NonZeroU64 {
   x
 }
 
-// CHECK: i64 @option_nonzero_int(i64 %x)
+// CHECK: noundef i64 @option_nonzero_int(i64 noundef %x)
 #[no_mangle]
 pub fn option_nonzero_int(x: Option<NonZeroU64>) -> Option<NonZeroU64> {
   x
@@ -138,7 +138,7 @@ pub fn indirect_struct(_: S) {
 pub fn borrowed_struct(_: &S) {
 }
 
-// CHECK: @raw_struct({{%S\*|ptr}} %_1)
+// CHECK: @raw_struct({{%S\*|ptr}} noundef %_1)
 #[no_mangle]
 pub fn raw_struct(_: *const S) {
 }
@@ -160,35 +160,35 @@ pub fn struct_return() -> S {
 }
 
 // Hack to get the correct size for the length part in slices
-// CHECK: @helper([[USIZE:i[0-9]+]] %_1)
+// CHECK: @helper([[USIZE:i[0-9]+]] noundef %_1)
 #[no_mangle]
 pub fn helper(_: usize) {
 }
 
-// CHECK: @slice({{\[0 x i8\]\*|ptr}} noalias noundef nonnull readonly align 1 %_1.0, [[USIZE]] %_1.1)
+// CHECK: @slice({{\[0 x i8\]\*|ptr}} noalias noundef nonnull readonly align 1 %_1.0, [[USIZE]] noundef %_1.1)
 // FIXME #25759 This should also have `nocapture`
 #[no_mangle]
 pub fn slice(_: &[u8]) {
 }
 
-// CHECK: @mutable_slice({{\[0 x i8\]\*|ptr}} noalias noundef nonnull align 1 %_1.0, [[USIZE]] %_1.1)
+// CHECK: @mutable_slice({{\[0 x i8\]\*|ptr}} noalias noundef nonnull align 1 %_1.0, [[USIZE]] noundef %_1.1)
 // FIXME #25759 This should also have `nocapture`
 #[no_mangle]
 pub fn mutable_slice(_: &mut [u8]) {
 }
 
-// CHECK: @unsafe_slice({{\[0 x i16\]\*|ptr}} noundef nonnull align 2 %_1.0, [[USIZE]] %_1.1)
+// CHECK: @unsafe_slice({{\[0 x i16\]\*|ptr}} noundef nonnull align 2 %_1.0, [[USIZE]] noundef %_1.1)
 // unsafe interior means this isn't actually readonly and there may be aliases ...
 #[no_mangle]
 pub fn unsafe_slice(_: &[UnsafeInner]) {
 }
 
-// CHECK: @raw_slice({{\[0 x i8\]\*|ptr}} %_1.0, [[USIZE]] %_1.1)
+// CHECK: @raw_slice({{\[0 x i8\]\*|ptr}} noundef %_1.0, [[USIZE]] noundef %_1.1)
 #[no_mangle]
 pub fn raw_slice(_: *const [u8]) {
 }
 
-// CHECK: @str({{\[0 x i8\]\*|ptr}} noalias noundef nonnull readonly align 1 %_1.0, [[USIZE]] %_1.1)
+// CHECK: @str({{\[0 x i8\]\*|ptr}} noalias noundef nonnull readonly align 1 %_1.0, [[USIZE]] noundef %_1.1)
 // FIXME #25759 This should also have `nocapture`
 #[no_mangle]
 pub fn str(_: &[u8]) {
@@ -197,26 +197,26 @@ pub fn str(_: &[u8]) {
 // CHECK: @trait_borrow({{\{\}\*|ptr}} noundef nonnull align 1 %_1.0, {{.+}} noalias noundef readonly align {{.*}} dereferenceable({{.*}}) %_1.1)
 // FIXME #25759 This should also have `nocapture`
 #[no_mangle]
-pub fn trait_borrow(_: &Drop) {
+pub fn trait_borrow(_: &dyn Drop) {
 }
 
-// CHECK: @trait_raw({{\{\}\*|ptr}} %_1.0, {{.+}} noalias noundef readonly align {{.*}} dereferenceable({{.*}}) %_1.1)
+// CHECK: @trait_raw({{\{\}\*|ptr}} noundef %_1.0, {{.+}} noalias noundef readonly align {{.*}} dereferenceable({{.*}}) %_1.1)
 #[no_mangle]
-pub fn trait_raw(_: *const Drop) {
+pub fn trait_raw(_: *const dyn Drop) {
 }
 
 // CHECK: @trait_box({{\{\}\*|ptr}} noalias noundef nonnull align 1{{( %0)?}}, {{.+}} noalias noundef readonly align {{.*}} dereferenceable({{.*}}){{( %1)?}})
 #[no_mangle]
-pub fn trait_box(_: Box<Drop>) {
+pub fn trait_box(_: Box<dyn Drop>) {
 }
 
 // CHECK: { {{i8\*|ptr}}, {{i8\*|ptr}} } @trait_option({{i8\*|ptr}} noalias noundef align 1 %x.0, {{i8\*|ptr}} %x.1)
 #[no_mangle]
-pub fn trait_option(x: Option<Box<Drop>>) -> Option<Box<Drop>> {
+pub fn trait_option(x: Option<Box<dyn Drop>>) -> Option<Box<dyn Drop>> {
   x
 }
 
-// CHECK: { {{\[0 x i16\]\*|ptr}}, [[USIZE]] } @return_slice({{\[0 x i16\]\*|ptr}} noalias noundef nonnull readonly align 2 %x.0, [[USIZE]] %x.1)
+// CHECK: { {{\[0 x i16\]\*|ptr}}, [[USIZE]] } @return_slice({{\[0 x i16\]\*|ptr}} noalias noundef nonnull readonly align 2 %x.0, [[USIZE]] noundef %x.1)
 #[no_mangle]
 pub fn return_slice(x: &[u16]) -> &[u16] {
   x

tests/codegen/intrinsics/const_eval_select.rs

@@ -13,6 +13,6 @@ pub fn hi(n: i32) -> i32 { n }
 
 #[no_mangle]
 pub unsafe fn hey() {
-    // CHECK: call i32 @hi(i32
+    // CHECK: call noundef i32 @hi(i32
     const_eval_select((42,), foo, hi);
 }

tests/codegen/intrinsics/mask.rs

@@ -2,7 +2,7 @@
 #![feature(core_intrinsics)]
 
 // CHECK-LABEL: @mask_ptr
-// CHECK-SAME: [[WORD:i[0-9]+]] %mask
+// CHECK-SAME: [[WORD:i[0-9]+]] noundef %mask
 #[no_mangle]
 pub fn mask_ptr(ptr: *const u16, mask: usize) -> *const u16 {
     // CHECK: call

tests/codegen/issue-32031.rs

@@ -5,7 +5,7 @@
 #[no_mangle]
 pub struct F32(f32);
 
-// CHECK: define{{.*}}float @add_newtype_f32(float %a, float %b)
+// CHECK: define{{.*}}float @add_newtype_f32(float noundef %a, float noundef %b)
 #[inline(never)]
 #[no_mangle]
 pub fn add_newtype_f32(a: F32, b: F32) -> F32 {
@@ -15,7 +15,7 @@ pub fn add_newtype_f32(a: F32, b: F32) -> F32 {
 #[no_mangle]
 pub struct F64(f64);
 
-// CHECK: define{{.*}}double @add_newtype_f64(double %a, double %b)
+// CHECK: define{{.*}}double @add_newtype_f64(double noundef %a, double noundef %b)
 #[inline(never)]
 #[no_mangle]
 pub fn add_newtype_f64(a: F64, b: F64) -> F64 {

tests/codegen/issue-58881.rs

@@ -16,6 +16,6 @@ struct Bar(u64, u64, u64);
 
 // Ensure that emit arguments of the correct type.
 pub unsafe fn test_call_variadic() {
-    // CHECK: call void (i32, ...) @variadic_fn(i32 0, i8 {{.*}}, {{%Bar\*|ptr}} {{.*}})
+    // CHECK: call void (i32, ...) @variadic_fn(i32 noundef 0, i8 {{.*}}, {{%Bar\*|ptr}} {{.*}})
     variadic_fn(0, Foo(0), Bar(0, 0, 0))
 }

tests/codegen/loads.rs

@@ -51,7 +51,7 @@ pub fn load_scalar_pair<'a>(x: &(&'a i32, &'a Align16)) -> (&'a i32, &'a Align16
 #[no_mangle]
 pub fn load_raw_pointer<'a>(x: &*const i32) -> *const i32 {
     // loaded raw pointer should not have !nonnull, !align, or !noundef metadata
-    // CHECK: load {{i32\*|ptr}}, {{i32\*\*|ptr}} %x, align [[PTR_ALIGNMENT]]{{$}}
+    // CHECK: load {{i32\*|ptr}}, {{i32\*\*|ptr}} %x, align [[PTR_ALIGNMENT]], !noundef !2{{$}}
     *x
 }
 
@@ -93,7 +93,7 @@ pub fn load_maybeuninit_enum_bool(x: &MaybeUninit<MyBool>) -> MaybeUninit<MyBool
 // CHECK-LABEL: @load_int
 #[no_mangle]
 pub fn load_int(x: &u16) -> u16 {
-    // CHECK: load i16, {{i16\*|ptr}} %x, align 2{{$}}
+    // CHECK: load i16, {{i16\*|ptr}} %x, align 2, !noundef !2{{$}}
     *x
 }
 
@@ -107,7 +107,7 @@ pub fn load_nonzero_int(x: &NonZeroU16) -> NonZeroU16 {
 // CHECK-LABEL: @load_option_nonzero_int
 #[no_mangle]
 pub fn load_option_nonzero_int(x: &Option<NonZeroU16>) -> Option<NonZeroU16> {
-    // CHECK: load i16, {{i16\*|ptr}} %x, align 2{{$}}
+    // CHECK: load i16, {{i16\*|ptr}} %x, align 2, !noundef !2{{$}}
     *x
 }
 

tests/codegen/naked-functions.rs

@@ -19,7 +19,7 @@ pub unsafe extern "C" fn naked_empty() {
 }
 
 // CHECK: Function Attrs: naked
-// CHECK-NEXT: define{{.*}}i{{[0-9]+}} @naked_with_args_and_return(i64 %a, i64 %b)
+// CHECK-NEXT: define{{.*}}i{{[0-9]+}} @naked_with_args_and_return(i64 noundef %a, i64 noundef %b)
 #[no_mangle]
 #[naked]
 pub unsafe extern "C" fn naked_with_args_and_return(a: isize, b: isize) -> isize {