Auto merge of #106294 - Nilstrieb:noundef-everything, r=nikic

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. After #99182, 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.

cc `@nagisa` `@scottmcm` `@nikic`

1 files changed, 42 insertions, 16 deletions

diff --git a/tests/codegen/function-arguments.rs b/tests/codegen/function-arguments.rs
index 0f9e90f6ba7..1f979d7b90a 100644
--- a/tests/codegen/function-arguments.rs
+++ b/tests/codegen/function-arguments.rs
@@ -1,11 +1,11 @@
 // compile-flags: -O -C no-prepopulate-passes
 
 #![crate_type = "lib"]
-#![feature(rustc_attrs)]
 
 use std::mem::MaybeUninit;
 use std::num::NonZeroU64;
 use std::marker::PhantomPinned;
+use std::ptr::NonNull;
 
 pub struct S {
   _field: [i32; 8],
@@ -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
@@ -138,11 +138,27 @@ pub fn indirect_struct(_: S) {
 pub fn borrowed_struct(_: &S) {
 }
 
-// CHECK: @raw_struct({{%S\*|ptr}} %_1)
+// CHECK: @option_borrow({{i32\*|ptr}} noalias noundef readonly align 4 dereferenceable_or_null(4) %x)
+#[no_mangle]
+pub fn option_borrow(x: Option<&i32>) {
+}
+
+// CHECK: @option_borrow_mut({{i32\*|ptr}} noalias noundef align 4 dereferenceable_or_null(4) %x)
+#[no_mangle]
+pub fn option_borrow_mut(x: Option<&mut i32>) {
+}
+
+// CHECK: @raw_struct({{%S\*|ptr}} noundef %_1)
 #[no_mangle]
 pub fn raw_struct(_: *const S) {
 }
 
+// CHECK: @raw_option_nonnull_struct({{i32\*|ptr}} noundef %_1)
+#[no_mangle]
+pub fn raw_option_nonnull_struct(_: Option<NonNull<S>>) {
+}
+
+
 // `Box` can get deallocated during execution of the function, so it should
 // not get `dereferenceable`.
 // CHECK: noundef nonnull align 4 {{i32\*|ptr}} @_box({{i32\*|ptr}} noalias noundef nonnull align 4 %x)
@@ -160,35 +176,35 @@ 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 +213,36 @@ 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: @option_trait_borrow({{i8\*|ptr}} noundef align 1 %x.0, {{i8\*|ptr}} %x.1)
+#[no_mangle]
+pub fn option_trait_borrow(x: Option<&dyn Drop>) {
+}
+
+// CHECK: @option_trait_borrow_mut({{i8\*|ptr}} noundef align 1 %x.0, {{i8\*|ptr}} %x.1)
+#[no_mangle]
+pub fn option_trait_borrow_mut(x: Option<&mut 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