mirror of https://github.com/rust-lang/rust.git
do not mark interior mutable shared refs as dereferenceable
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@ -2636,7 +2636,7 @@ where
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if ty.is_unpin(tcx.at(DUMMY_SP), cx.param_env()) {
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PointerKind::UniqueBorrowed
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} else {
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PointerKind::SharedMutable
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PointerKind::UniqueBorrowedPinned
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}
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}
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}
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@ -3255,10 +3255,13 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
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// `Box` (`UniqueBorrowed`) are not necessarily dereferenceable
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// for the entire duration of the function as they can be deallocated
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// at any time. Set their valid size to 0.
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// at any time. Same for shared mutable references. If LLVM had a
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// way to say "dereferenceable on entry" we could use it here.
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attrs.pointee_size = match kind {
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PointerKind::UniqueOwned => Size::ZERO,
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_ => pointee.size,
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PointerKind::UniqueBorrowed
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| PointerKind::UniqueBorrowedPinned
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| PointerKind::Frozen => pointee.size,
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PointerKind::SharedMutable | PointerKind::UniqueOwned => Size::ZERO,
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};
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// `Box`, `&T`, and `&mut T` cannot be undef.
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@ -3285,7 +3288,9 @@ impl<'tcx> LayoutCx<'tcx, TyCtxt<'tcx>> {
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// or not to actually emit the attribute. It can also be controlled with the
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// `-Zmutable-noalias` debugging option.
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let no_alias = match kind {
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PointerKind::SharedMutable | PointerKind::UniqueBorrowed => false,
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PointerKind::SharedMutable
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| PointerKind::UniqueBorrowed
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| PointerKind::UniqueBorrowedPinned => false,
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PointerKind::UniqueOwned => noalias_for_box,
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PointerKind::Frozen => !is_return,
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};
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@ -1352,13 +1352,17 @@ pub enum PointerKind {
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/// Most general case, we know no restrictions to tell LLVM.
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SharedMutable,
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/// `&T` where `T` contains no `UnsafeCell`, is `noalias` and `readonly`.
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/// `&T` where `T` contains no `UnsafeCell`, is `dereferenceable`, `noalias` and `readonly`.
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Frozen,
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/// `&mut T` which is `noalias` but not `readonly`.
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/// `&mut T` which is `dereferenceable` and `noalias` but not `readonly`.
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UniqueBorrowed,
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/// `Box<T>`, unlike `UniqueBorrowed`, it also has `noalias` on returns.
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/// `&mut !Unpin`, which is `dereferenceable` but neither `noalias` nor `readonly`.
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UniqueBorrowedPinned,
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/// `Box<T>`, which is `noalias` (even on return types, unlike the above) but neither `readonly`
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/// nor `dereferenceable`.
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UniqueOwned,
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}
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@ -5,6 +5,7 @@
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use std::mem::MaybeUninit;
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use std::num::NonZeroU64;
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use std::marker::PhantomPinned;
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pub struct S {
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_field: [i32; 8],
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@ -14,6 +15,11 @@ pub struct UnsafeInner {
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_field: std::cell::UnsafeCell<i16>,
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}
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pub struct NotUnpin {
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_field: i32,
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_marker: PhantomPinned,
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}
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pub enum MyBool {
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True,
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False,
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@ -91,7 +97,7 @@ pub fn static_borrow(_: &'static i32) {
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pub fn named_borrow<'r>(_: &'r i32) {
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}
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// CHECK: @unsafe_borrow({{i16\*|ptr}} noundef align 2 dereferenceable(2) %_1)
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// CHECK: @unsafe_borrow({{i16\*|ptr}} noundef nonnull align 2 %_1)
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// unsafe interior means this isn't actually readonly and there may be aliases ...
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#[no_mangle]
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pub fn unsafe_borrow(_: &UnsafeInner) {
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@ -109,6 +115,18 @@ pub fn mutable_unsafe_borrow(_: &mut UnsafeInner) {
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pub fn mutable_borrow(_: &mut i32) {
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}
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#[no_mangle]
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// CHECK: @mutable_notunpin_borrow({{i32\*|ptr}} noundef align 4 dereferenceable(4) %_1)
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// This one is *not* `noalias` because it might be self-referential.
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pub fn mutable_notunpin_borrow(_: &mut NotUnpin) {
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}
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// CHECK: @notunpin_borrow({{i32\*|ptr}} noalias noundef readonly align 4 dereferenceable(4) %_1)
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// But `&NotUnpin` behaves perfectly normal.
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#[no_mangle]
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pub fn notunpin_borrow(_: &NotUnpin) {
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}
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// CHECK: @indirect_struct({{%S\*|ptr}} noalias nocapture noundef dereferenceable(32) %_1)
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#[no_mangle]
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pub fn indirect_struct(_: S) {
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