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Stop having two different alignment constants

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* Stop having two different alignment constants
* Update library/core/src/alloc/global.rs
This commit is contained in:
Mark Rousskov 2026-02-08 19:54:03 +00:00
parent 08a4ce529f
commit 4a979d546b
8 changed files with 14 additions and 11 deletions
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7
library/core/src/alloc/global.rs
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@ -284,9 +284,10 @@ pub unsafe trait GlobalAlloc {
/// [`handle_alloc_error`]: ../../alloc/alloc/fn.handle_alloc_error.html
#[stable(feature = "global_alloc", since = "1.28.0")]
unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
// SAFETY: the caller must ensure that the `new_size` does not overflow.
// `layout.align()` comes from a `Layout` and is thus guaranteed to be valid.
let new_layout = unsafe { Layout::from_size_align_unchecked(new_size, layout.align()) };
let alignment = layout.alignment();
// SAFETY: the caller must ensure that the `new_size` does not overflow
// when rounded up to the next multiple of `alignment`.
let new_layout = unsafe { Layout::from_size_alignment_unchecked(new_size, alignment) };
// SAFETY: the caller must ensure that `new_layout` is greater than zero.
let new_ptr = unsafe { self.alloc(new_layout) };
if !new_ptr.is_null() {

5
library/core/src/mem/mod.rs
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@ -1260,7 +1260,10 @@ pub trait SizedTypeProperties: Sized {
#[doc(hidden)]
#[unstable(feature = "ptr_alignment_type", issue = "102070")]
const ALIGNMENT: Alignment = Alignment::of::<Self>();
const ALIGNMENT: Alignment = {
// This can't panic since type alignment is always a power of two.
Alignment::new(Self::ALIGN).unwrap()
};
/// `true` if this type requires no storage.
/// `false` if its [size](size_of) is greater than zero.

3
library/core/src/ptr/alignment.rs
View file

@ -52,8 +52,7 @@ impl Alignment {
#[inline]
#[must_use]
pub const fn of<T>() -> Self {
// This can't actually panic since type alignment is always a power of two.
const { Alignment::new(align_of::<T>()).unwrap() }
<T as mem::SizedTypeProperties>::ALIGNMENT
}
/// Returns the [ABI]-required minimum alignment of the type of the value that `val` points to.

2
tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.32bit.panic-abort.diff
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@ -44,7 +44,7 @@
StorageLive(_4);
StorageLive(_5);
StorageLive(_6);
- _6 = const std::ptr::Alignment::of::<[bool; 0]>::{constant#0} as *const [bool; 0] (Transmute);
- _6 = const <[bool; 0] as std::mem::SizedTypeProperties>::ALIGNMENT as *const [bool; 0] (Transmute);
- _5 = NonNull::<[bool; 0]> { pointer: copy _6 };
+ _6 = const {0x1 as *const [bool; 0]};
+ _5 = const NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }};

2
tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.32bit.panic-unwind.diff
View file

@ -44,7 +44,7 @@
StorageLive(_4);
StorageLive(_5);
StorageLive(_6);
- _6 = const std::ptr::Alignment::of::<[bool; 0]>::{constant#0} as *const [bool; 0] (Transmute);
- _6 = const <[bool; 0] as std::mem::SizedTypeProperties>::ALIGNMENT as *const [bool; 0] (Transmute);
- _5 = NonNull::<[bool; 0]> { pointer: copy _6 };
+ _6 = const {0x1 as *const [bool; 0]};
+ _5 = const NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }};

2
tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.64bit.panic-abort.diff
View file

@ -44,7 +44,7 @@
StorageLive(_4);
StorageLive(_5);
StorageLive(_6);
- _6 = const std::ptr::Alignment::of::<[bool; 0]>::{constant#0} as *const [bool; 0] (Transmute);
- _6 = const <[bool; 0] as std::mem::SizedTypeProperties>::ALIGNMENT as *const [bool; 0] (Transmute);
- _5 = NonNull::<[bool; 0]> { pointer: copy _6 };
+ _6 = const {0x1 as *const [bool; 0]};
+ _5 = const NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }};

2
tests/mir-opt/dataflow-const-prop/default_boxed_slice.main.GVN.64bit.panic-unwind.diff
View file

@ -44,7 +44,7 @@
StorageLive(_4);
StorageLive(_5);
StorageLive(_6);
- _6 = const std::ptr::Alignment::of::<[bool; 0]>::{constant#0} as *const [bool; 0] (Transmute);
- _6 = const <[bool; 0] as std::mem::SizedTypeProperties>::ALIGNMENT as *const [bool; 0] (Transmute);
- _5 = NonNull::<[bool; 0]> { pointer: copy _6 };
+ _6 = const {0x1 as *const [bool; 0]};
+ _5 = const NonNull::<[bool; 0]> {{ pointer: {0x1 as *const [bool; 0]} }};

2
tests/mir-opt/gvn_ptr_eq_with_constant.main.GVN.diff
View file

@ -40,7 +40,7 @@
StorageLive(_1);
StorageLive(_2);
StorageLive(_3);
- _3 = const std::ptr::Alignment::of::<u8>::{constant#0};
- _3 = const <u8 as std::mem::SizedTypeProperties>::ALIGNMENT;
- _2 = copy _3 as *mut u8 (Transmute);
+ _3 = const std::ptr::Alignment {{ _inner_repr_trick: std::ptr::alignment::AlignmentEnum::_Align1Shl0 }};
+ _2 = const {0x1 as *mut u8};