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Rollup merge of rust-lang#102207 - CraftSpider:const-layout, r=scottmcm
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Constify remaining `Layout` methods

Makes the methods on `Layout` that aren't yet unstably const, under the same feature and issue, rust-lang#67521. Most of them required no changes, only non-trivial change is probably constifying `ValidAlignment` which may affect rust-lang#102072
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Manishearth authored Nov 18, 2022
2 parents 70fe5f0 + bbcdebd commit 968b9d8
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Showing 3 changed files with 46 additions and 18 deletions.
36 changes: 25 additions & 11 deletions library/core/src/alloc/layout.rs
Original file line number Diff line number Diff line change
Expand Up @@ -157,9 +157,10 @@ impl Layout {
/// allocate backing structure for `T` (which could be a trait
/// or other unsized type like a slice).
#[stable(feature = "alloc_layout", since = "1.28.0")]
#[rustc_const_unstable(feature = "const_alloc_layout", issue = "67521")]
#[must_use]
#[inline]
pub fn for_value<T: ?Sized>(t: &T) -> Self {
pub const fn for_value<T: ?Sized>(t: &T) -> Self {
let (size, align) = (mem::size_of_val(t), mem::align_of_val(t));
// SAFETY: see rationale in `new` for why this is using the unsafe variant
unsafe { Layout::from_size_align_unchecked(size, align) }
Expand Down Expand Up @@ -191,8 +192,9 @@ impl Layout {
/// [trait object]: ../../book/ch17-02-trait-objects.html
/// [extern type]: ../../unstable-book/language-features/extern-types.html
#[unstable(feature = "layout_for_ptr", issue = "69835")]
#[rustc_const_unstable(feature = "const_alloc_layout", issue = "67521")]
#[must_use]
pub unsafe fn for_value_raw<T: ?Sized>(t: *const T) -> Self {
pub const unsafe fn for_value_raw<T: ?Sized>(t: *const T) -> Self {
// SAFETY: we pass along the prerequisites of these functions to the caller
let (size, align) = unsafe { (mem::size_of_val_raw(t), mem::align_of_val_raw(t)) };
// SAFETY: see rationale in `new` for why this is using the unsafe variant
Expand Down Expand Up @@ -229,8 +231,9 @@ impl Layout {
/// Returns an error if the combination of `self.size()` and the given
/// `align` violates the conditions listed in [`Layout::from_size_align`].
#[stable(feature = "alloc_layout_manipulation", since = "1.44.0")]
#[rustc_const_unstable(feature = "const_alloc_layout", issue = "67521")]
#[inline]
pub fn align_to(&self, align: usize) -> Result<Self, LayoutError> {
pub const fn align_to(&self, align: usize) -> Result<Self, LayoutError> {
Layout::from_size_align(self.size(), cmp::max(self.align(), align))
}

Expand Down Expand Up @@ -287,10 +290,11 @@ impl Layout {
/// This is equivalent to adding the result of `padding_needed_for`
/// to the layout's current size.
#[stable(feature = "alloc_layout_manipulation", since = "1.44.0")]
#[rustc_const_unstable(feature = "const_alloc_layout", issue = "67521")]
#[must_use = "this returns a new `Layout`, \
without modifying the original"]
#[inline]
pub fn pad_to_align(&self) -> Layout {
pub const fn pad_to_align(&self) -> Layout {
let pad = self.padding_needed_for(self.align());
// This cannot overflow. Quoting from the invariant of Layout:
// > `size`, when rounded up to the nearest multiple of `align`,
Expand All @@ -311,8 +315,9 @@ impl Layout {
///
/// On arithmetic overflow, returns `LayoutError`.
#[unstable(feature = "alloc_layout_extra", issue = "55724")]
#[rustc_const_unstable(feature = "const_alloc_layout", issue = "67521")]
#[inline]
pub fn repeat(&self, n: usize) -> Result<(Self, usize), LayoutError> {
pub const fn repeat(&self, n: usize) -> Result<(Self, usize), LayoutError> {
// This cannot overflow. Quoting from the invariant of Layout:
// > `size`, when rounded up to the nearest multiple of `align`,
// > must not overflow isize (i.e., the rounded value must be
Expand All @@ -321,7 +326,8 @@ impl Layout {
let alloc_size = padded_size.checked_mul(n).ok_or(LayoutError)?;

// The safe constructor is called here to enforce the isize size limit.
Layout::from_size_alignment(alloc_size, self.align).map(|layout| (layout, padded_size))
let layout = Layout::from_size_alignment(alloc_size, self.align)?;
Ok((layout, padded_size))
}

/// Creates a layout describing the record for `self` followed by
Expand Down Expand Up @@ -370,8 +376,9 @@ impl Layout {
/// # assert_eq!(repr_c(&[u64, u32, u16, u32]), Ok((s, vec![0, 8, 12, 16])));
/// ```
#[stable(feature = "alloc_layout_manipulation", since = "1.44.0")]
#[rustc_const_unstable(feature = "const_alloc_layout", issue = "67521")]
#[inline]
pub fn extend(&self, next: Self) -> Result<(Self, usize), LayoutError> {
pub const fn extend(&self, next: Self) -> Result<(Self, usize), LayoutError> {
let new_align = cmp::max(self.align, next.align);
let pad = self.padding_needed_for(next.align());

Expand All @@ -396,8 +403,9 @@ impl Layout {
///
/// On arithmetic overflow, returns `LayoutError`.
#[unstable(feature = "alloc_layout_extra", issue = "55724")]
#[rustc_const_unstable(feature = "const_alloc_layout", issue = "67521")]
#[inline]
pub fn repeat_packed(&self, n: usize) -> Result<Self, LayoutError> {
pub const fn repeat_packed(&self, n: usize) -> Result<Self, LayoutError> {
let size = self.size().checked_mul(n).ok_or(LayoutError)?;
// The safe constructor is called here to enforce the isize size limit.
Layout::from_size_alignment(size, self.align)
Expand All @@ -410,8 +418,9 @@ impl Layout {
///
/// On arithmetic overflow, returns `LayoutError`.
#[unstable(feature = "alloc_layout_extra", issue = "55724")]
#[rustc_const_unstable(feature = "const_alloc_layout", issue = "67521")]
#[inline]
pub fn extend_packed(&self, next: Self) -> Result<Self, LayoutError> {
pub const fn extend_packed(&self, next: Self) -> Result<Self, LayoutError> {
let new_size = self.size().checked_add(next.size()).ok_or(LayoutError)?;
// The safe constructor is called here to enforce the isize size limit.
Layout::from_size_alignment(new_size, self.align)
Expand All @@ -422,13 +431,18 @@ impl Layout {
/// On arithmetic overflow or when the total size would exceed
/// `isize::MAX`, returns `LayoutError`.
#[stable(feature = "alloc_layout_manipulation", since = "1.44.0")]
#[rustc_const_unstable(feature = "const_alloc_layout", issue = "67521")]
#[inline]
pub fn array<T>(n: usize) -> Result<Self, LayoutError> {
pub const fn array<T>(n: usize) -> Result<Self, LayoutError> {
// Reduce the amount of code we need to monomorphize per `T`.
return inner(mem::size_of::<T>(), Alignment::of::<T>(), n);

#[inline]
fn inner(element_size: usize, align: Alignment, n: usize) -> Result<Layout, LayoutError> {
const fn inner(
element_size: usize,
align: Alignment,
n: usize,
) -> Result<Layout, LayoutError> {
// We need to check two things about the size:
// - That the total size won't overflow a `usize`, and
// - That the total size still fits in an `isize`.
Expand Down
4 changes: 4 additions & 0 deletions library/core/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -98,6 +98,8 @@
// Library features:
#![feature(const_align_offset)]
#![feature(const_align_of_val)]
#![feature(const_align_of_val_raw)]
#![feature(const_alloc_layout)]
#![feature(const_arguments_as_str)]
#![feature(const_array_into_iter_constructors)]
#![feature(const_bigint_helper_methods)]
Expand Down Expand Up @@ -137,6 +139,7 @@
#![feature(const_ptr_write)]
#![feature(const_raw_ptr_comparison)]
#![feature(const_size_of_val)]
#![feature(const_size_of_val_raw)]
#![feature(const_slice_from_raw_parts_mut)]
#![feature(const_slice_ptr_len)]
#![feature(const_slice_split_at_mut)]
Expand All @@ -151,6 +154,7 @@
#![feature(const_unsafecell_get_mut)]
#![feature(const_waker)]
#![feature(core_panic)]
#![cfg_attr(not(bootstrap), feature(derive_const))]
#![feature(duration_consts_float)]
#![feature(maybe_uninit_uninit_array)]
#![feature(ptr_alignment_type)]
Expand Down
24 changes: 17 additions & 7 deletions library/core/src/ptr/alignment.rs
Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,9 @@ use crate::{cmp, fmt, hash, mem, num};
/// Note that particularly large alignments, while representable in this type,
/// are likely not to be supported by actual allocators and linkers.
#[unstable(feature = "ptr_alignment_type", issue = "102070")]
#[derive(Copy, Clone, Eq, PartialEq)]
#[derive(Copy, Clone, Eq)]
#[cfg_attr(bootstrap, derive(PartialEq))]
#[cfg_attr(not(bootstrap), derive_const(PartialEq))]
#[repr(transparent)]
pub struct Alignment(AlignmentEnum);

Expand Down Expand Up @@ -167,16 +169,18 @@ impl From<Alignment> for usize {
}
}

#[rustc_const_unstable(feature = "const_alloc_layout", issue = "67521")]
#[unstable(feature = "ptr_alignment_type", issue = "102070")]
impl cmp::Ord for Alignment {
impl const cmp::Ord for Alignment {
#[inline]
fn cmp(&self, other: &Self) -> cmp::Ordering {
self.as_nonzero().cmp(&other.as_nonzero())
self.as_nonzero().get().cmp(&other.as_nonzero().get())
}
}

#[rustc_const_unstable(feature = "const_alloc_layout", issue = "67521")]
#[unstable(feature = "ptr_alignment_type", issue = "102070")]
impl cmp::PartialOrd for Alignment {
impl const cmp::PartialOrd for Alignment {
#[inline]
fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
Some(self.cmp(other))
Expand All @@ -198,7 +202,9 @@ type AlignmentEnum = AlignmentEnum32;
#[cfg(target_pointer_width = "64")]
type AlignmentEnum = AlignmentEnum64;

#[derive(Copy, Clone, Eq, PartialEq)]
#[derive(Copy, Clone, Eq)]
#[cfg_attr(bootstrap, derive(PartialEq))]
#[cfg_attr(not(bootstrap), derive_const(PartialEq))]
#[repr(u16)]
enum AlignmentEnum16 {
_Align1Shl0 = 1 << 0,
Expand All @@ -219,7 +225,9 @@ enum AlignmentEnum16 {
_Align1Shl15 = 1 << 15,
}

#[derive(Copy, Clone, Eq, PartialEq)]
#[derive(Copy, Clone, Eq)]
#[cfg_attr(bootstrap, derive(PartialEq))]
#[cfg_attr(not(bootstrap), derive_const(PartialEq))]
#[repr(u32)]
enum AlignmentEnum32 {
_Align1Shl0 = 1 << 0,
Expand Down Expand Up @@ -256,7 +264,9 @@ enum AlignmentEnum32 {
_Align1Shl31 = 1 << 31,
}

#[derive(Copy, Clone, Eq, PartialEq)]
#[derive(Copy, Clone, Eq)]
#[cfg_attr(bootstrap, derive(PartialEq))]
#[cfg_attr(not(bootstrap), derive_const(PartialEq))]
#[repr(u64)]
enum AlignmentEnum64 {
_Align1Shl0 = 1 << 0,
Expand Down

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