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Auto merge of #102795 - lukas-code:constify-is-aligned-via-align-offset, r=oli-obk

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Constify `is_aligned` via `align_offset`

Alternative to https://github.com/rust-lang/rust/pull/102753

Make `align_offset` work in const eval (and not always return `usize::MAX`) and then use that to constify `is_aligned{_to}`.

Tracking Issue: https://github.com/rust-lang/rust/issues/104203
This commit is contained in:
bors 2022-11-19 18:57:39 +00:00
commit c5d82ed7a4
11 changed files with 986 additions and 99 deletions
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188
compiler/rustc_const_eval/src/const_eval/machine.rs
View file

@ -1,8 +1,12 @@
use rustc_hir::def::DefKind;
use rustc_hir::LangItem;
use rustc_middle::mir;
use rustc_middle::mir::interpret::PointerArithmetic;
use rustc_middle::ty::layout::FnAbiOf;
use rustc_middle::ty::{self, Ty, TyCtxt};
use std::borrow::Borrow;
use std::hash::Hash;
use std::ops::ControlFlow;
use rustc_data_structures::fx::FxIndexMap;
use rustc_data_structures::fx::IndexEntry;
@ -17,58 +21,12 @@ use rustc_target::abi::{Align, Size};
use rustc_target::spec::abi::Abi as CallAbi;
use crate::interpret::{
self, compile_time_machine, AllocId, ConstAllocation, Frame, ImmTy, InterpCx, InterpResult,
OpTy, PlaceTy, Pointer, Scalar, StackPopUnwind,
self, compile_time_machine, AllocId, ConstAllocation, FnVal, Frame, ImmTy, InterpCx,
InterpResult, OpTy, PlaceTy, Pointer, Scalar, StackPopUnwind,
};
use super::error::*;
impl<'mir, 'tcx> InterpCx<'mir, 'tcx, CompileTimeInterpreter<'mir, 'tcx>> {
/// "Intercept" a function call to a panic-related function
/// because we have something special to do for it.
/// If this returns successfully (`Ok`), the function should just be evaluated normally.
fn hook_special_const_fn(
&mut self,
instance: ty::Instance<'tcx>,
args: &[OpTy<'tcx>],
) -> InterpResult<'tcx, Option<ty::Instance<'tcx>>> {
// All `#[rustc_do_not_const_check]` functions should be hooked here.
let def_id = instance.def_id();
if Some(def_id) == self.tcx.lang_items().panic_display()
|| Some(def_id) == self.tcx.lang_items().begin_panic_fn()
{
// &str or &&str
assert!(args.len() == 1);
let mut msg_place = self.deref_operand(&args[0])?;
while msg_place.layout.ty.is_ref() {
msg_place = self.deref_operand(&msg_place.into())?;
}
let msg = Symbol::intern(self.read_str(&msg_place)?);
let span = self.find_closest_untracked_caller_location();
let (file, line, col) = self.location_triple_for_span(span);
return Err(ConstEvalErrKind::Panic { msg, file, line, col }.into());
} else if Some(def_id) == self.tcx.lang_items().panic_fmt() {
// For panic_fmt, call const_panic_fmt instead.
if let Some(const_panic_fmt) = self.tcx.lang_items().const_panic_fmt() {
return Ok(Some(
ty::Instance::resolve(
*self.tcx,
ty::ParamEnv::reveal_all(),
const_panic_fmt,
self.tcx.intern_substs(&[]),
)
.unwrap()
.unwrap(),
));
}
}
Ok(None)
}
}
/// Extra machine state for CTFE, and the Machine instance
pub struct CompileTimeInterpreter<'mir, 'tcx> {
/// For now, the number of terminators that can be evaluated before we throw a resource
@ -191,6 +149,125 @@ impl interpret::MayLeak for ! {
}
impl<'mir, 'tcx: 'mir> CompileTimeEvalContext<'mir, 'tcx> {
/// "Intercept" a function call, because we have something special to do for it.
/// All `#[rustc_do_not_const_check]` functions should be hooked here.
/// If this returns `Some` function, which may be `instance` or a different function with
/// compatible arguments, then evaluation should continue with that function.
/// If this returns `None`, the function call has been handled and the function has returned.
fn hook_special_const_fn(
&mut self,
instance: ty::Instance<'tcx>,
args: &[OpTy<'tcx>],
dest: &PlaceTy<'tcx>,
ret: Option<mir::BasicBlock>,
) -> InterpResult<'tcx, Option<ty::Instance<'tcx>>> {
let def_id = instance.def_id();
if Some(def_id) == self.tcx.lang_items().panic_display()
|| Some(def_id) == self.tcx.lang_items().begin_panic_fn()
{
// &str or &&str
assert!(args.len() == 1);
let mut msg_place = self.deref_operand(&args[0])?;
while msg_place.layout.ty.is_ref() {
msg_place = self.deref_operand(&msg_place.into())?;
}
let msg = Symbol::intern(self.read_str(&msg_place)?);
let span = self.find_closest_untracked_caller_location();
let (file, line, col) = self.location_triple_for_span(span);
return Err(ConstEvalErrKind::Panic { msg, file, line, col }.into());
} else if Some(def_id) == self.tcx.lang_items().panic_fmt() {
// For panic_fmt, call const_panic_fmt instead.
let const_def_id = self.tcx.require_lang_item(LangItem::ConstPanicFmt, None);
let new_instance = ty::Instance::resolve(
*self.tcx,
ty::ParamEnv::reveal_all(),
const_def_id,
instance.substs,
)
.unwrap()
.unwrap();
return Ok(Some(new_instance));
} else if Some(def_id) == self.tcx.lang_items().align_offset_fn() {
// For align_offset, we replace the function call if the pointer has no address.
match self.align_offset(instance, args, dest, ret)? {
ControlFlow::Continue(()) => return Ok(Some(instance)),
ControlFlow::Break(()) => return Ok(None),
}
}
Ok(Some(instance))
}
/// `align_offset(ptr, target_align)` needs special handling in const eval, because the pointer
/// may not have an address.
///
/// If `ptr` does have a known address, then we return `CONTINUE` and the function call should
/// proceed as normal.
///
/// If `ptr` doesn't have an address, but its underlying allocation's alignment is at most
/// `target_align`, then we call the function again with an dummy address relative to the
/// allocation.
///
/// If `ptr` doesn't have an address and `target_align` is stricter than the underlying
/// allocation's alignment, then we return `usize::MAX` immediately.
fn align_offset(
&mut self,
instance: ty::Instance<'tcx>,
args: &[OpTy<'tcx>],
dest: &PlaceTy<'tcx>,
ret: Option<mir::BasicBlock>,
) -> InterpResult<'tcx, ControlFlow<()>> {
assert_eq!(args.len(), 2);
let ptr = self.read_pointer(&args[0])?;
let target_align = self.read_scalar(&args[1])?.to_machine_usize(self)?;
if !target_align.is_power_of_two() {
throw_ub_format!("`align_offset` called with non-power-of-two align: {}", target_align);
}
match self.ptr_try_get_alloc_id(ptr) {
Ok((alloc_id, offset, _extra)) => {
let (_size, alloc_align, _kind) = self.get_alloc_info(alloc_id);
if target_align <= alloc_align.bytes() {
// Extract the address relative to the allocation base that is definitely
// sufficiently aligned and call `align_offset` again.
let addr = ImmTy::from_uint(offset.bytes(), args[0].layout).into();
let align = ImmTy::from_uint(target_align, args[1].layout).into();
let fn_abi = self.fn_abi_of_instance(instance, ty::List::empty())?;
// We replace the entire entire function call with a "tail call".
// Note that this happens before the frame of the original function
// is pushed on the stack.
self.eval_fn_call(
FnVal::Instance(instance),
(CallAbi::Rust, fn_abi),
&[addr, align],
/* with_caller_location = */ false,
dest,
ret,
StackPopUnwind::NotAllowed,
)?;
Ok(ControlFlow::BREAK)
} else {
// Not alignable in const, return `usize::MAX`.
let usize_max = Scalar::from_machine_usize(self.machine_usize_max(), self);
self.write_scalar(usize_max, dest)?;
self.return_to_block(ret)?;
Ok(ControlFlow::BREAK)
}
}
Err(_addr) => {
// The pointer has an address, continue with function call.
Ok(ControlFlow::CONTINUE)
}
}
}
/// See documentation on the `ptr_guaranteed_cmp` intrinsic.
fn guaranteed_cmp(&mut self, a: Scalar, b: Scalar) -> InterpResult<'tcx, u8> {
Ok(match (a, b) {
@ -271,8 +348,8 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
instance: ty::Instance<'tcx>,
_abi: CallAbi,
args: &[OpTy<'tcx>],
_dest: &PlaceTy<'tcx>,
_ret: Option<mir::BasicBlock>,
dest: &PlaceTy<'tcx>,
ret: Option<mir::BasicBlock>,
_unwind: StackPopUnwind, // unwinding is not supported in consts
) -> InterpResult<'tcx, Option<(&'mir mir::Body<'tcx>, ty::Instance<'tcx>)>> {
debug!("find_mir_or_eval_fn: {:?}", instance);
@ -291,7 +368,11 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
}
}
if let Some(new_instance) = ecx.hook_special_const_fn(instance, args)? {
let Some(new_instance) = ecx.hook_special_const_fn(instance, args, dest, ret)? else {
return Ok(None);
};
if new_instance != instance {
// We call another const fn instead.
// However, we return the *original* instance to make backtraces work out
// (and we hope this does not confuse the FnAbi checks too much).
@ -300,13 +381,14 @@ impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir,
new_instance,
_abi,
args,
_dest,
_ret,
dest,
ret,
_unwind,
)?
.map(|(body, _instance)| (body, instance)));
}
}
// This is a const fn. Call it.
Ok(Some((ecx.load_mir(instance.def, None)?, instance)))
}

5
compiler/rustc_const_eval/src/interpret/intrinsics.rs
View file

@ -243,6 +243,11 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
let discr_val = self.read_discriminant(&place.into())?.0;
self.write_scalar(discr_val, dest)?;
}
sym::exact_div => {
let l = self.read_immediate(&args[0])?;
let r = self.read_immediate(&args[1])?;
self.exact_div(&l, &r, dest)?;
}
sym::unchecked_shl
| sym::unchecked_shr
| sym::unchecked_add

1
library/core/src/intrinsics.rs
View file

@ -1851,6 +1851,7 @@ extern "rust-intrinsic" {
/// `x % y != 0` or `y == 0` or `x == T::MIN && y == -1`
///
/// This intrinsic does not have a stable counterpart.
#[rustc_const_unstable(feature = "const_exact_div", issue = "none")]
pub fn exact_div<T: Copy>(x: T, y: T) -> T;
/// Performs an unchecked division, resulting in undefined behavior

2
library/core/src/lib.rs
View file

@ -109,6 +109,7 @@
#![feature(const_cmp)]
#![feature(const_discriminant)]
#![feature(const_eval_select)]
#![feature(const_exact_div)]
#![feature(const_float_bits_conv)]
#![feature(const_float_classify)]
#![feature(const_fmt_arguments_new)]
@ -129,6 +130,7 @@
#![feature(const_option)]
#![feature(const_option_ext)]
#![feature(const_pin)]
#![feature(const_pointer_is_aligned)]
#![feature(const_ptr_sub_ptr)]
#![feature(const_replace)]
#![feature(const_result_drop)]

260
library/core/src/ptr/const_ptr.rs
View file

@ -1320,6 +1320,8 @@ impl<T: ?Sized> *const T {
/// }
/// # }
/// ```
#[must_use]
#[inline]
#[stable(feature = "align_offset", since = "1.36.0")]
#[rustc_const_unstable(feature = "const_align_offset", issue = "90962")]
pub const fn align_offset(self, align: usize) -> usize
@ -1330,32 +1332,149 @@ impl<T: ?Sized> *const T {
panic!("align_offset: align is not a power-of-two");
}
fn rt_impl<T>(p: *const T, align: usize) -> usize {
#[cfg(bootstrap)]
{
fn rt_impl<T>(p: *const T, align: usize) -> usize {
// SAFETY: `align` has been checked to be a power of 2 above
unsafe { align_offset(p, align) }
}
const fn ctfe_impl<T>(_: *const T, _: usize) -> usize {
usize::MAX
}
// SAFETY:
// It is permissible for `align_offset` to always return `usize::MAX`,
// algorithm correctness can not depend on `align_offset` returning non-max values.
//
// As such the behaviour can't change after replacing `align_offset` with `usize::MAX`, only performance can.
unsafe { intrinsics::const_eval_select((self, align), ctfe_impl, rt_impl) }
}
#[cfg(not(bootstrap))]
{
// SAFETY: `align` has been checked to be a power of 2 above
unsafe { align_offset(p, align) }
unsafe { align_offset(self, align) }
}
const fn ctfe_impl<T>(_: *const T, _: usize) -> usize {
usize::MAX
}
// SAFETY:
// It is permissible for `align_offset` to always return `usize::MAX`,
// algorithm correctness can not depend on `align_offset` returning non-max values.
//
// As such the behaviour can't change after replacing `align_offset` with `usize::MAX`, only performance can.
unsafe { intrinsics::const_eval_select((self, align), ctfe_impl, rt_impl) }
}
/// Returns whether the pointer is properly aligned for `T`.
///
/// # Examples
///
/// Basic usage:
/// ```
/// #![feature(pointer_is_aligned)]
/// #![feature(pointer_byte_offsets)]
///
/// // On some platforms, the alignment of i32 is less than 4.
/// #[repr(align(4))]
/// struct AlignedI32(i32);
///
/// let data = AlignedI32(42);
/// let ptr = &data as *const AlignedI32;
///
/// assert!(ptr.is_aligned());
/// assert!(!ptr.wrapping_byte_add(1).is_aligned());
/// ```
///
/// # At compiletime
/// **Note: Alignment at compiletime is experimental and subject to change. See the
/// [tracking issue] for details.**
///
/// At compiletime, the compiler may not know where a value will end up in memory.
/// Calling this function on a pointer created from a reference at compiletime will only
/// return `true` if the pointer is guaranteed to be aligned. This means that the pointer
/// is never aligned if cast to a type with a stricter alignment than the reference's
/// underlying allocation.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
///
/// // On some platforms, the alignment of primitives is less than their size.
/// #[repr(align(4))]
/// struct AlignedI32(i32);
/// #[repr(align(8))]
/// struct AlignedI64(i64);
///
/// const _: () = {
/// let data = AlignedI32(42);
/// let ptr = &data as *const AlignedI32;
/// assert!(ptr.is_aligned());
///
/// // At runtime either `ptr1` or `ptr2` would be aligned, but at compiletime neither is aligned.
/// let ptr1 = ptr.cast::<AlignedI64>();
/// let ptr2 = ptr.wrapping_add(1).cast::<AlignedI64>();
/// assert!(!ptr1.is_aligned());
/// assert!(!ptr2.is_aligned());
/// };
/// ```
///
/// Due to this behavior, it is possible that a runtime pointer derived from a compiletime
/// pointer is aligned, even if the compiletime pointer wasn't aligned.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
///
/// // On some platforms, the alignment of primitives is less than their size.
/// #[repr(align(4))]
/// struct AlignedI32(i32);
/// #[repr(align(8))]
/// struct AlignedI64(i64);
///
/// // At compiletime, neither `COMPTIME_PTR` nor `COMPTIME_PTR + 1` is aligned.
/// const COMPTIME_PTR: *const AlignedI32 = &AlignedI32(42);
/// const _: () = assert!(!COMPTIME_PTR.cast::<AlignedI64>().is_aligned());
/// const _: () = assert!(!COMPTIME_PTR.wrapping_add(1).cast::<AlignedI64>().is_aligned());
///
/// // At runtime, either `runtime_ptr` or `runtime_ptr + 1` is aligned.
/// let runtime_ptr = COMPTIME_PTR;
/// assert_ne!(
/// runtime_ptr.cast::<AlignedI64>().is_aligned(),
/// runtime_ptr.wrapping_add(1).cast::<AlignedI64>().is_aligned(),
/// );
/// ```
///
/// If a pointer is created from a fixed address, this function behaves the same during
/// runtime and compiletime.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
///
/// // On some platforms, the alignment of primitives is less than their size.
/// #[repr(align(4))]
/// struct AlignedI32(i32);
/// #[repr(align(8))]
/// struct AlignedI64(i64);
///
/// const _: () = {
/// let ptr = 40 as *const AlignedI32;
/// assert!(ptr.is_aligned());
///
/// // For pointers with a known address, runtime and compiletime behavior are identical.
/// let ptr1 = ptr.cast::<AlignedI64>();
/// let ptr2 = ptr.wrapping_add(1).cast::<AlignedI64>();
/// assert!(ptr1.is_aligned());
/// assert!(!ptr2.is_aligned());
/// };
/// ```
///
/// [tracking issue]: https://github.com/rust-lang/rust/issues/104203
#[must_use]
#[inline]
#[unstable(feature = "pointer_is_aligned", issue = "96284")]
pub fn is_aligned(self) -> bool
#[rustc_const_unstable(feature = "const_pointer_is_aligned", issue = "104203")]
pub const fn is_aligned(self) -> bool
where
T: Sized,
{
self.is_aligned_to(core::mem::align_of::<T>())
self.is_aligned_to(mem::align_of::<T>())
}
/// Returns whether the pointer is aligned to `align`.
@ -1366,16 +1485,121 @@ impl<T: ?Sized> *const T {
/// # Panics
///
/// The function panics if `align` is not a power-of-two (this includes 0).
///
/// # Examples
///
/// Basic usage:
/// ```
/// #![feature(pointer_is_aligned)]
/// #![feature(pointer_byte_offsets)]
///
/// // On some platforms, the alignment of i32 is less than 4.
/// #[repr(align(4))]
/// struct AlignedI32(i32);
///
/// let data = AlignedI32(42);
/// let ptr = &data as *const AlignedI32;
///
/// assert!(ptr.is_aligned_to(1));
/// assert!(ptr.is_aligned_to(2));
/// assert!(ptr.is_aligned_to(4));
///
/// assert!(ptr.wrapping_byte_add(2).is_aligned_to(2));
/// assert!(!ptr.wrapping_byte_add(2).is_aligned_to(4));
///
/// assert_ne!(ptr.is_aligned_to(8), ptr.wrapping_add(1).is_aligned_to(8));
/// ```
///
/// # At compiletime
/// **Note: Alignment at compiletime is experimental and subject to change. See the
/// [tracking issue] for details.**
///
/// At compiletime, the compiler may not know where a value will end up in memory.
/// Calling this function on a pointer created from a reference at compiletime will only
/// return `true` if the pointer is guaranteed to be aligned. This means that the pointer
/// cannot be stricter aligned than the reference's underlying allocation.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
///
/// // On some platforms, the alignment of i32 is less than 4.
/// #[repr(align(4))]
/// struct AlignedI32(i32);
///
/// const _: () = {
/// let data = AlignedI32(42);
/// let ptr = &data as *const AlignedI32;
///
/// assert!(ptr.is_aligned_to(1));
/// assert!(ptr.is_aligned_to(2));
/// assert!(ptr.is_aligned_to(4));
///
/// // At compiletime, we know for sure that the pointer isn't aligned to 8.
/// assert!(!ptr.is_aligned_to(8));
/// assert!(!ptr.wrapping_add(1).is_aligned_to(8));
/// };
/// ```
///
/// Due to this behavior, it is possible that a runtime pointer derived from a compiletime
/// pointer is aligned, even if the compiletime pointer wasn't aligned.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
///
/// // On some platforms, the alignment of i32 is less than 4.
/// #[repr(align(4))]
/// struct AlignedI32(i32);
///
/// // At compiletime, neither `COMPTIME_PTR` nor `COMPTIME_PTR + 1` is aligned.
/// const COMPTIME_PTR: *const AlignedI32 = &AlignedI32(42);
/// const _: () = assert!(!COMPTIME_PTR.is_aligned_to(8));
/// const _: () = assert!(!COMPTIME_PTR.wrapping_add(1).is_aligned_to(8));
///
/// // At runtime, either `runtime_ptr` or `runtime_ptr + 1` is aligned.
/// let runtime_ptr = COMPTIME_PTR;
/// assert_ne!(
/// runtime_ptr.is_aligned_to(8),
/// runtime_ptr.wrapping_add(1).is_aligned_to(8),
/// );
/// ```
///
/// If a pointer is created from a fixed address, this function behaves the same during
/// runtime and compiletime.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
///
/// const _: () = {
/// let ptr = 40 as *const u8;
/// assert!(ptr.is_aligned_to(1));
/// assert!(ptr.is_aligned_to(2));
/// assert!(ptr.is_aligned_to(4));
/// assert!(ptr.is_aligned_to(8));
/// assert!(!ptr.is_aligned_to(16));
/// };
/// ```
///
/// [tracking issue]: https://github.com/rust-lang/rust/issues/104203
#[must_use]
#[inline]
#[unstable(feature = "pointer_is_aligned", issue = "96284")]
pub fn is_aligned_to(self, align: usize) -> bool {
#[rustc_const_unstable(feature = "const_pointer_is_aligned", issue = "104203")]
pub const fn is_aligned_to(self, align: usize) -> bool {
if !align.is_power_of_two() {
panic!("is_aligned_to: align is not a power-of-two");
}
// Cast is needed for `T: !Sized`
self.cast::<u8>().addr() & align - 1 == 0
// We can't use the address of `self` in a `const fn`, so we use `align_offset` instead.
// The cast to `()` is used to
// 1. deal with fat pointers; and
// 2. ensure that `align_offset` doesn't actually try to compute an offset.
self.cast::<()>().align_offset(align) == 0
}
}

20
library/core/src/ptr/mod.rs
View file

@ -1574,10 +1574,14 @@ pub unsafe fn write_volatile<T>(dst: *mut T, src: T) {
/// Align pointer `p`.
///
/// Calculate offset (in terms of elements of `stride` stride) that has to be applied
/// Calculate offset (in terms of elements of `size_of::<T>()` stride) that has to be applied
/// to pointer `p` so that pointer `p` would get aligned to `a`.
///
/// Note: This implementation has been carefully tailored to not panic. It is UB for this to panic.
/// # Safety
/// `a` must be a power of two.
///
/// # Notes
/// This implementation has been carefully tailored to not panic. It is UB for this to panic.
/// The only real change that can be made here is change of `INV_TABLE_MOD_16` and associated
/// constants.
///
@ -1587,7 +1591,7 @@ pub unsafe fn write_volatile<T>(dst: *mut T, src: T) {
///
/// Any questions go to @nagisa.
#[lang = "align_offset"]
pub(crate) unsafe fn align_offset<T: Sized>(p: *const T, a: usize) -> usize {
pub(crate) const unsafe fn align_offset<T: Sized>(p: *const T, a: usize) -> usize {
// FIXME(#75598): Direct use of these intrinsics improves codegen significantly at opt-level <=
// 1, where the method versions of these operations are not inlined.
use intrinsics::{
@ -1604,7 +1608,7 @@ pub(crate) unsafe fn align_offset<T: Sized>(p: *const T, a: usize) -> usize {
///
/// Implementation of this function shall not panic. Ever.
#[inline]
unsafe fn mod_inv(x: usize, m: usize) -> usize {
const unsafe fn mod_inv(x: usize, m: usize) -> usize {
/// Multiplicative modular inverse table modulo 2⁴ = 16.
///
/// Note, that this table does not contain values where inverse does not exist (i.e., for
@ -1646,8 +1650,14 @@ pub(crate) unsafe fn align_offset<T: Sized>(p: *const T, a: usize) -> usize {
inverse & m_minus_one
}
let addr = p.addr();
let stride = mem::size_of::<T>();
// SAFETY: This is just an inlined `p.addr()` (which is not
// a `const fn` so we cannot call it).
// During const eval, we hook this function to ensure that the pointer never
// has provenance, making this sound.
let addr: usize = unsafe { mem::transmute(p) };
// SAFETY: `a` is a power-of-two, therefore non-zero.
let a_minus_one = unsafe { unchecked_sub(a, 1) };

264
library/core/src/ptr/mut_ptr.rs
View file

@ -1588,6 +1588,8 @@ impl<T: ?Sized> *mut T {
/// }
/// # }
/// ```
#[must_use]
#[inline]
#[stable(feature = "align_offset", since = "1.36.0")]
#[rustc_const_unstable(feature = "const_align_offset", issue = "90962")]
pub const fn align_offset(self, align: usize) -> usize
@ -1598,32 +1600,151 @@ impl<T: ?Sized> *mut T {
panic!("align_offset: align is not a power-of-two");
}
fn rt_impl<T>(p: *mut T, align: usize) -> usize {
#[cfg(bootstrap)]
{
fn rt_impl<T>(p: *mut T, align: usize) -> usize {
// SAFETY: `align` has been checked to be a power of 2 above
unsafe { align_offset(p, align) }
}
const fn ctfe_impl<T>(_: *mut T, _: usize) -> usize {
usize::MAX
}
// SAFETY:
// It is permissible for `align_offset` to always return `usize::MAX`,
// algorithm correctness can not depend on `align_offset` returning non-max values.
//
// As such the behaviour can't change after replacing `align_offset` with `usize::MAX`, only performance can.
unsafe { intrinsics::const_eval_select((self, align), ctfe_impl, rt_impl) }
}
#[cfg(not(bootstrap))]
{
// SAFETY: `align` has been checked to be a power of 2 above
unsafe { align_offset(p, align) }
unsafe { align_offset(self, align) }
}
const fn ctfe_impl<T>(_: *mut T, _: usize) -> usize {
usize::MAX
}
// SAFETY:
// It is permissible for `align_offset` to always return `usize::MAX`,
// algorithm correctness can not depend on `align_offset` returning non-max values.
//
// As such the behaviour can't change after replacing `align_offset` with `usize::MAX`, only performance can.
unsafe { intrinsics::const_eval_select((self, align), ctfe_impl, rt_impl) }
}
/// Returns whether the pointer is properly aligned for `T`.
///
/// # Examples
///
/// Basic usage:
/// ```
/// #![feature(pointer_is_aligned)]
/// #![feature(pointer_byte_offsets)]
///
/// // On some platforms, the alignment of i32 is less than 4.
/// #[repr(align(4))]
/// struct AlignedI32(i32);
///
/// let mut data = AlignedI32(42);
/// let ptr = &mut data as *mut AlignedI32;
///
/// assert!(ptr.is_aligned());
/// assert!(!ptr.wrapping_byte_add(1).is_aligned());
/// ```
///
/// # At compiletime
/// **Note: Alignment at compiletime is experimental and subject to change. See the
/// [tracking issue] for details.**
///
/// At compiletime, the compiler may not know where a value will end up in memory.
/// Calling this function on a pointer created from a reference at compiletime will only
/// return `true` if the pointer is guaranteed to be aligned. This means that the pointer
/// is never aligned if cast to a type with a stricter alignment than the reference's
/// underlying allocation.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
/// #![feature(const_mut_refs)]
///
/// // On some platforms, the alignment of primitives is less than their size.
/// #[repr(align(4))]
/// struct AlignedI32(i32);
/// #[repr(align(8))]
/// struct AlignedI64(i64);
///
/// const _: () = {
/// let mut data = AlignedI32(42);
/// let ptr = &mut data as *mut AlignedI32;
/// assert!(ptr.is_aligned());
///
/// // At runtime either `ptr1` or `ptr2` would be aligned, but at compiletime neither is aligned.
/// let ptr1 = ptr.cast::<AlignedI64>();
/// let ptr2 = ptr.wrapping_add(1).cast::<AlignedI64>();
/// assert!(!ptr1.is_aligned());
/// assert!(!ptr2.is_aligned());
/// };
/// ```
///
/// Due to this behavior, it is possible that a runtime pointer derived from a compiletime
/// pointer is aligned, even if the compiletime pointer wasn't aligned.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
///
/// // On some platforms, the alignment of primitives is less than their size.
/// #[repr(align(4))]
/// struct AlignedI32(i32);
/// #[repr(align(8))]
/// struct AlignedI64(i64);
///
/// // At compiletime, neither `COMPTIME_PTR` nor `COMPTIME_PTR + 1` is aligned.
/// // Also, note that mutable references are not allowed in the final value of constants.
/// const COMPTIME_PTR: *mut AlignedI32 = (&AlignedI32(42) as *const AlignedI32).cast_mut();
/// const _: () = assert!(!COMPTIME_PTR.cast::<AlignedI64>().is_aligned());
/// const _: () = assert!(!COMPTIME_PTR.wrapping_add(1).cast::<AlignedI64>().is_aligned());
///
/// // At runtime, either `runtime_ptr` or `runtime_ptr + 1` is aligned.
/// let runtime_ptr = COMPTIME_PTR;
/// assert_ne!(
/// runtime_ptr.cast::<AlignedI64>().is_aligned(),
/// runtime_ptr.wrapping_add(1).cast::<AlignedI64>().is_aligned(),
/// );
/// ```
///
/// If a pointer is created from a fixed address, this function behaves the same during
/// runtime and compiletime.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
///
/// // On some platforms, the alignment of primitives is less than their size.
/// #[repr(align(4))]
/// struct AlignedI32(i32);
/// #[repr(align(8))]
/// struct AlignedI64(i64);
///
/// const _: () = {
/// let ptr = 40 as *mut AlignedI32;
/// assert!(ptr.is_aligned());
///
/// // For pointers with a known address, runtime and compiletime behavior are identical.
/// let ptr1 = ptr.cast::<AlignedI64>();
/// let ptr2 = ptr.wrapping_add(1).cast::<AlignedI64>();
/// assert!(ptr1.is_aligned());
/// assert!(!ptr2.is_aligned());
/// };
/// ```
///
/// [tracking issue]: https://github.com/rust-lang/rust/issues/104203
#[must_use]
#[inline]
#[unstable(feature = "pointer_is_aligned", issue = "96284")]
pub fn is_aligned(self) -> bool
#[rustc_const_unstable(feature = "const_pointer_is_aligned", issue = "104203")]
pub const fn is_aligned(self) -> bool
where
T: Sized,
{
self.is_aligned_to(core::mem::align_of::<T>())
self.is_aligned_to(mem::align_of::<T>())
}
/// Returns whether the pointer is aligned to `align`.
@ -1634,16 +1755,123 @@ impl<T: ?Sized> *mut T {
/// # Panics
///
/// The function panics if `align` is not a power-of-two (this includes 0).
///
/// # Examples
///
/// Basic usage:
/// ```
/// #![feature(pointer_is_aligned)]
/// #![feature(pointer_byte_offsets)]
///
/// // On some platforms, the alignment of i32 is less than 4.
/// #[repr(align(4))]
/// struct AlignedI32(i32);
///
/// let mut data = AlignedI32(42);
/// let ptr = &mut data as *mut AlignedI32;
///
/// assert!(ptr.is_aligned_to(1));
/// assert!(ptr.is_aligned_to(2));
/// assert!(ptr.is_aligned_to(4));
///
/// assert!(ptr.wrapping_byte_add(2).is_aligned_to(2));
/// assert!(!ptr.wrapping_byte_add(2).is_aligned_to(4));
///
/// assert_ne!(ptr.is_aligned_to(8), ptr.wrapping_add(1).is_aligned_to(8));
/// ```
///
/// # At compiletime
/// **Note: Alignment at compiletime is experimental and subject to change. See the
/// [tracking issue] for details.**
///
/// At compiletime, the compiler may not know where a value will end up in memory.
/// Calling this function on a pointer created from a reference at compiletime will only
/// return `true` if the pointer is guaranteed to be aligned. This means that the pointer
/// cannot be stricter aligned than the reference's underlying allocation.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
/// #![feature(const_mut_refs)]
///
/// // On some platforms, the alignment of i32 is less than 4.
/// #[repr(align(4))]
/// struct AlignedI32(i32);
///
/// const _: () = {
/// let mut data = AlignedI32(42);
/// let ptr = &mut data as *mut AlignedI32;
///
/// assert!(ptr.is_aligned_to(1));
/// assert!(ptr.is_aligned_to(2));
/// assert!(ptr.is_aligned_to(4));
///
/// // At compiletime, we know for sure that the pointer isn't aligned to 8.
/// assert!(!ptr.is_aligned_to(8));
/// assert!(!ptr.wrapping_add(1).is_aligned_to(8));
/// };
/// ```
///
/// Due to this behavior, it is possible that a runtime pointer derived from a compiletime
/// pointer is aligned, even if the compiletime pointer wasn't aligned.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
///
/// // On some platforms, the alignment of i32 is less than 4.
/// #[repr(align(4))]
/// struct AlignedI32(i32);
///
/// // At compiletime, neither `COMPTIME_PTR` nor `COMPTIME_PTR + 1` is aligned.
/// // Also, note that mutable references are not allowed in the final value of constants.
/// const COMPTIME_PTR: *mut AlignedI32 = (&AlignedI32(42) as *const AlignedI32).cast_mut();
/// const _: () = assert!(!COMPTIME_PTR.is_aligned_to(8));
/// const _: () = assert!(!COMPTIME_PTR.wrapping_add(1).is_aligned_to(8));
///
/// // At runtime, either `runtime_ptr` or `runtime_ptr + 1` is aligned.
/// let runtime_ptr = COMPTIME_PTR;
/// assert_ne!(
/// runtime_ptr.is_aligned_to(8),
/// runtime_ptr.wrapping_add(1).is_aligned_to(8),
/// );
/// ```
///
/// If a pointer is created from a fixed address, this function behaves the same during
/// runtime and compiletime.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
///
/// const _: () = {
/// let ptr = 40 as *mut u8;
/// assert!(ptr.is_aligned_to(1));
/// assert!(ptr.is_aligned_to(2));
/// assert!(ptr.is_aligned_to(4));
/// assert!(ptr.is_aligned_to(8));
/// assert!(!ptr.is_aligned_to(16));
/// };
/// ```
///
/// [tracking issue]: https://github.com/rust-lang/rust/issues/104203
#[must_use]
#[inline]
#[unstable(feature = "pointer_is_aligned", issue = "96284")]
pub fn is_aligned_to(self, align: usize) -> bool {
#[rustc_const_unstable(feature = "const_pointer_is_aligned", issue = "104203")]
pub const fn is_aligned_to(self, align: usize) -> bool {
if !align.is_power_of_two() {
panic!("is_aligned_to: align is not a power-of-two");
}
// Cast is needed for `T: !Sized`
self.cast::<u8>().addr() & align - 1 == 0
// We can't use the address of `self` in a `const fn`, so we use `align_offset` instead.
// The cast to `()` is used to
// 1. deal with fat pointers; and
// 2. ensure that `align_offset` doesn't actually try to compute an offset.
self.cast::<()>().align_offset(align) == 0
}
}

3
library/core/tests/lib.rs
View file

@ -4,6 +4,7 @@
#![feature(array_windows)]
#![feature(bigint_helper_methods)]
#![feature(cell_update)]
#![feature(const_align_offset)]
#![feature(const_assume)]
#![feature(const_align_of_val_raw)]
#![feature(const_black_box)]
@ -18,6 +19,7 @@
#![feature(const_nonnull_new)]
#![feature(const_num_from_num)]
#![feature(const_pointer_byte_offsets)]
#![feature(const_pointer_is_aligned)]
#![feature(const_ptr_as_ref)]
#![feature(const_ptr_read)]
#![feature(const_ptr_write)]
@ -81,6 +83,7 @@
#![feature(never_type)]
#![feature(unwrap_infallible)]
#![feature(pointer_byte_offsets)]
#![feature(pointer_is_aligned)]
#![feature(portable_simd)]
#![feature(ptr_metadata)]
#![feature(once_cell)]

279
library/core/tests/ptr.rs
View file

@ -358,6 +358,23 @@ fn align_offset_zst() {
}
}
#[test]
#[cfg(not(bootstrap))]
fn align_offset_zst_const() {
const {
// For pointers of stride = 0, the pointer is already aligned or it cannot be aligned at
// all, because no amount of elements will align the pointer.
let mut p = 1;
while p < 1024 {
assert!(ptr::invalid::<()>(p).align_offset(p) == 0);
if p != 1 {
assert!(ptr::invalid::<()>(p + 1).align_offset(p) == !0);
}
p = (p + 1).next_power_of_two();
}
}
}
#[test]
fn align_offset_stride_one() {
// For pointers of stride = 1, the pointer can always be aligned. The offset is equal to
@ -379,6 +396,26 @@ fn align_offset_stride_one() {
}
}
#[test]
#[cfg(not(bootstrap))]
fn align_offset_stride_one_const() {
const {
// For pointers of stride = 1, the pointer can always be aligned. The offset is equal to
// number of bytes.
let mut align = 1;
while align < 1024 {
let mut ptr = 1;
while ptr < 2 * align {
let expected = ptr % align;
let offset = if expected == 0 { 0 } else { align - expected };
assert!(ptr::invalid::<u8>(ptr).align_offset(align) == offset);
ptr += 1;
}
align = (align + 1).next_power_of_two();
}
}
}
#[test]
fn align_offset_various_strides() {
unsafe fn test_stride<T>(ptr: *const T, align: usize) -> bool {
@ -455,6 +492,182 @@ fn align_offset_various_strides() {
assert!(!x);
}
#[test]
#[cfg(not(bootstrap))]
fn align_offset_various_strides_const() {
const unsafe fn test_stride<T>(ptr: *const T, numptr: usize, align: usize) {
let mut expected = usize::MAX;
// Naive but definitely correct way to find the *first* aligned element of stride::<T>.
let mut el = 0;
while el < align {
if (numptr + el * ::std::mem::size_of::<T>()) % align == 0 {
expected = el;
break;
}
el += 1;
}
let got = ptr.align_offset(align);
assert!(got == expected);
}
const {
// For pointers of stride != 1, we verify the algorithm against the naivest possible
// implementation
let mut align = 1;
let limit = 32;
while align < limit {
let mut ptr = 1;
while ptr < 4 * align {
unsafe {
#[repr(packed)]
struct A3(u16, u8);
test_stride::<A3>(ptr::invalid::<A3>(ptr), ptr, align);
struct A4(u32);
test_stride::<A4>(ptr::invalid::<A4>(ptr), ptr, align);
#[repr(packed)]
struct A5(u32, u8);
test_stride::<A5>(ptr::invalid::<A5>(ptr), ptr, align);
#[repr(packed)]
struct A6(u32, u16);
test_stride::<A6>(ptr::invalid::<A6>(ptr), ptr, align);
#[repr(packed)]
struct A7(u32, u16, u8);
test_stride::<A7>(ptr::invalid::<A7>(ptr), ptr, align);
#[repr(packed)]
struct A8(u32, u32);
test_stride::<A8>(ptr::invalid::<A8>(ptr), ptr, align);
#[repr(packed)]
struct A9(u32, u32, u8);
test_stride::<A9>(ptr::invalid::<A9>(ptr), ptr, align);
#[repr(packed)]
struct A10(u32, u32, u16);
test_stride::<A10>(ptr::invalid::<A10>(ptr), ptr, align);
test_stride::<u32>(ptr::invalid::<u32>(ptr), ptr, align);
test_stride::<u128>(ptr::invalid::<u128>(ptr), ptr, align);
}
ptr += 1;
}
align = (align + 1).next_power_of_two();
}
}
}
#[test]
#[cfg(not(bootstrap))]
fn align_offset_with_provenance_const() {
const {
// On some platforms (e.g. msp430-none-elf), the alignment of `i32` is less than 4.
#[repr(align(4))]
struct AlignedI32(i32);
let data = AlignedI32(42);
// `stride % align == 0` (usual case)
let ptr: *const i32 = &data.0;
assert!(ptr.align_offset(1) == 0);
assert!(ptr.align_offset(2) == 0);
assert!(ptr.align_offset(4) == 0);
assert!(ptr.align_offset(8) == usize::MAX);
assert!(ptr.wrapping_byte_add(1).align_offset(1) == 0);
assert!(ptr.wrapping_byte_add(1).align_offset(2) == usize::MAX);
assert!(ptr.wrapping_byte_add(2).align_offset(1) == 0);
assert!(ptr.wrapping_byte_add(2).align_offset(2) == 0);
assert!(ptr.wrapping_byte_add(2).align_offset(4) == usize::MAX);
assert!(ptr.wrapping_byte_add(3).align_offset(1) == 0);
assert!(ptr.wrapping_byte_add(3).align_offset(2) == usize::MAX);
assert!(ptr.wrapping_add(42).align_offset(4) == 0);
assert!(ptr.wrapping_add(42).align_offset(8) == usize::MAX);
let ptr1: *const i8 = ptr.cast();
assert!(ptr1.align_offset(1) == 0);
assert!(ptr1.align_offset(2) == 0);
assert!(ptr1.align_offset(4) == 0);
assert!(ptr1.align_offset(8) == usize::MAX);
assert!(ptr1.wrapping_byte_add(1).align_offset(1) == 0);
assert!(ptr1.wrapping_byte_add(1).align_offset(2) == 1);
assert!(ptr1.wrapping_byte_add(1).align_offset(4) == 3);
assert!(ptr1.wrapping_byte_add(1).align_offset(8) == usize::MAX);
assert!(ptr1.wrapping_byte_add(2).align_offset(1) == 0);
assert!(ptr1.wrapping_byte_add(2).align_offset(2) == 0);
assert!(ptr1.wrapping_byte_add(2).align_offset(4) == 2);
assert!(ptr1.wrapping_byte_add(2).align_offset(8) == usize::MAX);
assert!(ptr1.wrapping_byte_add(3).align_offset(1) == 0);
assert!(ptr1.wrapping_byte_add(3).align_offset(2) == 1);
assert!(ptr1.wrapping_byte_add(3).align_offset(4) == 1);
assert!(ptr1.wrapping_byte_add(3).align_offset(8) == usize::MAX);
let ptr2: *const i16 = ptr.cast();
assert!(ptr2.align_offset(1) == 0);
assert!(ptr2.align_offset(2) == 0);
assert!(ptr2.align_offset(4) == 0);
assert!(ptr2.align_offset(8) == usize::MAX);
assert!(ptr2.wrapping_byte_add(1).align_offset(1) == 0);
assert!(ptr2.wrapping_byte_add(1).align_offset(2) == usize::MAX);
assert!(ptr2.wrapping_byte_add(2).align_offset(1) == 0);
assert!(ptr2.wrapping_byte_add(2).align_offset(2) == 0);
assert!(ptr2.wrapping_byte_add(2).align_offset(4) == 1);
assert!(ptr2.wrapping_byte_add(2).align_offset(8) == usize::MAX);
assert!(ptr2.wrapping_byte_add(3).align_offset(1) == 0);
assert!(ptr2.wrapping_byte_add(3).align_offset(2) == usize::MAX);
let ptr3: *const i64 = ptr.cast();
assert!(ptr3.align_offset(1) == 0);
assert!(ptr3.align_offset(2) == 0);
assert!(ptr3.align_offset(4) == 0);
assert!(ptr3.align_offset(8) == usize::MAX);
assert!(ptr3.wrapping_byte_add(1).align_offset(1) == 0);
assert!(ptr3.wrapping_byte_add(1).align_offset(2) == usize::MAX);
// `stride % align != 0` (edge case)
let ptr4: *const [u8; 3] = ptr.cast();
assert!(ptr4.align_offset(1) == 0);
assert!(ptr4.align_offset(2) == 0);
assert!(ptr4.align_offset(4) == 0);
assert!(ptr4.align_offset(8) == usize::MAX);
assert!(ptr4.wrapping_byte_add(1).align_offset(1) == 0);
assert!(ptr4.wrapping_byte_add(1).align_offset(2) == 1);
assert!(ptr4.wrapping_byte_add(1).align_offset(4) == 1);
assert!(ptr4.wrapping_byte_add(1).align_offset(8) == usize::MAX);
assert!(ptr4.wrapping_byte_add(2).align_offset(1) == 0);
assert!(ptr4.wrapping_byte_add(2).align_offset(2) == 0);
assert!(ptr4.wrapping_byte_add(2).align_offset(4) == 2);
assert!(ptr4.wrapping_byte_add(2).align_offset(8) == usize::MAX);
assert!(ptr4.wrapping_byte_add(3).align_offset(1) == 0);
assert!(ptr4.wrapping_byte_add(3).align_offset(2) == 1);
assert!(ptr4.wrapping_byte_add(3).align_offset(4) == 3);
assert!(ptr4.wrapping_byte_add(3).align_offset(8) == usize::MAX);
let ptr5: *const [u8; 5] = ptr.cast();
assert!(ptr5.align_offset(1) == 0);
assert!(ptr5.align_offset(2) == 0);
assert!(ptr5.align_offset(4) == 0);
assert!(ptr5.align_offset(8) == usize::MAX);
assert!(ptr5.wrapping_byte_add(1).align_offset(1) == 0);
assert!(ptr5.wrapping_byte_add(1).align_offset(2) == 1);
assert!(ptr5.wrapping_byte_add(1).align_offset(4) == 3);
assert!(ptr5.wrapping_byte_add(1).align_offset(8) == usize::MAX);
assert!(ptr5.wrapping_byte_add(2).align_offset(1) == 0);
assert!(ptr5.wrapping_byte_add(2).align_offset(2) == 0);
assert!(ptr5.wrapping_byte_add(2).align_offset(4) == 2);
assert!(ptr5.wrapping_byte_add(2).align_offset(8) == usize::MAX);
assert!(ptr5.wrapping_byte_add(3).align_offset(1) == 0);
assert!(ptr5.wrapping_byte_add(3).align_offset(2) == 1);
assert!(ptr5.wrapping_byte_add(3).align_offset(4) == 1);
assert!(ptr5.wrapping_byte_add(3).align_offset(8) == usize::MAX);
}
}
#[test]
fn align_offset_issue_103361() {
#[cfg(target_pointer_width = "64")]
@ -467,6 +680,72 @@ fn align_offset_issue_103361() {
let _ = (SIZE as *const HugeSize).align_offset(SIZE);
}
#[test]
#[cfg(not(bootstrap))]
fn align_offset_issue_103361_const() {
#[cfg(target_pointer_width = "64")]
const SIZE: usize = 1 << 47;
#[cfg(target_pointer_width = "32")]
const SIZE: usize = 1 << 30;
#[cfg(target_pointer_width = "16")]
const SIZE: usize = 1 << 13;
struct HugeSize([u8; SIZE - 1]);
const {
assert!(ptr::invalid::<HugeSize>(SIZE - 1).align_offset(SIZE) == SIZE - 1);
assert!(ptr::invalid::<HugeSize>(SIZE).align_offset(SIZE) == 0);
assert!(ptr::invalid::<HugeSize>(SIZE + 1).align_offset(SIZE) == 1);
}
}
#[test]
fn is_aligned() {
let data = 42;
let ptr: *const i32 = &data;
assert!(ptr.is_aligned());
assert!(ptr.is_aligned_to(1));
assert!(ptr.is_aligned_to(2));
assert!(ptr.is_aligned_to(4));
assert!(ptr.wrapping_byte_add(2).is_aligned_to(1));
assert!(ptr.wrapping_byte_add(2).is_aligned_to(2));
assert!(!ptr.wrapping_byte_add(2).is_aligned_to(4));
// At runtime either `ptr` or `ptr+1` is aligned to 8.
assert_ne!(ptr.is_aligned_to(8), ptr.wrapping_add(1).is_aligned_to(8));
}
#[test]
#[cfg(not(bootstrap))]
fn is_aligned_const() {
const {
let data = 42;
let ptr: *const i32 = &data;
assert!(ptr.is_aligned());
assert!(ptr.is_aligned_to(1));
assert!(ptr.is_aligned_to(2));
assert!(ptr.is_aligned_to(4));
assert!(ptr.wrapping_byte_add(2).is_aligned_to(1));
assert!(ptr.wrapping_byte_add(2).is_aligned_to(2));
assert!(!ptr.wrapping_byte_add(2).is_aligned_to(4));
// At comptime neither `ptr` nor `ptr+1` is aligned to 8.
assert!(!ptr.is_aligned_to(8));
assert!(!ptr.wrapping_add(1).is_aligned_to(8));
}
}
#[test]
#[cfg(bootstrap)]
fn is_aligned_const() {
const {
let data = 42;
let ptr: *const i32 = &data;
// The bootstrap compiler always returns false for is_aligned.
assert!(!ptr.is_aligned());
assert!(!ptr.is_aligned_to(1));
}
}
#[test]
fn offset_from() {
let mut a = [0; 5];

58
src/test/assembly/is_aligned.rs Normal file
View file

@ -0,0 +1,58 @@
// assembly-output: emit-asm
// min-llvm-version: 14.0
// only-x86_64
// revisions: opt-speed opt-size
// [opt-speed] compile-flags: -Copt-level=1
// [opt-size] compile-flags: -Copt-level=s
#![crate_type="rlib"]
#![feature(core_intrinsics)]
#![feature(pointer_is_aligned)]
// CHECK-LABEL: is_aligned_to_unchecked
// CHECK: decq
// CHECK-NEXT: testq
// CHECK-NEXT: sete
// CHECK: retq
#[no_mangle]
pub unsafe fn is_aligned_to_unchecked(ptr: *const u8, align: usize) -> bool {
unsafe {
std::intrinsics::assume(align.is_power_of_two())
}
ptr.is_aligned_to(align)
}
// CHECK-LABEL: is_aligned_1
// CHECK: movb $1
// CHECK: retq
#[no_mangle]
pub fn is_aligned_1(ptr: *const u8) -> bool {
ptr.is_aligned()
}
// CHECK-LABEL: is_aligned_2
// CHECK: testb $1
// CHECK-NEXT: sete
// CHECK: retq
#[no_mangle]
pub fn is_aligned_2(ptr: *const u16) -> bool {
ptr.is_aligned()
}
// CHECK-LABEL: is_aligned_4
// CHECK: testb $3
// CHECK-NEXT: sete
// CHECK: retq
#[no_mangle]
pub fn is_aligned_4(ptr: *const u32) -> bool {
ptr.is_aligned()
}
// CHECK-LABEL: is_aligned_8
// CHECK: testb $7
// CHECK-NEXT: sete
// CHECK: retq
#[no_mangle]
pub fn is_aligned_8(ptr: *const u64) -> bool {
ptr.is_aligned()
}

5
src/tools/miri/src/shims/intrinsics/mod.rs
View file

@ -368,11 +368,6 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
}
// Other
"exact_div" => {
let [num, denom] = check_arg_count(args)?;
this.exact_div(&this.read_immediate(num)?, &this.read_immediate(denom)?, dest)?;
}
"breakpoint" => {
let [] = check_arg_count(args)?;
// normally this would raise a SIGTRAP, which aborts if no debugger is connected