Rollup merge of #76965 - fusion-engineering-forks:fix-atomic-from-mut, r=Amanieu
Add cfg(target_has_atomic_equal_alignment) and use it for Atomic::from_mut. Fixes some platform-specific problems with #74532 by using the actual alignment of the types instead of hardcoding a few `target_arch`s. r? @RalfJung
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8 changed files with 272 additions and 5 deletions
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@ -327,6 +327,28 @@ impl AtomicBool {
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unsafe { &mut *(self.v.get() as *mut bool) }
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}
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/// Get atomic access to a `&mut bool`.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(atomic_from_mut)]
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/// use std::sync::atomic::{AtomicBool, Ordering};
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///
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/// let mut some_bool = true;
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/// let a = AtomicBool::from_mut(&mut some_bool);
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/// a.store(false, Ordering::Relaxed);
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/// assert_eq!(some_bool, false);
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/// ```
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#[inline]
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#[cfg(target_has_atomic_equal_alignment = "8")]
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#[unstable(feature = "atomic_from_mut", issue = "76314")]
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pub fn from_mut(v: &mut bool) -> &Self {
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// SAFETY: the mutable reference guarantees unique ownership, and
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// alignment of both `bool` and `Self` is 1.
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unsafe { &*(v as *mut bool as *mut Self) }
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}
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/// Consumes the atomic and returns the contained value.
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///
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/// This is safe because passing `self` by value guarantees that no other threads are
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@ -819,6 +841,32 @@ impl<T> AtomicPtr<T> {
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self.p.get_mut()
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}
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/// Get atomic access to a pointer.
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///
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/// # Examples
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///
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/// ```
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/// #![feature(atomic_from_mut)]
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/// use std::sync::atomic::{AtomicPtr, Ordering};
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///
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/// let mut some_ptr = &mut 123 as *mut i32;
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/// let a = AtomicPtr::from_mut(&mut some_ptr);
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/// a.store(&mut 456, Ordering::Relaxed);
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/// assert_eq!(unsafe { *some_ptr }, 456);
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/// ```
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#[inline]
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#[cfg(target_has_atomic_equal_alignment = "ptr")]
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#[unstable(feature = "atomic_from_mut", issue = "76314")]
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pub fn from_mut(v: &mut *mut T) -> &Self {
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use crate::mem::align_of;
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let [] = [(); align_of::<AtomicPtr<()>>() - align_of::<*mut ()>()];
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// SAFETY:
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// - the mutable reference guarantees unique ownership.
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// - the alignment of `*mut T` and `Self` is the same on all platforms
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// supported by rust, as verified above.
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unsafe { &*(v as *mut *mut T as *mut Self) }
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}
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/// Consumes the atomic and returns the contained value.
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///
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/// This is safe because passing `self` by value guarantees that no other threads are
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@ -1113,6 +1161,7 @@ macro_rules! if_not_8_bit {
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#[cfg(target_has_atomic_load_store = "8")]
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macro_rules! atomic_int {
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($cfg_cas:meta,
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$cfg_align:meta,
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$stable:meta,
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$stable_cxchg:meta,
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$stable_debug:meta,
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@ -1231,6 +1280,45 @@ assert_eq!(some_var.load(Ordering::SeqCst), 5);
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}
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}
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doc_comment! {
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concat!("Get atomic access to a `&mut ", stringify!($int_type), "`.
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",
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if_not_8_bit! {
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$int_type,
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concat!(
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"**Note:** This function is only available on targets where `",
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stringify!($int_type), "` has an alignment of ", $align, " bytes."
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)
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},
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"
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# Examples
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```
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#![feature(atomic_from_mut)]
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", $extra_feature, "use std::sync::atomic::{", stringify!($atomic_type), ", Ordering};
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let mut some_int = 123;
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let a = ", stringify!($atomic_type), "::from_mut(&mut some_int);
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a.store(100, Ordering::Relaxed);
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assert_eq!(some_int, 100);
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```
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"),
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#[inline]
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#[$cfg_align]
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#[unstable(feature = "atomic_from_mut", issue = "76314")]
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pub fn from_mut(v: &mut $int_type) -> &Self {
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use crate::mem::align_of;
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let [] = [(); align_of::<Self>() - align_of::<$int_type>()];
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// SAFETY:
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// - the mutable reference guarantees unique ownership.
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// - the alignment of `$int_type` and `Self` is the
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// same, as promised by $cfg_align and verified above.
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unsafe { &*(v as *mut $int_type as *mut Self) }
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}
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}
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doc_comment! {
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concat!("Consumes the atomic and returns the contained value.
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@ -1873,6 +1961,7 @@ let mut atomic = ", stringify!($atomic_type), "::new(1);
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#[cfg(target_has_atomic_load_store = "8")]
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atomic_int! {
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cfg(target_has_atomic = "8"),
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cfg(target_has_atomic_equal_alignment = "8"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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@ -1891,6 +1980,7 @@ atomic_int! {
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#[cfg(target_has_atomic_load_store = "8")]
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atomic_int! {
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cfg(target_has_atomic = "8"),
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cfg(target_has_atomic_equal_alignment = "8"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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@ -1909,6 +1999,7 @@ atomic_int! {
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#[cfg(target_has_atomic_load_store = "16")]
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atomic_int! {
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cfg(target_has_atomic = "16"),
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cfg(target_has_atomic_equal_alignment = "16"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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@ -1927,6 +2018,7 @@ atomic_int! {
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#[cfg(target_has_atomic_load_store = "16")]
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atomic_int! {
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cfg(target_has_atomic = "16"),
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cfg(target_has_atomic_equal_alignment = "16"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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@ -1945,6 +2037,7 @@ atomic_int! {
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#[cfg(target_has_atomic_load_store = "32")]
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atomic_int! {
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cfg(target_has_atomic = "32"),
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cfg(target_has_atomic_equal_alignment = "32"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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@ -1963,6 +2056,7 @@ atomic_int! {
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#[cfg(target_has_atomic_load_store = "32")]
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atomic_int! {
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cfg(target_has_atomic = "32"),
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cfg(target_has_atomic_equal_alignment = "32"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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@ -1981,6 +2075,7 @@ atomic_int! {
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#[cfg(target_has_atomic_load_store = "64")]
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atomic_int! {
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cfg(target_has_atomic = "64"),
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cfg(target_has_atomic_equal_alignment = "64"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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@ -1999,6 +2094,7 @@ atomic_int! {
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#[cfg(target_has_atomic_load_store = "64")]
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atomic_int! {
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cfg(target_has_atomic = "64"),
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cfg(target_has_atomic_equal_alignment = "64"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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stable(feature = "integer_atomics_stable", since = "1.34.0"),
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@ -2017,6 +2113,7 @@ atomic_int! {
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#[cfg(target_has_atomic_load_store = "128")]
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atomic_int! {
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cfg(target_has_atomic = "128"),
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cfg(target_has_atomic_equal_alignment = "128"),
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unstable(feature = "integer_atomics", issue = "32976"),
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unstable(feature = "integer_atomics", issue = "32976"),
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unstable(feature = "integer_atomics", issue = "32976"),
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@ -2035,6 +2132,7 @@ atomic_int! {
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#[cfg(target_has_atomic_load_store = "128")]
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atomic_int! {
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cfg(target_has_atomic = "128"),
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cfg(target_has_atomic_equal_alignment = "128"),
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unstable(feature = "integer_atomics", issue = "32976"),
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unstable(feature = "integer_atomics", issue = "32976"),
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unstable(feature = "integer_atomics", issue = "32976"),
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@ -2074,6 +2172,7 @@ macro_rules! ptr_width {
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#[cfg(target_has_atomic_load_store = "ptr")]
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atomic_int! {
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cfg(target_has_atomic = "ptr"),
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cfg(target_has_atomic_equal_alignment = "ptr"),
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stable(feature = "rust1", since = "1.0.0"),
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stable(feature = "extended_compare_and_swap", since = "1.10.0"),
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stable(feature = "atomic_debug", since = "1.3.0"),
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@ -2092,6 +2191,7 @@ atomic_int! {
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#[cfg(target_has_atomic_load_store = "ptr")]
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atomic_int! {
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cfg(target_has_atomic = "ptr"),
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cfg(target_has_atomic_equal_alignment = "ptr"),
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stable(feature = "rust1", since = "1.0.0"),
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stable(feature = "extended_compare_and_swap", since = "1.10.0"),
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stable(feature = "atomic_debug", since = "1.3.0"),
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