Rollup of 6 pull requests

config.example.toml

@@ -922,6 +922,15 @@
 # argument as the test binary.
 #runner = <none> (string)
 
+# Use the optimized LLVM C intrinsics for `compiler_builtins`, rather than Rust intrinsics
+# on this target.
+# Requires the LLVM submodule to be managed by bootstrap (i.e. not external) so that `compiler-rt`
+# sources are available.
+#
+# Setting this to `false` generates slower code, but removes the requirement for a C toolchain in
+# order to run `x check`.
+#optimized-compiler-builtins = build.optimized-compiler-builtins (bool)
+
 # =============================================================================
 # Distribution options
 #

library/alloc/src/lib.rs

@@ -126,6 +126,7 @@
 #![feature(local_waker)]
 #![feature(maybe_uninit_slice)]
 #![feature(maybe_uninit_uninit_array_transpose)]
+#![feature(nonnull_provenance)]
 #![feature(panic_internals)]
 #![feature(pattern)]
 #![feature(pin_coerce_unsized_trait)]
@@ -142,6 +143,7 @@
 #![feature(slice_range)]
 #![feature(std_internals)]
 #![feature(str_internals)]
+#![feature(temporary_niche_types)]
 #![feature(trusted_fused)]
 #![feature(trusted_len)]
 #![feature(trusted_random_access)]

library/alloc/src/raw_vec.rs

@@ -33,21 +33,15 @@ enum AllocInit {
     Zeroed,
 }
 
-#[repr(transparent)]
-#[cfg_attr(target_pointer_width = "16", rustc_layout_scalar_valid_range_end(0x7fff))]
-#[cfg_attr(target_pointer_width = "32", rustc_layout_scalar_valid_range_end(0x7fff_ffff))]
-#[cfg_attr(target_pointer_width = "64", rustc_layout_scalar_valid_range_end(0x7fff_ffff_ffff_ffff))]
-struct Cap(usize);
+type Cap = core::num::niche_types::UsizeNoHighBit;
 
-impl Cap {
-    const ZERO: Cap = unsafe { Cap(0) };
+const ZERO_CAP: Cap = unsafe { Cap::new_unchecked(0) };
 
-    /// `Cap(cap)`, except if `T` is a ZST then `Cap::ZERO`.
-    ///
-    /// # Safety: cap must be <= `isize::MAX`.
-    unsafe fn new<T>(cap: usize) -> Self {
-        if T::IS_ZST { Cap::ZERO } else { unsafe { Self(cap) } }
-    }
+/// `Cap(cap)`, except if `T` is a ZST then `Cap::ZERO`.
+///
+/// # Safety: cap must be <= `isize::MAX`.
+unsafe fn new_cap<T>(cap: usize) -> Cap {
+    if T::IS_ZST { ZERO_CAP } else { unsafe { Cap::new_unchecked(cap) } }
 }
 
 /// A low-level utility for more ergonomically allocating, reallocating, and deallocating
@@ -257,7 +251,7 @@ impl<T, A: Allocator> RawVec<T, A> {
         // SAFETY: Precondition passed to the caller
         unsafe {
             let ptr = ptr.cast();
-            let capacity = Cap::new::<T>(capacity);
+            let capacity = new_cap::<T>(capacity);
             Self {
                 inner: RawVecInner::from_raw_parts_in(ptr, capacity, alloc),
                 _marker: PhantomData,
@@ -275,7 +269,7 @@ impl<T, A: Allocator> RawVec<T, A> {
         // SAFETY: Precondition passed to the caller
         unsafe {
             let ptr = ptr.cast();
-            let capacity = Cap::new::<T>(capacity);
+            let capacity = new_cap::<T>(capacity);
             Self { inner: RawVecInner::from_nonnull_in(ptr, capacity, alloc), _marker: PhantomData }
         }
     }
@@ -410,7 +404,7 @@ impl<A: Allocator> RawVecInner<A> {
     const fn new_in(alloc: A, align: usize) -> Self {
         let ptr = unsafe { core::mem::transmute(align) };
         // `cap: 0` means "unallocated". zero-sized types are ignored.
-        Self { ptr, cap: Cap::ZERO, alloc }
+        Self { ptr, cap: ZERO_CAP, alloc }
     }
 
     #[cfg(not(no_global_oom_handling))]
@@ -483,7 +477,11 @@ impl<A: Allocator> RawVecInner<A> {
         // Allocators currently return a `NonNull<[u8]>` whose length
         // matches the size requested. If that ever changes, the capacity
         // here should change to `ptr.len() / mem::size_of::<T>()`.
-        Ok(Self { ptr: Unique::from(ptr.cast()), cap: unsafe { Cap(capacity) }, alloc })
+        Ok(Self {
+            ptr: Unique::from(ptr.cast()),
+            cap: unsafe { Cap::new_unchecked(capacity) },
+            alloc,
+        })
     }
 
     #[inline]
@@ -508,7 +506,7 @@ impl<A: Allocator> RawVecInner<A> {
 
     #[inline]
     const fn capacity(&self, elem_size: usize) -> usize {
-        if elem_size == 0 { usize::MAX } else { self.cap.0 }
+        if elem_size == 0 { usize::MAX } else { self.cap.as_inner() }
     }
 
     #[inline]
@@ -518,15 +516,15 @@ impl<A: Allocator> RawVecInner<A> {
 
     #[inline]
     fn current_memory(&self, elem_layout: Layout) -> Option<(NonNull<u8>, Layout)> {
-        if elem_layout.size() == 0 || self.cap.0 == 0 {
+        if elem_layout.size() == 0 || self.cap.as_inner() == 0 {
             None
         } else {
             // We could use Layout::array here which ensures the absence of isize and usize overflows
             // and could hypothetically handle differences between stride and size, but this memory
             // has already been allocated so we know it can't overflow and currently Rust does not
             // support such types. So we can do better by skipping some checks and avoid an unwrap.
             unsafe {
-                let alloc_size = elem_layout.size().unchecked_mul(self.cap.0);
+                let alloc_size = elem_layout.size().unchecked_mul(self.cap.as_inner());
                 let layout = Layout::from_size_align_unchecked(alloc_size, elem_layout.align());
                 Some((self.ptr.into(), layout))
             }
@@ -562,7 +560,7 @@ impl<A: Allocator> RawVecInner<A> {
     #[inline]
     #[track_caller]
     fn grow_one(&mut self, elem_layout: Layout) {
-        if let Err(err) = self.grow_amortized(self.cap.0, 1, elem_layout) {
+        if let Err(err) = self.grow_amortized(self.cap.as_inner(), 1, elem_layout) {
             handle_error(err);
         }
     }
@@ -627,7 +625,7 @@ impl<A: Allocator> RawVecInner<A> {
         // the size requested. If that ever changes, the capacity here should
         // change to `ptr.len() / mem::size_of::<T>()`.
         self.ptr = Unique::from(ptr.cast());
-        self.cap = unsafe { Cap(cap) };
+        self.cap = unsafe { Cap::new_unchecked(cap) };
     }
 
     fn grow_amortized(
@@ -650,7 +648,7 @@ impl<A: Allocator> RawVecInner<A> {
 
         // This guarantees exponential growth. The doubling cannot overflow
         // because `cap <= isize::MAX` and the type of `cap` is `usize`.
-        let cap = cmp::max(self.cap.0 * 2, required_cap);
+        let cap = cmp::max(self.cap.as_inner() * 2, required_cap);
         let cap = cmp::max(min_non_zero_cap(elem_layout.size()), cap);
 
         let new_layout = layout_array(cap, elem_layout)?;
@@ -719,7 +717,7 @@ impl<A: Allocator> RawVecInner<A> {
             unsafe { self.alloc.deallocate(ptr, layout) };
             self.ptr =
                 unsafe { Unique::new_unchecked(ptr::without_provenance_mut(elem_layout.align())) };
-            self.cap = Cap::ZERO;
+            self.cap = ZERO_CAP;
         } else {
             let ptr = unsafe {
                 // Layout cannot overflow here because it would have

library/alloc/src/rc.rs

@@ -252,6 +252,7 @@ use core::intrinsics::abort;
 use core::iter;
 use core::marker::{PhantomData, Unsize};
 use core::mem::{self, ManuallyDrop, align_of_val_raw};
+use core::num::NonZeroUsize;
 use core::ops::{CoerceUnsized, Deref, DerefMut, DerefPure, DispatchFromDyn, LegacyReceiver};
 use core::panic::{RefUnwindSafe, UnwindSafe};
 #[cfg(not(no_global_oom_handling))]
@@ -3027,12 +3028,7 @@ impl<T> Weak<T> {
     #[rustc_const_stable(feature = "const_weak_new", since = "1.73.0")]
     #[must_use]
     pub const fn new() -> Weak<T> {
-        Weak {
-            ptr: unsafe {
-                NonNull::new_unchecked(ptr::without_provenance_mut::<RcInner<T>>(usize::MAX))
-            },
-            alloc: Global,
-        }
+        Weak { ptr: NonNull::without_provenance(NonZeroUsize::MAX), alloc: Global }
     }
 }
 
@@ -3054,12 +3050,7 @@ impl<T, A: Allocator> Weak<T, A> {
     #[inline]
     #[unstable(feature = "allocator_api", issue = "32838")]
     pub fn new_in(alloc: A) -> Weak<T, A> {
-        Weak {
-            ptr: unsafe {
-                NonNull::new_unchecked(ptr::without_provenance_mut::<RcInner<T>>(usize::MAX))
-            },
-            alloc,
-        }
+        Weak { ptr: NonNull::without_provenance(NonZeroUsize::MAX), alloc }
     }
 }
 

library/alloc/src/sync.rs

@@ -18,6 +18,7 @@ use core::intrinsics::abort;
 use core::iter;
 use core::marker::{PhantomData, Unsize};
 use core::mem::{self, ManuallyDrop, align_of_val_raw};
+use core::num::NonZeroUsize;
 use core::ops::{CoerceUnsized, Deref, DerefPure, DispatchFromDyn, LegacyReceiver};
 use core::panic::{RefUnwindSafe, UnwindSafe};
 use core::pin::{Pin, PinCoerceUnsized};
@@ -2687,12 +2688,7 @@ impl<T> Weak<T> {
     #[rustc_const_stable(feature = "const_weak_new", since = "1.73.0")]
     #[must_use]
     pub const fn new() -> Weak<T> {
-        Weak {
-            ptr: unsafe {
-                NonNull::new_unchecked(ptr::without_provenance_mut::<ArcInner<T>>(usize::MAX))
-            },
-            alloc: Global,
-        }
+        Weak { ptr: NonNull::without_provenance(NonZeroUsize::MAX), alloc: Global }
     }
 }
 
@@ -2717,12 +2713,7 @@ impl<T, A: Allocator> Weak<T, A> {
     #[inline]
     #[unstable(feature = "allocator_api", issue = "32838")]
     pub fn new_in(alloc: A) -> Weak<T, A> {
-        Weak {
-            ptr: unsafe {
-                NonNull::new_unchecked(ptr::without_provenance_mut::<ArcInner<T>>(usize::MAX))
-            },
-            alloc,
-        }
+        Weak { ptr: NonNull::without_provenance(NonZeroUsize::MAX), alloc }
     }
 }
 

library/core/src/alloc/layout.rs

@@ -233,8 +233,7 @@ impl Layout {
     #[must_use]
     #[inline]
     pub const fn dangling(&self) -> NonNull<u8> {
-        // SAFETY: align is guaranteed to be non-zero
-        unsafe { NonNull::new_unchecked(crate::ptr::without_provenance_mut::<u8>(self.align())) }
+        NonNull::without_provenance(self.align.as_nonzero())
     }
 
     /// Creates a layout describing the record that can hold a value

library/core/src/num/mod.rs

@@ -51,6 +51,10 @@ mod overflow_panic;
 mod saturating;
 mod wrapping;
 
+/// 100% perma-unstable
+#[doc(hidden)]
+pub mod niche_types;
+
 #[stable(feature = "rust1", since = "1.0.0")]
 #[cfg(not(no_fp_fmt_parse))]
 pub use dec2flt::ParseFloatError;