Merge pull request #408 from RalfJung/without_provenance

add without_provenance to pointer types

Author: calebzulawski

crates/core_simd/src/simd/ptr/const_ptr.rs

@@ -42,6 +42,19 @@ pub trait SimdConstPtr: Copy + Sealed {
     /// Equivalent to calling [`pointer::addr`] on each element.
     fn addr(self) -> Self::Usize;
 
+    /// Convert an address to a pointer without giving it any provenance.
+    ///
+    /// Without provenance, this pointer is not associated with any actual allocation. Such a
+    /// no-provenance pointer may be used for zero-sized memory accesses (if suitably aligned), but
+    /// non-zero-sized memory accesses with a no-provenance pointer are UB. No-provenance pointers
+    /// are little more than a usize address in disguise.
+    ///
+    /// This is different from [`Self::from_exposed_addr`], which creates a pointer that picks up a
+    /// previously exposed provenance.
+    ///
+    /// Equivalent to calling [`core::ptr::without_provenance`] on each element.
+    fn without_provenance(addr: Self::Usize) -> Self;
+
     /// Creates a new pointer with the given address.
     ///
     /// This performs the same operation as a cast, but copies the *address-space* and
@@ -118,6 +131,14 @@ where
         unsafe { core::mem::transmute_copy(&self) }
     }
 
+    #[inline]
+    fn without_provenance(addr: Self::Usize) -> Self {
+        // FIXME(strict_provenance_magic): I am magic and should be a compiler intrinsic.
+        // SAFETY: Integer-to-pointer transmutes are valid (if you are okay with not getting any
+        // provenance).
+        unsafe { core::mem::transmute_copy(&addr) }
+    }
+
     #[inline]
     fn with_addr(self, addr: Self::Usize) -> Self {
         // FIXME(strict_provenance_magic): I am magic and should be a compiler intrinsic.

crates/core_simd/src/simd/ptr/mut_ptr.rs

@@ -39,6 +39,19 @@ pub trait SimdMutPtr: Copy + Sealed {
     /// Equivalent to calling [`pointer::addr`] on each element.
     fn addr(self) -> Self::Usize;
 
+    /// Convert an address to a pointer without giving it any provenance.
+    ///
+    /// Without provenance, this pointer is not associated with any actual allocation. Such a
+    /// no-provenance pointer may be used for zero-sized memory accesses (if suitably aligned), but
+    /// non-zero-sized memory accesses with a no-provenance pointer are UB. No-provenance pointers
+    /// are little more than a usize address in disguise.
+    ///
+    /// This is different from [`Self::from_exposed_addr`], which creates a pointer that picks up a
+    /// previously exposed provenance.
+    ///
+    /// Equivalent to calling [`core::ptr::without_provenance`] on each element.
+    fn without_provenance(addr: Self::Usize) -> Self;
+
     /// Creates a new pointer with the given address.
     ///
     /// This performs the same operation as a cast, but copies the *address-space* and
@@ -115,6 +128,14 @@ where
         unsafe { core::mem::transmute_copy(&self) }
     }
 
+    #[inline]
+    fn without_provenance(addr: Self::Usize) -> Self {
+        // FIXME(strict_provenance_magic): I am magic and should be a compiler intrinsic.
+        // SAFETY: Integer-to-pointer transmutes are valid (if you are okay with not getting any
+        // provenance).
+        unsafe { core::mem::transmute_copy(&addr) }
+    }
+
     #[inline]
     fn with_addr(self, addr: Self::Usize) -> Self {
         // FIXME(strict_provenance_magic): I am magic and should be a compiler intrinsic.