Make use of `[wrapping_]byte_{add,sub}`

...replacing `.cast().wrapping_offset().cast()` & similar code.

2 files changed, 7 insertions, 10 deletions

diff --git a/library/alloc/src/vec/into_iter.rs b/library/alloc/src/vec/into_iter.rs
index 4351548811d..ed049194dd0 100644
--- a/library/alloc/src/vec/into_iter.rs
+++ b/library/alloc/src/vec/into_iter.rs
@@ -4,7 +4,6 @@ use crate::alloc::{Allocator, Global};
 use crate::raw_vec::RawVec;
 use core::array;
 use core::fmt;
-use core::intrinsics::arith_offset;
 use core::iter::{
     FusedIterator, InPlaceIterable, SourceIter, TrustedLen, TrustedRandomAccessNoCoerce,
 };
@@ -154,7 +153,7 @@ impl<T, A: Allocator> Iterator for IntoIter<T, A> {
             // purposefully don't use 'ptr.offset' because for
             // vectors with 0-size elements this would return the
             // same pointer.
-            self.ptr = unsafe { arith_offset(self.ptr as *const i8, 1) as *mut T };
+            self.ptr = self.ptr.wrapping_byte_add(1);
 
             // Make up a value of this ZST.
             Some(unsafe { mem::zeroed() })
@@ -184,7 +183,7 @@ impl<T, A: Allocator> Iterator for IntoIter<T, A> {
             // SAFETY: due to unchecked casts of unsigned amounts to signed offsets the wraparound
             // effectively results in unsigned pointers representing positions 0..usize::MAX,
             // which is valid for ZSTs.
-            self.ptr = unsafe { arith_offset(self.ptr as *const i8, step_size as isize) as *mut T }
+            self.ptr = self.ptr.wrapping_byte_add(step_size);
         } else {
             // SAFETY: the min() above ensures that step_size is in bounds
             self.ptr = unsafe { self.ptr.add(step_size) };
@@ -217,7 +216,7 @@ impl<T, A: Allocator> Iterator for IntoIter<T, A> {
                 return Err(unsafe { array::IntoIter::new_unchecked(raw_ary, 0..len) });
             }
 
-            self.ptr = unsafe { arith_offset(self.ptr as *const i8, N as isize) as *mut T };
+            self.ptr = self.ptr.wrapping_byte_add(N);
             // Safety: ditto
             return Ok(unsafe { MaybeUninit::array_assume_init(raw_ary) });
         }
@@ -267,7 +266,7 @@ impl<T, A: Allocator> DoubleEndedIterator for IntoIter<T, A> {
             None
         } else if mem::size_of::<T>() == 0 {
             // See above for why 'ptr.offset' isn't used
-            self.end = unsafe { arith_offset(self.end as *const i8, -1) as *mut T };
+            self.end = self.ptr.wrapping_byte_sub(1);
 
             // Make up a value of this ZST.
             Some(unsafe { mem::zeroed() })
@@ -283,9 +282,7 @@ impl<T, A: Allocator> DoubleEndedIterator for IntoIter<T, A> {
         let step_size = self.len().min(n);
         if mem::size_of::<T>() == 0 {
             // SAFETY: same as for advance_by()
-            self.end = unsafe {
-                arith_offset(self.end as *const i8, step_size.wrapping_neg() as isize) as *mut T
-            }
+            self.end = self.end.wrapping_byte_sub(step_size);
         } else {
             // SAFETY: same as for advance_by()
             self.end = unsafe { self.end.sub(step_size) };
diff --git a/library/alloc/src/vec/mod.rs b/library/alloc/src/vec/mod.rs
index 2c786fd511e..1f19b9e5945 100644
--- a/library/alloc/src/vec/mod.rs
+++ b/library/alloc/src/vec/mod.rs
@@ -59,7 +59,7 @@ use core::cmp::Ordering;
 use core::convert::TryFrom;
 use core::fmt;
 use core::hash::{Hash, Hasher};
-use core::intrinsics::{arith_offset, assume};
+use core::intrinsics::assume;
 use core::iter;
 #[cfg(not(no_global_oom_handling))]
 use core::iter::FromIterator;
@@ -2678,7 +2678,7 @@ impl<T, A: Allocator> IntoIterator for Vec<T, A> {
             let alloc = ManuallyDrop::new(ptr::read(me.allocator()));
             let begin = me.as_mut_ptr();
             let end = if mem::size_of::<T>() == 0 {
-                arith_offset(begin as *const i8, me.len() as isize) as *const T
+                begin.wrapping_byte_add(me.len())
             } else {
                 begin.add(me.len()) as *const T
             };