Also use in memchr

Author: oli-obk

src/libcore/ptr.rs

@@ -646,7 +646,7 @@ impl<T: ?Sized> *const T {
     /// Accessing adjacent `u8` as `u16`
     ///
     /// ```
-    /// # #![feature(core_intrinsics)]
+    /// # #![feature(align_offset)]
     /// # fn foo(n: usize) {
     /// # use std::mem::align_of;
     /// # unsafe {
@@ -875,7 +875,7 @@ impl<T: ?Sized> *mut T {
     /// Accessing adjacent `u8` as `u16`
     ///
     /// ```
-    /// # #![feature(core_intrinsics)]
+    /// # #![feature(align_offset)]
     /// # fn foo(n: usize) {
     /// # use std::mem::align_of;
     /// # unsafe {

src/libstd/sys_common/memchr.rs

@@ -15,6 +15,7 @@
 pub mod fallback {
     use cmp;
     use mem;
+    use intrinsics::align_offset;
 
     const LO_U64: u64 = 0x0101010101010101;
     const HI_U64: u64 = 0x8080808080808080;
@@ -65,15 +66,12 @@ pub mod fallback {
         let usize_bytes = mem::size_of::<usize>();
 
         // search up to an aligned boundary
-        let align = (ptr as usize) & (usize_bytes- 1);
-        let mut offset;
-        if align > 0 {
-            offset = cmp::min(usize_bytes - align, len);
+        let mut offset = unsafe { align_offset(ptr as *const _, usize_bytes) };
+        if offset > 0 {
+            offset = cmp::min(offset, len);
             if let Some(index) = text[..offset].iter().position(|elt| *elt == x) {
                 return Some(index);
             }
-        } else {
-            offset = 0;
         }
 
         // search the body of the text