Rollup merge of rust-lang#100169 - WaffleLapkin:optimize_is_aligned_to, r=workingjubilee

Optimize `pointer::as_aligned_to`

This PR replaces `addr % align` with `addr & align - 1`, which is correct due to `align` being a power of two.

Here is a proof that this makes things better: [[godbolt]](https://godbolt.org/z/Wbq3hx6YG).

This PR also removes `assume(align != 0)`, with the new impl it does not improve anything anymore ([[godbolt]](https://rust.godbolt.org/z/zcnrG4777), [[original concern]](rust-lang#95643 (comment))).

Author: matthiaskrgr

library/core/src/ptr/const_ptr.rs

@@ -1336,11 +1336,8 @@ impl<T: ?Sized> *const T {
             panic!("is_aligned_to: align is not a power-of-two");
         }
 
-        // SAFETY: `is_power_of_two()` will return `false` for zero.
-        unsafe { core::intrinsics::assume(align != 0) };
-
         // Cast is needed for `T: !Sized`
-        self.cast::<u8>().addr() % align == 0
+        self.cast::<u8>().addr() & align - 1 == 0
     }
 }
 

library/core/src/ptr/mut_ptr.rs

@@ -1614,11 +1614,8 @@ impl<T: ?Sized> *mut T {
             panic!("is_aligned_to: align is not a power-of-two");
         }
 
-        // SAFETY: `is_power_of_two()` will return `false` for zero.
-        unsafe { core::intrinsics::assume(align != 0) };
-
         // Cast is needed for `T: !Sized`
-        self.cast::<u8>().addr() % align == 0
+        self.cast::<u8>().addr() & align - 1 == 0
     }
 }