diff --git a/src/liballoc/lib.rs b/src/liballoc/lib.rs
index ca86850f5df..2db9cc7c4d8 100644
--- a/src/liballoc/lib.rs
+++ b/src/liballoc/lib.rs
@@ -83,6 +83,7 @@
 #![feature(lang_items)]
 #![feature(no_std)]
 #![feature(nonzero)]
+#![feature(num_bits_bytes)]
 #![feature(optin_builtin_traits)]
 #![feature(placement_in_syntax)]
 #![feature(placement_new_protocol)]
diff --git a/src/liballoc/raw_vec.rs b/src/liballoc/raw_vec.rs
index 9311f44d9df..97acd0db524 100644
--- a/src/liballoc/raw_vec.rs
+++ b/src/liballoc/raw_vec.rs
@@ -15,6 +15,7 @@ use heap;
 use super::oom;
 use super::boxed::Box;
 use core::ops::Drop;
+use core;
 
 /// A low-level utility for more ergonomically allocating, reallocating, and deallocating a
 /// a buffer of memory on the heap without having to worry about all the corner cases
@@ -443,11 +444,8 @@ impl<T> Drop for RawVec<T> {
 // user-space. e.g. PAE or x32
 
 #[inline]
-#[cfg(target_pointer_width = "64")]
-fn alloc_guard(_alloc_size: usize) { }
-
-#[inline]
-#[cfg(target_pointer_width = "32")]
 fn alloc_guard(alloc_size: usize) {
-    assert!(alloc_size <= ::core::isize::MAX as usize, "capacity overflow");
+    if core::usize::BITS < 64 {
+        assert!(alloc_size <= ::core::isize::MAX as usize, "capacity overflow");
+    }
 }
diff --git a/src/libcore/fmt/mod.rs b/src/libcore/fmt/mod.rs
index ea2a9d1cfaf..86700583f2d 100644
--- a/src/libcore/fmt/mod.rs
+++ b/src/libcore/fmt/mod.rs
@@ -1340,12 +1340,7 @@ impl<T> Pointer for *const T {
             f.flags |= 1 << (FlagV1::SignAwareZeroPad as u32);
 
             if let None = f.width {
-                // The formats need two extra bytes, for the 0x
-                if cfg!(target_pointer_width = "32") {
-                    f.width = Some(10);
-                } else {
-                    f.width = Some(18);
-                }
+                f.width = Some((::usize::BITS/4) + 2);
             }
         }
         f.flags |= 1 << (FlagV1::Alternate as u32);
diff --git a/src/libcore/hash/mod.rs b/src/libcore/hash/mod.rs
index 361c6d700de..2a4c909d638 100644
--- a/src/libcore/hash/mod.rs
+++ b/src/libcore/hash/mod.rs
@@ -144,11 +144,11 @@ pub trait Hasher {
     #[inline]
     #[stable(feature = "hasher_write", since = "1.3.0")]
     fn write_usize(&mut self, i: usize) {
-        if cfg!(target_pointer_width = "32") {
-            self.write_u32(i as u32)
-        } else {
-            self.write_u64(i as u64)
-        }
+        let bytes = unsafe {
+            ::slice::from_raw_parts(&i as *const usize as *const u8,
+                                    mem::size_of::<usize>())
+        };
+        self.write(bytes);
     }
 
     /// Write a single `i8` into this hasher.
diff --git a/src/libcore/iter.rs b/src/libcore/iter.rs
index 0471a08cd78..b800ec24a95 100644
--- a/src/libcore/iter.rs
+++ b/src/libcore/iter.rs
@@ -2234,7 +2234,9 @@ step_impl_signed!(isize i8 i16 i32);
 step_impl_unsigned!(u64);
 #[cfg(target_pointer_width = "64")]
 step_impl_signed!(i64);
-#[cfg(target_pointer_width = "32")]
+// If the target pointer width is not 64-bits, we
+// assume here that it is less than 64-bits.
+#[cfg(not(target_pointer_width = "64"))]
 step_impl_no_between!(u64 i64);
 
 /// An adapter for stepping range iterators by a custom amount.