implement raw pointer comparisons in librustc

This is mostly for consistency, as you can now compare raw pointers in
constant expressions or without the standard library.

It also reduces the number of `ptrtoint` instructions in the IR, making
tracking down culprits of what's usually an anti-pattern easier.

src/libstd/ptr.rs

@@ -383,7 +383,7 @@ impl<T> RawPtr<T> for *mut T {
 }
 
 // Equality for pointers
-#[cfg(not(test))]
+#[cfg(stage0, not(test))]
 impl<T> Eq for *T {
     #[inline]
     fn eq(&self, other: &*T) -> bool {
@@ -393,7 +393,17 @@ impl<T> Eq for *T {
     fn ne(&self, other: &*T) -> bool { !self.eq(other) }
 }
 
-#[cfg(not(test))]
+#[cfg(not(stage0), not(test))]
+impl<T> Eq for *T {
+    #[inline]
+    fn eq(&self, other: &*T) -> bool {
+        *self == *other
+    }
+    #[inline]
+    fn ne(&self, other: &*T) -> bool { !self.eq(other) }
+}
+
+#[cfg(stage0, not(test))]
 impl<T> Eq for *mut T {
     #[inline]
     fn eq(&self, other: &*mut T) -> bool {
@@ -403,6 +413,16 @@ impl<T> Eq for *mut T {
     fn ne(&self, other: &*mut T) -> bool { !self.eq(other) }
 }
 
+#[cfg(not(stage0), not(test))]
+impl<T> Eq for *mut T {
+    #[inline]
+    fn eq(&self, other: &*mut T) -> bool {
+        *self == *other
+    }
+    #[inline]
+    fn ne(&self, other: &*mut T) -> bool { !self.eq(other) }
+}
+
 // Equivalence for pointers
 #[cfg(not(test))]
 impl<T> Equiv<*mut T> for *T {
@@ -460,7 +480,7 @@ mod externfnpointers {
 }
 
 // Comparison for pointers
-#[cfg(not(test))]
+#[cfg(stage0, not(test))]
 impl<T> Ord for *T {
     #[inline]
     fn lt(&self, other: &*T) -> bool {
@@ -480,7 +500,27 @@ impl<T> Ord for *T {
     }
 }
 
-#[cfg(not(test))]
+#[cfg(not(stage0), not(test))]
+impl<T> Ord for *T {
+    #[inline]
+    fn lt(&self, other: &*T) -> bool {
+        *self < *other
+    }
+    #[inline]
+    fn le(&self, other: &*T) -> bool {
+        *self <= *other
+    }
+    #[inline]
+    fn ge(&self, other: &*T) -> bool {
+        *self >= *other
+    }
+    #[inline]
+    fn gt(&self, other: &*T) -> bool {
+        *self > *other
+    }
+}
+
+#[cfg(stage0, not(test))]
 impl<T> Ord for *mut T {
     #[inline]
     fn lt(&self, other: &*mut T) -> bool {
@@ -500,6 +540,26 @@ impl<T> Ord for *mut T {
     }
 }
 
+#[cfg(not(stage0), not(test))]
+impl<T> Ord for *mut T {
+    #[inline]
+    fn lt(&self, other: &*mut T) -> bool {
+        *self < *other
+    }
+    #[inline]
+    fn le(&self, other: &*mut T) -> bool {
+        *self <= *other
+    }
+    #[inline]
+    fn ge(&self, other: &*mut T) -> bool {
+        *self >= *other
+    }
+    #[inline]
+    fn gt(&self, other: &*mut T) -> bool {
+        *self > *other
+    }
+}
+
 #[cfg(test)]
 pub mod ptr_tests {
     use super::*;