incr.comp.: Use 128-bit Metrohash instead of BLAKE2 for computing ICHs.

src/librustc/ich/fingerprint.rs

@@ -9,8 +9,8 @@
 // except according to those terms.
 
 use rustc_data_structures::stable_hasher;
-use std::mem;
-use std::slice;
+// use std::mem;
+// use std::slice;
 
 #[derive(Eq, PartialEq, Ord, PartialOrd, Hash, Debug, Clone, Copy, RustcEncodable, RustcDecodable)]
 pub struct Fingerprint(u64, u64);
@@ -55,15 +55,8 @@ impl ::std::fmt::Display for Fingerprint {
 
 impl stable_hasher::StableHasherResult for Fingerprint {
     fn finish(mut hasher: stable_hasher::StableHasher<Self>) -> Self {
-        let hash_bytes: &[u8] = hasher.finalize();
-
-        assert!(hash_bytes.len() >= mem::size_of::<u64>() * 2);
-        let hash_bytes: &[u64] = unsafe {
-            slice::from_raw_parts(hash_bytes.as_ptr() as *const u64, 2)
-        };
-
-        // The bytes returned bytes the Blake2B hasher are always little-endian.
-        Fingerprint(u64::from_le(hash_bytes[0]), u64::from_le(hash_bytes[1]))
+        let (_0, _1) = hasher.finalize();
+        Fingerprint(_0, _1)
     }
 }
 

src/librustc_data_structures/lib.rs

@@ -28,6 +28,7 @@
 #![feature(fn_traits)]
 #![feature(unsize)]
 #![feature(i128_type)]
+#![feature(i128)]
 #![feature(conservative_impl_trait)]
 #![feature(specialization)]