Use the &>> operator in HashTest.

Gets rid of some obvious inefficiencies in this benchmark.

Author: Fidetro

benchmark/single-source/Hash.swift

@@ -113,19 +113,13 @@ class Hash {
   /// \brief Left-rotate \p x by \p c.
   final
   func rol(_ x: UInt32, _ c: UInt32) -> UInt32 {
-    // TODO: use the &>> operator.
-    let a = UInt32(truncatingIfNeeded: Int64(x) << Int64(c))
-    let b = UInt32(truncatingIfNeeded: Int64(x) >> (32 - Int64(c)))
-    return a|b
+    return x &<< c | x &>> (32 &- c)
   }
 
   /// \brief Right-rotate \p x by \p c.
   final
   func ror(_ x: UInt32, _ c: UInt32) -> UInt32 {
-    // TODO: use the &>> operator.
-    let a = UInt32(truncatingIfNeeded: Int64(x) >> Int64(c))
-    let b = UInt32(truncatingIfNeeded: Int64(x) << (32 - Int64(c)))
-    return a|b
+    return x &>> c | x &<< (32 &- c)
   }
 }