Move simple_hash into its own module.

src/libcretonne/simple_hash.rs

@@ -0,0 +1,21 @@
+/// A primitive hash function for matching opcodes.
+/// Must match `meta/constant_hash.py`.
+pub fn simple_hash(s: &str) -> u32 {
+    let mut h: u32 = 5381;
+    for c in s.chars() {
+        h = (h ^ c as u32).wrapping_add(h.rotate_right(6));
+    }
+    h
+}
+
+#[cfg(test)]
+mod tests {
+    use super::simple_hash;
+
+    #[test]
+    fn basic() {
+        // c.f. meta/constant_hash.py tests.
+        assert_eq!(simple_hash("Hello"), 0x2fa70c01);
+        assert_eq!(simple_hash("world"), 0x5b0c31d5);
+    }
+}