Add an IsEqual FieldPredicate.

Compare an immediate operand to a constant value.

lib/cretonne/src/predicates.rs

@@ -9,6 +9,12 @@
 //! Some of these predicates may be unused in certain ISA configurations, so we suppress the
 //! dead_code warning.
 
+/// Check that `x` is the same as `y`.
+#[allow(dead_code)]
+pub fn is_equal<T: Eq + Copy>(x: T, y: T) -> bool {
+    x == y
+}
+
 /// Check that `x` can be represented as a `wd`-bit signed integer with `sc` low zero bits.
 #[allow(dead_code)]
 pub fn is_signed_int<T: Into<i64>>(x: T, wd: u8, sc: u8) -> bool {