From b31ca83b919f4724e9054ccfb6fb3ea7eeeb71d9 Mon Sep 17 00:00:00 2001
From: Jakob Stoklund Olesen <jolesen@mozilla.com>
Date: Fri, 31 Mar 2017 10:12:44 -0700
Subject: [PATCH] Add an IsEqual FieldPredicate.

Compare an immediate operand to a constant value.
---
 lib/cretonne/meta/cdsl/predicates.py | 15 +++++++++++++++
 lib/cretonne/src/predicates.rs       |  6 ++++++
 2 files changed, 21 insertions(+)

diff --git a/lib/cretonne/meta/cdsl/predicates.py b/lib/cretonne/meta/cdsl/predicates.py
index 8ba4c8eb41..e75920d948 100644
--- a/lib/cretonne/meta/cdsl/predicates.py
+++ b/lib/cretonne/meta/cdsl/predicates.py
@@ -232,6 +232,21 @@ class FieldPredicate(object):
         return 'predicates::{}({})'.format(self.function, ', '.join(args))
 
 
+class IsEqual(FieldPredicate):
+    """
+    Instruction predicate that checks if an immediate instruction format field
+    is equal to a constant value.
+
+    :param field: `FormatField` to be checked.
+    :param value: The constant value to compare against.
+    """
+
+    def __init__(self, field, value):
+        # type: (FormatField, Any) -> None
+        super(IsEqual, self).__init__(field, 'is_equal', (value,))
+        self.value = value
+
+
 class IsSignedInt(FieldPredicate):
     """
     Instruction predicate that checks if an immediate instruction format field
diff --git a/lib/cretonne/src/predicates.rs b/lib/cretonne/src/predicates.rs
index 748a75e23a..770857d100 100644
--- a/lib/cretonne/src/predicates.rs
+++ b/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 {