1 files changed, 50 insertions, 0 deletions
diff --git a/js/src/jit-test/tests/warp/compare-empty-string.js b/js/src/jit-test/tests/warp/compare-empty-string.js
new file mode 100644
index 0000000000..30cf03f874
--- /dev/null
+++ b/js/src/jit-test/tests/warp/compare-empty-string.js
@@ -0,0 +1,50 @@
+// Test case to cover empty string comparison folding.
+//
+// MCompare can fold comparison with an empty string constant and replace it
+// with |string.length <op> 0|.
+
+const strings = [
+  // Zero length string.
+  "",
+
+  // Uncommon zero length strings.
+  newString("", {external: true}),
+
+  // Latin-1 strings.
+  "a",
+  "ä",
+  "monkey",
+
+  // Two-byte strings.
+  "猿",
+  "🐒",
+  newString("monkey", {twoByte: true}),
+];
+
+const operators = [
+  "==", "===", "!=", "!==",
+  "<", "<=", ">=", ">",
+];
+
+for (let op of operators) {
+  let lhs = x => `${x} ${op} ""`;
+  let rhs = x => `"" ${op} ${x}`;
+
+  for (let input of [lhs, rhs]) {
+    let fn = Function("strings", `
+      const expected = strings.map(x => {
+        // Prevent Warp compilation when computing the expected results.
+        with ({}) ;
+        return ${input("x")};
+      });
+
+      for (let i = 0; i < 200; ++i) {
+        let idx = i % strings.length;
+        let str = strings[idx];
+        let res = ${input("str")};
+        assertEq(res, expected[idx]);
+      }
+    `);
+    fn(strings);
+  }
+}