1 files changed, 18 insertions, 0 deletions
diff --git a/js/src/jit-test/tests/warp/string-charCodeAt-constant-index-in-left-rope-child.js b/js/src/jit-test/tests/warp/string-charCodeAt-constant-index-in-left-rope-child.js
new file mode 100644
index 0000000000..5835b019ad
--- /dev/null
+++ b/js/src/jit-test/tests/warp/string-charCodeAt-constant-index-in-left-rope-child.js
@@ -0,0 +1,18 @@
+// `str.charCodeAt(0)` doesn't need to inspect the right rope child, because
+// the first character is guaranteed to be in the left child.
+
+const ropes = [
+  newRope("ABCDEFGHIJKL", "MNOPQRSTUVWXYZ"),
+  newRope("abcdefghijkl", "mnopqrstuvwxyz"),
+
+  newRope("A", "BCDEFGHIJKLMNOPQRSTUVWXYZ"),
+  newRope("a", "bcdefghijklmnopqrstuvwxyz"),
+];
+
+for (let i = 0; i < 500; ++i) {
+  let rope = ropes[i & 3];
+
+  let actual = rope.charCodeAt(0);
+  let expected = 0x41 + (i & 1) * 0x20;
+  assertEq(actual, expected);
+}