1 files changed, 51 insertions, 0 deletions
diff --git a/js/src/jit-test/tests/arrays/spreadnew-optimization.js b/js/src/jit-test/tests/arrays/spreadnew-optimization.js
new file mode 100644
index 0000000000..d676bdb753
--- /dev/null
+++ b/js/src/jit-test/tests/arrays/spreadnew-optimization.js
@@ -0,0 +1,51 @@
+// Test case adapted from "apply-optimization.js" to test SpreadNew instead of FunApply.
+
+// Uses fewer iterations than "apply-optimization.js" to keep the overall runtime reasonable.
+const iterations = 40;
+
+function make(k) {
+    var a = new Array(k);
+    for ( let i=0 ; i < k ; i++ )
+        a[i] = {}
+    return a;
+}
+
+function g() {
+    // Ensure |new.target| and |this| are correct.
+    assertEq(new.target, g);
+    assertEq(typeof this, "object");
+    assertEq(Object.getPrototypeOf(this), g.prototype);
+
+    // Returns a Number object, because constructor calls need to return an object!
+    return new Number(arguments.length);
+}
+
+function f(a) {
+    var sum = 0;
+    for ( let i=0 ; i < iterations ; i++ )
+        sum += new g(...a);
+    return sum;
+}
+
+function time(k, t) {
+    var then = Date.now();
+    assertEq(t(), iterations*k);
+    var now = Date.now();
+    return now - then;
+}
+
+function p(v) {
+    // Uncomment to see timings
+    // print(v);
+}
+
+f(make(200));
+
+// There is currently a cutoff after 375 where we bailout in order to avoid
+// handling very large stack frames.  This slows the operation down by a factor
+// of 100 or so.
+
+p(time(374, () => f(make(374))));
+p(time(375, () => f(make(375))));
+p(time(376, () => f(make(376))));
+p(time(377, () => f(make(377))));