1 files changed, 50 insertions, 0 deletions
diff --git a/js/src/jit-test/tests/gc/pretenuring.js b/js/src/jit-test/tests/gc/pretenuring.js
new file mode 100644
index 0000000000..6f20706e9b
--- /dev/null
+++ b/js/src/jit-test/tests/gc/pretenuring.js
@@ -0,0 +1,50 @@
+// Test nursery string allocation and pretenuring.
+
+gczeal(0);
+
+gcparam("minNurseryBytes", 4096 * 1024);
+gcparam("maxNurseryBytes", 4096 * 1024);
+gc();
+
+// String allocation in the nursery is initially enabled.
+assertEq(nurseryStringsEnabled(), true);
+
+// Literal strings are atoms (which are always tenured).
+assertEq(isNurseryAllocated("foo"), false);
+
+// The result of Number.toString is nursery allocated.
+assertEq(isNurseryAllocated((1234).toString()), true);
+
+// Ropes are nursery allocated.
+let s = "bar";
+assertEq(isNurseryAllocated("foo" + s), true);
+
+// Dependent strings are nursery allocated.
+assertEq(isNurseryAllocated("foobar".substr(1)), true);
+
+// The testing function 'newString' allows control over which heap is used.
+assertEq(isNurseryAllocated(newString("foobar", { tenured: true })), false);
+assertEq(isNurseryAllocated(newString("foobar", { tenured: false })), true);
+
+// Allocating lots of strings which survive nursery collection disables
+// allocating strings in the nursery.
+let a = [];
+for (let i = 1; i < 500000; i++) {
+  a.push(i.toString());
+}
+gc();
+assertEq(nurseryStringsEnabled(), false);
+a = undefined;
+
+// When a large number of tenured strings die very soon after allocation,
+// pretenuring for that zone is reset and nursery allocation enabled again.
+
+gc();
+assertEq(nurseryStringsEnabled(), false);
+let initGCNumber = gcparam('majorGCNumber');
+while (!nurseryStringsEnabled() && gcparam('majorGCNumber') < initGCNumber + 3) {
+  for (let i = 1; i < 100000; i++) {
+    a = i.toString();
+  }
+}
+assertEq(nurseryStringsEnabled(), true);