1 files changed, 39 insertions, 0 deletions
diff --git a/js/src/jit-test/manual-tests/dense-to-sparse.js b/js/src/jit-test/manual-tests/dense-to-sparse.js
new file mode 100644
index 0000000000..006b77442b
--- /dev/null
+++ b/js/src/jit-test/manual-tests/dense-to-sparse.js
@@ -0,0 +1,39 @@
+// |jit-test| allow-oom
+// Appending elements to a dense array should make the array sparse when the
+// length exceeds the limit.
+
+function test() {
+  const MAX_DENSE_ELEMENTS_ALLOCATION = (1 << 28) - 1;
+  const VALUES_PER_HEADER = 2;
+  const MAX_DENSE_ELEMENTS_COUNT = MAX_DENSE_ELEMENTS_ALLOCATION - VALUES_PER_HEADER;
+  const SPARSE_DENSITY_RATIO = 8;
+  const MIN_DENSE = MAX_DENSE_ELEMENTS_COUNT / SPARSE_DENSITY_RATIO;
+  const MARGIN = 16;
+
+  let a = [];
+  // Fill the beginning of array to make it keep dense until length exceeds
+  // MAX_DENSE_ELEMENTS_COUNT.
+  for (let i = 0; i < MIN_DENSE; i++)
+    a[i] = i;
+
+  // Skip from MIN_DENSE to MAX_DENSE_ELEMENTS_COUNT - MARGIN, to reduce the
+  // time taken by test.
+
+  // Fill the ending of array to make it sparse at MAX_DENSE_ELEMENTS_COUNT.
+  for (let i = MAX_DENSE_ELEMENTS_COUNT - MARGIN; i < MAX_DENSE_ELEMENTS_COUNT + MARGIN; i++)
+    a[i] = i;
+
+  // Make sure the last element is defined.
+  assertEq(a.length, MAX_DENSE_ELEMENTS_COUNT + MARGIN);
+  assertEq(a[a.length - 1], MAX_DENSE_ELEMENTS_COUNT + MARGIN - 1);
+
+  // Make sure elements around MAX_DENSE_ELEMENTS_COUNT are also defined.
+  assertEq(a[MAX_DENSE_ELEMENTS_COUNT - 1], MAX_DENSE_ELEMENTS_COUNT - 1);
+  assertEq(a[MAX_DENSE_ELEMENTS_COUNT], MAX_DENSE_ELEMENTS_COUNT);
+  assertEq(a[MAX_DENSE_ELEMENTS_COUNT + 1], MAX_DENSE_ELEMENTS_COUNT + 1);
+}
+
+// Takes too long time on debug build.
+if (!getBuildConfiguration("debug")) {
+  test();
+}