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27
28// Regression test of a very rare corner case where left-trimming an
29// array caused invalid marking bit patterns on lazily swept pages.
30//
31// Lazy sweeping was deprecated. We are keeping the test case to make
32// sure that concurrent sweeping, which relies on similar assumptions
33// as lazy sweeping works correctly.
34
35// Flags: --expose-gc --noincremental-marking --max-semi-space-size=1
36
37(function() {
38  var head = new Array(1);
39  var tail = head;
40
41  // Fill heap to increase old-space size and trigger concurrent sweeping on
42  // some of the old-space pages.
43  for (var i = 0; i < 200; i++) {
44    tail[1] = new Array(1000);
45    tail = tail[1];
46  }
47  array = new Array(100);
48  gc(); gc();
49
50  // At this point "array" should have been promoted to old-space and be
51  // located in a concurrently swept page with intact marking bits. Now shift
52  // the array to trigger left-trimming operations.
53  assertEquals(100, array.length);
54  for (var i = 0; i < 50; i++) {
55    array.shift();
56  }
57  assertEquals(50, array.length);
58
59  // At this point "array" should have been trimmed from the left with
60  // marking bits being correctly transfered to the new object start.
61  // Scavenging operations cause concurrent sweeping to advance and verify
62  // that marking bit patterns are still sane.
63  for (var i = 0; i < 200; i++) {
64    tail[1] = new Array(1000);
65    tail = tail[1];
66  }
67})();
68