regress-1708.js revision 3ef787dbeca8a5fb1086949cda830dccee07bfbd 
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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// Flags: --expose-gc --noincremental-marking --max-new-space-size 1000
32
33(function() {
34  var head = new Array(1);
35  var tail = head;
36
37  // Fill heap to increase old-space size and trigger lazy sweeping on
38  // some of the old-space pages.
39  for (var i = 0; i < 200; i++) {
40    tail[1] = new Array(1000);
41    tail = tail[1];
42  }
43  array = new Array(100);
44  gc(); gc();
45
46  // At this point "array" should have been promoted to old-space and be
47  // located in a lazy swept page with intact marking bits. Now shift
48  // the array to trigger left-trimming operations.
49  assertEquals(100, array.length);
50  for (var i = 0; i < 50; i++) {
51    array.shift();
52  }
53  assertEquals(50, array.length);
54
55  // At this point "array" should have been trimmed from the left with
56  // marking bits being correctly transfered to the new object start.
57  // Scavenging operations cause lazy sweeping to advance and verify
58  // that marking bit patterns are still sane.
59  for (var i = 0; i < 200; i++) {
60    tail[1] = new Array(1000);
61    tail = tail[1];
62  }
63})();
64