Remove over-zealous hole checking in Array.slice()

test/mjsunit/regress/regress-165637.js

+// Copyright 2009 the V8 project authors. All rights reserved.

[Jakob Kummerow, 2012/12/12 14:28:57]

nit: 2012

+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
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+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Should not take a very long time (n^2 algorithms are bad)
+
+function do_slices() {
+  var data = new Array(1024 * 12); // 12kB
+
+  for (var i = 0; i < data.length; i++) {
+    data[i] = 255;
+  }
+
+  var start = Date.now();
+
+  for (i = 0; i < 20000; i++) {
+    data.slice(4, 1);
+  }
+
+  return Date.now() - start;
+}
+
+// Should never take more than 3 seconds (if the bug is fixed, the test takes
+// considerably less time than 3 seconds).
+assertTrue(do_slices() < (3 * 1000));
+
+// Make sure that packed and unpacked array slices are still properly handled
+var holey_array = [1, 2, 3, 4, 5,,,,,,];
+assertFalse(%HasFastHoleyElements(holey_array.slice(6, 1)));

[Jakob Kummerow, 2012/12/12 14:28:57]

needs --allow-natives-syntax

+assertEquals(undefined, holey_array.slice(6, 7)[0])
+assertFalse(%HasFastHoleyElements(holey_array.slice(2, 1)));
+assertEquals(3, holey_array.slice(2, 3)[0])