Properly set ElementsKind of empty FAST_DOUBLE_ELEMENTS arrays when transitioning.

test/mjsunit/regress/regress-117409.js

Index: test/mjsunit/regress/regress-117409.js
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+// Copyright 2012 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --expose-gc
+
+function KeyedStoreIC(a) { a[0] = Math.E; }
+
+// literal with a fast double elements backing store

[Jakob Kummerow, 2012/05/09 15:02:58]

nit: Proper sentences with capitalization and full stop, please. (More below.)

+var literal = [1.2];
+
+// specialize the IC for fast double elements
+KeyedStoreIC(literal);
+KeyedStoreIC(literal);
+
+// truncate js array to 0 elements:
+//   backing store will be replaces with empty fixed array

[Jakob Kummerow, 2012/05/09 15:02:58]

nit: replaced

+literal.length = 0;
+
+// ArrayPush built-in will replace empty fixed array backing
+// store with 19 elements fixed array backing store.
+// Leading to a mismatch between the map and the backing store.
+// Debug mode will crash here in set_elements accessor.
+literal.push(Math.E, Math.E);
+
+// Corrupt the backing store!
+KeyedStoreIC(literal);
+
+// Release mode will crash here when trying to visit parts of E as pointers.
+gc();