Fix an error in a keyed lookup stub - HeapNumbers treated as strings.

test/mjsunit/regress/regress-155924.js

+// Copyright 2009 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.
+
+// A HeapNumber with certain bits in the mantissa of the floating point
+// value should not be able to masquerade as a string in a keyed lookup
+// inline cache stub.  See http://codereview.chromium.org/155924.
+
+A = [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 ];
+
+function foo() {
+  x = 1 << 26;
+  x = x * x;
+  // The following floating-point heap number has a second word similar
+  // to that of the string "5":
+  // 2^52 + index << cached_index_shift + cached_index_tag
+  x = x + (5 << 2) + (1 << 1);
+  return A[x];
+}
+
+assertEquals(undefined, foo(), "First lookup A[bad_float]");
+assertEquals(undefined, foo(), "Second lookup A[bad_float]");
+assertEquals(undefined, foo(), "Third lookup A[bad_float]");