Ensure that GenerateStoreFastDoubleElement returns stored value on all paths.

test/mjsunit/regress/regress-91013.js

Index: test/mjsunit/regress/regress-91013.js
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+// Copyright 2011 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.
+
+// Test that KeyedStore stub for unboxed double arrays backing store
+// correctly returns stored value as the result.
+
+// Flags: --allow-natives-syntax --unbox-double-arrays
+
+// Create array with unboxed double array backing store.
+var i = 100000;
+var a = new Array(i);
+for (var j = 0; j < i; j++) {
+  a[j] = 0.5;
+}
+
+assertTrue(%HasFastDoubleElements(a));
+
+// Store some smis into it.
+for (var j = 0; j < 10; j++) {
+  assertEquals(j, a[j] = j);
+}
+
+// Store some heap numbers into it.
+for (var j = 0; j < 10; j++) {
+  var v = j + 0.5;
+  assertEquals(v, a[j] = v);
+}