Introduce FieldIndex to unify and abstract property/field offset

test/mjsunit/outobject-double-for-in.js

 // 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: --allow-natives-syntax
 
-function crash(obj) {
-  return obj.foo;
+function DoubleContainer() {
+  this.x0 = 0.5;
+  this.x1 = undefined;
+  this.x2 = undefined;
+  this.x3 = undefined;
+  this.x4 = undefined;
+  this.x5 = undefined;
+  this.x6 = undefined;
+  this.x7 = 5;
+  this.x8 = undefined;
+  this.x9 = undefined;
+  this.x10 = undefined;
+  this.x11 = undefined;
+  this.x12 = undefined;
+  this.x13 = undefined;
+  this.x14 = undefined;
+  this.x15 = undefined;
+  this.x16 = true;
+  this.y = 2.5;
 }
 
-function base(number_of_properties) {
-  var result = new Array();
-  for (var i = 0; i < number_of_properties; i++) {
-    result["property" + i] = "value" + i;
+var z = new DoubleContainer();
+
+function test_props(a) {
+  for (var i in a) {
+    assertTrue(i !== "x0" || a[i] === 0.5);
+    assertTrue(i !== "y" || a[i] === 2.5);
+    assertTrue(i !== "x12" || a[i] === undefined);
+    assertTrue(i !== "x16" || a[i] === true);
+    assertTrue(i !== "x7" || a[i] === 5);
   }
-  result.foo = number_of_properties;
-  return result;
 }
 
-var a = base(12);
-var b = base(13);
-var c = base(14);
-var d = base(15);
-
-crash(a);  // Premonomorphic.
-crash(a);
-crash(b);
-crash(c);
-crash(d);  // Polymorphic, degree 4.
-
-//Prepare ElementsKind transition map chain.
-var x = base(13);
-x[0] = "object";
-x = base(14);
-x[0] = "object";
-x = base(15);
-x[0] = "object";
-
-%OptimizeFunctionOnNextCall(crash);
-crash(a);
+test_props(z);
+test_props(z);
+%OptimizeFunctionOnNextCall(test_props);
+test_props(z);