Make DescriptorArray::IsMoreGeneralThan() and DescriptorArray::Merge() compatible again.

BUG=365172
LOG=y
TEST=mjsunit/regress/regress-365172-[1-3]
R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/255513005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@20922 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/objects.cc

@@ -8520,6 +8520,10 @@ bool DescriptorArray::IsMoreGeneralThan(int verbatim,
     if (details.type() == CONSTANT) {
       if (other_details.type() != CONSTANT) return false;
       if (GetValue(descriptor) != other->GetValue(descriptor)) return false;
+    } else if (details.type() == FIELD && other_details.type() == FIELD) {
+      if (!other->GetFieldType(descriptor)->NowIs(GetFieldType(descriptor))) {
+        return false;
+      }
     }
   }
 

test/mjsunit/regress/regress-365172-1.js

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --track-field-types
+
+var b1 = {d: 1}; var b2 = {d: 2};
+var f1 = {x: 1}; var f2 = {x: 2};
+f1.b = b1;
+f2.x = {};
+b2.d = 4.2;
+f2.b = b2;
+var x = f1.x;

test/mjsunit/regress/regress-365172-2.js

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax --track-field-types
+
+var b1 = {d: 1}; var b2 = {d: 2};
+var f1 = {x: 1}; var f2 = {x: 2};
+f1.b = b1;
+f2.x = {};
+b2.d = 4.2;
+f2.b = b2;
+%TryMigrateInstance(f1);

test/mjsunit/regress/regress-365172-3.js

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --expose-gc --track-field-types
+
+function f1(a) { return {x:a, v:''}; }
+function f2(a) { return {x:{v:a}, v:''}; }
+function f3(a) { return {x:[], v:{v:''}}; }
+f3([0]);
+a = f1(1);
+a.__defineGetter__('v', function() { gc(); return f2(this); });
+a.v;
+f3(1);