Fix polymorphic load on named fields.

This fixes polymorphic loads to correctly compare in-object offsets
instead of indices, because indices might coincide even though the
actual slot is different because of different instance sizes.

R=danno@chromium.org
BUG=v8:2030
TEST=mjsunit/regress/regress-2030,mjsunit/mirror-array

Review URL: https://chromiumcodereview.appspot.com/9864028

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11153 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/hydrogen.cc

@@ -4029,7 +4029,8 @@ void HGraphBuilder::HandlePolymorphicLoadNamedField(Property* expr,
                                                     SmallMapList* types,
                                                     Handle<String> name) {
   int count = 0;
-  int previous_field_index = 0;
+  int previous_field_offset = 0;
+  bool previous_field_is_in_object = false;
   bool is_monomorphic_field = true;
   Handle<Map> map;
   LookupResult lookup(isolate());
@@ -4037,10 +4038,21 @@ void HGraphBuilder::HandlePolymorphicLoadNamedField(Property* expr,
     map = types->at(i);
     if (ComputeLoadStoreField(map, name, &lookup, false)) {
       int index = ComputeLoadStoreFieldIndex(map, name, &lookup);
+      bool is_in_object = index < 0;
+      int offset = index * kPointerSize;
+      if (index < 0) {
+        // Negative property indices are in-object properties, indexed
+        // from the end of the fixed part of the object.
+        offset += map->instance_size();
+      } else {
+        offset += FixedArray::kHeaderSize;
+      }
       if (count == 0) {
-        previous_field_index = index;
+        previous_field_offset = offset;
+        previous_field_is_in_object = is_in_object;
       } else if (is_monomorphic_field) {
-        is_monomorphic_field = (index == previous_field_index);
+        is_monomorphic_field = (offset == previous_field_offset) &&
+                               (is_in_object == previous_field_is_in_object);
       }
       ++count;
     }

test/mjsunit/regress/regress-2030.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 a() {
+  this.x = 1;
+}
+var aa = new a();
+%DebugPrint(aa);
+
+function b() {
+  this.z = 23;
+  this.x = 2;
+}
+var bb = new b();
+%DebugPrint(bb);
+
+function f(o) {
+  return o.x;
+}
+
+assertSame(1, f(aa));
+assertSame(1, f(aa));
+assertSame(2, f(bb));
+assertSame(2, f(bb));
+%OptimizeFunctionOnNextCall(f);
+assertSame(1, f(aa));
+assertSame(2, f(bb));