Only fold polymorphic into monomorphic load if all load from either receiver or same prototype.

R=jkummerow@chromium.org

Review URL: https://chromiumcodereview.appspot.com/25718002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@17078 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/hydrogen.cc

@@ -4707,10 +4707,14 @@ bool HOptimizedGraphBuilder::PropertyAccessInfo::IsCompatibleForLoad(
   if (!LookupDescriptor()) return false;
 
   if (!lookup_.IsFound()) {
-    return (!info->lookup_.IsFound() || !info->holder_.is_null()) &&
+    return (!info->lookup_.IsFound() || info->has_holder()) &&
         map_->prototype() == info->map_->prototype();
   }
 
+  // Mismatch if the other access info found the property in the prototype
+  // chain.
+  if (info->has_holder()) return false;
+
   if (lookup_.IsPropertyCallbacks()) {
     return accessor_.is_identical_to(info->accessor_);
   }

test/mjsunit/regress/regress-polymorphic-load.js

+// Copyright 2013 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 f(o) {
+  return o.x;
+}
+
+var o1 = {x:1};
+var o2 = {__proto__: {x:2}};
+
+f(o2);
+f(o2);
+f(o2);
+f(o1);
+%OptimizeFunctionOnNextCall(f);
+assertEquals(1, f(o1));
+assertEquals(2, f(o2));