Make instanceof and Object.getPrototypeOf work for proxies, plus a few other tweaks.

src/x64/builtins-x64.cc

 // 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
@@ skipping 345 matching lines @@
 
   // If the result is an object (in the ECMA sense), we should get rid
   // of the receiver and use the result; see ECMA-262 section 13.2.2-7
   // on page 74.
   Label use_receiver, exit;
   // If the result is a smi, it is *not* an object in the ECMA sense.
   __ JumpIfSmi(rax, &use_receiver);
 
   // If the type of the result (stored in its map) is less than
   // FIRST_SPEC_OBJECT_TYPE, it is not an object in the ECMA sense.
+  STATIC_ASSERT(LAST_SPEC_OBJECT_TYPE == LAST_TYPE);
   __ CmpObjectType(rax, FIRST_SPEC_OBJECT_TYPE, rcx);
   __ j(above_equal, &exit);
 
   // Throw away the result of the constructor invocation and use the
   // on-stack receiver as the result.
   __ bind(&use_receiver);
   __ movq(rax, Operand(rsp, 0));
 
   // Restore the arguments count and leave the construct frame.
   __ bind(&exit);
@@ skipping 1137 matching lines @@
   Deoptimizer::EntryGenerator generator(masm, Deoptimizer::OSR);
   generator.Generate();
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64