X87: [proxies] fix access issue when having proxies on the prototype-chain of global objects.

src/x87/code-stubs-x87.cc

 // Copyright 2012 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.
 
 #if V8_TARGET_ARCH_X87
 
 #include "src/base/bits.h"
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
 #include "src/codegen.h"
@@ skipping 2262 matching lines @@
   // {function}.  The cached answer will be set when it is known below.
   __ StoreRoot(function, scratch, Heap::kInstanceofCacheFunctionRootIndex);
   __ StoreRoot(object_map, scratch, Heap::kInstanceofCacheMapRootIndex);
 
   // Loop through the prototype chain looking for the {function} prototype.
   // Assume true, and change to false if not found.
   Label done, loop, fast_runtime_fallback;
   __ mov(eax, isolate()->factory()->true_value());
   __ bind(&loop);
 
+  // Check if the object needs to be access checked.
   __ test_b(FieldOperand(object_map, Map::kBitFieldOffset),
             1 << Map::kIsAccessCheckNeeded);
   __ j(not_zero, &fast_runtime_fallback, Label::kNear);
+  // Check if the current object is a Proxy.
   __ CmpInstanceType(object_map, JS_PROXY_TYPE);
   __ j(equal, &fast_runtime_fallback, Label::kNear);
 
   __ mov(object, FieldOperand(object_map, Map::kPrototypeOffset));
   __ cmp(object, function_prototype);
   __ j(equal, &done, Label::kNear);
+  __ mov(object_map, FieldOperand(object, HeapObject::kMapOffset));
   __ cmp(object, isolate()->factory()->null_value());
-  __ mov(object_map, FieldOperand(object, HeapObject::kMapOffset));
   __ j(not_equal, &loop);
   __ mov(eax, isolate()->factory()->false_value());
+
   __ bind(&done);
   __ StoreRoot(eax, scratch, Heap::kInstanceofCacheAnswerRootIndex);
   __ ret(0);
 
   // Found Proxy or access check needed: Call the runtime.
   __ bind(&fast_runtime_fallback);
   __ PopReturnAddressTo(scratch);
   __ Push(object);
   __ Push(function_prototype);
   __ PushReturnAddressFrom(scratch);
@@ skipping 3025 matching lines @@
                            Operand(ebp, 7 * kPointerSize), NULL);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X87