Fix for issue 341. In the stub for instanceof, we could try to read...

src/ia32/codegen-ia32.cc

 // Copyright 2006-2009 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 7168 matching lines @@
 
 
 void InstanceofStub::Generate(MacroAssembler* masm) {
   // Get the object - go slow case if it's a smi.
   Label slow;
   __ mov(eax, Operand(esp, 2 * kPointerSize));  // 2 ~ return address, function
   __ test(eax, Immediate(kSmiTagMask));
   __ j(zero, &slow, not_taken);
 
   // Check that the left hand is a JS object.
   __ mov(eax, FieldOperand(eax, HeapObject::kMapOffset));  // ebx - object map

[Kasper Lund, 2009/05/12 11:32:12]

Why does this say ebx - object map?

[Kevin Millikin (Chromium), 2009/05/12 11:39:46]

Weird.

   __ movzx_b(ecx, FieldOperand(eax, Map::kInstanceTypeOffset));  // ecx - type
   __ cmp(ecx, FIRST_JS_OBJECT_TYPE);
   __ j(less, &slow, not_taken);
   __ cmp(ecx, LAST_JS_OBJECT_TYPE);
   __ j(greater, &slow, not_taken);
 
   // Get the prototype of the function.
   __ mov(edx, Operand(esp, 1 * kPointerSize));  // 1 ~ return address
   __ TryGetFunctionPrototype(edx, ebx, ecx, &slow);
 
   // Check that the function prototype is a JS object.
+  __ test(ebx, Immediate(kSmiTagMask));
+  __ j(zero, &slow, not_taken);
   __ mov(ecx, FieldOperand(ebx, HeapObject::kMapOffset));
   __ movzx_b(ecx, FieldOperand(ecx, Map::kInstanceTypeOffset));
   __ cmp(ecx, FIRST_JS_OBJECT_TYPE);
   __ j(less, &slow, not_taken);
   __ cmp(ecx, LAST_JS_OBJECT_TYPE);
   __ j(greater, &slow, not_taken);
 
   // Register mapping: eax is object map and ebx is function prototype.
   __ mov(ecx, FieldOperand(eax, Map::kPrototypeOffset));
 
@@ skipping 18 matching lines @@
 
   // Slow-case: Go through the JavaScript implementation.
   __ bind(&slow);
   __ InvokeBuiltin(Builtins::INSTANCE_OF, JUMP_FUNCTION);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal