Fix crashes during GC caused by partially initialized objects. The...

src/x64/macro-assembler-x64.h

 // Copyright 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 932 matching lines @@
   void EnterExitFramePrologue(bool save_rax);
 
   // Allocates arg_stack_space * kPointerSize memory (not GCed) on the stack
   // accessible via StackSpaceOperand.
   void EnterExitFrameEpilogue(int arg_stack_space);
 
   void LeaveExitFrameEpilogue();
 
   // Allocation support helpers.
   // Loads the top of new-space into the result register.
-  // If flags contains RESULT_CONTAINS_TOP then result_end is valid and
-  // already contains the top of new-space, and scratch is invalid.
   // Otherwise the address of the new-space top is loaded into scratch (if
   // scratch is valid), and the new-space top is loaded into result.
   void LoadAllocationTopHelper(Register result,
-                               Register result_end,
                                Register scratch,
                                AllocationFlags flags);
   // Update allocation top with value in result_end register.
   // If scratch is valid, it contains the address of the allocation top.
   void UpdateAllocationTopHelper(Register result_end, Register scratch);
 
   // Helper for PopHandleScope.  Allowed to perform a GC and returns
   // NULL if gc_allowed.  Does not perform a GC if !gc_allowed, and
   // possibly returns a failure object indicating an allocation failure.
   Object* PopHandleScopeHelper(Register saved,
@@ skipping 771 matching lines @@
       Jump(adaptor, RelocInfo::CODE_TARGET);
     }
     bind(&invoke);
   }
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_X64_MACRO_ASSEMBLER_X64_H_