Get rid of the HInstanceSize instruction.

src/x64/lithium-codegen-x64.cc

 // 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
@@ skipping 2519 matching lines @@
   Label done;
   __ j(not_zero, &load_false);
   __ LoadRoot(rax, Heap::kTrueValueRootIndex);
   __ jmp(&done);
   __ bind(&load_false);
   __ LoadRoot(rax, Heap::kFalseValueRootIndex);
   __ bind(&done);
 }
 
 
-void LCodeGen::DoInstanceSize(LInstanceSize* instr) {
-  Register object = ToRegister(instr->object());
-  Register result = ToRegister(instr->result());
-  __ movq(result, FieldOperand(object, HeapObject::kMapOffset));
-  __ movzxbq(result, FieldOperand(result, Map::kInstanceSizeOffset));
-}
-
-
 void LCodeGen::DoCmpT(LCmpT* instr) {
   Token::Value op = instr->op();
 
   Handle<Code> ic = CompareIC::GetUninitialized(isolate(), op);
   CallCode(ic, RelocInfo::CODE_TARGET, instr);
 
   Condition condition = TokenToCondition(op, false);
   Label true_value, done;
   __ testq(rax, rax);
   __ j(condition, &true_value, Label::kNear);
@@ skipping 2882 matching lines @@
                                FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64