Add instrumentation in the TemplateInterpreter

[Christian Thalinger]

Can you share the reason?

> On Feb 18, 2016, at 8:01 AM, Khanh Nguyen <ktruong.nguyen at gmail.com> wrote:
> 
> Unfortunately it has to be the Template Interpreter.
> 
> On Feb 18, 2016 9:27 AM, "Christian Thalinger" <christian.thalinger at oracle.com <mailto:christian.thalinger at oracle.com>> wrote:
> Does it have to be the template interpreter or could you do your work with Zero as well?
> 
> > On Feb 9, 2016, at 11:19 PM, Khanh Nguyen <ktruong.nguyen at gmail.com <mailto:ktruong.nguyen at gmail.com>> wrote:
> >
> > Hello,
> >
> > I want to add instrumentation to monitor all reads and writes in the
> > TemplateInterpreter, I think I got the correct place for it in
> > /cpu/x86/vm/templateTable_x86_64.cpp. Can someone please tell me if I'm
> > doing it right?
> >
> > For writes:
> > static void do_oop_store(InterpreterMacroAssembler* _masm,
> >                         Address obj,
> >                         Register val,
> >                         BarrierSet::Name barrier,
> >                         bool precise) {
> > [...]
> > case BarrierSet::CardTableModRef:
> >  case BarrierSet::CardTableExtension:
> >      {
> >        if (val == noreg) {
> >          __ store_heap_oop_null(obj);
> >        } else {
> >          __ store_heap_oop(obj, val);
> >
> > /*mycodeA*/  __ movptr(c_rarg1, obj.base()); // save this value otherwise
> > it will be changed?
> >
> >          // flatten object address if needed
> >          if (!precise || (obj.index() == noreg && obj.disp() == 0)) {
> >            __ store_check(obj.base());
> > /*mycodeB*/ __ call_VM(noreg, //void
> >                       CAST_FROM_FN_PTR(address,
> >                                        InterpreterRuntime::write_helper),
> >                       c_rarg1,  // obj
> >                       c_rarg1, // field address because store check is
> > called on field address
> >                       val);
> >          } else {
> >            __ leaq(rdx, obj);
> >            __ store_check(rdx);
> > /*mycodeC*/ __ call_VM(noreg, //void
> >                         CAST_FROM_FN_PTR(address,
> >                                          InterpreterRuntime::write_helper),
> >                         c_rarg1,  // obj
> >                         rdx, // field address, because store check is
> > called on field address
> >                         val);
> >        }
> >      }
> >      break;
> >
> > For reads:
> > case Bytecodes::_fast_agetfield:
> >    __ load_heap_oop(rax, field);
> >
> > /*mycodeD*/     __ call_VM(noreg,
> >               CAST_FROM_FN_PTR(address,
> >                                InterpreterRuntime::read_barrier_helper),
> >               rax);
> >
> > __ verify_oop(rax);
> >    break;
> >
> > My questions are:
> >
> > 1) I thought this represents a putfield a.f=b where a.f is represented by
> > the parameter obj of type Address. b is obvious the parameter val of type
> > Register. Especially in obj there are fields: base, index and disp. But as
> > I run this, looks like obj is actually the field address. (the case mycodeB)
> > I haven't found a test case that can trigger the case mycodeC to see the
> > behavior (i.e., rdx might get destroyed and I got random value back or
> > c_rarg1 is the obj address and rdx is field address)
> >
> > 2) Before this, I tried to insert the same __ call_VM in fast_aputfield
> > before do_oop_store but it results in JVM crash. I don't understand the
> > reason why. What I did in the call is just print the parameters. I did see
> > the values printed (only the 1st time it goes to the method) but then the
> > VM crashed. I thought __ call_VM will preserve all registers's value and
> > restore properly when comes back. My instrumentation has no side effect, I
> > just observe and record the values (actually just printing the values to
> > test).
> >
> > 3) Is it strictly required to have the line /*mycodeA*/ I tried to, in
> > mycodeB line, pass obj.base() twice and it got build errors for "smashed
> > args"?
> >
> > I greatly appreciate your time,
> >
> > Best,
> >
> > Khanh Nguyen
>