[9] RFR [XS] 8054492: Casting can result in redundant null checks in generated code

[Vladimir Kozlov]

I hope it is the final version.

http://cr.openjdk.java.net/~kvn/8054492/webrev.02/

Full blown intrinsic is created for Class.cast(). It tries, first, to 
fold statically the code. If it can't, it calls gen_checkcast() and 
generate uncommon trap when the exception have to be thrown. Also if we 
hit uncommon trap too match it will not generate instrinsic with dynamic 
checks during recompilation, but it still tries to fold it statically.

Since the intrinsic can be skipped I marked Class.cast() as force_inline 
method to make sure it is inlined to propagate checkcast information in 
compiled code.

An additional improvement could be made to type checks in intrinsics if 
we use speculative types. I filed RFE:
https://bugs.openjdk.java.net/browse/JDK-8062477

I added new regression test and added compile_id to WB nmethod information.

Tested jtreg hotspot and jtreg j/l/invoke from jdk, CTW, JPRT, performance.

Nashorn's Octane-Box2D and Octane-DeltaBlue shows few percents improvement.

Thanks,
Vladimir

On 10/24/14 2:57 PM, Vladimir Kozlov wrote:
> On 10/23/14 3:45 AM, Paul Sandoz wrote:
>> Hi Vladimir,
>>
>> Do you consider these two aspects (intrinsic and inline) closely
>> interrelated do as to be considered under the same issue? If not i can
>> log another issue for the inlining.
>
> I am working on next version of my intrinsic after discussion with John
> Rose. It will use gen_checkcast() code which we use for checkcast
> bytecode. It will be more general code and less dependable on inlining.
> But I still want to do force inlining Call.cast() in more general case
> when we can still use profiling data.
>
> I am concern about changes in castReference() to use Class.cast(). It
> will need additional performance testing because it was big performance
> bottleneck for jsr292. And I don't want to cause regression.
>
> Thanks,
> Vladimir
>
>>
>> Paul.
>>
>> On Oct 23, 2014, at 7:09 AM, Vladimir Kozlov
>> <vladimir.kozlov at oracle.com> wrote:
>>
>>> On 10/22/14 2:29 AM, Paul Sandoz wrote:
>>>> On Oct 22, 2014, at 10:54 AM, Roland Westrelin
>>>> <roland.westrelin at oracle.com> wrote:
>>>>>> Here is intrinsic implementation:
>>>>>>
>>>>>> http://cr.openjdk.java.net/~kvn/8054492/webrev.01/
>>>>>
>>>>> That looks good to me.
>>>>>
>>>> Same here.
>>>>
>>>> On Oct 22, 2014, at 2:02 AM, Vladimir Kozlov
>>>> <vladimir.kozlov at oracle.com> wrote:
>>>>> Paul, is it enough for you?
>>>>>
>>>>
>>>> Yes, many thanks. I verified in a number of scenarios.
>>>>
>>>> With Class.cast intrinsified can we can replace uses of following
>>>> method in j.l.i.MethodHandleImpl with Class.cast?
>>>
>>> Intrinsic is not enough. That code was added because we do not inline
>>> Class.cast() for deep call stacks. C2 has inline depth limit 9. But
>>> we can workaround using next changes:
>>>
>>> --- a/src/share/vm/opto/bytecodeInfo.cpp    Fri Aug 22 09:55:49 2014
>>> -0700
>>> +++ b/src/share/vm/opto/bytecodeInfo.cpp    Wed Oct 22 22:07:21 2014
>>> -0700
>>> @@ -161,6 +161,7 @@
>>>    if ((freq >= InlineFrequencyRatio) ||
>>>        (call_site_count >= InlineFrequencyCount) ||
>>>        is_unboxing_method(callee_method, C) ||
>>> +      (callee_method->intrinsic_id() == vmIntrinsics::_class_cast) ||
>>>        is_init_with_ea(callee_method, caller_method, C)) {
>>>
>>>      max_inline_size = C->freq_inline_size();
>>> @@ -262,6 +263,11 @@
>>>      return false;
>>>    }
>>>
>>> +  if (callee_method->intrinsic_id() == vmIntrinsics::_class_cast) {
>>> +    // Inline Class.cast() method.
>>> +    return false;
>>> +  }
>>> +
>>>    if (callee_method->has_compiled_code() &&
>>>        callee_method->instructions_size() > InlineSmallCode) {
>>>      set_msg("already compiled into a big method");
>>>
>>>
>>> Thanks,
>>> Vladimir
>>>
>>>>
>>>>      @ForceInline
>>>>      @SuppressWarnings("unchecked")
>>>>      static <T,U> T castReference(Class<? extends T> t, U x) {
>>>>          // inlined Class.cast because we can't ForceInline it
>>>>          if (x != null && !t.isInstance(x))
>>>>              throw newClassCastException(t, x);
>>>>          return (T) x;
>>>>      }
>>>>
>>>> Paul.
>>>>
>>