[9] RFR (M): 8037209: Improvements and cleanups to bytecode assembly for lambda forms

[Vladimir Ivanov]

Updated version:
http://cr.openjdk.java.net/~vlivanov/8037209/webrev.01/

Changes:
   - rebased to enum-based BasicType;
   - decided to integrate changes for typed array getters/setters 
separately;

Best regards,
Vladimir Ivanov

On 3/14/14 8:36 PM, Vladimir Ivanov wrote:
>> Doh! crossed webrevs, thanks.
>>
>> Just had a quick look, this looks like a really nice improvement to
>> the array setter/getter support, definitely simplified. IIUC the
>> mh.viewAsType will now handle the appropriate casting. I believe it
>> might reduce the "ceremony" for array setter/getter MHs [1].
>>
>> I see there is a PROFILE_LEVEL option, by default set to 0, that
>> results in casts not being emitted:
>>
>> +                if (VerifyType.isNullConversion(Object.class, pclass,
>> false)) {
>> +                    if (PROFILE_LEVEL > 0)
>> +                        emitReferenceCast(Object.class, arg);
>> +                    return;
>> +                }
>> ...
>> +            mv.visitLdcInsn(constantPlaceholder(cls));
>> +            mv.visitTypeInsn(Opcodes.CHECKCAST, CLS);
>> +            mv.visitInsn(Opcodes.SWAP);
>> +            mv.visitMethodInsn(Opcodes.INVOKESTATIC, MHI,
>> "castReference", CLL_SIG, false);
>> +            if (Object[].class.isAssignableFrom(cls))
>> +                mv.visitTypeInsn(Opcodes.CHECKCAST, OBJARY);
>> +            else if (PROFILE_LEVEL > 0)
>> +                mv.visitTypeInsn(Opcodes.CHECKCAST, OBJ);
>>
>> Can you explain a bit the rational for that?
> These casts are redundant - they aren't required for bytecode
> correctness. The idea behind PROFILE_LEVEL is to provide more type
> information to JIT-compiler. Right now, type profiling occurs on every
> checkcast instruction. So, having these additional instructions we can
> feed C2 with more accurate information about types.
>
> Consider this as a hack to overcome some of the limitations of current
> profiling implementation in VM.
>
> Best regards,
> Vladimir Ivanov
>
>> Paul.
>>
>> [1] Below is an inlining trace for an array getter MH in the current
>> code i obtained a few weeks ago when investigating CAS-based MHs for
>> arrays:
>>
>> Inlining _isInstance on constant Class java/lang/Class
>> Inlining _isInstance on constant Class [Ljava/lang/Object;
>> Inlining _isInstance on constant Class [Ljava/lang/String;
>> Inlining _isInstance on constant Class java/lang/String
>>                              @ 12   unsafe.ArrayMHTest::get_mh_orig
>> (19 bytes)   inline (hot)
>>                                @ 12
>> java.lang.invoke.LambdaForm$MH/924874137::invokeExact_MT (15 bytes)
>> inline (hot)
>>                                  @ 2
>> java.lang.invoke.Invokers::checkExactType (30 bytes)   inline (hot)
>>                                    @ 11
>> java.lang.invoke.MethodHandle::type (5 bytes)   accessor
>>                                  @ 11
>> java.lang.invoke.LambdaForm$MH/1980556943::convert (21 bytes)   inline
>> (hot)
>>                                    @ 7
>> java.lang.invoke.LambdaForm$MH/1892887290::getElement (20 bytes)
>> inline (hot)
>>                                      @ 16
>> java.lang.invoke.LambdaForm$MH/816943783::convert (37 bytes)   inline
>> (hot)
>>                                        @ 6
>> java.lang.invoke.LambdaForm$BMH/1350345087::reinvoke (26 bytes)
>> inline (hot)
>>                                          @ 12
>> java.lang.invoke.BoundMethodHandle$Species_LL::reinvokerTarget (8
>> bytes)   inline (hot)
>>                                          @ 22
>> java.lang.invoke.LambdaForm$DMH/1162873666::invokeStatic_LL_L (15
>> bytes)   inline (hot)
>>                                            @ 1
>> java.lang.invoke.DirectMethodHandle::internalMemberName (8 bytes)
>> inline (hot)
>>                                            @ 11
>> sun.invoke.util.ValueConversions::castReference (20 bytes)   inline (hot)
>>                                              @ 6
>> java.lang.Class::isInstance (0 bytes)   (intrinsic)
>>                                        @ 17
>> java.lang.invoke.LambdaForm$BMH/1350345087::reinvoke (26 bytes)
>> inline (hot)
>>                                          @ 12
>> java.lang.invoke.BoundMethodHandle$Species_LL::reinvokerTarget (8
>> bytes)   inline (hot)
>>                                          @ 22
>> java.lang.invoke.LambdaForm$DMH/1162873666::invokeStatic_LL_L (15
>> bytes)   inline (hot)
>>                                            @ 1
>> java.lang.invoke.DirectMethodHandle::internalMemberName (8 bytes)
>> inline (hot)
>>                                            @ 11
>> sun.invoke.util.ValueConversions::castReference (20 bytes)   inline (hot)
>>                                              @ 6
>> java.lang.Class::isInstance (0 bytes)   (intrinsic)
>>                                        @ 33
>> java.lang.invoke.MethodHandleImpl$ArrayAccessor::getElementL (10
>> bytes)   inline (hot)
>>                                          @ 2   java.lang.Class::cast
>> (27 bytes)   inline (hot)
>>                                            @ 6
>> java.lang.Class::isInstance (0 bytes)   (intrinsic)
>>                                    @ 17
>> java.lang.invoke.LambdaForm$MH/91466391::convert (23 bytes)   inline
>> (hot)
>>                                      @ 6
>> java.lang.invoke.LambdaForm$BMH/1350345087::reinvoke (26 bytes)
>> inline (hot)
>>                                        @ 12
>> java.lang.invoke.BoundMethodHandle$Species_LL::reinvokerTarget (8
>> bytes)   inline (hot)
>>                                        @ 22
>> java.lang.invoke.LambdaForm$DMH/1162873666::invokeStatic_LL_L (15
>> bytes)   inline (hot)
>>                                          @ 1
>> java.lang.invoke.DirectMethodHandle::internalMemberName (8 bytes)
>> inline (hot)
>>                                          @ 11
>> sun.invoke.util.ValueConversions::castReference (20 bytes)   inline (hot)
>>                                            @ 6
>> java.lang.Class::isInstance (0 bytes)   (intrinsic)
>>                                      @ 19
>> java.lang.invoke.LambdaForm$MH/349834280::identity (10 bytes)   inline
>> (hot)
>>                                        @ 6
>> java.lang.invoke.LambdaForm$DMH/1357006072::invokeStatic_L_L (14
>> bytes)   inline (hot)
>>                                          @ 1
>> java.lang.invoke.DirectMethodHandle::internalMemberName (8 bytes)
>> inline (hot)
>>                                          @ 10
>> sun.invoke.util.ValueConversions::identity (2 bytes)   inline (hot)
>>