[External] : Re: 8230015: [instruction selector] generic vector operands support.

[Vladimir Ivanov]

>> It should be enough to provide implementations for those methods on 
>> YOURARCH to make Matcher::do_postselect_cleanup() working.
> 
> It is my fault: other VectorNodes, for example, `MulVD` and `ReplicateD` 
> also need to change `vecX/Y` to `vec` in the very beginning, not only 
> just LoadVector/StoreVector.  Sorry that I am too hurry to see the 
> optimization effect.

Yes, the downside is that there's no implicit operand conversion 
supported between concrete and generic vector operands. You have to 
migrate everything at once.

Best regards,
Vladimir Ivanov

>>
>> Can you elaborate on what exactly you are trying to accomplish?
> 
> Better SPECjvm2008 benchmark performance and meanwhile libjvm.so keep 
> slim :)
> 
> Thanks,
> Leslie Zhai
> 
>>
>>
>> Best regards,
>> Vladimir Ivanov
>>
>> On 14.04.2021 08:09, Leslie Zhai wrote:
>>> Hi Jatin,
>>>
>>> Thanks for your great work!
>>>
>>> libjvm.so reduced +1MB will help SPECjvm2008 some benchmark +44% 
>>> speed up.
>>>
>>> Then I tried to port 8234391: C2: Generic vector operands for 
>>> `YOURARCH` about LoadVector and StoreVector at first.
>>>
>>> Only `Matcher::regmask_for_ideal_register` was able to call 
>>> `Matcher::is_generic_vector`, but compared with X86, 
>>> `Matcher::do_postselect_cleanup` was also able to call 
>>> `Matcher::is_generic_vector` too.
>>>
>>> I debug the `Matcher::do_postselect_cleanup`:
>>>
>>> diff --git a/src/hotspot/share/opto/matcher.cpp 
>>> b/src/hotspot/share/opto/matcher.cpp
>>> index 0846cad3c3f..8fd644d2d93 100644
>>> --- a/src/hotspot/share/opto/matcher.cpp
>>> +++ b/src/hotspot/share/opto/matcher.cpp
>>> @@ -309,6 +309,9 @@ void Matcher::match( ) {
>>>      C->record_method_not_compilable("must be able to represent all 
>>> call arguments in reg mask");
>>>    }
>>>
>>> +#ifdef YOURARCH64
>>> +  do_postselect_cleanup();
>>> +#endif
>>>    if (C->failing())  return;  // bailed out on incoming arg failure
>>>
>>>    // ---------------
>>> @@ -2630,8 +2633,10 @@ void 
>>> Matcher::specialize_generic_vector_operands() {
>>>          int opnd_idx = m->operand_index(1);
>>>          Node* def = m->in(opnd_idx);
>>>          m->subsume_by(def, C);
>>> +#if !defined(YOURARCH64)
>>>        } else if (m->is_MachTemp()) {
>>>          // process MachTemp nodes at use site (see 
>>> Matcher::specialize_vector_operand)
>>> +#endif
>>>        } else {
>>>          specialize_mach_node(m);
>>>        }
>>>
>>> But `Matcher::do_postselect_cleanup` was still not able to be called.
>>>
>>>> Current patch enables this support only for x86 target, to get a 
>>> feedback from community.
>>>
>>> Then how to port Generic vector operands for other targets?
>>>
>>> Thanks,
>>>
>>> Leslie Zhai
>>>
>>>
>>> 在 2019年08月22日 14:49, Bhateja, Jatin 写道:
>>>> Hi All,
>>>>
>>>> Please find below a patch for generic vector operands[1] support 
>>>> during instruction selection.
>>>>
>>>> Motivation behind the patch is to reduce the number of vector 
>>>> selection patterns whose operands meagerly differ in vector lengths.
>>>> This will not only result in lesser code being generated by ADLC 
>>>> which effectively translates to size reduction in libjvm.so but also
>>>> help in better maintenance of AD files.
>>>>
>>>> Using generic operands we were able to collapse multiple vector 
>>>> patterns over mainline
>>>>               Initial number of vector instruction patterns 
>>>> (vec[XYZSD] + legVec[ZXYSD]   :  510
>>>>               Reduced vector instruction patterns  (vecG + 
>>>> legVecG)                                  :  222
>>>>
>>>> With this we could see around 1MB size reduction in libjvm.so.
>>>>
>>>> In order to have minimal impact over downstream compiler passes, a 
>>>> post-selection pass has been introduced (currently enabled only for 
>>>> X86 target)
>>>> which replaces these generic operands with their corresponding 
>>>> concreter vector length variants.
>>>>
>>>> JBS      : https://bugs.openjdk.java.net/browse/JDK-8230015
>>>> Patch  : 
>>>> http://cr.openjdk.java.net/~jbhateja/genericVectorOperands/webrev.00/
>>>>
>>>> Kindly review and share your feedback.
>>>>
>>>> Best Regards,
>>>> Jatin Bhateja
>>>>
>>>> [1] 
>>>> http://cr.openjdk.java.net/~jbhateja/genericVectorOperands/generic_operands_support_v1.0.pdf 
>>>>
>>>>
>>>
>