RFR(M) JDK-8181809 PPC64: Leverage mtfprd/mffprd on POWER8

[Doerr, Martin]

Excellent. Thanks for the update. The C1 part looks good, too.

Also, thanks for checking "I could not find evidence of any config that includes vpmsumb but not 
mtfprd."

There are only a few formally required things:
- The new C1 code contains Tab characters. It's not possible to push it without fixing this.
- Copyright messages should be updated.
- Minor resolution to get vm_version_ppc applied to recent jdk10/hs.

If no other changes get requested, I can handle these issues this time before pushing.
But we need another review, first.

Thanks and best regards,
Martin


-----Original Message-----
From: Matthew Brandyberry [mailto:mbrandy at linux.vnet.ibm.com] 
Sent: Freitag, 23. Juni 2017 04:54
To: Doerr, Martin <martin.doerr at sap.com>; ppc-aix-port-dev at openjdk.java.net; hotspot-dev at openjdk.java.net
Subject: Re: RFR(M) JDK-8181809 PPC64: Leverage mtfprd/mffprd on POWER8

Updated webrev: http://cr.openjdk.java.net/~gromero/8181809/v2/

See below for responses inline.

On 6/20/17 8:38 AM, Matthew Brandyberry wrote:
> Hi Martin,
>
> Thanks for the review.  I'll take a look at these areas and report 
> back -- especially the integration into C1.
>
> On 6/20/17 8:33 AM, Doerr, Martin wrote:
>> Hi Matt,
>>
>> thanks for providing this webrev. I had already thought about using 
>> these instructions for this purpose and your change matches pretty 
>> much what I'd do.
>>
>> Here a couple of comments:
>> ppc.ad:
>> This was a lot of work. Thanks for doing it.
>> effect(DEF dst, USE src); is redundant if a match rule match(Set dst 
>> (MoveL2D src)); exists.
Fixed.
>>
>> vm_version:
>> This part is in conflict with Michihiro's change which is already 
>> pushed in jdk10, but it's trivial to resolve. I'm ok with using 
>> has_vpmsumb() for has_mtfprd(). In the past, we sometimes had trouble 
>> with assuming that a certain Power processor supports all new 
>> instructions if it supports certain ones. We also use the hotspot 
>> code on as400 where certain instruction subsets were disabled while 
>> other Power 8 instructions were usable. Maybe you can double-check if 
>> there may exist configurations in which has_vpmsumb() doesn't match 
>> has_mtfprd().
I could not find evidence of any config that includes vpmsumb but not 
mtfprd.
>>
>> C1:
>> It should also be possible to use the instructions in C1 compiler. 
>> Maybe you would like to take a look at it as well and see if it can 
>> be done with feasible effort.
>> Here are some hints:
>> The basic decisions are made in LIRGenerator::do_Convert. You could 
>> skip the force_to_spill or must_start_in_memory steps.
>> The final assembly code gets emitted in LIR_Assembler::emit_opConvert 
>> where you could replace the store instructions.
>> For testing, you can use -XX:TieredStopAtLevel=1, for example.
Done.  Please take a look.
>>
>> Thanks and best regards,
>> Martin
>>
>>
>> -----Original Message-----
>> From: hotspot-dev [mailto:hotspot-dev-bounces at openjdk.java.net] On 
>> Behalf Of Matthew Brandyberry
>> Sent: Montag, 19. Juni 2017 18:28
>> To: ppc-aix-port-dev at openjdk.java.net; hotspot-dev at openjdk.java.net
>> Subject: RFR(M) JDK-8181809 PPC64: Leverage mtfprd/mffprd on POWER8
>>
>> This is a PPC-specific hotspot optimization that leverages the
>> mtfprd/mffprd instructions for for movement between general purpose and
>> floating point registers (rather than through memory).  It yields a ~35%
>> improvement measured via a microbenchmark. Please review: Bug:
>> https://bugs.openjdk.java.net/browse/JDK-8181809 Webrev:
>> http://cr.openjdk.java.net/~gromero/8181809/v1/ Thanks, Matt
>>
>>
>