RFR: 8307907: [ppc] Remove RTM locking implementation [v2]

[Richard Reingruber]

On Fri, 9 Jun 2023 18:25:30 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

>> This PR removes RTM code for PPC64. The instructions are not supported by Power10 processors.
>> The situation is even worse in Power9 compatibility mode on Power10. The VM detects RTM to be available, but the processor is unable to complete any transaction successfully.
>> The feature had so many problems and we never supported it in production.
>
> Martin Doerr has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Remove RTM from feature string. Otherwise, tests complain about it.

Looks good (except 2 nits). I'm glad we get rid of this complex code. Thanks!

src/hotspot/cpu/ppc/macroAssembler_ppc.cpp line 2648:

> 2646: 
> 2647: #if INCLUDE_RTM_OPT
> 2648:   if (UseRTMForStackLocks && use_rtm) {

Can RTM related method parameters (e.g. `use_rtm`) be removed?

src/hotspot/cpu/ppc/macroAssembler_ppc.cpp line 2773:

> 2771: 
> 2772: #if INCLUDE_RTM_OPT
> 2773:   if (UseRTMForStackLocks && use_rtm) {

Can RTM related method parameters (e.g. `use_rtm`) be removed?

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PR Review: https://git.openjdk.org/jdk/pull/14398#pullrequestreview-1479472940
PR Review Comment: https://git.openjdk.org/jdk/pull/14398#discussion_r1229636539
PR Review Comment: https://git.openjdk.org/jdk/pull/14398#discussion_r1229640506