RFR: 8307907: [ppc] Remove RTM locking implementation [v3]

[Thomas Stuefe]

On Wed, 14 Jun 2023 14:31:41 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 more leftovers from RTM.

You also can probably remove `transaction_failure_reason` from assembler_ppc.hpp

src/hotspot/cpu/ppc/vm_version_ppc.cpp line 1:

> 1: /*

I think you can remove PPC_FEATURE2_HTM_NOSC too, right?

test/hotspot/jtreg/compiler/rtm/cli/TestUseRTMLockingOptionOnUnsupportedCPU.java line 65:

> 63:                         ExitCode.FAIL, "-XX:+UseRTMLocking");
> 64:             } catch (Throwable e) {
> 65:                 throw e; // checking unsupported OS error is not necessary

Why even catch this now?

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PR Review: https://git.openjdk.org/jdk/pull/14398#pullrequestreview-1480110350
PR Review Comment: https://git.openjdk.org/jdk/pull/14398#discussion_r1230046819
PR Review Comment: https://git.openjdk.org/jdk/pull/14398#discussion_r1230042445