RFR: 8338995: New Object to ObjectMonitor mapping: PPC64 implementation [v3]

[Richard Reingruber]

On Fri, 13 Sep 2024 18:32:41 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

>> PPC64 implementation of [JDK-8315884](https://bugs.openjdk.org/browse/JDK-8315884).
>
> Martin Doerr has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Remove empty line.
>  - Improve register usage and readability.

Hi Martin,

thanks for doing the port.
Have you done a little bit of performance testing with `test/micro/org/openjdk/bench/vm/lang/LockUnlock.java`?

Thanks, Richard.

src/hotspot/cpu/ppc/macroAssembler_ppc.cpp line 2825:

> 2823:       for (int i = 0; i < num_unrolled; i++) {
> 2824:         ld(tmp3, 0, cache_addr);
> 2825:         cmpd(CCR0, tmp3, obj);

Please file a RFE to consistently use either `flag` or `CCR0`.

src/hotspot/cpu/ppc/macroAssembler_ppc.cpp line 2878:

> 2876:       ld(tmp2, in_bytes(ObjectMonitor::recursions_offset()), monitor);
> 2877:       addi(tmp2, tmp2, 1);
> 2878:       std(tmp2, in_bytes(ObjectMonitor::recursions_offset()), monitor);

Can you replace the if-statement with the following?

Suggestion:

      assert_different_registers(tmp2, monitor);
      int offset = in_bytes(ObjectMonitor::recursions_offset()) - (UseObjectMonitorTable ? 0 : monitor_tag);
      ld(tmp2, offset, monitor);
      addi(tmp2, tmp2, 1);
      std(tmp2, offset, monitor);

src/hotspot/cpu/ppc/macroAssembler_ppc.cpp line 3013:

> 3011:       // null check with Flags == NE, no valid pointer below alignof(ObjectMonitor*)
> 3012:       cmpldi(CCR0, monitor, checked_cast<uint8_t>(alignof(ObjectMonitor*)));
> 3013:       blt(CCR0, slow_path);

Please file a RFE to consistently use either `flag` or `CCR0`.

-------------

PR Review: https://git.openjdk.org/jdk/pull/20922#pullrequestreview-2310141350
PR Review Comment: https://git.openjdk.org/jdk/pull/20922#discussion_r1763476209
PR Review Comment: https://git.openjdk.org/jdk/pull/20922#discussion_r1764762441
PR Review Comment: https://git.openjdk.org/jdk/pull/20922#discussion_r1764719435