RFR: 8349686: [s390x] C1: Improve Class.isInstance intrinsic [v10]

[Lutz Schmidt]

On Tue, 25 Feb 2025 15:39:21 GMT, Amit Kumar <amitkumar at openjdk.org> wrote:

>> s390x implementation for Class.isInstance intrinsic. 
>> 
>> Tier1 test on release & fastdebug vm are clean with flag: `-XX:-UseSecondarySupersCache -XX:+UseSecondarySupersTable -XX:+VerifySecondarySupers -XX:+StressSecondarySupers`. 
>> 
>> Benchmark results will be updated soon.
>
> Amit Kumar has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Update src/hotspot/cpu/s390/c1_Runtime1_s390.cpp
>   
>   Co-authored-by: Andrew Haley <aph-open at littlepinkcloud.com>

There is one minor add'l improvement, if you like. Does not block integration.
Looks good otherwise.

src/hotspot/cpu/s390/c1_Runtime1_s390.cpp line 603:

> 601:       Register temp0 = Z_ARG4, temp1 = Z_ARG5, temp2 = Z_R10, temp3 = Z_R11;
> 602: 
> 603:       __ z_lg(klass, Address(Z_ARG1, java_lang_Class::klass_offset()));

You could combine this with the LTGR below into a LTG. The clear_reg() call will preserve CC.

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Marked as reviewed by lucy (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/23535#pullrequestreview-2697552814
PR Review Comment: https://git.openjdk.org/jdk/pull/23535#discussion_r2002823312