RFR: 8331126: [s390x] secondary_super_cache does not scale well [v6]

[Amit Kumar]

On Sun, 30 Jun 2024 09:42:52 GMT, Andrew Haley <aph at openjdk.org> wrote:

>> Amit Kumar has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   add2reg -> z_la
>
> src/hotspot/cpu/s390/macroAssembler_s390.cpp line 3243:
> 
>> 3241:   // Get the first array index that can contain super_klass.
>> 3242:   if (bit != 0) {
>> 3243:     pop_count_long(r_array_index, r_array_index, Z_R1_scratch); // all the registers are hardcoded so should be fine
> 
> This comment is also rather baffling. You seem to be concerned about something, but what? `pop_count_long` doesn't cause any particular risk, does it?

For machines older than `Z15`, `pop_count_long` clobbers `Z_R1_scratch` register.  That's why I added it there.

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PR Review Comment: https://git.openjdk.org/jdk/pull/19544#discussion_r1660203297