RFR: 8339983: [s390x] secondary_super_cache does not scale well: C1 and interpreter [v2]

[Amit Kumar]

On Wed, 27 Nov 2024 11:08:18 GMT, Amit Kumar <amitkumar at openjdk.org> wrote:

>>> There is a significant (and varying) distance between here and where the CC is evaluated. I would expect at least a comment that the code in between must not alter the CC.
>> 
>> I'd just move the comparison nearer the conditional branch.
>
>>I'd just move the comparison nearer the conditional branch. 
> 
> result_reg could be `noreg`. So it will be popped out and we might loose the content. One such call is at `3245`:
> 
>   if (UseSecondarySupersTable) {
>     check_klass_subtype_slow_path_table(sub_klass,
>                                         super_klass,
>                                         temp_reg,
>                                         temp2_reg,
>                                         /*temp3*/noreg,
>                                         /*temp4*/noreg,
>                                         /*result*/noreg,
>                                         L_success,
>                                         L_failure,
>                                         set_cond_codes);
> 
> 
> But we can store the value in scratch register, maybe `Z_R0` and then move this check.

Also, between this instruction and the branch instruction, we are emitting `z_lg` and `z_lghi` instruction. So maybe just put a comment ?

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PR Review Comment: https://git.openjdk.org/jdk/pull/22341#discussion_r1860478551