RFR: 8367325: [s390x] build failure due to JDK-8361376 [v4]

[Amit Kumar]

On Thu, 18 Sep 2025 10:25:34 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

>> Amit Kumar has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   refactor
>
> src/hotspot/cpu/s390/gc/shared/barrierSetAssembler_s390.cpp line 174:
> 
>> 172: void BarrierSetAssembler::nmethod_entry_barrier(MacroAssembler* masm) {
>> 173:   BarrierSetNMethod* bs_nm = BarrierSet::barrier_set()->barrier_set_nmethod();
>> 174:   __ align(4, __ offset() + BARRIER_TOTAL_LENGTH); // must align the following block which requires atomic updates
> 
> Now, this is confusing. We don't want to align the end of the barrier. We need to align the patchable field which is the immediate field of the cfi instruction.

I couldn't find out better way to keep the main code free from magic numbers, so now there are three constants:
1. holding offset to the instruction (cfi) 
2. holding the offset the the patchable data 
3. total barrier length. 

I guess explanation in .hpp is enough to explain the usecase.

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PR Review Comment: https://git.openjdk.org/jdk/pull/27213#discussion_r2358878758