RFR: JDK-8299229: [JVMCI] add support for UseZGC [v6]

[Tom Rodriguez]

On Wed, 3 May 2023 03:44:12 GMT, Fei Yang <fyang at openjdk.org> wrote:

>> Tom Rodriguez has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 14 commits:
>> 
>>  - Fix handling of extra data
>>  - Merge branch 'master' into tkr-zgc
>>  - Require nmethod entry barrier emission
>>  - Merge branch 'master' into tkr-zgc
>>  - Use reloc for guard location and read internal fields using HotSpot accessors
>>  - Merge branch 'master' into tkr-zgc
>>  - Remove access to extra data section from Java code
>>  - Handle concurrent unloading
>>  - Merge branch 'master' into tkr-zgc
>>  - Add missing declaration
>>  - ... and 4 more: https://git.openjdk.org/jdk/compare/f00a748b...ce19812e
>
> src/hotspot/cpu/riscv/gc/shared/barrierSetNMethod_riscv.cpp line 85:
> 
>> 83:     if (nm->is_compiled_by_jvmci()) {
>> 84:       _instruction_address = nm->code_begin() + nm->frame_complete_offset();
>> 85:       _guard_addr = reinterpret_cast<int*>(nm->consts_begin() + nm->jvmci_nmethod_data()->nmethod_entry_patch_offset());
> 
> I see 'nm->consts_begin()' is used here to calculate '_guard_addr' for the JVMCI case on riscv. Do you have more details about the design? Thanks.

I forgot to update the riscv version since Graal isn't actually fully working there.  It should look just like the aarch64 code in this regard as the same strategy should work there too.

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PR Review Comment: https://git.openjdk.org/jdk/pull/11996#discussion_r1183967703