RFR: 8325467: Support methods with many arguments in C2 [v24]

[Daniel Lundén]

On Mon, 1 Sep 2025 08:30:19 GMT, Emanuel Peter <epeter at openjdk.org> wrote:

>> Daniel Lundén has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 35 commits:
>> 
>>  - Restore modified java/lang/invoke tests
>>  - Sort includes (new requirement)
>>  - Merge remote-tracking branch 'upstream/master' into many-arguments-8325467+pr-updates
>>  - Add clarifying comments at definitions of register mask sizes
>>  - Fix implicit zero and nullptr checks
>>  - Add deep copy comment
>>  - Merge remote-tracking branch 'upstream/master' into many-arguments-8325467+pr-updates
>>  - Fix typo
>>  - Updates after Emanuel's comments
>>  - Refactor and improve TestNestedSynchronize.java
>>  - ... and 25 more: https://git.openjdk.org/jdk/compare/b39c7369...80c6cf47
>
> src/hotspot/share/opto/regmask.hpp line 170:
> 
>> 168:   // variable indicates how many words we offset with. We consider all
>> 169:   // registers before the offset to not be included in the register mask.
>> 170:   unsigned int _offset;
> 
> Does that mean we make different slices of the mask?

I don't quite understand the question, can you please elaborate? The `_offset` means we shift the register mask to the right, so that the first bit of the first `_RM_UP` element no longer represents `OptoReg` 0 (but rather `OptoReg` `_offset * BitsPerWord`).

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PR Review Comment: https://git.openjdk.org/jdk/pull/20404#discussion_r2314325238