RFR: 8325467: Support methods with many arguments in C2 [v27]

[Daniel Lundén]

On Tue, 16 Sep 2025 12:01:22 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 39 commits:
>> 
>>  - Clarify comments in regmask.hpp
>>  - Merge remote-tracking branch 'upstream/master' into many-arguments-8325467+pr-updates
>>  - Address review comments (renaming on the way in a separate PR)
>>  - Update src/hotspot/share/opto/regmask.hpp
>>    
>>    Co-authored-by: Emanuel Peter <emanuel.peter at oracle.com>
>>  - 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
>>  - ... and 29 more: https://git.openjdk.org/jdk/compare/60930a3e...c1f41288
>
> src/hotspot/share/opto/regmask.hpp line 241:
> 
>> 239:   //          \_______________________________________________________________________________/
>> 240:   //                                                  |
>> 241:   //                                  _rm_size_in_words=_offset=5
> 
> Can you please add some concise comment why we need `rollover`? Does that happen during register allocation, and if we have rollover then we start spilling instead of keeping values in registers?

I'll update the comment above the definition of `_offset` (which I'll move just above this) to hopefully make this clearer.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20404#discussion_r2354855077